Send ICMP errors when the network is unreachable

Before this change, we would silently drop packets when unable to determine a
route to the destination host. This change brings us into line with RFC 792
(IPv4) and RFC 4443 (IPv6), both of which specify that gateways should return
an ICMP error to the sender when unable to reach the destination.

Startblock:
  has LGTM from asfez
  and then
  add reviewer ghanan
PiperOrigin-RevId: 372214051

11 files changed, 593 insertions, 131 deletions

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 264f8d926..60ef33360 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -199,6 +199,13 @@ var Metrics = tcpip.Stats{
 		OptionRecordRouteReceived:           mustCreateMetric("/netstack/ip/options/record_route_received", "Number of record route options found in received IP packets."),
 		OptionRouterAlertReceived:           mustCreateMetric("/netstack/ip/options/router_alert_received", "Number of router alert options found in received IP packets."),
 		OptionUnknownReceived:               mustCreateMetric("/netstack/ip/options/unknown_received", "Number of unknown options found in received IP packets."),
+		Forwarding: tcpip.IPForwardingStats{
+			Unrouteable:          mustCreateMetric("/netstack/ip/forwarding/unrouteable", "Number of IP packets received which couldn't be routed and thus were not forwarded."),
+			ExhaustedTTL:         mustCreateMetric("/netstack/ip/forwarding/exhausted_ttl", "Number of IP packets received which could not be forwarded due to an exhausted TTL."),
+			LinkLocalSource:      mustCreateMetric("/netstack/ip/forwarding/link_local_source_address", "Number of IP packets received which could not be forwarded due to a link-local source address."),
+			LinkLocalDestination: mustCreateMetric("/netstack/ip/forwarding/link_local_destination_address", "Number of IP packets received which could not be forwarded due to a link-local destination address."),
+			Errors:               mustCreateMetric("/netstack/ip/forwarding/errors", "Number of IP packets which couldn't be forwarded."),
+		},
 	},
 	ARP: tcpip.ARPStats{
 		PacketsReceived:                                 mustCreateMetric("/netstack/arp/packets_received", "Number of ARP packets received from the link layer."),
diff --git a/pkg/tcpip/network/internal/ip/BUILD b/pkg/tcpip/network/internal/ip/BUILD
index d21b4c7ef..fd944ce99 100644
--- a/pkg/tcpip/network/internal/ip/BUILD
+++ b/pkg/tcpip/network/internal/ip/BUILD
@@ -6,6 +6,7 @@ go_library(
     name = "ip",
     srcs = [
         "duplicate_address_detection.go",
+        "errors.go",
         "generic_multicast_protocol.go",
         "stats.go",
     ],
diff --git a/pkg/tcpip/network/internal/ip/errors.go b/pkg/tcpip/network/internal/ip/errors.go
new file mode 100644
index 000000000..50fabfd79
--- /dev/null
+++ b/pkg/tcpip/network/internal/ip/errors.go
@@ -0,0 +1,77 @@
+// 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 ip
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
+// ForwardingError represents an error that occured while trying to forward
+// a packet.
+type ForwardingError interface {
+	isForwardingError()
+	fmt.Stringer
+}
+
+// ErrTTLExceeded indicates that the received packet's TTL has been exceeded.
+type ErrTTLExceeded struct{}
+
+func (*ErrTTLExceeded) isForwardingError() {}
+
+func (*ErrTTLExceeded) String() string { return "ttl exceeded" }
+
+// ErrIPOptProblem indicates the received packet had a problem with an IP
+// option.
+type ErrIPOptProblem struct{}
+
+func (*ErrIPOptProblem) isForwardingError() {}
+
+func (*ErrIPOptProblem) String() string { return "ip option problem" }
+
+// ErrLinkLocalSourceAddress indicates the received packet had a link-local
+// source address.
+type ErrLinkLocalSourceAddress struct{}
+
+func (*ErrLinkLocalSourceAddress) isForwardingError() {}
+
+func (*ErrLinkLocalSourceAddress) String() string { return "link local destination address" }
+
+// ErrLinkLocalDestinationAddress indicates the received packet had a link-local
+// destination address.
+type ErrLinkLocalDestinationAddress struct{}
+
+func (*ErrLinkLocalDestinationAddress) isForwardingError() {}
+
+func (*ErrLinkLocalDestinationAddress) String() string { return "link local destination address" }
+
+// ErrNoRoute indicates the Netstack couldn't find a route for the
+// received packet.
+type ErrNoRoute struct{}
+
+func (*ErrNoRoute) isForwardingError() {}
+
+func (*ErrNoRoute) String() string { return "no route" }
+
+// ErrOther indicates the packet coould not be forwarded for a reason
+// captured by the contained error.
+type ErrOther struct {
+	Err tcpip.Error
+}
+
+func (*ErrOther) isForwardingError() {}
+
+func (e *ErrOther) String() string { return fmt.Sprintf("other tcpip error: %s", e.Err) }
diff --git a/pkg/tcpip/network/internal/ip/stats.go b/pkg/tcpip/network/internal/ip/stats.go
index d06b26309..392f0b0c7 100644
--- a/pkg/tcpip/network/internal/ip/stats.go
+++ b/pkg/tcpip/network/internal/ip/stats.go
@@ -18,73 +18,114 @@ import "gvisor.dev/gvisor/pkg/tcpip"
 
