Merge release-20201216.0-105-g25b5ec713 (automated)

21 files changed, 164 insertions, 295 deletions

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 57f224120..94fb425b2 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -36,7 +36,6 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/amutex"
 	"gvisor.dev/gvisor/pkg/binary"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/log"
@@ -459,18 +458,10 @@ func (i *ioSequencePayload) DropFirst(n int) {
 // Write implements fs.FileOperations.Write.
 func (s *SocketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
 	f := &ioSequencePayload{ctx: ctx, src: src}
-	n, resCh, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
+	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
 	if err == tcpip.ErrWouldBlock {
 		return 0, syserror.ErrWouldBlock
 	}
-
-	if resCh != nil {
-		if err := amutex.Block(ctx, resCh); err != nil {
-			return 0, err
-		}
-		n, _, err = s.Endpoint.Write(f, tcpip.WriteOptions{})
-	}
-
 	if err != nil {
 		return 0, syserr.TranslateNetstackError(err).ToError()
 	}
@@ -526,24 +517,12 @@ func (r *readerPayload) Payload(size int) ([]byte, *tcpip.Error) {
 // ReadFrom implements fs.FileOperations.ReadFrom.
 func (s *SocketOperations) ReadFrom(ctx context.Context, _ *fs.File, r io.Reader, count int64) (int64, error) {
 	f := &readerPayload{ctx: ctx, r: r, count: count}
-	n, resCh, err := s.Endpoint.Write(f, tcpip.WriteOptions{
+	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{
 		// Reads may be destructive but should be very fast,
 		// so we can't release the lock while copying data.
 		Atomic: true,
 	})
 	if err == tcpip.ErrWouldBlock {
-		return 0, syserror.ErrWouldBlock
-	}
-
-	if resCh != nil {
-		if err := amutex.Block(ctx, resCh); err != nil {
-			return 0, err
-		}
-		n, _, err = s.Endpoint.Write(f, tcpip.WriteOptions{
-			Atomic: true, // See above.
-		})
-	}
-	if err == tcpip.ErrWouldBlock {
 		return n, syserror.ErrWouldBlock
 	} else if err != nil {
 		return int64(n), f.err // Propagate error.
@@ -2836,13 +2815,7 @@ func (s *socketOpsCommon) SendMsg(t *kernel.Task, src usermem.IOSequence, to []b
 	}
 
 	v := &ioSequencePayload{t, src}
-	n, resCh, err := s.Endpoint.Write(v, opts)
-	if resCh != nil {
-		if err := t.Block(resCh); err != nil {
-			return 0, syserr.FromError(err)
-		}
-		n, _, err = s.Endpoint.Write(v, opts)
-	}
+	n, err := s.Endpoint.Write(v, opts)
 	dontWait := flags&linux.MSG_DONTWAIT != 0
 	if err == nil && (n >= v.src.NumBytes() || dontWait) {
 		// Complete write.
@@ -2861,7 +2834,7 @@ func (s *socketOpsCommon) SendMsg(t *kernel.Task, src usermem.IOSequence, to []b
 	v.DropFirst(int(n))
 	total := n
 	for {
-		n, _, err = s.Endpoint.Write(v, opts)
+		n, err = s.Endpoint.Write(v, opts)
 		v.DropFirst(int(n))
 		total += n
 
diff --git a/pkg/sentry/socket/netstack/netstack_vfs2.go b/pkg/sentry/socket/netstack/netstack_vfs2.go
index b756bfca0..6f70b02fc 100644
--- a/pkg/sentry/socket/netstack/netstack_vfs2.go
+++ b/pkg/sentry/socket/netstack/netstack_vfs2.go
@@ -16,7 +16,6 @@ package netstack
 
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/amutex"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/marshal"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
@@ -131,18 +130,10 @@ func (s *SocketVFS2) Write(ctx context.Context, src usermem.IOSequence, opts vfs
 	}
 
 	f := &ioSequencePayload{ctx: ctx, src: src}
-	n, resCh, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
+	n, err := s.Endpoint.Write(f, tcpip.WriteOptions{})
 	if err == tcpip.ErrWouldBlock {
 		return 0, syserror.ErrWouldBlock
 	}
-
-	if resCh != nil {
-		if err := amutex.Block(ctx, resCh); err != nil {
-			return 0, err
-		}
-		n, _, err = s.Endpoint.Write(f, tcpip.WriteOptions{})
-	}
-
 	if err != nil {
 		return 0, syserr.TranslateNetstackError(err).ToError()
 	}
diff --git a/pkg/syserr/netstack.go b/pkg/syserr/netstack.go
index 2756d4471..cb8981633 100644
--- a/pkg/syserr/netstack.go
+++ b/pkg/syserr/netstack.go
@@ -93,7 +93,6 @@ func init() {
 	addErrMapping(tcpip.ErrConnectionAborted, ErrConnectionAborted)
 	addErrMapping(tcpip.ErrNoSuchFile, ErrNoSuchFile)
 	addErrMapping(tcpip.ErrInvalidOptionValue, ErrInvalidOptionValue)
-	addErrMapping(tcpip.ErrNoLinkAddress, ErrHostDown)
 	addErrMapping(tcpip.ErrBadAddress, ErrBadAddress)
 	addErrMapping(tcpip.ErrNetworkUnreachable, ErrNetworkUnreachable)
 	addErrMapping(tcpip.ErrMessageTooLong, ErrMessageTooLong)
diff --git a/pkg/tcpip/adapters/gonet/gonet.go b/pkg/tcpip/adapters/gonet/gonet.go
index 7193f56ad..85a0b8b90 100644
--- a/pkg/tcpip/adapters/gonet/gonet.go
+++ b/pkg/tcpip/adapters/gonet/gonet.go
@@ -397,22 +397,9 @@ func (c *TCPConn) Write(b []byte) (int, error) {
 		}
 
