Change tcpip.Error to an interface

This makes it possible to add data to types that implement tcpip.Error.
ErrBadLinkEndpoint is removed as it is unused.

PiperOrigin-RevId: 354437314

105 files changed, 2246 insertions, 1713 deletions

diff --git a/pkg/tcpip/BUILD b/pkg/tcpip/BUILD
index e7924e5c2..f979d22f0 100644
--- a/pkg/tcpip/BUILD
+++ b/pkg/tcpip/BUILD
@@ -18,6 +18,7 @@ go_template_instance(
 go_library(
     name = "tcpip",
     srcs = [
+        "errors.go",
         "sock_err_list.go",
         "socketops.go",
         "tcpip.go",
diff --git a/pkg/tcpip/adapters/gonet/gonet.go b/pkg/tcpip/adapters/gonet/gonet.go
index 7c7495c30..c188aaa18 100644
--- a/pkg/tcpip/adapters/gonet/gonet.go
+++ b/pkg/tcpip/adapters/gonet/gonet.go
@@ -248,7 +248,7 @@ func NewTCPConn(wq *waiter.Queue, ep tcpip.Endpoint) *TCPConn {
 func (l *TCPListener) Accept() (net.Conn, error) {
 	n, wq, err := l.ep.Accept(nil)
 
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
 		l.wq.EventRegister(&waitEntry, waiter.EventIn)
@@ -257,7 +257,7 @@ func (l *TCPListener) Accept() (net.Conn, error) {
 		for {
 			n, wq, err = l.ep.Accept(nil)
 
-			if err != tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 				break
 			}
 
@@ -298,14 +298,14 @@ func commonRead(b []byte, ep tcpip.Endpoint, wq *waiter.Queue, deadline <-chan s
 	opts := tcpip.ReadOptions{NeedRemoteAddr: addr != nil}
 	res, err := ep.Read(&w, opts)
 
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
 		wq.EventRegister(&waitEntry, waiter.EventIn)
 		defer wq.EventUnregister(&waitEntry)
 		for {
 			res, err = ep.Read(&w, opts)
-			if err != tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 				break
 			}
 			select {
@@ -316,7 +316,7 @@ func commonRead(b []byte, ep tcpip.Endpoint, wq *waiter.Queue, deadline <-chan s
 		}
 	}
 
-	if err == tcpip.ErrClosedForReceive {
+	if _, ok := err.(*tcpip.ErrClosedForReceive); ok {
 		return 0, io.EOF
 	}
 
@@ -356,7 +356,7 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 	}
 
 	// We must handle two soft failure conditions simultaneously:
-	//  1. Write may write nothing and return tcpip.ErrWouldBlock.
+	//  1. Write may write nothing and return *tcpip.ErrWouldBlock.
 	//     If this happens, we need to register for notifications if we have
 	//     not already and wait to try again.
 	//  2. Write may write fewer than the full number of bytes and return
@@ -376,9 +376,9 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 		r.Reset(b[nbytes:])
 		n, err := c.ep.Write(&r, tcpip.WriteOptions{})
 		nbytes += int(n)
-		switch err {
+		switch err.(type) {
 		case nil:
-		case tcpip.ErrWouldBlock:
+		case *tcpip.ErrWouldBlock:
 			if ch == nil {
 				entry, ch = waiter.NewChannelEntry(nil)
 
@@ -495,7 +495,7 @@ func DialContextTCP(ctx context.Context, s *stack.Stack, addr tcpip.FullAddress,
 	}
 
 	err = ep.Connect(addr)
-	if err == tcpip.ErrConnectStarted {
+	if _, ok := err.(*tcpip.ErrConnectStarted); ok {
 		select {
 		case <-ctx.Done():
 			ep.Close()
@@ -649,7 +649,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 	var r bytes.Reader
 	r.Reset(b)
 	n, err := c.ep.Write(&r, writeOptions)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
 		c.wq.EventRegister(&waitEntry, waiter.EventOut)
@@ -662,7 +662,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 			}
 
 			n, err = c.ep.Write(&r, writeOptions)
-			if err != tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 				break
 			}
 		}
diff --git a/pkg/tcpip/adapters/gonet/gonet_test.go b/pkg/tcpip/adapters/gonet/gonet_test.go
index b196324c7..2b3ea4bdf 100644
--- a/pkg/tcpip/adapters/gonet/gonet_test.go
+++ b/pkg/tcpip/adapters/gonet/gonet_test.go
@@ -58,7 +58,7 @@ func TestTimeouts(t *testing.T) {
 	}
 }
 
-func newLoopbackStack() (*stack.Stack, *tcpip.Error) {
+func newLoopbackStack() (*stack.Stack, tcpip.Error) {
 	// Create the stack and add a NIC.
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{ipv4.NewProtocol, ipv6.NewProtocol},
@@ -94,7 +94,7 @@ type testConnection struct {
 	ep tcpip.Endpoint
 }
 
-func connect(s *stack.Stack, addr tcpip.FullAddress) (*testConnection, *tcpip.Error) {
+func connect(s *stack.Stack, addr tcpip.FullAddress) (*testConnection, tcpip.Error) {
 	wq := &waiter.Queue{}
 	ep, err := s.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, wq)
 	if err != nil {
@@ -105,7 +105,7 @@ func connect(s *stack.Stack, addr tcpip.FullAddress) (*testConnection, *tcpip.Er
 	wq.EventRegister(&entry, waiter.EventOut)
 
 	err = ep.Connect(addr)
-	if err == tcpip.ErrConnectStarted {
+	if _, ok := err.(*tcpip.ErrConnectStarted); ok {
 		<-ch
 		err = ep.LastError()
 	}
@@ -660,11 +660,13 @@ func TestTCPDialError(t *testing.T) {
 	ip := tcpip.Address(net.IPv4(169, 254, 10, 1).To4())
 	addr := tcpip.FullAddress{NICID, ip, 11211}
 
-	_, err := DialTCP(s, addr, ipv4.ProtocolNumber)
-	got, ok := err.(*net.OpError)
-	want := tcpip.ErrNoRoute
-	if !ok || got.Err.Error() != want.String() {
-		t.Errorf("Got DialTCP() = %v, want = %v", err, tcpip.ErrNoRoute)
+	switch _, err := DialTCP(s, addr, ipv4.ProtocolNumber); err := err.(type) {
+	case *net.OpError:
+		if err.Err.Error() != (&tcpip.ErrNoRoute{}).String() {
+			t.Errorf("got DialTCP() = %s, want = %s", err, &tcpip.ErrNoRoute{})
+		}
+	default:
+		t.Errorf("got DialTCP(...) = %v, want %s", err, &tcpip.ErrNoRoute{})
 	}
 }
 
diff --git a/pkg/tcpip/errors.go b/pkg/tcpip/errors.go
new file mode 100644
index 000000000..af46da1d2
--- /dev/null
+++ b/pkg/tcpip/errors.go
@@ -0,0 +1,538 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tcpip
+
+import (
+	"fmt"
+)
+
+// Error represents an error in the netstack error space.
+//
+// The error interface is intentionally omitted to avoid loss of type
+// information that would occur if these errors were passed as error.
+type Error interface {
+	isError()
+
+	// IgnoreStats indicates whether this error should be included in failure
+	// counts in tcpip.Stats structs.
+	IgnoreStats() bool
+
+	fmt.Stringer
+}
+
+// ErrAborted indicates the operation was aborted.
+//
+// +stateify savable
+type ErrAborted struct{}
+
+func (*ErrAborted) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrAborted) IgnoreStats() bool {
+	return false
+}
+func (*ErrAborted) String() string {
+	return "operation aborted"
+}
+
+// ErrAddressFamilyNotSupported indicates the operation does not support the
+// given address family.
+//
+// +stateify savable
+type ErrAddressFamilyNotSupported struct{}
+
+func (*ErrAddressFamilyNotSupported) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrAddressFamilyNotSupported) IgnoreStats() bool {
+	return false
+}
+func (*ErrAddressFamilyNotSupported) String() string {
+	return "address family not supported by protocol"
+}
+
+// ErrAlreadyBound indicates the endpoint is already bound.
+//
+// +stateify savable
+type ErrAlreadyBound struct{}
+
+func (*ErrAlreadyBound) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrAlreadyBound) IgnoreStats() bool {
+	return true
+}
+func (*ErrAlreadyBound) String() string { return "endpoint already bound" }
+
+// ErrAlreadyConnected indicates the endpoint is already connected.
+//
+// +stateify savable
+type ErrAlreadyConnected struct{}
+
+func (*ErrAlreadyConnected) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrAlreadyConnected) IgnoreStats() bool {
+	return true
+}
+func (*ErrAlreadyConnected) String() string { return "endpoint is already connected" }
+
+// ErrAlreadyConnecting indicates the endpoint is already connecting.
+//
+// +stateify savable
+type ErrAlreadyConnecting struct{}
+
+func (*ErrAlreadyConnecting) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrAlreadyConnecting) IgnoreStats() bool {
+	return true
+}
+func (*ErrAlreadyConnecting) String() string { return "endpoint is already connecting" }
+
+// ErrBadAddress indicates a bad address was provided.
+//
+// +stateify savable
+type ErrBadAddress struct{}
+
+func (*ErrBadAddress) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrBadAddress) IgnoreStats() bool {
+	return false
+}
+func (*ErrBadAddress) String() string { return "bad address" }
+
+// ErrBadBuffer indicates a bad buffer was provided.
+//
+// +stateify savable
+type ErrBadBuffer struct{}
+
+func (*ErrBadBuffer) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrBadBuffer) IgnoreStats() bool {
+	return false
+}
+func (*ErrBadBuffer) String() string { return "bad buffer" }
+
+// ErrBadLocalAddress indicates a bad local address was provided.
+//
+// +stateify savable
+type ErrBadLocalAddress struct{}
+
+func (*ErrBadLocalAddress) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrBadLocalAddress) IgnoreStats() bool {
+	return false
+}
+func (*ErrBadLocalAddress) String() string { return "bad local address" }
+
+// ErrBroadcastDisabled indicates broadcast is not enabled on the endpoint.
+//
+// +stateify savable
+type ErrBroadcastDisabled struct{}
+
+func (*ErrBroadcastDisabled) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrBroadcastDisabled) IgnoreStats() bool {
+	return false
+}
+func (*ErrBroadcastDisabled) String() string { return "broadcast socket option disabled" }
+
+// ErrClosedForReceive indicates the endpoint is closed for incoming data.
+//
+// +stateify savable
+type ErrClosedForReceive struct{}
+
+func (*ErrClosedForReceive) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrClosedForReceive) IgnoreStats() bool {
+	return false
+}
+func (*ErrClosedForReceive) String() string { return "endpoint is closed for receive" }
+
+// ErrClosedForSend indicates the endpoint is closed for outgoing data.
+//
+// +stateify savable
+type ErrClosedForSend struct{}
+
+func (*ErrClosedForSend) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrClosedForSend) IgnoreStats() bool {
+	return false
+}
+func (*ErrClosedForSend) String() string { return "endpoint is closed for send" }
+
+// ErrConnectStarted indicates the endpoint is connecting asynchronously.
+//
+// +stateify savable
+type ErrConnectStarted struct{}
+
+func (*ErrConnectStarted) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrConnectStarted) IgnoreStats() bool {
+	return true
+}
+func (*ErrConnectStarted) String() string { return "connection attempt started" }
+
+// ErrConnectionAborted indicates the connection was aborted.
+//
+// +stateify savable
+type ErrConnectionAborted struct{}
+
+func (*ErrConnectionAborted) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrConnectionAborted) IgnoreStats() bool {
+	return false
+}
+func (*ErrConnectionAborted) String() string { return "connection aborted" }
+
+// ErrConnectionRefused indicates the connection was refused.
+//
+// +stateify savable
+type ErrConnectionRefused struct{}
+
+func (*ErrConnectionRefused) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrConnectionRefused) IgnoreStats() bool {
+	return false
+}
+func (*ErrConnectionRefused) String() string { return "connection was refused" }
+
+// ErrConnectionReset indicates the connection was reset.
+//
+// +stateify savable
+type ErrConnectionReset struct{}
+
+func (*ErrConnectionReset) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrConnectionReset) IgnoreStats() bool {
+	return false
+}
+func (*ErrConnectionReset) String() string { return "connection reset by peer" }
+
+// ErrDestinationRequired indicates the operation requires a destination
+// address, and one was not provided.
+//
+// +stateify savable
+type ErrDestinationRequired struct{}
+
+func (*ErrDestinationRequired) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrDestinationRequired) IgnoreStats() bool {
+	return false
+}
+func (*ErrDestinationRequired) String() string { return "destination address is required" }
+
+// ErrDuplicateAddress indicates the operation encountered a duplicate address.
+//
+// +stateify savable
+type ErrDuplicateAddress struct{}
+
+func (*ErrDuplicateAddress) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrDuplicateAddress) IgnoreStats() bool {
+	return false
+}
+func (*ErrDuplicateAddress) String() string { return "duplicate address" }
+
+// ErrDuplicateNICID indicates the operation encountered a duplicate NIC ID.
+//
+// +stateify savable
+type ErrDuplicateNICID struct{}
+
+func (*ErrDuplicateNICID) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrDuplicateNICID) IgnoreStats() bool {
+	return false
+}
+func (*ErrDuplicateNICID) String() string { return "duplicate nic id" }
+
+// ErrInvalidEndpointState indicates the endpoint is in an invalid state.
+//
+// +stateify savable
+type ErrInvalidEndpointState struct{}
+
+func (*ErrInvalidEndpointState) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrInvalidEndpointState) IgnoreStats() bool {
+	return false
+}
+func (*ErrInvalidEndpointState) String() string { return "endpoint is in invalid state" }
+
+// ErrInvalidOptionValue indicates an invalid option value was provided.
+//
+// +stateify savable
+type ErrInvalidOptionValue struct{}
+
+func (*ErrInvalidOptionValue) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrInvalidOptionValue) IgnoreStats() bool {
+	return false
+}
+func (*ErrInvalidOptionValue) String() string { return "invalid option value specified" }
+
+// ErrMalformedHeader indicates the operation encountered a malformed header.
+//
+// +stateify savable
+type ErrMalformedHeader struct{}
+
+func (*ErrMalformedHeader) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrMalformedHeader) IgnoreStats() bool {
+	return false
+}
+func (*ErrMalformedHeader) String() string { return "header is malformed" }
+
+// ErrMessageTooLong indicates the operation encountered a message whose length
+// exceeds the maximum permitted.
+//
+// +stateify savable
+type ErrMessageTooLong struct{}
+
+func (*ErrMessageTooLong) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrMessageTooLong) IgnoreStats() bool {
+	return false
+}
+func (*ErrMessageTooLong) String() string { return "message too long" }
+
+// ErrNetworkUnreachable indicates the operation is not able to reach the
+// destination network.
+//
+// +stateify savable
+type ErrNetworkUnreachable struct{}
+
+func (*ErrNetworkUnreachable) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNetworkUnreachable) IgnoreStats() bool {
+	return false
+}
+func (*ErrNetworkUnreachable) String() string { return "network is unreachable" }
+
+// ErrNoBufferSpace indicates no buffer space is available.
+//
+// +stateify savable
+type ErrNoBufferSpace struct{}
+
+func (*ErrNoBufferSpace) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNoBufferSpace) IgnoreStats() bool {
+	return false
+}
+func (*ErrNoBufferSpace) String() string { return "no buffer space available" }
+
+// ErrNoPortAvailable indicates no port could be allocated for the operation.
+//
+// +stateify savable
+type ErrNoPortAvailable struct{}
+
+func (*ErrNoPortAvailable) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNoPortAvailable) IgnoreStats() bool {
+	return false
+}
+func (*ErrNoPortAvailable) String() string { return "no ports are available" }
+
+// ErrNoRoute indicates the operation is not able to find a route to the
+// destination.
+//
+// +stateify savable
+type ErrNoRoute struct{}
+
+func (*ErrNoRoute) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNoRoute) IgnoreStats() bool {
+	return false
+}
+func (*ErrNoRoute) String() string { return "no route" }
+
+// ErrNoSuchFile is used to indicate that ENOENT should be returned the to
+// calling application.
+//
+// +stateify savable
+type ErrNoSuchFile struct{}
+
+func (*ErrNoSuchFile) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNoSuchFile) IgnoreStats() bool {
+	return false
+}
+func (*ErrNoSuchFile) String() string { return "no such file" }
+
+// ErrNotConnected indicates the endpoint is not connected.
+//
+// +stateify savable
+type ErrNotConnected struct{}
+
+func (*ErrNotConnected) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNotConnected) IgnoreStats() bool {
+	return false
+}
+func (*ErrNotConnected) String() string { return "endpoint not connected" }
+
+// ErrNotPermitted indicates the operation is not permitted.
+//
+// +stateify savable
+type ErrNotPermitted struct{}
+
+func (*ErrNotPermitted) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNotPermitted) IgnoreStats() bool {
+	return false
+}
+func (*ErrNotPermitted) String() string { return "operation not permitted" }
+
+// ErrNotSupported indicates the operation is not supported.
+//
+// +stateify savable
+type ErrNotSupported struct{}
+
+func (*ErrNotSupported) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrNotSupported) IgnoreStats() bool {
+	return false
+}
+func (*ErrNotSupported) String() string { return "operation not supported" }
+
+// ErrPortInUse indicates the provided port is in use.
+//
+// +stateify savable
+type ErrPortInUse struct{}
+
+func (*ErrPortInUse) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrPortInUse) IgnoreStats() bool {
+	return false
+}
+func (*ErrPortInUse) String() string { return "port is in use" }
+
+// ErrQueueSizeNotSupported indicates the endpoint does not allow queue size
+// operation.
+//
+// +stateify savable
+type ErrQueueSizeNotSupported struct{}
+
+func (*ErrQueueSizeNotSupported) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrQueueSizeNotSupported) IgnoreStats() bool {
+	return false
+}
+func (*ErrQueueSizeNotSupported) String() string { return "queue size querying not supported" }
+
+// ErrTimeout indicates the operation timed out.
+//
+// +stateify savable
+type ErrTimeout struct{}
+
+func (*ErrTimeout) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrTimeout) IgnoreStats() bool {
+	return false
+}
+func (*ErrTimeout) String() string { return "operation timed out" }
+
+// ErrUnknownDevice indicates an unknown device identifier was provided.
+//
+// +stateify savable
+type ErrUnknownDevice struct{}
+
+func (*ErrUnknownDevice) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrUnknownDevice) IgnoreStats() bool {
+	return false
+}
+func (*ErrUnknownDevice) String() string { return "unknown device" }
+
+// ErrUnknownNICID indicates an unknown NIC ID was provided.
+//
+// +stateify savable
+type ErrUnknownNICID struct{}
+
+func (*ErrUnknownNICID) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrUnknownNICID) IgnoreStats() bool {
+	return false
+}
+func (*ErrUnknownNICID) String() string { return "unknown nic id" }
+
+// ErrUnknownProtocol indicates an unknown protocol was requested.
+//
+// +stateify savable
+type ErrUnknownProtocol struct{}
+
+func (*ErrUnknownProtocol) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrUnknownProtocol) IgnoreStats() bool {
+	return false
+}
+func (*ErrUnknownProtocol) String() string { return "unknown protocol" }
+
+// ErrUnknownProtocolOption indicates an unknown protocol option was provided.
+//
+// +stateify savable
+type ErrUnknownProtocolOption struct{}
+
+func (*ErrUnknownProtocolOption) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrUnknownProtocolOption) IgnoreStats() bool {
+	return false
+}
+func (*ErrUnknownProtocolOption) String() string { return "unknown option for protocol" }
+
+// ErrWouldBlock indicates the operation would block.
+//
+// +stateify savable
+type ErrWouldBlock struct{}
+
+func (*ErrWouldBlock) isError() {}
+
+// IgnoreStats implements Error.
+func (*ErrWouldBlock) IgnoreStats() bool {
+	return true
+}
+func (*ErrWouldBlock) String() string { return "operation would block" }
diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index 5580d6a78..f2403978c 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -453,9 +453,9 @@ const (
 )
 
 // ScopeForIPv6Address returns the scope for an IPv6 address.
-func ScopeForIPv6Address(addr tcpip.Address) (IPv6AddressScope, *tcpip.Error) {
+func ScopeForIPv6Address(addr tcpip.Address) (IPv6AddressScope, tcpip.Error) {
 	if len(addr) != IPv6AddressSize {
-		return GlobalScope, tcpip.ErrBadAddress
+		return GlobalScope, &tcpip.ErrBadAddress{}
 	}
 
 	switch {
diff --git a/pkg/tcpip/header/ipv6_test.go b/pkg/tcpip/header/ipv6_test.go
index e3fbd64f3..f10f446a6 100644
--- a/pkg/tcpip/header/ipv6_test.go
+++ b/pkg/tcpip/header/ipv6_test.go
@@ -299,7 +299,7 @@ func TestScopeForIPv6Address(t *testing.T) {
 		name  string
 		addr  tcpip.Address
 		scope header.IPv6AddressScope
-		err   *tcpip.Error
+		err   tcpip.Error
 	}{
 		{
 			name:  "Unique Local",
@@ -329,15 +329,15 @@ func TestScopeForIPv6Address(t *testing.T) {
 			name:  "IPv4",
 			addr:  "\x01\x02\x03\x04",
 			scope: header.GlobalScope,
-			err:   tcpip.ErrBadAddress,
+			err:   &tcpip.ErrBadAddress{},
 		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			got, err := header.ScopeForIPv6Address(test.addr)
-			if err != test.err {
-				t.Errorf("got header.IsV6UniqueLocalAddress(%s) = (_, %v), want = (_, %v)", test.addr, err, test.err)
+			if diff := cmp.Diff(test.err, err); diff != "" {
+				t.Errorf("unexpected error from header.IsV6UniqueLocalAddress(%s), (-want, +got):\n%s", test.addr, diff)
 			}
 			if got != test.scope {
 				t.Errorf("got header.IsV6UniqueLocalAddress(%s) = (%d, _), want = (%d, _)", test.addr, got, test.scope)
diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index a068d93a4..cd76272de 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -229,7 +229,7 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket stores outbound packets into the channel.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	p := PacketInfo{
 		Pkt:   pkt,
 		Proto: protocol,
@@ -243,7 +243,7 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 }
 
 // WritePackets stores outbound packets into the channel.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := 0
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		p := PacketInfo{
diff --git a/pkg/tcpip/link/ethernet/ethernet.go b/pkg/tcpip/link/ethernet/ethernet.go
index 2f2d9d4ac..d873766a6 100644
--- a/pkg/tcpip/link/ethernet/ethernet.go
+++ b/pkg/tcpip/link/ethernet/ethernet.go
@@ -61,13 +61,13 @@ func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.AddHeader(e.Endpoint.LinkAddress(), r.RemoteLinkAddress, proto, pkt)
 	return e.Endpoint.WritePacket(r, gso, proto, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	linkAddr := e.Endpoint.LinkAddress()
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index f86c383d8..0164d851b 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -57,7 +57,7 @@ import (
 // linkDispatcher reads packets from the link FD and dispatches them to the
 // NetworkDispatcher.
 type linkDispatcher interface {
-	dispatch() (bool, *tcpip.Error)
+	dispatch() (bool, tcpip.Error)
 }
 
 // PacketDispatchMode are the various supported methods of receiving and
@@ -118,7 +118,7 @@ type endpoint struct {
 
 	// closed is a function to be called when the FD's peer (if any) closes
 	// its end of the communication pipe.
-	closed func(*tcpip.Error)
+	closed func(tcpip.Error)
 
 	inboundDispatchers []linkDispatcher
 	dispatcher         stack.NetworkDispatcher
@@ -149,7 +149,7 @@ type Options struct {
 
 	// ClosedFunc is a function to be called when an endpoint's peer (if
 	// any) closes its end of the communication pipe.
-	ClosedFunc func(*tcpip.Error)
+	ClosedFunc func(tcpip.Error)
 
 	// Address is the link address for this endpoint. Only used if
 	// EthernetHeader is true.
@@ -411,7 +411,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if e.hdrSize > 0 {
 		e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
 	}
@@ -451,7 +451,7 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 	return rawfile.NonBlockingWriteIovec(fd, builder.Build())
 }
 
-func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, *tcpip.Error) {
+func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, tcpip.Error) {
 	// Send a batch of packets through batchFD.
 	mmsgHdrs := make([]rawfile.MMsgHdr, 0, len(batch))
 	for _, pkt := range batch {
@@ -518,7 +518,7 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, *tc
 //  - pkt.EgressRoute
 //  - pkt.GSOOptions
 //  - pkt.NetworkProtocolNumber
-func (e *endpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	// Preallocate to avoid repeated reallocation as we append to batch.
 	// batchSz is 47 because when SWGSO is in use then a single 65KB TCP
 	// segment can get split into 46 segments of 1420 bytes and a single 216
@@ -562,13 +562,13 @@ func viewsEqual(vs1, vs2 []buffer.View) bool {
 }
 
 // InjectOutobund implements stack.InjectableEndpoint.InjectOutbound.
-func (e *endpoint) InjectOutbound(dest tcpip.Address, packet []byte) *tcpip.Error {
+func (e *endpoint) InjectOutbound(dest tcpip.Address, packet []byte) tcpip.Error {
 	return rawfile.NonBlockingWrite(e.fds[0], packet)
 }
 
 // dispatchLoop reads packets from the file descriptor in a loop and dispatches
 // them to the network stack.
-func (e *endpoint) dispatchLoop(inboundDispatcher linkDispatcher) *tcpip.Error {
+func (e *endpoint) dispatchLoop(inboundDispatcher linkDispatcher) tcpip.Error {
 	for {
 		cont, err := inboundDispatcher.dispatch()
 		if err != nil || !cont {
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index e2985cb84..e82371798 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/pkg/tcpip/link/fdbased/endpoint_test.go
@@ -95,7 +95,7 @@ func newContext(t *testing.T, opt *Options) *context {
 	}
 
 	done := make(chan struct{}, 2)
-	opt.ClosedFunc = func(*tcpip.Error) {
+	opt.ClosedFunc = func(tcpip.Error) {
 		done <- struct{}{}
 	}
 
diff --git a/pkg/tcpip/link/fdbased/mmap.go b/pkg/tcpip/link/fdbased/mmap.go
index c475dda20..a2b63fe6b 100644
--- a/pkg/tcpip/link/fdbased/mmap.go
+++ b/pkg/tcpip/link/fdbased/mmap.go
@@ -129,7 +129,7 @@ type packetMMapDispatcher struct {
 	ringOffset int
 }
 
-func (d *packetMMapDispatcher) readMMappedPacket() ([]byte, *tcpip.Error) {
+func (d *packetMMapDispatcher) readMMappedPacket() ([]byte, tcpip.Error) {
 	hdr := tPacketHdr(d.ringBuffer[d.ringOffset*tpFrameSize:])
 	for hdr.tpStatus()&tpStatusUser == 0 {
 		event := rawfile.PollEvent{
@@ -163,7 +163,7 @@ func (d *packetMMapDispatcher) readMMappedPacket() ([]byte, *tcpip.Error) {
 
 // dispatch reads packets from an mmaped ring buffer and dispatches them to the
 // network stack.
-func (d *packetMMapDispatcher) dispatch() (bool, *tcpip.Error) {
+func (d *packetMMapDispatcher) dispatch() (bool, tcpip.Error) {
 	pkt, err := d.readMMappedPacket()
 	if err != nil {
 		return false, err
diff --git a/pkg/tcpip/link/fdbased/packet_dispatchers.go b/pkg/tcpip/link/fdbased/packet_dispatchers.go
index edab110b5..ecae1ad2d 100644
--- a/pkg/tcpip/link/fdbased/packet_dispatchers.go
+++ b/pkg/tcpip/link/fdbased/packet_dispatchers.go
@@ -139,7 +139,7 @@ func newReadVDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
 }
 
 // dispatch reads one packet from the file descriptor and dispatches it.
-func (d *readVDispatcher) dispatch() (bool, *tcpip.Error) {
+func (d *readVDispatcher) dispatch() (bool, tcpip.Error) {
 	n, err := rawfile.BlockingReadv(d.fd, d.buf.nextIovecs())
 	if n == 0 || err != nil {
 		return false, err
@@ -226,7 +226,7 @@ func newRecvMMsgDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
 
 // recvMMsgDispatch reads more than one packet at a time from the file
 // descriptor and dispatches it.
-func (d *recvMMsgDispatcher) dispatch() (bool, *tcpip.Error) {
+func (d *recvMMsgDispatcher) dispatch() (bool, tcpip.Error) {
 	// Fill message headers.
 	for k := range d.msgHdrs {
 		if d.msgHdrs[k].Msg.Iovlen > 0 {
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index ac6a6be87..691467870 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -76,7 +76,7 @@ func (*endpoint) Wait() {}
 
 // WritePacket implements stack.LinkEndpoint.WritePacket. It delivers outbound
 // packets to the network-layer dispatcher.
-func (e *endpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	// Construct data as the unparsed portion for the loopback packet.
 	data := buffer.NewVectorisedView(pkt.Size(), pkt.Views())
 
@@ -92,7 +92,7 @@ func (e *endpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, protocol tcpip.N
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
diff --git a/pkg/tcpip/link/muxed/injectable.go b/pkg/tcpip/link/muxed/injectable.go
index 316f508e6..668f72eee 100644
--- a/pkg/tcpip/link/muxed/injectable.go
+++ b/pkg/tcpip/link/muxed/injectable.go
@@ -87,10 +87,10 @@ func (m *InjectableEndpoint) InjectInbound(protocol tcpip.NetworkProtocolNumber,
 // WritePackets writes outbound packets to the appropriate
 // LinkInjectableEndpoint based on the RemoteAddress. HandleLocal only works if
 // r.RemoteAddress has a route registered in this endpoint.
-func (m *InjectableEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (m *InjectableEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	endpoint, ok := m.routes[r.RemoteAddress]
 	if !ok {
-		return 0, tcpip.ErrNoRoute
+		return 0, &tcpip.ErrNoRoute{}
 	}
 	return endpoint.WritePackets(r, gso, pkts, protocol)
 }
@@ -98,19 +98,19 @@ func (m *InjectableEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkt
 // WritePacket writes outbound packets to the appropriate LinkInjectableEndpoint
 // based on the RemoteAddress. HandleLocal only works if r.RemoteAddress has a
 // route registered in this endpoint.
-func (m *InjectableEndpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (m *InjectableEndpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if endpoint, ok := m.routes[r.RemoteAddress]; ok {
 		return endpoint.WritePacket(r, gso, protocol, pkt)
 	}
-	return tcpip.ErrNoRoute
+	return &tcpip.ErrNoRoute{}
 }
 
 // InjectOutbound writes outbound packets to the appropriate
 // LinkInjectableEndpoint based on the dest address.
-func (m *InjectableEndpoint) InjectOutbound(dest tcpip.Address, packet []byte) *tcpip.Error {
+func (m *InjectableEndpoint) InjectOutbound(dest tcpip.Address, packet []byte) tcpip.Error {
 	endpoint, ok := m.routes[dest]
 	if !ok {
-		return tcpip.ErrNoRoute
+		return &tcpip.ErrNoRoute{}
 	}
 	return endpoint.InjectOutbound(dest, packet)
 }
diff --git a/pkg/tcpip/link/nested/nested.go b/pkg/tcpip/link/nested/nested.go
index 814a54f23..97ad9fdd5 100644
--- a/pkg/tcpip/link/nested/nested.go
+++ b/pkg/tcpip/link/nested/nested.go
@@ -113,12 +113,12 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	return e.child.WritePacket(r, gso, protocol, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	return e.child.WritePackets(r, gso, pkts, protocol)
 }
 
diff --git a/pkg/tcpip/link/packetsocket/endpoint.go b/pkg/tcpip/link/packetsocket/endpoint.go
index c95cdd681..6cbe18a56 100644
--- a/pkg/tcpip/link/packetsocket/endpoint.go
+++ b/pkg/tcpip/link/packetsocket/endpoint.go
@@ -35,13 +35,13 @@ func New(lower stack.LinkEndpoint) stack.LinkEndpoint {
 }
 
 // WritePacket implements stack.LinkEndpoint.WritePacket.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, protocol, pkt)
 	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, pkt.NetworkProtocolNumber, pkt)
 	}
diff --git a/pkg/tcpip/link/pipe/pipe.go b/pkg/tcpip/link/pipe/pipe.go
index 36aa9055c..bbe84f220 100644
--- a/pkg/tcpip/link/pipe/pipe.go
+++ b/pkg/tcpip/link/pipe/pipe.go
@@ -75,7 +75,7 @@ func (e *Endpoint) deliverPackets(r stack.RouteInfo, proto tcpip.NetworkProtocol
 }
 
 // WritePacket implements stack.LinkEndpoint.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if e.linked.IsAttached() {
 		var pkts stack.PacketBufferList
 		pkts.PushBack(pkt)
@@ -86,7 +86,7 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.Netw
 }
 
 // WritePackets implements stack.LinkEndpoint.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	if e.linked.IsAttached() {
 		e.deliverPackets(r, proto, pkts)
 	}
diff --git a/pkg/tcpip/link/qdisc/fifo/endpoint.go b/pkg/tcpip/link/qdisc/fifo/endpoint.go
index 03efba606..128ef6e87 100644
--- a/pkg/tcpip/link/qdisc/fifo/endpoint.go
+++ b/pkg/tcpip/link/qdisc/fifo/endpoint.go
@@ -150,7 +150,7 @@ func (e *endpoint) GSOMaxSize() uint32 {
 }
 
 // WritePacket implements stack.LinkEndpoint.WritePacket.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	// WritePacket caller's do not set the following fields in PacketBuffer
 	// so we populate them here.
 	pkt.EgressRoute = r
@@ -158,7 +158,7 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 	pkt.NetworkProtocolNumber = protocol
 	d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
 	if !d.q.enqueue(pkt) {
-		return tcpip.ErrNoBufferSpace
+		return &tcpip.ErrNoBufferSpace{}
 	}
 	d.newPacketWaker.Assert()
 	return nil
@@ -171,7 +171,7 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 //  - pkt.EgressRoute
 //  - pkt.GSOOptions
 //  - pkt.NetworkProtocolNumber
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	enqueued := 0
 	for pkt := pkts.Front(); pkt != nil; {
 		d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
@@ -180,7 +180,7 @@ func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.Pa
 			if enqueued > 0 {
 				d.newPacketWaker.Assert()
 			}
-			return enqueued, tcpip.ErrNoBufferSpace
+			return enqueued, &tcpip.ErrNoBufferSpace{}
 		}
 		pkt = nxt
 		enqueued++
diff --git a/pkg/tcpip/link/rawfile/BUILD b/pkg/tcpip/link/rawfile/BUILD
index 6c410c5a6..e1047da50 100644
--- a/pkg/tcpip/link/rawfile/BUILD
+++ b/pkg/tcpip/link/rawfile/BUILD
@@ -27,5 +27,6 @@ go_test(
     library = "rawfile",
     deps = [
         "//pkg/tcpip",
+        "@com_github_google_go_cmp//cmp:go_default_library",
     ],
 )
diff --git a/pkg/tcpip/link/rawfile/errors.go b/pkg/tcpip/link/rawfile/errors.go
index 604868fd8..406b97709 100644
--- a/pkg/tcpip/link/rawfile/errors.go
+++ b/pkg/tcpip/link/rawfile/errors.go
@@ -17,7 +17,6 @@
 package rawfile
 
 import (
-	"fmt"
 	"syscall"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -25,48 +24,54 @@ import (
 
 const maxErrno = 134
 
-var translations [maxErrno]*tcpip.Error
-
 // TranslateErrno translate an errno from the syscall package into a
-// *tcpip.Error.
+// tcpip.Error.
 //
 // Valid, but unrecognized errnos will be translated to
-// tcpip.ErrInvalidEndpointState (EINVAL).
-func TranslateErrno(e syscall.Errno) *tcpip.Error {
-	if e > 0 && e < syscall.Errno(len(translations)) {
-		if err := translations[e]; err != nil {
-			return err
-		}
-	}
-	return tcpip.ErrInvalidEndpointState
-}
-
-func addTranslation(host syscall.Errno, trans *tcpip.Error) {
-	if translations[host] != nil {
-		panic(fmt.Sprintf("duplicate translation for host errno %q (%d)", host.Error(), host))
+// *tcpip.ErrInvalidEndpointState (EINVAL).
+func TranslateErrno(e syscall.Errno) tcpip.Error {
+	switch e {
+	case syscall.EEXIST:
+		return &tcpip.ErrDuplicateAddress{}
+	case syscall.ENETUNREACH:
+		return &tcpip.ErrNoRoute{}
+	case syscall.EINVAL:
+		return &tcpip.ErrInvalidEndpointState{}
+	case syscall.EALREADY:
+		return &tcpip.ErrAlreadyConnecting{}
+	case syscall.EISCONN:
+		return &tcpip.ErrAlreadyConnected{}
+	case syscall.EADDRINUSE:
+		return &tcpip.ErrPortInUse{}
+	case syscall.EADDRNOTAVAIL:
+		return &tcpip.ErrBadLocalAddress{}
+	case syscall.EPIPE:
+		return &tcpip.ErrClosedForSend{}
+	case syscall.EWOULDBLOCK:
+		return &tcpip.ErrWouldBlock{}
+	case syscall.ECONNREFUSED:
+		return &tcpip.ErrConnectionRefused{}
+	case syscall.ETIMEDOUT:
+		return &tcpip.ErrTimeout{}
+	case syscall.EINPROGRESS:
+		return &tcpip.ErrConnectStarted{}
+	case syscall.EDESTADDRREQ:
+		return &tcpip.ErrDestinationRequired{}
+	case syscall.ENOTSUP:
+		return &tcpip.ErrNotSupported{}
+	case syscall.ENOTTY:
+		return &tcpip.ErrQueueSizeNotSupported{}
+	case syscall.ENOTCONN:
+		return &tcpip.ErrNotConnected{}
+	case syscall.ECONNRESET:
+		return &tcpip.ErrConnectionReset{}
+	case syscall.ECONNABORTED:
+		return &tcpip.ErrConnectionAborted{}
+	case syscall.EMSGSIZE:
+		return &tcpip.ErrMessageTooLong{}
+	case syscall.ENOBUFS:
+		return &tcpip.ErrNoBufferSpace{}
+	default:
+		return &tcpip.ErrInvalidEndpointState{}
 	}
-	translations[host] = trans
-}
-
-func init() {
-	addTranslation(syscall.EEXIST, tcpip.ErrDuplicateAddress)
-	addTranslation(syscall.ENETUNREACH, tcpip.ErrNoRoute)
-	addTranslation(syscall.EINVAL, tcpip.ErrInvalidEndpointState)
-	addTranslation(syscall.EALREADY, tcpip.ErrAlreadyConnecting)
-	addTranslation(syscall.EISCONN, tcpip.ErrAlreadyConnected)
-	addTranslation(syscall.EADDRINUSE, tcpip.ErrPortInUse)
-	addTranslation(syscall.EADDRNOTAVAIL, tcpip.ErrBadLocalAddress)
-	addTranslation(syscall.EPIPE, tcpip.ErrClosedForSend)
-	addTranslation(syscall.EWOULDBLOCK, tcpip.ErrWouldBlock)
-	addTranslation(syscall.ECONNREFUSED, tcpip.ErrConnectionRefused)
-	addTranslation(syscall.ETIMEDOUT, tcpip.ErrTimeout)
-	addTranslation(syscall.EINPROGRESS, tcpip.ErrConnectStarted)
-	addTranslation(syscall.EDESTADDRREQ, tcpip.ErrDestinationRequired)
-	addTranslation(syscall.ENOTSUP, tcpip.ErrNotSupported)
-	addTranslation(syscall.ENOTTY, tcpip.ErrQueueSizeNotSupported)
-	addTranslation(syscall.ENOTCONN, tcpip.ErrNotConnected)
-	addTranslation(syscall.ECONNRESET, tcpip.ErrConnectionReset)
-	addTranslation(syscall.ECONNABORTED, tcpip.ErrConnectionAborted)
-	addTranslation(syscall.EMSGSIZE, tcpip.ErrMessageTooLong)
-	addTranslation(syscall.ENOBUFS, tcpip.ErrNoBufferSpace)
 }
diff --git a/pkg/tcpip/link/rawfile/errors_test.go b/pkg/tcpip/link/rawfile/errors_test.go
index e4cdc66bd..61aea1744 100644
--- a/pkg/tcpip/link/rawfile/errors_test.go
+++ b/pkg/tcpip/link/rawfile/errors_test.go
@@ -20,34 +20,35 @@ import (
 	"syscall"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
 func TestTranslateErrno(t *testing.T) {
 	for _, test := range []struct {
 		errno      syscall.Errno
-		translated *tcpip.Error
+		translated tcpip.Error
 	}{
 		{
 			errno:      syscall.Errno(0),
-			translated: tcpip.ErrInvalidEndpointState,
+			translated: &tcpip.ErrInvalidEndpointState{},
 		},
 		{
 			errno:      syscall.Errno(maxErrno),
-			translated: tcpip.ErrInvalidEndpointState,
+			translated: &tcpip.ErrInvalidEndpointState{},
 		},
 		{
 			errno:      syscall.Errno(514),
-			translated: tcpip.ErrInvalidEndpointState,
+			translated: &tcpip.ErrInvalidEndpointState{},
 		},
 		{
 			errno:      syscall.EEXIST,
-			translated: tcpip.ErrDuplicateAddress,
+			translated: &tcpip.ErrDuplicateAddress{},
 		},
 	} {
 		got := TranslateErrno(test.errno)
-		if got != test.translated {
-			t.Errorf("TranslateErrno(%q) = %q, want %q", test.errno, got, test.translated)
+		if diff := cmp.Diff(test.translated, got); diff != "" {
+			t.Errorf("unexpected result from TranslateErrno(%q), (-want, +got):\n%s", test.errno, diff)
 		}
 	}
 }
diff --git a/pkg/tcpip/link/rawfile/rawfile_unsafe.go b/pkg/tcpip/link/rawfile/rawfile_unsafe.go
index f4c32c2da..06f3ee21e 100644
--- a/pkg/tcpip/link/rawfile/rawfile_unsafe.go
+++ b/pkg/tcpip/link/rawfile/rawfile_unsafe.go
@@ -52,7 +52,7 @@ func GetMTU(name string) (uint32, error) {
 
 // NonBlockingWrite writes the given buffer to a file descriptor. It fails if
 // partial data is written.
-func NonBlockingWrite(fd int, buf []byte) *tcpip.Error {
+func NonBlockingWrite(fd int, buf []byte) tcpip.Error {
 	var ptr unsafe.Pointer
 	if len(buf) > 0 {
 		ptr = unsafe.Pointer(&buf[0])
@@ -68,7 +68,7 @@ func NonBlockingWrite(fd int, buf []byte) *tcpip.Error {
 
 // NonBlockingWriteIovec writes iovec to a file descriptor in a single syscall.
 // It fails if partial data is written.
-func NonBlockingWriteIovec(fd int, iovec []syscall.Iovec) *tcpip.Error {
+func NonBlockingWriteIovec(fd int, iovec []syscall.Iovec) tcpip.Error {
 	iovecLen := uintptr(len(iovec))
 	_, _, e := syscall.RawSyscall(syscall.SYS_WRITEV, uintptr(fd), uintptr(unsafe.Pointer(&iovec[0])), iovecLen)
 	if e != 0 {
@@ -78,7 +78,7 @@ func NonBlockingWriteIovec(fd int, iovec []syscall.Iovec) *tcpip.Error {
 }
 
 // NonBlockingSendMMsg sends multiple messages on a socket.
-func NonBlockingSendMMsg(fd int, msgHdrs []MMsgHdr) (int, *tcpip.Error) {
+func NonBlockingSendMMsg(fd int, msgHdrs []MMsgHdr) (int, tcpip.Error) {
 	n, _, e := syscall.RawSyscall6(unix.SYS_SENDMMSG, uintptr(fd), uintptr(unsafe.Pointer(&msgHdrs[0])), uintptr(len(msgHdrs)), syscall.MSG_DONTWAIT, 0, 0)
 	if e != 0 {
 		return 0, TranslateErrno(e)
@@ -97,7 +97,7 @@ type PollEvent struct {
 // BlockingRead reads from a file descriptor that is set up as non-blocking. If
 // no data is available, it will block in a poll() syscall until the file
 // descriptor becomes readable.
-func BlockingRead(fd int, b []byte) (int, *tcpip.Error) {
+func BlockingRead(fd int, b []byte) (int, tcpip.Error) {
 	for {
 		n, _, e := syscall.RawSyscall(syscall.SYS_READ, uintptr(fd), uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
 		if e == 0 {
@@ -119,7 +119,7 @@ func BlockingRead(fd int, b []byte) (int, *tcpip.Error) {
 // BlockingReadv reads from a file descriptor that is set up as non-blocking and
 // stores the data in a list of iovecs buffers. If no data is available, it will
 // block in a poll() syscall until the file descriptor becomes readable.
-func BlockingReadv(fd int, iovecs []syscall.Iovec) (int, *tcpip.Error) {
+func BlockingReadv(fd int, iovecs []syscall.Iovec) (int, tcpip.Error) {
 	for {
 		n, _, e := syscall.RawSyscall(syscall.SYS_READV, uintptr(fd), uintptr(unsafe.Pointer(&iovecs[0])), uintptr(len(iovecs)))
 		if e == 0 {
@@ -149,7 +149,7 @@ type MMsgHdr struct {
 // and stores the received messages in a slice of MMsgHdr structures. If no data
 // is available, it will block in a poll() syscall until the file descriptor
 // becomes readable.
-func BlockingRecvMMsg(fd int, msgHdrs []MMsgHdr) (int, *tcpip.Error) {
+func BlockingRecvMMsg(fd int, msgHdrs []MMsgHdr) (int, tcpip.Error) {
 	for {
 		n, _, e := syscall.RawSyscall6(syscall.SYS_RECVMMSG, uintptr(fd), uintptr(unsafe.Pointer(&msgHdrs[0])), uintptr(len(msgHdrs)), syscall.MSG_DONTWAIT, 0, 0)
 		if e == 0 {
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index 6c937c858..2599bc406 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -203,7 +203,7 @@ func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 
 // WritePacket writes outbound packets to the file descriptor. If it is not
 // currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
 
 	views := pkt.Views()
@@ -213,14 +213,14 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, protocol tcpip.N
 	e.mu.Unlock()
 
 	if !ok {
-		return tcpip.ErrWouldBlock
+		return &tcpip.ErrWouldBlock{}
 	}
 
 	return nil
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (*endpoint) WritePackets(stack.RouteInfo, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
diff --git a/pkg/tcpip/link/sharedmem/sharedmem_test.go b/pkg/tcpip/link/sharedmem/sharedmem_test.go
index 23242b9e0..d480ad656 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem_test.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem_test.go
@@ -425,8 +425,9 @@ func TestFillTxQueue(t *testing.T) {
 		ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 		Data:               buf.ToVectorisedView(),
 	})
-	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != want {
-		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
+	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
 }
 
@@ -493,8 +494,9 @@ func TestFillTxQueueAfterBadCompletion(t *testing.T) {
 		ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 		Data:               buf.ToVectorisedView(),
 	})
-	if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != want {
-		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
+	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
 }
 
@@ -538,8 +540,8 @@ func TestFillTxMemory(t *testing.T) {
 		Data:               buf.ToVectorisedView(),
 	})
 	err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
-	if want := tcpip.ErrWouldBlock; err != want {
-		t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 	}
 }
 
@@ -579,8 +581,9 @@ func TestFillTxMemoryWithMultiBuffer(t *testing.T) {
 			ReserveHeaderBytes: int(c.ep.MaxHeaderLength()),
 			Data:               buffer.NewView(bufferSize).ToVectorisedView(),
 		})
-		if want, err := tcpip.ErrWouldBlock, c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt); err != want {
-			t.Fatalf("WritePacket return unexpected result: got %v, want %v", err, want)
+		err := c.ep.WritePacket(r, nil /* gso */, header.IPv4ProtocolNumber, pkt)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Fatalf("got WritePacket(...) = %v, want %s", err, &tcpip.ErrWouldBlock{})
 		}
 	}
 
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 5859851d8..bd2b8d4bf 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -187,7 +187,7 @@ func (e *endpoint) dumpPacket(dir direction, gso *stack.GSO, protocol tcpip.Netw
 // WritePacket implements the stack.LinkEndpoint interface. It is called by
 // higher-level protocols to write packets; it just logs the packet and
 // forwards the request to the lower endpoint.
-func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	e.dumpPacket(directionSend, gso, protocol, pkt)
 	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
 }
@@ -195,7 +195,7 @@ func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 // WritePackets implements the stack.LinkEndpoint interface. It is called by
 // higher-level protocols to write packets; it just logs the packet and
 // forwards the request to the lower endpoint.
-func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		e.dumpPacket(directionSend, gso, protocol, pkt)
 	}
diff --git a/pkg/tcpip/link/tun/device.go b/pkg/tcpip/link/tun/device.go
index bfac358f4..3829ca9c9 100644
--- a/pkg/tcpip/link/tun/device.go
+++ b/pkg/tcpip/link/tun/device.go
@@ -149,10 +149,10 @@ func attachOrCreateNIC(s *stack.Stack, name, prefix string, linkCaps stack.LinkE
 		err := s.CreateNICWithOptions(endpoint.nicID, endpoint, stack.NICOptions{
 			Name: endpoint.name,
 		})
-		switch err {
+		switch err.(type) {
 		case nil:
 			return endpoint, nil
-		case tcpip.ErrDuplicateNICID:
+		case *tcpip.ErrDuplicateNICID:
 			// Race detected: A NIC has been created in between.
 			continue
 		default:
diff --git a/pkg/tcpip/link/waitable/waitable.go b/pkg/tcpip/link/waitable/waitable.go
index 30f1ad540..20259b285 100644
--- a/pkg/tcpip/link/waitable/waitable.go
+++ b/pkg/tcpip/link/waitable/waitable.go
@@ -108,7 +108,7 @@ func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
 // WritePacket implements stack.LinkEndpoint.WritePacket. It is called by
 // higher-level protocols to write packets. It only forwards packets to the
 // lower endpoint if Wait or WaitWrite haven't been called.
-func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if !e.writeGate.Enter() {
 		return nil
 	}
@@ -121,7 +121,7 @@ func (e *Endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip
 // WritePackets implements stack.LinkEndpoint.WritePackets. It is called by
 // higher-level protocols to write packets. It only forwards packets to the
 // lower endpoint if Wait or WaitWrite haven't been called.
-func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *Endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	if !e.writeGate.Enter() {
 		return pkts.Len(), nil
 	}
diff --git a/pkg/tcpip/link/waitable/waitable_test.go b/pkg/tcpip/link/waitable/waitable_test.go
index b139de7dd..e368a9eaa 100644
--- a/pkg/tcpip/link/waitable/waitable_test.go
+++ b/pkg/tcpip/link/waitable/waitable_test.go
@@ -69,13 +69,13 @@ func (e *countedEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e *countedEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) *tcpip.Error {
+func (e *countedEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	e.writeCount++
 	return nil
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (e *countedEndpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *countedEndpoint) WritePackets(_ stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, _ tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	e.writeCount += pkts.Len()
 	return pkts.Len(), nil
 }
diff --git a/pkg/tcpip/network/BUILD b/pkg/tcpip/network/BUILD
index 9ebf31b78..0caa65251 100644
--- a/pkg/tcpip/network/BUILD
+++ b/pkg/tcpip/network/BUILD
@@ -25,5 +25,6 @@ go_test(
         "//pkg/tcpip/transport/icmp",
         "//pkg/tcpip/transport/tcp",
         "//pkg/tcpip/transport/udp",
+        "@com_github_google_go_cmp//cmp:go_default_library",
     ],
 )
diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index 6bc8c5c02..7838cc753 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -55,9 +55,9 @@ type endpoint struct {
 	stats         sharedStats
 }
 
-func (e *endpoint) Enable() *tcpip.Error {
+func (e *endpoint) Enable() tcpip.Error {
 	if !e.nic.Enabled() {
-		return tcpip.ErrNotPermitted
+		return &tcpip.ErrNotPermitted{}
 	}
 
 	e.setEnabled(true)
@@ -105,8 +105,8 @@ func (e *endpoint) Close() {
 	e.protocol.forgetEndpoint(e.nic.ID())
 }
 
-func (*endpoint) WritePacket(*stack.Route, *stack.GSO, stack.NetworkHeaderParams, *stack.PacketBuffer) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) WritePacket(*stack.Route, *stack.GSO, stack.NetworkHeaderParams, *stack.PacketBuffer) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // NetworkProtocolNumber implements stack.NetworkEndpoint.NetworkProtocolNumber.
@@ -115,12 +115,12 @@ func (*endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (*endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList, stack.NetworkHeaderParams) (int, *tcpip.Error) {
-	return 0, tcpip.ErrNotSupported
+func (*endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList, stack.NetworkHeaderParams) (int, tcpip.Error) {
+	return 0, &tcpip.ErrNotSupported{}
 }
 
-func (*endpoint) WriteHeaderIncludedPacket(*stack.Route, *stack.PacketBuffer) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) WriteHeaderIncludedPacket(*stack.Route, *stack.PacketBuffer) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
@@ -276,14 +276,14 @@ func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
 }
 
 // LinkAddressRequest implements stack.LinkAddressResolver.LinkAddressRequest.
-func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic stack.NetworkInterface) *tcpip.Error {
+func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic stack.NetworkInterface) tcpip.Error {
 	nicID := nic.ID()
 
 	p.mu.Lock()
 	netEP, ok := p.mu.eps[nicID]
 	p.mu.Unlock()
 	if !ok {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	stats := netEP.stats.arp
@@ -295,18 +295,18 @@ func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remot
 	if len(localAddr) == 0 {
 		addr, ok := p.stack.GetMainNICAddress(nicID, header.IPv4ProtocolNumber)
 		if !ok {
-			return tcpip.ErrUnknownNICID
+			return &tcpip.ErrUnknownNICID{}
 		}
 
 		if len(addr.Address) == 0 {
 			stats.outgoingRequestInterfaceHasNoLocalAddressErrors.Increment()
-			return tcpip.ErrNetworkUnreachable
+			return &tcpip.ErrNetworkUnreachable{}
 		}
 
 		localAddr = addr.Address
 	} else if p.stack.CheckLocalAddress(nicID, header.IPv4ProtocolNumber, localAddr) == 0 {
 		stats.outgoingRequestBadLocalAddressErrors.Increment()
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
@@ -345,13 +345,13 @@ func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bo
 }
 
 // SetOption implements stack.NetworkProtocol.SetOption.
-func (*protocol) SetOption(tcpip.SettableNetworkProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) SetOption(tcpip.SettableNetworkProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Option implements stack.NetworkProtocol.Option.
-func (*protocol) Option(tcpip.GettableNetworkProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) Option(tcpip.GettableNetworkProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Close implements stack.TransportProtocol.Close.
diff --git a/pkg/tcpip/network/arp/arp_test.go b/pkg/tcpip/network/arp/arp_test.go
index 6b23c0079..b0f07aa44 100644
--- a/pkg/tcpip/network/arp/arp_test.go
+++ b/pkg/tcpip/network/arp/arp_test.go
@@ -537,7 +537,7 @@ type testInterface struct {
 
 	nicID tcpip.NICID
 
-	writeErr *tcpip.Error
+	writeErr tcpip.Error
 }
 
 func (t *testInterface) ID() tcpip.NICID {
@@ -560,15 +560,15 @@ func (*testInterface) Promiscuous() bool {
 	return false
 }
 
-func (t *testInterface) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (t *testInterface) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	return t.LinkEndpoint.WritePacket(r.Fields(), gso, protocol, pkt)
 }
 
-func (t *testInterface) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (t *testInterface) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	return t.LinkEndpoint.WritePackets(r.Fields(), gso, pkts, protocol)
 }
 