 // LINT.IfChange(MultiCounterIPStats)
 
+// MultiCounterIPForwardingStats holds IP forwarding statistics. Each counter
+// may have several versions.
+type MultiCounterIPForwardingStats struct {
+	// Unrouteable is the number of IP packets received which were dropped
+	// because the netstack could not construct a route to their
+	// destination.
+	Unrouteable tcpip.MultiCounterStat
+
+	// ExhaustedTTL is the number of IP packets received which were dropped
+	// because their TTL was exhausted.
+	ExhaustedTTL tcpip.MultiCounterStat
+
+	// LinkLocalSource is the number of IP packets which were dropped
+	// because they contained a link-local source address.
+	LinkLocalSource tcpip.MultiCounterStat
+
+	// LinkLocalDestination is the number of IP packets which were dropped
+	// because they contained a link-local destination address.
+	LinkLocalDestination tcpip.MultiCounterStat
+
+	// Errors is the number of IP packets received which could not be
+	// successfully forwarded.
+	Errors tcpip.MultiCounterStat
+}
+
 // MultiCounterIPStats holds IP statistics, each counter may have several
 // versions.
 type MultiCounterIPStats struct {
-	// PacketsReceived is the number of IP packets received from the link layer.
+	// PacketsReceived is the number of IP packets received from the link
+	// layer.
 	PacketsReceived tcpip.MultiCounterStat
 
-	// DisabledPacketsReceived is the number of IP packets received from the link
-	// layer when the IP layer is disabled.
+	// DisabledPacketsReceived is the number of IP packets received from
+	// the link layer when the IP layer is disabled.
 	DisabledPacketsReceived tcpip.MultiCounterStat
 
-	// InvalidDestinationAddressesReceived is the number of IP packets received
-	// with an unknown or invalid destination address.
+	// InvalidDestinationAddressesReceived is the number of IP packets
+	// received with an unknown or invalid destination address.
 	InvalidDestinationAddressesReceived tcpip.MultiCounterStat
 
-	// InvalidSourceAddressesReceived is the number of IP packets received with a
-	// source address that should never have been received on the wire.
+	// InvalidSourceAddressesReceived is the number of IP packets received
+	// with a source address that should never have been received on the
+	// wire.
 	InvalidSourceAddressesReceived tcpip.MultiCounterStat
 
-	// PacketsDelivered is the number of incoming IP packets that are successfully
-	// delivered to the transport layer.
+	// PacketsDelivered is the number of incoming IP packets that are
+	// successfully delivered to the transport layer.
 	PacketsDelivered tcpip.MultiCounterStat
 
 	// PacketsSent is the number of IP packets sent via WritePacket.
 	PacketsSent tcpip.MultiCounterStat
 
-	// OutgoingPacketErrors is the number of IP packets which failed to write to a
-	// link-layer endpoint.
+	// OutgoingPacketErrors is the number of IP packets which failed to
+	// write to a link-layer endpoint.
 	OutgoingPacketErrors tcpip.MultiCounterStat
 
-	// MalformedPacketsReceived is the number of IP Packets that were dropped due
-	// to the IP packet header failing validation checks.
+	// MalformedPacketsReceived is the number of IP Packets that were
+	// dropped due to the IP packet header failing validation checks.
 	MalformedPacketsReceived tcpip.MultiCounterStat
 
-	// MalformedFragmentsReceived is the number of IP Fragments that were dropped
-	// due to the fragment failing validation checks.
+	// MalformedFragmentsReceived is the number of IP Fragments that were
+	// dropped due to the fragment failing validation checks.
 	MalformedFragmentsReceived tcpip.MultiCounterStat
 