 		var n int64
-		var resCh <-chan struct{}
-		n, resCh, err = c.ep.Write(tcpip.SlicePayload(v), tcpip.WriteOptions{})
+		n, err = c.ep.Write(tcpip.SlicePayload(v), tcpip.WriteOptions{})
 		nbytes += int(n)
 		v.TrimFront(int(n))
-
-		if resCh != nil {
-			select {
-			case <-deadline:
-				return nbytes, c.newOpError("write", &timeoutError{})
-			case <-resCh:
-			}
-
-			n, _, err = c.ep.Write(tcpip.SlicePayload(v), tcpip.WriteOptions{})
-			nbytes += int(n)
-			v.TrimFront(int(n))
-		}
 	}
 
 	if err == nil {
@@ -666,17 +653,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 	v := buffer.NewView(len(b))
 	copy(v, b)
 
-	n, resCh, err := c.ep.Write(tcpip.SlicePayload(v), wopts)
-	if resCh != nil {
-		select {
-		case <-deadline:
-			return int(n), c.newRemoteOpError("write", addr, &timeoutError{})
-		case <-resCh:
-		}
-
-		n, _, err = c.ep.Write(tcpip.SlicePayload(v), wopts)
-	}
-
+	n, err := c.ep.Write(tcpip.SlicePayload(v), wopts)
 	if err == tcpip.ErrWouldBlock {
 		// Create wait queue entry that notifies a channel.
 		waitEntry, notifyCh := waiter.NewChannelEntry(nil)
@@ -689,7 +666,7 @@ func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 			case <-notifyCh:
 			}
 
-			n, _, err = c.ep.Write(tcpip.SlicePayload(v), wopts)
+			n, err = c.ep.Write(tcpip.SlicePayload(v), wopts)
 			if err != tcpip.ErrWouldBlock {
 				break
 			}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index e9ff70d04..cc045c7a9 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -64,6 +64,7 @@ const (
 
 var ipv4BroadcastAddr = header.IPv4Broadcast.WithPrefix()
 
+var _ stack.LinkResolvableNetworkEndpoint = (*endpoint)(nil)
 var _ stack.GroupAddressableEndpoint = (*endpoint)(nil)
 var _ stack.AddressableEndpoint = (*endpoint)(nil)
 var _ stack.NetworkEndpoint = (*endpoint)(nil)
@@ -87,6 +88,21 @@ type endpoint struct {
 	}
 }
 
+// HandleLinkResolutionFailure implements stack.LinkResolvableNetworkEndpoint.
+func (e *endpoint) HandleLinkResolutionFailure(pkt *stack.PacketBuffer) {
+	// handleControl expects the entire offending packet to be in the packet
+	// buffer's data field.
+	pkt = stack.NewPacketBuffer(stack.PacketBufferOptions{
+		Data: buffer.NewVectorisedView(pkt.Size(), pkt.Views()),
+	})
+	pkt.NICID = e.nic.ID()
+	pkt.NetworkProtocolNumber = ProtocolNumber
+	// Use the same control type as an ICMPv4 destination host unreachable error
+	// since the host is considered unreachable if we cannot resolve the link
+	// address to the next hop.
+	e.handleControl(stack.ControlNoRoute, 0, pkt)
+}
+
 // NewEndpoint creates a new ipv4 endpoint.
 func (p *protocol) NewEndpoint(nic stack.NetworkInterface, _ stack.LinkAddressCache, _ stack.NUDHandler, dispatcher stack.TransportDispatcher) stack.NetworkEndpoint {
 	e := &endpoint{
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index f2018d073..2f82c3d5f 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -163,6 +163,7 @@ func getLabel(addr tcpip.Address) uint8 {
 	panic(fmt.Sprintf("should have a label for address = %s", addr))
 }
 
+var _ stack.LinkResolvableNetworkEndpoint = (*endpoint)(nil)
 var _ stack.GroupAddressableEndpoint = (*endpoint)(nil)
 var _ stack.AddressableEndpoint = (*endpoint)(nil)
 var _ stack.NetworkEndpoint = (*endpoint)(nil)
@@ -224,6 +225,18 @@ type OpaqueInterfaceIdentifierOptions struct {
 	SecretKey []byte
 }
 