-func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if t.writeErr != nil {
 		return t.writeErr
 	}
@@ -589,8 +589,8 @@ func TestLinkAddressRequest(t *testing.T) {
 		nicAddr                                         tcpip.Address
 		localAddr                                       tcpip.Address
 		remoteLinkAddr                                  tcpip.LinkAddress
-		linkErr                                         *tcpip.Error
-		expectedErr                                     *tcpip.Error
+		linkErr                                         tcpip.Error
+		expectedErr                                     tcpip.Error
 		expectedLocalAddr                               tcpip.Address
 		expectedRemoteLinkAddr                          tcpip.LinkAddress
 		expectedRequestsSent                            uint64
@@ -651,7 +651,7 @@ func TestLinkAddressRequest(t *testing.T) {
 			nicAddr:                              stackAddr,
 			localAddr:                            testAddr,
 			remoteLinkAddr:                       remoteLinkAddr,
-			expectedErr:                          tcpip.ErrBadLocalAddress,
+			expectedErr:                          &tcpip.ErrBadLocalAddress{},
 			expectedRequestsSent:                 0,
 			expectedRequestBadLocalAddressErrors: 1,
 			expectedRequestInterfaceHasNoLocalAddressErrors: 0,
@@ -662,7 +662,7 @@ func TestLinkAddressRequest(t *testing.T) {
 			nicAddr:                              stackAddr,
 			localAddr:                            testAddr,
 			remoteLinkAddr:                       "",
-			expectedErr:                          tcpip.ErrBadLocalAddress,
+			expectedErr:                          &tcpip.ErrBadLocalAddress{},
 			expectedRequestsSent:                 0,
 			expectedRequestBadLocalAddressErrors: 1,
 			expectedRequestInterfaceHasNoLocalAddressErrors: 0,
@@ -673,7 +673,7 @@ func TestLinkAddressRequest(t *testing.T) {
 			nicAddr:                              "",
 			localAddr:                            "",
 			remoteLinkAddr:                       remoteLinkAddr,
-			expectedErr:                          tcpip.ErrNetworkUnreachable,
+			expectedErr:                          &tcpip.ErrNetworkUnreachable{},
 			expectedRequestsSent:                 0,
 			expectedRequestBadLocalAddressErrors: 0,
 			expectedRequestInterfaceHasNoLocalAddressErrors: 1,
@@ -684,7 +684,7 @@ func TestLinkAddressRequest(t *testing.T) {
 			nicAddr:                              "",
 			localAddr:                            "",
 			remoteLinkAddr:                       "",
-			expectedErr:                          tcpip.ErrNetworkUnreachable,
+			expectedErr:                          &tcpip.ErrNetworkUnreachable{},
 			expectedRequestsSent:                 0,
 			expectedRequestBadLocalAddressErrors: 0,
 			expectedRequestInterfaceHasNoLocalAddressErrors: 1,
@@ -695,8 +695,8 @@ func TestLinkAddressRequest(t *testing.T) {
 			nicAddr:                              stackAddr,
 			localAddr:                            stackAddr,
 			remoteLinkAddr:                       remoteLinkAddr,
-			linkErr:                              tcpip.ErrInvalidEndpointState,
-			expectedErr:                          tcpip.ErrInvalidEndpointState,
+			linkErr:                              &tcpip.ErrInvalidEndpointState{},
+			expectedErr:                          &tcpip.ErrInvalidEndpointState{},
 			expectedRequestsSent:                 0,
 			expectedRequestBadLocalAddressErrors: 0,
 			expectedRequestInterfaceHasNoLocalAddressErrors: 0,
@@ -732,8 +732,9 @@ func TestLinkAddressRequest(t *testing.T) {
 			// link endpoint even though the stack uses the real NIC to validate the
 			// local address.
 			iface := testInterface{LinkEndpoint: linkEP, nicID: nicID, writeErr: test.linkErr}
-			if err := linkRes.LinkAddressRequest(remoteAddr, test.localAddr, test.remoteLinkAddr, &iface); err != test.expectedErr {
-				t.Fatalf("got p.LinkAddressRequest(%s, %s, %s, _) = %s, want = %s", remoteAddr, test.localAddr, test.remoteLinkAddr, err, test.expectedErr)
+			err := linkRes.LinkAddressRequest(remoteAddr, test.localAddr, test.remoteLinkAddr, &iface)
+			if diff := cmp.Diff(test.expectedErr, err); diff != "" {
+				t.Fatalf("unexpected error from p.LinkAddressRequest(%s, %s, %s, _), (-want, +got):\n%s", remoteAddr, test.localAddr, test.remoteLinkAddr, diff)
 			}
 
 			if got := s.Stats().ARP.OutgoingRequestsSent.Value(); got != test.expectedRequestsSent {
@@ -792,7 +793,8 @@ func TestLinkAddressRequestWithoutNIC(t *testing.T) {
 		t.Fatal("expected ARP protocol to implement stack.LinkAddressResolver")
 	}
 
-	if err := linkRes.LinkAddressRequest(remoteAddr, "", remoteLinkAddr, &testInterface{nicID: nicID}); err != tcpip.ErrNotConnected {
-		t.Fatalf("got p.LinkAddressRequest(%s, %s, %s, _) = %s, want = %s", remoteAddr, "", remoteLinkAddr, err, tcpip.ErrNotConnected)
+	err := linkRes.LinkAddressRequest(remoteAddr, "", remoteLinkAddr, &testInterface{nicID: nicID})
+	if _, ok := err.(*tcpip.ErrNotConnected); !ok {
+		t.Fatalf("got p.LinkAddressRequest(%s, %s, %s, _) = %s, want = %s", remoteAddr, "", remoteLinkAddr, err, &tcpip.ErrNotConnected{})
 	}
 }
diff --git a/pkg/tcpip/network/ip/generic_multicast_protocol.go b/pkg/tcpip/network/ip/generic_multicast_protocol.go
index f2f0e069c..a81f5c8c3 100644
--- a/pkg/tcpip/network/ip/generic_multicast_protocol.go
+++ b/pkg/tcpip/network/ip/generic_multicast_protocol.go
@@ -174,10 +174,10 @@ type MulticastGroupProtocol interface {
 	//
 	// Returns false if the caller should queue the report to be sent later. Note,
 	// returning false does not mean that the receiver hit an error.
-	SendReport(groupAddress tcpip.Address) (sent bool, err *tcpip.Error)
+	SendReport(groupAddress tcpip.Address) (sent bool, err tcpip.Error)
 
 	// SendLeave sends a multicast leave for the specified group address.
-	SendLeave(groupAddress tcpip.Address) *tcpip.Error
+	SendLeave(groupAddress tcpip.Address) tcpip.Error
 }
 
 // GenericMulticastProtocolState is the per interface generic multicast protocol
diff --git a/pkg/tcpip/network/ip/generic_multicast_protocol_test.go b/pkg/tcpip/network/ip/generic_multicast_protocol_test.go
index 85593f211..d5d5a449e 100644
--- a/pkg/tcpip/network/ip/generic_multicast_protocol_test.go
+++ b/pkg/tcpip/network/ip/generic_multicast_protocol_test.go
@@ -141,7 +141,7 @@ func (m *mockMulticastGroupProtocol) Enabled() bool {
 // SendReport implements ip.MulticastGroupProtocol.
 //
 // Precondition: m.mu must be locked.
-func (m *mockMulticastGroupProtocol) SendReport(groupAddress tcpip.Address) (bool, *tcpip.Error) {
+func (m *mockMulticastGroupProtocol) SendReport(groupAddress tcpip.Address) (bool, tcpip.Error) {
 	if m.mu.TryLock() {
 		m.mu.Unlock()
 		m.t.Fatalf("got write lock, expected to not take the lock; generic multicast protocol must take the write lock before sending report for %s", groupAddress)
@@ -158,7 +158,7 @@ func (m *mockMulticastGroupProtocol) SendReport(groupAddress tcpip.Address) (boo
 // SendLeave implements ip.MulticastGroupProtocol.
 //
 // Precondition: m.mu must be locked.
-func (m *mockMulticastGroupProtocol) SendLeave(groupAddress tcpip.Address) *tcpip.Error {
+func (m *mockMulticastGroupProtocol) SendLeave(groupAddress tcpip.Address) tcpip.Error {
 	if m.mu.TryLock() {
 		m.mu.Unlock()
 		m.t.Fatalf("got write lock, expected to not take the lock; generic multicast protocol must take the write lock before sending leave for %s", groupAddress)
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index 2a6ec19dc..47cce79bb 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -18,6 +18,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
@@ -167,7 +168,7 @@ func (*testObject) Wait() {}
 // WritePacket is called by network endpoints after producing a packet and
 // writing it to the link endpoint. This is used by the test object to verify
 // that the produced packet is as expected.
-func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	var prot tcpip.TransportProtocolNumber
 	var srcAddr tcpip.Address
 	var dstAddr tcpip.Address
@@ -189,7 +190,7 @@ func (t *testObject) WritePacket(_ *stack.Route, _ *stack.GSO, protocol tcpip.Ne
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*testObject) WritePackets(_ *stack.Route, _ *stack.GSO, pkt stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (*testObject) WritePackets(_ *stack.Route, _ *stack.GSO, pkt stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
@@ -203,7 +204,7 @@ func (*testObject) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.Net
 	panic("not implemented")
 }
 
-func buildIPv4Route(local, remote tcpip.Address) (*stack.Route, *tcpip.Error) {
+func buildIPv4Route(local, remote tcpip.Address) (*stack.Route, tcpip.Error) {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{ipv4.NewProtocol},
 		TransportProtocols: []stack.TransportProtocolFactory{udp.NewProtocol, tcp.NewProtocol},
@@ -219,7 +220,7 @@ func buildIPv4Route(local, remote tcpip.Address) (*stack.Route, *tcpip.Error) {
 	return s.FindRoute(nicID, local, remote, ipv4.ProtocolNumber, false /* multicastLoop */)
 }
 
-func buildIPv6Route(local, remote tcpip.Address) (*stack.Route, *tcpip.Error) {
+func buildIPv6Route(local, remote tcpip.Address) (*stack.Route, tcpip.Error) {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocolFactory{ipv6.NewProtocol},
 		TransportProtocols: []stack.TransportProtocolFactory{udp.NewProtocol, tcp.NewProtocol},
@@ -306,8 +307,8 @@ func (t *testInterface) setEnabled(v bool) {
 	t.mu.disabled = !v
 }
 
-func (*testInterface) WritePacketToRemote(tcpip.LinkAddress, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*testInterface) WritePacketToRemote(tcpip.LinkAddress, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 func TestSourceAddressValidation(t *testing.T) {
@@ -479,8 +480,9 @@ func TestEnableWhenNICDisabled(t *testing.T) {
 			// Attempting to enable the endpoint while the NIC is disabled should
 			// fail.
 			nic.setEnabled(false)
-			if err := ep.Enable(); err != tcpip.ErrNotPermitted {
-				t.Fatalf("got ep.Enable() = %s, want = %s", err, tcpip.ErrNotPermitted)
+			err := ep.Enable()
+			if _, ok := err.(*tcpip.ErrNotPermitted); !ok {
+				t.Fatalf("got ep.Enable() = %s, want = %s", err, &tcpip.ErrNotPermitted{})
 			}
 			// ep should consider the NIC's enabled status when determining its own
 			// enabled status so we "enable" the NIC to read just the endpoint's
@@ -1122,7 +1124,7 @@ func TestWriteHeaderIncludedPacket(t *testing.T) {
 		remoteAddr   tcpip.Address
 		pktGen       func(*testing.T, tcpip.Address) buffer.VectorisedView
 		checker      func(*testing.T, *stack.PacketBuffer, tcpip.Address)
-		expectedErr  *tcpip.Error
+		expectedErr  tcpip.Error
 	}{
 		{
 			name:         "IPv4",
@@ -1187,7 +1189,7 @@ func TestWriteHeaderIncludedPacket(t *testing.T) {
 				ip.SetHeaderLength(header.IPv4MinimumSize - 1)
 				return hdr.View().ToVectorisedView()
 			},
-			expectedErr: tcpip.ErrMalformedHeader,
+			expectedErr: &tcpip.ErrMalformedHeader{},
 		},
 		{
 			name:         "IPv4 too small",
@@ -1205,7 +1207,7 @@ func TestWriteHeaderIncludedPacket(t *testing.T) {
 				})
 				return buffer.View(ip[:len(ip)-1]).ToVectorisedView()
 			},
-			expectedErr: tcpip.ErrMalformedHeader,
+			expectedErr: &tcpip.ErrMalformedHeader{},
 		},
 		{
 			name:         "IPv4 minimum size",
@@ -1465,7 +1467,7 @@ func TestWriteHeaderIncludedPacket(t *testing.T) {
 				})
 				return buffer.View(ip[:len(ip)-1]).ToVectorisedView()
 			},
-			expectedErr: tcpip.ErrMalformedHeader,
+			expectedErr: &tcpip.ErrMalformedHeader{},
 		},
 	}
 
@@ -1506,10 +1508,13 @@ func TestWriteHeaderIncludedPacket(t *testing.T) {
 					}
 					defer r.Release()
 
-					if err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
-						Data: test.pktGen(t, subTest.srcAddr),
-					})); err != test.expectedErr {
-						t.Fatalf("got r.WriteHeaderIncludedPacket(_) = %s, want = %s", err, test.expectedErr)
+					{
+						err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
+							Data: test.pktGen(t, subTest.srcAddr),
+						}))
+						if diff := cmp.Diff(test.expectedErr, err); diff != "" {
+							t.Fatalf("unexpected error from r.WriteHeaderIncludedPacket(_), (-want, +got):\n%s", diff)
+						}
 					}
 
 					if test.expectedErr != nil {
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index 6bb97c46a..3d93a2cd0 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -310,7 +310,7 @@ func (*icmpReasonParamProblem) isICMPReason() {}
 // the problematic packet. It incorporates as much of that packet as
 // possible as well as any error metadata as is available. returnError
 // expects pkt to hold a valid IPv4 packet as per the wire format.
-func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpip.Error {
+func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip.Error {
 	origIPHdr := header.IPv4(pkt.NetworkHeader().View())
 	origIPHdrSrc := origIPHdr.SourceAddress()
 	origIPHdrDst := origIPHdr.DestinationAddress()
@@ -376,7 +376,7 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi
 	netEP, ok := p.mu.eps[pkt.NICID]
 	p.mu.Unlock()
 	if !ok {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	sent := netEP.stats.icmp.packetsSent
diff --git a/pkg/tcpip/network/ipv4/igmp.go b/pkg/tcpip/network/ipv4/igmp.go
index 4550aacd6..4cd0b3256 100644
--- a/pkg/tcpip/network/ipv4/igmp.go
+++ b/pkg/tcpip/network/ipv4/igmp.go
@@ -103,7 +103,7 @@ func (igmp *igmpState) Enabled() bool {
 // SendReport implements ip.MulticastGroupProtocol.
 //
 // Precondition: igmp.ep.mu must be read locked.
-func (igmp *igmpState) SendReport(groupAddress tcpip.Address) (bool, *tcpip.Error) {
+func (igmp *igmpState) SendReport(groupAddress tcpip.Address) (bool, tcpip.Error) {
 	igmpType := header.IGMPv2MembershipReport
 	if igmp.v1Present() {
 		igmpType = header.IGMPv1MembershipReport
@@ -114,7 +114,7 @@ func (igmp *igmpState) SendReport(groupAddress tcpip.Address) (bool, *tcpip.Erro
 // SendLeave implements ip.MulticastGroupProtocol.
 //
 // Precondition: igmp.ep.mu must be read locked.
-func (igmp *igmpState) SendLeave(groupAddress tcpip.Address) *tcpip.Error {
+func (igmp *igmpState) SendLeave(groupAddress tcpip.Address) tcpip.Error {
 	// As per RFC 2236 Section 6, Page 8: "If the interface state says the
 	// Querier is running IGMPv1, this action SHOULD be skipped. If the flag
 	// saying we were the last host to report is cleared, this action MAY be
@@ -242,7 +242,7 @@ func (igmp *igmpState) handleMembershipReport(groupAddress tcpip.Address) {
 // writePacket assembles and sends an IGMP packet.
 //
 // Precondition: igmp.ep.mu must be read locked.
-func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip.Address, igmpType header.IGMPType) (bool, *tcpip.Error) {
+func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip.Address, igmpType header.IGMPType) (bool, tcpip.Error) {
 	igmpData := header.IGMP(buffer.NewView(header.IGMPReportMinimumSize))
 	igmpData.SetType(igmpType)
 	igmpData.SetGroupAddress(groupAddress)
@@ -293,7 +293,7 @@ func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip
 // messages.
 //
 // If the group already exists in the membership map, returns
-// tcpip.ErrDuplicateAddress.
+// *tcpip.ErrDuplicateAddress.
 //
 // Precondition: igmp.ep.mu must be locked.
 func (igmp *igmpState) joinGroup(groupAddress tcpip.Address) {
@@ -312,13 +312,13 @@ func (igmp *igmpState) isInGroup(groupAddress tcpip.Address) bool {
 // if required.
 //
 // Precondition: igmp.ep.mu must be locked.
-func (igmp *igmpState) leaveGroup(groupAddress tcpip.Address) *tcpip.Error {
+func (igmp *igmpState) leaveGroup(groupAddress tcpip.Address) tcpip.Error {
 	// LeaveGroup returns false only if the group was not joined.
 	if igmp.genericMulticastProtocol.LeaveGroupLocked(groupAddress) {
 		return nil
 	}
 
-	return tcpip.ErrBadLocalAddress
+	return &tcpip.ErrBadLocalAddress{}
 }
 
 // softLeaveAll leaves all groups from the perspective of IGMP, but remains
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index a05275a5b..e5c80699d 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -137,14 +137,14 @@ func (p *protocol) forgetEndpoint(nicID tcpip.NICID) {
 }
 
 // Enable implements stack.NetworkEndpoint.
-func (e *endpoint) Enable() *tcpip.Error {
+func (e *endpoint) Enable() tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	// If the NIC is not enabled, the endpoint can't do anything meaningful so
 	// don't enable the endpoint.
 	if !e.nic.Enabled() {
-		return tcpip.ErrNotPermitted
+		return &tcpip.ErrNotPermitted{}
 	}
 
 	// If the endpoint is already enabled, there is nothing for it to do.
@@ -212,7 +212,9 @@ func (e *endpoint) disableLocked() {
 	}
 
 	// The endpoint may have already left the multicast group.
-	if err := e.leaveGroupLocked(header.IPv4AllSystems); err != nil && err != tcpip.ErrBadLocalAddress {
+	switch err := e.leaveGroupLocked(header.IPv4AllSystems); err.(type) {
+	case nil, *tcpip.ErrBadLocalAddress:
+	default:
 		panic(fmt.Sprintf("unexpected error when leaving group = %s: %s", header.IPv4AllSystems, err))
 	}
 
@@ -221,7 +223,9 @@ func (e *endpoint) disableLocked() {
 	e.mu.igmp.softLeaveAll()
 
 	// The address may have already been removed.
-	if err := e.mu.addressableEndpointState.RemovePermanentAddress(ipv4BroadcastAddr.Address); err != nil && err != tcpip.ErrBadLocalAddress {
+	switch err := e.mu.addressableEndpointState.RemovePermanentAddress(ipv4BroadcastAddr.Address); err.(type) {
+	case nil, *tcpip.ErrBadLocalAddress:
+	default:
 		panic(fmt.Sprintf("unexpected error when removing address = %s: %s", ipv4BroadcastAddr.Address, err))
 	}
 
@@ -256,7 +260,7 @@ func (e *endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
 	return e.protocol.Number()
 }
 
-func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, options header.IPv4OptionsSerializer) *tcpip.Error {
+func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, options header.IPv4OptionsSerializer) tcpip.Error {
 	hdrLen := header.IPv4MinimumSize
 	var optLen int
 	if options != nil {
@@ -264,12 +268,12 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 	}
 	hdrLen += optLen
 	if hdrLen > header.IPv4MaximumHeaderSize {
-		return tcpip.ErrMessageTooLong
+		return &tcpip.ErrMessageTooLong{}
 	}
 	ip := header.IPv4(pkt.NetworkHeader().Push(hdrLen))
 	length := pkt.Size()
 	if length > math.MaxUint16 {
-		return tcpip.ErrMessageTooLong
+		return &tcpip.ErrMessageTooLong{}
 	}
 	// RFC 6864 section 4.3 mandates uniqueness of ID values for non-atomic
 	// datagrams. Since the DF bit is never being set here, all datagrams
@@ -294,7 +298,7 @@ func (e *endpoint) addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.Packet
 // fragment. It returns the number of fragments handled and the number of
 // fragments left to be processed. The IP header must already be present in the
 // original packet.
-func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
+func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
 	// Round the MTU down to align to 8 bytes.
 	fragmentPayloadSize := networkMTU &^ 7
 	networkHeader := header.IPv4(pkt.NetworkHeader().View())
@@ -314,7 +318,7 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	if err := e.addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* options */); err != nil {
 		return err
 	}
@@ -353,7 +357,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	return e.writePacket(r, gso, pkt, false /* headerIncluded */)
 }
 
-func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, headerIncluded bool) *tcpip.Error {
+func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, headerIncluded bool) tcpip.Error {
 	if r.Loop&stack.PacketLoop != 0 {
 		pkt := pkt.CloneToInbound()
 		if e.protocol.stack.ParsePacketBuffer(ProtocolNumber, pkt) == stack.ParsedOK {
@@ -377,7 +381,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 	}
 
 	if packetMustBeFragmented(pkt, networkMTU, gso) {
-		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 			// TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each
 			// fragment one by one using WritePacket() (current strategy) or if we
 			// want to create a PacketBufferList from the fragments and feed it to
@@ -398,7 +402,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	if r.Loop&stack.PacketLoop != 0 {
 		panic("multiple packets in local loop")
 	}
@@ -423,7 +427,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 			// Keep track of the packet that is about to be fragmented so it can be
 			// removed once the fragmentation is done.
 			originalPkt := pkt
-			if _, _, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+			if _, _, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 				// Modify the packet list in place with the new fragments.
 				pkts.InsertAfter(pkt, fragPkt)
 				pkt = fragPkt
@@ -488,22 +492,22 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 }
 
 // WriteHeaderIncludedPacket implements stack.NetworkEndpoint.
-func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) tcpip.Error {
 	// The packet already has an IP header, but there are a few required
 	// checks.
 	h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
 	if !ok {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 
 	hdrLen := header.IPv4(h).HeaderLength()
 	if hdrLen < header.IPv4MinimumSize {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 
 	h, ok = pkt.Data.PullUp(int(hdrLen))
 	if !ok {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 	ip := header.IPv4(h)
 
@@ -541,14 +545,14 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 	// wire format. We also want to check if the header's fields are valid before
 	// sending the packet.
 	if !parse.IPv4(pkt) || !header.IPv4(pkt.NetworkHeader().View()).IsValid(pktSize) {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 
 	return e.writePacket(r, nil /* gso */, pkt, true /* headerIncluded */)
 }
 
 // forwardPacket attempts to forward a packet to its final destination.
-func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	h := header.IPv4(pkt.NetworkHeader().View())
 	ttl := h.TTL()
 	if ttl == 0 {
@@ -568,7 +572,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error {
 		networkEndpoint.(*endpoint).handlePacket(pkt)
 		return nil
 	}
-	if err != tcpip.ErrBadAddress {
+	if _, ok := err.(*tcpip.ErrBadAddress); !ok {
 		return err
 	}
 
@@ -825,7 +829,7 @@ func (e *endpoint) Close() {
 }
 
 // AddAndAcquirePermanentAddress implements stack.AddressableEndpoint.
-func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, *tcpip.Error) {
+func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, tcpip.Error) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
@@ -837,7 +841,7 @@ func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, p
 }
 
 // RemovePermanentAddress implements stack.AddressableEndpoint.
-func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.mu.addressableEndpointState.RemovePermanentAddress(addr)
@@ -894,7 +898,7 @@ func (e *endpoint) PermanentAddresses() []tcpip.AddressWithPrefix {
 }
 
 // JoinGroup implements stack.GroupAddressableEndpoint.
-func (e *endpoint) JoinGroup(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) JoinGroup(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.joinGroupLocked(addr)
@@ -903,9 +907,9 @@ func (e *endpoint) JoinGroup(addr tcpip.Address) *tcpip.Error {
 // joinGroupLocked is like JoinGroup but with locking requirements.
 //
 // Precondition: e.mu must be locked.
-func (e *endpoint) joinGroupLocked(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) joinGroupLocked(addr tcpip.Address) tcpip.Error {
 	if !header.IsV4MulticastAddress(addr) {
-		return tcpip.ErrBadAddress
+		return &tcpip.ErrBadAddress{}
 	}
 
 	e.mu.igmp.joinGroup(addr)
@@ -913,7 +917,7 @@ func (e *endpoint) joinGroupLocked(addr tcpip.Address) *tcpip.Error {
 }
 
 // LeaveGroup implements stack.GroupAddressableEndpoint.
-func (e *endpoint) LeaveGroup(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) LeaveGroup(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.leaveGroupLocked(addr)
@@ -922,7 +926,7 @@ func (e *endpoint) LeaveGroup(addr tcpip.Address) *tcpip.Error {
 // leaveGroupLocked is like LeaveGroup but with locking requirements.
 //
 // Precondition: e.mu must be locked.
-func (e *endpoint) leaveGroupLocked(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) leaveGroupLocked(addr tcpip.Address) tcpip.Error {
 	return e.mu.igmp.leaveGroup(addr)
 }
 
@@ -995,24 +999,24 @@ func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 }
 
 // SetOption implements NetworkProtocol.SetOption.
-func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
+func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		p.SetDefaultTTL(uint8(*v))
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // Option implements NetworkProtocol.Option.
-func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
+func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		*v = tcpip.DefaultTTLOption(p.DefaultTTL())
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
@@ -1058,9 +1062,9 @@ func (p *protocol) SetForwarding(v bool) {
 
 // calculateNetworkMTU calculates the network-layer payload MTU based on the
 // link-layer payload mtu.
-func calculateNetworkMTU(linkMTU, networkHeaderSize uint32) (uint32, *tcpip.Error) {
+func calculateNetworkMTU(linkMTU, networkHeaderSize uint32) (uint32, tcpip.Error) {
 	if linkMTU < header.IPv4MinimumMTU {
-		return 0, tcpip.ErrInvalidEndpointState
+		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// As per RFC 791 section 3.1, an IPv4 header cannot exceed 60 bytes in
@@ -1068,7 +1072,7 @@ func calculateNetworkMTU(linkMTU, networkHeaderSize uint32) (uint32, *tcpip.Erro
 	//   The maximal internet header is 60 octets, and a typical internet header
 	//   is 20 octets, allowing a margin for headers of higher level protocols.
 	if networkHeaderSize > header.IPv4MaximumHeaderSize {
-		return 0, tcpip.ErrMalformedHeader
+		return 0, &tcpip.ErrMalformedHeader{}
 	}
 
 	networkMTU := linkMTU
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index dac7cbfd4..ed5899f0b 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -78,8 +78,11 @@ func TestExcludeBroadcast(t *testing.T) {
 		defer ep.Close()
 
 		// Cannot connect using a broadcast address as the source.
-		if err := ep.Connect(randomAddr); err != tcpip.ErrNoRoute {
-			t.Errorf("got ep.Connect(...) = %v, want = %v", err, tcpip.ErrNoRoute)
+		{
+			err := ep.Connect(randomAddr)
+			if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+				t.Errorf("got ep.Connect(...) = %v, want = %v", err, &tcpip.ErrNoRoute{})
+			}
 		}
 
 		// However, we can bind to a broadcast address to listen.
@@ -1376,8 +1379,8 @@ func TestFragmentationErrors(t *testing.T) {
 		payloadSize           int
 		allowPackets          int
 		outgoingErrors        int
-		mockError             *tcpip.Error
-		wantError             *tcpip.Error
+		mockError             tcpip.Error
+		wantError             tcpip.Error
 	}{
 		{
 			description:           "No frag",
@@ -1386,8 +1389,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transportHeaderLength: 0,
 			allowPackets:          0,
 			outgoingErrors:        1,
-			mockError:             tcpip.ErrAborted,
-			wantError:             tcpip.ErrAborted,
+			mockError:             &tcpip.ErrAborted{},
+			wantError:             &tcpip.ErrAborted{},
 		},
 		{
 			description:           "Error on first frag",
@@ -1396,8 +1399,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transportHeaderLength: 0,
 			allowPackets:          0,
 			outgoingErrors:        3,
-			mockError:             tcpip.ErrAborted,
-			wantError:             tcpip.ErrAborted,
+			mockError:             &tcpip.ErrAborted{},
+			wantError:             &tcpip.ErrAborted{},
 		},
 		{
 			description:           "Error on second frag",
@@ -1406,8 +1409,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transportHeaderLength: 0,
 			allowPackets:          1,
 			outgoingErrors:        2,
-			mockError:             tcpip.ErrAborted,
-			wantError:             tcpip.ErrAborted,
+			mockError:             &tcpip.ErrAborted{},
+			wantError:             &tcpip.ErrAborted{},
 		},
 		{
 			description:           "Error on first frag MTU smaller than header",
@@ -1416,8 +1419,8 @@ func TestFragmentationErrors(t *testing.T) {
 			payloadSize:           500,
 			allowPackets:          0,
 			outgoingErrors:        4,
-			mockError:             tcpip.ErrAborted,
-			wantError:             tcpip.ErrAborted,
+			mockError:             &tcpip.ErrAborted{},
+			wantError:             &tcpip.ErrAborted{},
 		},
 		{
 			description:           "Error when MTU is smaller than IPv4 minimum MTU",
@@ -1427,7 +1430,7 @@ func TestFragmentationErrors(t *testing.T) {
 			allowPackets:          0,
 			outgoingErrors:        1,
 			mockError:             nil,
-			wantError:             tcpip.ErrInvalidEndpointState,
+			wantError:             &tcpip.ErrInvalidEndpointState{},
 		},
 	}
 
@@ -1441,8 +1444,8 @@ func TestFragmentationErrors(t *testing.T) {
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
 			}, pkt)
-			if err != ft.wantError {
-				t.Errorf("got WritePacket(_, _, _) = %s, want = %s", err, ft.wantError)
+			if diff := cmp.Diff(ft.wantError, err); diff != "" {
+				t.Fatalf("unexpected error from r.WritePacket(_, _, _), (-want, +got):\n%s", diff)
 			}
 			if got := int(r.Stats().IP.PacketsSent.Value()); got != ft.allowPackets {
 				t.Errorf("got r.Stats().IP.PacketsSent.Value() = %d, want = %d", got, ft.allowPackets)
@@ -2475,8 +2478,9 @@ func TestReceiveFragments(t *testing.T) {
 				}
 			}
 
-			if res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{}); err != tcpip.ErrWouldBlock {
-				t.Fatalf("(last) got Read = (%v, %v), want = (_, %s)", res, err, tcpip.ErrWouldBlock)
+			res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{})
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				t.Fatalf("(last) got Read = (%#v, %v), want = (_, %s)", res, err, &tcpip.ErrWouldBlock{})
 			}
 		})
 	}
@@ -2554,11 +2558,11 @@ func TestWriteStats(t *testing.T) {
 	// Parameterize the tests to run with both WritePacket and WritePackets.
 	writers := []struct {
 		name         string
-		writePackets func(*stack.Route, stack.PacketBufferList) (int, *tcpip.Error)
+		writePackets func(*stack.Route, stack.PacketBufferList) (int, tcpip.Error)
 	}{
 		{
 			name: "WritePacket",
-			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, *tcpip.Error) {
+			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				nWritten := 0
 				for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 					if err := rt.WritePacket(nil, stack.NetworkHeaderParams{}, pkt); err != nil {
@@ -2570,7 +2574,7 @@ func TestWriteStats(t *testing.T) {
 			},
 		}, {
 			name: "WritePackets",
-			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, *tcpip.Error) {
+			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				return rt.WritePackets(nil, pkts, stack.NetworkHeaderParams{})
 			},
 		},
@@ -2580,7 +2584,7 @@ func TestWriteStats(t *testing.T) {
 		t.Run(writer.name, func(t *testing.T) {
 			for _, test := range tests {
 				t.Run(test.name, func(t *testing.T) {
-					ep := testutil.NewMockLinkEndpoint(header.IPv4MinimumMTU, tcpip.ErrInvalidEndpointState, test.allowPackets)
+					ep := testutil.NewMockLinkEndpoint(header.IPv4MinimumMTU, &tcpip.ErrInvalidEndpointState{}, test.allowPackets)
 					rt := buildRoute(t, ep)
 
 					var pkts stack.PacketBufferList
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 95efada3a..43f8a825e 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -237,7 +237,9 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool) {
 				//
 				// TODO(gvisor.dev/issue/4046): Handle the scenario when a duplicate
 				// address is detected for an assigned address.
-				if err := e.dupTentativeAddrDetected(targetAddr); err != nil && err != tcpip.ErrBadAddress && err != tcpip.ErrInvalidEndpointState {
+				switch err := e.dupTentativeAddrDetected(targetAddr); err.(type) {
+				case nil, *tcpip.ErrBadAddress, *tcpip.ErrInvalidEndpointState:
+				default:
 					panic(fmt.Sprintf("unexpected error handling duplicate tentative address: %s", err))
 				}
 			}
@@ -413,10 +415,12 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer, hasFragmentHeader bool) {
 			//
 			// TODO(gvisor.dev/issue/4046): Handle the scenario when a duplicate
 			// address is detected for an assigned address.
-			if err := e.dupTentativeAddrDetected(targetAddr); err != nil && err != tcpip.ErrBadAddress && err != tcpip.ErrInvalidEndpointState {
+			switch err := e.dupTentativeAddrDetected(targetAddr); err.(type) {
+			case nil, *tcpip.ErrBadAddress, *tcpip.ErrInvalidEndpointState:
+				return
+			default:
 				panic(fmt.Sprintf("unexpected error handling duplicate tentative address: %s", err))
 			}
-			return
 		}
 
 		it, err := na.Options().Iter(false /* check */)
@@ -687,14 +691,14 @@ func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
 }
 
 // LinkAddressRequest implements stack.LinkAddressResolver.
-func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic stack.NetworkInterface) *tcpip.Error {
+func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic stack.NetworkInterface) tcpip.Error {
 	nicID := nic.ID()
 
 	p.mu.Lock()
 	netEP, ok := p.mu.eps[nicID]
 	p.mu.Unlock()
 	if !ok {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	remoteAddr := targetAddr
@@ -706,12 +710,12 @@ func (p *protocol) LinkAddressRequest(targetAddr, localAddr tcpip.Address, remot
 	if len(localAddr) == 0 {
 		addressEndpoint := netEP.AcquireOutgoingPrimaryAddress(remoteAddr, false /* allowExpired */)
 		if addressEndpoint == nil {
-			return tcpip.ErrNetworkUnreachable
+			return &tcpip.ErrNetworkUnreachable{}
 		}
 
 		localAddr = addressEndpoint.AddressWithPrefix().Address
 	} else if p.stack.CheckLocalAddress(nicID, ProtocolNumber, localAddr) == 0 {
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	optsSerializer := header.NDPOptionsSerializer{
@@ -813,7 +817,7 @@ func (*icmpReasonReassemblyTimeout) isICMPReason() {}
 
 // returnError takes an error descriptor and generates the appropriate ICMP
 // error packet for IPv6 and sends it.
-func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpip.Error {
+func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip.Error {
 	origIPHdr := header.IPv6(pkt.NetworkHeader().View())
 	origIPHdrSrc := origIPHdr.SourceAddress()
 	origIPHdrDst := origIPHdr.DestinationAddress()
@@ -884,7 +888,7 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi
 	netEP, ok := p.mu.eps[pkt.NICID]
 	p.mu.Unlock()
 	if !ok {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	sent := netEP.stats.icmp.packetsSent
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 641c60b7c..db1c2e663 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -79,7 +79,7 @@ func (*stubLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return ""
 }
 
-func (*stubLinkEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) *tcpip.Error {
+func (*stubLinkEndpoint) WritePacket(stack.RouteInfo, *stack.GSO, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) tcpip.Error {
 	return nil
 }
 
@@ -145,15 +145,15 @@ func (*testInterface) Promiscuous() bool {
 	return false
 }
 
-func (t *testInterface) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (t *testInterface) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	return t.LinkEndpoint.WritePacket(r.Fields(), gso, protocol, pkt)
 }
 
-func (t *testInterface) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (t *testInterface) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	return t.LinkEndpoint.WritePackets(r.Fields(), gso, pkts, protocol)
 }
 
-func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (t *testInterface) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	var r stack.RouteInfo
 	r.NetProto = protocol
 	r.RemoteLinkAddress = remoteLinkAddr
@@ -1283,7 +1283,7 @@ func TestLinkAddressRequest(t *testing.T) {
 		localAddr      tcpip.Address
 		remoteLinkAddr tcpip.LinkAddress
 
-		expectedErr            *tcpip.Error
+		expectedErr            tcpip.Error
 		expectedRemoteAddr     tcpip.Address
 		expectedRemoteLinkAddr tcpip.LinkAddress
 	}{
@@ -1321,23 +1321,23 @@ func TestLinkAddressRequest(t *testing.T) {
 			name:           "Unicast with unassigned address",
 			localAddr:      lladdr1,
 			remoteLinkAddr: linkAddr1,
-			expectedErr:    tcpip.ErrBadLocalAddress,
+			expectedErr:    &tcpip.ErrBadLocalAddress{},
 		},
 		{
 			name:           "Multicast with unassigned address",
 			localAddr:      lladdr1,
 			remoteLinkAddr: "",
-			expectedErr:    tcpip.ErrBadLocalAddress,
+			expectedErr:    &tcpip.ErrBadLocalAddress{},
 		},
 		{
 			name:           "Unicast with no local address available",
 			remoteLinkAddr: linkAddr1,
-			expectedErr:    tcpip.ErrNetworkUnreachable,
+			expectedErr:    &tcpip.ErrNetworkUnreachable{},
 		},
 		{
 			name:           "Multicast with no local address available",
 			remoteLinkAddr: "",
-			expectedErr:    tcpip.ErrNetworkUnreachable,
+			expectedErr:    &tcpip.ErrNetworkUnreachable{},
 		},
 	}
 
@@ -1366,8 +1366,9 @@ func TestLinkAddressRequest(t *testing.T) {
 			// ID and link endpoint used by the NIC we created earlier so that we can
 			// mock a link address request and observe the packets sent to the link
 			// endpoint even though the stack uses the real NIC.
-			if err := linkRes.LinkAddressRequest(lladdr0, test.localAddr, test.remoteLinkAddr, &testInterface{LinkEndpoint: linkEP, nicID: nicID}); err != test.expectedErr {
-				t.Errorf("got p.LinkAddressRequest(%s, %s, %s, _) = %s, want = %s", lladdr0, test.localAddr, test.remoteLinkAddr, err, test.expectedErr)
+			err := linkRes.LinkAddressRequest(lladdr0, test.localAddr, test.remoteLinkAddr, &testInterface{LinkEndpoint: linkEP, nicID: nicID})
+			if diff := cmp.Diff(test.expectedErr, err); diff != "" {
+				t.Fatalf("unexpected error from p.LinkAddressRequest(%s, %s, %s, _), (-want, +got):\n%s", lladdr0, test.localAddr, test.remoteLinkAddr, diff)
 			}
 
 			if test.expectedErr != nil {
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index d658f9bcb..94043ed4e 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -307,17 +307,17 @@ func (e *endpoint) hasTentativeAddr(addr tcpip.Address) bool {
 // dupTentativeAddrDetected removes the tentative address if it exists. If the
 // address was generated via SLAAC, an attempt is made to generate a new
 // address.
-func (e *endpoint) dupTentativeAddrDetected(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) dupTentativeAddrDetected(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	addressEndpoint := e.getAddressRLocked(addr)
 	if addressEndpoint == nil {
-		return tcpip.ErrBadAddress
+		return &tcpip.ErrBadAddress{}
 	}
 
 	if addressEndpoint.GetKind() != stack.PermanentTentative {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// If the address is a SLAAC address, do not invalidate its SLAAC prefix as an
@@ -369,14 +369,14 @@ func (e *endpoint) transitionForwarding(forwarding bool) {
 }
 
 // Enable implements stack.NetworkEndpoint.
-func (e *endpoint) Enable() *tcpip.Error {
+func (e *endpoint) Enable() tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	// If the NIC is not enabled, the endpoint can't do anything meaningful so
 	// don't enable the endpoint.
 	if !e.nic.Enabled() {
-		return tcpip.ErrNotPermitted
+		return &tcpip.ErrNotPermitted{}
 	}
 
 	// If the endpoint is already enabled, there is nothing for it to do.
@@ -418,7 +418,7 @@ func (e *endpoint) Enable() *tcpip.Error {
 	//
 	// Addresses may have aleady completed DAD but in the time since the endpoint
 	// was last enabled, other devices may have acquired the same addresses.
-	var err *tcpip.Error
+	var err tcpip.Error
 	e.mu.addressableEndpointState.ForEachEndpoint(func(addressEndpoint stack.AddressEndpoint) bool {
 		addr := addressEndpoint.AddressWithPrefix().Address
 		if !header.IsV6UnicastAddress(addr) {
@@ -499,7 +499,9 @@ func (e *endpoint) disableLocked() {
 	e.stopDADForPermanentAddressesLocked()
 
 	// The endpoint may have already left the multicast group.
-	if err := e.leaveGroupLocked(header.IPv6AllNodesMulticastAddress); err != nil && err != tcpip.ErrBadLocalAddress {
+	switch err := e.leaveGroupLocked(header.IPv6AllNodesMulticastAddress); err.(type) {
+	case nil, *tcpip.ErrBadLocalAddress:
+	default:
 		panic(fmt.Sprintf("unexpected error when leaving group = %s: %s", header.IPv6AllNodesMulticastAddress, err))
 	}
 
@@ -555,11 +557,11 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 	return e.nic.MaxHeaderLength() + header.IPv6MinimumSize
 }
 
-func addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, extensionHeaders header.IPv6ExtHdrSerializer) *tcpip.Error {
+func addIPHeader(srcAddr, dstAddr tcpip.Address, pkt *stack.PacketBuffer, params stack.NetworkHeaderParams, extensionHeaders header.IPv6ExtHdrSerializer) tcpip.Error {
 	extHdrsLen := extensionHeaders.Length()
 	length := pkt.Size() + extensionHeaders.Length()
 	if length > math.MaxUint16 {
-		return tcpip.ErrMessageTooLong
+		return &tcpip.ErrMessageTooLong{}
 	}
 	ip := header.IPv6(pkt.NetworkHeader().Push(header.IPv6MinimumSize + extHdrsLen))
 	ip.Encode(&header.IPv6Fields{
@@ -585,7 +587,7 @@ func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *sta
 // fragments left to be processed. The IP header must already be present in the
 // original packet. The transport header protocol number is required to avoid
 // parsing the IPv6 extension headers.
-func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
+func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) tcpip.Error) (int, int, tcpip.Error) {
 	networkHeader := header.IPv6(pkt.NetworkHeader().View())
 
 	// TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are
@@ -598,13 +600,13 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 		// of 8 as per RFC 8200 section 4.5:
 		//   Each complete fragment, except possibly the last ("rightmost") one, is
 		//   an integer multiple of 8 octets long.
-		return 0, 1, tcpip.ErrMessageTooLong
+		return 0, 1, &tcpip.ErrMessageTooLong{}
 	}
 
 	if fragmentPayloadLen < uint32(pkt.TransportHeader().View().Size()) {
 		// As per RFC 8200 Section 4.5, the Transport Header is expected to be small
 		// enough to fit in the first fragment.
-		return 0, 1, tcpip.ErrMessageTooLong
+		return 0, 1, &tcpip.ErrMessageTooLong{}
 	}
 
 	pf := fragmentation.MakePacketFragmenter(pkt, fragmentPayloadLen, calculateFragmentReserve(pkt))
@@ -624,7 +626,7 @@ func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU ui
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	if err := addIPHeader(r.LocalAddress, r.RemoteAddress, pkt, params, nil /* extensionHeaders */); err != nil {
 		return err
 	}
@@ -662,7 +664,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	return e.writePacket(r, gso, pkt, params.Protocol, false /* headerIncluded */)
 }
 
-func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, protocol tcpip.TransportProtocolNumber, headerIncluded bool) *tcpip.Error {
+func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.PacketBuffer, protocol tcpip.TransportProtocolNumber, headerIncluded bool) tcpip.Error {
 	if r.Loop&stack.PacketLoop != 0 {
 		pkt := pkt.CloneToInbound()
 		if e.protocol.stack.ParsePacketBuffer(ProtocolNumber, pkt) == stack.ParsedOK {
@@ -685,7 +687,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 	}
 
 	if packetMustBeFragmented(pkt, networkMTU, gso) {
-		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+		sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 			// TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each
 			// fragment one by one using WritePacket() (current strategy) or if we
 			// want to create a PacketBufferList from the fragments and feed it to
@@ -707,7 +709,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
 }
 
 // WritePackets implements stack.NetworkEndpoint.WritePackets.
-func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, *tcpip.Error) {
+func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	if r.Loop&stack.PacketLoop != 0 {
 		panic("not implemented")
 	}
@@ -731,7 +733,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 			// Keep track of the packet that is about to be fragmented so it can be
 			// removed once the fragmentation is done.
 			originalPkt := pb
-			if _, _, err := e.handleFragments(r, gso, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+			if _, _, err := e.handleFragments(r, gso, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) tcpip.Error {
 				// Modify the packet list in place with the new fragments.
 				pkts.InsertAfter(pb, fragPkt)
 				pb = fragPkt
@@ -798,11 +800,11 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 }
 
 // WriteHeaderIncludedPacket implements stack.NetworkEndpoint.
-func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) tcpip.Error {
 	// The packet already has an IP header, but there are a few required checks.
 	h, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
 	if !ok {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 	ip := header.IPv6(h)
 
@@ -827,14 +829,14 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 	// sending the packet.
 	proto, _, _, _, ok := parse.IPv6(pkt)
 	if !ok || !header.IPv6(pkt.NetworkHeader().View()).IsValid(pktSize) {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 
 	return e.writePacket(r, nil /* gso */, pkt, proto, true /* headerIncluded */)
 }
 
 // forwardPacket attempts to forward a packet to its final destination.
-func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error {
+func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	h := header.IPv6(pkt.NetworkHeader().View())
 	hopLimit := h.HopLimit()
 	if hopLimit <= 1 {
@@ -856,7 +858,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error {
 		networkEndpoint.(*endpoint).handlePacket(pkt)
 		return nil
 	}
-	if err != tcpip.ErrBadAddress {
+	if _, ok := err.(*tcpip.ErrBadAddress); !ok {
 		return err
 	}
 
@@ -1330,7 +1332,7 @@ func (e *endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
 }
 
 // AddAndAcquirePermanentAddress implements stack.AddressableEndpoint.
-func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, *tcpip.Error) {
+func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, tcpip.Error) {
 	// TODO(b/169350103): add checks here after making sure we no longer receive
 	// an empty address.
 	e.mu.Lock()
@@ -1345,7 +1347,7 @@ func (e *endpoint) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, p
 // solicited-node multicast group and start duplicate address detection.
 //
 // Precondition: e.mu must be write locked.
-func (e *endpoint) addAndAcquirePermanentAddressLocked(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, *tcpip.Error) {
+func (e *endpoint) addAndAcquirePermanentAddressLocked(addr tcpip.AddressWithPrefix, peb stack.PrimaryEndpointBehavior, configType stack.AddressConfigType, deprecated bool) (stack.AddressEndpoint, tcpip.Error) {
 	addressEndpoint, err := e.mu.addressableEndpointState.AddAndAcquirePermanentAddress(addr, peb, configType, deprecated)
 	if err != nil {
 		return nil, err
@@ -1374,13 +1376,13 @@ func (e *endpoint) addAndAcquirePermanentAddressLocked(addr tcpip.AddressWithPre
 }
 
 // RemovePermanentAddress implements stack.AddressableEndpoint.
-func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	addressEndpoint := e.getAddressRLocked(addr)
 	if addressEndpoint == nil || !addressEndpoint.GetKind().IsPermanent() {
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	return e.removePermanentEndpointLocked(addressEndpoint, true)
@@ -1390,7 +1392,7 @@ func (e *endpoint) RemovePermanentAddress(addr tcpip.Address) *tcpip.Error {
 // it works with a stack.AddressEndpoint.
 //
 // Precondition: e.mu must be write locked.
-func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEndpoint, allowSLAACInvalidation bool) *tcpip.Error {
+func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEndpoint, allowSLAACInvalidation bool) tcpip.Error {
 	addr := addressEndpoint.AddressWithPrefix()
 	unicast := header.IsV6UnicastAddress(addr.Address)
 	if unicast {
@@ -1415,12 +1417,12 @@ func (e *endpoint) removePermanentEndpointLocked(addressEndpoint stack.AddressEn
 	}
 
 	snmc := header.SolicitedNodeAddr(addr.Address)
+	err := e.leaveGroupLocked(snmc)
 	// The endpoint may have already left the multicast group.
-	if err := e.leaveGroupLocked(snmc); err != nil && err != tcpip.ErrBadLocalAddress {
-		return err
+	if _, ok := err.(*tcpip.ErrBadLocalAddress); ok {
+		err = nil
 	}
-
-	return nil
+	return err
 }
 
 // hasPermanentAddressLocked returns true if the endpoint has a permanent
@@ -1630,7 +1632,7 @@ func (e *endpoint) PermanentAddresses() []tcpip.AddressWithPrefix {
 }
 
 // JoinGroup implements stack.GroupAddressableEndpoint.
-func (e *endpoint) JoinGroup(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) JoinGroup(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.joinGroupLocked(addr)
@@ -1639,9 +1641,9 @@ func (e *endpoint) JoinGroup(addr tcpip.Address) *tcpip.Error {
 // joinGroupLocked is like JoinGroup but with locking requirements.
 //
 // Precondition: e.mu must be locked.
-func (e *endpoint) joinGroupLocked(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) joinGroupLocked(addr tcpip.Address) tcpip.Error {
 	if !header.IsV6MulticastAddress(addr) {
-		return tcpip.ErrBadAddress
+		return &tcpip.ErrBadAddress{}
 	}
 
 	e.mu.mld.joinGroup(addr)
@@ -1649,7 +1651,7 @@ func (e *endpoint) joinGroupLocked(addr tcpip.Address) *tcpip.Error {
 }
 
 // LeaveGroup implements stack.GroupAddressableEndpoint.
-func (e *endpoint) LeaveGroup(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) LeaveGroup(addr tcpip.Address) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	return e.leaveGroupLocked(addr)
@@ -1658,7 +1660,7 @@ func (e *endpoint) LeaveGroup(addr tcpip.Address) *tcpip.Error {
 // leaveGroupLocked is like LeaveGroup but with locking requirements.
 //
 // Precondition: e.mu must be locked.
-func (e *endpoint) leaveGroupLocked(addr tcpip.Address) *tcpip.Error {
+func (e *endpoint) leaveGroupLocked(addr tcpip.Address) tcpip.Error {
 	return e.mu.mld.leaveGroup(addr)
 }
 
@@ -1762,24 +1764,24 @@ func (p *protocol) forgetEndpoint(nicID tcpip.NICID) {
 }
 
 // SetOption implements NetworkProtocol.SetOption.
-func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
+func (p *protocol) SetOption(option tcpip.SettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		p.SetDefaultTTL(uint8(*v))
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // Option implements NetworkProtocol.Option.
-func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
+func (p *protocol) Option(option tcpip.GettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		*v = tcpip.DefaultTTLOption(p.DefaultTTL())
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
@@ -1842,9 +1844,9 @@ func (p *protocol) SetForwarding(v bool) {
 // link-layer payload MTU and the length of every IPv6 header.
 // Note that this is different than the Payload Length field of the IPv6 header,
 // which includes the length of the extension headers.
-func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, *tcpip.Error) {
+func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, tcpip.Error) {
 	if linkMTU < header.IPv6MinimumMTU {
-		return 0, tcpip.ErrInvalidEndpointState
+		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// As per RFC 7112 section 5, we should discard packets if their IPv6 header
@@ -1855,7 +1857,7 @@ func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, *tcpip.Erro
 	//   bytes ensures that the header chain length does not exceed the IPv6
 	//   minimum MTU.
 	if networkHeadersLen > header.IPv6MinimumMTU {
-		return 0, tcpip.ErrMalformedHeader
+		return 0, &tcpip.ErrMalformedHeader{}
 	}
 
 	networkMTU := linkMTU - uint32(networkHeadersLen)
diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go
index 5276878a0..8248052a3 100644
--- a/pkg/tcpip/network/ipv6/ipv6_test.go
+++ b/pkg/tcpip/network/ipv6/ipv6_test.go
@@ -996,8 +996,9 @@ func TestReceiveIPv6ExtHdrs(t *testing.T) {
 			}
 
 			// Should not have any more UDP packets.
-			if res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{}); err != tcpip.ErrWouldBlock {
-				t.Fatalf("got Read = (%v, %v), want = (_, %s)", res, err, tcpip.ErrWouldBlock)
+			res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{})
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				t.Fatalf("got Read = (%v, %v), want = (_, %s)", res, err, &tcpip.ErrWouldBlock{})
 			}
 		})
 	}
@@ -1988,8 +1989,9 @@ func TestReceiveIPv6Fragments(t *testing.T) {
 				}
 			}
 
-			if res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{}); err != tcpip.ErrWouldBlock {
-				t.Fatalf("(last) got Read = (%v, %v), want = (_, %s)", res, err, tcpip.ErrWouldBlock)
+			res, err := ep.Read(ioutil.Discard, tcpip.ReadOptions{})
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				t.Fatalf("(last) got Read = (%v, %v), want = (_, %s)", res, err, &tcpip.ErrWouldBlock{})
 			}
 		})
 	}
@@ -2472,11 +2474,11 @@ func TestWriteStats(t *testing.T) {
 
 	writers := []struct {
 		name         string
-		writePackets func(*stack.Route, stack.PacketBufferList) (int, *tcpip.Error)
+		writePackets func(*stack.Route, stack.PacketBufferList) (int, tcpip.Error)
 	}{
 		{
 			name: "WritePacket",
-			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, *tcpip.Error) {
+			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				nWritten := 0
 				for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 					if err := rt.WritePacket(nil, stack.NetworkHeaderParams{}, pkt); err != nil {
@@ -2488,7 +2490,7 @@ func TestWriteStats(t *testing.T) {
 			},
 		}, {
 			name: "WritePackets",
-			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, *tcpip.Error) {
+			writePackets: func(rt *stack.Route, pkts stack.PacketBufferList) (int, tcpip.Error) {
 				return rt.WritePackets(nil, pkts, stack.NetworkHeaderParams{})
 			},
 		},
@@ -2498,7 +2500,7 @@ func TestWriteStats(t *testing.T) {
 		t.Run(writer.name, func(t *testing.T) {
 			for _, test := range tests {
 				t.Run(test.name, func(t *testing.T) {
-					ep := testutil.NewMockLinkEndpoint(header.IPv6MinimumMTU, tcpip.ErrInvalidEndpointState, test.allowPackets)
+					ep := testutil.NewMockLinkEndpoint(header.IPv6MinimumMTU, &tcpip.ErrInvalidEndpointState{}, test.allowPackets)
 					rt := buildRoute(t, ep)
 					var pkts stack.PacketBufferList
 					for i := 0; i < nPackets; i++ {
@@ -2832,8 +2834,8 @@ func TestFragmentationErrors(t *testing.T) {
 		payloadSize    int
 		allowPackets   int
 		outgoingErrors int
-		mockError      *tcpip.Error
-		wantError      *tcpip.Error
+		mockError      tcpip.Error
+		wantError      tcpip.Error
 	}{
 		{
 			description:    "No frag",
@@ -2842,8 +2844,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transHdrLen:    0,
 			allowPackets:   0,
 			outgoingErrors: 1,
-			mockError:      tcpip.ErrAborted,
-			wantError:      tcpip.ErrAborted,
+			mockError:      &tcpip.ErrAborted{},
+			wantError:      &tcpip.ErrAborted{},
 		},
 		{
 			description:    "Error on first frag",
@@ -2852,8 +2854,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transHdrLen:    0,
 			allowPackets:   0,
 			outgoingErrors: 3,
-			mockError:      tcpip.ErrAborted,
-			wantError:      tcpip.ErrAborted,
+			mockError:      &tcpip.ErrAborted{},
+			wantError:      &tcpip.ErrAborted{},
 		},
 		{
 			description:    "Error on second frag",
@@ -2862,8 +2864,8 @@ func TestFragmentationErrors(t *testing.T) {
 			transHdrLen:    0,
 			allowPackets:   1,
 			outgoingErrors: 2,
-			mockError:      tcpip.ErrAborted,
-			wantError:      tcpip.ErrAborted,
+			mockError:      &tcpip.ErrAborted{},
+			wantError:      &tcpip.ErrAborted{},
 		},
 		{
 			description:    "Error when MTU is smaller than transport header",
@@ -2873,7 +2875,7 @@ func TestFragmentationErrors(t *testing.T) {
 			allowPackets:   0,
 			outgoingErrors: 1,
 			mockError:      nil,
-			wantError:      tcpip.ErrMessageTooLong,
+			wantError:      &tcpip.ErrMessageTooLong{},
 		},
 		{
 			description:    "Error when MTU is smaller than IPv6 minimum MTU",
@@ -2883,7 +2885,7 @@ func TestFragmentationErrors(t *testing.T) {
 			allowPackets:   0,
 			outgoingErrors: 1,
 			mockError:      nil,
-			wantError:      tcpip.ErrInvalidEndpointState,
+			wantError:      &tcpip.ErrInvalidEndpointState{},
 		},
 	}
 
@@ -2897,8 +2899,8 @@ func TestFragmentationErrors(t *testing.T) {
 				TTL:      ttl,
 				TOS:      stack.DefaultTOS,
 			}, pkt)
-			if err != ft.wantError {
-				t.Errorf("got WritePacket(_, _, _) = %s, want = %s", err, ft.wantError)
+			if diff := cmp.Diff(ft.wantError, err); diff != "" {
+				t.Errorf("unexpected error from WritePacket(_, _, _), (-want, +got):\n%s", diff)
 			}
 			if got := int(r.Stats().IP.PacketsSent.Value()); got != ft.allowPackets {
 				t.Errorf("got r.Stats().IP.PacketsSent.Value() = %d, want = %d", got, ft.allowPackets)
diff --git a/pkg/tcpip/network/ipv6/mld.go b/pkg/tcpip/network/ipv6/mld.go
index c376016e9..2cc0dfebd 100644
--- a/pkg/tcpip/network/ipv6/mld.go
+++ b/pkg/tcpip/network/ipv6/mld.go
@@ -68,14 +68,14 @@ func (mld *mldState) Enabled() bool {
 // SendReport implements ip.MulticastGroupProtocol.
 //
 // Precondition: mld.ep.mu must be read locked.
-func (mld *mldState) SendReport(groupAddress tcpip.Address) (bool, *tcpip.Error) {
+func (mld *mldState) SendReport(groupAddress tcpip.Address) (bool, tcpip.Error) {
 	return mld.writePacket(groupAddress, groupAddress, header.ICMPv6MulticastListenerReport)
 }
 