 	// IPTablesPreroutingDropped is the number of IP packets dropped in the
 	// Prerouting chain.
 	IPTablesPreroutingDropped tcpip.MultiCounterStat
 
-	// IPTablesInputDropped is the number of IP packets dropped in the Input
-	// chain.
+	// IPTablesInputDropped is the number of IP packets dropped in the
+	// Input chain.
 	IPTablesInputDropped tcpip.MultiCounterStat
 
-	// IPTablesOutputDropped is the number of IP packets dropped in the Output
-	// chain.
+	// IPTablesOutputDropped is the number of IP packets dropped in the
+	// Output chain.
 	IPTablesOutputDropped tcpip.MultiCounterStat
 
-	// IPTablesPostroutingDropped is the number of IP packets dropped in the
-	// Postrouting chain.
+	// IPTablesPostroutingDropped is the number of IP packets dropped in
+	// the Postrouting chain.
 	IPTablesPostroutingDropped tcpip.MultiCounterStat
 
-	// TODO(https://gvisor.dev/issues/5529): Move the IPv4-only option stats out
-	// of IPStats.
+	// TODO(https://gvisor.dev/issues/5529): Move the IPv4-only option
+	// stats out of IPStats.
 
 	// OptionTimestampReceived is the number of Timestamp options seen.
 	OptionTimestampReceived tcpip.MultiCounterStat
 
-	// OptionRecordRouteReceived is the number of Record Route options seen.
+	// OptionRecordRouteReceived is the number of Record Route options
+	// seen.
 	OptionRecordRouteReceived tcpip.MultiCounterStat
 
-	// OptionRouterAlertReceived is the number of Router Alert options seen.
+	// OptionRouterAlertReceived is the number of Router Alert options
+	// seen.
 	OptionRouterAlertReceived tcpip.MultiCounterStat
 
 	// OptionUnknownReceived is the number of unknown IP options seen.
 	OptionUnknownReceived tcpip.MultiCounterStat
+
+	// Forwarding collects stats related to IP forwarding.
+	Forwarding MultiCounterIPForwardingStats
+}
+
+// Init sets internal counters to track a and b counters.
+func (m *MultiCounterIPForwardingStats) Init(a, b *tcpip.IPForwardingStats) {
+	m.Unrouteable.Init(a.Unrouteable, b.Unrouteable)
+	m.Errors.Init(a.Errors, b.Errors)
+	m.LinkLocalSource.Init(a.LinkLocalSource, b.LinkLocalSource)
+	m.LinkLocalDestination.Init(a.LinkLocalDestination, b.LinkLocalDestination)
+	m.ExhaustedTTL.Init(a.ExhaustedTTL, b.ExhaustedTTL)
 }
 
 // Init sets internal counters to track a and b counters.
@@ -106,6 +147,7 @@ func (m *MultiCounterIPStats) Init(a, b *tcpip.IPStats) {
 	m.OptionRecordRouteReceived.Init(a.OptionRecordRouteReceived, b.OptionRecordRouteReceived)
 	m.OptionRouterAlertReceived.Init(a.OptionRouterAlertReceived, b.OptionRouterAlertReceived)
 	m.OptionUnknownReceived.Init(a.OptionUnknownReceived, b.OptionUnknownReceived)
+	m.Forwarding.Init(&a.Forwarding, &b.Forwarding)
 }
 
 // LINT.ThenChange(:MultiCounterIPStats, ../../../tcpip.go:IPStats)
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index 3f2093f00..c8ed1ce79 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -446,6 +446,23 @@ func (r *icmpReasonParamProblem) isForwarding() bool {
 	return r.forwarding
 }
 