+// HandleLinkResolutionFailure implements stack.LinkResolvableNetworkEndpoint.
+func (e *endpoint) HandleLinkResolutionFailure(pkt *stack.PacketBuffer) {
+	// handleControl expects the entire offending packet to be in the packet
+	// buffer's data field.
+	pkt = stack.NewPacketBuffer(stack.PacketBufferOptions{
+		Data: buffer.NewVectorisedView(pkt.Size(), pkt.Views()),
+	})
+	pkt.NICID = e.nic.ID()
+	pkt.NetworkProtocolNumber = ProtocolNumber
+	e.handleControl(stack.ControlAddressUnreachable, 0, pkt)
+}
+
 // onAddressAssignedLocked handles an address being assigned.
 //
 // Precondition: e.mu must be exclusively locked.
diff --git a/pkg/tcpip/stack/packet_buffer.go b/pkg/tcpip/stack/packet_buffer.go
index 664cc6fa0..5f216ca21 100644
--- a/pkg/tcpip/stack/packet_buffer.go
+++ b/pkg/tcpip/stack/packet_buffer.go
@@ -268,17 +268,6 @@ func (pk *PacketBuffer) Clone() *PacketBuffer {
 	}
 }
 
-// SourceLinkAddress returns the source link address of the packet.
-func (pk *PacketBuffer) SourceLinkAddress() tcpip.LinkAddress {
-	link := pk.LinkHeader().View()
-
-	if link.IsEmpty() {
-		return ""
-	}
-
-	return header.Ethernet(link).SourceAddress()
-}
-
 // Network returns the network header as a header.Network.
 //
 // Network should only be called when NetworkHeader has been set.
diff --git a/pkg/tcpip/stack/pending_packets.go b/pkg/tcpip/stack/pending_packets.go
index 4a3adcf33..bded8814e 100644
--- a/pkg/tcpip/stack/pending_packets.go
+++ b/pkg/tcpip/stack/pending_packets.go
@@ -101,10 +101,12 @@ func (f *packetsPendingLinkResolution) enqueue(ch <-chan struct{}, r *Route, pro
 		}
 
 		for _, p := range packets {
-			if cancelled {
-				p.route.Stats().IP.OutgoingPacketErrors.Increment()
-			} else if p.route.IsResolutionRequired() {
+			if cancelled || p.route.IsResolutionRequired() {
 				p.route.Stats().IP.OutgoingPacketErrors.Increment()
+
+				if linkResolvableEP, ok := p.route.outgoingNIC.getNetworkEndpoint(p.route.NetProto).(LinkResolvableNetworkEndpoint); ok {
+					linkResolvableEP.HandleLinkResolutionFailure(pkt)
+				}
 			} else {
 				p.route.outgoingNIC.writePacket(p.route, nil /* gso */, p.proto, p.pkt)
 			}
diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 4795208b4..924790779 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -55,7 +55,19 @@ type ControlType int
 // The following are the allowed values for ControlType values.
 // TODO(http://gvisor.dev/issue/3210): Support time exceeded messages.
 const (
-	ControlNetworkUnreachable ControlType = iota
+	// ControlAddressUnreachable indicates that an IPv6 packet did not reach its
+	// destination as the destination address was unreachable.
+	//
+	// This maps to the ICMPv6 Destination Ureachable Code 3 error; see
+	// RFC 4443 section 3.1 for more details.
+	ControlAddressUnreachable ControlType = iota
+	ControlNetworkUnreachable
+	// ControlNoRoute indicates that an IPv4 packet did not reach its destination
+	// because the destination host was unreachable.
+	//
+	// This maps to the ICMPv4 Destination Ureachable Code 1 error; see
+	// RFC 791's Destination Unreachable Message section (page 4) for more
+	// details.
 	ControlNoRoute
 	ControlPacketTooBig
 	ControlPortUnreachable
@@ -503,6 +515,13 @@ type NetworkInterface interface {
 	WritePacketToRemote(tcpip.LinkAddress, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) *tcpip.Error
 }
 
+// LinkResolvableNetworkEndpoint handles link resolution events.
+type LinkResolvableNetworkEndpoint interface {
+	// HandleLinkResolutionFailure is called when link resolution prevents the
+	// argument from having been sent.
+	HandleLinkResolutionFailure(*PacketBuffer)
+}
+
 // NetworkEndpoint is the interface that needs to be implemented by endpoints
 // of network layer protocols (e.g., ipv4, ipv6).
 type NetworkEndpoint interface {
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index f798056c0..002ddaf67 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -104,7 +104,6 @@ var (
 	ErrConnectionAborted         = &Error{msg: "connection aborted"}
 	ErrNoSuchFile                = &Error{msg: "no such file"}
 	ErrInvalidOptionValue        = &Error{msg: "invalid option value specified"}
-	ErrNoLinkAddress             = &Error{msg: "no remote link address"}
 	ErrBadAddress                = &Error{msg: "bad address"}
 	ErrNetworkUnreachable        = &Error{msg: "network is unreachable"}
 	ErrMessageTooLong            = &Error{msg: "message too long"}
@@ -154,7 +153,6 @@ func StringToError(s string) *Error {
 			ErrConnectionAborted,
 			ErrNoSuchFile,
 			ErrInvalidOptionValue,
-			ErrNoLinkAddress,
 			ErrBadAddress,
 			ErrNetworkUnreachable,
 			ErrMessageTooLong,
@@ -640,12 +638,7 @@ 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.
-	//
-	// For UDP and Ping sockets if address resolution is required,
-	// ErrNoLinkAddress and a notification channel is returned for the caller to
-	// block. Channel is closed once address resolution is complete (success or
-	// not). The channel is only non-nil in this case.
-	Write(Payloader, WriteOptions) (int64, <-chan struct{}, *Error)
+	Write(Payloader, WriteOptions) (int64, *Error)
 