 // SendLeave implements ip.MulticastGroupProtocol.
 //
 // Precondition: mld.ep.mu must be read locked.
-func (mld *mldState) SendLeave(groupAddress tcpip.Address) *tcpip.Error {
+func (mld *mldState) SendLeave(groupAddress tcpip.Address) tcpip.Error {
 	_, err := mld.writePacket(header.IPv6AllRoutersMulticastAddress, groupAddress, header.ICMPv6MulticastListenerDone)
 	return err
 }
@@ -112,7 +112,7 @@ func (mld *mldState) handleMulticastListenerReport(mldHdr header.MLD) {
 // joinGroup handles joining a new group and sending and scheduling the required
 // messages.
 //
-// If the group is already joined, returns tcpip.ErrDuplicateAddress.
+// If the group is already joined, returns *tcpip.ErrDuplicateAddress.
 //
 // Precondition: mld.ep.mu must be locked.
 func (mld *mldState) joinGroup(groupAddress tcpip.Address) {
@@ -131,13 +131,13 @@ func (mld *mldState) isInGroup(groupAddress tcpip.Address) bool {
 // required.
 //
 // Precondition: mld.ep.mu must be locked.
-func (mld *mldState) leaveGroup(groupAddress tcpip.Address) *tcpip.Error {
+func (mld *mldState) leaveGroup(groupAddress tcpip.Address) tcpip.Error {
 	// LeaveGroup returns false only if the group was not joined.
 	if mld.genericMulticastProtocol.LeaveGroupLocked(groupAddress) {
 		return nil
 	}
 
-	return tcpip.ErrBadLocalAddress
+	return &tcpip.ErrBadLocalAddress{}
 }
 
 // softLeaveAll leaves all groups from the perspective of MLD, but remains
@@ -166,7 +166,7 @@ func (mld *mldState) sendQueuedReports() {
 // writePacket assembles and sends an MLD packet.
 //
 // Precondition: mld.ep.mu must be read locked.
-func (mld *mldState) writePacket(destAddress, groupAddress tcpip.Address, mldType header.ICMPv6Type) (bool, *tcpip.Error) {
+func (mld *mldState) writePacket(destAddress, groupAddress tcpip.Address, mldType header.ICMPv6Type) (bool, tcpip.Error) {
 	sentStats := mld.ep.stats.icmp.packetsSent
 	var mldStat tcpip.MultiCounterStat
 	switch mldType {
diff --git a/pkg/tcpip/network/ipv6/ndp.go b/pkg/tcpip/network/ipv6/ndp.go
index ca4ff621d..d7dde1767 100644
--- a/pkg/tcpip/network/ipv6/ndp.go
+++ b/pkg/tcpip/network/ipv6/ndp.go
@@ -241,7 +241,7 @@ type NDPDispatcher interface {
 	//
 	// This function is not permitted to block indefinitely. This function
 	// is also not permitted to call into the stack.
-	OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err *tcpip.Error)
+	OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error)
 
 	// OnDefaultRouterDiscovered is called when a new default router is
 	// discovered. Implementations must return true if the newly discovered
@@ -614,10 +614,10 @@ type slaacPrefixState struct {
 // tentative.
 //
 // The IPv6 endpoint that ndp belongs to MUST be locked.
-func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressEndpoint stack.AddressEndpoint) *tcpip.Error {
+func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressEndpoint stack.AddressEndpoint) tcpip.Error {
 	// addr must be a valid unicast IPv6 address.
 	if !header.IsV6UnicastAddress(addr) {
-		return tcpip.ErrAddressFamilyNotSupported
+		return &tcpip.ErrAddressFamilyNotSupported{}
 	}
 
 	if addressEndpoint.GetKind() != stack.PermanentTentative {
@@ -666,7 +666,7 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 
 			dadDone := remaining == 0
 
-			var err *tcpip.Error
+			var err tcpip.Error
 			if !dadDone {
 				err = ndp.sendDADPacket(addr, addressEndpoint)
 			}
@@ -717,7 +717,7 @@ func (ndp *ndpState) startDuplicateAddressDetection(addr tcpip.Address, addressE
 // addr.
 //
 // addr must be a tentative IPv6 address on ndp's IPv6 endpoint.
-func (ndp *ndpState) sendDADPacket(addr tcpip.Address, addressEndpoint stack.AddressEndpoint) *tcpip.Error {
+func (ndp *ndpState) sendDADPacket(addr tcpip.Address, addressEndpoint stack.AddressEndpoint) tcpip.Error {
 	snmc := header.SolicitedNodeAddr(addr)
 
 	icmp := header.ICMPv6(buffer.NewView(header.ICMPv6NeighborSolicitMinimumSize))
diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go
index 7a22309e5..9d34ea436 100644
--- a/pkg/tcpip/network/ipv6/ndp_test.go
+++ b/pkg/tcpip/network/ipv6/ndp_test.go
@@ -90,7 +90,7 @@ type testNDPDispatcher struct {
 	addr tcpip.Address
 }
 
-func (*testNDPDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, *tcpip.Error) {
+func (*testNDPDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, tcpip.Error) {
 }
 
 func (t *testNDPDispatcher) OnDefaultRouterDiscovered(_ tcpip.NICID, addr tcpip.Address) bool {
@@ -242,17 +242,19 @@ func TestNeighorSolicitationWithSourceLinkLayerOption(t *testing.T) {
 			})
 
 			wantInvalid := uint64(0)
-			wantErr := (*tcpip.Error)(nil)
 			wantSucccess := true
 			if len(test.expectedLinkAddr) == 0 {
 				wantInvalid = 1
-				wantErr = tcpip.ErrWouldBlock
 				wantSucccess = false
+				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, &tcpip.ErrWouldBlock{})
+				}
+			} else {
+				if err != nil {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = nil", nicID, lladdr1, lladdr0, ProtocolNumber, err)
+				}
 			}
 
-			if err != wantErr {
-				t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, wantErr)
-			}
 			if diff := cmp.Diff(stack.LinkResolutionResult{LinkAddress: test.expectedLinkAddr, Success: wantSucccess}, <-ch); diff != "" {
 				t.Errorf("linkResolutionResult mismatch (-want +got):\n%s", diff)
 			}
@@ -801,17 +803,19 @@ func TestNeighorAdvertisementWithTargetLinkLayerOption(t *testing.T) {
 			})
 
 			wantInvalid := uint64(0)
-			wantErr := (*tcpip.Error)(nil)
 			wantSucccess := true
 			if len(test.expectedLinkAddr) == 0 {
 				wantInvalid = 1
-				wantErr = tcpip.ErrWouldBlock
 				wantSucccess = false
+				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, &tcpip.ErrWouldBlock{})
+				}
+			} else {
+				if err != nil {
+					t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = nil", nicID, lladdr1, lladdr0, ProtocolNumber, err)
+				}
 			}
 
-			if err != wantErr {
-				t.Errorf("got s.GetLinkAddress(%d, %s, %s, %d, _) = %s, want = %s", nicID, lladdr1, lladdr0, ProtocolNumber, err, wantErr)
-			}
 			if diff := cmp.Diff(stack.LinkResolutionResult{LinkAddress: test.expectedLinkAddr, Success: wantSucccess}, <-ch); diff != "" {
 				t.Errorf("linkResolutionResult mismatch (-want +got):\n%s", diff)
 			}
diff --git a/pkg/tcpip/network/testutil/testutil.go b/pkg/tcpip/network/testutil/testutil.go
index 9bd009374..f5fa77b65 100644
--- a/pkg/tcpip/network/testutil/testutil.go
+++ b/pkg/tcpip/network/testutil/testutil.go
@@ -35,7 +35,7 @@ type MockLinkEndpoint struct {
 	WrittenPackets []*stack.PacketBuffer
 
 	mtu          uint32
-	err          *tcpip.Error
+	err          tcpip.Error
 	allowPackets int
 }
 
@@ -43,7 +43,7 @@ type MockLinkEndpoint struct {
 //
 // err is the error that will be returned once allowPackets packets are written
 // to the endpoint.
-func NewMockLinkEndpoint(mtu uint32, err *tcpip.Error, allowPackets int) *MockLinkEndpoint {
+func NewMockLinkEndpoint(mtu uint32, err tcpip.Error, allowPackets int) *MockLinkEndpoint {
 	return &MockLinkEndpoint{
 		mtu:          mtu,
 		err:          err,
@@ -64,7 +64,7 @@ func (*MockLinkEndpoint) MaxHeaderLength() uint16 { return 0 }
 func (*MockLinkEndpoint) LinkAddress() tcpip.LinkAddress { return "" }
 
 // WritePacket implements LinkEndpoint.WritePacket.
-func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
 	if ep.allowPackets == 0 {
 		return ep.err
 	}
@@ -74,7 +74,7 @@ func (ep *MockLinkEndpoint) WritePacket(_ stack.RouteInfo, _ *stack.GSO, _ tcpip
 }
 
 // WritePackets implements LinkEndpoint.WritePackets.
-func (ep *MockLinkEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (ep *MockLinkEndpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	var n int
 
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
diff --git a/pkg/tcpip/ports/BUILD b/pkg/tcpip/ports/BUILD
index 2bad05a2e..57abec5c9 100644
--- a/pkg/tcpip/ports/BUILD
+++ b/pkg/tcpip/ports/BUILD
@@ -18,5 +18,6 @@ go_test(
     library = ":ports",
     deps = [
         "//pkg/tcpip",
+        "@com_github_google_go_cmp//cmp:go_default_library",
     ],
 )
diff --git a/pkg/tcpip/ports/ports.go b/pkg/tcpip/ports/ports.go
index d87193650..11dbdbbcf 100644
--- a/pkg/tcpip/ports/ports.go
+++ b/pkg/tcpip/ports/ports.go
@@ -329,7 +329,7 @@ func NewPortManager() *PortManager {
 // possible ephemeral ports, allowing the caller to decide whether a given port
 // is suitable for its needs, and stopping when a port is found or an error
 // occurs.
-func (s *PortManager) PickEphemeralPort(testPort func(p uint16) (bool, *tcpip.Error)) (port uint16, err *tcpip.Error) {
+func (s *PortManager) PickEphemeralPort(testPort func(p uint16) (bool, tcpip.Error)) (port uint16, err tcpip.Error) {
 	offset := uint32(rand.Int31n(numEphemeralPorts))
 	return s.pickEphemeralPort(offset, numEphemeralPorts, testPort)
 }
@@ -348,7 +348,7 @@ func (s *PortManager) incPortHint() {
 // iterates over all ephemeral ports, allowing the caller to decide whether a
 // given port is suitable for its needs and stopping when a port is found or an
 // error occurs.
-func (s *PortManager) PickEphemeralPortStable(offset uint32, testPort func(p uint16) (bool, *tcpip.Error)) (port uint16, err *tcpip.Error) {
+func (s *PortManager) PickEphemeralPortStable(offset uint32, testPort func(p uint16) (bool, tcpip.Error)) (port uint16, err tcpip.Error) {
 	p, err := s.pickEphemeralPort(s.portHint()+offset, numEphemeralPorts, testPort)
 	if err == nil {
 		s.incPortHint()
@@ -361,7 +361,7 @@ func (s *PortManager) PickEphemeralPortStable(offset uint32, testPort func(p uin
 // and iterates over the number of ports specified by count and allows the
 // caller to decide whether a given port is suitable for its needs, and stopping
 // when a port is found or an error occurs.
-func (s *PortManager) pickEphemeralPort(offset, count uint32, testPort func(p uint16) (bool, *tcpip.Error)) (port uint16, err *tcpip.Error) {
+func (s *PortManager) pickEphemeralPort(offset, count uint32, testPort func(p uint16) (bool, tcpip.Error)) (port uint16, err tcpip.Error) {
 	for i := uint32(0); i < count; i++ {
 		port = uint16(FirstEphemeral + (offset+i)%count)
 		ok, err := testPort(port)
@@ -374,7 +374,7 @@ func (s *PortManager) pickEphemeralPort(offset, count uint32, testPort func(p ui
 		}
 	}
 
-	return 0, tcpip.ErrNoPortAvailable
+	return 0, &tcpip.ErrNoPortAvailable{}
 }
 
 // IsPortAvailable tests if the given port is available on all given protocols.
@@ -404,7 +404,7 @@ func (s *PortManager) isPortAvailableLocked(networks []tcpip.NetworkProtocolNumb
 // An optional testPort closure can be passed in which if provided will be used
 // to test if the picked port can be used. The function should return true if
 // the port is safe to use, false otherwise.
-func (s *PortManager) ReservePort(networks []tcpip.NetworkProtocolNumber, transport tcpip.TransportProtocolNumber, addr tcpip.Address, port uint16, flags Flags, bindToDevice tcpip.NICID, dest tcpip.FullAddress, testPort func(port uint16) bool) (reservedPort uint16, err *tcpip.Error) {
+func (s *PortManager) ReservePort(networks []tcpip.NetworkProtocolNumber, transport tcpip.TransportProtocolNumber, addr tcpip.Address, port uint16, flags Flags, bindToDevice tcpip.NICID, dest tcpip.FullAddress, testPort func(port uint16) bool) (reservedPort uint16, err tcpip.Error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -414,17 +414,17 @@ func (s *PortManager) ReservePort(networks []tcpip.NetworkProtocolNumber, transp
 	// protocols.
 	if port != 0 {
 		if !s.reserveSpecificPort(networks, transport, addr, port, flags, bindToDevice, dst) {
-			return 0, tcpip.ErrPortInUse
+			return 0, &tcpip.ErrPortInUse{}
 		}
 		if testPort != nil && !testPort(port) {
 			s.releasePortLocked(networks, transport, addr, port, flags.Bits(), bindToDevice, dst)
-			return 0, tcpip.ErrPortInUse
+			return 0, &tcpip.ErrPortInUse{}
 		}
 		return port, nil
 	}
 
 	// A port wasn't specified, so try to find one.
-	return s.PickEphemeralPort(func(p uint16) (bool, *tcpip.Error) {
+	return s.PickEphemeralPort(func(p uint16) (bool, tcpip.Error) {
 		if !s.reserveSpecificPort(networks, transport, addr, p, flags, bindToDevice, dst) {
 			return false, nil
 		}
diff --git a/pkg/tcpip/ports/ports_test.go b/pkg/tcpip/ports/ports_test.go
index 4bc949fd8..e70fbb72b 100644
--- a/pkg/tcpip/ports/ports_test.go
+++ b/pkg/tcpip/ports/ports_test.go
@@ -18,6 +18,7 @@ import (
 	"math/rand"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
@@ -32,7 +33,7 @@ const (
 type portReserveTestAction struct {
 	port    uint16
 	ip      tcpip.Address
-	want    *tcpip.Error
+	want    tcpip.Error
 	flags   Flags
 	release bool
 	device  tcpip.NICID
@@ -50,19 +51,19 @@ func TestPortReservation(t *testing.T) {
 				{port: 80, ip: fakeIPAddress, want: nil},
 				{port: 80, ip: fakeIPAddress1, want: nil},
 				/* N.B. Order of tests matters! */
-				{port: 80, ip: anyIPAddress, want: tcpip.ErrPortInUse},
-				{port: 80, ip: fakeIPAddress, want: tcpip.ErrPortInUse, flags: Flags{LoadBalanced: true}},
+				{port: 80, ip: anyIPAddress, want: &tcpip.ErrPortInUse{}},
+				{port: 80, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}, flags: Flags{LoadBalanced: true}},
 			},
 		},
 		{
 			tname: "bind to inaddr any",
 			actions: []portReserveTestAction{
 				{port: 22, ip: anyIPAddress, want: nil},
-				{port: 22, ip: fakeIPAddress, want: tcpip.ErrPortInUse},
+				{port: 22, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}},
 				/* release fakeIPAddress, but anyIPAddress is still inuse */
 				{port: 22, ip: fakeIPAddress, release: true},
-				{port: 22, ip: fakeIPAddress, want: tcpip.ErrPortInUse},
-				{port: 22, ip: fakeIPAddress, want: tcpip.ErrPortInUse, flags: Flags{LoadBalanced: true}},
+				{port: 22, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}},
+				{port: 22, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}, flags: Flags{LoadBalanced: true}},
 				/* Release port 22 from any IP address, then try to reserve fake IP address on 22 */
 				{port: 22, ip: anyIPAddress, want: nil, release: true},
 				{port: 22, ip: fakeIPAddress, want: nil},
@@ -80,8 +81,8 @@ func TestPortReservation(t *testing.T) {
 				{port: 25, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 25, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 
-				{port: 25, ip: fakeIPAddress, flags: Flags{}, want: tcpip.ErrPortInUse},
-				{port: 25, ip: anyIPAddress, flags: Flags{}, want: tcpip.ErrPortInUse},
+				{port: 25, ip: fakeIPAddress, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
+				{port: 25, ip: anyIPAddress, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
 
 				{port: 25, ip: anyIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 			},
@@ -91,14 +92,14 @@ func TestPortReservation(t *testing.T) {
 				{port: 24, ip: anyIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: anyIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 
-				{port: 24, ip: anyIPAddress, flags: Flags{}, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, flags: Flags{}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: anyIPAddress, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
 
 				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, release: true, want: nil},
 
 				{port: 24, ip: anyIPAddress, flags: Flags{LoadBalanced: true}, release: true},
-				{port: 24, ip: anyIPAddress, flags: Flags{}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: anyIPAddress, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
 
 				{port: 24, ip: anyIPAddress, flags: Flags{LoadBalanced: true}, release: true},
 				{port: 24, ip: anyIPAddress, flags: Flags{}, want: nil},
@@ -107,7 +108,7 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind twice with device fails",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 3, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 3, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 3, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind to device",
@@ -119,50 +120,50 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind to device and then without device",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind without device",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 123, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 123, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with device",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 123, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, device: 0, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 123, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, device: 0, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 456, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, device: 789, want: nil},
-				{port: 24, ip: fakeIPAddress, want: tcpip.ErrPortInUse},
-				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}},
+				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with reuseport",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 123, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 123, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: nil},
 			},
 		}, {
 			tname: "binding with reuseport and device",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 123, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 123, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 456, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, device: 789, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 999, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 999, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "mixing reuseport and not reuseport by binding to device",
@@ -177,14 +178,14 @@ func TestPortReservation(t *testing.T) {
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, device: 456, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind and release",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 345, flags: Flags{}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 345, flags: Flags{}, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 789, flags: Flags{LoadBalanced: true}, want: nil},
 
 				// Release the bind to device 0 and try again.
@@ -195,7 +196,7 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind twice with reuseport once",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "release an unreserved device",
@@ -213,16 +214,16 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind with reuseaddr",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 123, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 123, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{MostRecent: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, want: &tcpip.ErrPortInUse{}},
 				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{MostRecent: true}, want: nil},
 			},
 		}, {
 			tname: "bind twice with reuseaddr once",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, device: 123, flags: Flags{}, want: nil},
-				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{MostRecent: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, device: 0, flags: Flags{MostRecent: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with reuseaddr and reuseport",
@@ -236,14 +237,14 @@ func TestPortReservation(t *testing.T) {
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true, LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with reuseaddr and reuseport, and then reuseport",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true, LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with reuseaddr and reuseport twice, and then reuseaddr",
@@ -264,14 +265,14 @@ func TestPortReservation(t *testing.T) {
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true, LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind with reuseport, and then reuseaddr and reuseport",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{LoadBalanced: true}, want: nil},
 				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true, LoadBalanced: true}, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{MostRecent: true}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind tuple with reuseaddr, and then wildcard with reuseaddr",
@@ -283,7 +284,7 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind tuple with reuseaddr, and then wildcard",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, flags: Flags{TupleOnly: true}, dest: tcpip.FullAddress{Addr: fakeIPAddress, Port: 24}, want: nil},
-				{port: 24, ip: fakeIPAddress, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind wildcard with reuseaddr, and then tuple with reuseaddr",
@@ -295,7 +296,7 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind tuple with reuseaddr, and then wildcard",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{TupleOnly: true}, dest: tcpip.FullAddress{Addr: fakeIPAddress, Port: 24}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{TupleOnly: true}, dest: tcpip.FullAddress{Addr: fakeIPAddress, Port: 24}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind two tuples with reuseaddr",
@@ -313,7 +314,7 @@ func TestPortReservation(t *testing.T) {
 			tname: "bind wildcard, and then tuple with reuseaddr",
 			actions: []portReserveTestAction{
 				{port: 24, ip: fakeIPAddress, dest: tcpip.FullAddress{}, want: nil},
-				{port: 24, ip: fakeIPAddress, flags: Flags{TupleOnly: true}, dest: tcpip.FullAddress{Addr: fakeIPAddress, Port: 24}, want: tcpip.ErrPortInUse},
+				{port: 24, ip: fakeIPAddress, flags: Flags{TupleOnly: true}, dest: tcpip.FullAddress{Addr: fakeIPAddress, Port: 24}, want: &tcpip.ErrPortInUse{}},
 			},
 		}, {
 			tname: "bind wildcard twice with reuseaddr",
@@ -333,8 +334,8 @@ func TestPortReservation(t *testing.T) {
 					continue
 				}
 				gotPort, err := pm.ReservePort(net, fakeTransNumber, test.ip, test.port, test.flags, test.device, test.dest, nil /* testPort */)
-				if err != test.want {
-					t.Fatalf("ReservePort(.., .., %s, %d, %+v, %d, %v) = %v, want %v", test.ip, test.port, test.flags, test.device, test.dest, err, test.want)
+				if diff := cmp.Diff(test.want, err); diff != "" {
+					t.Fatalf("unexpected error from ReservePort(.., .., %s, %d, %+v, %d, %v), (-want, +got):\n%s", test.ip, test.port, test.flags, test.device, test.dest, diff)
 				}
 				if test.port == 0 && (gotPort == 0 || gotPort < FirstEphemeral) {
 					t.Fatalf("ReservePort(.., .., .., 0, ..) = %d, want port number >= %d to be picked", gotPort, FirstEphemeral)
@@ -345,30 +346,29 @@ func TestPortReservation(t *testing.T) {
 }
 
 func TestPickEphemeralPort(t *testing.T) {
-	customErr := &tcpip.Error{}
 	for _, test := range []struct {
 		name     string
-		f        func(port uint16) (bool, *tcpip.Error)
-		wantErr  *tcpip.Error
+		f        func(port uint16) (bool, tcpip.Error)
+		wantErr  tcpip.Error
 		wantPort uint16
 	}{
 		{
 			name: "no-port-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				return false, nil
 			},
-			wantErr: tcpip.ErrNoPortAvailable,
+			wantErr: &tcpip.ErrNoPortAvailable{},
 		},
 		{
 			name: "port-tester-error",
-			f: func(port uint16) (bool, *tcpip.Error) {
-				return false, customErr
+			f: func(port uint16) (bool, tcpip.Error) {
+				return false, &tcpip.ErrBadBuffer{}
 			},
-			wantErr: customErr,
+			wantErr: &tcpip.ErrBadBuffer{},
 		},
 		{
 			name: "only-port-16042-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				if port == FirstEphemeral+42 {
 					return true, nil
 				}
@@ -378,49 +378,52 @@ func TestPickEphemeralPort(t *testing.T) {
 		},
 		{
 			name: "only-port-under-16000-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				if port < FirstEphemeral {
 					return true, nil
 				}
 				return false, nil
 			},
-			wantErr: tcpip.ErrNoPortAvailable,
+			wantErr: &tcpip.ErrNoPortAvailable{},
 		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			pm := NewPortManager()
-			if port, err := pm.PickEphemeralPort(test.f); port != test.wantPort || err != test.wantErr {
-				t.Errorf("PickEphemeralPort(..) = (port %d, err %v); want (port %d, err %v)", port, err, test.wantPort, test.wantErr)
+			port, err := pm.PickEphemeralPort(test.f)
+			if diff := cmp.Diff(test.wantErr, err); diff != "" {
+				t.Fatalf("unexpected error from PickEphemeralPort(..), (-want, +got):\n%s", diff)
+			}
+			if port != test.wantPort {
+				t.Errorf("got PickEphemeralPort(..) = (%d, nil); want (%d, nil)", port, test.wantPort)
 			}
 		})
 	}
 }
 
 func TestPickEphemeralPortStable(t *testing.T) {
-	customErr := &tcpip.Error{}
 	for _, test := range []struct {
 		name     string
-		f        func(port uint16) (bool, *tcpip.Error)
-		wantErr  *tcpip.Error
+		f        func(port uint16) (bool, tcpip.Error)
+		wantErr  tcpip.Error
 		wantPort uint16
 	}{
 		{
 			name: "no-port-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				return false, nil
 			},
-			wantErr: tcpip.ErrNoPortAvailable,
+			wantErr: &tcpip.ErrNoPortAvailable{},
 		},
 		{
 			name: "port-tester-error",
-			f: func(port uint16) (bool, *tcpip.Error) {
-				return false, customErr
+			f: func(port uint16) (bool, tcpip.Error) {
+				return false, &tcpip.ErrBadBuffer{}
 			},
-			wantErr: customErr,
+			wantErr: &tcpip.ErrBadBuffer{},
 		},
 		{
 			name: "only-port-16042-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				if port == FirstEphemeral+42 {
 					return true, nil
 				}
@@ -430,20 +433,24 @@ func TestPickEphemeralPortStable(t *testing.T) {
 		},
 		{
 			name: "only-port-under-16000-available",
-			f: func(port uint16) (bool, *tcpip.Error) {
+			f: func(port uint16) (bool, tcpip.Error) {
 				if port < FirstEphemeral {
 					return true, nil
 				}
 				return false, nil
 			},
-			wantErr: tcpip.ErrNoPortAvailable,
+			wantErr: &tcpip.ErrNoPortAvailable{},
 		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			pm := NewPortManager()
 			portOffset := uint32(rand.Int31n(int32(numEphemeralPorts)))
-			if port, err := pm.PickEphemeralPortStable(portOffset, test.f); port != test.wantPort || err != test.wantErr {
-				t.Errorf("PickEphemeralPort(..) = (port %d, err %v); want (port %d, err %v)", port, err, test.wantPort, test.wantErr)
+			port, err := pm.PickEphemeralPortStable(portOffset, test.f)
+			if diff := cmp.Diff(test.wantErr, err); diff != "" {
+				t.Fatalf("unexpected error from PickEphemeralPort(..), (-want, +got):\n%s", diff)
+			}
+			if port != test.wantPort {
+				t.Errorf("got PickEphemeralPort(..) = (%d, nil); want (%d, nil)", port, test.wantPort)
 			}
 		})
 	}
diff --git a/pkg/tcpip/sample/tun_tcp_connect/main.go b/pkg/tcpip/sample/tun_tcp_connect/main.go
index 3d9954c84..856ea998d 100644
--- a/pkg/tcpip/sample/tun_tcp_connect/main.go
+++ b/pkg/tcpip/sample/tun_tcp_connect/main.go
@@ -175,7 +175,7 @@ func main() {
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
 	wq.EventRegister(&waitEntry, waiter.EventOut)
 	terr := ep.Connect(remote)
-	if terr == tcpip.ErrConnectStarted {
+	if _, ok := terr.(*tcpip.ErrConnectStarted); ok {
 		fmt.Println("Connect is pending...")
 		<-notifyCh
 		terr = ep.LastError()
@@ -198,11 +198,11 @@ func main() {
 	for {
 		_, err := ep.Read(os.Stdout, tcpip.ReadOptions{})
 		if err != nil {
-			if err == tcpip.ErrClosedForReceive {
+			if _, ok := err.(*tcpip.ErrClosedForReceive); ok {
 				break
 			}
 
-			if err == tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 				<-notifyCh
 				continue
 			}
diff --git a/pkg/tcpip/sample/tun_tcp_echo/main.go b/pkg/tcpip/sample/tun_tcp_echo/main.go
index ae9cf44e7..9b23df3a9 100644
--- a/pkg/tcpip/sample/tun_tcp_echo/main.go
+++ b/pkg/tcpip/sample/tun_tcp_echo/main.go
@@ -51,7 +51,7 @@ type endpointWriter struct {
 }
 
 type tcpipError struct {
-	inner *tcpip.Error
+	inner tcpip.Error
 }
 
 func (e *tcpipError) Error() string {
@@ -89,7 +89,7 @@ func echo(wq *waiter.Queue, ep tcpip.Endpoint) {
 	for {
 		_, err := ep.Read(&w, tcpip.ReadOptions{})
 		if err != nil {
-			if err == tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 				<-notifyCh
 				continue
 			}
@@ -217,7 +217,7 @@ func main() {
 	for {
 		n, wq, err := ep.Accept(nil)
 		if err != nil {
-			if err == tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 				<-notifyCh
 				continue
 			}
diff --git a/pkg/tcpip/socketops.go b/pkg/tcpip/socketops.go
index 7eabbc599..019d6a63c 100644
--- a/pkg/tcpip/socketops.go
+++ b/pkg/tcpip/socketops.go
@@ -46,16 +46,16 @@ type SocketOptionsHandler interface {
 	OnCorkOptionSet(v bool)
 
 	// LastError is invoked when SO_ERROR is read for an endpoint.
-	LastError() *Error
+	LastError() Error
 
 	// UpdateLastError updates the endpoint specific last error field.
-	UpdateLastError(err *Error)
+	UpdateLastError(err Error)
 
 	// HasNIC is invoked to check if the NIC is valid for SO_BINDTODEVICE.
 	HasNIC(v int32) bool
 
 	// GetSendBufferSize is invoked to get the SO_SNDBUFSIZE.
-	GetSendBufferSize() (int64, *Error)
+	GetSendBufferSize() (int64, Error)
 
 	// IsUnixSocket is invoked to check if the socket is of unix domain.
 	IsUnixSocket() bool
@@ -83,12 +83,12 @@ func (*DefaultSocketOptionsHandler) OnDelayOptionSet(bool) {}
 func (*DefaultSocketOptionsHandler) OnCorkOptionSet(bool) {}
 
 // LastError implements SocketOptionsHandler.LastError.
-func (*DefaultSocketOptionsHandler) LastError() *Error {
+func (*DefaultSocketOptionsHandler) LastError() Error {
 	return nil
 }
 
 // UpdateLastError implements SocketOptionsHandler.UpdateLastError.
-func (*DefaultSocketOptionsHandler) UpdateLastError(*Error) {}
+func (*DefaultSocketOptionsHandler) UpdateLastError(Error) {}
 
 // HasNIC implements SocketOptionsHandler.HasNIC.
 func (*DefaultSocketOptionsHandler) HasNIC(int32) bool {
@@ -96,7 +96,7 @@ func (*DefaultSocketOptionsHandler) HasNIC(int32) bool {
 }
 
 // GetSendBufferSize implements SocketOptionsHandler.GetSendBufferSize.
-func (*DefaultSocketOptionsHandler) GetSendBufferSize() (int64, *Error) {
+func (*DefaultSocketOptionsHandler) GetSendBufferSize() (int64, Error) {
 	return 0, nil
 }
 
@@ -109,11 +109,11 @@ func (*DefaultSocketOptionsHandler) IsUnixSocket() bool {
 // implemented by the stack.
 type StackHandler interface {
 	// Option allows retrieving stack wide options.
-	Option(option interface{}) *Error
+	Option(option interface{}) Error
 
 	// TransportProtocolOption allows retrieving individual protocol level
 	// option values.
-	TransportProtocolOption(proto TransportProtocolNumber, option GettableTransportProtocolOption) *Error
+	TransportProtocolOption(proto TransportProtocolNumber, option GettableTransportProtocolOption) Error
 }
 
 // SocketOptions contains all the variables which store values for SOL_SOCKET,
@@ -238,7 +238,7 @@ func storeAtomicBool(addr *uint32, v bool) {
 }
 
 // SetLastError sets the last error for a socket.
-func (so *SocketOptions) SetLastError(err *Error) {
+func (so *SocketOptions) SetLastError(err Error) {
 	so.handler.UpdateLastError(err)
 }
 
@@ -423,7 +423,7 @@ func (so *SocketOptions) SetRecvError(v bool) {
 }
 
 // GetLastError gets value for SO_ERROR option.
-func (so *SocketOptions) GetLastError() *Error {
+func (so *SocketOptions) GetLastError() Error {
 	return so.handler.LastError()
 }
 
@@ -480,7 +480,7 @@ type SockError struct {
 	sockErrorEntry
 
 	// Err is the error caused by the errant packet.
-	Err *Error
+	Err Error
 	// ErrOrigin indicates the error origin.
 	ErrOrigin SockErrOrigin
 	// ErrType is the type in the ICMP header.
@@ -538,7 +538,7 @@ func (so *SocketOptions) QueueErr(err *SockError) {
 }
 
 // QueueLocalErr queues a local error onto the local queue.
-func (so *SocketOptions) QueueLocalErr(err *Error, net NetworkProtocolNumber, info uint32, dst FullAddress, payload []byte) {
+func (so *SocketOptions) QueueLocalErr(err Error, net NetworkProtocolNumber, info uint32, dst FullAddress, payload []byte) {
 	so.QueueErr(&SockError{
 		Err:       err,
 		ErrOrigin: SockExtErrorOriginLocal,
@@ -555,9 +555,9 @@ func (so *SocketOptions) GetBindToDevice() int32 {
 }
 
 // SetBindToDevice sets value for SO_BINDTODEVICE option.
-func (so *SocketOptions) SetBindToDevice(bindToDevice int32) *Error {
+func (so *SocketOptions) SetBindToDevice(bindToDevice int32) Error {
 	if !so.handler.HasNIC(bindToDevice) {
-		return ErrUnknownDevice
+		return &ErrUnknownDevice{}
 	}
 
 	atomic.StoreInt32(&so.bindToDevice, bindToDevice)
@@ -565,7 +565,7 @@ func (so *SocketOptions) SetBindToDevice(bindToDevice int32) *Error {
 }
 
 // GetSendBufferSize gets value for SO_SNDBUF option.
-func (so *SocketOptions) GetSendBufferSize() (int64, *Error) {
+func (so *SocketOptions) GetSendBufferSize() (int64, Error) {
 	if so.handler.IsUnixSocket() {
 		return so.handler.GetSendBufferSize()
 	}
diff --git a/pkg/tcpip/stack/addressable_endpoint_state.go b/pkg/tcpip/stack/addressable_endpoint_state.go
index cd423bf71..e5590ecc0 100644
--- a/pkg/tcpip/stack/addressable_endpoint_state.go
+++ b/pkg/tcpip/stack/addressable_endpoint_state.go
@@ -117,7 +117,7 @@ func (a *AddressableEndpointState) releaseAddressStateLocked(addrState *addressS
 }
 
 // AddAndAcquirePermanentAddress implements AddressableEndpoint.
-func (a *AddressableEndpointState) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated bool) (AddressEndpoint, *tcpip.Error) {
+func (a *AddressableEndpointState) AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated bool) (AddressEndpoint, tcpip.Error) {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	ep, err := a.addAndAcquireAddressLocked(addr, peb, configType, deprecated, true /* permanent */)
@@ -143,10 +143,10 @@ func (a *AddressableEndpointState) AddAndAcquirePermanentAddress(addr tcpip.Addr
 
 // AddAndAcquireTemporaryAddress adds a temporary address.
 //
-// Returns tcpip.ErrDuplicateAddress if the address exists.
+// Returns *tcpip.ErrDuplicateAddress if the address exists.
 //
 // The temporary address's endpoint is acquired and returned.
-func (a *AddressableEndpointState) AddAndAcquireTemporaryAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior) (AddressEndpoint, *tcpip.Error) {
+func (a *AddressableEndpointState) AddAndAcquireTemporaryAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior) (AddressEndpoint, tcpip.Error) {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	ep, err := a.addAndAcquireAddressLocked(addr, peb, AddressConfigStatic, false /* deprecated */, false /* permanent */)
@@ -176,11 +176,11 @@ func (a *AddressableEndpointState) AddAndAcquireTemporaryAddress(addr tcpip.Addr
 // If the addressable endpoint already has the address in a non-permanent state,
 // and addAndAcquireAddressLocked is adding a permanent address, that address is
 // promoted in place and its properties set to the properties provided. If the
-// address already exists in any other state, then tcpip.ErrDuplicateAddress is
+// address already exists in any other state, then *tcpip.ErrDuplicateAddress is
 // returned, regardless the kind of address that is being added.
 //
 // Precondition: a.mu must be write locked.
-func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated, permanent bool) (*addressState, *tcpip.Error) {
+func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated, permanent bool) (*addressState, tcpip.Error) {
 	// attemptAddToPrimary is false when the address is already in the primary
 	// address list.
 	attemptAddToPrimary := true
@@ -190,7 +190,7 @@ func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.Address
 			// We are adding a non-permanent address but the address exists. No need
 			// to go any further since we can only promote existing temporary/expired
 			// addresses to permanent.
-			return nil, tcpip.ErrDuplicateAddress
+			return nil, &tcpip.ErrDuplicateAddress{}
 		}
 
 		addrState.mu.Lock()
@@ -198,7 +198,7 @@ func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.Address
 			addrState.mu.Unlock()
 			// We are adding a permanent address but a permanent address already
 			// exists.
-			return nil, tcpip.ErrDuplicateAddress
+			return nil, &tcpip.ErrDuplicateAddress{}
 		}
 
 		if addrState.mu.refs == 0 {
@@ -293,7 +293,7 @@ func (a *AddressableEndpointState) addAndAcquireAddressLocked(addr tcpip.Address
 }
 
 // RemovePermanentAddress implements AddressableEndpoint.
-func (a *AddressableEndpointState) RemovePermanentAddress(addr tcpip.Address) *tcpip.Error {
+func (a *AddressableEndpointState) RemovePermanentAddress(addr tcpip.Address) tcpip.Error {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 	return a.removePermanentAddressLocked(addr)
@@ -303,10 +303,10 @@ func (a *AddressableEndpointState) RemovePermanentAddress(addr tcpip.Address) *t
 // requirements.
 //
 // Precondition: a.mu must be write locked.
-func (a *AddressableEndpointState) removePermanentAddressLocked(addr tcpip.Address) *tcpip.Error {
+func (a *AddressableEndpointState) removePermanentAddressLocked(addr tcpip.Address) tcpip.Error {
 	addrState, ok := a.mu.endpoints[addr]
 	if !ok {
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	return a.removePermanentEndpointLocked(addrState)
@@ -314,10 +314,10 @@ func (a *AddressableEndpointState) removePermanentAddressLocked(addr tcpip.Addre
 
 // RemovePermanentEndpoint removes the passed endpoint if it is associated with
 // a and permanent.
-func (a *AddressableEndpointState) RemovePermanentEndpoint(ep AddressEndpoint) *tcpip.Error {
+func (a *AddressableEndpointState) RemovePermanentEndpoint(ep AddressEndpoint) tcpip.Error {
 	addrState, ok := ep.(*addressState)
 	if !ok || addrState.addressableEndpointState != a {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	a.mu.Lock()
@@ -329,9 +329,9 @@ func (a *AddressableEndpointState) RemovePermanentEndpoint(ep AddressEndpoint) *
 // requirements.
 //
 // Precondition: a.mu must be write locked.
-func (a *AddressableEndpointState) removePermanentEndpointLocked(addrState *addressState) *tcpip.Error {
+func (a *AddressableEndpointState) removePermanentEndpointLocked(addrState *addressState) tcpip.Error {
 	if !addrState.GetKind().IsPermanent() {
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	addrState.SetKind(PermanentExpired)
@@ -574,9 +574,11 @@ func (a *AddressableEndpointState) Cleanup() {
 	defer a.mu.Unlock()
 
 	for _, ep := range a.mu.endpoints {
-		// removePermanentEndpointLocked returns tcpip.ErrBadLocalAddress if ep is
+		// removePermanentEndpointLocked returns *tcpip.ErrBadLocalAddress if ep is
 		// not a permanent address.
-		if err := a.removePermanentEndpointLocked(ep); err != nil && err != tcpip.ErrBadLocalAddress {
+		switch err := a.removePermanentEndpointLocked(ep); err.(type) {
+		case nil, *tcpip.ErrBadLocalAddress:
+		default:
 			panic(fmt.Sprintf("unexpected error from removePermanentEndpointLocked(%s): %s", ep.addr, err))
 		}
 	}
diff --git a/pkg/tcpip/stack/conntrack.go b/pkg/tcpip/stack/conntrack.go
index 5e649cca6..54617f2e6 100644
--- a/pkg/tcpip/stack/conntrack.go
+++ b/pkg/tcpip/stack/conntrack.go
@@ -198,15 +198,15 @@ type bucket struct {
 // TCP header.
 //
 // Preconditions: pkt.NetworkHeader() is valid.
-func packetToTupleID(pkt *PacketBuffer) (tupleID, *tcpip.Error) {
+func packetToTupleID(pkt *PacketBuffer) (tupleID, tcpip.Error) {
 	netHeader := pkt.Network()
 	if netHeader.TransportProtocol() != header.TCPProtocolNumber {
-		return tupleID{}, tcpip.ErrUnknownProtocol
+		return tupleID{}, &tcpip.ErrUnknownProtocol{}
 	}
 
 	tcpHeader := header.TCP(pkt.TransportHeader().View())
 	if len(tcpHeader) < header.TCPMinimumSize {
-		return tupleID{}, tcpip.ErrUnknownProtocol
+		return tupleID{}, &tcpip.ErrUnknownProtocol{}
 	}
 
 	return tupleID{
@@ -617,7 +617,7 @@ func (ct *ConnTrack) reapTupleLocked(tuple *tuple, bucket int, now time.Time) bo
 	return true
 }
 
-func (ct *ConnTrack) originalDst(epID TransportEndpointID, netProto tcpip.NetworkProtocolNumber) (tcpip.Address, uint16, *tcpip.Error) {
+func (ct *ConnTrack) originalDst(epID TransportEndpointID, netProto tcpip.NetworkProtocolNumber) (tcpip.Address, uint16, tcpip.Error) {
 	// Lookup the connection. The reply's original destination
 	// describes the original address.
 	tid := tupleID{
@@ -631,10 +631,10 @@ func (ct *ConnTrack) originalDst(epID TransportEndpointID, netProto tcpip.Networ
 	conn, _ := ct.connForTID(tid)
 	if conn == nil {
 		// Not a tracked connection.
-		return "", 0, tcpip.ErrNotConnected
+		return "", 0, &tcpip.ErrNotConnected{}
 	} else if conn.manip == manipNone {
 		// Unmanipulated connection.
-		return "", 0, tcpip.ErrInvalidOptionValue
+		return "", 0, &tcpip.ErrInvalidOptionValue{}
 	}
 
 	return conn.original.dstAddr, conn.original.dstPort, nil
diff --git a/pkg/tcpip/stack/forwarding_test.go b/pkg/tcpip/stack/forwarding_test.go
index d29c9a49b..63a42a2ea 100644
--- a/pkg/tcpip/stack/forwarding_test.go
+++ b/pkg/tcpip/stack/forwarding_test.go
@@ -55,7 +55,7 @@ type fwdTestNetworkEndpoint struct {
 	dispatcher TransportDispatcher
 }
 
-func (*fwdTestNetworkEndpoint) Enable() *tcpip.Error {
+func (*fwdTestNetworkEndpoint) Enable() tcpip.Error {
 	return nil
 }
 
@@ -112,7 +112,7 @@ func (f *fwdTestNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNu
 	return f.proto.Number()
 }
 
-func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) *tcpip.Error {
+func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	// Add the protocol's header to the packet and send it to the link
 	// endpoint.
 	b := pkt.NetworkHeader().Push(fwdTestNetHeaderLen)
@@ -124,14 +124,14 @@ func (f *fwdTestNetworkEndpoint) WritePacket(r *Route, gso *GSO, params NetworkH
 }
 
 // WritePackets implements LinkEndpoint.WritePackets.
-func (*fwdTestNetworkEndpoint) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, *tcpip.Error) {
+func (*fwdTestNetworkEndpoint) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
-func (f *fwdTestNetworkEndpoint) WriteHeaderIncludedPacket(r *Route, pkt *PacketBuffer) *tcpip.Error {
+func (f *fwdTestNetworkEndpoint) WriteHeaderIncludedPacket(r *Route, pkt *PacketBuffer) tcpip.Error {
 	// The network header should not already be populated.
 	if _, ok := pkt.NetworkHeader().Consume(fwdTestNetHeaderLen); !ok {
-		return tcpip.ErrMalformedHeader
+		return &tcpip.ErrMalformedHeader{}
 	}
 
 	return f.nic.WritePacket(r, nil /* gso */, fwdTestNetNumber, pkt)
@@ -207,19 +207,19 @@ func (f *fwdTestNetworkProtocol) NewEndpoint(nic NetworkInterface, _ LinkAddress
 	return e
 }
 
-func (*fwdTestNetworkProtocol) SetOption(tcpip.SettableNetworkProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*fwdTestNetworkProtocol) SetOption(tcpip.SettableNetworkProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
-func (*fwdTestNetworkProtocol) Option(tcpip.GettableNetworkProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*fwdTestNetworkProtocol) Option(tcpip.GettableNetworkProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 func (*fwdTestNetworkProtocol) Close() {}
 
 func (*fwdTestNetworkProtocol) Wait() {}
 
-func (f *fwdTestNetworkProtocol) LinkAddressRequest(addr, _ tcpip.Address, remoteLinkAddr tcpip.LinkAddress, _ NetworkInterface) *tcpip.Error {
+func (f *fwdTestNetworkProtocol) LinkAddressRequest(addr, _ tcpip.Address, remoteLinkAddr tcpip.LinkAddress, _ NetworkInterface) tcpip.Error {
 	if f.onLinkAddressResolved != nil {
 		time.AfterFunc(f.addrResolveDelay, func() {
 			f.onLinkAddressResolved(f.addrCache, f.neigh, addr, remoteLinkAddr)
@@ -319,7 +319,7 @@ func (e *fwdTestLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return e.linkAddr
 }
 
-func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) *tcpip.Error {
+func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	p := fwdTestPacketInfo{
 		RemoteLinkAddress: r.RemoteLinkAddress,
 		LocalLinkAddress:  r.LocalLinkAddress,
@@ -335,7 +335,7 @@ func (e fwdTestLinkEndpoint) WritePacket(r RouteInfo, gso *GSO, protocol tcpip.N
 }
 
 // WritePackets stores outbound packets into the channel.
-func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (e *fwdTestLinkEndpoint) WritePackets(r RouteInfo, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	n := 0
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		e.WritePacket(r, gso, protocol, pkt)
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 04af933a6..63832c200 100644
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -229,7 +229,7 @@ func (it *IPTables) GetTable(id TableID, ipv6 bool) Table {
 
 // ReplaceTable replaces or inserts table by name. It panics when an invalid id
 // is provided.
-func (it *IPTables) ReplaceTable(id TableID, table Table, ipv6 bool) *tcpip.Error {
+func (it *IPTables) ReplaceTable(id TableID, table Table, ipv6 bool) tcpip.Error {
 	it.mu.Lock()
 	defer it.mu.Unlock()
 	// If iptables is being enabled, initialize the conntrack table and
@@ -483,11 +483,11 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx
 
 // OriginalDst returns the original destination of redirected connections. It
 // returns an error if the connection doesn't exist or isn't redirected.
-func (it *IPTables) OriginalDst(epID TransportEndpointID, netProto tcpip.NetworkProtocolNumber) (tcpip.Address, uint16, *tcpip.Error) {
+func (it *IPTables) OriginalDst(epID TransportEndpointID, netProto tcpip.NetworkProtocolNumber) (tcpip.Address, uint16, tcpip.Error) {
 	it.mu.RLock()
 	defer it.mu.RUnlock()
 	if !it.modified {
-		return "", 0, tcpip.ErrNotConnected
+		return "", 0, &tcpip.ErrNotConnected{}
 	}
 	return it.connections.originalDst(epID, netProto)
 }
diff --git a/pkg/tcpip/stack/linkaddrcache.go b/pkg/tcpip/stack/linkaddrcache.go
index c68cbfed4..3ce7a57db 100644
--- a/pkg/tcpip/stack/linkaddrcache.go
+++ b/pkg/tcpip/stack/linkaddrcache.go
@@ -199,7 +199,7 @@ func (c *linkAddrCache) getOrCreateEntryLocked(k tcpip.Address) *linkAddrEntry {
 }
 
 // get reports any known link address for k.
-func (c *linkAddrCache) get(k tcpip.Address, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, onResolve func(LinkResolutionResult)) (tcpip.LinkAddress, <-chan struct{}, *tcpip.Error) {
+func (c *linkAddrCache) get(k tcpip.Address, linkRes LinkAddressResolver, localAddr tcpip.Address, nic NetworkInterface, onResolve func(LinkResolutionResult)) (tcpip.LinkAddress, <-chan struct{}, tcpip.Error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	entry := c.getOrCreateEntryLocked(k)
@@ -226,7 +226,7 @@ func (c *linkAddrCache) get(k tcpip.Address, linkRes LinkAddressResolver, localA
 			entry.mu.done = make(chan struct{})
 			go c.startAddressResolution(k, linkRes, localAddr, nic, entry.mu.done) // S/R-SAFE: link non-savable; wakers dropped synchronously.
 		}
-		return entry.mu.linkAddr, entry.mu.done, tcpip.ErrWouldBlock
+		return entry.mu.linkAddr, entry.mu.done, &tcpip.ErrWouldBlock{}
 	default:
 		panic(fmt.Sprintf("invalid cache entry state: %s", s))
 	}
diff --git a/pkg/tcpip/stack/linkaddrcache_test.go b/pkg/tcpip/stack/linkaddrcache_test.go
index 1bf7fad09..466a5e8d9 100644
--- a/pkg/tcpip/stack/linkaddrcache_test.go
+++ b/pkg/tcpip/stack/linkaddrcache_test.go
@@ -48,7 +48,7 @@ type testLinkAddressResolver struct {
 	onLinkAddressRequest func()
 }
 
-func (r *testLinkAddressResolver) LinkAddressRequest(targetAddr, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) *tcpip.Error {
+func (r *testLinkAddressResolver) LinkAddressRequest(targetAddr, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) tcpip.Error {
 	// TODO(gvisor.dev/issue/5141): Use a fake clock.
 	time.AfterFunc(r.delay, func() { r.fakeRequest(targetAddr) })
 	if f := r.onLinkAddressRequest; f != nil {
@@ -77,13 +77,13 @@ func (*testLinkAddressResolver) LinkAddressProtocol() tcpip.NetworkProtocolNumbe
 	return 1
 }
 
-func getBlocking(c *linkAddrCache, addr tcpip.Address, linkRes LinkAddressResolver) (tcpip.LinkAddress, *tcpip.Error) {
+func getBlocking(c *linkAddrCache, addr tcpip.Address, linkRes LinkAddressResolver) (tcpip.LinkAddress, tcpip.Error) {
 	var attemptedResolution bool
 	for {
 		got, ch, err := c.get(addr, linkRes, "", nil, nil)
-		if err == tcpip.ErrWouldBlock {
+		if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 			if attemptedResolution {
-				return got, tcpip.ErrTimeout
+				return got, &tcpip.ErrTimeout{}
 			}
 			attemptedResolution = true
 			<-ch
@@ -177,7 +177,8 @@ func TestCacheAgeLimit(t *testing.T) {
 	e := testAddrs[0]
 	c.AddLinkAddress(e.addr, e.linkAddr)
 	time.Sleep(50 * time.Millisecond)
-	if _, _, err := c.get(e.addr, linkRes, "", nil, nil); err != tcpip.ErrWouldBlock {
+	_, _, err := c.get(e.addr, linkRes, "", nil, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		t.Errorf("got c.get(%s, _, '', nil, nil) = %s, want = ErrWouldBlock", e.addr, err)
 	}
 }
@@ -259,8 +260,9 @@ func TestCacheResolutionFailed(t *testing.T) {
 	before := atomic.LoadUint32(&requestCount)
 
 	e.addr += "2"
-	if a, err := getBlocking(c, e.addr, linkRes); err != tcpip.ErrTimeout {
-		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
+	a, err := getBlocking(c, e.addr, linkRes)
+	if _, ok := err.(*tcpip.ErrTimeout); !ok {
+		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, &tcpip.ErrTimeout{})
 	}
 
 	if got, want := int(atomic.LoadUint32(&requestCount)-before), c.resolutionAttempts; got != want {
@@ -275,7 +277,8 @@ func TestCacheResolutionTimeout(t *testing.T) {
 	linkRes := &testLinkAddressResolver{cache: c, delay: resolverDelay}
 
 	e := testAddrs[0]
-	if a, err := getBlocking(c, e.addr, linkRes); err != tcpip.ErrTimeout {
-		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, tcpip.ErrTimeout)
+	a, err := getBlocking(c, e.addr, linkRes)
+	if _, ok := err.(*tcpip.ErrTimeout); !ok {
+		t.Errorf("got getBlocking(_, %s, _) = (%s, %s), want = (_, %s)", e.addr, a, err, &tcpip.ErrTimeout{})
 	}
 }
diff --git a/pkg/tcpip/stack/ndp_test.go b/pkg/tcpip/stack/ndp_test.go
index d7bbb25ea..64383bc7c 100644
--- a/pkg/tcpip/stack/ndp_test.go
+++ b/pkg/tcpip/stack/ndp_test.go
@@ -104,7 +104,7 @@ type ndpDADEvent struct {
 	nicID    tcpip.NICID
 	addr     tcpip.Address
 	resolved bool
-	err      *tcpip.Error
+	err      tcpip.Error
 }
 
 type ndpRouterEvent struct {
@@ -174,7 +174,7 @@ type ndpDispatcher struct {
 }
 
 // Implements ipv6.NDPDispatcher.OnDuplicateAddressDetectionStatus.
-func (n *ndpDispatcher) OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err *tcpip.Error) {
+func (n *ndpDispatcher) OnDuplicateAddressDetectionStatus(nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error) {
 	if n.dadC != nil {
 		n.dadC <- ndpDADEvent{
 			nicID,
@@ -311,7 +311,7 @@ func (l *channelLinkWithHeaderLength) MaxHeaderLength() uint16 {
 
 // Check e to make sure that the event is for addr on nic with ID 1, and the
 // resolved flag set to resolved with the specified err.
-func checkDADEvent(e ndpDADEvent, nicID tcpip.NICID, addr tcpip.Address, resolved bool, err *tcpip.Error) string {
+func checkDADEvent(e ndpDADEvent, nicID tcpip.NICID, addr tcpip.Address, resolved bool, err tcpip.Error) string {
 	return cmp.Diff(ndpDADEvent{nicID: nicID, addr: addr, resolved: resolved, err: err}, e, cmp.AllowUnexported(e))
 }
 
@@ -465,8 +465,8 @@ func TestDADResolve(t *testing.T) {
 			// tentative address.
 			{
 				r, err := s.FindRoute(nicID, "", addr2, header.IPv6ProtocolNumber, false)
-				if err != tcpip.ErrNoRoute {
-					t.Errorf("got FindRoute(%d, '', %s, %d, false) = (%+v, %v), want = (_, %s)", nicID, addr2, header.IPv6ProtocolNumber, r, err, tcpip.ErrNoRoute)
+				if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+					t.Errorf("got FindRoute(%d, '', %s, %d, false) = (%+v, %v), want = (_, %s)", nicID, addr2, header.IPv6ProtocolNumber, r, err, &tcpip.ErrNoRoute{})
 				}
 				if r != nil {
 					r.Release()
@@ -474,8 +474,8 @@ func TestDADResolve(t *testing.T) {
 			}
 			{
 				r, err := s.FindRoute(nicID, addr1, addr2, header.IPv6ProtocolNumber, false)
-				if err != tcpip.ErrNoRoute {
-					t.Errorf("got FindRoute(%d, %s, %s, %d, false) = (%+v, %v), want = (_, %s)", nicID, addr1, addr2, header.IPv6ProtocolNumber, r, err, tcpip.ErrNoRoute)
+				if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+					t.Errorf("got FindRoute(%d, %s, %s, %d, false) = (%+v, %v), want = (_, %s)", nicID, addr1, addr2, header.IPv6ProtocolNumber, r, err, &tcpip.ErrNoRoute{})
 				}
 				if r != nil {
 					r.Release()
@@ -3222,8 +3222,11 @@ func TestAutoGenAddrJobDeprecation(t *testing.T) {
 			defer ep.Close()
 			ep.SocketOptions().SetV6Only(true)
 
-			if err := ep.Connect(dstAddr); err != tcpip.ErrNoRoute {
-				t.Errorf("got ep.Connect(%+v) = %s, want = %s", dstAddr, err, tcpip.ErrNoRoute)
+			{
+				err := ep.Connect(dstAddr)
+				if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+					t.Errorf("got ep.Connect(%+v) = %s, want = %s", dstAddr, err, &tcpip.ErrNoRoute{})
+				}
 			}
 		})
 	}
diff --git a/pkg/tcpip/stack/neighbor_cache.go b/pkg/tcpip/stack/neighbor_cache.go
index eea32dcf5..88a3ff776 100644
--- a/pkg/tcpip/stack/neighbor_cache.go
+++ b/pkg/tcpip/stack/neighbor_cache.go
@@ -126,7 +126,7 @@ func (n *neighborCache) getOrCreateEntry(remoteAddr tcpip.Address, linkRes LinkA
 // packet prompting NUD/link address resolution.
 //
 // TODO(gvisor.dev/issue/5151): Don't return the neighbor entry.
-func (n *neighborCache) entry(remoteAddr, localAddr tcpip.Address, linkRes LinkAddressResolver, onResolve func(LinkResolutionResult)) (NeighborEntry, <-chan struct{}, *tcpip.Error) {
+func (n *neighborCache) entry(remoteAddr, localAddr tcpip.Address, linkRes LinkAddressResolver, onResolve func(LinkResolutionResult)) (NeighborEntry, <-chan struct{}, tcpip.Error) {
 	entry := n.getOrCreateEntry(remoteAddr, linkRes)
 	entry.mu.Lock()
 	defer entry.mu.Unlock()
@@ -154,7 +154,7 @@ func (n *neighborCache) entry(remoteAddr, localAddr tcpip.Address, linkRes LinkA
 			entry.done = make(chan struct{})
 		}
 		entry.handlePacketQueuedLocked(localAddr)
-		return entry.neigh, entry.done, tcpip.ErrWouldBlock
+		return entry.neigh, entry.done, &tcpip.ErrWouldBlock{}
 	default:
 		panic(fmt.Sprintf("Invalid cache entry state: %s", s))
 	}
diff --git a/pkg/tcpip/stack/neighbor_cache_test.go b/pkg/tcpip/stack/neighbor_cache_test.go
index dbdb51bb4..2870e4f66 100644
--- a/pkg/tcpip/stack/neighbor_cache_test.go
+++ b/pkg/tcpip/stack/neighbor_cache_test.go
@@ -194,7 +194,7 @@ type testNeighborResolver struct {
 
 var _ LinkAddressResolver = (*testNeighborResolver)(nil)
 