+// icmpReasonNetworkUnreachable is an error in which the network specified in
+// the internet destination field of the datagram is unreachable.
+type icmpReasonNetworkUnreachable struct{}
+
+func (*icmpReasonNetworkUnreachable) isICMPReason() {}
+func (*icmpReasonNetworkUnreachable) isForwarding() bool {
+	// If we hit a Net Unreachable error, then we know we are operating as
+	// a router. As per RFC 792 page 5, Destination Unreachable Message,
+	//
+	//  If, according to the information in the gateway's routing tables,
+	//  the network specified in the internet destination field of a
+	//  datagram is unreachable, e.g., the distance to the network is
+	//  infinity, the gateway may send a destination unreachable message to
+	//  the internet source host of the datagram.
+	return true
+}
+
 // returnError takes an error descriptor and generates the appropriate ICMP
 // error packet for IPv4 and sends it back to the remote device that sent
 // the problematic packet. It incorporates as much of that packet as
@@ -614,6 +631,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 		icmpHdr.SetType(header.ICMPv4DstUnreachable)
 		icmpHdr.SetCode(header.ICMPv4ProtoUnreachable)
 		counter = sent.dstUnreachable
+	case *icmpReasonNetworkUnreachable:
+		icmpHdr.SetType(header.ICMPv4DstUnreachable)
+		icmpHdr.SetCode(header.ICMPv4NetUnreachable)
+		counter = sent.dstUnreachable
 	case *icmpReasonTTLExceeded:
 		icmpHdr.SetType(header.ICMPv4TimeExceeded)
 		icmpHdr.SetCode(header.ICMPv4TTLExceeded)
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index a0bc06465..b11e56c6a 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -29,6 +29,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/header/parse"
 	"gvisor.dev/gvisor/pkg/tcpip/network/hash"
 	"gvisor.dev/gvisor/pkg/tcpip/network/internal/fragmentation"
+	"gvisor.dev/gvisor/pkg/tcpip/network/internal/ip"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -599,22 +600,25 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 }
 
 // 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) ip.ForwardingError {
 	h := header.IPv4(pkt.NetworkHeader().View())
 
 	dstAddr := h.DestinationAddress()
-	if header.IsV4LinkLocalUnicastAddress(h.SourceAddress()) || header.IsV4LinkLocalUnicastAddress(dstAddr) || header.IsV4LinkLocalMulticastAddress(dstAddr) {
-		// As per RFC 3927 section 7,
-		//
-		//   A router MUST NOT forward a packet with an IPv4 Link-Local source or
-		//   destination address, irrespective of the router's default route
-		//   configuration or routes obtained from dynamic routing protocols.
-		//
-		//   A router which receives a packet with an IPv4 Link-Local source or
-		//   destination address MUST NOT forward the packet.  This prevents
-		//   forwarding of packets back onto the network segment from which they
-		//   originated, or to any other segment.
-		return nil
+	// As per RFC 3927 section 7,
+	//
+	//   A router MUST NOT forward a packet with an IPv4 Link-Local source or
+	//   destination address, irrespective of the router's default route
+	//   configuration or routes obtained from dynamic routing protocols.
+	//
+	//   A router which receives a packet with an IPv4 Link-Local source or
+	//   destination address MUST NOT forward the packet.  This prevents
+	//   forwarding of packets back onto the network segment from which they
+	//   originated, or to any other segment.
+	if header.IsV4LinkLocalUnicastAddress(h.SourceAddress()) {
+		return &ip.ErrLinkLocalSourceAddress{}
+	}
+	if header.IsV4LinkLocalUnicastAddress(dstAddr) || header.IsV4LinkLocalMulticastAddress(dstAddr) {
+		return &ip.ErrLinkLocalDestinationAddress{}
 	}
 
 	ttl := h.TTL()
@@ -624,7 +628,12 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 		//  If the gateway processing a datagram finds the time to live field
 		//  is zero it must discard the datagram.  The gateway may also notify
 		//  the source host via the time exceeded message.
-		return e.protocol.returnError(&icmpReasonTTLExceeded{}, pkt)
+		//
+		// We return the original error rather than the result of returning
+		// the ICMP packet because the original error is more relevant to
+		// the caller.
+		_ = e.protocol.returnError(&icmpReasonTTLExceeded{}, pkt)
+		return &ip.ErrTTLExceeded{}
 	}
 
 	if opts := h.Options(); len(opts) != 0 {
@@ -635,10 +644,8 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 					pointer:    optProblem.Pointer,
 					forwarding: true,
 				}, pkt)
-				e.protocol.stack.Stats().MalformedRcvdPackets.Increment()
-				e.stats.ip.MalformedPacketsReceived.Increment()
 			}
-			return nil // option problems are not reported locally.
+			return &ip.ErrIPOptProblem{}
 		}
 		copied := copy(opts, newOpts)
 		if copied != len(newOpts) {
@@ -662,8 +669,16 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	}
 
 	r, err := e.protocol.stack.FindRoute(0, "", dstAddr, ProtocolNumber, false /* multicastLoop */)
-	if err != nil {
-		return err
+	switch err.(type) {
+	case nil:
+	case *tcpip.ErrNoRoute, *tcpip.ErrNetworkUnreachable:
+		// We return the original error rather than the result of returning
+		// the ICMP packet because the original error is more relevant to
+		// the caller.
+		_ = e.protocol.returnError(&icmpReasonNetworkUnreachable{}, pkt)
+		return &ip.ErrNoRoute{}
+	default:
+		return &ip.ErrOther{Err: err}
 	}
 	defer r.Release()
 