 	// Connect connects the endpoint to its peer. Specifying a NIC is
 	// optional.
@@ -1784,9 +1777,6 @@ type SendErrors struct {
 
 	// NoRoute is the number of times we failed to resolve IP route.
 	NoRoute StatCounter
-
-	// NoLinkAddr is the number of times we failed to resolve ARP.
-	NoLinkAddr StatCounter
 }
 
 // ReadErrors collects segment read errors from an endpoint read call.
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index c32fe5c4f..87277fbd3 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -236,8 +236,8 @@ 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, <-chan struct{}, *tcpip.Error) {
-	n, ch, err := e.write(p, opts)
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+	n, err := e.write(p, opts)
 	switch err {
 	case nil:
 		e.stats.PacketsSent.Increment()
@@ -247,8 +247,6 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		e.stats.WriteErrors.WriteClosed.Increment()
 	case tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoLinkAddress:
-		e.stats.SendErrors.NoLinkAddr.Increment()
 	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
@@ -256,13 +254,13 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		// For all other errors when writing to the network layer.
 		e.stats.SendErrors.SendToNetworkFailed.Increment()
 	}
-	return n, ch, err
+	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *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, nil, tcpip.ErrInvalidOptionValue
+		return 0, tcpip.ErrInvalidOptionValue
 	}
 
 	to := opts.To
@@ -272,14 +270,14 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 
 	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
 	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-		return 0, nil, tcpip.ErrClosedForSend
+		return 0, tcpip.ErrClosedForSend
 	}
 
 	// Prepare for write.
 	for {
 		retry, err := e.prepareForWrite(to)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 
 		if !retry {
@@ -294,7 +292,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		nicID := to.NIC
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
-				return 0, nil, tcpip.ErrNoRoute
+				return 0, tcpip.ErrNoRoute
 			}
 
 			nicID = e.BindNICID
@@ -302,31 +300,22 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 
 		dst, netProto, err := e.checkV4MappedLocked(*to)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 
 		// Find the endpoint.
 		r, err := e.stack.FindRoute(nicID, e.BindAddr, dst.Addr, netProto, false /* multicastLoop */)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 		defer r.Release()
 
 		route = r
 	}
 
-	if route.IsResolutionRequired() {
-		if ch, err := route.Resolve(nil); err != nil {
-			if err == tcpip.ErrWouldBlock {
-				return 0, ch, tcpip.ErrNoLinkAddress
-			}
-			return 0, nil, err
-		}
-	}
-
 	v, err := p.FullPayload()
 	if err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 
 	switch e.NetProto {
@@ -338,10 +327,10 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	}
 
 	if err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 
-	return int64(len(v)), nil, nil
+	return int64(len(v)), nil
 }
 
 // SetSockOpt sets a socket option.
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
index 3ab060751..c3b3b8d34 100644
--- a/pkg/tcpip/transport/packet/endpoint.go
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -207,9 +207,9 @@ func (ep *endpoint) Read(dst io.Writer, count int, opts tcpip.ReadOptions) (tcpi
 	return res, nil
 }
 
-func (*endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *tcpip.Error) {
+func (*endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
 	// TODO(gvisor.dev/issue/173): Implement.
-	return 0, nil, tcpip.ErrInvalidOptionValue
+	return 0, tcpip.ErrInvalidOptionValue
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect. Packet sockets cannot be
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index dd260535f..425bcf3ee 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -234,20 +234,20 @@ func (e *endpoint) Read(dst io.Writer, count int, opts tcpip.ReadOptions) (tcpip
 }
 
 // Write implements tcpip.Endpoint.Write.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *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, nil, 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, nil, tcpip.ErrInvalidOptionValue
+			return 0, tcpip.ErrInvalidOptionValue
 		}
 	}
 
-	n, ch, err := e.write(p, opts)
+	n, err := e.write(p, opts)
 	switch err {
 	case nil:
 		e.stats.PacketsSent.Increment()
@@ -257,8 +257,6 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		e.stats.WriteErrors.WriteClosed.Increment()
 	case tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoLinkAddress:
-		e.stats.SendErrors.NoLinkAddr.Increment()
 	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
@@ -266,25 +264,25 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		// For all other errors when writing to the network layer.
 		e.stats.SendErrors.SendToNetworkFailed.Increment()
 	}
-	return n, ch, err
+	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *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, nil, tcpip.ErrInvalidOptionValue
+		return 0, tcpip.ErrInvalidOptionValue
 	}
 
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
 	if e.closed {
-		return 0, nil, tcpip.ErrInvalidEndpointState
+		return 0, tcpip.ErrInvalidEndpointState
 	}
 
 	payloadBytes, err := p.FullPayload()
 	if err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 
 	// If this is an unassociated socket and callee provided a nonzero
@@ -292,7 +290,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	if e.ops.GetHeaderIncluded() {
 		ip := header.IPv4(payloadBytes)
 		if !ip.IsValid(len(payloadBytes)) {
-			return 0, nil, tcpip.ErrInvalidOptionValue
+			return 0, tcpip.ErrInvalidOptionValue
 		}
 		dstAddr := ip.DestinationAddress()
 		// Update dstAddr with the address in the IP header, unless
@@ -313,7 +311,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		// If the user doesn't specify a destination, they should have
 		// connected to another address.
 		if !e.connected {
-			return 0, nil, tcpip.ErrDestinationRequired
+			return 0, tcpip.ErrDestinationRequired
 		}
 
 		return e.finishWrite(payloadBytes, e.route)
@@ -323,42 +321,30 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	// 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, nil, tcpip.ErrNoRoute
+		return 0, tcpip.ErrNoRoute
 	}
 