-func (r *testNeighborResolver) LinkAddressRequest(targetAddr, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) *tcpip.Error {
+func (r *testNeighborResolver) LinkAddressRequest(targetAddr, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) tcpip.Error {
 	if !r.dropReplies {
 		// Delay handling the request to emulate network latency.
 		r.clock.AfterFunc(r.delay, func() {
@@ -295,8 +295,9 @@ func TestNeighborCacheEntry(t *testing.T) {
 	if !ok {
 		t.Fatal("store.entry(0) not found")
 	}
-	if _, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := neigh.entry(entry.Addr, "", linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 
 	clock.Advance(typicalLatency)
@@ -359,8 +360,9 @@ func TestNeighborCacheRemoveEntry(t *testing.T) {
 		t.Fatal("store.entry(0) not found")
 	}
 
-	if _, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := neigh.entry(entry.Addr, "", linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 
 	clock.Advance(typicalLatency)
@@ -414,8 +416,11 @@ func TestNeighborCacheRemoveEntry(t *testing.T) {
 		}
 	}
 
-	if _, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	{
+		_, _, err := neigh.entry(entry.Addr, "", linkRes, nil)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
+		}
 	}
 }
 
@@ -462,8 +467,9 @@ func (c *testContext) overflowCache(opts overflowOptions) error {
 		if !ok {
 			return fmt.Errorf("c.store.entry(%d) not found", i)
 		}
-		if _, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil); err != tcpip.ErrWouldBlock {
-			return fmt.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		_, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			return fmt.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		c.clock.Advance(c.neigh.config().RetransmitTimer)
 
@@ -579,8 +585,9 @@ func TestNeighborCacheRemoveEntryThenOverflow(t *testing.T) {
 	if !ok {
 		t.Fatal("c.store.entry(0) not found")
 	}
-	if _, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	c.clock.Advance(c.neigh.config().RetransmitTimer)
 	wantEvents := []testEntryEventInfo{
@@ -830,8 +837,9 @@ func TestNeighborCacheOverwriteWithStaticEntryThenOverflow(t *testing.T) {
 	if !ok {
 		t.Fatal("c.store.entry(0) not found")
 	}
-	if _, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	c.clock.Advance(typicalLatency)
 	wantEvents := []testEntryEventInfo{
@@ -989,8 +997,9 @@ func TestNeighborCacheClear(t *testing.T) {
 	if !ok {
 		t.Fatal("store.entry(0) not found")
 	}
-	if _, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := neigh.entry(entry.Addr, "", linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	clock.Advance(typicalLatency)
 
@@ -1094,8 +1103,9 @@ func TestNeighborCacheClearThenOverflow(t *testing.T) {
 	if !ok {
 		t.Fatal("c.store.entry(0) not found")
 	}
-	if _, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil); err != tcpip.ErrWouldBlock {
-		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	_, _, err := c.neigh.entry(entry.Addr, "", c.linkRes, nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Errorf("got c.neigh.entry(%s, '', _, nil, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	c.clock.Advance(typicalLatency)
 	wantEvents := []testEntryEventInfo{
@@ -1193,8 +1203,8 @@ func TestNeighborCacheKeepFrequentlyUsed(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Errorf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Errorf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		clock.Advance(typicalLatency)
 		select {
@@ -1249,8 +1259,8 @@ func TestNeighborCacheKeepFrequentlyUsed(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Errorf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Errorf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		clock.Advance(typicalLatency)
 		select {
@@ -1360,8 +1370,10 @@ func TestNeighborCacheConcurrent(t *testing.T) {
 			wg.Add(1)
 			go func(entry NeighborEntry) {
 				defer wg.Done()
-				if e, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err != nil && err != tcpip.ErrWouldBlock {
-					t.Errorf("got neigh.entry(%s, '', _, nil, nil) = (%+v, _, %s), want (_, _, nil) or (_, _, %s)", entry.Addr, e, err, tcpip.ErrWouldBlock)
+				switch e, _, err := neigh.entry(entry.Addr, "", linkRes, nil); err.(type) {
+				case nil, *tcpip.ErrWouldBlock:
+				default:
+					t.Errorf("got neigh.entry(%s, '', _, nil, nil) = (%+v, _, %s), want (_, _, nil) or (_, _, %s)", entry.Addr, e, err, &tcpip.ErrWouldBlock{})
 				}
 			}(entry)
 		}
@@ -1422,8 +1434,8 @@ func TestNeighborCacheReplace(t *testing.T) {
 			t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 		}
 	})
-	if err != tcpip.ErrWouldBlock {
-		t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	clock.Advance(typicalLatency)
 	select {
@@ -1535,8 +1547,8 @@ func TestNeighborCacheResolutionFailed(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		clock.Advance(typicalLatency)
 		select {
@@ -1569,8 +1581,8 @@ func TestNeighborCacheResolutionFailed(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		waitFor := config.DelayFirstProbeTime + typicalLatency*time.Duration(config.MaxMulticastProbes)
 		clock.Advance(waitFor)
@@ -1614,8 +1626,8 @@ func TestNeighborCacheResolutionTimeout(t *testing.T) {
 			t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 		}
 	})
-	if err != tcpip.ErrWouldBlock {
-		t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 	}
 	waitFor := config.RetransmitTimer * time.Duration(config.MaxMulticastProbes)
 	clock.Advance(waitFor)
@@ -1655,8 +1667,8 @@ func TestNeighborCacheRetryResolution(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		waitFor := config.RetransmitTimer * time.Duration(config.MaxMulticastProbes)
 		clock.Advance(waitFor)
@@ -1688,8 +1700,8 @@ func TestNeighborCacheRetryResolution(t *testing.T) {
 				t.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 			}
 		})
-		if err != tcpip.ErrWouldBlock {
-			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+		if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+			t.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 		}
 		if incompleteEntry.State != Incomplete {
 			t.Fatalf("got entry.State = %s, want = %s", incompleteEntry.State, Incomplete)
@@ -1747,8 +1759,8 @@ func BenchmarkCacheClear(b *testing.B) {
 					b.Fatalf("got link resolution result mismatch (-want +got):\n%s", diff)
 				}
 			})
-			if err != tcpip.ErrWouldBlock {
-				b.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, tcpip.ErrWouldBlock)
+			if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				b.Fatalf("got neigh.entry(%s, '', _, _, nil) = %v, want = %s", entry.Addr, err, &tcpip.ErrWouldBlock{})
 			}
 
 			select {
diff --git a/pkg/tcpip/stack/neighbor_entry_test.go b/pkg/tcpip/stack/neighbor_entry_test.go
index 3b05bcf15..140b8ca00 100644
--- a/pkg/tcpip/stack/neighbor_entry_test.go
+++ b/pkg/tcpip/stack/neighbor_entry_test.go
@@ -193,7 +193,7 @@ func (p entryTestProbeInfo) String() string {
 
 // LinkAddressRequest sends a request for the LinkAddress of addr. Broadcasts
 // to the local network if linkAddr is the zero value.
-func (r *entryTestLinkResolver) LinkAddressRequest(targetAddr, localAddr tcpip.Address, linkAddr tcpip.LinkAddress, _ NetworkInterface) *tcpip.Error {
+func (r *entryTestLinkResolver) LinkAddressRequest(targetAddr, localAddr tcpip.Address, linkAddr tcpip.LinkAddress, _ NetworkInterface) tcpip.Error {
 	p := entryTestProbeInfo{
 		RemoteAddress:     targetAddr,
 		RemoteLinkAddress: linkAddr,
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index f59416fd3..16e55085d 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -231,7 +231,9 @@ func (n *NIC) disableLocked() {
 	//
 	// This matches linux's behaviour at the time of writing:
 	// https://github.com/torvalds/linux/blob/71c061d2443814de15e177489d5cc00a4a253ef3/net/core/neighbour.c#L371
-	if err := n.clearNeighbors(); err != nil && err != tcpip.ErrNotSupported {
+	switch err := n.clearNeighbors(); err.(type) {
+	case nil, *tcpip.ErrNotSupported:
+	default:
 		panic(fmt.Sprintf("n.clearNeighbors(): %s", err))
 	}
 
@@ -246,7 +248,7 @@ func (n *NIC) disableLocked() {
 // address (ff02::1), start DAD for permanent addresses, and start soliciting
 // routers if the stack is not operating as a router. If the stack is also
 // configured to auto-generate a link-local address, one will be generated.
-func (n *NIC) enable() *tcpip.Error {
+func (n *NIC) enable() tcpip.Error {
 	n.mu.Lock()
 	defer n.mu.Unlock()
 
@@ -266,7 +268,7 @@ func (n *NIC) enable() *tcpip.Error {
 // remove detaches NIC from the link endpoint and releases network endpoint
 // resources. This guarantees no packets between this NIC and the network
 // stack.
-func (n *NIC) remove() *tcpip.Error {
+func (n *NIC) remove() tcpip.Error {
 	n.mu.Lock()
 	defer n.mu.Unlock()
 
@@ -302,11 +304,12 @@ func (n *NIC) IsLoopback() bool {
 }
 
 // WritePacket implements NetworkLinkEndpoint.
-func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) *tcpip.Error {
+func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	_, err := n.enqueuePacketBuffer(r, gso, protocol, pkt)
 	return err
 }
-func (n *NIC) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
+
+func (n *NIC) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	// As per relevant RFCs, we should queue packets while we wait for link
 	// resolution to complete.
 	//
@@ -328,14 +331,14 @@ func (n *NIC) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProt
 }
 
 // WritePacketToRemote implements NetworkInterface.
-func (n *NIC) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) *tcpip.Error {
+func (n *NIC) WritePacketToRemote(remoteLinkAddr tcpip.LinkAddress, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	var r RouteInfo
 	r.NetProto = protocol
 	r.RemoteLinkAddress = remoteLinkAddr
 	return n.writePacket(r, gso, protocol, pkt)
 }
 
-func (n *NIC) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) *tcpip.Error {
+func (n *NIC) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) tcpip.Error {
 	// WritePacket takes ownership of pkt, calculate numBytes first.
 	numBytes := pkt.Size()
 
@@ -352,11 +355,11 @@ func (n *NIC) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolN
 }
 
 // WritePackets implements NetworkLinkEndpoint.
-func (n *NIC) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+func (n *NIC) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
 	return n.enqueuePacketBuffer(r, gso, protocol, &pkts)
 }
 
-func (n *NIC) writePackets(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, *tcpip.Error) {
+func (n *NIC) writePackets(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, tcpip.Error) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		pkt.EgressRoute = r
 		pkt.GSOOptions = gso
@@ -472,15 +475,15 @@ func (n *NIC) getAddressOrCreateTempInner(protocol tcpip.NetworkProtocolNumber,
 
 // addAddress adds a new address to n, so that it starts accepting packets
 // targeted at the given address (and network protocol).
-func (n *NIC) addAddress(protocolAddress tcpip.ProtocolAddress, peb PrimaryEndpointBehavior) *tcpip.Error {
+func (n *NIC) addAddress(protocolAddress tcpip.ProtocolAddress, peb PrimaryEndpointBehavior) tcpip.Error {
 	ep, ok := n.networkEndpoints[protocolAddress.Protocol]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 
 	addressableEndpoint, ok := ep.(AddressableEndpoint)
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	addressEndpoint, err := addressableEndpoint.AddAndAcquirePermanentAddress(protocolAddress.AddressWithPrefix, peb, AddressConfigStatic, false /* deprecated */)
@@ -544,21 +547,22 @@ func (n *NIC) primaryAddress(proto tcpip.NetworkProtocolNumber) tcpip.AddressWit
 }
 
 // removeAddress removes an address from n.
-func (n *NIC) removeAddress(addr tcpip.Address) *tcpip.Error {
+func (n *NIC) removeAddress(addr tcpip.Address) tcpip.Error {
 	for _, ep := range n.networkEndpoints {
 		addressableEndpoint, ok := ep.(AddressableEndpoint)
 		if !ok {
 			continue
 		}
 
-		if err := addressableEndpoint.RemovePermanentAddress(addr); err == tcpip.ErrBadLocalAddress {
+		switch err := addressableEndpoint.RemovePermanentAddress(addr); err.(type) {
+		case *tcpip.ErrBadLocalAddress:
 			continue
-		} else {
+		default:
 			return err
 		}
 	}
 
-	return tcpip.ErrBadLocalAddress
+	return &tcpip.ErrBadLocalAddress{}
 }
 
 func (n *NIC) confirmReachable(addr tcpip.Address) {
@@ -567,7 +571,7 @@ func (n *NIC) confirmReachable(addr tcpip.Address) {
 	}
 }
 
-func (n *NIC) getNeighborLinkAddress(addr, localAddr tcpip.Address, linkRes LinkAddressResolver, onResolve func(LinkResolutionResult)) (tcpip.LinkAddress, <-chan struct{}, *tcpip.Error) {
+func (n *NIC) getNeighborLinkAddress(addr, localAddr tcpip.Address, linkRes LinkAddressResolver, onResolve func(LinkResolutionResult)) (tcpip.LinkAddress, <-chan struct{}, tcpip.Error) {
 	if n.neigh != nil {
 		entry, ch, err := n.neigh.entry(addr, localAddr, linkRes, onResolve)
 		return entry.LinkAddr, ch, err
@@ -576,37 +580,37 @@ func (n *NIC) getNeighborLinkAddress(addr, localAddr tcpip.Address, linkRes Link
 	return n.linkAddrCache.get(addr, linkRes, localAddr, n, onResolve)
 }
 
-func (n *NIC) neighbors() ([]NeighborEntry, *tcpip.Error) {
+func (n *NIC) neighbors() ([]NeighborEntry, tcpip.Error) {
 	if n.neigh == nil {
-		return nil, tcpip.ErrNotSupported
+		return nil, &tcpip.ErrNotSupported{}
 	}
 
 	return n.neigh.entries(), nil
 }
 
-func (n *NIC) addStaticNeighbor(addr tcpip.Address, linkAddress tcpip.LinkAddress) *tcpip.Error {
+func (n *NIC) addStaticNeighbor(addr tcpip.Address, linkAddress tcpip.LinkAddress) tcpip.Error {
 	if n.neigh == nil {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	n.neigh.addStaticEntry(addr, linkAddress)
 	return nil
 }
 
-func (n *NIC) removeNeighbor(addr tcpip.Address) *tcpip.Error {
+func (n *NIC) removeNeighbor(addr tcpip.Address) tcpip.Error {
 	if n.neigh == nil {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	if !n.neigh.removeEntry(addr) {
-		return tcpip.ErrBadAddress
+		return &tcpip.ErrBadAddress{}
 	}
 	return nil
 }
 
-func (n *NIC) clearNeighbors() *tcpip.Error {
+func (n *NIC) clearNeighbors() tcpip.Error {
 	if n.neigh == nil {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	n.neigh.clear()
@@ -615,7 +619,7 @@ func (n *NIC) clearNeighbors() *tcpip.Error {
 
 // joinGroup adds a new endpoint for the given multicast address, if none
 // exists yet. Otherwise it just increments its count.
-func (n *NIC) joinGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) *tcpip.Error {
+func (n *NIC) joinGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) tcpip.Error {
 	// TODO(b/143102137): When implementing MLD, make sure MLD packets are
 	// not sent unless a valid link-local address is available for use on n
 	// as an MLD packet's source address must be a link-local address as
@@ -623,12 +627,12 @@ func (n *NIC) joinGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address
 
 	ep, ok := n.networkEndpoints[protocol]
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	gep, ok := ep.(GroupAddressableEndpoint)
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	return gep.JoinGroup(addr)
@@ -636,15 +640,15 @@ func (n *NIC) joinGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address
 
 // leaveGroup decrements the count for the given multicast address, and when it
 // reaches zero removes the endpoint for this address.
-func (n *NIC) leaveGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) *tcpip.Error {
+func (n *NIC) leaveGroup(protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) tcpip.Error {
 	ep, ok := n.networkEndpoints[protocol]
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	gep, ok := ep.(GroupAddressableEndpoint)
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	return gep.LeaveGroup(addr)
@@ -894,9 +898,9 @@ func (n *NIC) Name() string {
 }
 
 // nudConfigs gets the NUD configurations for n.
-func (n *NIC) nudConfigs() (NUDConfigurations, *tcpip.Error) {
+func (n *NIC) nudConfigs() (NUDConfigurations, tcpip.Error) {
 	if n.neigh == nil {
-		return NUDConfigurations{}, tcpip.ErrNotSupported
+		return NUDConfigurations{}, &tcpip.ErrNotSupported{}
 	}
 	return n.neigh.config(), nil
 }
@@ -905,22 +909,22 @@ func (n *NIC) nudConfigs() (NUDConfigurations, *tcpip.Error) {
 //
 // Note, if c contains invalid NUD configuration values, it will be fixed to
 // use default values for the erroneous values.
-func (n *NIC) setNUDConfigs(c NUDConfigurations) *tcpip.Error {
+func (n *NIC) setNUDConfigs(c NUDConfigurations) tcpip.Error {
 	if n.neigh == nil {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 	c.resetInvalidFields()
 	n.neigh.setConfig(c)
 	return nil
 }
 
-func (n *NIC) registerPacketEndpoint(netProto tcpip.NetworkProtocolNumber, ep PacketEndpoint) *tcpip.Error {
+func (n *NIC) registerPacketEndpoint(netProto tcpip.NetworkProtocolNumber, ep PacketEndpoint) tcpip.Error {
 	n.mu.Lock()
 	defer n.mu.Unlock()
 
 	eps, ok := n.mu.packetEPs[netProto]
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 	eps.add(ep)
 
diff --git a/pkg/tcpip/stack/nic_test.go b/pkg/tcpip/stack/nic_test.go
index be5df7b01..2f719fbe5 100644
--- a/pkg/tcpip/stack/nic_test.go
+++ b/pkg/tcpip/stack/nic_test.go
@@ -39,7 +39,7 @@ type testIPv6Endpoint struct {
 	invalidatedRtr tcpip.Address
 }
 
-func (*testIPv6Endpoint) Enable() *tcpip.Error {
+func (*testIPv6Endpoint) Enable() tcpip.Error {
 	return nil
 }
 
@@ -65,21 +65,21 @@ func (e *testIPv6Endpoint) MaxHeaderLength() uint16 {
 }
 
 // WritePacket implements NetworkEndpoint.WritePacket.
-func (*testIPv6Endpoint) WritePacket(*Route, *GSO, NetworkHeaderParams, *PacketBuffer) *tcpip.Error {
+func (*testIPv6Endpoint) WritePacket(*Route, *GSO, NetworkHeaderParams, *PacketBuffer) tcpip.Error {
 	return nil
 }
 
 // WritePackets implements NetworkEndpoint.WritePackets.
-func (*testIPv6Endpoint) WritePackets(*Route, *GSO, PacketBufferList, NetworkHeaderParams) (int, *tcpip.Error) {
+func (*testIPv6Endpoint) WritePackets(*Route, *GSO, PacketBufferList, NetworkHeaderParams) (int, tcpip.Error) {
 	// Our tests don't use this so we don't support it.
-	return 0, tcpip.ErrNotSupported
+	return 0, &tcpip.ErrNotSupported{}
 }
 
 // WriteHeaderIncludedPacket implements
 // NetworkEndpoint.WriteHeaderIncludedPacket.
-func (*testIPv6Endpoint) WriteHeaderIncludedPacket(*Route, *PacketBuffer) *tcpip.Error {
+func (*testIPv6Endpoint) WriteHeaderIncludedPacket(*Route, *PacketBuffer) tcpip.Error {
 	// Our tests don't use this so we don't support it.
-	return tcpip.ErrNotSupported
+	return &tcpip.ErrNotSupported{}
 }
 
 // HandlePacket implements NetworkEndpoint.HandlePacket.
@@ -149,12 +149,12 @@ func (p *testIPv6Protocol) NewEndpoint(nic NetworkInterface, _ LinkAddressCache,
 }
 
 // SetOption implements NetworkProtocol.SetOption.
-func (*testIPv6Protocol) SetOption(tcpip.SettableNetworkProtocolOption) *tcpip.Error {
+func (*testIPv6Protocol) SetOption(tcpip.SettableNetworkProtocolOption) tcpip.Error {
 	return nil
 }
 
 // Option implements NetworkProtocol.Option.
-func (*testIPv6Protocol) Option(tcpip.GettableNetworkProtocolOption) *tcpip.Error {
+func (*testIPv6Protocol) Option(tcpip.GettableNetworkProtocolOption) tcpip.Error {
 	return nil
 }
 
@@ -175,7 +175,7 @@ func (*testIPv6Protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
 }
 
 // LinkAddressRequest implements LinkAddressResolver.
-func (*testIPv6Protocol) LinkAddressRequest(_, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) *tcpip.Error {
+func (*testIPv6Protocol) LinkAddressRequest(_, _ tcpip.Address, _ tcpip.LinkAddress, _ NetworkInterface) tcpip.Error {
 	return nil
 }
 
diff --git a/pkg/tcpip/stack/nud_test.go b/pkg/tcpip/stack/nud_test.go
index 7bca1373e..ebfd5eb45 100644
--- a/pkg/tcpip/stack/nud_test.go
+++ b/pkg/tcpip/stack/nud_test.go
@@ -65,8 +65,9 @@ func TestSetNUDConfigurationFailsForBadNICID(t *testing.T) {
 
 	// No NIC with ID 1 yet.
 	config := stack.NUDConfigurations{}
-	if err := s.SetNUDConfigurations(1, config); err != tcpip.ErrUnknownNICID {
-		t.Fatalf("got s.SetNDPConfigurations(1, %+v) = %v, want = %s", config, err, tcpip.ErrUnknownNICID)
+	err := s.SetNUDConfigurations(1, config)
+	if _, ok := err.(*tcpip.ErrUnknownNICID); !ok {
+		t.Fatalf("got s.SetNDPConfigurations(1, %+v) = %v, want = %s", config, err, &tcpip.ErrUnknownNICID{})
 	}
 }
 
@@ -90,8 +91,9 @@ func TestNUDConfigurationFailsForNotSupported(t *testing.T) {
 	if err := s.CreateNIC(nicID, e); err != nil {
 		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
 	}
-	if _, err := s.NUDConfigurations(nicID); err != tcpip.ErrNotSupported {
-		t.Fatalf("got s.NDPConfigurations(%d) = %v, want = %s", nicID, err, tcpip.ErrNotSupported)
+	_, err := s.NUDConfigurations(nicID)
+	if _, ok := err.(*tcpip.ErrNotSupported); !ok {
+		t.Fatalf("got s.NDPConfigurations(%d) = %v, want = %s", nicID, err, &tcpip.ErrNotSupported{})
 	}
 }
 
@@ -117,8 +119,9 @@ func TestSetNUDConfigurationFailsForNotSupported(t *testing.T) {
 	}
 
 	config := stack.NUDConfigurations{}
-	if err := s.SetNUDConfigurations(nicID, config); err != tcpip.ErrNotSupported {
-		t.Fatalf("got s.SetNDPConfigurations(%d, %+v) = %v, want = %s", nicID, config, err, tcpip.ErrNotSupported)
+	err := s.SetNUDConfigurations(nicID, config)
+	if _, ok := err.(*tcpip.ErrNotSupported); !ok {
+		t.Fatalf("got s.SetNDPConfigurations(%d, %+v) = %v, want = %s", nicID, config, err, &tcpip.ErrNotSupported{})
 	}
 }
 
diff --git a/pkg/tcpip/stack/pending_packets.go b/pkg/tcpip/stack/pending_packets.go
index c4769b17e..c6adfb27b 100644
--- a/pkg/tcpip/stack/pending_packets.go
+++ b/pkg/tcpip/stack/pending_packets.go
@@ -114,7 +114,7 @@ func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpi
 	}
 }
 
-func (f *packetsPendingLinkResolution) writePacketBuffer(r RouteInfo, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
+func (f *packetsPendingLinkResolution) writePacketBuffer(r RouteInfo, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	switch pkt := pkt.(type) {
 	case *PacketBuffer:
 		if err := f.nic.writePacket(r, gso, proto, pkt); err != nil {
@@ -133,7 +133,7 @@ func (f *packetsPendingLinkResolution) writePacketBuffer(r RouteInfo, gso *GSO,
 // If the maximum number of pending resolutions is reached, the packets
 // associated with the oldest link resolution will be dequeued as if they failed
 // link resolution.
-func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
+func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
 	f.mu.Lock()
 	// Make sure we attempt resolution while holding f's lock so that we avoid
 	// a race where link resolution completes before we enqueue the packets.
@@ -146,13 +146,13 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
 	// To make sure B does not interleave with A and C, we make sure A and C are
 	// done while holding the lock.
 	routeInfo, ch, err := r.resolvedFields(nil)
-	switch err {
+	switch err.(type) {
 	case nil:
 		// The route resolved immediately, so we don't need to wait for link
 		// resolution to send the packet.
 		f.mu.Unlock()
 		return f.writePacketBuffer(routeInfo, gso, proto, pkt)
-	case tcpip.ErrWouldBlock:
+	case *tcpip.ErrWouldBlock:
 		// We need to wait for link resolution to complete.
 	default:
 		f.mu.Unlock()
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 33df192aa..510da8689 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -172,10 +172,10 @@ type TransportProtocol interface {
 	Number() tcpip.TransportProtocolNumber
 
 	// NewEndpoint creates a new endpoint of the transport protocol.
-	NewEndpoint(netProto tcpip.NetworkProtocolNumber, waitQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error)
+	NewEndpoint(netProto tcpip.NetworkProtocolNumber, waitQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error)
 
 	// NewRawEndpoint creates a new raw endpoint of the transport protocol.
-	NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waitQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error)
+	NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waitQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error)
 
 	// MinimumPacketSize returns the minimum valid packet size of this
 	// transport protocol. The stack automatically drops any packets smaller
@@ -184,7 +184,7 @@ type TransportProtocol interface {
 
 	// ParsePorts returns the source and destination ports stored in a
 	// packet of this protocol.
-	ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error)
+	ParsePorts(v buffer.View) (src, dst uint16, err tcpip.Error)
 
 	// HandleUnknownDestinationPacket handles packets targeted at this
 	// protocol that don't match any existing endpoint. For example,
@@ -197,12 +197,12 @@ type TransportProtocol interface {
 	// SetOption allows enabling/disabling protocol specific features.
 	// SetOption returns an error if the option is not supported or the
 	// provided option value is invalid.
-	SetOption(option tcpip.SettableTransportProtocolOption) *tcpip.Error
+	SetOption(option tcpip.SettableTransportProtocolOption) tcpip.Error
 
 	// Option allows retrieving protocol specific option values.
 	// Option returns an error if the option is not supported or the
 	// provided option value is invalid.
-	Option(option tcpip.GettableTransportProtocolOption) *tcpip.Error
+	Option(option tcpip.GettableTransportProtocolOption) tcpip.Error
 
 	// Close requests that any worker goroutines owned by the protocol
 	// stop.
@@ -289,10 +289,10 @@ type NetworkHeaderParams struct {
 // endpoints may associate themselves with the same identifier (group address).
 type GroupAddressableEndpoint interface {
 	// JoinGroup joins the specified group.
-	JoinGroup(group tcpip.Address) *tcpip.Error
+	JoinGroup(group tcpip.Address) tcpip.Error
 
 	// LeaveGroup attempts to leave the specified group.
-	LeaveGroup(group tcpip.Address) *tcpip.Error
+	LeaveGroup(group tcpip.Address) tcpip.Error
 
 	// IsInGroup returns true if the endpoint is a member of the specified group.
 	IsInGroup(group tcpip.Address) bool
@@ -440,17 +440,17 @@ func (k AddressKind) IsPermanent() bool {
 type AddressableEndpoint interface {
 	// AddAndAcquirePermanentAddress adds the passed permanent address.
 	//
-	// Returns tcpip.ErrDuplicateAddress if the address exists.
+	// Returns *tcpip.ErrDuplicateAddress if the address exists.
 	//
 	// Acquires and returns the AddressEndpoint for the added address.
-	AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated bool) (AddressEndpoint, *tcpip.Error)
+	AddAndAcquirePermanentAddress(addr tcpip.AddressWithPrefix, peb PrimaryEndpointBehavior, configType AddressConfigType, deprecated bool) (AddressEndpoint, tcpip.Error)
 
 	// RemovePermanentAddress removes the passed address if it is a permanent
 	// address.
 	//
-	// Returns tcpip.ErrBadLocalAddress if the endpoint does not have the passed
+	// Returns *tcpip.ErrBadLocalAddress if the endpoint does not have the passed
 	// permanent address.
-	RemovePermanentAddress(addr tcpip.Address) *tcpip.Error
+	RemovePermanentAddress(addr tcpip.Address) tcpip.Error
 
 	// MainAddress returns the endpoint's primary permanent address.
 	MainAddress() tcpip.AddressWithPrefix
@@ -512,14 +512,14 @@ type NetworkInterface interface {
 	Promiscuous() bool
 
 	// WritePacketToRemote writes the packet to the given remote link address.
-	WritePacketToRemote(tcpip.LinkAddress, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) *tcpip.Error
+	WritePacketToRemote(tcpip.LinkAddress, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePacket writes a packet with the given protocol through the given
 	// route.
 	//
 	// WritePacket takes ownership of the packet buffer. The packet buffer's
 	// network and transport header must be set.
-	WritePacket(*Route, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) *tcpip.Error
+	WritePacket(*Route, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol through the given
 	// route. Must not be called with an empty list of packet buffers.
@@ -529,7 +529,7 @@ type NetworkInterface interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(*Route, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error)
+	WritePackets(*Route, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 }
 
 // LinkResolvableNetworkEndpoint handles link resolution events.
@@ -547,8 +547,8 @@ type NetworkEndpoint interface {
 	// Must only be called when the stack is in a state that allows the endpoint
 	// to send and receive packets.
 	//
-	// Returns tcpip.ErrNotPermitted if the endpoint cannot be enabled.
-	Enable() *tcpip.Error
+	// Returns *tcpip.ErrNotPermitted if the endpoint cannot be enabled.
+	Enable() tcpip.Error
 
 	// Enabled returns true if the endpoint is enabled.
 	Enabled() bool
@@ -574,16 +574,16 @@ type NetworkEndpoint interface {
 	// WritePacket writes a packet to the given destination address and
 	// protocol. It takes ownership of pkt. pkt.TransportHeader must have
 	// already been set.
-	WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) *tcpip.Error
+	WritePacket(r *Route, gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets to the given destination address and
 	// protocol. pkts must not be zero length. It takes ownership of pkts and
 	// underlying packets.
-	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, *tcpip.Error)
+	WritePackets(r *Route, gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error)
 
 	// WriteHeaderIncludedPacket writes a packet that includes a network
 	// header to the given destination address. It takes ownership of pkt.
-	WriteHeaderIncludedPacket(r *Route, pkt *PacketBuffer) *tcpip.Error
+	WriteHeaderIncludedPacket(r *Route, pkt *PacketBuffer) tcpip.Error
 
 	// HandlePacket is called by the link layer when new packets arrive to
 	// this network endpoint. It sets pkt.NetworkHeader.
@@ -654,12 +654,12 @@ type NetworkProtocol interface {
 	// SetOption allows enabling/disabling protocol specific features.
 	// SetOption returns an error if the option is not supported or the
 	// provided option value is invalid.
-	SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error
+	SetOption(option tcpip.SettableNetworkProtocolOption) tcpip.Error
 
 	// Option allows retrieving protocol specific option values.
 	// Option returns an error if the option is not supported or the
 	// provided option value is invalid.
-	Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error
+	Option(option tcpip.GettableNetworkProtocolOption) tcpip.Error
 
 	// Close requests that any worker goroutines owned by the protocol
 	// stop.
@@ -796,7 +796,7 @@ type LinkEndpoint interface {
 	// To participate in transparent bridging, a LinkEndpoint implementation
 	// should call eth.Encode with header.EthernetFields.SrcAddr set to
 	// r.LocalLinkAddress if it is provided.
-	WritePacket(RouteInfo, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) *tcpip.Error
+	WritePacket(RouteInfo, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) tcpip.Error
 
 	// WritePackets writes packets with the given protocol and route. Must not be
 	// called with an empty list of packet buffers.
@@ -806,7 +806,7 @@ type LinkEndpoint interface {
 	// Right now, WritePackets is used only when the software segmentation
 	// offload is enabled. If it will be used for something else, syscall filters
 	// may need to be updated.
-	WritePackets(RouteInfo, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error)
+	WritePackets(RouteInfo, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error)
 }
 
 // InjectableLinkEndpoint is a LinkEndpoint where inbound packets are
@@ -821,7 +821,7 @@ type InjectableLinkEndpoint interface {
 	// link.
 	//
 	// dest is used by endpoints with multiple raw destinations.
-	InjectOutbound(dest tcpip.Address, packet []byte) *tcpip.Error
+	InjectOutbound(dest tcpip.Address, packet []byte) tcpip.Error
 }
 
 // A LinkAddressResolver is an extension to a NetworkProtocol that
@@ -833,7 +833,7 @@ type LinkAddressResolver interface {
 	//
 	// The request is sent from the passed network interface. If the interface
 	// local address is unspecified, any interface local address may be used.
-	LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic NetworkInterface) *tcpip.Error
+	LinkAddressRequest(targetAddr, localAddr tcpip.Address, remoteLinkAddr tcpip.LinkAddress, nic NetworkInterface) tcpip.Error
 
 	// ResolveStaticAddress attempts to resolve address without sending
 	// requests. It either resolves the name immediately or returns the
@@ -858,11 +858,11 @@ type RawFactory interface {
 	// NewUnassociatedEndpoint produces endpoints for writing packets not
 	// associated with a particular transport protocol. Such endpoints can
 	// be used to write arbitrary packets that include the network header.
-	NewUnassociatedEndpoint(stack *Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error)
+	NewUnassociatedEndpoint(stack *Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error)
 
 	// NewPacketEndpoint produces endpoints for reading and writing packets
 	// that include network and (when cooked is false) link layer headers.
-	NewPacketEndpoint(stack *Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error)
+	NewPacketEndpoint(stack *Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error)
 }
 
 // GSOType is the type of GSO segments.
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 9c8c155fa..4ae0f2a1a 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -331,7 +331,7 @@ type ResolvedFieldsResult struct {
 //
 // Note, the route will not cache the remote link address when address
 // resolution completes.
-func (r *Route) ResolvedFields(afterResolve func(ResolvedFieldsResult)) *tcpip.Error {
+func (r *Route) ResolvedFields(afterResolve func(ResolvedFieldsResult)) tcpip.Error {
 	_, _, err := r.resolvedFields(afterResolve)
 	return err
 }
@@ -342,7 +342,7 @@ func (r *Route) ResolvedFields(afterResolve func(ResolvedFieldsResult)) *tcpip.E
 //
 // The route's fields will also be returned, regardless of whether address
 // resolution is required or not.
-func (r *Route) resolvedFields(afterResolve func(ResolvedFieldsResult)) (RouteInfo, <-chan struct{}, *tcpip.Error) {
+func (r *Route) resolvedFields(afterResolve func(ResolvedFieldsResult)) (RouteInfo, <-chan struct{}, tcpip.Error) {
 	r.mu.RLock()
 	fields := r.fieldsLocked()
 	resolutionRequired := r.isResolutionRequiredRLocked()
@@ -429,9 +429,9 @@ func (r *Route) isValidForOutgoingRLocked() bool {
 }
 
 // WritePacket writes the packet through the given route.
-func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) *tcpip.Error {
+func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuffer) tcpip.Error {
 	if !r.isValidForOutgoing() {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	return r.outgoingNIC.getNetworkEndpoint(r.NetProto).WritePacket(r, gso, params, pkt)
@@ -439,9 +439,9 @@ func (r *Route) WritePacket(gso *GSO, params NetworkHeaderParams, pkt *PacketBuf
 
 // WritePackets writes a list of n packets through the given route and returns
 // the number of packets written.
-func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, *tcpip.Error) {
+func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHeaderParams) (int, tcpip.Error) {
 	if !r.isValidForOutgoing() {
-		return 0, tcpip.ErrInvalidEndpointState
+		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	return r.outgoingNIC.getNetworkEndpoint(r.NetProto).WritePackets(r, gso, pkts, params)
@@ -449,9 +449,9 @@ func (r *Route) WritePackets(gso *GSO, pkts PacketBufferList, params NetworkHead
 
 // WriteHeaderIncludedPacket writes a packet already containing a network
 // header through the given route.
-func (r *Route) WriteHeaderIncludedPacket(pkt *PacketBuffer) *tcpip.Error {
+func (r *Route) WriteHeaderIncludedPacket(pkt *PacketBuffer) tcpip.Error {
 	if !r.isValidForOutgoing() {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	return r.outgoingNIC.getNetworkEndpoint(r.NetProto).WriteHeaderIncludedPacket(r, pkt)
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index e9c5db4c3..e56183e71 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -552,7 +552,7 @@ type TransportEndpointInfo struct {
 // incompatible with the receiver.
 //
 // Preconditon: the parent endpoint mu must be held while calling this method.
-func (t *TransportEndpointInfo) AddrNetProtoLocked(addr tcpip.FullAddress, v6only bool) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+func (t *TransportEndpointInfo) AddrNetProtoLocked(addr tcpip.FullAddress, v6only bool) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, tcpip.Error) {
 	netProto := t.NetProto
 	switch len(addr.Addr) {
 	case header.IPv4AddressSize:
@@ -570,11 +570,11 @@ func (t *TransportEndpointInfo) AddrNetProtoLocked(addr tcpip.FullAddress, v6onl
 	switch len(t.ID.LocalAddress) {
 	case header.IPv4AddressSize:
 		if len(addr.Addr) == header.IPv6AddressSize {
-			return tcpip.FullAddress{}, 0, tcpip.ErrInvalidEndpointState
+			return tcpip.FullAddress{}, 0, &tcpip.ErrInvalidEndpointState{}
 		}
 	case header.IPv6AddressSize:
 		if len(addr.Addr) == header.IPv4AddressSize {
-			return tcpip.FullAddress{}, 0, tcpip.ErrNetworkUnreachable
+			return tcpip.FullAddress{}, 0, &tcpip.ErrNetworkUnreachable{}
 		}
 	}
 
@@ -582,10 +582,10 @@ func (t *TransportEndpointInfo) AddrNetProtoLocked(addr tcpip.FullAddress, v6onl
 	case netProto == t.NetProto:
 	case netProto == header.IPv4ProtocolNumber && t.NetProto == header.IPv6ProtocolNumber:
 		if v6only {
-			return tcpip.FullAddress{}, 0, tcpip.ErrNoRoute
+			return tcpip.FullAddress{}, 0, &tcpip.ErrNoRoute{}
 		}
 	default:
-		return tcpip.FullAddress{}, 0, tcpip.ErrInvalidEndpointState
+		return tcpip.FullAddress{}, 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	return addr, netProto, nil
@@ -698,10 +698,10 @@ func (s *Stack) UniqueID() uint64 {
 // options. This method returns an error if the protocol is not supported or
 // option is not supported by the protocol implementation or the provided value
 // is incorrect.
-func (s *Stack) SetNetworkProtocolOption(network tcpip.NetworkProtocolNumber, option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
+func (s *Stack) SetNetworkProtocolOption(network tcpip.NetworkProtocolNumber, option tcpip.SettableNetworkProtocolOption) tcpip.Error {
 	netProto, ok := s.networkProtocols[network]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 	return netProto.SetOption(option)
 }
@@ -715,10 +715,10 @@ func (s *Stack) SetNetworkProtocolOption(network tcpip.NetworkProtocolNumber, op
 // if err != nil {
 //   ...
 // }
-func (s *Stack) NetworkProtocolOption(network tcpip.NetworkProtocolNumber, option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
+func (s *Stack) NetworkProtocolOption(network tcpip.NetworkProtocolNumber, option tcpip.GettableNetworkProtocolOption) tcpip.Error {
 	netProto, ok := s.networkProtocols[network]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 	return netProto.Option(option)
 }
@@ -727,10 +727,10 @@ func (s *Stack) NetworkProtocolOption(network tcpip.NetworkProtocolNumber, optio
 // options. This method returns an error if the protocol is not supported or
 // option is not supported by the protocol implementation or the provided value
 // is incorrect.
-func (s *Stack) SetTransportProtocolOption(transport tcpip.TransportProtocolNumber, option tcpip.SettableTransportProtocolOption) *tcpip.Error {
+func (s *Stack) SetTransportProtocolOption(transport tcpip.TransportProtocolNumber, option tcpip.SettableTransportProtocolOption) tcpip.Error {
 	transProtoState, ok := s.transportProtocols[transport]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 	return transProtoState.proto.SetOption(option)
 }
@@ -742,10 +742,10 @@ func (s *Stack) SetTransportProtocolOption(transport tcpip.TransportProtocolNumb
 // if err := s.TransportProtocolOption(tcpip.TCPProtocolNumber, &v); err != nil {
 //   ...
 // }
-func (s *Stack) TransportProtocolOption(transport tcpip.TransportProtocolNumber, option tcpip.GettableTransportProtocolOption) *tcpip.Error {
+func (s *Stack) TransportProtocolOption(transport tcpip.TransportProtocolNumber, option tcpip.GettableTransportProtocolOption) tcpip.Error {
 	transProtoState, ok := s.transportProtocols[transport]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 	return transProtoState.proto.Option(option)
 }
@@ -778,15 +778,15 @@ func (s *Stack) Stats() tcpip.Stats {
 
 // SetForwarding enables or disables packet forwarding between NICs for the
 // passed protocol.
-func (s *Stack) SetForwarding(protocolNum tcpip.NetworkProtocolNumber, enable bool) *tcpip.Error {
+func (s *Stack) SetForwarding(protocolNum tcpip.NetworkProtocolNumber, enable bool) tcpip.Error {
 	protocol, ok := s.networkProtocols[protocolNum]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 
 	forwardingProtocol, ok := protocol.(ForwardingNetworkProtocol)
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	forwardingProtocol.SetForwarding(enable)
@@ -849,10 +849,10 @@ func (s *Stack) RemoveRoutes(match func(tcpip.Route) bool) {
 }
 
 // NewEndpoint creates a new transport layer endpoint of the given protocol.
-func (s *Stack) NewEndpoint(transport tcpip.TransportProtocolNumber, network tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (s *Stack) NewEndpoint(transport tcpip.TransportProtocolNumber, network tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	t, ok := s.transportProtocols[transport]
 	if !ok {
-		return nil, tcpip.ErrUnknownProtocol
+		return nil, &tcpip.ErrUnknownProtocol{}
 	}
 
 	return t.proto.NewEndpoint(network, waiterQueue)
@@ -861,9 +861,9 @@ func (s *Stack) NewEndpoint(transport tcpip.TransportProtocolNumber, network tcp
 // NewRawEndpoint creates a new raw transport layer endpoint of the given
 // protocol. Raw endpoints receive all traffic for a given protocol regardless
 // of address.
-func (s *Stack) NewRawEndpoint(transport tcpip.TransportProtocolNumber, network tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue, associated bool) (tcpip.Endpoint, *tcpip.Error) {
+func (s *Stack) NewRawEndpoint(transport tcpip.TransportProtocolNumber, network tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue, associated bool) (tcpip.Endpoint, tcpip.Error) {
 	if s.rawFactory == nil {
-		return nil, tcpip.ErrNotPermitted
+		return nil, &tcpip.ErrNotPermitted{}
 	}
 
 	if !associated {
@@ -872,7 +872,7 @@ func (s *Stack) NewRawEndpoint(transport tcpip.TransportProtocolNumber, network
 
 	t, ok := s.transportProtocols[transport]
 	if !ok {
-		return nil, tcpip.ErrUnknownProtocol
+		return nil, &tcpip.ErrUnknownProtocol{}
 	}
 
 	return t.proto.NewRawEndpoint(network, waiterQueue)
@@ -880,9 +880,9 @@ func (s *Stack) NewRawEndpoint(transport tcpip.TransportProtocolNumber, network
 
 // NewPacketEndpoint creates a new packet endpoint listening for the given
 // netProto.
-func (s *Stack) NewPacketEndpoint(cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (s *Stack) NewPacketEndpoint(cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	if s.rawFactory == nil {
-		return nil, tcpip.ErrNotPermitted
+		return nil, &tcpip.ErrNotPermitted{}
 	}
 
 	return s.rawFactory.NewPacketEndpoint(s, cooked, netProto, waiterQueue)
@@ -913,20 +913,20 @@ type NICOptions struct {
 // NICs can be configured.
 //
 // LinkEndpoint.Attach will be called to bind ep with a NetworkDispatcher.
-func (s *Stack) CreateNICWithOptions(id tcpip.NICID, ep LinkEndpoint, opts NICOptions) *tcpip.Error {
+func (s *Stack) CreateNICWithOptions(id tcpip.NICID, ep LinkEndpoint, opts NICOptions) tcpip.Error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
 	// Make sure id is unique.
 	if _, ok := s.nics[id]; ok {
-		return tcpip.ErrDuplicateNICID
+		return &tcpip.ErrDuplicateNICID{}
 	}
 
 	// Make sure name is unique, unless unnamed.
 	if opts.Name != "" {
 		for _, n := range s.nics {
 			if n.Name() == opts.Name {
-				return tcpip.ErrDuplicateNICID
+				return &tcpip.ErrDuplicateNICID{}
 			}
 		}
 	}
@@ -942,7 +942,7 @@ func (s *Stack) CreateNICWithOptions(id tcpip.NICID, ep LinkEndpoint, opts NICOp
 
 // CreateNIC creates a NIC with the provided id and LinkEndpoint and calls
 // LinkEndpoint.Attach to bind ep with a NetworkDispatcher.
-func (s *Stack) CreateNIC(id tcpip.NICID, ep LinkEndpoint) *tcpip.Error {
+func (s *Stack) CreateNIC(id tcpip.NICID, ep LinkEndpoint) tcpip.Error {
 	return s.CreateNICWithOptions(id, ep, NICOptions{})
 }
 
@@ -960,26 +960,26 @@ func (s *Stack) GetLinkEndpointByName(name string) LinkEndpoint {
 
 // EnableNIC enables the given NIC so that the link-layer endpoint can start
 // delivering packets to it.
-func (s *Stack) EnableNIC(id tcpip.NICID) *tcpip.Error {
+func (s *Stack) EnableNIC(id tcpip.NICID) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[id]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.enable()
 }
 
 // DisableNIC disables the given NIC.
-func (s *Stack) DisableNIC(id tcpip.NICID) *tcpip.Error {
+func (s *Stack) DisableNIC(id tcpip.NICID) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[id]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	nic.disable()
@@ -1000,7 +1000,7 @@ func (s *Stack) CheckNIC(id tcpip.NICID) bool {
 }
 
 // RemoveNIC removes NIC and all related routes from the network stack.
-func (s *Stack) RemoveNIC(id tcpip.NICID) *tcpip.Error {
+func (s *Stack) RemoveNIC(id tcpip.NICID) tcpip.Error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -1010,10 +1010,10 @@ func (s *Stack) RemoveNIC(id tcpip.NICID) *tcpip.Error {
 // removeNICLocked removes NIC and all related routes from the network stack.
 //
 // s.mu must be locked.
-func (s *Stack) removeNICLocked(id tcpip.NICID) *tcpip.Error {
+func (s *Stack) removeNICLocked(id tcpip.NICID) tcpip.Error {
 	nic, ok := s.nics[id]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 	delete(s.nics, id)
 
@@ -1118,13 +1118,13 @@ type NICStateFlags struct {
 }
 
 // AddAddress adds a new network-layer address to the specified NIC.
-func (s *Stack) AddAddress(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) *tcpip.Error {
+func (s *Stack) AddAddress(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.Address) tcpip.Error {
 	return s.AddAddressWithOptions(id, protocol, addr, CanBePrimaryEndpoint)
 }
 
 // AddAddressWithPrefix is the same as AddAddress, but allows you to specify
 // the address prefix.
-func (s *Stack) AddAddressWithPrefix(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.AddressWithPrefix) *tcpip.Error {
+func (s *Stack) AddAddressWithPrefix(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.AddressWithPrefix) tcpip.Error {
 	ap := tcpip.ProtocolAddress{
 		Protocol:          protocol,
 		AddressWithPrefix: addr,
@@ -1134,16 +1134,16 @@ func (s *Stack) AddAddressWithPrefix(id tcpip.NICID, protocol tcpip.NetworkProto
 
 // AddProtocolAddress adds a new network-layer protocol address to the
 // specified NIC.
-func (s *Stack) AddProtocolAddress(id tcpip.NICID, protocolAddress tcpip.ProtocolAddress) *tcpip.Error {
+func (s *Stack) AddProtocolAddress(id tcpip.NICID, protocolAddress tcpip.ProtocolAddress) tcpip.Error {
 	return s.AddProtocolAddressWithOptions(id, protocolAddress, CanBePrimaryEndpoint)
 }
 
 // AddAddressWithOptions is the same as AddAddress, but allows you to specify
 // whether the new endpoint can be primary or not.
-func (s *Stack) AddAddressWithOptions(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.Address, peb PrimaryEndpointBehavior) *tcpip.Error {
+func (s *Stack) AddAddressWithOptions(id tcpip.NICID, protocol tcpip.NetworkProtocolNumber, addr tcpip.Address, peb PrimaryEndpointBehavior) tcpip.Error {
 	netProto, ok := s.networkProtocols[protocol]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 	return s.AddProtocolAddressWithOptions(id, tcpip.ProtocolAddress{
 		Protocol: protocol,
@@ -1156,13 +1156,13 @@ func (s *Stack) AddAddressWithOptions(id tcpip.NICID, protocol tcpip.NetworkProt
 
 // AddProtocolAddressWithOptions is the same as AddProtocolAddress, but allows
 // you to specify whether the new endpoint can be primary or not.
-func (s *Stack) AddProtocolAddressWithOptions(id tcpip.NICID, protocolAddress tcpip.ProtocolAddress, peb PrimaryEndpointBehavior) *tcpip.Error {
+func (s *Stack) AddProtocolAddressWithOptions(id tcpip.NICID, protocolAddress tcpip.ProtocolAddress, peb PrimaryEndpointBehavior) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[id]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.addAddress(protocolAddress, peb)
@@ -1170,7 +1170,7 @@ func (s *Stack) AddProtocolAddressWithOptions(id tcpip.NICID, protocolAddress tc
 
 // RemoveAddress removes an existing network-layer address from the specified
 // NIC.
-func (s *Stack) RemoveAddress(id tcpip.NICID, addr tcpip.Address) *tcpip.Error {
+func (s *Stack) RemoveAddress(id tcpip.NICID, addr tcpip.Address) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
@@ -1178,7 +1178,7 @@ func (s *Stack) RemoveAddress(id tcpip.NICID, addr tcpip.Address) *tcpip.Error {
 		return nic.removeAddress(addr)
 	}
 
-	return tcpip.ErrUnknownNICID
+	return &tcpip.ErrUnknownNICID{}
 }
 
 // AllAddresses returns a map of NICIDs to their protocol addresses (primary
@@ -1308,7 +1308,7 @@ func (s *Stack) findLocalRouteRLocked(localAddressNICID tcpip.NICID, localAddr,
 // If no local address is provided, the stack will select a local address. If no
 // remote address is provided, the stack wil use a remote address equal to the
 // local address.
-func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, netProto tcpip.NetworkProtocolNumber, multicastLoop bool) (*Route, *tcpip.Error) {
+func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, netProto tcpip.NetworkProtocolNumber, multicastLoop bool) (*Route, tcpip.Error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
@@ -1344,9 +1344,9 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 		}
 
 		if isLoopback {
-			return nil, tcpip.ErrBadLocalAddress
+			return nil, &tcpip.ErrBadLocalAddress{}
 		}
-		return nil, tcpip.ErrNetworkUnreachable
+		return nil, &tcpip.ErrNetworkUnreachable{}
 	}
 
 	canForward := s.Forwarding(netProto) && !header.IsV6LinkLocalAddress(localAddr) && !isLinkLocal
@@ -1412,7 +1412,7 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 				}
 			}
 
-			return nil, tcpip.ErrNoRoute
+			return nil, &tcpip.ErrNoRoute{}
 		}
 
 		if id == 0 {
@@ -1432,12 +1432,12 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 	}
 
 	if needRoute {
-		return nil, tcpip.ErrNoRoute
+		return nil, &tcpip.ErrNoRoute{}
 	}
 	if header.IsV6LoopbackAddress(remoteAddr) {
-		return nil, tcpip.ErrBadLocalAddress
+		return nil, &tcpip.ErrBadLocalAddress{}
 	}
-	return nil, tcpip.ErrNetworkUnreachable
+	return nil, &tcpip.ErrNetworkUnreachable{}
 }
 
 // CheckNetworkProtocol checks if a given network protocol is enabled in the
@@ -1483,13 +1483,13 @@ func (s *Stack) CheckLocalAddress(nicID tcpip.NICID, protocol tcpip.NetworkProto
 }
 
 // SetPromiscuousMode enables or disables promiscuous mode in the given NIC.
-func (s *Stack) SetPromiscuousMode(nicID tcpip.NICID, enable bool) *tcpip.Error {
+func (s *Stack) SetPromiscuousMode(nicID tcpip.NICID, enable bool) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[nicID]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	nic.setPromiscuousMode(enable)
@@ -1499,13 +1499,13 @@ func (s *Stack) SetPromiscuousMode(nicID tcpip.NICID, enable bool) *tcpip.Error
 
 // SetSpoofing enables or disables address spoofing in the given NIC, allowing
 // endpoints to bind to any address in the NIC.
-func (s *Stack) SetSpoofing(nicID tcpip.NICID, enable bool) *tcpip.Error {
+func (s *Stack) SetSpoofing(nicID tcpip.NICID, enable bool) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[nicID]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	nic.setSpoofing(enable)
@@ -1514,13 +1514,13 @@ func (s *Stack) SetSpoofing(nicID tcpip.NICID, enable bool) *tcpip.Error {
 }
 
 // AddLinkAddress adds a link address for the neighbor on the specified NIC.
-func (s *Stack) AddLinkAddress(nicID tcpip.NICID, neighbor tcpip.Address, linkAddr tcpip.LinkAddress) *tcpip.Error {
+func (s *Stack) AddLinkAddress(nicID tcpip.NICID, neighbor tcpip.Address, linkAddr tcpip.LinkAddress) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	nic, ok := s.nics[nicID]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	nic.linkAddrCache.AddLinkAddress(neighbor, linkAddr)
@@ -1549,17 +1549,17 @@ type LinkResolutionResult struct {
 // If specified, the local address must be an address local to the interface
 // the neighbor cache belongs to. The local address is the source address of
 // a packet prompting NUD/link address resolution.
-func (s *Stack) GetLinkAddress(nicID tcpip.NICID, addr, localAddr tcpip.Address, protocol tcpip.NetworkProtocolNumber, onResolve func(LinkResolutionResult)) *tcpip.Error {
+func (s *Stack) GetLinkAddress(nicID tcpip.NICID, addr, localAddr tcpip.Address, protocol tcpip.NetworkProtocolNumber, onResolve func(LinkResolutionResult)) tcpip.Error {
 	s.mu.RLock()
 	nic, ok := s.nics[nicID]
 	s.mu.RUnlock()
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	linkRes, ok := s.linkAddrResolvers[protocol]
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	if linkAddr, ok := linkRes.ResolveStaticAddress(addr); ok {
@@ -1572,26 +1572,26 @@ func (s *Stack) GetLinkAddress(nicID tcpip.NICID, addr, localAddr tcpip.Address,
 }
 
 // Neighbors returns all IP to MAC address associations.
-func (s *Stack) Neighbors(nicID tcpip.NICID) ([]NeighborEntry, *tcpip.Error) {
+func (s *Stack) Neighbors(nicID tcpip.NICID) ([]NeighborEntry, tcpip.Error) {
 	s.mu.RLock()
 	nic, ok := s.nics[nicID]
 	s.mu.RUnlock()
 
 	if !ok {
-		return nil, tcpip.ErrUnknownNICID
+		return nil, &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.neighbors()
 }
 
 // AddStaticNeighbor statically associates an IP address to a MAC address.
-func (s *Stack) AddStaticNeighbor(nicID tcpip.NICID, addr tcpip.Address, linkAddr tcpip.LinkAddress) *tcpip.Error {
+func (s *Stack) AddStaticNeighbor(nicID tcpip.NICID, addr tcpip.Address, linkAddr tcpip.LinkAddress) tcpip.Error {
 	s.mu.RLock()
 	nic, ok := s.nics[nicID]
 	s.mu.RUnlock()
 
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.addStaticNeighbor(addr, linkAddr)
@@ -1600,26 +1600,26 @@ func (s *Stack) AddStaticNeighbor(nicID tcpip.NICID, addr tcpip.Address, linkAdd
 // RemoveNeighbor removes an IP to MAC address association previously created
 // either automically or by AddStaticNeighbor. Returns ErrBadAddress if there
 // is no association with the provided address.
-func (s *Stack) RemoveNeighbor(nicID tcpip.NICID, addr tcpip.Address) *tcpip.Error {
+func (s *Stack) RemoveNeighbor(nicID tcpip.NICID, addr tcpip.Address) tcpip.Error {
 	s.mu.RLock()
 	nic, ok := s.nics[nicID]
 	s.mu.RUnlock()
 