@@ -680,10 +695,13 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	//   spent, the field must be decremented by 1.
 	newHdr.SetTTL(ttl - 1)
 
-	return r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
+	if err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               buffer.View(newHdr).ToVectorisedView(),
-	}))
+	})); err != nil {
+		return &ip.ErrOther{Err: err}
+	}
+	return nil
 }
 
 // HandlePacket is called by the link layer when new ipv4 packets arrive for
@@ -798,7 +816,24 @@ func (e *endpoint) handleValidatedPacket(h header.IPv4, pkt *stack.PacketBuffer)
 			stats.ip.InvalidDestinationAddressesReceived.Increment()
 			return
 		}
-		_ = e.forwardPacket(pkt)
+		switch err := e.forwardPacket(pkt); err.(type) {
+		case nil:
+			return
+		case *ip.ErrLinkLocalSourceAddress:
+			stats.ip.Forwarding.LinkLocalSource.Increment()
+		case *ip.ErrLinkLocalDestinationAddress:
+			stats.ip.Forwarding.LinkLocalDestination.Increment()
+		case *ip.ErrTTLExceeded:
+			stats.ip.Forwarding.ExhaustedTTL.Increment()
+		case *ip.ErrNoRoute:
+			stats.ip.Forwarding.Unrouteable.Increment()
+		case *ip.ErrIPOptProblem:
+			e.protocol.stack.Stats().MalformedRcvdPackets.Increment()
+			stats.ip.MalformedPacketsReceived.Increment()
+		default:
+			panic(fmt.Sprintf("unexpected error %s while trying to forward packet: %#v", err, pkt))
+		}
+		stats.ip.Forwarding.Errors.Increment()
 		return
 	}
 
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index 7d413c455..7a7cad04a 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -131,48 +131,69 @@ func TestForwarding(t *testing.T) {
 	}
 	remoteIPv4Addr1 := tcpip.Address(net.ParseIP("10.0.0.2").To4())
 	remoteIPv4Addr2 := tcpip.Address(net.ParseIP("11.0.0.2").To4())
+	unreachableIPv4Addr := tcpip.Address(net.ParseIP("12.0.0.2").To4())
+	multicastIPv4Addr := tcpip.Address(net.ParseIP("225.0.0.0").To4())
+	linkLocalIPv4Addr := tcpip.Address(net.ParseIP("169.254.0.0").To4())
 