 	// Find the route to the destination. If BindAddress is 0,
 	// FindRoute will choose an appropriate source address.
 	route, err := e.stack.FindRoute(nic, e.BindAddr, opts.To.Addr, e.NetProto, false)
 	if err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 
-	n, ch, err := e.finishWrite(payloadBytes, route)
+	n, err := e.finishWrite(payloadBytes, route)
 	route.Release()
-	return n, ch, err
+	return n, err
 }
 
 // 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, <-chan struct{}, *tcpip.Error) {
-	// We may need to resolve the route (match a link layer address to the
-	// network address). If that requires blocking (e.g. to use ARP),
-	// return a channel on which the caller can wait.
-	if route.IsResolutionRequired() {
-		if ch, err := route.Resolve(nil); err != nil {
-			if err == tcpip.ErrWouldBlock {
-				return 0, ch, tcpip.ErrNoLinkAddress
-			}
-			return 0, nil, err
-		}
-	}
-
+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(),
 		})
 		if err := route.WriteHeaderIncludedPacket(pkt); err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 	} else {
 		pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
@@ -371,11 +357,11 @@ func (e *endpoint) finishWrite(payloadBytes []byte, route *stack.Route) (int64,
 			TTL:      route.DefaultTTL(),
 			TOS:      stack.DefaultTOS,
 		}, pkt); err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 	}
 
-	return int64(len(payloadBytes)), nil, nil
+	return int64(len(payloadBytes)), nil
 }
 
 // Disconnect implements tcpip.Endpoint.Disconnect.
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 2d96a65bd..9e8872fc9 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -210,7 +210,6 @@ func (l *listenContext) createConnectingEndpoint(s *segment, iss seqnum.Value, i
 	if err != nil {
 		return nil, err
 	}
-	route.ResolveWith(s.remoteLinkAddr)
 
 	n := newEndpoint(l.stack, netProto, queue)
 	n.ops.SetV6Only(l.v6Only)
@@ -573,7 +572,6 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) *tcpip.Er
 				return err
 			}
 			defer route.Release()
-			route.ResolveWith(s.remoteLinkAddr)
 
 			// Send SYN without window scaling because we currently
 			// don't encode this information in the cookie.
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index a00ef97c6..f45d26a87 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -460,66 +460,9 @@ func (h *handshake) processSegments() *tcpip.Error {
 	return nil
 }
 
-func (h *handshake) resolveRoute() *tcpip.Error {
-	// Set up the wakers.
-	var s sleep.Sleeper
-	resolutionWaker := &sleep.Waker{}
-	s.AddWaker(resolutionWaker, wakerForResolution)
-	s.AddWaker(&h.ep.notificationWaker, wakerForNotification)
-	defer s.Done()
-
-	// Initial action is to resolve route.
-	index := wakerForResolution
-	attemptedResolution := false
-	for {
-		switch index {
-		case wakerForResolution:
-			if _, err := h.ep.route.Resolve(resolutionWaker.Assert); err != tcpip.ErrWouldBlock {
-				if err != nil {
-					h.ep.stats.SendErrors.NoRoute.Increment()
-				}
-				// Either success (err == nil) or failure.
-				return err
-			}
-			if attemptedResolution {
-				h.ep.stats.SendErrors.NoLinkAddr.Increment()
-				return tcpip.ErrNoLinkAddress
-			}
-			attemptedResolution = true
-			// Resolution not completed. Keep trying...
-
-		case wakerForNotification:
-			n := h.ep.fetchNotifications()
-			if n&notifyClose != 0 {
-				return tcpip.ErrAborted
-			}
-			if n&notifyDrain != 0 {
-				close(h.ep.drainDone)
-				h.ep.mu.Unlock()
-				<-h.ep.undrain
-				h.ep.mu.Lock()
-			}
-			if n&notifyError != 0 {
-				return h.ep.lastErrorLocked()
-			}
-		}
-
-		// Wait for notification.
-		h.ep.mu.Unlock()
-		index, _ = s.Fetch(true /* block */)
-		h.ep.mu.Lock()
-	}
-}
-
 // start resolves the route if necessary and sends the first
 // SYN/SYN-ACK.
 func (h *handshake) start() *tcpip.Error {
-	if h.ep.route.IsResolutionRequired() {
-		if err := h.resolveRoute(); err != nil {
-			return err
-		}
-	}
-
 	h.startTime = time.Now()
 	h.ep.amss = calculateAdvertisedMSS(h.ep.userMSS, h.ep.route)
 	var sackEnabled tcpip.TCPSACKEnabled
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 25b180fa5..ddbed7e46 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1507,7 +1507,7 @@ func (e *endpoint) isEndpointWritableLocked() (int, *tcpip.Error) {
 }
 