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.removeNeighbor(addr)
 }
 
 // ClearNeighbors removes all IP to MAC address associations.
-func (s *Stack) ClearNeighbors(nicID tcpip.NICID) *tcpip.Error {
+func (s *Stack) ClearNeighbors(nicID tcpip.NICID) tcpip.Error {
 	s.mu.RLock()
 	nic, ok := s.nics[nicID]
 	s.mu.RUnlock()
 
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.clearNeighbors()
@@ -1629,13 +1629,13 @@ func (s *Stack) ClearNeighbors(nicID tcpip.NICID) *tcpip.Error {
 // transport dispatcher. Received packets that match the provided id will be
 // delivered to the given endpoint; specifying a nic is optional, but
 // nic-specific IDs have precedence over global ones.
-func (s *Stack) RegisterTransportEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (s *Stack) RegisterTransportEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	return s.demux.registerEndpoint(netProtos, protocol, id, ep, flags, bindToDevice)
 }
 
 // CheckRegisterTransportEndpoint checks if an endpoint can be registered with
 // the stack transport dispatcher.
-func (s *Stack) CheckRegisterTransportEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (s *Stack) CheckRegisterTransportEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	return s.demux.checkEndpoint(netProtos, protocol, id, flags, bindToDevice)
 }
 
@@ -1672,7 +1672,7 @@ func (s *Stack) FindTransportEndpoint(netProto tcpip.NetworkProtocolNumber, tran
 // RegisterRawTransportEndpoint registers the given endpoint with the stack
 // transport dispatcher. Received packets that match the provided transport
 // protocol will be delivered to the given endpoint.
-func (s *Stack) RegisterRawTransportEndpoint(netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, ep RawTransportEndpoint) *tcpip.Error {
+func (s *Stack) RegisterRawTransportEndpoint(netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, ep RawTransportEndpoint) tcpip.Error {
 	return s.demux.registerRawEndpoint(netProto, transProto, ep)
 }
 
@@ -1782,7 +1782,7 @@ func (s *Stack) Resume() {
 // RegisterPacketEndpoint registers ep with the stack, causing it to receive
 // all traffic of the specified netProto on the given NIC. If nicID is 0, it
 // receives traffic from every NIC.
-func (s *Stack) RegisterPacketEndpoint(nicID tcpip.NICID, netProto tcpip.NetworkProtocolNumber, ep PacketEndpoint) *tcpip.Error {
+func (s *Stack) RegisterPacketEndpoint(nicID tcpip.NICID, netProto tcpip.NetworkProtocolNumber, ep PacketEndpoint) tcpip.Error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -1801,7 +1801,7 @@ func (s *Stack) RegisterPacketEndpoint(nicID tcpip.NICID, netProto tcpip.Network
 	// Capture on a specific device.
 	nic, ok := s.nics[nicID]
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 	if err := nic.registerPacketEndpoint(netProto, ep); err != nil {
 		return err
@@ -1839,12 +1839,12 @@ func (s *Stack) unregisterPacketEndpointLocked(nicID tcpip.NICID, netProto tcpip
 
 // WritePacketToRemote writes a payload on the specified NIC using the provided
 // network protocol and remote link address.
-func (s *Stack) WritePacketToRemote(nicID tcpip.NICID, remote tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, payload buffer.VectorisedView) *tcpip.Error {
+func (s *Stack) WritePacketToRemote(nicID tcpip.NICID, remote tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, payload buffer.VectorisedView) tcpip.Error {
 	s.mu.Lock()
 	nic, ok := s.nics[nicID]
 	s.mu.Unlock()
 	if !ok {
-		return tcpip.ErrUnknownDevice
+		return &tcpip.ErrUnknownDevice{}
 	}
 	pkt := NewPacketBuffer(PacketBufferOptions{
 		ReserveHeaderBytes: int(nic.MaxHeaderLength()),
@@ -1909,37 +1909,37 @@ func (s *Stack) RemoveTCPProbe() {
 }
 
 // JoinGroup joins the given multicast group on the given NIC.
-func (s *Stack) JoinGroup(protocol tcpip.NetworkProtocolNumber, nicID tcpip.NICID, multicastAddr tcpip.Address) *tcpip.Error {
+func (s *Stack) JoinGroup(protocol tcpip.NetworkProtocolNumber, nicID tcpip.NICID, multicastAddr tcpip.Address) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	if nic, ok := s.nics[nicID]; ok {
 		return nic.joinGroup(protocol, multicastAddr)
 	}
-	return tcpip.ErrUnknownNICID
+	return &tcpip.ErrUnknownNICID{}
 }
 
 // LeaveGroup leaves the given multicast group on the given NIC.
-func (s *Stack) LeaveGroup(protocol tcpip.NetworkProtocolNumber, nicID tcpip.NICID, multicastAddr tcpip.Address) *tcpip.Error {
+func (s *Stack) LeaveGroup(protocol tcpip.NetworkProtocolNumber, nicID tcpip.NICID, multicastAddr tcpip.Address) tcpip.Error {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	if nic, ok := s.nics[nicID]; ok {
 		return nic.leaveGroup(protocol, multicastAddr)
 	}
-	return tcpip.ErrUnknownNICID
+	return &tcpip.ErrUnknownNICID{}
 }
 
 // IsInGroup returns true if the NIC with ID nicID has joined the multicast
 // group multicastAddr.
-func (s *Stack) IsInGroup(nicID tcpip.NICID, multicastAddr tcpip.Address) (bool, *tcpip.Error) {
+func (s *Stack) IsInGroup(nicID tcpip.NICID, multicastAddr tcpip.Address) (bool, tcpip.Error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
 	if nic, ok := s.nics[nicID]; ok {
 		return nic.isInGroup(multicastAddr), nil
 	}
-	return false, tcpip.ErrUnknownNICID
+	return false, &tcpip.ErrUnknownNICID{}
 }
 
 // IPTables returns the stack's iptables.
@@ -1979,26 +1979,26 @@ func (s *Stack) AllowICMPMessage() bool {
 
 // GetNetworkEndpoint returns the NetworkEndpoint with the specified protocol
 // number installed on the specified NIC.
-func (s *Stack) GetNetworkEndpoint(nicID tcpip.NICID, proto tcpip.NetworkProtocolNumber) (NetworkEndpoint, *tcpip.Error) {
+func (s *Stack) GetNetworkEndpoint(nicID tcpip.NICID, proto tcpip.NetworkProtocolNumber) (NetworkEndpoint, tcpip.Error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
 	nic, ok := s.nics[nicID]
 	if !ok {
-		return nil, tcpip.ErrUnknownNICID
+		return nil, &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.getNetworkEndpoint(proto), nil
 }
 
 // NUDConfigurations gets the per-interface NUD configurations.
-func (s *Stack) NUDConfigurations(id tcpip.NICID) (NUDConfigurations, *tcpip.Error) {
+func (s *Stack) NUDConfigurations(id tcpip.NICID) (NUDConfigurations, tcpip.Error) {
 	s.mu.RLock()
 	nic, ok := s.nics[id]
 	s.mu.RUnlock()
 
 	if !ok {
-		return NUDConfigurations{}, tcpip.ErrUnknownNICID
+		return NUDConfigurations{}, &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.nudConfigs()
@@ -2008,13 +2008,13 @@ func (s *Stack) NUDConfigurations(id tcpip.NICID) (NUDConfigurations, *tcpip.Err
 //
 // Note, if c contains invalid NUD configuration values, it will be fixed to
 // use default values for the erroneous values.
-func (s *Stack) SetNUDConfigurations(id tcpip.NICID, c NUDConfigurations) *tcpip.Error {
+func (s *Stack) SetNUDConfigurations(id tcpip.NICID, c NUDConfigurations) tcpip.Error {
 	s.mu.RLock()
 	nic, ok := s.nics[id]
 	s.mu.RUnlock()
 
 	if !ok {
-		return tcpip.ErrUnknownNICID
+		return &tcpip.ErrUnknownNICID{}
 	}
 
 	return nic.setNUDConfigs(c)
@@ -2056,7 +2056,7 @@ func generateRandInt64() int64 {
 }
 
 // FindNetworkEndpoint returns the network endpoint for the given address.
-func (s *Stack) FindNetworkEndpoint(netProto tcpip.NetworkProtocolNumber, address tcpip.Address) (NetworkEndpoint, *tcpip.Error) {
+func (s *Stack) FindNetworkEndpoint(netProto tcpip.NetworkProtocolNumber, address tcpip.Address) (NetworkEndpoint, tcpip.Error) {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
@@ -2068,7 +2068,7 @@ func (s *Stack) FindNetworkEndpoint(netProto tcpip.NetworkProtocolNumber, addres
 		addressEndpoint.DecRef()
 		return nic.getNetworkEndpoint(netProto), nil
 	}
-	return nil, tcpip.ErrBadAddress
+	return nil, &tcpip.ErrBadAddress{}
 }
 
 // FindNICNameFromID returns the name of the NIC for the given NICID.
diff --git a/pkg/tcpip/stack/stack_options.go b/pkg/tcpip/stack/stack_options.go
index 92e70f94e..8d9b20b7e 100644
--- a/pkg/tcpip/stack/stack_options.go
+++ b/pkg/tcpip/stack/stack_options.go
@@ -40,17 +40,17 @@ type ReceiveBufferSizeOption struct {
 }
 
 // SetOption allows setting stack wide options.
-func (s *Stack) SetOption(option interface{}) *tcpip.Error {
+func (s *Stack) SetOption(option interface{}) tcpip.Error {
 	switch v := option.(type) {
 	case tcpip.SendBufferSizeOption:
 		// Make sure we don't allow lowering the buffer below minimum
 		// required for stack to work.
 		if v.Min < MinBufferSize {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		if v.Default < v.Min || v.Default > v.Max {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		s.mu.Lock()
@@ -62,11 +62,11 @@ func (s *Stack) SetOption(option interface{}) *tcpip.Error {
 		// Make sure we don't allow lowering the buffer below minimum
 		// required for stack to work.
 		if v.Min < MinBufferSize {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		if v.Default < v.Min || v.Default > v.Max {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		s.mu.Lock()
@@ -75,12 +75,12 @@ func (s *Stack) SetOption(option interface{}) *tcpip.Error {
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // Option allows retrieving stack wide options.
-func (s *Stack) Option(option interface{}) *tcpip.Error {
+func (s *Stack) Option(option interface{}) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.SendBufferSizeOption:
 		s.mu.RLock()
@@ -95,6 +95,6 @@ func (s *Stack) Option(option interface{}) *tcpip.Error {
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index 0f02f1d53..41f95811f 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -90,7 +90,7 @@ type fakeNetworkEndpoint struct {
 	dispatcher stack.TransportDispatcher
 }
 
-func (f *fakeNetworkEndpoint) Enable() *tcpip.Error {
+func (f *fakeNetworkEndpoint) Enable() tcpip.Error {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	f.mu.enabled = true
@@ -162,7 +162,7 @@ func (f *fakeNetworkEndpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumbe
 	return f.proto.Number()
 }
 
-func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) *tcpip.Error {
+func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.NetworkHeaderParams, pkt *stack.PacketBuffer) tcpip.Error {
 	// Increment the sent packet count in the protocol descriptor.
 	f.proto.sendPacketCount[int(r.RemoteAddress[0])%len(f.proto.sendPacketCount)]++
 
@@ -185,12 +185,12 @@ func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, gso *stack.GSO, params
 }
 
 // WritePackets implements stack.LinkEndpoint.WritePackets.
-func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, *tcpip.Error) {
+func (*fakeNetworkEndpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, tcpip.Error) {
 	panic("not implemented")
 }
 
-func (*fakeNetworkEndpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*fakeNetworkEndpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 func (f *fakeNetworkEndpoint) Close() {
@@ -253,23 +253,23 @@ func (f *fakeNetworkProtocol) NewEndpoint(nic stack.NetworkInterface, _ stack.Li
 	return e
 }
 
-func (f *fakeNetworkProtocol) SetOption(option tcpip.SettableNetworkProtocolOption) *tcpip.Error {
+func (f *fakeNetworkProtocol) SetOption(option tcpip.SettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		f.defaultTTL = uint8(*v)
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
-func (f *fakeNetworkProtocol) Option(option tcpip.GettableNetworkProtocolOption) *tcpip.Error {
+func (f *fakeNetworkProtocol) Option(option tcpip.GettableNetworkProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.DefaultTTLOption:
 		*v = tcpip.DefaultTTLOption(f.defaultTTL)
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
@@ -418,7 +418,7 @@ func TestNetworkReceive(t *testing.T) {
 	}
 }
 
-func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) *tcpip.Error {
+func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) tcpip.Error {
 	r, err := s.FindRoute(0, "", addr, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		return err
@@ -427,7 +427,7 @@ func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) *tcpip.Erro
 	return send(r, payload)
 }
 
-func send(r *stack.Route, payload buffer.View) *tcpip.Error {
+func send(r *stack.Route, payload buffer.View) tcpip.Error {
 	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: fakeTransNumber, TTL: 123, TOS: stack.DefaultTOS}, stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               payload.ToVectorisedView(),
@@ -456,14 +456,14 @@ func testSend(t *testing.T, r *stack.Route, ep *channel.Endpoint, payload buffer
 	}
 }
 
-func testFailingSend(t *testing.T, r *stack.Route, ep *channel.Endpoint, payload buffer.View, wantErr *tcpip.Error) {
+func testFailingSend(t *testing.T, r *stack.Route, ep *channel.Endpoint, payload buffer.View, wantErr tcpip.Error) {
 	t.Helper()
 	if gotErr := send(r, payload); gotErr != wantErr {
 		t.Errorf("send failed: got = %s, want = %s ", gotErr, wantErr)
 	}
 }
 
-func testFailingSendTo(t *testing.T, s *stack.Stack, addr tcpip.Address, ep *channel.Endpoint, payload buffer.View, wantErr *tcpip.Error) {
+func testFailingSendTo(t *testing.T, s *stack.Stack, addr tcpip.Address, ep *channel.Endpoint, payload buffer.View, wantErr tcpip.Error) {
 	t.Helper()
 	if gotErr := sendTo(s, addr, payload); gotErr != wantErr {
 		t.Errorf("sendto failed: got = %s, want = %s ", gotErr, wantErr)
@@ -600,8 +600,8 @@ func testRoute(t *testing.T, s *stack.Stack, nic tcpip.NICID, srcAddr, dstAddr,
 
 func testNoRoute(t *testing.T, s *stack.Stack, nic tcpip.NICID, srcAddr, dstAddr tcpip.Address) {
 	_, err := s.FindRoute(nic, srcAddr, dstAddr, fakeNetNumber, false /* multicastLoop */)
-	if err != tcpip.ErrNoRoute {
-		t.Fatalf("FindRoute returned unexpected error, got = %v, want = %s", err, tcpip.ErrNoRoute)
+	if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+		t.Fatalf("FindRoute returned unexpected error, got = %v, want = %s", err, &tcpip.ErrNoRoute{})
 	}
 }
 
@@ -649,8 +649,9 @@ func TestDisableUnknownNIC(t *testing.T) {
 		NetworkProtocols: []stack.NetworkProtocolFactory{fakeNetFactory},
 	})
 
-	if err := s.DisableNIC(1); err != tcpip.ErrUnknownNICID {
-		t.Fatalf("got s.DisableNIC(1) = %v, want = %s", err, tcpip.ErrUnknownNICID)
+	err := s.DisableNIC(1)
+	if _, ok := err.(*tcpip.ErrUnknownNICID); !ok {
+		t.Fatalf("got s.DisableNIC(1) = %v, want = %s", err, &tcpip.ErrUnknownNICID{})
 	}
 }
 
@@ -708,8 +709,9 @@ func TestRemoveUnknownNIC(t *testing.T) {
 		NetworkProtocols: []stack.NetworkProtocolFactory{fakeNetFactory},
 	})
 
-	if err := s.RemoveNIC(1); err != tcpip.ErrUnknownNICID {
-		t.Fatalf("got s.RemoveNIC(1) = %v, want = %s", err, tcpip.ErrUnknownNICID)
+	err := s.RemoveNIC(1)
+	if _, ok := err.(*tcpip.ErrUnknownNICID); !ok {
+		t.Fatalf("got s.RemoveNIC(1) = %v, want = %s", err, &tcpip.ErrUnknownNICID{})
 	}
 }
 
@@ -752,8 +754,8 @@ func TestRemoveNIC(t *testing.T) {
 func TestRouteWithDownNIC(t *testing.T) {
 	tests := []struct {
 		name   string
-		downFn func(s *stack.Stack, nicID tcpip.NICID) *tcpip.Error
-		upFn   func(s *stack.Stack, nicID tcpip.NICID) *tcpip.Error
+		downFn func(s *stack.Stack, nicID tcpip.NICID) tcpip.Error
+		upFn   func(s *stack.Stack, nicID tcpip.NICID) tcpip.Error
 	}{
 		{
 			name:   "Disabled NIC",
@@ -911,15 +913,15 @@ func TestRouteWithDownNIC(t *testing.T) {
 				if err := test.downFn(s, nicID1); err != nil {
 					t.Fatalf("test.downFn(_, %d): %s", nicID1, err)
 				}
-				testFailingSend(t, r1, ep1, buf, tcpip.ErrInvalidEndpointState)
+				testFailingSend(t, r1, ep1, buf, &tcpip.ErrInvalidEndpointState{})
 				testSend(t, r2, ep2, buf)
 
 				// Writes with Routes that use NIC2 after being brought down should fail.
 				if err := test.downFn(s, nicID2); err != nil {
 					t.Fatalf("test.downFn(_, %d): %s", nicID2, err)
 				}
-				testFailingSend(t, r1, ep1, buf, tcpip.ErrInvalidEndpointState)
-				testFailingSend(t, r2, ep2, buf, tcpip.ErrInvalidEndpointState)
+				testFailingSend(t, r1, ep1, buf, &tcpip.ErrInvalidEndpointState{})
+				testFailingSend(t, r2, ep2, buf, &tcpip.ErrInvalidEndpointState{})
 
 				if upFn := test.upFn; upFn != nil {
 					// Writes with Routes that use NIC1 after being brought up should
@@ -932,7 +934,7 @@ func TestRouteWithDownNIC(t *testing.T) {
 						t.Fatalf("test.upFn(_, %d): %s", nicID1, err)
 					}
 					testSend(t, r1, ep1, buf)
-					testFailingSend(t, r2, ep2, buf, tcpip.ErrInvalidEndpointState)
+					testFailingSend(t, r2, ep2, buf, &tcpip.ErrInvalidEndpointState{})
 				}
 			})
 		}
@@ -1057,11 +1059,12 @@ func TestAddressRemoval(t *testing.T) {
 		t.Fatal("RemoveAddress failed:", err)
 	}
 	testFailingRecv(t, fakeNet, localAddrByte, ep, buf)
-	testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+	testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 
 	// Check that removing the same address fails.
-	if err := s.RemoveAddress(1, localAddr); err != tcpip.ErrBadLocalAddress {
-		t.Fatalf("RemoveAddress returned unexpected error, got = %v, want = %s", err, tcpip.ErrBadLocalAddress)
+	err := s.RemoveAddress(1, localAddr)
+	if _, ok := err.(*tcpip.ErrBadLocalAddress); !ok {
+		t.Fatalf("RemoveAddress returned unexpected error, got = %v, want = %s", err, &tcpip.ErrBadLocalAddress{})
 	}
 }
 
@@ -1108,12 +1111,15 @@ func TestAddressRemovalWithRouteHeld(t *testing.T) {
 		t.Fatal("RemoveAddress failed:", err)
 	}
 	testFailingRecv(t, fakeNet, localAddrByte, ep, buf)
-	testFailingSend(t, r, ep, nil, tcpip.ErrInvalidEndpointState)
-	testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+	testFailingSend(t, r, ep, nil, &tcpip.ErrInvalidEndpointState{})
+	testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 
 	// Check that removing the same address fails.
-	if err := s.RemoveAddress(1, localAddr); err != tcpip.ErrBadLocalAddress {
-		t.Fatalf("RemoveAddress returned unexpected error, got = %v, want = %s", err, tcpip.ErrBadLocalAddress)
+	{
+		err := s.RemoveAddress(1, localAddr)
+		if _, ok := err.(*tcpip.ErrBadLocalAddress); !ok {
+			t.Fatalf("RemoveAddress returned unexpected error, got = %v, want = %s", err, &tcpip.ErrBadLocalAddress{})
+		}
 	}
 }
 
@@ -1207,7 +1213,7 @@ func TestEndpointExpiration(t *testing.T) {
 					// FIXME(b/139841518):Spoofing doesn't work if there is no primary address.
 					// testSendTo(t, s, remoteAddr, ep, nil)
 				} else {
-					testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+					testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 				}
 
 				// 2. Add Address, everything should work.
@@ -1235,7 +1241,7 @@ func TestEndpointExpiration(t *testing.T) {
 					// FIXME(b/139841518):Spoofing doesn't work if there is no primary address.
 					// testSendTo(t, s, remoteAddr, ep, nil)
 				} else {
-					testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+					testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 				}
 
 				// 4. Add Address back, everything should work again.
@@ -1274,8 +1280,8 @@ func TestEndpointExpiration(t *testing.T) {
 					testSend(t, r, ep, nil)
 					testSendTo(t, s, remoteAddr, ep, nil)
 				} else {
-					testFailingSend(t, r, ep, nil, tcpip.ErrInvalidEndpointState)
-					testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+					testFailingSend(t, r, ep, nil, &tcpip.ErrInvalidEndpointState{})
+					testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 				}
 
 				// 7. Add Address back, everything should work again.
@@ -1311,7 +1317,7 @@ func TestEndpointExpiration(t *testing.T) {
 					// FIXME(b/139841518):Spoofing doesn't work if there is no primary address.
 					// testSendTo(t, s, remoteAddr, ep, nil)
 				} else {
-					testFailingSendTo(t, s, remoteAddr, ep, nil, tcpip.ErrNoRoute)
+					testFailingSendTo(t, s, remoteAddr, ep, nil, &tcpip.ErrNoRoute{})
 				}
 			})
 		}
@@ -1354,8 +1360,8 @@ func TestPromiscuousMode(t *testing.T) {
 
 	// Check that we can't get a route as there is no local address.
 	_, err := s.FindRoute(0, "", "\x02", fakeNetNumber, false /* multicastLoop */)
-	if err != tcpip.ErrNoRoute {
-		t.Fatalf("FindRoute returned unexpected error: got = %v, want = %s", err, tcpip.ErrNoRoute)
+	if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+		t.Fatalf("FindRoute returned unexpected error: got = %v, want = %s", err, &tcpip.ErrNoRoute{})
 	}
 
 	// Set promiscuous mode to false, then check that packet can't be
@@ -1561,7 +1567,7 @@ func TestSpoofingNoAddress(t *testing.T) {
 		t.Errorf("FindRoute succeeded with route %+v when it should have failed", r)
 	}
 	// Sending a packet fails.
-	testFailingSendTo(t, s, dstAddr, ep, nil, tcpip.ErrNoRoute)
+	testFailingSendTo(t, s, dstAddr, ep, nil, &tcpip.ErrNoRoute{})
 
 	// With address spoofing enabled, FindRoute permits any address to be used
 	// as the source.
@@ -1611,8 +1617,11 @@ func TestOutgoingBroadcastWithEmptyRouteTable(t *testing.T) {
 	s.SetRouteTable([]tcpip.Route{})
 
 	// If there is no endpoint, it won't work.
-	if _, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */); err != tcpip.ErrNetworkUnreachable {
-		t.Fatalf("got FindRoute(1, %s, %s, %d) = %s, want = %s", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, tcpip.ErrNetworkUnreachable)
+	{
+		_, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */)
+		if _, ok := err.(*tcpip.ErrNetworkUnreachable); !ok {
+			t.Fatalf("got FindRoute(1, %s, %s, %d) = %s, want = %s", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, &tcpip.ErrNetworkUnreachable{})
+		}
 	}
 
 	protoAddr := tcpip.ProtocolAddress{Protocol: fakeNetNumber, AddressWithPrefix: tcpip.AddressWithPrefix{header.IPv4Any, 0}}
@@ -1631,8 +1640,11 @@ func TestOutgoingBroadcastWithEmptyRouteTable(t *testing.T) {
 	}
 
 	// If the NIC doesn't exist, it won't work.
-	if _, err := s.FindRoute(2, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */); err != tcpip.ErrNetworkUnreachable {
-		t.Fatalf("got FindRoute(2, %v, %v, %d) = %v want = %v", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, tcpip.ErrNetworkUnreachable)
+	{
+		_, err := s.FindRoute(2, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */)
+		if _, ok := err.(*tcpip.ErrNetworkUnreachable); !ok {
+			t.Fatalf("got FindRoute(2, %v, %v, %d) = %v want = %v", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, &tcpip.ErrNetworkUnreachable{})
+		}
 	}
 }
 
@@ -1774,9 +1786,9 @@ func TestMulticastOrIPv6LinkLocalNeedsNoRoute(t *testing.T) {
 				anyAddr = header.IPv6Any
 			}
 
-			want := tcpip.ErrNetworkUnreachable
+			var want tcpip.Error = &tcpip.ErrNetworkUnreachable{}
 			if tc.routeNeeded {
-				want = tcpip.ErrNoRoute
+				want = &tcpip.ErrNoRoute{}
 			}
 
 			// If there is no endpoint, it won't work.
@@ -1790,8 +1802,8 @@ func TestMulticastOrIPv6LinkLocalNeedsNoRoute(t *testing.T) {
 
 			if r, err := s.FindRoute(1, anyAddr, tc.address, fakeNetNumber, false /* multicastLoop */); tc.routeNeeded {
 				// Route table is empty but we need a route, this should cause an error.
-				if err != tcpip.ErrNoRoute {
-					t.Fatalf("got FindRoute(1, %v, %v, %v) = %v, want = %v", anyAddr, tc.address, fakeNetNumber, err, tcpip.ErrNoRoute)
+				if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+					t.Fatalf("got FindRoute(1, %v, %v, %v) = %v, want = %v", anyAddr, tc.address, fakeNetNumber, err, &tcpip.ErrNoRoute{})
 				}
 			} else {
 				if err != nil {
@@ -2115,7 +2127,7 @@ func TestCreateNICWithOptions(t *testing.T) {
 	type callArgsAndExpect struct {
 		nicID tcpip.NICID
 		opts  stack.NICOptions
-		err   *tcpip.Error
+		err   tcpip.Error
 	}
 
 	tests := []struct {
@@ -2133,7 +2145,7 @@ func TestCreateNICWithOptions(t *testing.T) {
 				{
 					nicID: tcpip.NICID(1),
 					opts:  stack.NICOptions{Name: "eth2"},
-					err:   tcpip.ErrDuplicateNICID,
+					err:   &tcpip.ErrDuplicateNICID{},
 				},
 			},
 		},
@@ -2148,7 +2160,7 @@ func TestCreateNICWithOptions(t *testing.T) {
 				{
 					nicID: tcpip.NICID(2),
 					opts:  stack.NICOptions{Name: "lo"},
-					err:   tcpip.ErrDuplicateNICID,
+					err:   &tcpip.ErrDuplicateNICID{},
 				},
 			},
 		},
@@ -2178,7 +2190,7 @@ func TestCreateNICWithOptions(t *testing.T) {
 				{
 					nicID: tcpip.NICID(1),
 					opts:  stack.NICOptions{},
-					err:   tcpip.ErrDuplicateNICID,
+					err:   &tcpip.ErrDuplicateNICID{},
 				},
 			},
 		},
@@ -3297,14 +3309,14 @@ func TestStackReceiveBufferSizeOption(t *testing.T) {
 	testCases := []struct {
 		name string
 		rs   stack.ReceiveBufferSizeOption
-		err  *tcpip.Error
+		err  tcpip.Error
 	}{
 		// Invalid configurations.
-		{"min_below_zero", stack.ReceiveBufferSizeOption{Min: -1, Default: sMin, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"min_zero", stack.ReceiveBufferSizeOption{Min: 0, Default: sMin, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"default_below_min", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin - 1, Max: sMin - 1}, tcpip.ErrInvalidOptionValue},
-		{"default_above_max", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"max_below_min", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin - 1}, tcpip.ErrInvalidOptionValue},
+		{"min_below_zero", stack.ReceiveBufferSizeOption{Min: -1, Default: sMin, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"min_zero", stack.ReceiveBufferSizeOption{Min: 0, Default: sMin, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"default_below_min", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin - 1, Max: sMin - 1}, &tcpip.ErrInvalidOptionValue{}},
+		{"default_above_max", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"max_below_min", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin - 1}, &tcpip.ErrInvalidOptionValue{}},
 
 		// Valid Configurations
 		{"in_ascending_order", stack.ReceiveBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin + 2}, nil},
@@ -3337,14 +3349,14 @@ func TestStackSendBufferSizeOption(t *testing.T) {
 	testCases := []struct {
 		name string
 		ss   tcpip.SendBufferSizeOption
-		err  *tcpip.Error
+		err  tcpip.Error
 	}{
 		// Invalid configurations.
-		{"min_below_zero", tcpip.SendBufferSizeOption{Min: -1, Default: sMin, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"min_zero", tcpip.SendBufferSizeOption{Min: 0, Default: sMin, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"default_below_min", tcpip.SendBufferSizeOption{Min: 0, Default: sMin - 1, Max: sMin - 1}, tcpip.ErrInvalidOptionValue},
-		{"default_above_max", tcpip.SendBufferSizeOption{Min: 0, Default: sMin + 1, Max: sMin}, tcpip.ErrInvalidOptionValue},
-		{"max_below_min", tcpip.SendBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin - 1}, tcpip.ErrInvalidOptionValue},
+		{"min_below_zero", tcpip.SendBufferSizeOption{Min: -1, Default: sMin, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"min_zero", tcpip.SendBufferSizeOption{Min: 0, Default: sMin, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"default_below_min", tcpip.SendBufferSizeOption{Min: 0, Default: sMin - 1, Max: sMin - 1}, &tcpip.ErrInvalidOptionValue{}},
+		{"default_above_max", tcpip.SendBufferSizeOption{Min: 0, Default: sMin + 1, Max: sMin}, &tcpip.ErrInvalidOptionValue{}},
+		{"max_below_min", tcpip.SendBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin - 1}, &tcpip.ErrInvalidOptionValue{}},
 
 		// Valid Configurations
 		{"in_ascending_order", tcpip.SendBufferSizeOption{Min: sMin, Default: sMin + 1, Max: sMin + 2}, nil},
@@ -3356,11 +3368,12 @@ func TestStackSendBufferSizeOption(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			s := stack.New(stack.Options{})
 			defer s.Close()
-			if err := s.SetOption(tc.ss); err != tc.err {
-				t.Fatalf("s.SetOption(%+v) = %v, want: %v", tc.ss, err, tc.err)
+			err := s.SetOption(tc.ss)
+			if diff := cmp.Diff(tc.err, err); diff != "" {
+				t.Fatalf("unexpected error from s.SetOption(%+v), (-want, +got):\n%s", tc.ss, diff)
 			}
-			var ss tcpip.SendBufferSizeOption
 			if tc.err == nil {
+				var ss tcpip.SendBufferSizeOption
 				if err := s.Option(&ss); err != nil {
 					t.Fatalf("s.Option(%+v) = %v, want: nil", ss, err)
 				}
@@ -3919,7 +3932,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 		addrNIC   tcpip.NICID
 		localAddr tcpip.Address
 
-		findRouteErr          *tcpip.Error
+		findRouteErr          tcpip.Error
 		dependentOnForwarding bool
 	}{
 		{
@@ -3928,7 +3941,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			forwardingEnabled:     false,
 			addrNIC:               nicID1,
 			localAddr:             fakeNetCfg.nic2Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -3937,7 +3950,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			forwardingEnabled:     true,
 			addrNIC:               nicID1,
 			localAddr:             fakeNetCfg.nic2Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -3946,7 +3959,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			forwardingEnabled:     false,
 			addrNIC:               nicID1,
 			localAddr:             fakeNetCfg.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -3982,7 +3995,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			forwardingEnabled:     false,
 			addrNIC:               nicID2,
 			localAddr:             fakeNetCfg.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -3991,7 +4004,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			forwardingEnabled:     true,
 			addrNIC:               nicID2,
 			localAddr:             fakeNetCfg.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4015,7 +4028,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                fakeNetCfg,
 			forwardingEnabled:     false,
 			localAddr:             fakeNetCfg.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4031,7 +4044,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6LinkLocalNIC1WithGlobalRemote,
 			forwardingEnabled:     false,
 			addrNIC:               nicID1,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4039,7 +4052,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6LinkLocalNIC1WithGlobalRemote,
 			forwardingEnabled:     true,
 			addrNIC:               nicID1,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4047,7 +4060,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6LinkLocalNIC1WithGlobalRemote,
 			forwardingEnabled:     false,
 			localAddr:             ipv6LinkLocalNIC1WithGlobalRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4055,7 +4068,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6LinkLocalNIC1WithGlobalRemote,
 			forwardingEnabled:     true,
 			localAddr:             ipv6LinkLocalNIC1WithGlobalRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNoRoute,
+			findRouteErr:          &tcpip.ErrNoRoute{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4087,7 +4100,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6GlobalNIC1WithLinkLocalRemote,
 			forwardingEnabled:     false,
 			localAddr:             ipv6GlobalNIC1WithLinkLocalRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNetworkUnreachable,
+			findRouteErr:          &tcpip.ErrNetworkUnreachable{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4095,7 +4108,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6GlobalNIC1WithLinkLocalRemote,
 			forwardingEnabled:     true,
 			localAddr:             ipv6GlobalNIC1WithLinkLocalRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNetworkUnreachable,
+			findRouteErr:          &tcpip.ErrNetworkUnreachable{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4103,7 +4116,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6GlobalNIC1WithLinkLocalMulticastRemote,
 			forwardingEnabled:     false,
 			localAddr:             ipv6GlobalNIC1WithLinkLocalMulticastRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNetworkUnreachable,
+			findRouteErr:          &tcpip.ErrNetworkUnreachable{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4111,7 +4124,7 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			netCfg:                ipv6GlobalNIC1WithLinkLocalMulticastRemote,
 			forwardingEnabled:     true,
 			localAddr:             ipv6GlobalNIC1WithLinkLocalMulticastRemote.nic1Addr,
-			findRouteErr:          tcpip.ErrNetworkUnreachable,
+			findRouteErr:          &tcpip.ErrNetworkUnreachable{},
 			dependentOnForwarding: false,
 		},
 		{
@@ -4166,8 +4179,8 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			if r != nil {
 				defer r.Release()
 			}
-			if err != test.findRouteErr {
-				t.Fatalf("FindRoute(%d, %s, %s, %d, false) = %s, want = %s", test.addrNIC, test.localAddr, test.netCfg.remoteAddr, test.netCfg.proto, err, test.findRouteErr)
+			if diff := cmp.Diff(test.findRouteErr, err); diff != "" {
+				t.Fatalf("unexpected error from FindRoute(%d, %s, %s, %d, false), (-want, +got):\n%s", test.addrNIC, test.localAddr, test.netCfg.remoteAddr, test.netCfg.proto, diff)
 			}
 
 			if test.findRouteErr != nil {
@@ -4214,8 +4227,11 @@ func TestFindRouteWithForwarding(t *testing.T) {
 			if err := s.SetForwarding(test.netCfg.proto, false); err != nil {
 				t.Fatalf("SetForwarding(%d, false): %s", test.netCfg.proto, err)
 			}
-			if err := send(r, data); err != tcpip.ErrInvalidEndpointState {
-				t.Fatalf("got send(_, _) = %s, want = %s", err, tcpip.ErrInvalidEndpointState)
+			{
+				err := send(r, data)
+				if _, ok := err.(*tcpip.ErrInvalidEndpointState); !ok {
+					t.Fatalf("got send(_, _) = %s, want = %s", err, &tcpip.ErrInvalidEndpointState{})
+				}
 			}
 			if n := ep1.Drain(); n != 0 {
 				t.Errorf("got %d unexpected packets from ep1", n)
@@ -4277,8 +4293,9 @@ func TestWritePacketToRemote(t *testing.T) {
 	}
 
 	t.Run("InvalidNICID", func(t *testing.T) {
-		if got, want := s.WritePacketToRemote(234, linkAddr2, header.IPv4ProtocolNumber, buffer.View([]byte{1}).ToVectorisedView()), tcpip.ErrUnknownDevice; got != want {
-			t.Fatalf("s.WritePacketToRemote(_, _, _, _) = %s, want = %s", got, want)
+		err := s.WritePacketToRemote(234, linkAddr2, header.IPv4ProtocolNumber, buffer.View([]byte{1}).ToVectorisedView())
+		if _, ok := err.(*tcpip.ErrUnknownDevice); !ok {
+			t.Fatalf("s.WritePacketToRemote(_, _, _, _) = %s, want = %s", err, &tcpip.ErrUnknownDevice{})
 		}
 		pkt, ok := e.Read()
 		if got, want := ok, false; got != want {
@@ -4352,11 +4369,17 @@ func TestGetLinkAddressErrors(t *testing.T) {
 		t.Fatalf("CreateNIC(%d, _) = %s", nicID, err)
 	}
 
-	if err := s.GetLinkAddress(unknownNICID, "", "", ipv4.ProtocolNumber, nil); err != tcpip.ErrUnknownNICID {
-		t.Errorf("got s.GetLinkAddress(%d, '', '', %d, nil) = %s, want = %s", unknownNICID, ipv4.ProtocolNumber, err, tcpip.ErrUnknownNICID)
+	{
+		err := s.GetLinkAddress(unknownNICID, "", "", ipv4.ProtocolNumber, nil)
+		if _, ok := err.(*tcpip.ErrUnknownNICID); !ok {
+			t.Errorf("got s.GetLinkAddress(%d, '', '', %d, nil) = %s, want = %s", unknownNICID, ipv4.ProtocolNumber, err, &tcpip.ErrUnknownNICID{})
+		}
 	}
-	if err := s.GetLinkAddress(nicID, "", "", ipv4.ProtocolNumber, nil); err != tcpip.ErrNotSupported {
-		t.Errorf("got s.GetLinkAddress(%d, '', '', %d, nil) = %s, want = %s", unknownNICID, ipv4.ProtocolNumber, err, tcpip.ErrNotSupported)
+	{
+		err := s.GetLinkAddress(nicID, "", "", ipv4.ProtocolNumber, nil)
+		if _, ok := err.(*tcpip.ErrNotSupported); !ok {
+			t.Errorf("got s.GetLinkAddress(%d, '', '', %d, nil) = %s, want = %s", unknownNICID, ipv4.ProtocolNumber, err, &tcpip.ErrNotSupported{})
+		}
 	}
 }
 
diff --git a/pkg/tcpip/stack/transport_demuxer.go b/pkg/tcpip/stack/transport_demuxer.go
index 07b2818d2..26eceb804 100644
--- a/pkg/tcpip/stack/transport_demuxer.go
+++ b/pkg/tcpip/stack/transport_demuxer.go
@@ -205,7 +205,7 @@ func (epsByNIC *endpointsByNIC) handleControlPacket(n *NIC, id TransportEndpoint
 
 // registerEndpoint returns true if it succeeds. It fails and returns
 // false if ep already has an element with the same key.
-func (epsByNIC *endpointsByNIC) registerEndpoint(d *transportDemuxer, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, t TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (epsByNIC *endpointsByNIC) registerEndpoint(d *transportDemuxer, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, t TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	epsByNIC.mu.Lock()
 	defer epsByNIC.mu.Unlock()
 
@@ -222,7 +222,7 @@ func (epsByNIC *endpointsByNIC) registerEndpoint(d *transportDemuxer, netProto t
 	return multiPortEp.singleRegisterEndpoint(t, flags)
 }
 
-func (epsByNIC *endpointsByNIC) checkEndpoint(d *transportDemuxer, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (epsByNIC *endpointsByNIC) checkEndpoint(d *transportDemuxer, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	epsByNIC.mu.RLock()
 	defer epsByNIC.mu.RUnlock()
 
@@ -294,7 +294,7 @@ func newTransportDemuxer(stack *Stack) *transportDemuxer {
 
 // registerEndpoint registers the given endpoint with the dispatcher such that
 // packets that match the endpoint ID are delivered to it.
-func (d *transportDemuxer) registerEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (d *transportDemuxer) registerEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	for i, n := range netProtos {
 		if err := d.singleRegisterEndpoint(n, protocol, id, ep, flags, bindToDevice); err != nil {
 			d.unregisterEndpoint(netProtos[:i], protocol, id, ep, flags, bindToDevice)
@@ -306,7 +306,7 @@ func (d *transportDemuxer) registerEndpoint(netProtos []tcpip.NetworkProtocolNum
 }
 
 // checkEndpoint checks if an endpoint can be registered with the dispatcher.
-func (d *transportDemuxer) checkEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (d *transportDemuxer) checkEndpoint(netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	for _, n := range netProtos {
 		if err := d.singleCheckEndpoint(n, protocol, id, flags, bindToDevice); err != nil {
 			return err
@@ -403,7 +403,7 @@ func (ep *multiPortEndpoint) handlePacketAll(id TransportEndpointID, pkt *Packet
 
 // singleRegisterEndpoint tries to add an endpoint to the multiPortEndpoint
 // list. The list might be empty already.
-func (ep *multiPortEndpoint) singleRegisterEndpoint(t TransportEndpoint, flags ports.Flags) *tcpip.Error {
+func (ep *multiPortEndpoint) singleRegisterEndpoint(t TransportEndpoint, flags ports.Flags) tcpip.Error {
 	ep.mu.Lock()
 	defer ep.mu.Unlock()
 
@@ -412,7 +412,7 @@ func (ep *multiPortEndpoint) singleRegisterEndpoint(t TransportEndpoint, flags p
 	if len(ep.endpoints) != 0 {
 		// If it was previously bound, we need to check if we can bind again.
 		if ep.flags.TotalRefs() > 0 && bits&ep.flags.IntersectionRefs() == 0 {
-			return tcpip.ErrPortInUse
+			return &tcpip.ErrPortInUse{}
 		}
 	}
 
@@ -422,7 +422,7 @@ func (ep *multiPortEndpoint) singleRegisterEndpoint(t TransportEndpoint, flags p
 	return nil
 }
 
-func (ep *multiPortEndpoint) singleCheckEndpoint(flags ports.Flags) *tcpip.Error {
+func (ep *multiPortEndpoint) singleCheckEndpoint(flags ports.Flags) tcpip.Error {
 	ep.mu.RLock()
 	defer ep.mu.RUnlock()
 
@@ -431,7 +431,7 @@ func (ep *multiPortEndpoint) singleCheckEndpoint(flags ports.Flags) *tcpip.Error
 	if len(ep.endpoints) != 0 {
 		// If it was previously bound, we need to check if we can bind again.
 		if ep.flags.TotalRefs() > 0 && bits&ep.flags.IntersectionRefs() == 0 {
-			return tcpip.ErrPortInUse
+			return &tcpip.ErrPortInUse{}
 		}
 	}
 
@@ -456,7 +456,7 @@ func (ep *multiPortEndpoint) unregisterEndpoint(t TransportEndpoint, flags ports
 	return len(ep.endpoints) == 0
 }
 
-func (d *transportDemuxer) singleRegisterEndpoint(netProto tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (d *transportDemuxer) singleRegisterEndpoint(netProto tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	if id.RemotePort != 0 {
 		// SO_REUSEPORT only applies to bound/listening endpoints.
 		flags.LoadBalanced = false
@@ -464,7 +464,7 @@ func (d *transportDemuxer) singleRegisterEndpoint(netProto tcpip.NetworkProtocol
 
 	eps, ok := d.protocol[protocolIDs{netProto, protocol}]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 
 	eps.mu.Lock()
@@ -482,7 +482,7 @@ func (d *transportDemuxer) singleRegisterEndpoint(netProto tcpip.NetworkProtocol
 	return epsByNIC.registerEndpoint(d, netProto, protocol, ep, flags, bindToDevice)
 }
 
-func (d *transportDemuxer) singleCheckEndpoint(netProto tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) *tcpip.Error {
+func (d *transportDemuxer) singleCheckEndpoint(netProto tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, flags ports.Flags, bindToDevice tcpip.NICID) tcpip.Error {
 	if id.RemotePort != 0 {
 		// SO_REUSEPORT only applies to bound/listening endpoints.
 		flags.LoadBalanced = false
@@ -490,7 +490,7 @@ func (d *transportDemuxer) singleCheckEndpoint(netProto tcpip.NetworkProtocolNum
 
 	eps, ok := d.protocol[protocolIDs{netProto, protocol}]
 	if !ok {
-		return tcpip.ErrUnknownProtocol
+		return &tcpip.ErrUnknownProtocol{}
 	}
 
 	eps.mu.RLock()
@@ -649,10 +649,10 @@ func (d *transportDemuxer) findTransportEndpoint(netProto tcpip.NetworkProtocolN
 // that packets of the appropriate protocol are delivered to it. A single
 // packet can be sent to one or more raw endpoints along with a non-raw
 // endpoint.
-func (d *transportDemuxer) registerRawEndpoint(netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, ep RawTransportEndpoint) *tcpip.Error {
+func (d *transportDemuxer) registerRawEndpoint(netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, ep RawTransportEndpoint) tcpip.Error {
 	eps, ok := d.protocol[protocolIDs{netProto, transProto}]
 	if !ok {
-		return tcpip.ErrNotSupported
+		return &tcpip.ErrNotSupported{}
 	}
 
 	eps.mu.Lock()
diff --git a/pkg/tcpip/stack/transport_demuxer_test.go b/pkg/tcpip/stack/transport_demuxer_test.go
index de4b5fbdc..10cbbe589 100644
--- a/pkg/tcpip/stack/transport_demuxer_test.go
+++ b/pkg/tcpip/stack/transport_demuxer_test.go
@@ -175,9 +175,9 @@ func TestTransportDemuxerRegister(t *testing.T) {
 	for _, test := range []struct {
 		name  string
 		proto tcpip.NetworkProtocolNumber
-		want  *tcpip.Error
+		want  tcpip.Error
 	}{
-		{"failure", ipv6.ProtocolNumber, tcpip.ErrUnknownProtocol},
+		{"failure", ipv6.ProtocolNumber, &tcpip.ErrUnknownProtocol{}},
 		{"success", ipv4.ProtocolNumber, nil},
 	} {
 		t.Run(test.name, func(t *testing.T) {
@@ -294,7 +294,7 @@ func TestBindToDeviceDistribution(t *testing.T) {
 						defer wq.EventUnregister(&we)
 						defer close(ch)
 
-						var err *tcpip.Error
+						var err tcpip.Error
 						ep, err := c.s.NewEndpoint(udp.ProtocolNumber, netProtoNum, &wq)
 						if err != nil {
 							t.Fatalf("NewEndpoint failed: %s", err)
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index c49427c4c..cf5de747b 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -87,18 +87,18 @@ func (*fakeTransportEndpoint) Readiness(mask waiter.EventMask) waiter.EventMask
 	return mask
 }
 
-func (*fakeTransportEndpoint) Read(io.Writer, tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (*fakeTransportEndpoint) Read(io.Writer, tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	return tcpip.ReadResult{}, nil
 }
 
-func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	if len(f.route.RemoteAddress) == 0 {
-		return 0, tcpip.ErrNoRoute
+		return 0, &tcpip.ErrNoRoute{}
 	}
 
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
-		return 0, tcpip.ErrBadBuffer
+		return 0, &tcpip.ErrBadBuffer{}
 	}
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
@@ -114,37 +114,37 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions
 }
 
 // SetSockOpt sets a socket option. Currently not supported.
-func (*fakeTransportEndpoint) SetSockOpt(tcpip.SettableSocketOption) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*fakeTransportEndpoint) SetSockOpt(tcpip.SettableSocketOption) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // SetSockOptInt sets a socket option. Currently not supported.
-func (*fakeTransportEndpoint) SetSockOptInt(tcpip.SockOptInt, int) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*fakeTransportEndpoint) SetSockOptInt(tcpip.SockOptInt, int) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
-	return -1, tcpip.ErrUnknownProtocolOption
+func (*fakeTransportEndpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
+	return -1, &tcpip.ErrUnknownProtocolOption{}
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (*fakeTransportEndpoint) GetSockOpt(tcpip.GettableSocketOption) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*fakeTransportEndpoint) GetSockOpt(tcpip.GettableSocketOption) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
-func (*fakeTransportEndpoint) Disconnect() *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*fakeTransportEndpoint) Disconnect() tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
-func (f *fakeTransportEndpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+func (f *fakeTransportEndpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	f.peerAddr = addr.Addr
 
 	// Find the route.
 	r, err := f.proto.stack.FindRoute(addr.NIC, "", addr.Addr, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
-		return tcpip.ErrNoRoute
+		return &tcpip.ErrNoRoute{}
 	}
 
 	// Try to register so that we can start receiving packets.
@@ -164,22 +164,22 @@ func (f *fakeTransportEndpoint) UniqueID() uint64 {
 	return f.uniqueID
 }
 
-func (*fakeTransportEndpoint) ConnectEndpoint(e tcpip.Endpoint) *tcpip.Error {
+func (*fakeTransportEndpoint) ConnectEndpoint(e tcpip.Endpoint) tcpip.Error {
 	return nil
 }
 
-func (*fakeTransportEndpoint) Shutdown(tcpip.ShutdownFlags) *tcpip.Error {
+func (*fakeTransportEndpoint) Shutdown(tcpip.ShutdownFlags) tcpip.Error {
 	return nil
 }
 
 func (*fakeTransportEndpoint) Reset() {
 }
 
-func (*fakeTransportEndpoint) Listen(int) *tcpip.Error {
+func (*fakeTransportEndpoint) Listen(int) tcpip.Error {
 	return nil
 }
 
-func (f *fakeTransportEndpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+func (f *fakeTransportEndpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
 	if len(f.acceptQueue) == 0 {
 		return nil, nil, nil
 	}
@@ -188,7 +188,7 @@ func (f *fakeTransportEndpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *wai
 	return a, nil, nil
 }
 
-func (f *fakeTransportEndpoint) Bind(a tcpip.FullAddress) *tcpip.Error {
+func (f *fakeTransportEndpoint) Bind(a tcpip.FullAddress) tcpip.Error {
 	if err := f.proto.stack.RegisterTransportEndpoint(
 		[]tcpip.NetworkProtocolNumber{fakeNetNumber},
 		fakeTransNumber,
@@ -203,11 +203,11 @@ func (f *fakeTransportEndpoint) Bind(a tcpip.FullAddress) *tcpip.Error {
 	return nil
 }
 
-func (*fakeTransportEndpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (*fakeTransportEndpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	return tcpip.FullAddress{}, nil
 }
 
-func (*fakeTransportEndpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (*fakeTransportEndpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	return tcpip.FullAddress{}, nil
 }
 
@@ -252,7 +252,7 @@ func (*fakeTransportEndpoint) Resume(*stack.Stack) {}
 
 func (*fakeTransportEndpoint) Wait() {}
 
-func (*fakeTransportEndpoint) LastError() *tcpip.Error {
+func (*fakeTransportEndpoint) LastError() tcpip.Error {
 	return nil
 }
 
@@ -280,19 +280,19 @@ func (*fakeTransportProtocol) Number() tcpip.TransportProtocolNumber {
 	return fakeTransNumber
 }
 
-func (f *fakeTransportProtocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, _ *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (f *fakeTransportProtocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, _ *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newFakeTransportEndpoint(f, netProto, f.stack), nil
 }
 
-func (*fakeTransportProtocol) NewRawEndpoint(tcpip.NetworkProtocolNumber, *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
-	return nil, tcpip.ErrUnknownProtocol
+func (*fakeTransportProtocol) NewRawEndpoint(tcpip.NetworkProtocolNumber, *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
+	return nil, &tcpip.ErrUnknownProtocol{}
 }
 
 func (*fakeTransportProtocol) MinimumPacketSize() int {
 	return fakeTransHeaderLen
 }
 
-func (*fakeTransportProtocol) ParsePorts(buffer.View) (src, dst uint16, err *tcpip.Error) {
+func (*fakeTransportProtocol) ParsePorts(buffer.View) (src, dst uint16, err tcpip.Error) {
 	return 0, 0, nil
 }
 
@@ -300,23 +300,23 @@ func (*fakeTransportProtocol) HandleUnknownDestinationPacket(stack.TransportEndp
 	return stack.UnknownDestinationPacketHandled
 }
 
-func (f *fakeTransportProtocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpip.Error {
+func (f *fakeTransportProtocol) SetOption(option tcpip.SettableTransportProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.TCPModerateReceiveBufferOption:
 		f.opts.good = bool(*v)
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
-func (f *fakeTransportProtocol) Option(option tcpip.GettableTransportProtocolOption) *tcpip.Error {
+func (f *fakeTransportProtocol) Option(option tcpip.GettableTransportProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.TCPModerateReceiveBufferOption:
 		*v = tcpip.TCPModerateReceiveBufferOption(f.opts.good)
 		return nil
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index c023152f1..c500a0d1c 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -47,141 +47,6 @@ import (
 // Using header.IPv4AddressSize would cause an import cycle.
 const ipv4AddressSize = 4
 
-// Error represents an error in the netstack error space. Using a special type
-// ensures that errors outside of this space are not accidentally introduced.
-//
-// All errors must have unique msg strings.
-//
-// +stateify savable
-type Error struct {
-	msg string
-
-	ignoreStats bool
-}
-
-// String implements fmt.Stringer.String.
-func (e *Error) String() string {
-	if e == nil {
-		return "<nil>"
-	}
-	return e.msg
-}
-
-// IgnoreStats indicates whether this error type should be included in failure
-// counts in tcpip.Stats structs.
-func (e *Error) IgnoreStats() bool {
-	return e.ignoreStats
-}
-
-// Errors that can be returned by the network stack.
-var (
-	ErrUnknownProtocol           = &Error{msg: "unknown protocol"}
-	ErrUnknownNICID              = &Error{msg: "unknown nic id"}
-	ErrUnknownDevice             = &Error{msg: "unknown device"}
-	ErrUnknownProtocolOption     = &Error{msg: "unknown option for protocol"}
-	ErrDuplicateNICID            = &Error{msg: "duplicate nic id"}
-	ErrDuplicateAddress          = &Error{msg: "duplicate address"}
-	ErrNoRoute                   = &Error{msg: "no route"}
-	ErrBadLinkEndpoint           = &Error{msg: "bad link layer endpoint"}
-	ErrAlreadyBound              = &Error{msg: "endpoint already bound", ignoreStats: true}
-	ErrInvalidEndpointState      = &Error{msg: "endpoint is in invalid state"}
-	ErrAlreadyConnecting         = &Error{msg: "endpoint is already connecting", ignoreStats: true}
-	ErrAlreadyConnected          = &Error{msg: "endpoint is already connected", ignoreStats: true}
-	ErrNoPortAvailable           = &Error{msg: "no ports are available"}
-	ErrPortInUse                 = &Error{msg: "port is in use"}
-	ErrBadLocalAddress           = &Error{msg: "bad local address"}
-	ErrClosedForSend             = &Error{msg: "endpoint is closed for send"}
-	ErrClosedForReceive          = &Error{msg: "endpoint is closed for receive"}
-	ErrWouldBlock                = &Error{msg: "operation would block", ignoreStats: true}
-	ErrConnectionRefused         = &Error{msg: "connection was refused"}
-	ErrTimeout                   = &Error{msg: "operation timed out"}
-	ErrAborted                   = &Error{msg: "operation aborted"}
-	ErrConnectStarted            = &Error{msg: "connection attempt started", ignoreStats: true}
-	ErrDestinationRequired       = &Error{msg: "destination address is required"}
-	ErrNotSupported              = &Error{msg: "operation not supported"}
-	ErrQueueSizeNotSupported     = &Error{msg: "queue size querying not supported"}
-	ErrNotConnected              = &Error{msg: "endpoint not connected"}
-	ErrConnectionReset           = &Error{msg: "connection reset by peer"}
-	ErrConnectionAborted         = &Error{msg: "connection aborted"}
-	ErrNoSuchFile                = &Error{msg: "no such file"}
-	ErrInvalidOptionValue        = &Error{msg: "invalid option value specified"}
-	ErrBadAddress                = &Error{msg: "bad address"}
-	ErrNetworkUnreachable        = &Error{msg: "network is unreachable"}
-	ErrMessageTooLong            = &Error{msg: "message too long"}
-	ErrNoBufferSpace             = &Error{msg: "no buffer space available"}
-	ErrBroadcastDisabled         = &Error{msg: "broadcast socket option disabled"}
-	ErrNotPermitted              = &Error{msg: "operation not permitted"}
-	ErrAddressFamilyNotSupported = &Error{msg: "address family not supported by protocol"}
-	ErrMalformedHeader           = &Error{msg: "header is malformed"}
-	ErrBadBuffer                 = &Error{msg: "bad buffer"}
-)
-
-var messageToError map[string]*Error
-
-var populate sync.Once
-
-// StringToError converts an error message to the error.
-func StringToError(s string) *Error {
-	populate.Do(func() {
-		var errors = []*Error{
-			ErrUnknownProtocol,
-			ErrUnknownNICID,
-			ErrUnknownDevice,
-			ErrUnknownProtocolOption,
-			ErrDuplicateNICID,
-			ErrDuplicateAddress,
-			ErrNoRoute,
-			ErrBadLinkEndpoint,
-			ErrAlreadyBound,
-			ErrInvalidEndpointState,
-			ErrAlreadyConnecting,
-			ErrAlreadyConnected,
-			ErrNoPortAvailable,
-			ErrPortInUse,
-			ErrBadLocalAddress,
-			ErrClosedForSend,
-			ErrClosedForReceive,
-			ErrWouldBlock,
-			ErrConnectionRefused,
-			ErrTimeout,
-			ErrAborted,
-			ErrConnectStarted,
-			ErrDestinationRequired,
-			ErrNotSupported,
-			ErrQueueSizeNotSupported,
-			ErrNotConnected,
-			ErrConnectionReset,
-			ErrConnectionAborted,
-			ErrNoSuchFile,
-			ErrInvalidOptionValue,
-			ErrBadAddress,
-			ErrNetworkUnreachable,
-			ErrMessageTooLong,
-			ErrNoBufferSpace,
-			ErrBroadcastDisabled,
-			ErrNotPermitted,
-			ErrAddressFamilyNotSupported,
-			ErrMalformedHeader,
-			ErrBadBuffer,
-		}
-
-		messageToError = make(map[string]*Error)
-		for _, e := range errors {
-			if messageToError[e.String()] != nil {
-				panic("tcpip errors with duplicated message: " + e.String())
-			}
-			messageToError[e.String()] = e
-		}
-	})
-
-	e, ok := messageToError[s]
-	if !ok {
-		panic("unknown error message: " + s)
-	}
-
-	return e
-}
-
 // Errors related to Subnet
 var (
 	errSubnetLengthMismatch = errors.New("subnet length of address and mask differ")
@@ -633,7 +498,7 @@ type Endpoint interface {
 	// If non-zero number of bytes are successfully read and written to dst, err
 	// must be nil. Otherwise, if dst failed to write anything, ErrBadBuffer
 	// should be returned.
-	Read(dst io.Writer, opts ReadOptions) (res ReadResult, err *Error)
+	Read(io.Writer, ReadOptions) (ReadResult, Error)
 