 	tests := []struct {
-		name             string
-		TTL              uint8
-		expectErrorICMP  bool
-		options          header.IPv4Options
-		forwardedOptions header.IPv4Options
-		icmpType         header.ICMPv4Type
-		icmpCode         header.ICMPv4Code
+		name                         string
+		TTL                          uint8
+		sourceAddr                   tcpip.Address
+		destAddr                     tcpip.Address
+		expectErrorICMP              bool
+		expectPacketForwarded        bool
+		options                      header.IPv4Options
+		forwardedOptions             header.IPv4Options
+		icmpType                     header.ICMPv4Type
+		icmpCode                     header.ICMPv4Code
+		expectPacketUnrouteableError bool
+		expectLinkLocalSourceError   bool
+		expectLinkLocalDestError     bool
 	}{
 		{
 			name:            "TTL of zero",
 			TTL:             0,
+			sourceAddr:      remoteIPv4Addr1,
+			destAddr:        remoteIPv4Addr2,
 			expectErrorICMP: true,
 			icmpType:        header.ICMPv4TimeExceeded,
 			icmpCode:        header.ICMPv4TTLExceeded,
 		},
 		{
-			name:            "TTL of one",
-			TTL:             1,
-			expectErrorICMP: false,
+			name:                  "TTL of one",
+			TTL:                   1,
+			sourceAddr:            remoteIPv4Addr1,
+			destAddr:              remoteIPv4Addr2,
+			expectPacketForwarded: true,
 		},
 		{
-			name:            "TTL of two",
-			TTL:             2,
-			expectErrorICMP: false,
+			name:                  "TTL of two",
+			TTL:                   2,
+			sourceAddr:            remoteIPv4Addr1,
+			destAddr:              remoteIPv4Addr2,
+			expectPacketForwarded: true,
 		},
 		{
-			name:            "Max TTL",
-			TTL:             math.MaxUint8,
-			expectErrorICMP: false,
+			name:                  "Max TTL",
+			TTL:                   math.MaxUint8,
+			sourceAddr:            remoteIPv4Addr1,
+			destAddr:              remoteIPv4Addr2,
+			expectPacketForwarded: true,
 		},
 		{
-			name:             "four EOL options",
-			TTL:              2,
-			expectErrorICMP:  false,
-			options:          header.IPv4Options{0, 0, 0, 0},
-			forwardedOptions: header.IPv4Options{0, 0, 0, 0},
+			name:                  "four EOL options",
+			TTL:                   2,
+			sourceAddr:            remoteIPv4Addr1,
+			destAddr:              remoteIPv4Addr2,
+			expectPacketForwarded: true,
+			options:               header.IPv4Options{0, 0, 0, 0},
+			forwardedOptions:      header.IPv4Options{0, 0, 0, 0},
 		},
 		{
-			name: "TS type 1 full",
-			TTL:  2,
+			name:       "TS type 1 full",
+			TTL:        2,
+			sourceAddr: remoteIPv4Addr1,
+			destAddr:   remoteIPv4Addr2,
 			options: header.IPv4Options{
 				68, 12, 13, 0xF1,
 				192, 168, 1, 12,
@@ -183,8 +204,10 @@ func TestForwarding(t *testing.T) {
 			icmpCode:        header.ICMPv4UnusedCode,
 		},
 		{
-			name: "TS type 0",
-			TTL:  2,
+			name:       "TS type 0",
+			TTL:        2,
+			sourceAddr: remoteIPv4Addr1,
+			destAddr:   remoteIPv4Addr2,
 			options: header.IPv4Options{
 				68, 24, 21, 0x00,
 				1, 2, 3, 4,
@@ -201,10 +224,13 @@ func TestForwarding(t *testing.T) {
 				13, 14, 15, 16,
 				0x00, 0xad, 0x1c, 0x40, // time we expect from fakeclock
 			},
+			expectPacketForwarded: true,
 		},
 		{
-			name: "end of options list",
-			TTL:  2,
+			name:       "end of options list",
+			TTL:        2,
+			sourceAddr: remoteIPv4Addr1,
+			destAddr:   remoteIPv4Addr2,
 			options: header.IPv4Options{
 				68, 12, 13, 0x11,
 				192, 168, 1, 12,
@@ -220,6 +246,37 @@ func TestForwarding(t *testing.T) {
 				0, 0, 0, // 7 bytes unknown option removed.
 				0, 0, 0, 0,
 			},
+			expectPacketForwarded: true,
+		},
+		{
+			name:                         "Network unreachable",
+			TTL:                          2,
+			sourceAddr:                   remoteIPv4Addr1,
+			destAddr:                     unreachableIPv4Addr,
+			expectErrorICMP:              true,
+			icmpType:                     header.ICMPv4DstUnreachable,
+			icmpCode:                     header.ICMPv4NetUnreachable,
+			expectPacketUnrouteableError: true,
+		},
+		{
+			name:                         "Multicast destination",
+			TTL:                          2,
+			destAddr:                     multicastIPv4Addr,
+			expectPacketUnrouteableError: true,
+		},
+		{
+			name:                     "Link local destination",
+			TTL:                      2,
+			sourceAddr:               remoteIPv4Addr1,
+			destAddr:                 linkLocalIPv4Addr,
+			expectLinkLocalDestError: true,
+		},
+		{
+			name:                       "Link local source",
+			TTL:                        2,
+			sourceAddr:                 linkLocalIPv4Addr,
+			destAddr:                   remoteIPv4Addr2,
+			expectLinkLocalSourceError: true,
 		},
 	}
 	for _, test := range tests {
@@ -287,8 +344,8 @@ func TestForwarding(t *testing.T) {
 				TotalLength: totalLen,
 				Protocol:    uint8(header.ICMPv4ProtocolNumber),
 				TTL:         test.TTL,
-				SrcAddr:     remoteIPv4Addr1,
-				DstAddr:     remoteIPv4Addr2,
+				SrcAddr:     test.sourceAddr,
+				DstAddr:     test.destAddr,
 			})
 			if len(test.options) != 0 {
 				ip.SetHeaderLength(uint8(ipHeaderLength))
@@ -305,15 +362,15 @@ func TestForwarding(t *testing.T) {
 			})
 			e1.InjectInbound(header.IPv4ProtocolNumber, requestPkt)
 