 // Write writes data to the endpoint's peer.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *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.
@@ -1520,7 +1520,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		e.sndBufMu.Unlock()
 		e.UnlockUser()
 		e.stats.WriteErrors.WriteClosed.Increment()
-		return 0, nil, err
+		return 0, err
 	}
 
 	// We can release locks while copying data.
@@ -1541,7 +1541,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 			e.sndBufMu.Unlock()
 			e.UnlockUser()
 		}
-		return 0, nil, perr
+		return 0, perr
 	}
 
 	if !opts.Atomic {
@@ -1555,7 +1555,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 			e.sndBufMu.Unlock()
 			e.UnlockUser()
 			e.stats.WriteErrors.WriteClosed.Increment()
-			return 0, nil, err
+			return 0, err
 		}
 
 		// Discard any excess data copied in due to avail being reduced due
@@ -1575,7 +1575,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	// Do the work inline.
 	e.handleWrite()
 	e.UnlockUser()
-	return int64(len(v)), nil, nil
+	return int64(len(v)), nil
 }
 
 // selectWindowLocked returns the new window without checking for shrinking or scaling
@@ -2779,6 +2779,9 @@ func (e *endpoint) HandleControlPacket(typ stack.ControlType, extra uint32, pkt
 	case stack.ControlNoRoute:
 		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)
+
 	case stack.ControlNetworkUnreachable:
 		e.onICMPError(tcpip.ErrNetworkUnreachable, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6NetworkUnreachable), extra, pkt)
 	}
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index c9e194f82..1720370c9 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -222,7 +222,6 @@ func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) *tcpip.Error
 		return err
 	}
 	defer route.Release()
-	route.ResolveWith(s.remoteLinkAddr)
 
 	// Get the seqnum from the packet if the ack flag is set.
 	seq := seqnum.Value(0)
diff --git a/pkg/tcpip/transport/tcp/segment.go b/pkg/tcpip/transport/tcp/segment.go
index c5a6d2fba..7cca4def5 100644
--- a/pkg/tcpip/transport/tcp/segment.go
+++ b/pkg/tcpip/transport/tcp/segment.go
@@ -49,11 +49,10 @@ type segment struct {
 
 	// TODO(gvisor.dev/issue/4417): Hold a stack.PacketBuffer instead of
 	// individual members for link/network packet info.
-	srcAddr        tcpip.Address
-	dstAddr        tcpip.Address
-	netProto       tcpip.NetworkProtocolNumber
-	nicID          tcpip.NICID
-	remoteLinkAddr tcpip.LinkAddress
+	srcAddr  tcpip.Address
+	dstAddr  tcpip.Address
+	netProto tcpip.NetworkProtocolNumber
+	nicID    tcpip.NICID
 
 	data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
 
@@ -89,13 +88,12 @@ type segment struct {
 func newIncomingSegment(id stack.TransportEndpointID, pkt *stack.PacketBuffer) *segment {
 	netHdr := pkt.Network()
 	s := &segment{
-		refCnt:         1,
-		id:             id,
-		srcAddr:        netHdr.SourceAddress(),
-		dstAddr:        netHdr.DestinationAddress(),
-		netProto:       pkt.NetworkProtocolNumber,
-		nicID:          pkt.NICID,
-		remoteLinkAddr: pkt.SourceLinkAddress(),
+		refCnt:   1,
+		id:       id,
+		srcAddr:  netHdr.SourceAddress(),
+		dstAddr:  netHdr.DestinationAddress(),
+		netProto: pkt.NetworkProtocolNumber,
+		nicID:    pkt.NICID,
 	}
 	s.data = pkt.Data.Clone(s.views[:])
 	s.hdr = header.TCP(pkt.TransportHeader().View())
@@ -128,7 +126,6 @@ func (s *segment) clone() *segment {
 		window:         s.window,
 		netProto:       s.netProto,
 		nicID:          s.nicID,
-		remoteLinkAddr: s.remoteLinkAddr,
 		rcvdTime:       s.rcvdTime,
 		xmitTime:       s.xmitTime,
 		xmitCount:      s.xmitCount,
diff --git a/pkg/tcpip/transport/tcp/tcp_state_autogen.go b/pkg/tcpip/transport/tcp/tcp_state_autogen.go
index 251909dae..6131d151a 100644
--- a/pkg/tcpip/transport/tcp/tcp_state_autogen.go
+++ b/pkg/tcpip/transport/tcp/tcp_state_autogen.go
@@ -600,7 +600,6 @@ func (s *segment) StateFields() []string {
 		"dstAddr",
 		"netProto",
 		"nicID",
-		"remoteLinkAddr",
 		"data",
 		"hdr",
 		"sequenceNumber",
@@ -625,13 +624,13 @@ func (s *segment) beforeSave() {}
 func (s *segment) StateSave(stateSinkObject state.Sink) {
 	s.beforeSave()
 	var dataValue buffer.VectorisedView = s.saveData()
-	stateSinkObject.SaveValue(9, dataValue)
+	stateSinkObject.SaveValue(8, dataValue)
 	var optionsValue []byte = s.saveOptions()
-	stateSinkObject.SaveValue(18, optionsValue)
+	stateSinkObject.SaveValue(17, optionsValue)
 	var rcvdTimeValue unixTime = s.saveRcvdTime()
-	stateSinkObject.SaveValue(20, rcvdTimeValue)
+	stateSinkObject.SaveValue(19, rcvdTimeValue)
 	var xmitTimeValue unixTime = s.saveXmitTime()
-	stateSinkObject.SaveValue(21, xmitTimeValue)
+	stateSinkObject.SaveValue(20, xmitTimeValue)
 	stateSinkObject.Save(0, &s.segmentEntry)
 	stateSinkObject.Save(1, &s.refCnt)
 	stateSinkObject.Save(2, &s.ep)
@@ -640,19 +639,18 @@ func (s *segment) StateSave(stateSinkObject state.Sink) {
 	stateSinkObject.Save(5, &s.dstAddr)
 	stateSinkObject.Save(6, &s.netProto)
 	stateSinkObject.Save(7, &s.nicID)
-	stateSinkObject.Save(8, &s.remoteLinkAddr)
-	stateSinkObject.Save(10, &s.hdr)
-	stateSinkObject.Save(11, &s.sequenceNumber)
-	stateSinkObject.Save(12, &s.ackNumber)
-	stateSinkObject.Save(13, &s.flags)
-	stateSinkObject.Save(14, &s.window)
-	stateSinkObject.Save(15, &s.csum)
-	stateSinkObject.Save(16, &s.csumValid)
-	stateSinkObject.Save(17, &s.parsedOptions)
-	stateSinkObject.Save(19, &s.hasNewSACKInfo)
-	stateSinkObject.Save(22, &s.xmitCount)
-	stateSinkObject.Save(23, &s.acked)
-	stateSinkObject.Save(24, &s.dataMemSize)
+	stateSinkObject.Save(9, &s.hdr)
+	stateSinkObject.Save(10, &s.sequenceNumber)
+	stateSinkObject.Save(11, &s.ackNumber)
+	stateSinkObject.Save(12, &s.flags)
+	stateSinkObject.Save(13, &s.window)
+	stateSinkObject.Save(14, &s.csum)
+	stateSinkObject.Save(15, &s.csumValid)
+	stateSinkObject.Save(16, &s.parsedOptions)
+	stateSinkObject.Save(18, &s.hasNewSACKInfo)
+	stateSinkObject.Save(21, &s.xmitCount)
+	stateSinkObject.Save(22, &s.acked)
+	stateSinkObject.Save(23, &s.dataMemSize)
 }
 