 	// Write writes data to the endpoint's peer. This method does not block if
 	// the data cannot be written.
@@ -648,7 +513,7 @@ type Endpoint interface {
 	// stream (TCP) Endpoints may return partial writes, and even then only
 	// in the case where writing additional data would block. Other Endpoints
 	// will either write the entire message or return an error.
-	Write(Payloader, WriteOptions) (int64, *Error)
+	Write(Payloader, WriteOptions) (int64, Error)
 
 	// Connect connects the endpoint to its peer. Specifying a NIC is
 	// optional.
@@ -665,18 +530,18 @@ type Endpoint interface {
 	// If address.Addr is empty, this means that Endpoint has to be
 	// disconnected if this is supported, otherwise
 	// ErrAddressFamilyNotSupported must be returned.
-	Connect(address FullAddress) *Error
+	Connect(address FullAddress) Error
 
 	// Disconnect disconnects the endpoint from its peer.
-	Disconnect() *Error
+	Disconnect() Error
 
 	// Shutdown closes the read and/or write end of the endpoint connection
 	// to its peer.
-	Shutdown(flags ShutdownFlags) *Error
+	Shutdown(flags ShutdownFlags) Error
 
 	// Listen puts the endpoint in "listen" mode, which allows it to accept
 	// new connections.
-	Listen(backlog int) *Error
+	Listen(backlog int) Error
 
 	// Accept returns a new endpoint if a peer has established a connection
 	// to an endpoint previously set to listen mode. This method does not
@@ -686,36 +551,36 @@ type Endpoint interface {
 	//
 	// If peerAddr is not nil then it is populated with the peer address of the
 	// returned endpoint.
-	Accept(peerAddr *FullAddress) (Endpoint, *waiter.Queue, *Error)
+	Accept(peerAddr *FullAddress) (Endpoint, *waiter.Queue, Error)
 
 	// Bind binds the endpoint to a specific local address and port.
 	// Specifying a NIC is optional.
-	Bind(address FullAddress) *Error
+	Bind(address FullAddress) Error
 
 	// GetLocalAddress returns the address to which the endpoint is bound.
-	GetLocalAddress() (FullAddress, *Error)
+	GetLocalAddress() (FullAddress, Error)
 
 	// GetRemoteAddress returns the address to which the endpoint is
 	// connected.
-	GetRemoteAddress() (FullAddress, *Error)
+	GetRemoteAddress() (FullAddress, Error)
 
 	// Readiness returns the current readiness of the endpoint. For example,
 	// if waiter.EventIn is set, the endpoint is immediately readable.
 	Readiness(mask waiter.EventMask) waiter.EventMask
 
 	// SetSockOpt sets a socket option.
-	SetSockOpt(opt SettableSocketOption) *Error
+	SetSockOpt(opt SettableSocketOption) Error
 
 	// SetSockOptInt sets a socket option, for simple cases where a value
 	// has the int type.
-	SetSockOptInt(opt SockOptInt, v int) *Error
+	SetSockOptInt(opt SockOptInt, v int) Error
 
 	// GetSockOpt gets a socket option.
-	GetSockOpt(opt GettableSocketOption) *Error
+	GetSockOpt(opt GettableSocketOption) Error
 
 	// GetSockOptInt gets a socket option for simple cases where a return
 	// value has the int type.
-	GetSockOptInt(SockOptInt) (int, *Error)
+	GetSockOptInt(SockOptInt) (int, Error)
 
 	// State returns a socket's lifecycle state. The returned value is
 	// protocol-specific and is primarily used for diagnostics.
@@ -738,7 +603,7 @@ type Endpoint interface {
 	SetOwner(owner PacketOwner)
 
 	// LastError clears and returns the last error reported by the endpoint.
-	LastError() *Error
+	LastError() Error
 
 	// SocketOptions returns the structure which contains all the socket
 	// level options.
diff --git a/pkg/tcpip/tests/integration/forward_test.go b/pkg/tcpip/tests/integration/forward_test.go
index 2b5832c62..38e1881c7 100644
--- a/pkg/tcpip/tests/integration/forward_test.go
+++ b/pkg/tcpip/tests/integration/forward_test.go
@@ -340,7 +340,7 @@ func TestForwarding(t *testing.T) {
 	subTests := []struct {
 		name               string
 		proto              tcpip.TransportProtocolNumber
-		expectedConnectErr *tcpip.Error
+		expectedConnectErr tcpip.Error
 		setupServerSide    func(t *testing.T, ep tcpip.Endpoint, ch <-chan struct{}, clientAddr tcpip.FullAddress) (tcpip.Endpoint, chan struct{})
 		needRemoteAddr     bool
 	}{
@@ -361,7 +361,7 @@ func TestForwarding(t *testing.T) {
 		{
 			name:               "TCP",
 			proto:              tcp.ProtocolNumber,
-			expectedConnectErr: tcpip.ErrConnectStarted,
+			expectedConnectErr: &tcpip.ErrConnectStarted{},
 			setupServerSide: func(t *testing.T, ep tcpip.Endpoint, ch <-chan struct{}, clientAddr tcpip.FullAddress) (tcpip.Endpoint, chan struct{}) {
 				t.Helper()
 
@@ -371,7 +371,7 @@ func TestForwarding(t *testing.T) {
 				var addr tcpip.FullAddress
 				for {
 					newEP, wq, err := ep.Accept(&addr)
-					if err == tcpip.ErrWouldBlock {
+					if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 						<-ch
 						continue
 					}
@@ -420,8 +420,11 @@ func TestForwarding(t *testing.T) {
 						t.Fatalf("epsAndAddrs.clientEP.Bind(%#v): %s", clientAddr, err)
 					}
 
-					if err := epsAndAddrs.clientEP.Connect(serverAddr); err != subTest.expectedConnectErr {
-						t.Fatalf("got epsAndAddrs.clientEP.Connect(%#v) = %s, want = %s", serverAddr, err, subTest.expectedConnectErr)
+					{
+						err := epsAndAddrs.clientEP.Connect(serverAddr)
+						if diff := cmp.Diff(subTest.expectedConnectErr, err); diff != "" {
+							t.Fatalf("unexpected error from epsAndAddrs.clientEP.Connect(%#v), (-want, +got):\n%s", serverAddr, diff)
+						}
 					}
 					if addr, err := epsAndAddrs.clientEP.GetLocalAddress(); err != nil {
 						t.Fatalf("epsAndAddrs.clientEP.GetLocalAddress(): %s", err)
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
index 3c25d1e0c..7069352f2 100644
--- a/pkg/tcpip/tests/integration/link_resolution_test.go
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -257,7 +257,7 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 		name             string
 		netProto         tcpip.NetworkProtocolNumber
 		remoteAddr       tcpip.Address
-		expectedWriteErr *tcpip.Error
+		expectedWriteErr tcpip.Error
 		sockError        tcpip.SockError
 	}{
 		{
@@ -276,9 +276,9 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 			name:             "IPv4 without resolvable remote",
 			netProto:         ipv4.ProtocolNumber,
 			remoteAddr:       ipv4Addr3.AddressWithPrefix.Address,
-			expectedWriteErr: tcpip.ErrNoRoute,
+			expectedWriteErr: &tcpip.ErrNoRoute{},
 			sockError: tcpip.SockError{
-				Err:       tcpip.ErrNoRoute,
+				Err:       &tcpip.ErrNoRoute{},
 				ErrType:   byte(header.ICMPv4DstUnreachable),
 				ErrCode:   byte(header.ICMPv4HostUnreachable),
 				ErrOrigin: tcpip.SockExtErrorOriginICMP,
@@ -298,9 +298,9 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 			name:             "IPv6 without resolvable remote",
 			netProto:         ipv6.ProtocolNumber,
 			remoteAddr:       ipv6Addr3.AddressWithPrefix.Address,
-			expectedWriteErr: tcpip.ErrNoRoute,
+			expectedWriteErr: &tcpip.ErrNoRoute{},
 			sockError: tcpip.SockError{
-				Err:       tcpip.ErrNoRoute,
+				Err:       &tcpip.ErrNoRoute{},
 				ErrType:   byte(header.ICMPv6DstUnreachable),
 				ErrCode:   byte(header.ICMPv6AddressUnreachable),
 				ErrOrigin: tcpip.SockExtErrorOriginICMP6,
@@ -357,18 +357,24 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 
 			remoteAddr := listenerAddr
 			remoteAddr.Addr = test.remoteAddr
-			if err := clientEP.Connect(remoteAddr); err != tcpip.ErrConnectStarted {
-				t.Fatalf("got clientEP.Connect(%#v) = %s, want = %s", remoteAddr, err, tcpip.ErrConnectStarted)
+			{
+				err := clientEP.Connect(remoteAddr)
+				if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+					t.Fatalf("got clientEP.Connect(%#v) = %s, want = %s", remoteAddr, err, &tcpip.ErrConnectStarted{})
+				}
 			}
 
 			// Wait for an error due to link resolution failing, or the endpoint to be
 			// writable.
 			<-ch
-			var r bytes.Reader
-			r.Reset([]byte{0})
-			var wOpts tcpip.WriteOptions
-			if n, err := clientEP.Write(&r, wOpts); err != test.expectedWriteErr {
-				t.Errorf("got clientEP.Write(_, %#v) = (%d, %s), want = (_, %s)", wOpts, n, err, test.expectedWriteErr)
+			{
+				var r bytes.Reader
+				r.Reset([]byte{0})
+				var wOpts tcpip.WriteOptions
+				_, err := clientEP.Write(&r, wOpts)
+				if diff := cmp.Diff(test.expectedWriteErr, err); diff != "" {
+					t.Errorf("unexpected error from clientEP.Write(_, %#v), (-want, +got):\n%s", wOpts, diff)
+				}
 			}
 
 			if test.expectedWriteErr == nil {
@@ -382,7 +388,7 @@ func TestTCPLinkResolutionFailure(t *testing.T) {
 
 			sockErrCmpOpts := []cmp.Option{
 				cmpopts.IgnoreUnexported(tcpip.SockError{}),
-				cmp.Comparer(func(a, b *tcpip.Error) bool {
+				cmp.Comparer(func(a, b tcpip.Error) bool {
 					// tcpip.Error holds an unexported field but the errors netstack uses
 					// are pre defined so we can simply compare pointers.
 					return a == b
@@ -455,10 +461,11 @@ func TestGetLinkAddress(t *testing.T) {
 					host1Stack, _ := setupStack(t, stackOpts, host1NICID, host2NICID)
 
 					ch := make(chan stack.LinkResolutionResult, 1)
-					if err := host1Stack.GetLinkAddress(host1NICID, test.remoteAddr, "", test.netProto, func(r stack.LinkResolutionResult) {
+					err := host1Stack.GetLinkAddress(host1NICID, test.remoteAddr, "", test.netProto, func(r stack.LinkResolutionResult) {
 						ch <- r
-					}); err != tcpip.ErrWouldBlock {
-						t.Fatalf("got host1Stack.GetLinkAddress(%d, %s, '', %d, _) = %s, want = %s", host1NICID, test.remoteAddr, test.netProto, err, tcpip.ErrWouldBlock)
+					})
+					if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+						t.Fatalf("got host1Stack.GetLinkAddress(%d, %s, '', %d, _) = %s, want = %s", host1NICID, test.remoteAddr, test.netProto, err, &tcpip.ErrWouldBlock{})
 					}
 					wantRes := stack.LinkResolutionResult{Success: test.expectedOk}
 					if test.expectedOk {
@@ -572,10 +579,11 @@ func TestRouteResolvedFields(t *testing.T) {
 						wantUnresolvedRouteInfo := wantRouteInfo
 						wantUnresolvedRouteInfo.RemoteLinkAddress = ""
 
-						if err := r.ResolvedFields(func(r stack.ResolvedFieldsResult) {
+						err := r.ResolvedFields(func(r stack.ResolvedFieldsResult) {
 							ch <- r
-						}); err != tcpip.ErrWouldBlock {
-							t.Errorf("got r.ResolvedFields(_) = %s, want = %s", err, tcpip.ErrWouldBlock)
+						})
+						if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+							t.Errorf("got r.ResolvedFields(_) = %s, want = %s", err, &tcpip.ErrWouldBlock{})
 						}
 						if diff := cmp.Diff(stack.ResolvedFieldsResult{RouteInfo: wantRouteInfo, Success: test.expectedSuccess}, <-ch, cmp.AllowUnexported(stack.RouteInfo{})); diff != "" {
 							t.Errorf("route resolve result mismatch (-want +got):\n%s", diff)
@@ -618,7 +626,7 @@ func TestWritePacketsLinkResolution(t *testing.T) {
 		name             string
 		netProto         tcpip.NetworkProtocolNumber
 		remoteAddr       tcpip.Address
-		expectedWriteErr *tcpip.Error
+		expectedWriteErr tcpip.Error
 	}{
 		{
 			name:             "IPv4",
@@ -705,7 +713,7 @@ func TestWritePacketsLinkResolution(t *testing.T) {
 				var rOpts tcpip.ReadOptions
 				res, err := serverEP.Read(&writer, rOpts)
 				if err != nil {
-					if err == tcpip.ErrWouldBlock {
+					if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 						// Should not have anymore bytes to read after we read the sent
 						// number of bytes.
 						if count == len(data) {
@@ -1034,10 +1042,11 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 			// Add a reachable dynamic entry to our neighbor table for the remote.
 			{
 				ch := make(chan stack.LinkResolutionResult, 1)
-				if err := host1Stack.GetLinkAddress(host1NICID, test.neighborAddr, "", test.netProto, func(r stack.LinkResolutionResult) {
+				err := host1Stack.GetLinkAddress(host1NICID, test.neighborAddr, "", test.netProto, func(r stack.LinkResolutionResult) {
 					ch <- r
-				}); err != tcpip.ErrWouldBlock {
-					t.Fatalf("got host1Stack.GetLinkAddress(%d, %s, '', %d, _) = %s, want = %s", host1NICID, test.neighborAddr, test.netProto, err, tcpip.ErrWouldBlock)
+				})
+				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+					t.Fatalf("got host1Stack.GetLinkAddress(%d, %s, '', %d, _) = %s, want = %s", host1NICID, test.neighborAddr, test.netProto, err, &tcpip.ErrWouldBlock{})
 				}
 				if diff := cmp.Diff(stack.LinkResolutionResult{LinkAddress: linkAddr2, Success: true}, <-ch); diff != "" {
 					t.Fatalf("link resolution mismatch (-want +got):\n%s", diff)
@@ -1088,8 +1097,11 @@ func TestTCPConfirmNeighborReachability(t *testing.T) {
 			if err := listenerEP.Listen(1); err != nil {
 				t.Fatalf("listenerEP.Listen(1): %s", err)
 			}
-			if err := clientEP.Connect(listenerAddr); err != tcpip.ErrConnectStarted {
-				t.Fatalf("got clientEP.Connect(%#v) = %s, want = %s", listenerAddr, err, tcpip.ErrConnectStarted)
+			{
+				err := clientEP.Connect(listenerAddr)
+				if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+					t.Fatalf("got clientEP.Connect(%#v) = %s, want = %s", listenerAddr, err, &tcpip.ErrConnectStarted{})
+				}
 			}
 
 			// Wait for the TCP handshake to complete then make sure the neighbor is
diff --git a/pkg/tcpip/tests/integration/loopback_test.go b/pkg/tcpip/tests/integration/loopback_test.go
index 761283b66..ab67762ef 100644
--- a/pkg/tcpip/tests/integration/loopback_test.go
+++ b/pkg/tcpip/tests/integration/loopback_test.go
@@ -37,7 +37,7 @@ var _ ipv6.NDPDispatcher = (*ndpDispatcher)(nil)
 
 type ndpDispatcher struct{}
 
-func (*ndpDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, *tcpip.Error) {
+func (*ndpDispatcher) OnDuplicateAddressDetectionStatus(tcpip.NICID, tcpip.Address, bool, tcpip.Error) {
 }
 
 func (*ndpDispatcher) OnDefaultRouterDiscovered(tcpip.NICID, tcpip.Address) bool {
@@ -262,8 +262,8 @@ func TestLoopbackAcceptAllInSubnetUDP(t *testing.T) {
 				if diff := cmp.Diff(data, buf.Bytes()); diff != "" {
 					t.Errorf("got UDP payload mismatch (-want +got):\n%s", diff)
 				}
-			} else if err != tcpip.ErrWouldBlock {
-				t.Fatalf("got rep.Read = (%v, %s) [with data %x], want = (_, %s)", res, err, buf.Bytes(), tcpip.ErrWouldBlock)
+			} else if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				t.Fatalf("got rep.Read = (%v, %s) [with data %x], want = (_, %s)", res, err, buf.Bytes(), &tcpip.ErrWouldBlock{})
 			}
 		})
 	}
@@ -322,11 +322,14 @@ func TestLoopbackSubnetLifetimeBoundToAddr(t *testing.T) {
 	if err := s.RemoveAddress(nicID, protoAddr.AddressWithPrefix.Address); err != nil {
 		t.Fatalf("s.RemoveAddress(%d, %s): %s", nicID, protoAddr.AddressWithPrefix.Address, err)
 	}
-	if err := r.WritePacket(nil /* gso */, params, stack.NewPacketBuffer(stack.PacketBufferOptions{
-		ReserveHeaderBytes: int(r.MaxHeaderLength()),
-		Data:               data.ToVectorisedView(),
-	})); err != tcpip.ErrInvalidEndpointState {
-		t.Fatalf("got r.WritePacket(nil, %#v, _) = %s, want = %s", params, err, tcpip.ErrInvalidEndpointState)
+	{
+		err := r.WritePacket(nil /* gso */, params, stack.NewPacketBuffer(stack.PacketBufferOptions{
+			ReserveHeaderBytes: int(r.MaxHeaderLength()),
+			Data:               data.ToVectorisedView(),
+		}))
+		if _, ok := err.(*tcpip.ErrInvalidEndpointState); !ok {
+			t.Fatalf("got r.WritePacket(nil, %#v, _) = %s, want = %s", params, err, &tcpip.ErrInvalidEndpointState{})
+		}
 	}
 }
 
@@ -470,13 +473,17 @@ func TestLoopbackAcceptAllInSubnetTCP(t *testing.T) {
 				Addr: test.dstAddr,
 				Port: localPort,
 			}
-			if err := connectingEndpoint.Connect(connectAddr); err != tcpip.ErrConnectStarted {
-				t.Fatalf("connectingEndpoint.Connect(%#v): %s", connectAddr, err)
+			{
+				err := connectingEndpoint.Connect(connectAddr)
+				if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+					t.Fatalf("connectingEndpoint.Connect(%#v): %s", connectAddr, err)
+				}
 			}
 
 			if !test.expectAccept {
-				if _, _, err := listeningEndpoint.Accept(nil); err != tcpip.ErrWouldBlock {
-					t.Fatalf("got listeningEndpoint.Accept(nil) = %s, want = %s", err, tcpip.ErrWouldBlock)
+				_, _, err := listeningEndpoint.Accept(nil)
+				if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+					t.Fatalf("got listeningEndpoint.Accept(nil) = %s, want = %s", err, &tcpip.ErrWouldBlock{})
 				}
 				return
 			}
diff --git a/pkg/tcpip/tests/integration/multicast_broadcast_test.go b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
index 9cc12fa58..d685fdd36 100644
--- a/pkg/tcpip/tests/integration/multicast_broadcast_test.go
+++ b/pkg/tcpip/tests/integration/multicast_broadcast_test.go
@@ -479,8 +479,8 @@ func TestIncomingMulticastAndBroadcast(t *testing.T) {
 				if diff := cmp.Diff(data, buf.Bytes()); diff != "" {
 					t.Errorf("got UDP payload mismatch (-want +got):\n%s", diff)
 				}
-			} else if err != tcpip.ErrWouldBlock {
-				t.Fatalf("got Read = (%v, %s) [with data %x], want = (_, %s)", res, err, buf.Bytes(), tcpip.ErrWouldBlock)
+			} else if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+				t.Fatalf("got Read = (%v, %s) [with data %x], want = (_, %s)", res, err, buf.Bytes(), &tcpip.ErrWouldBlock{})
 			}
 		})
 	}
@@ -761,8 +761,11 @@ func TestUDPAddRemoveMembershipSocketOption(t *testing.T) {
 					if err := ep.SetSockOpt(&removeOpt); err != nil {
 						t.Fatalf("ep.SetSockOpt(&%#v): %s", removeOpt, err)
 					}
-					if _, err := ep.Read(&buf, tcpip.ReadOptions{}); err != tcpip.ErrWouldBlock {
-						t.Fatalf("got ep.Read = (_, %s), want = (_, %s)", err, tcpip.ErrWouldBlock)
+					{
+						_, err := ep.Read(&buf, tcpip.ReadOptions{})
+						if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+							t.Fatalf("got ep.Read = (_, %s), want = (_, %s)", err, &tcpip.ErrWouldBlock{})
+						}
 					}
 				})
 			}
diff --git a/pkg/tcpip/tests/integration/route_test.go b/pkg/tcpip/tests/integration/route_test.go
index 35ee7437a..9654c9527 100644
--- a/pkg/tcpip/tests/integration/route_test.go
+++ b/pkg/tcpip/tests/integration/route_test.go
@@ -81,7 +81,7 @@ func TestLocalPing(t *testing.T) {
 		linkEndpoint       func() stack.LinkEndpoint
 		localAddr          tcpip.Address
 		icmpBuf            func(*testing.T) buffer.View
-		expectedConnectErr *tcpip.Error
+		expectedConnectErr tcpip.Error
 		checkLinkEndpoint  func(t *testing.T, e stack.LinkEndpoint)
 	}{
 		{
@@ -126,7 +126,7 @@ func TestLocalPing(t *testing.T) {
 			netProto:           ipv4.ProtocolNumber,
 			linkEndpoint:       loopback.New,
 			icmpBuf:            ipv4ICMPBuf,
-			expectedConnectErr: tcpip.ErrNoRoute,
+			expectedConnectErr: &tcpip.ErrNoRoute{},
 			checkLinkEndpoint:  func(*testing.T, stack.LinkEndpoint) {},
 		},
 		{
@@ -135,7 +135,7 @@ func TestLocalPing(t *testing.T) {
 			netProto:           ipv6.ProtocolNumber,
 			linkEndpoint:       loopback.New,
 			icmpBuf:            ipv6ICMPBuf,
-			expectedConnectErr: tcpip.ErrNoRoute,
+			expectedConnectErr: &tcpip.ErrNoRoute{},
 			checkLinkEndpoint:  func(*testing.T, stack.LinkEndpoint) {},
 		},
 		{
@@ -144,7 +144,7 @@ func TestLocalPing(t *testing.T) {
 			netProto:           ipv4.ProtocolNumber,
 			linkEndpoint:       channelEP,
 			icmpBuf:            ipv4ICMPBuf,
-			expectedConnectErr: tcpip.ErrNoRoute,
+			expectedConnectErr: &tcpip.ErrNoRoute{},
 			checkLinkEndpoint:  channelEPCheck,
 		},
 		{
@@ -153,7 +153,7 @@ func TestLocalPing(t *testing.T) {
 			netProto:           ipv6.ProtocolNumber,
 			linkEndpoint:       channelEP,
 			icmpBuf:            ipv6ICMPBuf,
-			expectedConnectErr: tcpip.ErrNoRoute,
+			expectedConnectErr: &tcpip.ErrNoRoute{},
 			checkLinkEndpoint:  channelEPCheck,
 		},
 	}
@@ -186,8 +186,11 @@ func TestLocalPing(t *testing.T) {
 			defer ep.Close()
 
 			connAddr := tcpip.FullAddress{Addr: test.localAddr}
-			if err := ep.Connect(connAddr); err != test.expectedConnectErr {
-				t.Fatalf("got ep.Connect(%#v) = %s, want = %s", connAddr, err, test.expectedConnectErr)
+			{
+				err := ep.Connect(connAddr)
+				if diff := cmp.Diff(test.expectedConnectErr, err); diff != "" {
+					t.Fatalf("unexpected error from ep.Connect(%#v), (-want, +got):\n%s", connAddr, diff)
+				}
 			}
 
 			if test.expectedConnectErr != nil {
@@ -263,12 +266,12 @@ func TestLocalUDP(t *testing.T) {
 	subTests := []struct {
 		name             string
 		addAddress       bool
-		expectedWriteErr *tcpip.Error
+		expectedWriteErr tcpip.Error
 	}{
 		{
 			name:             "Unassigned local address",
 			addAddress:       false,
-			expectedWriteErr: tcpip.ErrNoRoute,
+			expectedWriteErr: &tcpip.ErrNoRoute{},
 		},
 		{
 			name:             "Assigned local address",
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index e4bcd3120..3cf05520d 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -84,7 +84,7 @@ type endpoint struct {
 	ops tcpip.SocketOptions
 }
 
-func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	ep := &endpoint{
 		stack: s,
 		TransportEndpointInfo: stack.TransportEndpointInfo{
@@ -159,14 +159,14 @@ func (e *endpoint) SetOwner(owner tcpip.PacketOwner) {
 }
 
 // Read implements tcpip.Endpoint.Read.
-func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	e.rcvMu.Lock()
 
 	if e.rcvList.Empty() {
-		err := tcpip.ErrWouldBlock
+		var err tcpip.Error = &tcpip.ErrWouldBlock{}
 		if e.rcvClosed {
 			e.stats.ReadErrors.ReadClosed.Increment()
-			err = tcpip.ErrClosedForReceive
+			err = &tcpip.ErrClosedForReceive{}
 		}
 		e.rcvMu.Unlock()
 		return tcpip.ReadResult{}, err
@@ -193,7 +193,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 
 	n, err := p.data.ReadTo(dst, opts.Peek)
 	if n == 0 && err != nil {
-		return res, tcpip.ErrBadBuffer
+		return res, &tcpip.ErrBadBuffer{}
 	}
 	res.Count = n
 	return res, nil
@@ -204,7 +204,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 // reacquire the mutex in exclusive mode.
 //
 // Returns true for retry if preparation should be retried.
-func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpip.Error) {
+func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err tcpip.Error) {
 	switch e.state {
 	case stateInitial:
 	case stateConnected:
@@ -212,11 +212,11 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpi
 
 	case stateBound:
 		if to == nil {
-			return false, tcpip.ErrDestinationRequired
+			return false, &tcpip.ErrDestinationRequired{}
 		}
 		return false, nil
 	default:
-		return false, tcpip.ErrInvalidEndpointState
+		return false, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	e.mu.RUnlock()
@@ -241,18 +241,18 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpi
 
 // Write writes data to the endpoint's peer. This method does not block
 // if the data cannot be written.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	n, err := e.write(p, opts)
-	switch err {
+	switch err.(type) {
 	case nil:
 		e.stats.PacketsSent.Increment()
-	case tcpip.ErrMessageTooLong, tcpip.ErrInvalidOptionValue:
+	case *tcpip.ErrMessageTooLong, *tcpip.ErrInvalidOptionValue:
 		e.stats.WriteErrors.InvalidArgs.Increment()
-	case tcpip.ErrClosedForSend:
+	case *tcpip.ErrClosedForSend:
 		e.stats.WriteErrors.WriteClosed.Increment()
-	case tcpip.ErrInvalidEndpointState:
+	case *tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
+	case *tcpip.ErrNoRoute, *tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
 	default:
@@ -262,10 +262,10 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
 	if opts.More {
-		return 0, tcpip.ErrInvalidOptionValue
+		return 0, &tcpip.ErrInvalidOptionValue{}
 	}
 
 	to := opts.To
@@ -275,7 +275,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 
 	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
 	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-		return 0, tcpip.ErrClosedForSend
+		return 0, &tcpip.ErrClosedForSend{}
 	}
 
 	// Prepare for write.
@@ -297,7 +297,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		nicID := to.NIC
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
-				return 0, tcpip.ErrNoRoute
+				return 0, &tcpip.ErrNoRoute{}
 			}
 
 			nicID = e.BindNICID
@@ -320,10 +320,10 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
-		return 0, tcpip.ErrBadBuffer
+		return 0, &tcpip.ErrBadBuffer{}
 	}
 
-	var err *tcpip.Error
+	var err tcpip.Error
 	switch e.NetProto {
 	case header.IPv4ProtocolNumber:
 		err = send4(route, e.ID.LocalPort, v, e.ttl, e.owner)
@@ -340,12 +340,12 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 }
 
 // SetSockOpt sets a socket option.
-func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
+func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	return nil
 }
 
 // SetSockOptInt sets a socket option. Currently not supported.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	switch opt {
 	case tcpip.TTLOption:
 		e.mu.Lock()
@@ -357,7 +357,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
@@ -382,18 +382,18 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 		return v, nil
 
 	default:
-		return -1, tcpip.ErrUnknownProtocolOption
+		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
-func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpip.PacketOwner) *tcpip.Error {
+func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpip.PacketOwner) tcpip.Error {
 	if len(data) < header.ICMPv4MinimumSize {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
@@ -411,7 +411,7 @@ func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpi
 
 	// Linux performs these basic checks.
 	if icmpv4.Type() != header.ICMPv4Echo || icmpv4.Code() != 0 {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	icmpv4.SetChecksum(0)
@@ -425,9 +425,9 @@ func send4(r *stack.Route, ident uint16, data buffer.View, ttl uint8, owner tcpi
 	return r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS}, pkt)
 }
 
-func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Error {
+func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) tcpip.Error {
 	if len(data) < header.ICMPv6EchoMinimumSize {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
@@ -442,7 +442,7 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Err
 	data = data[header.ICMPv6MinimumSize:]
 
 	if icmpv6.Type() != header.ICMPv6EchoRequest || icmpv6.Code() != 0 {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	dataVV := data.ToVectorisedView()
@@ -457,7 +457,7 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Err
 
 // checkV4MappedLocked determines the effective network protocol and converts
 // addr to its canonical form.
-func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, tcpip.Error) {
 	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProtoLocked(addr, false /* v6only */)
 	if err != nil {
 		return tcpip.FullAddress{}, 0, err
@@ -466,12 +466,12 @@ func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddres
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
-func (*endpoint) Disconnect() *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Disconnect() tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Connect connects the endpoint to its peer. Specifying a NIC is optional.
-func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
@@ -486,12 +486,12 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 		}
 
 		if nicID != 0 && nicID != e.BindNICID {
-			return tcpip.ErrInvalidEndpointState
+			return &tcpip.ErrInvalidEndpointState{}
 		}
 
 		nicID = e.BindNICID
 	default:
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	addr, netProto, err := e.checkV4MappedLocked(addr)
@@ -536,19 +536,19 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // ConnectEndpoint is not supported.
-func (*endpoint) ConnectEndpoint(tcpip.Endpoint) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*endpoint) ConnectEndpoint(tcpip.Endpoint) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // Shutdown closes the read and/or write end of the endpoint connection
 // to its peer.
-func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	e.shutdownFlags |= flags
 
 	if e.state != stateConnected {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	if flags&tcpip.ShutdownRead != 0 {
@@ -566,16 +566,16 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
 }
 
 // Listen is not supported by UDP, it just fails.
-func (*endpoint) Listen(int) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Listen(int) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Accept is not supported by UDP, it just fails.
-func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
-	return nil, nil, tcpip.ErrNotSupported
+func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
+	return nil, nil, &tcpip.ErrNotSupported{}
 }
 
-func (e *endpoint) registerWithStack(nicID tcpip.NICID, netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, *tcpip.Error) {
+func (e *endpoint) registerWithStack(nicID tcpip.NICID, netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, tcpip.Error) {
 	if id.LocalPort != 0 {
 		// The endpoint already has a local port, just attempt to
 		// register it.
@@ -584,13 +584,13 @@ func (e *endpoint) registerWithStack(nicID tcpip.NICID, netProtos []tcpip.Networ
 	}
 
 	// We need to find a port for the endpoint.
-	_, err := e.stack.PickEphemeralPort(func(p uint16) (bool, *tcpip.Error) {
+	_, err := e.stack.PickEphemeralPort(func(p uint16) (bool, tcpip.Error) {
 		id.LocalPort = p
 		err := e.stack.RegisterTransportEndpoint(netProtos, e.TransProto, id, e, ports.Flags{}, 0 /* bindtodevice */)
-		switch err {
+		switch err.(type) {
 		case nil:
 			return true, nil
-		case tcpip.ErrPortInUse:
+		case *tcpip.ErrPortInUse:
 			return false, nil
 		default:
 			return false, err
@@ -600,11 +600,11 @@ func (e *endpoint) registerWithStack(nicID tcpip.NICID, netProtos []tcpip.Networ
 	return id, err
 }
 
-func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) bindLocked(addr tcpip.FullAddress) tcpip.Error {
 	// Don't allow binding once endpoint is not in the initial state
 	// anymore.
 	if e.state != stateInitial {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	addr, netProto, err := e.checkV4MappedLocked(addr)
@@ -620,7 +620,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 	if len(addr.Addr) != 0 {
 		// A local address was specified, verify that it's valid.
 		if e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr) == 0 {
-			return tcpip.ErrBadLocalAddress
+			return &tcpip.ErrBadLocalAddress{}
 		}
 	}
 
@@ -648,7 +648,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 
 // Bind binds the endpoint to a specific local address and port.
 // Specifying a NIC is optional.
-func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
@@ -664,7 +664,7 @@ func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // GetLocalAddress returns the address to which the endpoint is bound.
-func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
@@ -676,12 +676,12 @@ func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
 }
 
 // GetRemoteAddress returns the address to which the endpoint is connected.
-func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
 	if e.state != stateConnected {
-		return tcpip.FullAddress{}, tcpip.ErrNotConnected
+		return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 	}
 
 	return tcpip.FullAddress{
@@ -806,7 +806,7 @@ func (e *endpoint) Stats() tcpip.EndpointStats {
 func (*endpoint) Wait() {}
 
 // LastError implements tcpip.Endpoint.LastError.
-func (*endpoint) LastError() *tcpip.Error {
+func (*endpoint) LastError() tcpip.Error {
 	return nil
 }
 
diff --git a/pkg/tcpip/transport/icmp/endpoint_state.go b/pkg/tcpip/transport/icmp/endpoint_state.go
index afe96998a..c9fa9974a 100644
--- a/pkg/tcpip/transport/icmp/endpoint_state.go
+++ b/pkg/tcpip/transport/icmp/endpoint_state.go
@@ -75,7 +75,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 		return
 	}
 
-	var err *tcpip.Error
+	var err tcpip.Error
 	if e.state == stateConnected {
 		e.route, err = e.stack.FindRoute(e.RegisterNICID, e.BindAddr, e.ID.RemoteAddress, e.NetProto, false /* multicastLoop */)
 		if err != nil {
@@ -85,7 +85,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 		e.ID.LocalAddress = e.route.LocalAddress
 	} else if len(e.ID.LocalAddress) != 0 { // stateBound
 		if e.stack.CheckLocalAddress(e.RegisterNICID, e.NetProto, e.ID.LocalAddress) == 0 {
-			panic(tcpip.ErrBadLocalAddress)
+			panic(&tcpip.ErrBadLocalAddress{})
 		}
 	}
 
diff --git a/pkg/tcpip/transport/icmp/protocol.go b/pkg/tcpip/transport/icmp/protocol.go
index 3820e5dc7..47f7dd1cb 100644
--- a/pkg/tcpip/transport/icmp/protocol.go
+++ b/pkg/tcpip/transport/icmp/protocol.go
@@ -59,18 +59,18 @@ func (p *protocol) netProto() tcpip.NetworkProtocolNumber {
 
 // NewEndpoint creates a new icmp endpoint. It implements
 // stack.TransportProtocol.NewEndpoint.
-func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	if netProto != p.netProto() {
-		return nil, tcpip.ErrUnknownProtocol
+		return nil, &tcpip.ErrUnknownProtocol{}
 	}
 	return newEndpoint(p.stack, netProto, p.number, waiterQueue)
 }
 
 // NewRawEndpoint creates a new raw icmp endpoint. It implements
 // stack.TransportProtocol.NewRawEndpoint.
-func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	if netProto != p.netProto() {
-		return nil, tcpip.ErrUnknownProtocol
+		return nil, &tcpip.ErrUnknownProtocol{}
 	}
 	return raw.NewEndpoint(p.stack, netProto, p.number, waiterQueue)
 }
@@ -87,7 +87,7 @@ func (p *protocol) MinimumPacketSize() int {
 }
 
 // ParsePorts in case of ICMP sets src to 0, dst to ICMP ID, and err to nil.
-func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
+func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err tcpip.Error) {
 	switch p.number {
 	case ProtocolNumber4:
 		hdr := header.ICMPv4(v)
@@ -106,13 +106,13 @@ func (*protocol) HandleUnknownDestinationPacket(stack.TransportEndpointID, *stac
 }
 
 // SetOption implements stack.TransportProtocol.SetOption.
-func (*protocol) SetOption(tcpip.SettableTransportProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) SetOption(tcpip.SettableTransportProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Option implements stack.TransportProtocol.Option.
-func (*protocol) Option(tcpip.GettableTransportProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) Option(tcpip.GettableTransportProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Close implements stack.TransportProtocol.Close.
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index d48877677..73bb66830 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -86,15 +86,15 @@ type endpoint struct {
 	boundNIC tcpip.NICID
 
 	// lastErrorMu protects lastError.
-	lastErrorMu sync.Mutex   `state:"nosave"`
-	lastError   *tcpip.Error `state:".(string)"`
+	lastErrorMu sync.Mutex `state:"nosave"`
+	lastError   tcpip.Error
 
 	// ops is used to get socket level options.
 	ops tcpip.SocketOptions
 }
 
 // NewEndpoint returns a new packet endpoint.
-func NewEndpoint(s *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func NewEndpoint(s *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	ep := &endpoint{
 		stack: s,
 		TransportEndpointInfo: stack.TransportEndpointInfo{
@@ -159,16 +159,16 @@ func (ep *endpoint) Close() {
 func (ep *endpoint) ModerateRecvBuf(copied int) {}
 
 // Read implements tcpip.Endpoint.Read.
-func (ep *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (ep *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	ep.rcvMu.Lock()
 
 	// If there's no data to read, return that read would block or that the
 	// endpoint is closed.
 	if ep.rcvList.Empty() {
-		err := tcpip.ErrWouldBlock
+		var err tcpip.Error = &tcpip.ErrWouldBlock{}
 		if ep.rcvClosed {
 			ep.stats.ReadErrors.ReadClosed.Increment()
-			err = tcpip.ErrClosedForReceive
+			err = &tcpip.ErrClosedForReceive{}
 		}
 		ep.rcvMu.Unlock()
 		return tcpip.ReadResult{}, err
@@ -198,49 +198,49 @@ func (ep *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResul
 
 	n, err := packet.data.ReadTo(dst, opts.Peek)
 	if n == 0 && err != nil {
-		return res, tcpip.ErrBadBuffer
+		return res, &tcpip.ErrBadBuffer{}
 	}
 	res.Count = n
 	return res, nil
 }
 
-func (*endpoint) Write(tcpip.Payloader, tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (*endpoint) Write(tcpip.Payloader, tcpip.WriteOptions) (int64, tcpip.Error) {
 	// TODO(gvisor.dev/issue/173): Implement.
-	return 0, tcpip.ErrInvalidOptionValue
+	return 0, &tcpip.ErrInvalidOptionValue{}
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect. Packet sockets cannot be
 // disconnected, and this function always returns tpcip.ErrNotSupported.
-func (*endpoint) Disconnect() *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Disconnect() tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Connect implements tcpip.Endpoint.Connect. Packet sockets cannot be
-// connected, and this function always returnes tcpip.ErrNotSupported.
-func (*endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
-	return tcpip.ErrNotSupported
+// connected, and this function always returnes *tcpip.ErrNotSupported.
+func (*endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Shutdown implements tcpip.Endpoint.Shutdown. Packet sockets cannot be used
-// with Shutdown, and this function always returns tcpip.ErrNotSupported.
-func (*endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
-	return tcpip.ErrNotSupported
+// with Shutdown, and this function always returns *tcpip.ErrNotSupported.
+func (*endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Listen implements tcpip.Endpoint.Listen. Packet sockets cannot be used with
-// Listen, and this function always returns tcpip.ErrNotSupported.
-func (*endpoint) Listen(backlog int) *tcpip.Error {
-	return tcpip.ErrNotSupported
+// Listen, and this function always returns *tcpip.ErrNotSupported.
+func (*endpoint) Listen(backlog int) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Accept implements tcpip.Endpoint.Accept. Packet sockets cannot be used with
-// Accept, and this function always returns tcpip.ErrNotSupported.
-func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
-	return nil, nil, tcpip.ErrNotSupported
+// Accept, and this function always returns *tcpip.ErrNotSupported.
+func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
+	return nil, nil, &tcpip.ErrNotSupported{}
 }
 
 // Bind implements tcpip.Endpoint.Bind.
-func (ep *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+func (ep *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
 	// TODO(gvisor.dev/issue/173): Add Bind support.
 
 	// "By default, all packets of the specified protocol type are passed
@@ -274,14 +274,14 @@ func (ep *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // GetLocalAddress implements tcpip.Endpoint.GetLocalAddress.
-func (*endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
-	return tcpip.FullAddress{}, tcpip.ErrNotSupported
+func (*endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
+	return tcpip.FullAddress{}, &tcpip.ErrNotSupported{}
 }
 
 // GetRemoteAddress implements tcpip.Endpoint.GetRemoteAddress.
-func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	// Even a connected socket doesn't return a remote address.
-	return tcpip.FullAddress{}, tcpip.ErrNotConnected
+	return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 }
 
 // Readiness implements tcpip.Endpoint.Readiness.
@@ -303,19 +303,19 @@ func (ep *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 // SetSockOpt implements tcpip.Endpoint.SetSockOpt. Packet sockets cannot be
 // used with SetSockOpt, and this function always returns
-// tcpip.ErrNotSupported.
-func (ep *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
+// *tcpip.ErrNotSupported.
+func (ep *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	switch opt.(type) {
 	case *tcpip.SocketDetachFilterOption:
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	switch opt {
 	case tcpip.ReceiveBufferSizeOption:
 		// Make sure the receive buffer size is within the min and max
@@ -336,11 +336,11 @@ func (ep *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
-func (ep *endpoint) LastError() *tcpip.Error {
+func (ep *endpoint) LastError() tcpip.Error {
 	ep.lastErrorMu.Lock()
 	defer ep.lastErrorMu.Unlock()
 
@@ -350,19 +350,19 @@ func (ep *endpoint) LastError() *tcpip.Error {
 }
 
 // UpdateLastError implements tcpip.SocketOptionsHandler.UpdateLastError.
-func (ep *endpoint) UpdateLastError(err *tcpip.Error) {
+func (ep *endpoint) UpdateLastError(err tcpip.Error) {
 	ep.lastErrorMu.Lock()
 	ep.lastError = err
 	ep.lastErrorMu.Unlock()
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (ep *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (ep *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
@@ -381,7 +381,7 @@ func (ep *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 		return v, nil
 
 	default:
-		return -1, tcpip.ErrUnknownProtocolOption
+		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
diff --git a/pkg/tcpip/transport/packet/endpoint_state.go b/pkg/tcpip/transport/packet/endpoint_state.go
index 4d98fb051..ece662c0d 100644
--- a/pkg/tcpip/transport/packet/endpoint_state.go
+++ b/pkg/tcpip/transport/packet/endpoint_state.go
@@ -68,24 +68,6 @@ func (ep *endpoint) afterLoad() {
 
 	// TODO(gvisor.dev/173): Once bind is supported, choose the right NIC.
 	if err := ep.stack.RegisterPacketEndpoint(0, ep.netProto, ep); err != nil {
-		panic(*err)
+		panic(err)
 	}
 }
-
-// saveLastError is invoked by stateify.
-func (ep *endpoint) saveLastError() string {
-	if ep.lastError == nil {
-		return ""
-	}
-
-	return ep.lastError.String()
-}
-
-// loadLastError is invoked by stateify.
-func (ep *endpoint) loadLastError(s string) {
-	if s == "" {
-		return
-	}
-
-	ep.lastError = tcpip.StringToError(s)
-}
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 6c6d45188..9c9ccc0ff 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -93,13 +93,13 @@ type endpoint struct {
 }
 
 // NewEndpoint returns a raw  endpoint for the given protocols.
-func NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newEndpoint(stack, netProto, transProto, waiterQueue, true /* associated */)
 }
 
-func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue, associated bool) (tcpip.Endpoint, *tcpip.Error) {
+func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue, associated bool) (tcpip.Endpoint, tcpip.Error) {
 	if netProto != header.IPv4ProtocolNumber && netProto != header.IPv6ProtocolNumber {
-		return nil, tcpip.ErrUnknownProtocol
+		return nil, &tcpip.ErrUnknownProtocol{}
 	}
 
 	e := &endpoint{
@@ -189,16 +189,16 @@ func (e *endpoint) SetOwner(owner tcpip.PacketOwner) {
 }
 
 // Read implements tcpip.Endpoint.Read.
-func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	e.rcvMu.Lock()
 
 	// If there's no data to read, return that read would block or that the
 	// endpoint is closed.
 	if e.rcvList.Empty() {
-		err := tcpip.ErrWouldBlock
+		var err tcpip.Error = &tcpip.ErrWouldBlock{}
 		if e.rcvClosed {
 			e.stats.ReadErrors.ReadClosed.Increment()
-			err = tcpip.ErrClosedForReceive
+			err = &tcpip.ErrClosedForReceive{}
 		}
 		e.rcvMu.Unlock()
 		return tcpip.ReadResult{}, err
@@ -225,37 +225,37 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 
 	n, err := pkt.data.ReadTo(dst, opts.Peek)
 	if n == 0 && err != nil {
-		return res, tcpip.ErrBadBuffer
+		return res, &tcpip.ErrBadBuffer{}
 	}
 	res.Count = n
 	return res, nil
 }
 
 // Write implements tcpip.Endpoint.Write.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// We can create, but not write to, unassociated IPv6 endpoints.
 	if !e.associated && e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber {
-		return 0, tcpip.ErrInvalidOptionValue
+		return 0, &tcpip.ErrInvalidOptionValue{}
 	}
 
 	if opts.To != nil {
 		// Raw sockets do not support sending to a IPv4 address on a IPv6 endpoint.
 		if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(opts.To.Addr) != header.IPv6AddressSize {
-			return 0, tcpip.ErrInvalidOptionValue
+			return 0, &tcpip.ErrInvalidOptionValue{}
 		}
 	}
 
 	n, err := e.write(p, opts)
-	switch err {
+	switch err.(type) {
 	case nil:
 		e.stats.PacketsSent.Increment()
-	case tcpip.ErrMessageTooLong, tcpip.ErrInvalidOptionValue:
+	case *tcpip.ErrMessageTooLong, *tcpip.ErrInvalidOptionValue:
 		e.stats.WriteErrors.InvalidArgs.Increment()
-	case tcpip.ErrClosedForSend:
+	case *tcpip.ErrClosedForSend:
 		e.stats.WriteErrors.WriteClosed.Increment()
-	case tcpip.ErrInvalidEndpointState:
+	case *tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
+	case *tcpip.ErrNoRoute, *tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
 	default:
@@ -265,22 +265,22 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// MSG_MORE is unimplemented. This also means that MSG_EOR is a no-op.
 	if opts.More {
-		return 0, tcpip.ErrInvalidOptionValue
+		return 0, &tcpip.ErrInvalidOptionValue{}
 	}
 
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
 	if e.closed {
-		return 0, tcpip.ErrInvalidEndpointState
+		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	payloadBytes := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, payloadBytes); err != nil {
-		return 0, tcpip.ErrBadBuffer
+		return 0, &tcpip.ErrBadBuffer{}
 	}
 
 	// If this is an unassociated socket and callee provided a nonzero
@@ -288,7 +288,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	if e.ops.GetHeaderIncluded() {
 		ip := header.IPv4(payloadBytes)
 		if !ip.IsValid(len(payloadBytes)) {
-			return 0, tcpip.ErrInvalidOptionValue
+			return 0, &tcpip.ErrInvalidOptionValue{}
 		}
 		dstAddr := ip.DestinationAddress()
 		// Update dstAddr with the address in the IP header, unless
@@ -309,7 +309,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		// If the user doesn't specify a destination, they should have
 		// connected to another address.
 		if !e.connected {
-			return 0, tcpip.ErrDestinationRequired
+			return 0, &tcpip.ErrDestinationRequired{}
 		}
 
 		return e.finishWrite(payloadBytes, e.route)
@@ -319,7 +319,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	// goes through a different NIC than the endpoint was bound to.
 	nic := opts.To.NIC
 	if e.bound && nic != 0 && nic != e.BindNICID {
-		return 0, tcpip.ErrNoRoute
+		return 0, &tcpip.ErrNoRoute{}
 	}
 
 	// Find the route to the destination. If BindAddress is 0,
@@ -336,7 +336,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 
 // finishWrite writes the payload to a route. It resolves the route if
 // necessary. It's really just a helper to make defer unnecessary in Write.
-func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64, *tcpip.Error) {
+func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64, tcpip.Error) {
 	if e.ops.GetHeaderIncluded() {
 		pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 			Data: buffer.View(payloadBytes).ToVectorisedView(),
@@ -363,22 +363,22 @@ func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64,
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
-func (*endpoint) Disconnect() *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Disconnect() tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Connect implements tcpip.Endpoint.Connect.
-func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	// Raw sockets do not support connecting to a IPv4 address on a IPv6 endpoint.
 	if e.TransportEndpointInfo.NetProto == header.IPv6ProtocolNumber && len(addr.Addr) != header.IPv6AddressSize {
-		return tcpip.ErrAddressFamilyNotSupported
+		return &tcpip.ErrAddressFamilyNotSupported{}
 	}
 
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	if e.closed {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	nic := addr.NIC
@@ -393,7 +393,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 		} else if addr.NIC != e.BindNICID {
 			// We're bound and addr specifies a NIC. They must be
 			// the same.
-			return tcpip.ErrInvalidEndpointState
+			return &tcpip.ErrInvalidEndpointState{}
 		}
 	}
 
@@ -424,34 +424,34 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // Shutdown implements tcpip.Endpoint.Shutdown. It's a noop for raw sockets.
-func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	if !e.connected {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 	return nil
 }
 
 // Listen implements tcpip.Endpoint.Listen.
-func (*endpoint) Listen(backlog int) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Listen(backlog int) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Accept implements tcpip.Endpoint.Accept.
-func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
-	return nil, nil, tcpip.ErrNotSupported
+func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
+	return nil, nil, &tcpip.ErrNotSupported{}
 }
 
 // Bind implements tcpip.Endpoint.Bind.
-func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	// If a local address was specified, verify that it's valid.
 	if len(addr.Addr) != 0 && e.stack.CheckLocalAddress(e.RegisterNICID, e.NetProto, addr.Addr) == 0 {
-		return tcpip.ErrBadLocalAddress
+		return &tcpip.ErrBadLocalAddress{}
 	}
 
 	if e.associated {
@@ -471,14 +471,14 @@ func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // GetLocalAddress implements tcpip.Endpoint.GetLocalAddress.
-func (*endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
-	return tcpip.FullAddress{}, tcpip.ErrNotSupported
+func (*endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
+	return tcpip.FullAddress{}, &tcpip.ErrNotSupported{}
 }
 
 // GetRemoteAddress implements tcpip.Endpoint.GetRemoteAddress.
-func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (*endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	// Even a connected socket doesn't return a remote address.
-	return tcpip.FullAddress{}, tcpip.ErrNotConnected
+	return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 }
 
 // Readiness implements tcpip.Endpoint.Readiness.
@@ -499,18 +499,18 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 }
 
 // SetSockOpt implements tcpip.Endpoint.SetSockOpt.
-func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
+func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	switch opt.(type) {
 	case *tcpip.SocketDetachFilterOption:
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	switch opt {
 	case tcpip.ReceiveBufferSizeOption:
 		// Make sure the receive buffer size is within the min and max
@@ -531,17 +531,17 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.ReceiveQueueSizeOption:
 		v := 0
@@ -560,7 +560,7 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 		return v, nil
 
 	default:
-		return -1, tcpip.ErrUnknownProtocolOption
+		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
@@ -680,7 +680,7 @@ func (e *endpoint) Stats() tcpip.EndpointStats {
 func (*endpoint) Wait() {}
 
 // LastError implements tcpip.Endpoint.LastError.
-func (*endpoint) LastError() *tcpip.Error {
+func (*endpoint) LastError() tcpip.Error {
 	return nil
 }
 
diff --git a/pkg/tcpip/transport/raw/endpoint_state.go b/pkg/tcpip/transport/raw/endpoint_state.go
index 65c64d99f..263ec5146 100644
--- a/pkg/tcpip/transport/raw/endpoint_state.go
+++ b/pkg/tcpip/transport/raw/endpoint_state.go
@@ -73,7 +73,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 
 	// If the endpoint is connected, re-connect.
 	if e.connected {
-		var err *tcpip.Error
+		var err tcpip.Error
 		// TODO(gvisor.dev/issue/4906): Properly restore the route with the right
 		// remote address. We used to pass e.remote.RemoteAddress which was
 		// effectively the empty address but since moving e.route to hold a pointer
@@ -89,7 +89,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 	// If the endpoint is bound, re-bind.
 	if e.bound {
 		if e.stack.CheckLocalAddress(e.RegisterNICID, e.NetProto, e.BindAddr) == 0 {
-			panic(tcpip.ErrBadLocalAddress)
+			panic(&tcpip.ErrBadLocalAddress{})
 		}
 	}
 
diff --git a/pkg/tcpip/transport/raw/protocol.go b/pkg/tcpip/transport/raw/protocol.go
index f30aa2a4a..e393b993d 100644
--- a/pkg/tcpip/transport/raw/protocol.go
+++ b/pkg/tcpip/transport/raw/protocol.go
@@ -25,11 +25,11 @@ import (
 type EndpointFactory struct{}
 
 // NewUnassociatedEndpoint implements stack.RawFactory.NewUnassociatedEndpoint.
-func (EndpointFactory) NewUnassociatedEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (EndpointFactory) NewUnassociatedEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newEndpoint(stack, netProto, transProto, waiterQueue, false /* associated */)
 }
 
 // NewPacketEndpoint implements stack.RawFactory.NewPacketEndpoint.
-func (EndpointFactory) NewPacketEndpoint(stack *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (EndpointFactory) NewPacketEndpoint(stack *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return packet.NewEndpoint(stack, cooked, netProto, waiterQueue)
 }
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index e475c36f3..842c1622b 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -199,7 +199,7 @@ func (l *listenContext) isCookieValid(id stack.TransportEndpointID, cookie seqnu
 
 // createConnectingEndpoint creates a new endpoint in a connecting state, with
 // the connection parameters given by the arguments.
-func (l *listenContext) createConnectingEndpoint(s *segment, iss seqnum.Value, irs seqnum.Value, rcvdSynOpts *header.TCPSynOptions, queue *waiter.Queue) (*endpoint, *tcpip.Error) {
+func (l *listenContext) createConnectingEndpoint(s *segment, iss seqnum.Value, irs seqnum.Value, rcvdSynOpts *header.TCPSynOptions, queue *waiter.Queue) (*endpoint, tcpip.Error) {
 	// Create a new endpoint.
 	netProto := l.netProto
 	if netProto == 0 {
@@ -242,7 +242,7 @@ func (l *listenContext) createConnectingEndpoint(s *segment, iss seqnum.Value, i
 // On success, a handshake h is returned with h.ep.mu held.
 //
 // Precondition: if l.listenEP != nil, l.listenEP.mu must be locked.
-func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, queue *waiter.Queue, owner tcpip.PacketOwner) (*handshake, *tcpip.Error) {
+func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, queue *waiter.Queue, owner tcpip.PacketOwner) (*handshake, tcpip.Error) {
 	// Create new endpoint.
 	irs := s.sequenceNumber
 	isn := generateSecureISN(s.id, l.stack.Seed())
@@ -267,7 +267,7 @@ func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, q
 			ep.mu.Unlock()
 			ep.Close()
 
-			return nil, tcpip.ErrConnectionAborted
+			return nil, &tcpip.ErrConnectionAborted{}
 		}
 		l.addPendingEndpoint(ep)
 
@@ -281,7 +281,7 @@ func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, q
 
 			l.removePendingEndpoint(ep)
 