+			reply, ok := e1.Read()
 			if test.expectErrorICMP {
-				reply, ok := e1.Read()
 				if !ok {
 					t.Fatalf("expected ICMP packet type %d through incoming NIC", test.icmpType)
 				}
 
 				checker.IPv4(t, header.IPv4(stack.PayloadSince(reply.Pkt.NetworkHeader())),
 					checker.SrcAddr(ipv4Addr1.Address),
-					checker.DstAddr(remoteIPv4Addr1),
+					checker.DstAddr(test.sourceAddr),
 					checker.TTL(ipv4.DefaultTTL),
 					checker.ICMPv4(
 						checker.ICMPv4Checksum(),
@@ -326,15 +383,19 @@ func TestForwarding(t *testing.T) {
 				if n := e2.Drain(); n != 0 {
 					t.Fatalf("got e2.Drain() = %d, want = 0", n)
 				}
-			} else {
-				reply, ok := e2.Read()
+			} else if ok {
+				t.Fatalf("expected no ICMP packet through incoming NIC, instead found: %#v", reply)
+			}
+
+			reply, ok = e2.Read()
+			if test.expectPacketForwarded {
 				if !ok {
 					t.Fatal("expected ICMP Echo packet through outgoing NIC")
 				}
 
 				checker.IPv4(t, header.IPv4(stack.PayloadSince(reply.Pkt.NetworkHeader())),
-					checker.SrcAddr(remoteIPv4Addr1),
-					checker.DstAddr(remoteIPv4Addr2),
+					checker.SrcAddr(test.sourceAddr),
+					checker.DstAddr(test.destAddr),
 					checker.TTL(test.TTL-1),
 					checker.IPv4Options(test.forwardedOptions),
 					checker.ICMPv4(
@@ -348,6 +409,39 @@ func TestForwarding(t *testing.T) {
 				if n := e1.Drain(); n != 0 {
 					t.Fatalf("got e1.Drain() = %d, want = 0", n)
 				}
+			} else if ok {
+				t.Fatalf("expected no ICMP Echo packet through outgoing NIC, instead found: %#v", reply)
+			}
+
+			boolToInt := func(val bool) uint64 {
+				if val {
+					return 1
+				}
+				return 0
+			}
+
+			if got, want := s.Stats().IP.Forwarding.LinkLocalSource.Value(), boolToInt(test.expectLinkLocalSourceError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.LinkLocalSource.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.LinkLocalDestination.Value(), boolToInt(test.expectLinkLocalDestError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.LinkLocalDestination.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.MalformedPacketsReceived.Value(), boolToInt(test.icmpType == header.ICMPv4ParamProblem); got != want {
+				t.Errorf("got s.Stats().IP.MalformedPacketsReceived.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.ExhaustedTTL.Value(), boolToInt(test.TTL <= 0); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.ExhaustedTTL.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.Unrouteable.Value(), boolToInt(test.expectPacketUnrouteableError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.Unrouteable.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.Errors.Value(), boolToInt(!test.expectPacketForwarded); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.Errors.Value() = %d, want = %d", got, want)
 			}
 		})
 	}
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 28bb61a08..ebb0b73df 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -955,6 +955,7 @@ func (*endpoint) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bo
 // icmpReason is a marker interface for IPv6 specific ICMP errors.
 type icmpReason interface {
 	isICMPReason()
+	isForwarding() bool
 }
 
 // icmpReasonParameterProblem is an error during processing of extension headers
@@ -986,6 +987,9 @@ type icmpReasonParameterProblem struct {
 }
 
 func (*icmpReasonParameterProblem) isICMPReason() {}
+func (*icmpReasonParameterProblem) isForwarding() bool {
+	return false
+}
 
 // icmpReasonPortUnreachable is an error where the transport protocol has no
 // listener and no alternative means to inform the sender.
@@ -993,12 +997,44 @@ type icmpReasonPortUnreachable struct{}
 