 func (s *segment) afterLoad() {}
@@ -666,23 +664,22 @@ func (s *segment) StateLoad(stateSourceObject state.Source) {
 	stateSourceObject.Load(5, &s.dstAddr)
 	stateSourceObject.Load(6, &s.netProto)
 	stateSourceObject.Load(7, &s.nicID)
-	stateSourceObject.Load(8, &s.remoteLinkAddr)
-	stateSourceObject.Load(10, &s.hdr)
-	stateSourceObject.Load(11, &s.sequenceNumber)
-	stateSourceObject.Load(12, &s.ackNumber)
-	stateSourceObject.Load(13, &s.flags)
-	stateSourceObject.Load(14, &s.window)
-	stateSourceObject.Load(15, &s.csum)
-	stateSourceObject.Load(16, &s.csumValid)
-	stateSourceObject.Load(17, &s.parsedOptions)
-	stateSourceObject.Load(19, &s.hasNewSACKInfo)
-	stateSourceObject.Load(22, &s.xmitCount)
-	stateSourceObject.Load(23, &s.acked)
-	stateSourceObject.Load(24, &s.dataMemSize)
-	stateSourceObject.LoadValue(9, new(buffer.VectorisedView), func(y interface{}) { s.loadData(y.(buffer.VectorisedView)) })
-	stateSourceObject.LoadValue(18, new([]byte), func(y interface{}) { s.loadOptions(y.([]byte)) })
-	stateSourceObject.LoadValue(20, new(unixTime), func(y interface{}) { s.loadRcvdTime(y.(unixTime)) })
-	stateSourceObject.LoadValue(21, new(unixTime), func(y interface{}) { s.loadXmitTime(y.(unixTime)) })
+	stateSourceObject.Load(9, &s.hdr)
+	stateSourceObject.Load(10, &s.sequenceNumber)
+	stateSourceObject.Load(11, &s.ackNumber)
+	stateSourceObject.Load(12, &s.flags)
+	stateSourceObject.Load(13, &s.window)
+	stateSourceObject.Load(14, &s.csum)
+	stateSourceObject.Load(15, &s.csumValid)
+	stateSourceObject.Load(16, &s.parsedOptions)
+	stateSourceObject.Load(18, &s.hasNewSACKInfo)
+	stateSourceObject.Load(21, &s.xmitCount)
+	stateSourceObject.Load(22, &s.acked)
+	stateSourceObject.Load(23, &s.dataMemSize)
+	stateSourceObject.LoadValue(8, new(buffer.VectorisedView), func(y interface{}) { s.loadData(y.(buffer.VectorisedView)) })
+	stateSourceObject.LoadValue(17, new([]byte), func(y interface{}) { s.loadOptions(y.([]byte)) })
+	stateSourceObject.LoadValue(19, new(unixTime), func(y interface{}) { s.loadRcvdTime(y.(unixTime)) })
+	stateSourceObject.LoadValue(20, new(unixTime), func(y interface{}) { s.loadXmitTime(y.(unixTime)) })
 }
 