-			return nil, tcpip.ErrConnectionAborted
+			return nil, &tcpip.ErrConnectionAborted{}
 		}
 
 		deferAccept = l.listenEP.deferAccept
@@ -313,7 +313,7 @@ func (l *listenContext) startHandshake(s *segment, opts *header.TCPSynOptions, q
 // established endpoint is returned with e.mu held.
 //
 // Precondition: if l.listenEP != nil, l.listenEP.mu must be locked.
-func (l *listenContext) performHandshake(s *segment, opts *header.TCPSynOptions, queue *waiter.Queue, owner tcpip.PacketOwner) (*endpoint, *tcpip.Error) {
+func (l *listenContext) performHandshake(s *segment, opts *header.TCPSynOptions, queue *waiter.Queue, owner tcpip.PacketOwner) (*endpoint, tcpip.Error) {
 	h, err := l.startHandshake(s, opts, queue, owner)
 	if err != nil {
 		return nil, err
@@ -467,7 +467,7 @@ func (e *endpoint) notifyAborted() {
 // cookies to accept connections.
 //
 // Precondition: if ctx.listenEP != nil, ctx.listenEP.mu must be locked.
-func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header.TCPSynOptions) *tcpip.Error {
+func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header.TCPSynOptions) tcpip.Error {
 	defer s.decRef()
 
 	h, err := ctx.startHandshake(s, opts, &waiter.Queue{}, e.owner)
@@ -522,7 +522,7 @@ func (e *endpoint) acceptQueueIsFull() bool {
 // and needs to handle it.
 //
 // Precondition: if ctx.listenEP != nil, ctx.listenEP.mu must be locked.
-func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) *tcpip.Error {
+func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Error {
 	e.rcvListMu.Lock()
 	rcvClosed := e.rcvClosed
 	e.rcvListMu.Unlock()
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 6df4e6525..4695b66d6 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -226,7 +226,7 @@ func (h *handshake) checkAck(s *segment) bool {
 
 // synSentState handles a segment received when the TCP 3-way handshake is in
 // the SYN-SENT state.
-func (h *handshake) synSentState(s *segment) *tcpip.Error {
+func (h *handshake) synSentState(s *segment) tcpip.Error {
 	// RFC 793, page 37, states that in the SYN-SENT state, a reset is
 	// acceptable if the ack field acknowledges the SYN.
 	if s.flagIsSet(header.TCPFlagRst) {
@@ -237,7 +237,7 @@ func (h *handshake) synSentState(s *segment) *tcpip.Error {
 			h.ep.workerCleanup = true
 			// Although the RFC above calls out ECONNRESET, Linux actually returns
 			// ECONNREFUSED here so we do as well.
-			return tcpip.ErrConnectionRefused
+			return &tcpip.ErrConnectionRefused{}
 		}
 		return nil
 	}
@@ -314,12 +314,12 @@ func (h *handshake) synSentState(s *segment) *tcpip.Error {
 
 // synRcvdState handles a segment received when the TCP 3-way handshake is in
 // the SYN-RCVD state.
-func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
+func (h *handshake) synRcvdState(s *segment) tcpip.Error {
 	if s.flagIsSet(header.TCPFlagRst) {
 		// RFC 793, page 37, states that in the SYN-RCVD state, a reset
 		// is acceptable if the sequence number is in the window.
 		if s.sequenceNumber.InWindow(h.ackNum, h.rcvWnd) {
-			return tcpip.ErrConnectionRefused
+			return &tcpip.ErrConnectionRefused{}
 		}
 		return nil
 	}
@@ -349,7 +349,7 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
 		h.ep.sendRaw(buffer.VectorisedView{}, header.TCPFlagRst|header.TCPFlagAck, seq, ack, 0)
 
 		if !h.active {
-			return tcpip.ErrInvalidEndpointState
+			return &tcpip.ErrInvalidEndpointState{}
 		}
 
 		h.resetState()
@@ -412,7 +412,7 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
 	return nil
 }
 
-func (h *handshake) handleSegment(s *segment) *tcpip.Error {
+func (h *handshake) handleSegment(s *segment) tcpip.Error {
 	h.sndWnd = s.window
 	if !s.flagIsSet(header.TCPFlagSyn) && h.sndWndScale > 0 {
 		h.sndWnd <<= uint8(h.sndWndScale)
@@ -429,7 +429,7 @@ func (h *handshake) handleSegment(s *segment) *tcpip.Error {
 
 // processSegments goes through the segment queue and processes up to
 // maxSegmentsPerWake (if they're available).
-func (h *handshake) processSegments() *tcpip.Error {
+func (h *handshake) processSegments() tcpip.Error {
 	for i := 0; i < maxSegmentsPerWake; i++ {
 		s := h.ep.segmentQueue.dequeue()
 		if s == nil {
@@ -505,7 +505,7 @@ func (h *handshake) start() {
 }
 
 // complete completes the TCP 3-way handshake initiated by h.start().
-func (h *handshake) complete() *tcpip.Error {
+func (h *handshake) complete() tcpip.Error {
 	// Set up the wakers.
 	var s sleep.Sleeper
 	resendWaker := sleep.Waker{}
@@ -555,7 +555,7 @@ func (h *handshake) complete() *tcpip.Error {
 		case wakerForNotification:
 			n := h.ep.fetchNotifications()
 			if (n&notifyClose)|(n&notifyAbort) != 0 {
-				return tcpip.ErrAborted
+				return &tcpip.ErrAborted{}
 			}
 			if n&notifyDrain != 0 {
 				for !h.ep.segmentQueue.empty() {
@@ -593,19 +593,19 @@ type backoffTimer struct {
 	t          *time.Timer
 }
 
-func newBackoffTimer(timeout, maxTimeout time.Duration, f func()) (*backoffTimer, *tcpip.Error) {
+func newBackoffTimer(timeout, maxTimeout time.Duration, f func()) (*backoffTimer, tcpip.Error) {
 	if timeout > maxTimeout {
-		return nil, tcpip.ErrTimeout
+		return nil, &tcpip.ErrTimeout{}
 	}
 	bt := &backoffTimer{timeout: timeout, maxTimeout: maxTimeout}
 	bt.t = time.AfterFunc(timeout, f)
 	return bt, nil
 }
 
-func (bt *backoffTimer) reset() *tcpip.Error {
+func (bt *backoffTimer) reset() tcpip.Error {
 	bt.timeout *= 2
 	if bt.timeout > MaxRTO {
-		return tcpip.ErrTimeout
+		return &tcpip.ErrTimeout{}
 	}
 	bt.t.Reset(bt.timeout)
 	return nil
@@ -706,7 +706,7 @@ type tcpFields struct {
 	txHash uint32
 }
 
-func (e *endpoint) sendSynTCP(r *stack.Route, tf tcpFields, opts header.TCPSynOptions) *tcpip.Error {
+func (e *endpoint) sendSynTCP(r *stack.Route, tf tcpFields, opts header.TCPSynOptions) tcpip.Error {
 	tf.opts = makeSynOptions(opts)
 	// We ignore SYN send errors and let the callers re-attempt send.
 	if err := e.sendTCP(r, tf, buffer.VectorisedView{}, nil); err != nil {
@@ -716,7 +716,7 @@ func (e *endpoint) sendSynTCP(r *stack.Route, tf tcpFields, opts header.TCPSynOp
 	return nil
 }
 
-func (e *endpoint) sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO) *tcpip.Error {
+func (e *endpoint) sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO) tcpip.Error {
 	tf.txHash = e.txHash
 	if err := sendTCP(r, tf, data, gso, e.owner); err != nil {
 		e.stats.SendErrors.SegmentSendToNetworkFailed.Increment()
@@ -755,7 +755,7 @@ func buildTCPHdr(r *stack.Route, tf tcpFields, pkt *stack.PacketBuffer, gso *sta
 	}
 }
 
-func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) *tcpip.Error {
+func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
 	// We need to shallow clone the VectorisedView here as ReadToView will
 	// split the VectorisedView and Trim underlying views as it splits. Not
 	// doing the clone here will cause the underlying views of data itself
@@ -803,7 +803,7 @@ func sendTCPBatch(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso
 
 // sendTCP sends a TCP segment with the provided options via the provided
 // network endpoint and under the provided identity.
-func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) *tcpip.Error {
+func sendTCP(r *stack.Route, tf tcpFields, data buffer.VectorisedView, gso *stack.GSO, owner tcpip.PacketOwner) tcpip.Error {
 	optLen := len(tf.opts)
 	if tf.rcvWnd > math.MaxUint16 {
 		tf.rcvWnd = math.MaxUint16
@@ -875,7 +875,7 @@ func (e *endpoint) makeOptions(sackBlocks []header.SACKBlock) []byte {
 }
 
 // sendRaw sends a TCP segment to the endpoint's peer.
-func (e *endpoint) sendRaw(data buffer.VectorisedView, flags byte, seq, ack seqnum.Value, rcvWnd seqnum.Size) *tcpip.Error {
+func (e *endpoint) sendRaw(data buffer.VectorisedView, flags byte, seq, ack seqnum.Value, rcvWnd seqnum.Size) tcpip.Error {
 	var sackBlocks []header.SACKBlock
 	if e.EndpointState() == StateEstablished && e.rcv.pendingRcvdSegments.Len() > 0 && (flags&header.TCPFlagAck != 0) {
 		sackBlocks = e.sack.Blocks[:e.sack.NumBlocks]
@@ -941,12 +941,14 @@ func (e *endpoint) handleClose() {
 // error code and sends a RST if and only if the error is not ErrConnectionReset
 // indicating that the connection is being reset due to receiving a RST. This
 // method must only be called from the protocol goroutine.
-func (e *endpoint) resetConnectionLocked(err *tcpip.Error) {
+func (e *endpoint) resetConnectionLocked(err tcpip.Error) {
 	// Only send a reset if the connection is being aborted for a reason
 	// other than receiving a reset.
 	e.setEndpointState(StateError)
 	e.hardError = err
-	if err != tcpip.ErrConnectionReset && err != tcpip.ErrTimeout {
+	switch err.(type) {
+	case *tcpip.ErrConnectionReset, *tcpip.ErrTimeout:
+	default:
 		// The exact sequence number to be used for the RST is the same as the
 		// one used by Linux. We need to handle the case of window being shrunk
 		// which can cause sndNxt to be outside the acceptable window on the
@@ -1056,7 +1058,7 @@ func (e *endpoint) drainClosingSegmentQueue() {
 	}
 }
 
-func (e *endpoint) handleReset(s *segment) (ok bool, err *tcpip.Error) {
+func (e *endpoint) handleReset(s *segment) (ok bool, err tcpip.Error) {
 	if e.rcv.acceptable(s.sequenceNumber, 0) {
 		// RFC 793, page 37 states that "in all states
 		// except SYN-SENT, all reset (RST) segments are
@@ -1084,7 +1086,7 @@ func (e *endpoint) handleReset(s *segment) (ok bool, err *tcpip.Error) {
 		//  delete the TCB, and return.
 		case StateCloseWait:
 			e.transitionToStateCloseLocked()
-			e.hardError = tcpip.ErrAborted
+			e.hardError = &tcpip.ErrAborted{}
 			e.notifyProtocolGoroutine(notifyTickleWorker)
 			return false, nil
 		default:
@@ -1097,14 +1099,14 @@ func (e *endpoint) handleReset(s *segment) (ok bool, err *tcpip.Error) {
 			// handleSegment is invoked from the processor goroutine
 			// rather than the worker goroutine.
 			e.notifyProtocolGoroutine(notifyResetByPeer)
-			return false, tcpip.ErrConnectionReset
+			return false, &tcpip.ErrConnectionReset{}
 		}
 	}
 	return true, nil
 }
 
 // handleSegments processes all inbound segments.
-func (e *endpoint) handleSegments(fastPath bool) *tcpip.Error {
+func (e *endpoint) handleSegments(fastPath bool) tcpip.Error {
 	checkRequeue := true
 	for i := 0; i < maxSegmentsPerWake; i++ {
 		if e.EndpointState().closed() {
@@ -1151,7 +1153,7 @@ func (e *endpoint) probeSegment() {
 
 // handleSegment handles a given segment and notifies the worker goroutine if
 // if the connection should be terminated.
-func (e *endpoint) handleSegment(s *segment) (cont bool, err *tcpip.Error) {
+func (e *endpoint) handleSegment(s *segment) (cont bool, err tcpip.Error) {
 	// Invoke the tcp probe if installed. The tcp probe function will update
 	// the TCPEndpointState after the segment is processed.
 	defer e.probeSegment()
@@ -1225,7 +1227,7 @@ func (e *endpoint) handleSegment(s *segment) (cont bool, err *tcpip.Error) {
 // keepaliveTimerExpired is called when the keepaliveTimer fires. We send TCP
 // keepalive packets periodically when the connection is idle. If we don't hear
 // from the other side after a number of tries, we terminate the connection.
-func (e *endpoint) keepaliveTimerExpired() *tcpip.Error {
+func (e *endpoint) keepaliveTimerExpired() tcpip.Error {
 	userTimeout := e.userTimeout
 
 	e.keepalive.Lock()
@@ -1239,13 +1241,13 @@ func (e *endpoint) keepaliveTimerExpired() *tcpip.Error {
 	if userTimeout != 0 && time.Since(e.rcv.lastRcvdAckTime) >= userTimeout && e.keepalive.unacked > 0 {
 		e.keepalive.Unlock()
 		e.stack.Stats().TCP.EstablishedTimedout.Increment()
-		return tcpip.ErrTimeout
+		return &tcpip.ErrTimeout{}
 	}
 
 	if e.keepalive.unacked >= e.keepalive.count {
 		e.keepalive.Unlock()
 		e.stack.Stats().TCP.EstablishedTimedout.Increment()
-		return tcpip.ErrTimeout
+		return &tcpip.ErrTimeout{}
 	}
 
 	// RFC1122 4.2.3.6: TCP keepalive is a dataless ACK with
@@ -1289,7 +1291,7 @@ func (e *endpoint) disableKeepaliveTimer() {
 // protocolMainLoop is the main loop of the TCP protocol. It runs in its own
 // goroutine and is responsible for sending segments and handling received
 // segments.
-func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{}) *tcpip.Error {
+func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{}) tcpip.Error {
 	e.mu.Lock()
 	var closeTimer *time.Timer
 	var closeWaker sleep.Waker
@@ -1355,25 +1357,25 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 	// wakes up.
 	funcs := []struct {
 		w *sleep.Waker
-		f func() *tcpip.Error
+		f func() tcpip.Error
 	}{
 		{
 			w: &e.sndWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				e.handleWrite()
 				return nil
 			},
 		},
 		{
 			w: &e.sndCloseWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				e.handleClose()
 				return nil
 			},
 		},
 		{
 			w: &closeWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				// This means the socket is being closed due
 				// to the TCP-FIN-WAIT2 timeout was hit. Just
 				// mark the socket as closed.
@@ -1384,10 +1386,10 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		},
 		{
 			w: &e.snd.resendWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				if !e.snd.retransmitTimerExpired() {
 					e.stack.Stats().TCP.EstablishedTimedout.Increment()
-					return tcpip.ErrTimeout
+					return &tcpip.ErrTimeout{}
 				}
 				return nil
 			},
@@ -1398,7 +1400,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		},
 		{
 			w: &e.newSegmentWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				return e.handleSegments(false /* fastPath */)
 			},
 		},
@@ -1408,7 +1410,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		},
 		{
 			w: &e.notificationWaker,
-			f: func() *tcpip.Error {
+			f: func() tcpip.Error {
 				n := e.fetchNotifications()
 				if n&notifyNonZeroReceiveWindow != 0 {
 					e.rcv.nonZeroWindow()
@@ -1425,11 +1427,11 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 				}
 
 				if n&notifyReset != 0 || n&notifyAbort != 0 {
-					return tcpip.ErrConnectionAborted
+					return &tcpip.ErrConnectionAborted{}
 				}
 
 				if n&notifyResetByPeer != 0 {
-					return tcpip.ErrConnectionReset
+					return &tcpip.ErrConnectionReset{}
 				}
 
 				if n&notifyClose != 0 && closeTimer == nil {
@@ -1508,7 +1510,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 
 	// Main loop. Handle segments until both send and receive ends of the
 	// connection have completed.
-	cleanupOnError := func(err *tcpip.Error) {
+	cleanupOnError := func(err tcpip.Error) {
 		e.stack.Stats().TCP.CurrentConnected.Decrement()
 		e.workerCleanup = true
 		if err != nil {
diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index 809c88732..2d90246e4 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -37,7 +37,7 @@ func TestV4MappedConnectOnV6Only(t *testing.T) {
 
 	// Start connection attempt, it must fail.
 	err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestV4MappedAddr, Port: context.TestPort})
-	if err != tcpip.ErrNoRoute {
+	if _, ok := err.(*tcpip.ErrNoRoute); !ok {
 		t.Fatalf("Unexpected return value from Connect: %v", err)
 	}
 }
@@ -49,7 +49,7 @@ func testV4Connect(t *testing.T, c *context.Context, checkers ...checker.Network
 	defer c.WQ.EventUnregister(&we)
 
 	err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestV4MappedAddr, Port: context.TestPort})
-	if err != tcpip.ErrConnectStarted {
+	if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 		t.Fatalf("Unexpected return value from Connect: %v", err)
 	}
 
@@ -156,7 +156,7 @@ func testV6Connect(t *testing.T, c *context.Context, checkers ...checker.Network
 	defer c.WQ.EventUnregister(&we)
 
 	err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestV6Addr, Port: context.TestPort})
-	if err != tcpip.ErrConnectStarted {
+	if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 		t.Fatalf("Unexpected return value from Connect: %v", err)
 	}
 
@@ -391,7 +391,7 @@ func testV4Accept(t *testing.T, c *context.Context) {
 	defer c.WQ.EventUnregister(&we)
 
 	nep, _, err := c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -525,7 +525,7 @@ func TestV6AcceptOnV6(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 	var addr tcpip.FullAddress
 	_, _, err := c.EP.Accept(&addr)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -549,7 +549,7 @@ func TestV4AcceptOnV4(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
@@ -613,7 +613,7 @@ func testV4ListenClose(t *testing.T, c *context.Context) {
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
 	nep, _, err := c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -635,7 +635,7 @@ func TestV4ListenCloseOnV4(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index bfa5b01fb..9a53f0d56 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -386,12 +386,12 @@ type endpoint struct {
 	// hardError is meaningful only when state is stateError. It stores the
 	// error to be returned when read/write syscalls are called and the
 	// endpoint is in this state. hardError is protected by endpoint mu.
-	hardError *tcpip.Error `state:".(string)"`
+	hardError tcpip.Error
 
 	// lastError represents the last error that the endpoint reported;
 	// access to it is protected by the following mutex.
-	lastErrorMu sync.Mutex   `state:"nosave"`
-	lastError   *tcpip.Error `state:".(string)"`
+	lastErrorMu sync.Mutex `state:"nosave"`
+	lastError   tcpip.Error
 
 	// rcvReadMu synchronizes calls to Read.
 	//
@@ -1059,7 +1059,7 @@ func (e *endpoint) Close() {
 		if isResetState {
 			// Close the endpoint without doing full shutdown and
 			// send a RST.
-			e.resetConnectionLocked(tcpip.ErrConnectionAborted)
+			e.resetConnectionLocked(&tcpip.ErrConnectionAborted{})
 			e.closeNoShutdownLocked()
 
 			// Wake up worker to close the endpoint.
@@ -1293,14 +1293,14 @@ func (e *endpoint) SetOwner(owner tcpip.PacketOwner) {
 }
 
 // Preconditions: e.mu must be held to call this function.
-func (e *endpoint) hardErrorLocked() *tcpip.Error {
+func (e *endpoint) hardErrorLocked() tcpip.Error {
 	err := e.hardError
 	e.hardError = nil
 	return err
 }
 
 // Preconditions: e.mu must be held to call this function.
-func (e *endpoint) lastErrorLocked() *tcpip.Error {
+func (e *endpoint) lastErrorLocked() tcpip.Error {
 	e.lastErrorMu.Lock()
 	defer e.lastErrorMu.Unlock()
 	err := e.lastError
@@ -1309,7 +1309,7 @@ func (e *endpoint) lastErrorLocked() *tcpip.Error {
 }
 
 // LastError implements tcpip.Endpoint.LastError.
-func (e *endpoint) LastError() *tcpip.Error {
+func (e *endpoint) LastError() tcpip.Error {
 	e.LockUser()
 	defer e.UnlockUser()
 	if err := e.hardErrorLocked(); err != nil {
@@ -1319,7 +1319,7 @@ func (e *endpoint) LastError() *tcpip.Error {
 }
 
 // UpdateLastError implements tcpip.SocketOptionsHandler.UpdateLastError.
-func (e *endpoint) UpdateLastError(err *tcpip.Error) {
+func (e *endpoint) UpdateLastError(err tcpip.Error) {
 	e.LockUser()
 	e.lastErrorMu.Lock()
 	e.lastError = err
@@ -1328,7 +1328,7 @@ func (e *endpoint) UpdateLastError(err *tcpip.Error) {
 }
 
 // Read implements tcpip.Endpoint.Read.
-func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	e.rcvReadMu.Lock()
 	defer e.rcvReadMu.Unlock()
 
@@ -1337,7 +1337,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 	// can remove segments from the list through commitRead().
 	first, last, serr := e.startRead()
 	if serr != nil {
-		if serr == tcpip.ErrClosedForReceive {
+		if _, ok := serr.(*tcpip.ErrClosedForReceive); ok {
 			e.stats.ReadErrors.ReadClosed.Increment()
 		}
 		return tcpip.ReadResult{}, serr
@@ -1377,7 +1377,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 
 	// If something is read, we must report it. Report error when nothing is read.
 	if done == 0 && err != nil {
-		return tcpip.ReadResult{}, tcpip.ErrBadBuffer
+		return tcpip.ReadResult{}, &tcpip.ErrBadBuffer{}
 	}
 	return tcpip.ReadResult{
 		Count: done,
@@ -1389,7 +1389,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 // inclusive range of segments that can be read.
 //
 // Precondition: e.rcvReadMu must be held.
-func (e *endpoint) startRead() (first, last *segment, err *tcpip.Error) {
+func (e *endpoint) startRead() (first, last *segment, err tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -1398,7 +1398,7 @@ func (e *endpoint) startRead() (first, last *segment, err *tcpip.Error) {
 	// on a receive. It can expect to read any data after the handshake
 	// is complete. RFC793, section 3.9, p58.
 	if e.EndpointState() == StateSynSent {
-		return nil, nil, tcpip.ErrWouldBlock
+		return nil, nil, &tcpip.ErrWouldBlock{}
 	}
 
 	// The endpoint can be read if it's connected, or if it's already closed
@@ -1414,17 +1414,17 @@ func (e *endpoint) startRead() (first, last *segment, err *tcpip.Error) {
 			if err := e.hardErrorLocked(); err != nil {
 				return nil, nil, err
 			}
-			return nil, nil, tcpip.ErrClosedForReceive
+			return nil, nil, &tcpip.ErrClosedForReceive{}
 		}
 		e.stats.ReadErrors.NotConnected.Increment()
-		return nil, nil, tcpip.ErrNotConnected
+		return nil, nil, &tcpip.ErrNotConnected{}
 	}
 
 	if e.rcvBufUsed == 0 {
 		if e.rcvClosed || !e.EndpointState().connected() {
-			return nil, nil, tcpip.ErrClosedForReceive
+			return nil, nil, &tcpip.ErrClosedForReceive{}
 		}
-		return nil, nil, tcpip.ErrWouldBlock
+		return nil, nil, &tcpip.ErrWouldBlock{}
 	}
 
 	return e.rcvList.Front(), e.rcvList.Back(), nil
@@ -1476,39 +1476,39 @@ func (e *endpoint) commitRead(done int) *segment {
 // moment. If the endpoint is not writable then it returns an error
 // indicating the reason why it's not writable.
 // Caller must hold e.mu and e.sndBufMu
-func (e *endpoint) isEndpointWritableLocked() (int, *tcpip.Error) {
+func (e *endpoint) isEndpointWritableLocked() (int, tcpip.Error) {
 	// The endpoint cannot be written to if it's not connected.
 	switch s := e.EndpointState(); {
 	case s == StateError:
 		if err := e.hardErrorLocked(); err != nil {
 			return 0, err
 		}
-		return 0, tcpip.ErrClosedForSend
+		return 0, &tcpip.ErrClosedForSend{}
 	case !s.connecting() && !s.connected():
-		return 0, tcpip.ErrClosedForSend
+		return 0, &tcpip.ErrClosedForSend{}
 	case s.connecting():
 		// As per RFC793, page 56, a send request arriving when in connecting
 		// state, can be queued to be completed after the state becomes
 		// connected. Return an error code for the caller of endpoint Write to
 		// try again, until the connection handshake is complete.
-		return 0, tcpip.ErrWouldBlock
+		return 0, &tcpip.ErrWouldBlock{}
 	}
 
 	// Check if the connection has already been closed for sends.
 	if e.sndClosed {
-		return 0, tcpip.ErrClosedForSend
+		return 0, &tcpip.ErrClosedForSend{}
 	}
 
 	sndBufSize := e.getSendBufferSize()
 	avail := sndBufSize - e.sndBufUsed
 	if avail <= 0 {
-		return 0, tcpip.ErrWouldBlock
+		return 0, &tcpip.ErrWouldBlock{}
 	}
 	return avail, nil
 }
 
 // Write writes data to the endpoint's peer.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	// Linux completely ignores any address passed to sendto(2) for TCP sockets
 	// (without the MSG_FASTOPEN flag). Corking is unimplemented, so opts.More
 	// and opts.EndOfRecord are also ignored.
@@ -1516,7 +1516,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	e.LockUser()
 	defer e.UnlockUser()
 
-	nextSeg, n, err := func() (*segment, int, *tcpip.Error) {
+	nextSeg, n, err := func() (*segment, int, tcpip.Error) {
 		e.sndBufMu.Lock()
 		defer e.sndBufMu.Unlock()
 
@@ -1526,7 +1526,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 			return nil, 0, err
 		}
 
-		v, err := func() ([]byte, *tcpip.Error) {
+		v, err := func() ([]byte, tcpip.Error) {
 			// We can release locks while copying data.
 			//
 			// This is not possible if atomic is set, because we can't allow the
@@ -1549,7 +1549,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 			}
 			v := make([]byte, avail)
 			if _, err := io.ReadFull(p, v); err != nil {
-				return nil, tcpip.ErrBadBuffer
+				return nil, &tcpip.ErrBadBuffer{}
 			}
 			return v, nil
 		}()
@@ -1702,7 +1702,7 @@ func (e *endpoint) getSendBufferSize() int {
 }
 
 // SetSockOptInt sets a socket option.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	// Lower 2 bits represents ECN bits. RFC 3168, section 23.1
 	const inetECNMask = 3
 
@@ -1730,7 +1730,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 	case tcpip.MaxSegOption:
 		userMSS := v
 		if userMSS < header.TCPMinimumMSS || userMSS > header.TCPMaximumMSS {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		e.LockUser()
 		e.userMSS = uint16(userMSS)
@@ -1741,7 +1741,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 		// Return not supported if attempting to set this option to
 		// anything other than path MTU discovery disabled.
 		if v != tcpip.PMTUDiscoveryDont {
-			return tcpip.ErrNotSupported
+			return &tcpip.ErrNotSupported{}
 		}
 
 	case tcpip.ReceiveBufferSizeOption:
@@ -1801,7 +1801,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 
 	case tcpip.TCPSynCountOption:
 		if v < 1 || v > 255 {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		e.LockUser()
 		e.maxSynRetries = uint8(v)
@@ -1817,7 +1817,7 @@ func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
 				return nil
 			default:
 				e.UnlockUser()
-				return tcpip.ErrInvalidOptionValue
+				return &tcpip.ErrInvalidOptionValue{}
 			}
 		}
 		var rs tcpip.TCPReceiveBufferSizeRangeOption
@@ -1838,7 +1838,7 @@ func (e *endpoint) HasNIC(id int32) bool {
 }
 
 // SetSockOpt sets a socket option.
-func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
+func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	switch v := opt.(type) {
 	case *tcpip.KeepaliveIdleOption:
 		e.keepalive.Lock()
@@ -1884,7 +1884,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 
 		// Linux returns ENOENT when an invalid congestion
 		// control algorithm is specified.
-		return tcpip.ErrNoSuchFile
+		return &tcpip.ErrNoSuchFile{}
 
 	case *tcpip.TCPLingerTimeoutOption:
 		e.LockUser()
@@ -1927,13 +1927,13 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 }
 
 // readyReceiveSize returns the number of bytes ready to be received.
-func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
+func (e *endpoint) readyReceiveSize() (int, tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
 	// The endpoint cannot be in listen state.
 	if e.EndpointState() == StateListen {
-		return 0, tcpip.ErrInvalidEndpointState
+		return 0, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	e.rcvListMu.Lock()
@@ -1943,7 +1943,7 @@ func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.KeepaliveCountOption:
 		e.keepalive.Lock()
@@ -2007,7 +2007,7 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 		return 1, nil
 
 	default:
-		return -1, tcpip.ErrUnknownProtocolOption
+		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
@@ -2035,7 +2035,7 @@ func (e *endpoint) getTCPInfo() tcpip.TCPInfoOption {
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
+func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
 	switch o := opt.(type) {
 	case *tcpip.TCPInfoOption:
 		*o = e.getTCPInfo()
@@ -2084,14 +2084,14 @@ func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
 		}
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 	return nil
 }
 
 // checkV4MappedLocked determines the effective network protocol and converts
 // addr to its canonical form.
-func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, tcpip.Error) {
 	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProtoLocked(addr, e.ops.GetV6Only())
 	if err != nil {
 		return tcpip.FullAddress{}, 0, err
@@ -2100,18 +2100,20 @@ func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddres
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
-func (*endpoint) Disconnect() *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Disconnect() tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Connect connects the endpoint to its peer.
-func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	err := e.connect(addr, true, true)
-	if err != nil && !err.IgnoreStats() {
-		// Connect failed. Let's wake up any waiters.
-		e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
-		e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
-		e.stats.FailedConnectionAttempts.Increment()
+	if err != nil {
+		if !err.IgnoreStats() {
+			// Connect failed. Let's wake up any waiters.
+			e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+			e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
+			e.stats.FailedConnectionAttempts.Increment()
+		}
 	}
 	return err
 }
@@ -2122,7 +2124,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 // created (so no new handshaking is done); for stack-accepted connections not
 // yet accepted by the app, they are restored without running the main goroutine
 // here.
-func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tcpip.Error {
+func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) tcpip.Error {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2141,7 +2143,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 			return nil
 		}
 		// Otherwise return that it's already connected.
-		return tcpip.ErrAlreadyConnected
+		return &tcpip.ErrAlreadyConnected{}
 	}
 
 	nicID := addr.NIC
@@ -2154,7 +2156,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 		}
 
 		if nicID != 0 && nicID != e.boundNICID {
-			return tcpip.ErrNoRoute
+			return &tcpip.ErrNoRoute{}
 		}
 
 		nicID = e.boundNICID
@@ -2166,16 +2168,16 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 	case StateConnecting, StateSynSent, StateSynRecv:
 		// A connection request has already been issued but hasn't completed
 		// yet.
-		return tcpip.ErrAlreadyConnecting
+		return &tcpip.ErrAlreadyConnecting{}
 
 	case StateError:
 		if err := e.hardErrorLocked(); err != nil {
 			return err
 		}
-		return tcpip.ErrConnectionAborted
+		return &tcpip.ErrConnectionAborted{}
 
 	default:
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// Find a route to the desired destination.
@@ -2231,12 +2233,12 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 		}
 
 		bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
-		if _, err := e.stack.PickEphemeralPortStable(portOffset, func(p uint16) (bool, *tcpip.Error) {
+		if _, err := e.stack.PickEphemeralPortStable(portOffset, func(p uint16) (bool, tcpip.Error) {
 			if sameAddr && p == e.ID.RemotePort {
 				return false, nil
 			}
 			if _, err := e.stack.ReservePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, bindToDevice, addr, nil /* testPort */); err != nil {
-				if err != tcpip.ErrPortInUse || !reuse {
+				if _, ok := err.(*tcpip.ErrPortInUse); !ok || !reuse {
 					return false, nil
 				}
 				transEPID := e.ID
@@ -2282,7 +2284,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 			id.LocalPort = p
 			if err := e.stack.RegisterTransportEndpoint(netProtos, ProtocolNumber, id, e, e.portFlags, bindToDevice); err != nil {
 				e.stack.ReleasePort(netProtos, ProtocolNumber, e.ID.LocalAddress, p, e.portFlags, bindToDevice, addr)
-				if err == tcpip.ErrPortInUse {
+				if _, ok := err.(*tcpip.ErrPortInUse); ok {
 					return false, nil
 				}
 				return false, err
@@ -2337,23 +2339,23 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
 		go e.protocolMainLoop(handshake, nil) // S/R-SAFE: will be drained before save.
 	}
 
-	return tcpip.ErrConnectStarted
+	return &tcpip.ErrConnectStarted{}
 }
 
 // ConnectEndpoint is not supported.
-func (*endpoint) ConnectEndpoint(tcpip.Endpoint) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*endpoint) ConnectEndpoint(tcpip.Endpoint) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // Shutdown closes the read and/or write end of the endpoint connection to its
 // peer.
-func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.LockUser()
 	defer e.UnlockUser()
 	return e.shutdownLocked(flags)
 }
 
-func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) *tcpip.Error {
+func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.shutdownFlags |= flags
 	switch {
 	case e.EndpointState().connected():
@@ -2368,7 +2370,7 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) *tcpip.Error {
 			// If we're fully closed and we have unread data we need to abort
 			// the connection with a RST.
 			if e.shutdownFlags&tcpip.ShutdownWrite != 0 && rcvBufUsed > 0 {
-				e.resetConnectionLocked(tcpip.ErrConnectionAborted)
+				e.resetConnectionLocked(&tcpip.ErrConnectionAborted{})
 				// Wake up worker to terminate loop.
 				e.notifyProtocolGoroutine(notifyTickleWorker)
 				return nil
@@ -2382,7 +2384,7 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) *tcpip.Error {
 				// Already closed.
 				e.sndBufMu.Unlock()
 				if e.EndpointState() == StateTimeWait {
-					return tcpip.ErrNotConnected
+					return &tcpip.ErrNotConnected{}
 				}
 				return nil
 			}
@@ -2415,22 +2417,24 @@ func (e *endpoint) shutdownLocked(flags tcpip.ShutdownFlags) *tcpip.Error {
 		}
 		return nil
 	default:
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 }
 
 // Listen puts the endpoint in "listen" mode, which allows it to accept
 // new connections.
-func (e *endpoint) Listen(backlog int) *tcpip.Error {
+func (e *endpoint) Listen(backlog int) tcpip.Error {
 	err := e.listen(backlog)
-	if err != nil && !err.IgnoreStats() {
-		e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
-		e.stats.FailedConnectionAttempts.Increment()
+	if err != nil {
+		if !err.IgnoreStats() {
+			e.stack.Stats().TCP.FailedConnectionAttempts.Increment()
+			e.stats.FailedConnectionAttempts.Increment()
+		}
 	}
 	return err
 }
 
-func (e *endpoint) listen(backlog int) *tcpip.Error {
+func (e *endpoint) listen(backlog int) tcpip.Error {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2448,7 +2452,7 @@ func (e *endpoint) listen(backlog int) *tcpip.Error {
 			// Adjust the size of the channel iff we can fix
 			// existing pending connections into the new one.
 			if len(e.acceptedChan) > backlog {
-				return tcpip.ErrInvalidEndpointState
+				return &tcpip.ErrInvalidEndpointState{}
 			}
 			if cap(e.acceptedChan) == backlog {
 				return nil
@@ -2480,7 +2484,7 @@ func (e *endpoint) listen(backlog int) *tcpip.Error {
 	// Endpoint must be bound before it can transition to listen mode.
 	if e.EndpointState() != StateBound {
 		e.stats.ReadErrors.InvalidEndpointState.Increment()
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// Register the endpoint.
@@ -2520,7 +2524,7 @@ func (e *endpoint) startAcceptedLoop() {
 // to an endpoint previously set to listen mode.
 //
 // addr if not-nil will contain the peer address of the returned endpoint.
-func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2529,7 +2533,7 @@ func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.
 	e.rcvListMu.Unlock()
 	// Endpoint must be in listen state before it can accept connections.
 	if rcvClosed || e.EndpointState() != StateListen {
-		return nil, nil, tcpip.ErrInvalidEndpointState
+		return nil, nil, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	// Get the new accepted endpoint.
@@ -2540,7 +2544,7 @@ func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.
 	case n = <-e.acceptedChan:
 		e.acceptCond.Signal()
 	default:
-		return nil, nil, tcpip.ErrWouldBlock
+		return nil, nil, &tcpip.ErrWouldBlock{}
 	}
 	if peerAddr != nil {
 		*peerAddr = n.getRemoteAddress()
@@ -2549,19 +2553,19 @@ func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.
 }
 
 // Bind binds the endpoint to a specific local port and optionally address.
-func (e *endpoint) Bind(addr tcpip.FullAddress) (err *tcpip.Error) {
+func (e *endpoint) Bind(addr tcpip.FullAddress) (err tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
 	return e.bindLocked(addr)
 }
 
-func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err *tcpip.Error) {
+func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err tcpip.Error) {
 	// Don't allow binding once endpoint is not in the initial state
 	// anymore. This is because once the endpoint goes into a connected or
 	// listen state, it is already bound.
 	if e.EndpointState() != StateInitial {
-		return tcpip.ErrAlreadyBound
+		return &tcpip.ErrAlreadyBound{}
 	}
 
 	e.BindAddr = addr.Addr
@@ -2589,7 +2593,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err *tcpip.Error) {
 	if len(addr.Addr) != 0 {
 		nic = e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr)
 		if nic == 0 {
-			return tcpip.ErrBadLocalAddress
+			return &tcpip.ErrBadLocalAddress{}
 		}
 		e.ID.LocalAddress = addr.Addr
 	}
@@ -2630,7 +2634,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) (err *tcpip.Error) {
 }
 
 // GetLocalAddress returns the address to which the endpoint is bound.
-func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2642,12 +2646,12 @@ func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
 }
 
 // GetRemoteAddress returns the address to which the endpoint is connected.
-func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
 	if !e.EndpointState().connected() {
-		return tcpip.FullAddress{}, tcpip.ErrNotConnected
+		return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 	}
 
 	return e.getRemoteAddress(), nil
@@ -2679,7 +2683,7 @@ func (e *endpoint) enqueueSegment(s *segment) bool {
 	return true
 }
 
-func (e *endpoint) onICMPError(err *tcpip.Error, errType byte, errCode byte, extra uint32, pkt *stack.PacketBuffer) {
+func (e *endpoint) onICMPError(err tcpip.Error, errType byte, errCode byte, extra uint32, pkt *stack.PacketBuffer) {
 	// Update last error first.
 	e.lastErrorMu.Lock()
 	e.lastError = err
@@ -2728,13 +2732,13 @@ func (e *endpoint) HandleControlPacket(typ stack.ControlType, extra uint32, pkt
 		e.notifyProtocolGoroutine(notifyMTUChanged)
 
 	case stack.ControlNoRoute:
-		e.onICMPError(tcpip.ErrNoRoute, byte(header.ICMPv4DstUnreachable), byte(header.ICMPv4HostUnreachable), extra, pkt)
+		e.onICMPError(&tcpip.ErrNoRoute{}, byte(header.ICMPv4DstUnreachable), byte(header.ICMPv4HostUnreachable), extra, pkt)
 
 	case stack.ControlAddressUnreachable:
-		e.onICMPError(tcpip.ErrNoRoute, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6AddressUnreachable), extra, pkt)
+		e.onICMPError(&tcpip.ErrNoRoute{}, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6AddressUnreachable), extra, pkt)
 
 	case stack.ControlNetworkUnreachable:
-		e.onICMPError(tcpip.ErrNetworkUnreachable, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6NetworkUnreachable), extra, pkt)
+		e.onICMPError(&tcpip.ErrNetworkUnreachable{}, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6NetworkUnreachable), extra, pkt)
 	}
 }
 
diff --git a/pkg/tcpip/transport/tcp/endpoint_state.go b/pkg/tcpip/transport/tcp/endpoint_state.go
index 4a01c81b4..c21dbc682 100644
--- a/pkg/tcpip/transport/tcp/endpoint_state.go
+++ b/pkg/tcpip/transport/tcp/endpoint_state.go
@@ -59,7 +59,7 @@ func (e *endpoint) beforeSave() {
 					Err: fmt.Errorf("endpoint cannot be saved in connected state: local %s:%d, remote %s:%d", e.ID.LocalAddress, e.ID.LocalPort, e.ID.RemoteAddress, e.ID.RemotePort),
 				})
 			}
-			e.resetConnectionLocked(tcpip.ErrConnectionAborted)
+			e.resetConnectionLocked(&tcpip.ErrConnectionAborted{})
 			e.mu.Unlock()
 			e.Close()
 			e.mu.Lock()
@@ -232,7 +232,8 @@ func (e *endpoint) Resume(s *stack.Stack) {
 		// Reset the scoreboard to reinitialize the sack information as
 		// we do not restore SACK information.
 		e.scoreboard.Reset()
-		if err := e.connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort}, false, e.workerRunning); err != tcpip.ErrConnectStarted {
+		err := e.connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort}, false, e.workerRunning)
+		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 			panic("endpoint connecting failed: " + err.String())
 		}
 		e.mu.Lock()
@@ -269,7 +270,8 @@ func (e *endpoint) Resume(s *stack.Stack) {
 			connectedLoading.Wait()
 			listenLoading.Wait()
 			bind()
-			if err := e.Connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort}); err != tcpip.ErrConnectStarted {
+			err := e.Connect(tcpip.FullAddress{NIC: e.boundNICID, Addr: e.connectingAddress, Port: e.ID.RemotePort})
+			if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 				panic("endpoint connecting failed: " + err.String())
 			}
 			connectingLoading.Done()
@@ -296,24 +298,6 @@ func (e *endpoint) Resume(s *stack.Stack) {
 	}
 }
 
-// saveLastError is invoked by stateify.
-func (e *endpoint) saveLastError() string {
-	if e.lastError == nil {
-		return ""
-	}
-
-	return e.lastError.String()
-}
-
-// loadLastError is invoked by stateify.
-func (e *endpoint) loadLastError(s string) {
-	if s == "" {
-		return
-	}
-
-	e.lastError = tcpip.StringToError(s)
-}
-
 // saveRecentTSTime is invoked by stateify.
 func (e *endpoint) saveRecentTSTime() unixTime {
 	return unixTime{e.recentTSTime.Unix(), e.recentTSTime.UnixNano()}
@@ -324,24 +308,6 @@ func (e *endpoint) loadRecentTSTime(unix unixTime) {
 	e.recentTSTime = time.Unix(unix.second, unix.nano)
 }
 
-// saveHardError is invoked by stateify.
-func (e *endpoint) saveHardError() string {
-	if e.hardError == nil {
-		return ""
-	}
-
-	return e.hardError.String()
-}
-
-// loadHardError is invoked by stateify.
-func (e *endpoint) loadHardError(s string) {
-	if s == "" {
-		return
-	}
-
-	e.hardError = tcpip.StringToError(s)
-}
-
 // saveMeasureTime is invoked by stateify.
 func (r *rcvBufAutoTuneParams) saveMeasureTime() unixTime {
 	return unixTime{r.measureTime.Unix(), r.measureTime.UnixNano()}
diff --git a/pkg/tcpip/transport/tcp/forwarder.go b/pkg/tcpip/transport/tcp/forwarder.go
index 596178625..2f9fe7ee0 100644
--- a/pkg/tcpip/transport/tcp/forwarder.go
+++ b/pkg/tcpip/transport/tcp/forwarder.go
@@ -143,12 +143,12 @@ func (r *ForwarderRequest) Complete(sendReset bool) {
 
 // CreateEndpoint creates a TCP endpoint for the connection request, performing
 // the 3-way handshake in the process.
-func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 
 	if r.segment == nil {
-		return nil, tcpip.ErrInvalidEndpointState
+		return nil, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	f := r.forwarder
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index 1720370c9..04012cd40 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -161,13 +161,13 @@ func (*protocol) Number() tcpip.TransportProtocolNumber {
 }
 
 // NewEndpoint creates a new tcp endpoint.
-func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newEndpoint(p.stack, netProto, waiterQueue), nil
 }
 
 // NewRawEndpoint creates a new raw TCP endpoint. Raw TCP sockets are currently
 // unsupported. It implements stack.TransportProtocol.NewRawEndpoint.
-func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return raw.NewEndpoint(p.stack, netProto, header.TCPProtocolNumber, waiterQueue)
 }
 
@@ -178,7 +178,7 @@ func (*protocol) MinimumPacketSize() int {
 
 // ParsePorts returns the source and destination ports stored in the given tcp
 // packet.
-func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
+func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err tcpip.Error) {
 	h := header.TCP(v)
 	return h.SourcePort(), h.DestinationPort(), nil
 }
@@ -216,7 +216,7 @@ func (p *protocol) HandleUnknownDestinationPacket(id stack.TransportEndpointID,
 // replyWithReset replies to the given segment with a reset segment.
 //
 // If the passed TTL is 0, then the route's default TTL will be used.
-func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) *tcpip.Error {
+func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) tcpip.Error {
 	route, err := stack.FindRoute(s.nicID, s.dstAddr, s.srcAddr, s.netProto, false /* multicastLoop */)
 	if err != nil {
 		return err
@@ -261,7 +261,7 @@ func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) *tcpip.Error
 }
 
 // SetOption implements stack.TransportProtocol.SetOption.
-func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpip.Error {
+func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.TCPSACKEnabled:
 		p.mu.Lock()
@@ -283,7 +283,7 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 
 	case *tcpip.TCPSendBufferSizeRangeOption:
 		if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		p.mu.Lock()
 		p.sendBufferSize = *v
@@ -292,7 +292,7 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 
 	case *tcpip.TCPReceiveBufferSizeRangeOption:
 		if v.Min <= 0 || v.Default < v.Min || v.Default > v.Max {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		p.mu.Lock()
 		p.recvBufferSize = *v
@@ -310,7 +310,7 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 		}
 		// linux returns ENOENT when an invalid congestion control
 		// is specified.
-		return tcpip.ErrNoSuchFile
+		return &tcpip.ErrNoSuchFile{}
 
 	case *tcpip.TCPModerateReceiveBufferOption:
 		p.mu.Lock()
@@ -340,7 +340,7 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 
 	case *tcpip.TCPTimeWaitReuseOption:
 		if *v < tcpip.TCPTimeWaitReuseDisabled || *v > tcpip.TCPTimeWaitReuseLoopbackOnly {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		p.mu.Lock()
 		p.timeWaitReuse = *v
@@ -381,7 +381,7 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 
 	case *tcpip.TCPSynRetriesOption:
 		if *v < 1 || *v > 255 {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 		p.mu.Lock()
 		p.synRetries = uint8(*v)
@@ -389,12 +389,12 @@ func (p *protocol) SetOption(option tcpip.SettableTransportProtocolOption) *tcpi
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // Option implements stack.TransportProtocol.Option.
-func (p *protocol) Option(option tcpip.GettableTransportProtocolOption) *tcpip.Error {
+func (p *protocol) Option(option tcpip.GettableTransportProtocolOption) tcpip.Error {
 	switch v := option.(type) {
 	case *tcpip.TCPSACKEnabled:
 		p.mu.RLock()
@@ -493,7 +493,7 @@ func (p *protocol) Option(option tcpip.GettableTransportProtocolOption) *tcpip.E
 		return nil
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
diff --git a/pkg/tcpip/transport/tcp/rack.go b/pkg/tcpip/transport/tcp/rack.go
index fdb7e3dc6..c0578f2d6 100644
--- a/pkg/tcpip/transport/tcp/rack.go
+++ b/pkg/tcpip/transport/tcp/rack.go
@@ -193,7 +193,7 @@ func (s *sender) schedulePTO() {
 
 // probeTimerExpired is the same as TLP_send_probe() as defined in
 // https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.5.2.
-func (s *sender) probeTimerExpired() *tcpip.Error {
+func (s *sender) probeTimerExpired() tcpip.Error {
 	if !s.rc.probeTimer.checkExpiration() {
 		return nil
 	}
diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index 405a6dce7..7a7c402c4 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -347,7 +347,7 @@ func (r *receiver) updateRTT() {
 	r.ep.rcvListMu.Unlock()
 }
 
-func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, closed bool) (drop bool, err *tcpip.Error) {
+func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, closed bool) (drop bool, err tcpip.Error) {
 	r.ep.rcvListMu.Lock()
 	rcvClosed := r.ep.rcvClosed || r.closed
 	r.ep.rcvListMu.Unlock()
@@ -395,7 +395,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 		// trigger a RST.
 		endDataSeq := s.sequenceNumber.Add(seqnum.Size(s.data.Size()))
 		if state != StateCloseWait && rcvClosed && r.rcvNxt.LessThan(endDataSeq) {
-			return true, tcpip.ErrConnectionAborted
+			return true, &tcpip.ErrConnectionAborted{}
 		}
 		if state == StateFinWait1 {
 			break
@@ -424,7 +424,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 		// the last actual data octet in a segment in
 		// which it occurs.
 		if closed && (!s.flagIsSet(header.TCPFlagFin) || s.sequenceNumber.Add(s.logicalLen()) != r.rcvNxt+1) {
-			return true, tcpip.ErrConnectionAborted
+			return true, &tcpip.ErrConnectionAborted{}
 		}
 	}
 
@@ -443,7 +443,7 @@ func (r *receiver) handleRcvdSegmentClosing(s *segment, state EndpointState, clo
 
 // handleRcvdSegment handles TCP segments directed at the connection managed by
 // r as they arrive. It is called by the protocol main loop.
-func (r *receiver) handleRcvdSegment(s *segment) (drop bool, err *tcpip.Error) {
+func (r *receiver) handleRcvdSegment(s *segment) (drop bool, err tcpip.Error) {
 	state := r.ep.EndpointState()
 	closed := r.ep.closed
 
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 027c2a4a8..2967c9f97 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -1497,7 +1497,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 }
 
 // sendSegment sends the specified segment.
-func (s *sender) sendSegment(seg *segment) *tcpip.Error {
+func (s *sender) sendSegment(seg *segment) tcpip.Error {
 	if seg.xmitCount > 0 {
 		s.ep.stack.Stats().TCP.Retransmits.Increment()
 		s.ep.stats.SendErrors.Retransmits.Increment()
@@ -1528,7 +1528,7 @@ func (s *sender) sendSegment(seg *segment) *tcpip.Error {
 
 // sendSegmentFromView sends a new segment containing the given payload, flags
 // and sequence number.
-func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags byte, seq seqnum.Value) *tcpip.Error {
+func (s *sender) sendSegmentFromView(data buffer.VectorisedView, flags byte, seq seqnum.Value) tcpip.Error {
 	s.lastSendTime = time.Now()
 	if seq == s.rttMeasureSeqNum {
 		s.rttMeasureTime = s.lastSendTime
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 87ff2b909..da2730e27 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -48,7 +48,7 @@ type endpointTester struct {
 }
 
 // CheckReadError issues a read to the endpoint and checking for an error.
-func (e *endpointTester) CheckReadError(t *testing.T, want *tcpip.Error) {
+func (e *endpointTester) CheckReadError(t *testing.T, want tcpip.Error) {
 	t.Helper()
 	res, got := e.ep.Read(ioutil.Discard, tcpip.ReadOptions{})
 	if got != want {
@@ -87,7 +87,7 @@ func (e *endpointTester) CheckReadFull(t *testing.T, count int, notifyRead <-cha
 	}
 	for w.N != 0 {
 		_, err := e.ep.Read(&w, tcpip.ReadOptions{})
-		if err == tcpip.ErrWouldBlock {
+		if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 			// Wait for receive to be notified.
 			select {
 			case <-notifyRead:
@@ -128,8 +128,11 @@ func TestGiveUpConnect(t *testing.T) {
 	wq.EventRegister(&waitEntry, waiter.EventHUp)
 	defer wq.EventUnregister(&waitEntry)
 
-	if err := ep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
-		t.Fatalf("got ep.Connect(...) = %s, want = %s", err, tcpip.ErrConnectStarted)
+	{
+		err := ep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+			t.Fatalf("got ep.Connect(...) = %v, want = %s", err, &tcpip.ErrConnectStarted{})
+		}
 	}
 
 	// Close the connection, wait for completion.
@@ -140,8 +143,11 @@ func TestGiveUpConnect(t *testing.T) {
 
 	// Call Connect again to retreive the handshake failure status
 	// and stats updates.
-	if err := ep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrAborted {
-		t.Fatalf("got ep.Connect(...) = %s, want = %s", err, tcpip.ErrAborted)
+	{
+		err := ep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrAborted); !ok {
+			t.Fatalf("got ep.Connect(...) = %v, want = %s", err, &tcpip.ErrAborted{})
+		}
 	}
 
 	if got := c.Stack().Stats().TCP.FailedConnectionAttempts.Value(); got != 1 {
@@ -194,8 +200,11 @@ func TestActiveFailedConnectionAttemptIncrement(t *testing.T) {
 	c.EP = ep
 	want := stats.TCP.FailedConnectionAttempts.Value() + 1
 
-	if err := c.EP.Connect(tcpip.FullAddress{NIC: 2, Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrNoRoute {
-		t.Errorf("got c.EP.Connect(...) = %s, want = %s", err, tcpip.ErrNoRoute)
+	{
+		err := c.EP.Connect(tcpip.FullAddress{NIC: 2, Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrNoRoute); !ok {
+			t.Errorf("got c.EP.Connect(...) = %v, want = %s", err, &tcpip.ErrNoRoute{})
+		}
 	}
 
 	if got := stats.TCP.FailedConnectionAttempts.Value(); got != want {
@@ -211,7 +220,7 @@ func TestCloseWithoutConnect(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -384,7 +393,7 @@ func TestTCPResetSentForACKWhenNotUsingSynCookies(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -925,8 +934,11 @@ func TestUserSuppliedMSSOnConnect(t *testing.T) {
 					ws := tcp.FindWndScale(seqnum.Size(rcvBufSize))
 
 					connectAddr := tcpip.FullAddress{Addr: ip.connectAddr, Port: context.TestPort}
-					if err := c.EP.Connect(connectAddr); err != tcpip.ErrConnectStarted {
-						t.Fatalf("Connect(%+v): %s", connectAddr, err)
+					{
+						err := c.EP.Connect(connectAddr)
+						if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+							t.Fatalf("Connect(%+v): %s", connectAddr, err)
+						}
 					}
 
 					// Receive SYN packet with our user supplied MSS.
@@ -1442,7 +1454,8 @@ func TestConnectBindToDevice(t *testing.T) {
 			c.WQ.EventRegister(&waitEntry, waiter.EventOut)
 			defer c.WQ.EventUnregister(&waitEntry)
 
-			if err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
+			err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+			if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 				t.Fatalf("unexpected return value from Connect: %s", err)
 			}
 
@@ -1502,8 +1515,9 @@ func TestSynSent(t *testing.T) {
 			defer c.WQ.EventUnregister(&waitEntry)
 
 			addr := tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}
-			if err := c.EP.Connect(addr); err != tcpip.ErrConnectStarted {
-				t.Fatalf("got Connect(%+v) = %s, want %s", addr, err, tcpip.ErrConnectStarted)
+			err := c.EP.Connect(addr)
+			if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+				t.Fatalf("got Connect(%+v) = %v, want %s", addr, err, &tcpip.ErrConnectStarted{})
 			}
 
 			// Receive SYN packet.
@@ -1548,9 +1562,9 @@ func TestSynSent(t *testing.T) {
 
 			ept := endpointTester{c.EP}
 			if test.reset {
-				ept.CheckReadError(t, tcpip.ErrConnectionRefused)
+				ept.CheckReadError(t, &tcpip.ErrConnectionRefused{})
 			} else {
-				ept.CheckReadError(t, tcpip.ErrAborted)
+				ept.CheckReadError(t, &tcpip.ErrAborted{})
 			}
 
 			if got := c.Stack().Stats().TCP.CurrentConnected.Value(); got != 0 {
@@ -1576,7 +1590,7 @@ func TestOutOfOrderReceive(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Send second half of data first, with seqnum 3 ahead of expected.
 	data := []byte{1, 2, 3, 4, 5, 6}
@@ -1601,7 +1615,7 @@ func TestOutOfOrderReceive(t *testing.T) {
 
 	// Wait 200ms and check that no data has been received.
 	time.Sleep(200 * time.Millisecond)
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Send the first 3 bytes now.
 	c.SendPacket(data[:3], &context.Headers{
@@ -1640,7 +1654,7 @@ func TestOutOfOrderFlood(t *testing.T) {
 	c.CreateConnected(789, 30000, rcvBufSz)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Send 100 packets before the actual one that is expected.
 	data := []byte{1, 2, 3, 4, 5, 6}
@@ -1716,7 +1730,7 @@ func TestRstOnCloseWithUnreadData(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	data := []byte{1, 2, 3}
 	c.SendPacket(data, &context.Headers{
@@ -1784,7 +1798,7 @@ func TestRstOnCloseWithUnreadDataFinConvertRst(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	data := []byte{1, 2, 3}
 	c.SendPacket(data, &context.Headers{
@@ -1866,13 +1880,13 @@ func TestShutdownRead(t *testing.T) {
 	c.CreateConnected(789, 30000, -1 /* epRcvBuf */)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	if err := c.EP.Shutdown(tcpip.ShutdownRead); err != nil {
 		t.Fatalf("Shutdown failed: %s", err)
 	}
 
-	ept.CheckReadError(t, tcpip.ErrClosedForReceive)
+	ept.CheckReadError(t, &tcpip.ErrClosedForReceive{})
 	var want uint64 = 1
 	if got := c.EP.Stats().(*tcp.Stats).ReadErrors.ReadClosed.Value(); got != want {
 		t.Fatalf("got EP stats Stats.ReadErrors.ReadClosed got %d want %d", got, want)
@@ -1891,7 +1905,7 @@ func TestFullWindowReceive(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Fill up the window w/ tcp.SegOverheadFactor*rcvBufSz as netstack multiplies
 	// the provided buffer value by tcp.SegOverheadFactor to calculate the actual
@@ -2052,7 +2066,7 @@ func TestNoWindowShrinking(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Send a 1 byte payload so that we can record the current receive window.
 	// Send a payload of half the size of rcvBufSize.
@@ -2370,7 +2384,7 @@ func TestScaledWindowAccept(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -2443,7 +2457,7 @@ func TestNonScaledWindowAccept(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -2958,7 +2972,7 @@ func TestSetTTL(t *testing.T) {
 			c := context.New(t, 65535)
 			defer c.Cleanup()
 
-			var err *tcpip.Error
+			var err tcpip.Error
 			c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &waiter.Queue{})
 			if err != nil {
 				t.Fatalf("NewEndpoint failed: %s", err)
@@ -2968,8 +2982,11 @@ func TestSetTTL(t *testing.T) {
 				t.Fatalf("SetSockOptInt(TTLOption, %d) failed: %s", wantTTL, err)
 			}
 
-			if err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
-				t.Fatalf("unexpected return value from Connect: %s", err)
+			{
+				err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+				if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+					t.Fatalf("unexpected return value from Connect: %s", err)
+				}
 			}
 
 			// Receive SYN packet.
@@ -3029,7 +3046,7 @@ func TestPassiveSendMSSLessThanMTU(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -3085,7 +3102,7 @@ func TestSynCookiePassiveSendMSSLessThanMTU(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -3110,9 +3127,9 @@ func TestForwarderSendMSSLessThanMTU(t *testing.T) {
 	defer c.Cleanup()
 
 	s := c.Stack()
-	ch := make(chan *tcpip.Error, 1)
+	ch := make(chan tcpip.Error, 1)
 	f := tcp.NewForwarder(s, 65536, 10, func(r *tcp.ForwarderRequest) {
-		var err *tcpip.Error
+		var err tcpip.Error
 		c.EP, err = r.CreateEndpoint(&c.WQ)
 		ch <- err
 	})
@@ -3141,7 +3158,7 @@ func TestSynOptionsOnActiveConnect(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -3160,8 +3177,11 @@ func TestSynOptionsOnActiveConnect(t *testing.T) {
 	c.WQ.EventRegister(&we, waiter.EventOut)
 	defer c.WQ.EventUnregister(&we)
 
-	if err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
-		t.Fatalf("got c.EP.Connect(...) = %s, want = %s", err, tcpip.ErrConnectStarted)
+	{
+		err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+			t.Fatalf("got c.EP.Connect(...) = %v, want = %s", err, &tcpip.ErrConnectStarted{})
+		}
 	}
 
 	// Receive SYN packet.
@@ -3271,22 +3291,23 @@ func TestReceiveOnResetConnection(t *testing.T) {
 
 loop:
 	for {
-		switch _, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{}); err {
-		case tcpip.ErrWouldBlock:
+		switch _, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{}); err.(type) {
+		case *tcpip.ErrWouldBlock:
 			select {
 			case <-ch:
 				// Expect the state to be StateError and subsequent Reads to fail with HardError.
-				if _, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{}); err != tcpip.ErrConnectionReset {
-					t.Fatalf("got c.EP.Read() = %s, want = %s", err, tcpip.ErrConnectionReset)
+				_, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{})
+				if _, ok := err.(*tcpip.ErrConnectionReset); !ok {
+					t.Fatalf("got c.EP.Read() = %v, want = %s", err, &tcpip.ErrConnectionReset{})
 				}
 				break loop
 			case <-time.After(1 * time.Second):
 				t.Fatalf("Timed out waiting for reset to arrive")
 			}
-		case tcpip.ErrConnectionReset:
+		case *tcpip.ErrConnectionReset:
 			break loop
 		default:
-			t.Fatalf("got c.EP.Read(nil) = %s, want = %s", err, tcpip.ErrConnectionReset)
+			t.Fatalf("got c.EP.Read(nil) = %v, want = %s", err, &tcpip.ErrConnectionReset{})
 		}
 	}
 
@@ -3325,8 +3346,9 @@ func TestSendOnResetConnection(t *testing.T) {
 	// Try to write.
 	var r bytes.Reader
 	r.Reset(make([]byte, 10))
-	if _, err := c.EP.Write(&r, tcpip.WriteOptions{}); err != tcpip.ErrConnectionReset {
-		t.Fatalf("got c.EP.Write(...) = %s, want = %s", err, tcpip.ErrConnectionReset)
+	_, err := c.EP.Write(&r, tcpip.WriteOptions{})
+	if _, ok := err.(*tcpip.ErrConnectionReset); !ok {
+		t.Fatalf("got c.EP.Write(...) = %v, want = %s", err, &tcpip.ErrConnectionReset{})
 	}
 }
 
@@ -4184,7 +4206,7 @@ func TestReadAfterClosedState(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Shutdown immediately for write, check that we get a FIN.
 	if err := c.EP.Shutdown(tcpip.ShutdownWrite); err != nil {
@@ -4263,10 +4285,13 @@ func TestReadAfterClosedState(t *testing.T) {
 
 	// Now that we drained the queue, check that functions fail with the
 	// right error code.
-	ept.CheckReadError(t, tcpip.ErrClosedForReceive)
+	ept.CheckReadError(t, &tcpip.ErrClosedForReceive{})
 	var buf bytes.Buffer
-	if _, err := c.EP.Read(&buf, tcpip.ReadOptions{Peek: true}); err != tcpip.ErrClosedForReceive {
-		t.Fatalf("c.EP.Read(_, {Peek: true}) = %v, %s; want _, %s", res, err, tcpip.ErrClosedForReceive)
+	{
+		_, err := c.EP.Read(&buf, tcpip.ReadOptions{Peek: true})
+		if _, ok := err.(*tcpip.ErrClosedForReceive); !ok {
+			t.Fatalf("c.EP.Read(_, {Peek: true}) = %v, %s; want _, %s", res, err, &tcpip.ErrClosedForReceive{})
+		}
 	}
 }
 
@@ -4277,7 +4302,7 @@ func TestReusePort(t *testing.T) {
 	defer c.Cleanup()
 
 	// First case, just an endpoint that was bound.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &waiter.Queue{})
 	if err != nil {
 		t.Fatalf("NewEndpoint failed; %s", err)
@@ -4307,8 +4332,11 @@ func TestReusePort(t *testing.T) {
 	if err := c.EP.Bind(tcpip.FullAddress{Port: context.StackPort}); err != nil {
 		t.Fatalf("Bind failed: %s", err)
 	}
-	if err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
-		t.Fatalf("got c.EP.Connect(...) = %s, want = %s", err, tcpip.ErrConnectStarted)
+	{
+		err := c.EP.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+			t.Fatalf("got c.EP.Connect(...) = %v, want = %s", err, &tcpip.ErrConnectStarted{})
+		}
 	}
 	c.EP.Close()
 
@@ -4515,11 +4543,11 @@ func TestBindToDeviceOption(t *testing.T) {
 	testActions := []struct {
 		name                 string
 		setBindToDevice      *tcpip.NICID
-		setBindToDeviceError *tcpip.Error
+		setBindToDeviceError tcpip.Error
 		getBindToDevice      int32
 	}{
 		{"GetDefaultValue", nil, nil, 0},
-		{"BindToNonExistent", nicIDPtr(999), tcpip.ErrUnknownDevice, 0},
+		{"BindToNonExistent", nicIDPtr(999), &tcpip.ErrUnknownDevice{}, 0},
 		{"BindToExistent", nicIDPtr(321), nil, 321},
 		{"UnbindToDevice", nicIDPtr(0), nil, 0},
 	}
@@ -4539,7 +4567,7 @@ func TestBindToDeviceOption(t *testing.T) {
 	}
 }
 
-func makeStack() (*stack.Stack, *tcpip.Error) {
+func makeStack() (*stack.Stack, tcpip.Error) {
 	s := stack.New(stack.Options{
 		NetworkProtocols: []stack.NetworkProtocolFactory{
 			ipv4.NewProtocol,
@@ -4609,8 +4637,11 @@ func TestSelfConnect(t *testing.T) {
 	wq.EventRegister(&waitEntry, waiter.EventOut)
 	defer wq.EventUnregister(&waitEntry)
 
-	if err := ep.Connect(tcpip.FullAddress{Addr: context.StackAddr, Port: context.StackPort}); err != tcpip.ErrConnectStarted {
-		t.Fatalf("got ep.Connect(...) = %s, want = %s", err, tcpip.ErrConnectStarted)
+	{
+		err := ep.Connect(tcpip.FullAddress{Addr: context.StackAddr, Port: context.StackPort})
+		if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
+			t.Fatalf("got ep.Connect(...) = %v, want = %s", err, &tcpip.ErrConnectStarted{})
+		}
 	}
 
 	<-notifyCh
@@ -4762,9 +4793,9 @@ func TestConnectAvoidsBoundPorts(t *testing.T) {
 													t.Fatalf("Bind(%d) failed: %s", i, err)
 												}
 											}
-											want := tcpip.ErrConnectStarted
+											var want tcpip.Error = &tcpip.ErrConnectStarted{}
 											if collides {
-												want = tcpip.ErrNoPortAvailable
+												want = &tcpip.ErrNoPortAvailable{}
 											}
 											if err := makeEP(candidateNetwork).Connect(tcpip.FullAddress{Addr: address(t, candidateAddressType, false), Port: 31337}); err != want {
 												t.Fatalf("got ep.Connect(..) = %s, want = %s", err, want)
@@ -4889,11 +4920,11 @@ func TestTCPEndpointProbe(t *testing.T) {
 func TestStackSetCongestionControl(t *testing.T) {
 	testCases := []struct {
 		cc  tcpip.CongestionControlOption
-		err *tcpip.Error
+		err tcpip.Error
 	}{
 		{"reno", nil},
 		{"cubic", nil},
-		{"blahblah", tcpip.ErrNoSuchFile},
+		{"blahblah", &tcpip.ErrNoSuchFile{}},
 	}
 
 	for _, tc := range testCases {
@@ -4975,11 +5006,11 @@ func TestStackSetAvailableCongestionControl(t *testing.T) {
 func TestEndpointSetCongestionControl(t *testing.T) {
 	testCases := []struct {
 		cc  tcpip.CongestionControlOption
-		err *tcpip.Error
+		err tcpip.Error
 	}{
 		{"reno", nil},
 		{"cubic", nil},
-		{"blahblah", tcpip.ErrNoSuchFile},
+		{"blahblah", &tcpip.ErrNoSuchFile{}},
 	}
 
 	for _, connected := range []bool{false, true} {
@@ -4989,7 +5020,7 @@ func TestEndpointSetCongestionControl(t *testing.T) {
 				defer c.Cleanup()
 
 				// Create TCP endpoint.
-				var err *tcpip.Error
+				var err tcpip.Error
 				c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 				if err != nil {
 					t.Fatalf("NewEndpoint failed: %s", err)
@@ -5085,7 +5116,7 @@ func TestKeepalive(t *testing.T) {
 
 	// Check that the connection is still alive.
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Send some data and wait before ACKing it. Keepalives should be disabled
 	// during this period.
@@ -5176,7 +5207,7 @@ func TestKeepalive(t *testing.T) {
 		t.Errorf("got c.Stack().Stats().TCP.EstablishedTimedout.Value() = %d, want = 1", got)
 	}
 
-	ept.CheckReadError(t, tcpip.ErrTimeout)
+	ept.CheckReadError(t, &tcpip.ErrTimeout{})
 
 	if got := c.Stack().Stats().TCP.CurrentEstablished.Value(); got != 0 {
 		t.Errorf("got stats.TCP.CurrentEstablished.Value() = %d, want = 0", got)
@@ -5283,7 +5314,7 @@ func TestListenBacklogFull(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -5326,7 +5357,7 @@ func TestListenBacklogFull(t *testing.T) {
 
 	for i := 0; i < listenBacklog; i++ {
 		_, _, err = c.EP.Accept(nil)
-		if err == tcpip.ErrWouldBlock {
+		if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 			// Wait for connection to be established.
 			select {
 			case <-ch:
@@ -5343,7 +5374,7 @@ func TestListenBacklogFull(t *testing.T) {
 
 	// Now verify that there are no more connections that can be accepted.
 	_, _, err = c.EP.Accept(nil)
-	if err != tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		select {
 		case <-ch:
 			t.Fatalf("unexpected endpoint delivered on Accept: %+v", c.EP)
@@ -5355,7 +5386,7 @@ func TestListenBacklogFull(t *testing.T) {
 	executeHandshake(t, c, context.TestPort+lastPortOffset, false /*synCookieInUse */)
 
 	newEP, _, err := c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -5598,7 +5629,7 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -5673,7 +5704,7 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	newEP, _, err := c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -5709,7 +5740,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 	}
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -5750,7 +5781,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	_, _, err = c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -5766,7 +5797,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 
 	// Now verify that there are no more connections that can be accepted.
 	_, _, err = c.EP.Accept(nil)
-	if err != tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
 		select {
 		case <-ch:
 			t.Fatalf("unexpected endpoint delivered on Accept: %+v", c.EP)
@@ -5780,7 +5811,7 @@ func TestSYNRetransmit(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -5824,7 +5855,7 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 	defer c.Cleanup()
 
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.Stack().NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %s", err)
@@ -5899,12 +5930,13 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 	})
 
 	newEP, _, err := c.EP.Accept(nil)
-
-	if err != nil && err != tcpip.ErrWouldBlock {
+	switch err.(type) {
+	case nil, *tcpip.ErrWouldBlock:
+	default:
 		t.Fatalf("Accept failed: %s", err)
 	}
 
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Try to accept the connections in the backlog.
 		we, ch := waiter.NewChannelEntry(nil)
 		c.WQ.EventRegister(&we, waiter.EventIn)
@@ -5972,7 +6004,7 @@ func TestPassiveConnectionAttemptIncrement(t *testing.T) {
 
 	// Verify that there is only one acceptable connection at this point.
 	_, _, err = c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6042,7 +6074,7 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
 
 	// Now check that there is one acceptable connections.
 	_, _, err = c.EP.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6074,7 +6106,7 @@ func TestEndpointBindListenAcceptState(t *testing.T) {
 	}
 
 	ept := endpointTester{ep}
-	ept.CheckReadError(t, tcpip.ErrNotConnected)
+	ept.CheckReadError(t, &tcpip.ErrNotConnected{})
 	if got := ep.Stats().(*tcp.Stats).ReadErrors.NotConnected.Value(); got != 1 {
 		t.Errorf("got EP stats Stats.ReadErrors.NotConnected got %d want %d", got, 1)
 	}
@@ -6094,7 +6126,7 @@ func TestEndpointBindListenAcceptState(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	aep, _, err := ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6110,8 +6142,11 @@ func TestEndpointBindListenAcceptState(t *testing.T) {
 	if got, want := tcp.EndpointState(aep.State()), tcp.StateEstablished; got != want {
 		t.Errorf("unexpected endpoint state: want %s, got %s", want, got)
 	}
-	if err := aep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrAlreadyConnected {
-		t.Errorf("unexpected error attempting to call connect on an established endpoint, got: %s, want: %s", err, tcpip.ErrAlreadyConnected)
+	{
+		err := aep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort})
+		if _, ok := err.(*tcpip.ErrAlreadyConnected); !ok {
+			t.Errorf("unexpected error attempting to call connect on an established endpoint, got: %v, want: %s", err, &tcpip.ErrAlreadyConnected{})
+		}
 	}
 	// Listening endpoint remains in listen state.
 	if got, want := tcp.EndpointState(ep.State()), tcp.StateListen; got != want {
@@ -6230,7 +6265,7 @@ func TestReceiveBufferAutoTuningApplicationLimited(t *testing.T) {
 	// window increases to the full available buffer size.
 	for {
 		_, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{})
-		if err == tcpip.ErrWouldBlock {
+		if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 			break
 		}
 	}
@@ -6354,7 +6389,7 @@ func TestReceiveBufferAutoTuning(t *testing.T) {
 		totalCopied := 0
 		for {
 			res, err := c.EP.Read(ioutil.Discard, tcpip.ReadOptions{})
-			if err == tcpip.ErrWouldBlock {
+			if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 				break
 			}
 			totalCopied += res.Count
@@ -6546,7 +6581,7 @@ func TestTCPTimeWaitRSTIgnored(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6665,7 +6700,7 @@ func TestTCPTimeWaitOutOfOrder(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6772,7 +6807,7 @@ func TestTCPTimeWaitNewSyn(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6862,7 +6897,7 @@ func TestTCPTimeWaitNewSyn(t *testing.T) {
 
 	// Try to accept the connection.
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -6936,7 +6971,7 @@ func TestTCPTimeWaitDuplicateFINExtendsTimeWait(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -7086,7 +7121,7 @@ func TestTCPCloseWithData(t *testing.T) {
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
@@ -7277,7 +7312,7 @@ func TestTCPUserTimeout(t *testing.T) {
 	)
 
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrTimeout)
+	ept.CheckReadError(t, &tcpip.ErrTimeout{})
 
 	if got, want := c.Stack().Stats().TCP.EstablishedTimedout.Value(), origEstablishedTimedout+1; got != want {
 		t.Errorf("got c.Stack().Stats().TCP.EstablishedTimedout = %d, want = %d", got, want)
@@ -7321,7 +7356,7 @@ func TestKeepaliveWithUserTimeout(t *testing.T) {
 
 	// Check that the connection is still alive.
 	ept := endpointTester{c.EP}
-	ept.CheckReadError(t, tcpip.ErrWouldBlock)
+	ept.CheckReadError(t, &tcpip.ErrWouldBlock{})
 
 	// Now receive 1 keepalives, but don't ACK it.
 	b := c.GetPacket()
@@ -7360,7 +7395,7 @@ func TestKeepaliveWithUserTimeout(t *testing.T) {
 		),
 	)
 
-	ept.CheckReadError(t, tcpip.ErrTimeout)
+	ept.CheckReadError(t, &tcpip.ErrTimeout{})
 	if got, want := c.Stack().Stats().TCP.EstablishedTimedout.Value(), origEstablishedTimedout+1; got != want {
 		t.Errorf("got c.Stack().Stats().TCP.EstablishedTimedout = %d, want = %d", got, want)
 	}
@@ -7515,8 +7550,9 @@ func TestTCPDeferAccept(t *testing.T) {
 
 	irs, iss := executeHandshake(t, c, context.TestPort, false /* synCookiesInUse */)
 
-	if _, _, err := c.EP.Accept(nil); err != tcpip.ErrWouldBlock {
-		t.Fatalf("got c.EP.Accept(nil) = %s, want: %s", err, tcpip.ErrWouldBlock)
+	_, _, err := c.EP.Accept(nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got c.EP.Accept(nil) = %v, want: %s", err, &tcpip.ErrWouldBlock{})
 	}
 
 	// Send data. This should result in an acceptable endpoint.
@@ -7573,8 +7609,9 @@ func TestTCPDeferAcceptTimeout(t *testing.T) {
 
 	irs, iss := executeHandshake(t, c, context.TestPort, false /* synCookiesInUse */)
 
-	if _, _, err := c.EP.Accept(nil); err != tcpip.ErrWouldBlock {
-		t.Fatalf("got c.EP.Accept(nil) = %s, want: %s", err, tcpip.ErrWouldBlock)
+	_, _, err := c.EP.Accept(nil)
+	if _, ok := err.(*tcpip.ErrWouldBlock); !ok {
+		t.Fatalf("got c.EP.Accept(nil) = %v, want: %s", err, &tcpip.ErrWouldBlock{})
 	}
 
 	// Sleep for a little of the tcpDeferAccept timeout.
@@ -7696,13 +7733,13 @@ func TestSetStackTimeWaitReuse(t *testing.T) {
 	s := c.Stack()
 	testCases := []struct {
 		v   int
-		err *tcpip.Error
+		err tcpip.Error
 	}{
 		{int(tcpip.TCPTimeWaitReuseDisabled), nil},
 		{int(tcpip.TCPTimeWaitReuseGlobal), nil},
 		{int(tcpip.TCPTimeWaitReuseLoopbackOnly), nil},
-		{int(tcpip.TCPTimeWaitReuseLoopbackOnly) + 1, tcpip.ErrInvalidOptionValue},
-		{int(tcpip.TCPTimeWaitReuseDisabled) - 1, tcpip.ErrInvalidOptionValue},
+		{int(tcpip.TCPTimeWaitReuseLoopbackOnly) + 1, &tcpip.ErrInvalidOptionValue{}},
+		{int(tcpip.TCPTimeWaitReuseDisabled) - 1, &tcpip.ErrInvalidOptionValue{}},
 	}
 
 	for _, tc := range testCases {
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index ee55f030c..b1cb9a324 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -586,7 +586,7 @@ func (c *Context) ReceiveNonBlockingAndCheckPacket(data []byte, offset, size int
 // is true then it sets the IP_V6ONLY option on the socket to make it a IPv6
 // only endpoint instead of a default dual stack socket.
 func (c *Context) CreateV6Endpoint(v6only bool) {
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.s.NewEndpoint(tcp.ProtocolNumber, ipv6.ProtocolNumber, &c.WQ)
 	if err != nil {
 		c.t.Fatalf("NewEndpoint failed: %v", err)
@@ -689,7 +689,8 @@ func (c *Context) Connect(iss seqnum.Value, rcvWnd seqnum.Size, options []byte)
 	c.WQ.EventRegister(&waitEntry, waiter.EventOut)
 	defer c.WQ.EventUnregister(&waitEntry)
 
-	if err := c.EP.Connect(tcpip.FullAddress{Addr: TestAddr, Port: TestPort}); err != tcpip.ErrConnectStarted {
+	err := c.EP.Connect(tcpip.FullAddress{Addr: TestAddr, Port: TestPort})
+	if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 		c.t.Fatalf("Unexpected return value from Connect: %v", err)
 	}
 
@@ -749,7 +750,7 @@ func (c *Context) Connect(iss seqnum.Value, rcvWnd seqnum.Size, options []byte)
 // Create creates a TCP endpoint.
 func (c *Context) Create(epRcvBuf int) {
 	// Create TCP endpoint.
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.s.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		c.t.Fatalf("NewEndpoint failed: %v", err)
@@ -887,7 +888,7 @@ func (r *RawEndpoint) VerifyACKHasSACK(sackBlocks []header.SACKBlock) {
 // It also verifies where required(eg.Timestamp) that the ACK to the SYN-ACK
 // does not carry an option that was not requested.
 func (c *Context) CreateConnectedWithOptions(wantOptions header.TCPSynOptions) *RawEndpoint {
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.EP, err = c.s.NewEndpoint(tcp.ProtocolNumber, ipv4.ProtocolNumber, &c.WQ)
 	if err != nil {
 		c.t.Fatalf("c.s.NewEndpoint(tcp, ipv4...) = %v", err)
@@ -903,7 +904,7 @@ func (c *Context) CreateConnectedWithOptions(wantOptions header.TCPSynOptions) *
 
 	testFullAddr := tcpip.FullAddress{Addr: TestAddr, Port: TestPort}
 	err = c.EP.Connect(testFullAddr)
-	if err != tcpip.ErrConnectStarted {
+	if _, ok := err.(*tcpip.ErrConnectStarted); !ok {
 		c.t.Fatalf("c.ep.Connect(%v) = %v", testFullAddr, err)
 	}
 	// Receive SYN packet.
@@ -1054,7 +1055,7 @@ func (c *Context) AcceptWithOptions(wndScale int, synOptions header.TCPSynOption
 	defer wq.EventUnregister(&we)
 
 	c.EP, _, err = ep.Accept(nil)
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index d2f7b6e85..31a5ddce9 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -109,8 +109,8 @@ type endpoint struct {
 	multicastNICID tcpip.NICID
 	portFlags      ports.Flags
 
-	lastErrorMu sync.Mutex   `state:"nosave"`
-	lastError   *tcpip.Error `state:".(string)"`
+	lastErrorMu sync.Mutex `state:"nosave"`
+	lastError   tcpip.Error
 
 	// Values used to reserve a port or register a transport endpoint.
 	// (which ever happens first).
@@ -215,7 +215,7 @@ func (e *endpoint) UniqueID() uint64 {
 	return e.uniqueID
 }
 
-func (e *endpoint) LastError() *tcpip.Error {
+func (e *endpoint) LastError() tcpip.Error {
 	e.lastErrorMu.Lock()
 	defer e.lastErrorMu.Unlock()
 
@@ -225,7 +225,7 @@ func (e *endpoint) LastError() *tcpip.Error {
 }
 
 // UpdateLastError implements tcpip.SocketOptionsHandler.UpdateLastError.
-func (e *endpoint) UpdateLastError(err *tcpip.Error) {
+func (e *endpoint) UpdateLastError(err tcpip.Error) {
 	e.lastErrorMu.Lock()
 	e.lastError = err
 	e.lastErrorMu.Unlock()
@@ -282,7 +282,7 @@ func (e *endpoint) Close() {
 func (e *endpoint) ModerateRecvBuf(copied int) {}
 
 // Read implements tcpip.Endpoint.Read.
-func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, *tcpip.Error) {
+func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult, tcpip.Error) {
 	if err := e.LastError(); err != nil {
 		return tcpip.ReadResult{}, err
 	}
@@ -290,10 +290,10 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 	e.rcvMu.Lock()
 
 	if e.rcvList.Empty() {
-		err := tcpip.ErrWouldBlock
+		var err tcpip.Error = &tcpip.ErrWouldBlock{}
 		if e.rcvClosed {
 			e.stats.ReadErrors.ReadClosed.Increment()
-			err = tcpip.ErrClosedForReceive
+			err = &tcpip.ErrClosedForReceive{}
 		}
 		e.rcvMu.Unlock()
 		return tcpip.ReadResult{}, err
@@ -340,7 +340,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 
 	n, err := p.data.ReadTo(dst, opts.Peek)
 	if n == 0 && err != nil {
-		return res, tcpip.ErrBadBuffer
+		return res, &tcpip.ErrBadBuffer{}
 	}
 	res.Count = n
 	return res, nil
@@ -351,7 +351,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 // reacquire the mutex in exclusive mode.
 //
 // Returns true for retry if preparation should be retried.
-func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpip.Error) {
+func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err tcpip.Error) {
 	switch e.EndpointState() {
 	case StateInitial:
 	case StateConnected:
@@ -359,11 +359,11 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpi
 
 	case StateBound:
 		if to == nil {
-			return false, tcpip.ErrDestinationRequired
+			return false, &tcpip.ErrDestinationRequired{}
 		}
 		return false, nil
 	default:
-		return false, tcpip.ErrInvalidEndpointState
+		return false, &tcpip.ErrInvalidEndpointState{}
 	}
 
 	e.mu.RUnlock()
@@ -389,7 +389,7 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err *tcpi
 // connectRoute establishes a route to the specified interface or the
 // configured multicast interface if no interface is specified and the
 // specified address is a multicast address.
-func (e *endpoint) connectRoute(nicID tcpip.NICID, addr tcpip.FullAddress, netProto tcpip.NetworkProtocolNumber) (*stack.Route, tcpip.NICID, *tcpip.Error) {
+func (e *endpoint) connectRoute(nicID tcpip.NICID, addr tcpip.FullAddress, netProto tcpip.NetworkProtocolNumber) (*stack.Route, tcpip.NICID, tcpip.Error) {
 	localAddr := e.ID.LocalAddress
 	if e.isBroadcastOrMulticast(nicID, netProto, localAddr) {
 		// A packet can only originate from a unicast address (i.e., an interface).
@@ -415,18 +415,18 @@ func (e *endpoint) connectRoute(nicID tcpip.NICID, addr tcpip.FullAddress, netPr
 
 // Write writes data to the endpoint's peer. This method does not block
 // if the data cannot be written.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	n, err := e.write(p, opts)
-	switch err {
+	switch err.(type) {
 	case nil:
 		e.stats.PacketsSent.Increment()
-	case tcpip.ErrMessageTooLong, tcpip.ErrInvalidOptionValue:
+	case *tcpip.ErrMessageTooLong, *tcpip.ErrInvalidOptionValue:
 		e.stats.WriteErrors.InvalidArgs.Increment()
-	case tcpip.ErrClosedForSend:
+	case *tcpip.ErrClosedForSend:
 		e.stats.WriteErrors.WriteClosed.Increment()
-	case tcpip.ErrInvalidEndpointState:
+	case *tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
+	case *tcpip.ErrNoRoute, *tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
 	default:
@@ -436,14 +436,14 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
 	if err := e.LastError(); err != nil {
 		return 0, err
 	}
 
 	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
 	if opts.More {
-		return 0, tcpip.ErrInvalidOptionValue
+		return 0, &tcpip.ErrInvalidOptionValue{}
 	}
 
 	to := opts.To
@@ -459,7 +459,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 
 	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
 	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-		return 0, tcpip.ErrClosedForSend
+		return 0, &tcpip.ErrClosedForSend{}
 	}
 
 	// Prepare for write.
@@ -485,7 +485,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 		}
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
-				return 0, tcpip.ErrNoRoute
+				return 0, &tcpip.ErrNoRoute{}
 			}
 
 			nicID = e.BindNICID
@@ -493,7 +493,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 
 		if to.Port == 0 {
 			// Port 0 is an invalid port to send to.
-			return 0, tcpip.ErrInvalidEndpointState
+			return 0, &tcpip.ErrInvalidEndpointState{}
 		}
 
 		dst, netProto, err := e.checkV4MappedLocked(*to)
@@ -512,19 +512,19 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 	}
 
 	if !e.ops.GetBroadcast() && route.IsOutboundBroadcast() {
-		return 0, tcpip.ErrBroadcastDisabled
+		return 0, &tcpip.ErrBroadcastDisabled{}
 	}
 
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
-		return 0, tcpip.ErrBadBuffer
+		return 0, &tcpip.ErrBadBuffer{}
 	}
 	if len(v) > header.UDPMaximumPacketSize {
 		// Payload can't possibly fit in a packet.
 		so := e.SocketOptions()
 		if so.GetRecvError() {
 			so.QueueLocalErr(
-				tcpip.ErrMessageTooLong,
+				&tcpip.ErrMessageTooLong{},
 				route.NetProto,
 				header.UDPMaximumPacketSize,
 				tcpip.FullAddress{
@@ -535,7 +535,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tc
 				v,
 			)
 		}
-		return 0, tcpip.ErrMessageTooLong
+		return 0, &tcpip.ErrMessageTooLong{}
 	}
 
 	ttl := e.ttl
@@ -585,13 +585,13 @@ func (e *endpoint) OnReusePortSet(v bool) {
 }
 
 // SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
-func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) *tcpip.Error {
+func (e *endpoint) SetSockOptInt(opt tcpip.SockOptInt, v int) tcpip.Error {
 	switch opt {
 	case tcpip.MTUDiscoverOption:
 		// Return not supported if the value is not disabling path
 		// MTU discovery.
 		if v != tcpip.PMTUDiscoveryDont {
-			return tcpip.ErrNotSupported
+			return &tcpip.ErrNotSupported{}
 		}
 
 	case tcpip.MulticastTTLOption:
@@ -643,7 +643,7 @@ func (e *endpoint) HasNIC(id int32) bool {
 }
 
 // SetSockOpt implements tcpip.Endpoint.SetSockOpt.
-func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
+func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) tcpip.Error {
 	switch v := opt.(type) {
 	case *tcpip.MulticastInterfaceOption:
 		e.mu.Lock()
@@ -665,17 +665,17 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 
 		if nic != 0 {
 			if !e.stack.CheckNIC(nic) {
-				return tcpip.ErrBadLocalAddress
+				return &tcpip.ErrBadLocalAddress{}
 			}
 		} else {
 			nic = e.stack.CheckLocalAddress(0, netProto, addr)
 			if nic == 0 {
-				return tcpip.ErrBadLocalAddress
+				return &tcpip.ErrBadLocalAddress{}
 			}
 		}
 
 		if e.BindNICID != 0 && e.BindNICID != nic {
-			return tcpip.ErrInvalidEndpointState
+			return &tcpip.ErrInvalidEndpointState{}
 		}
 
 		e.multicastNICID = nic
@@ -683,7 +683,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 
 	case *tcpip.AddMembershipOption:
 		if !header.IsV4MulticastAddress(v.MulticastAddr) && !header.IsV6MulticastAddress(v.MulticastAddr) {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		nicID := v.NIC
@@ -699,7 +699,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 			nicID = e.stack.CheckLocalAddress(nicID, e.NetProto, v.InterfaceAddr)
 		}
 		if nicID == 0 {
-			return tcpip.ErrUnknownDevice
+			return &tcpip.ErrUnknownDevice{}
 		}
 
 		memToInsert := multicastMembership{nicID: nicID, multicastAddr: v.MulticastAddr}
@@ -708,7 +708,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 		defer e.mu.Unlock()
 
 		if _, ok := e.multicastMemberships[memToInsert]; ok {
-			return tcpip.ErrPortInUse
+			return &tcpip.ErrPortInUse{}
 		}
 
 		if err := e.stack.JoinGroup(e.NetProto, nicID, v.MulticastAddr); err != nil {
@@ -719,7 +719,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 
 	case *tcpip.RemoveMembershipOption:
 		if !header.IsV4MulticastAddress(v.MulticastAddr) && !header.IsV6MulticastAddress(v.MulticastAddr) {
-			return tcpip.ErrInvalidOptionValue
+			return &tcpip.ErrInvalidOptionValue{}
 		}
 
 		nicID := v.NIC
@@ -734,7 +734,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 			nicID = e.stack.CheckLocalAddress(nicID, e.NetProto, v.InterfaceAddr)
 		}
 		if nicID == 0 {
-			return tcpip.ErrUnknownDevice
+			return &tcpip.ErrUnknownDevice{}
 		}
 
 		memToRemove := multicastMembership{nicID: nicID, multicastAddr: v.MulticastAddr}
@@ -743,7 +743,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 		defer e.mu.Unlock()
 
 		if _, ok := e.multicastMemberships[memToRemove]; !ok {
-			return tcpip.ErrBadLocalAddress
+			return &tcpip.ErrBadLocalAddress{}
 		}
 
 		if err := e.stack.LeaveGroup(e.NetProto, nicID, v.MulticastAddr); err != nil {
@@ -759,7 +759,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
-func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, tcpip.Error) {
 	switch opt {
 	case tcpip.IPv4TOSOption:
 		e.mu.RLock()
@@ -806,12 +806,12 @@ func (e *endpoint) GetSockOptInt(opt tcpip.SockOptInt) (int, *tcpip.Error) {
 		return v, nil
 
 	default:
-		return -1, tcpip.ErrUnknownProtocolOption
+		return -1, &tcpip.ErrUnknownProtocolOption{}
 	}
 }
 
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
+func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
 	switch o := opt.(type) {
 	case *tcpip.MulticastInterfaceOption:
 		e.mu.Lock()
@@ -822,14 +822,14 @@ func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) *tcpip.Error {
 		e.mu.Unlock()
 
 	default:
-		return tcpip.ErrUnknownProtocolOption
+		return &tcpip.ErrUnknownProtocolOption{}
 	}
 	return nil
 }
 
 // sendUDP sends a UDP segment via the provided network endpoint and under the
 // provided identity.
-func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort uint16, ttl uint8, useDefaultTTL bool, tos uint8, owner tcpip.PacketOwner, noChecksum bool) *tcpip.Error {
+func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort uint16, ttl uint8, useDefaultTTL bool, tos uint8, owner tcpip.PacketOwner, noChecksum bool) tcpip.Error {
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: header.UDPMinimumSize + int(r.MaxHeaderLength()),
 		Data:               data,
@@ -879,7 +879,7 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 
 // checkV4MappedLocked determines the effective network protocol and converts
 // addr to its canonical form.
-func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, tcpip.Error) {
 	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProtoLocked(addr, e.ops.GetV6Only())
 	if err != nil {
 		return tcpip.FullAddress{}, 0, err
@@ -888,7 +888,7 @@ func (e *endpoint) checkV4MappedLocked(addr tcpip.FullAddress) (tcpip.FullAddres
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
-func (e *endpoint) Disconnect() *tcpip.Error {
+func (e *endpoint) Disconnect() tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
@@ -906,7 +906,7 @@ func (e *endpoint) Disconnect() *tcpip.Error {
 
 	// Exclude ephemerally bound endpoints.
 	if e.BindNICID != 0 || e.ID.LocalAddress == "" {
-		var err *tcpip.Error
+		var err tcpip.Error
 		id = stack.TransportEndpointID{
 			LocalPort:    e.ID.LocalPort,
 			LocalAddress: e.ID.LocalAddress,
@@ -937,10 +937,10 @@ func (e *endpoint) Disconnect() *tcpip.Error {
 }
 
 // Connect connects the endpoint to its peer. Specifying a NIC is optional.
-func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Connect(addr tcpip.FullAddress) tcpip.Error {
 	if addr.Port == 0 {
 		// We don't support connecting to port zero.
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	e.mu.Lock()
@@ -957,12 +957,12 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 		}
 
 		if nicID != 0 && nicID != e.BindNICID {
-			return tcpip.ErrInvalidEndpointState
+			return &tcpip.ErrInvalidEndpointState{}
 		}
 
 		nicID = e.BindNICID
 	default:
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	addr, netProto, err := e.checkV4MappedLocked(addr)
@@ -1032,20 +1032,20 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // ConnectEndpoint is not supported.
-func (*endpoint) ConnectEndpoint(tcpip.Endpoint) *tcpip.Error {
-	return tcpip.ErrInvalidEndpointState
+func (*endpoint) ConnectEndpoint(tcpip.Endpoint) tcpip.Error {
+	return &tcpip.ErrInvalidEndpointState{}
 }
 
 // Shutdown closes the read and/or write end of the endpoint connection
 // to its peer.
-func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
 	// A socket in the bound state can still receive multicast messages,
 	// so we need to notify waiters on shutdown.
 	if state := e.EndpointState(); state != StateBound && state != StateConnected {
-		return tcpip.ErrNotConnected
+		return &tcpip.ErrNotConnected{}
 	}
 
 	e.shutdownFlags |= flags
@@ -1065,16 +1065,16 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
 }
 
 // Listen is not supported by UDP, it just fails.
-func (*endpoint) Listen(int) *tcpip.Error {
-	return tcpip.ErrNotSupported
+func (*endpoint) Listen(int) tcpip.Error {
+	return &tcpip.ErrNotSupported{}
 }
 
 // Accept is not supported by UDP, it just fails.
-func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
-	return nil, nil, tcpip.ErrNotSupported
+func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpip.Error) {
+	return nil, nil, &tcpip.ErrNotSupported{}
 }
 
-func (e *endpoint) registerWithStack(netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, tcpip.NICID, *tcpip.Error) {
+func (e *endpoint) registerWithStack(netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, tcpip.NICID, tcpip.Error) {
 	bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
 	if e.ID.LocalPort == 0 {
 		port, err := e.stack.ReservePort(netProtos, ProtocolNumber, id.LocalAddress, id.LocalPort, e.portFlags, bindToDevice, tcpip.FullAddress{}, nil /* testPort */)
@@ -1093,11 +1093,11 @@ func (e *endpoint) registerWithStack(netProtos []tcpip.NetworkProtocolNumber, id
 	return id, bindToDevice, err
 }
 
-func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) bindLocked(addr tcpip.FullAddress) tcpip.Error {
 	// Don't allow binding once endpoint is not in the initial state
 	// anymore.
 	if e.EndpointState() != StateInitial {
-		return tcpip.ErrInvalidEndpointState
+		return &tcpip.ErrInvalidEndpointState{}
 	}
 
 	addr, netProto, err := e.checkV4MappedLocked(addr)
@@ -1121,7 +1121,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 		// A local unicast address was specified, verify that it's valid.
 		nicID = e.stack.CheckLocalAddress(addr.NIC, netProto, addr.Addr)
 		if nicID == 0 {
-			return tcpip.ErrBadLocalAddress
+			return &tcpip.ErrBadLocalAddress{}
 		}
 	}
 
@@ -1151,7 +1151,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 
 // Bind binds the endpoint to a specific local address and port.
 // Specifying a NIC is optional.
-func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+func (e *endpoint) Bind(addr tcpip.FullAddress) tcpip.Error {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 
@@ -1167,7 +1167,7 @@ func (e *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
 }
 
 // GetLocalAddress returns the address to which the endpoint is bound.
-func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
@@ -1184,12 +1184,12 @@ func (e *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
 }
 
 // GetRemoteAddress returns the address to which the endpoint is connected.
-func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, tcpip.Error) {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
 	if e.EndpointState() != StateConnected {
-		return tcpip.FullAddress{}, tcpip.ErrNotConnected
+		return tcpip.FullAddress{}, &tcpip.ErrNotConnected{}
 	}
 
 	return tcpip.FullAddress{
@@ -1322,7 +1322,7 @@ func (e *endpoint) HandlePacket(id stack.TransportEndpointID, pkt *stack.PacketB
 	}
 }
 
-func (e *endpoint) onICMPError(err *tcpip.Error, errType byte, errCode byte, extra uint32, pkt *stack.PacketBuffer) {
+func (e *endpoint) onICMPError(err tcpip.Error, errType byte, errCode byte, extra uint32, pkt *stack.PacketBuffer) {
 	// Update last error first.
 	e.lastErrorMu.Lock()
 	e.lastError = err
@@ -1378,7 +1378,7 @@ func (e *endpoint) HandleControlPacket(typ stack.ControlType, extra uint32, pkt
 			default:
 				panic(fmt.Sprintf("unsupported net proto for infering ICMP type and code: %d", pkt.NetworkProtocolNumber))
 			}
-			e.onICMPError(tcpip.ErrConnectionRefused, errType, errCode, extra, pkt)
+			e.onICMPError(&tcpip.ErrConnectionRefused{}, errType, errCode, extra, pkt)
 			return
 		}
 	}
diff --git a/pkg/tcpip/transport/udp/endpoint_state.go b/pkg/tcpip/transport/udp/endpoint_state.go
index feb53b553..21a6aa460 100644
--- a/pkg/tcpip/transport/udp/endpoint_state.go
+++ b/pkg/tcpip/transport/udp/endpoint_state.go
@@ -37,24 +37,6 @@ func (u *udpPacket) loadData(data buffer.VectorisedView) {
 	u.data = data
 }
 
-// saveLastError is invoked by stateify.
-func (e *endpoint) saveLastError() string {
-	if e.lastError == nil {
-		return ""
-	}
-
-	return e.lastError.String()
-}
-
-// loadLastError is invoked by stateify.
-func (e *endpoint) loadLastError(s string) {
-	if s == "" {
-		return
-	}
-
-	e.lastError = tcpip.StringToError(s)
-}
-
 // beforeSave is invoked by stateify.
 func (e *endpoint) beforeSave() {
 	// Stop incoming packets from being handled (and mutate endpoint state).
@@ -114,7 +96,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 		netProto = header.IPv6ProtocolNumber
 	}
 
-	var err *tcpip.Error
+	var err tcpip.Error
 	if state == StateConnected {
 		e.route, err = e.stack.FindRoute(e.RegisterNICID, e.ID.LocalAddress, e.ID.RemoteAddress, netProto, e.ops.GetMulticastLoop())
 		if err != nil {
@@ -123,7 +105,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 	} else if len(e.ID.LocalAddress) != 0 && !e.isBroadcastOrMulticast(e.RegisterNICID, netProto, e.ID.LocalAddress) { // stateBound
 		// A local unicast address is specified, verify that it's valid.
 		if e.stack.CheckLocalAddress(e.RegisterNICID, netProto, e.ID.LocalAddress) == 0 {
-			panic(tcpip.ErrBadLocalAddress)
+			panic(&tcpip.ErrBadLocalAddress{})
 		}
 	}
 
diff --git a/pkg/tcpip/transport/udp/forwarder.go b/pkg/tcpip/transport/udp/forwarder.go
index aae794506..705ad1f64 100644
--- a/pkg/tcpip/transport/udp/forwarder.go
+++ b/pkg/tcpip/transport/udp/forwarder.go
@@ -69,7 +69,7 @@ func (r *ForwarderRequest) ID() stack.TransportEndpointID {
 }
 
 // CreateEndpoint creates a connected UDP endpoint for the session request.
-func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	netHdr := r.pkt.Network()
 	route, err := r.stack.FindRoute(r.pkt.NICID, netHdr.DestinationAddress(), netHdr.SourceAddress(), r.pkt.NetworkProtocolNumber, false /* multicastLoop */)
 	if err != nil {
diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go
index 91420edd3..427fdd0c9 100644
--- a/pkg/tcpip/transport/udp/protocol.go
+++ b/pkg/tcpip/transport/udp/protocol.go
@@ -54,13 +54,13 @@ func (*protocol) Number() tcpip.TransportProtocolNumber {
 }
 
 // NewEndpoint creates a new udp endpoint.
-func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return newEndpoint(p.stack, netProto, waiterQueue), nil
 }
 
 // NewRawEndpoint creates a new raw UDP endpoint. It implements
 // stack.TransportProtocol.NewRawEndpoint.
-func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+func (p *protocol) NewRawEndpoint(netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, tcpip.Error) {
 	return raw.NewEndpoint(p.stack, netProto, header.UDPProtocolNumber, waiterQueue)
 }
 
@@ -71,7 +71,7 @@ func (*protocol) MinimumPacketSize() int {
 
 // ParsePorts returns the source and destination ports stored in the given udp
 // packet.
-func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
+func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err tcpip.Error) {
 	h := header.UDP(v)
 	return h.SourcePort(), h.DestinationPort(), nil
 }
@@ -94,13 +94,13 @@ func (p *protocol) HandleUnknownDestinationPacket(id stack.TransportEndpointID,
 }
 
 // SetOption implements stack.TransportProtocol.SetOption.
-func (*protocol) SetOption(tcpip.SettableTransportProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) SetOption(tcpip.SettableTransportProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Option implements stack.TransportProtocol.Option.
-func (*protocol) Option(tcpip.GettableTransportProtocolOption) *tcpip.Error {
-	return tcpip.ErrUnknownProtocolOption
+func (*protocol) Option(tcpip.GettableTransportProtocolOption) tcpip.Error {
+	return &tcpip.ErrUnknownProtocolOption{}
 }
 
 // Close implements stack.TransportProtocol.Close.
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index c4794e876..64c5298d3 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -353,7 +353,7 @@ func (c *testContext) cleanup() {
 func (c *testContext) createEndpoint(proto tcpip.NetworkProtocolNumber) {
 	c.t.Helper()
 
-	var err *tcpip.Error
+	var err tcpip.Error
 	c.ep, err = c.s.NewEndpoint(udp.ProtocolNumber, proto, &c.wq)
 	if err != nil {
 		c.t.Fatal("NewEndpoint failed: ", err)
@@ -555,11 +555,11 @@ func TestBindToDeviceOption(t *testing.T) {
 	testActions := []struct {
 		name                 string
 		setBindToDevice      *tcpip.NICID
-		setBindToDeviceError *tcpip.Error
+		setBindToDeviceError tcpip.Error
 		getBindToDevice      int32
 	}{
 		{"GetDefaultValue", nil, nil, 0},
-		{"BindToNonExistent", nicIDPtr(999), tcpip.ErrUnknownDevice, 0},
+		{"BindToNonExistent", nicIDPtr(999), &tcpip.ErrUnknownDevice{}, 0},
 		{"BindToExistent", nicIDPtr(321), nil, 321},
 		{"UnbindToDevice", nicIDPtr(0), nil, 0},
 	}
@@ -599,7 +599,7 @@ func testReadInternal(c *testContext, flow testFlow, packetShouldBeDropped, expe
 
 	var buf bytes.Buffer
 	res, err := c.ep.Read(&buf, tcpip.ReadOptions{NeedRemoteAddr: true})
-	if err == tcpip.ErrWouldBlock {
+	if _, ok := err.(*tcpip.ErrWouldBlock); ok {
 		// Wait for data to become available.
 		select {
 		case <-ch:
@@ -703,8 +703,11 @@ func TestBindReservedPort(t *testing.T) {
 			t.Fatalf("NewEndpoint failed: %s", err)
 		}
 		defer ep.Close()
-		if got, want := ep.Bind(addr), tcpip.ErrPortInUse; got != want {
-			t.Fatalf("got ep.Bind(...) = %s, want = %s", got, want)
+		{
+			err := ep.Bind(addr)
+			if _, ok := err.(*tcpip.ErrPortInUse); !ok {
+				t.Fatalf("got ep.Bind(...) = %s, want = %s", err, &tcpip.ErrPortInUse{})
+			}
 		}
 	}
 
@@ -716,8 +719,11 @@ func TestBindReservedPort(t *testing.T) {
 		defer ep.Close()
 		// We can't bind ipv4-any on the port reserved by the connected endpoint
 		// above, since the endpoint is dual-stack.
-		if got, want := ep.Bind(tcpip.FullAddress{Port: addr.Port}), tcpip.ErrPortInUse; got != want {
-			t.Fatalf("got ep.Bind(...) = %s, want = %s", got, want)
+		{
+			err := ep.Bind(tcpip.FullAddress{Port: addr.Port})
+			if _, ok := err.(*tcpip.ErrPortInUse); !ok {
+				t.Fatalf("got ep.Bind(...) = %s, want = %s", err, &tcpip.ErrPortInUse{})
+			}
 		}
 		// We can bind an ipv4 address on this port, though.
 		if err := ep.Bind(tcpip.FullAddress{Addr: stackAddr, Port: addr.Port}); err != nil {
@@ -806,11 +812,11 @@ func TestV4ReadSelfSource(t *testing.T) {
 	for _, tt := range []struct {
 		name              string
 		handleLocal       bool
-		wantErr           *tcpip.Error
+		wantErr           tcpip.Error
 		wantInvalidSource uint64
 	}{
 		{"HandleLocal", false, nil, 0},
-		{"NoHandleLocal", true, tcpip.ErrWouldBlock, 1},
+		{"NoHandleLocal", true, &tcpip.ErrWouldBlock{}, 1},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			c := newDualTestContextWithOptions(t, defaultMTU, stack.Options{
@@ -959,7 +965,7 @@ func TestV4ReadBroadcastOnBoundToWildcard(t *testing.T) {
 
 // testFailingWrite sends a packet of the given test flow into the UDP endpoint
 // and verifies it fails with the provided error code.
-func testFailingWrite(c *testContext, flow testFlow, wantErr *tcpip.Error) {
+func testFailingWrite(c *testContext, flow testFlow, wantErr tcpip.Error) {
 	c.t.Helper()
 	// Take a snapshot of the stats to validate them at the end of the test.
 	epstats := c.ep.Stats().(*tcpip.TransportEndpointStats).Clone()
@@ -1092,7 +1098,7 @@ func TestDualWriteConnectedToV6(t *testing.T) {
 	testWrite(c, unicastV6)
 
 	// Write to V4 mapped address.
-	testFailingWrite(c, unicastV4in6, tcpip.ErrNetworkUnreachable)
+	testFailingWrite(c, unicastV4in6, &tcpip.ErrNetworkUnreachable{})
 	const want = 1
 	if got := c.ep.Stats().(*tcpip.TransportEndpointStats).SendErrors.NoRoute.Value(); got != want {
 		c.t.Fatalf("Endpoint stat not updated. got %d want %d", got, want)
@@ -1113,7 +1119,7 @@ func TestDualWriteConnectedToV4Mapped(t *testing.T) {
 	testWrite(c, unicastV4in6)
 
 	// Write to v6 address.
-	testFailingWrite(c, unicastV6, tcpip.ErrInvalidEndpointState)
+	testFailingWrite(c, unicastV6, &tcpip.ErrInvalidEndpointState{})
 }
 
 func TestV4WriteOnV6Only(t *testing.T) {
@@ -1123,7 +1129,7 @@ func TestV4WriteOnV6Only(t *testing.T) {
 	c.createEndpointForFlow(unicastV6Only)
 
 	// Write to V4 mapped address.
-	testFailingWrite(c, unicastV4in6, tcpip.ErrNoRoute)
+	testFailingWrite(c, unicastV4in6, &tcpip.ErrNoRoute{})
 }
 
 func TestV6WriteOnBoundToV4Mapped(t *testing.T) {
@@ -1138,7 +1144,7 @@ func TestV6WriteOnBoundToV4Mapped(t *testing.T) {
 	}
 
 	// Write to v6 address.
-	testFailingWrite(c, unicastV6, tcpip.ErrInvalidEndpointState)
+	testFailingWrite(c, unicastV6, &tcpip.ErrInvalidEndpointState{})
 }
 
 func TestV6WriteOnConnected(t *testing.T) {
@@ -1197,8 +1203,11 @@ func TestWriteOnConnectedInvalidPort(t *testing.T) {
 				c.t.Fatalf("c.ep.Write(...) wrote %d bytes, want %d bytes", got, want)
 			}
 
-			if err := c.ep.LastError(); err != tcpip.ErrConnectionRefused {
-				c.t.Fatalf("expected c.ep.LastError() == ErrConnectionRefused, got: %+v", err)
+			{
+				err := c.ep.LastError()
+				if _, ok := err.(*tcpip.ErrConnectionRefused); !ok {
+					c.t.Fatalf("expected c.ep.LastError() == ErrConnectionRefused, got: %+v", err)
+				}
 			}
 		})
 	}
@@ -2308,21 +2317,21 @@ func TestShutdownWrite(t *testing.T) {
 		t.Fatalf("Shutdown failed: %s", err)
 	}
 
-	testFailingWrite(c, unicastV6, tcpip.ErrClosedForSend)
+	testFailingWrite(c, unicastV6, &tcpip.ErrClosedForSend{})
 }
 
-func (c *testContext) checkEndpointWriteStats(incr uint64, want tcpip.TransportEndpointStats, err *tcpip.Error) {
+func (c *testContext) checkEndpointWriteStats(incr uint64, want tcpip.TransportEndpointStats, err tcpip.Error) {
 	got := c.ep.Stats().(*tcpip.TransportEndpointStats).Clone()
-	switch err {
+	switch err.(type) {
 	case nil:
 		want.PacketsSent.IncrementBy(incr)
-	case tcpip.ErrMessageTooLong, tcpip.ErrInvalidOptionValue:
+	case *tcpip.ErrMessageTooLong, *tcpip.ErrInvalidOptionValue:
 		want.WriteErrors.InvalidArgs.IncrementBy(incr)
-	case tcpip.ErrClosedForSend:
+	case *tcpip.ErrClosedForSend:
 		want.WriteErrors.WriteClosed.IncrementBy(incr)
-	case tcpip.ErrInvalidEndpointState:
+	case *tcpip.ErrInvalidEndpointState:
 		want.WriteErrors.InvalidEndpointState.IncrementBy(incr)
-	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
+	case *tcpip.ErrNoRoute, *tcpip.ErrBroadcastDisabled, *tcpip.ErrNetworkUnreachable:
 		want.SendErrors.NoRoute.IncrementBy(incr)
 	default:
 		want.SendErrors.SendToNetworkFailed.IncrementBy(incr)
@@ -2332,11 +2341,11 @@ func (c *testContext) checkEndpointWriteStats(incr uint64, want tcpip.TransportE
 	}
 }
 
-func (c *testContext) checkEndpointReadStats(incr uint64, want tcpip.TransportEndpointStats, err *tcpip.Error) {
+func (c *testContext) checkEndpointReadStats(incr uint64, want tcpip.TransportEndpointStats, err tcpip.Error) {
 	got := c.ep.Stats().(*tcpip.TransportEndpointStats).Clone()
-	switch err {
-	case nil, tcpip.ErrWouldBlock:
-	case tcpip.ErrClosedForReceive:
+	switch err.(type) {
+	case nil, *tcpip.ErrWouldBlock:
+	case *tcpip.ErrClosedForReceive:
 		want.ReadErrors.ReadClosed.IncrementBy(incr)
 	default:
 		c.t.Errorf("Endpoint error missing stats update err %v", err)
@@ -2509,14 +2518,26 @@ func TestOutgoingSubnetBroadcast(t *testing.T) {
 				Port: 80,
 			}
 			opts := tcpip.WriteOptions{To: &to}
-			expectedErrWithoutBcastOpt := tcpip.ErrBroadcastDisabled
+			expectedErrWithoutBcastOpt := func(err tcpip.Error) tcpip.Error {
+				if _, ok := err.(*tcpip.ErrBroadcastDisabled); ok {
+					return nil
+				}
+				return &tcpip.ErrBroadcastDisabled{}
+			}
 			if !test.requiresBroadcastOpt {
 				expectedErrWithoutBcastOpt = nil
 			}
 
 			r.Reset(data)
-			if n, err := ep.Write(&r, opts); err != expectedErrWithoutBcastOpt {
-				t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, expectedErrWithoutBcastOpt)
+			{
+				n, err := ep.Write(&r, opts)
+				if expectedErrWithoutBcastOpt != nil {
+					if want := expectedErrWithoutBcastOpt(err); want != nil {
+						t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, want)
+					}
+				} else if err != nil {
+					t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, nil)", opts, n, err)
+				}
 			}
 
 			ep.SocketOptions().SetBroadcast(true)
@@ -2529,8 +2550,15 @@ func TestOutgoingSubnetBroadcast(t *testing.T) {
 			ep.SocketOptions().SetBroadcast(false)
 
 			r.Reset(data)
-			if n, err := ep.Write(&r, opts); err != expectedErrWithoutBcastOpt {
-				t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, expectedErrWithoutBcastOpt)
+			{
+				n, err := ep.Write(&r, opts)
+				if expectedErrWithoutBcastOpt != nil {
+					if want := expectedErrWithoutBcastOpt(err); want != nil {
+						t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, %s)", opts, n, err, want)
+					}
+				} else if err != nil {
+					t.Fatalf("got ep.Write(_, %#v) = (%d, %s), want = (_, nil)", opts, n, err)
+				}
 			}
 		})
 	}