 func (q *segmentQueue) StateTypeName() string {
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 5d87f3a7e..520a0ac9d 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -417,8 +417,8 @@ 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, <-chan struct{}, *tcpip.Error) {
-	n, ch, err := e.write(p, opts)
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
+	n, err := e.write(p, opts)
 	switch err {
 	case nil:
 		e.stats.PacketsSent.Increment()
@@ -428,8 +428,6 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		e.stats.WriteErrors.WriteClosed.Increment()
 	case tcpip.ErrInvalidEndpointState:
 		e.stats.WriteErrors.InvalidEndpointState.Increment()
-	case tcpip.ErrNoLinkAddress:
-		e.stats.SendErrors.NoLinkAddr.Increment()
 	case tcpip.ErrNoRoute, tcpip.ErrBroadcastDisabled, tcpip.ErrNetworkUnreachable:
 		// Errors indicating any problem with IP routing of the packet.
 		e.stats.SendErrors.NoRoute.Increment()
@@ -437,17 +435,17 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		// For all other errors when writing to the network layer.
 		e.stats.SendErrors.SendToNetworkFailed.Increment()
 	}
-	return n, ch, err
+	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *tcpip.Error) {
+func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
 	if err := e.LastError(); err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 
 	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
 	if opts.More {
-		return 0, nil, tcpip.ErrInvalidOptionValue
+		return 0, tcpip.ErrInvalidOptionValue
 	}
 
 	to := opts.To
@@ -463,14 +461,14 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 
 	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
 	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-		return 0, nil, tcpip.ErrClosedForSend
+		return 0, tcpip.ErrClosedForSend
 	}
 
 	// Prepare for write.
 	for {
 		retry, err := e.prepareForWrite(to)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 
 		if !retry {
@@ -486,7 +484,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		nicID := to.NIC
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
-				return 0, nil, tcpip.ErrNoRoute
+				return 0, tcpip.ErrNoRoute
 			}
 
 			nicID = e.BindNICID
@@ -494,17 +492,17 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 
 		if to.Port == 0 {
 			// Port 0 is an invalid port to send to.
-			return 0, nil, tcpip.ErrInvalidEndpointState
+			return 0, tcpip.ErrInvalidEndpointState
 		}
 
 		dst, netProto, err := e.checkV4MappedLocked(*to)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 
 		r, _, err := e.connectRoute(nicID, dst, netProto)
 		if err != nil {
-			return 0, nil, err
+			return 0, err
 		}
 		defer r.Release()
 
@@ -513,21 +511,12 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	}
 
 	if !e.ops.GetBroadcast() && route.IsOutboundBroadcast() {
-		return 0, nil, tcpip.ErrBroadcastDisabled
-	}
-
-	if route.IsResolutionRequired() {
-		if ch, err := route.Resolve(nil); err != nil {
-			if err == tcpip.ErrWouldBlock {
-				return 0, ch, tcpip.ErrNoLinkAddress
-			}
-			return 0, nil, err
-		}
+		return 0, tcpip.ErrBroadcastDisabled
 	}
 
 	v, err := p.FullPayload()
 	if err != nil {
-		return 0, nil, err
+		return 0, err
 	}
 	if len(v) > header.UDPMaximumPacketSize {
 		// Payload can't possibly fit in a packet.
@@ -545,7 +534,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 				v,
 			)
 		}
-		return 0, nil, tcpip.ErrMessageTooLong
+		return 0, tcpip.ErrMessageTooLong
 	}
 
 	ttl := e.ttl
@@ -575,9 +564,9 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	// See: https://golang.org/pkg/sync/#RWMutex for details on why recursive read
 	// locking is prohibited.
 	if err := sendUDP(route, buffer.View(v).ToVectorisedView(), localPort, dstPort, ttl, useDefaultTTL, sendTOS, owner, noChecksum); err != nil {
-		return 0, nil, err
+		return 0, err
 	}
-	return int64(len(v)), nil, nil
+	return int64(len(v)), nil
 }
 
 // OnReuseAddressSet implements tcpip.SocketOptionsHandler.OnReuseAddressSet.
diff --git a/pkg/tcpip/transport/udp/forwarder.go b/pkg/tcpip/transport/udp/forwarder.go
index d7fc21f11..49e673d58 100644
--- a/pkg/tcpip/transport/udp/forwarder.go
+++ b/pkg/tcpip/transport/udp/forwarder.go
@@ -75,7 +75,6 @@ func (r *ForwarderRequest) CreateEndpoint(queue *waiter.Queue) (tcpip.Endpoint,
 	if err != nil {
 		return nil, err
 	}
-	route.ResolveWith(r.pkt.SourceLinkAddress())
 
 	ep := newEndpoint(r.stack, r.pkt.NetworkProtocolNumber, queue)
 	if err := r.stack.RegisterTransportEndpoint(r.pkt.NICID, []tcpip.NetworkProtocolNumber{r.pkt.NetworkProtocolNumber}, ProtocolNumber, r.id, ep, ep.portFlags, tcpip.NICID(ep.ops.GetBindToDevice())); err != nil {