 func (*icmpReasonPortUnreachable) isICMPReason() {}
 
+func (*icmpReasonPortUnreachable) isForwarding() bool {
+	return false
+}
+
+// icmpReasonNetUnreachable is an error where no route can be found to the
+// network of the final destination.
+type icmpReasonNetUnreachable struct{}
+
+func (*icmpReasonNetUnreachable) isICMPReason() {}
+
+func (*icmpReasonNetUnreachable) isForwarding() bool {
+	// If we hit a Network Unreachable error, then we also know we are
+	// operating as a router. As per RFC 4443 section 3.1:
+	//
+	//   If the reason for the failure to deliver is lack of a matching
+	//   entry in the forwarding node's routing table, the Code field is
+	//   set to 0 (Network Unreachable).
+	return true
+}
+
 // icmpReasonHopLimitExceeded is an error where a packet's hop limit exceeded in
 // transit to its final destination, as per RFC 4443 section 3.3.
 type icmpReasonHopLimitExceeded struct{}
 
 func (*icmpReasonHopLimitExceeded) isICMPReason() {}
 
+func (*icmpReasonHopLimitExceeded) isForwarding() bool {
+	// If we hit a Hop Limit Exceeded error, then we know we are operating
+	// as a router. As per RFC 4443 section 3.3:
+	//
+	//   If a router receives a packet with a Hop Limit of zero, or if a
+	//   router decrements a packet's Hop Limit to zero, it MUST discard
+	//   the packet and originate an ICMPv6 Time Exceeded message with Code
+	//   0 to the source of the packet.  This indicates either a routing
+	//   loop or too small an initial Hop Limit value.
+	return true
+}
+
 // icmpReasonReassemblyTimeout is an error where insufficient fragments are
 // received to complete reassembly of a packet within a configured time after
 // the reception of the first-arriving fragment of that packet.
@@ -1006,6 +1042,10 @@ type icmpReasonReassemblyTimeout struct{}
 
 func (*icmpReasonReassemblyTimeout) isICMPReason() {}
 
+func (*icmpReasonReassemblyTimeout) isForwarding() bool {
+	return false
+}
+
 // 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 {
@@ -1044,15 +1084,6 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 		return nil
 	}
 
-	// If we hit a Hop Limit Exceeded error, then we know we are operating as a
-	// router. As per RFC 4443 section 3.3:
-	//
-	//   If a router receives a packet with a Hop Limit of zero, or if a
-	//   router decrements a packet's Hop Limit to zero, it MUST discard the
-	//   packet and originate an ICMPv6 Time Exceeded message with Code 0 to
-	//   the source of the packet.  This indicates either a routing loop or
-	//   too small an initial Hop Limit value.
-	//
 	// If we are operating as a router, do not use the packet's destination
 	// address as the response's source address as we should not own the
 	// destination address of a packet we are forwarding.
@@ -1062,7 +1093,7 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 	// packet as "multicast addresses must not be used as source addresses in IPv6
 	// packets", as per RFC 4291 section 2.7.
 	localAddr := origIPHdrDst
-	if _, ok := reason.(*icmpReasonHopLimitExceeded); ok || isOrigDstMulticast {
+	if reason.isForwarding() || isOrigDstMulticast {
 		localAddr = ""
 	}
 	// Even if we were able to receive a packet from some remote, we may not have
@@ -1151,6 +1182,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) tcpip
 		icmpHdr.SetType(header.ICMPv6DstUnreachable)
 		icmpHdr.SetCode(header.ICMPv6PortUnreachable)
 		counter = sent.dstUnreachable
+	case *icmpReasonNetUnreachable:
+		icmpHdr.SetType(header.ICMPv6DstUnreachable)
+		icmpHdr.SetCode(header.ICMPv6NetworkUnreachable)
+		counter = sent.dstUnreachable
 	case *icmpReasonHopLimitExceeded:
 		icmpHdr.SetType(header.ICMPv6TimeExceeded)
 		icmpHdr.SetCode(header.ICMPv6HopLimitExceeded)
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 6974eae11..c7a92be6c 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -924,16 +924,19 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu
 }
 
 // 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) ip.ForwardingError {
 	h := header.IPv6(pkt.NetworkHeader().View())
 
 	dstAddr := h.DestinationAddress()
-	if header.IsV6LinkLocalUnicastAddress(h.SourceAddress()) || header.IsV6LinkLocalUnicastAddress(dstAddr) || header.IsV6LinkLocalMulticastAddress(dstAddr) {
-		// As per RFC 4291 section 2.5.6,
-		//
-		//   Routers must not forward any packets with Link-Local source or
-		//   destination addresses to other links.
-		return nil
+	// As per RFC 4291 section 2.5.6,
+	//
+	//   Routers must not forward any packets with Link-Local source or
+	//   destination addresses to other links.
+	if header.IsV6LinkLocalUnicastAddress(h.SourceAddress()) {
+		return &ip.ErrLinkLocalSourceAddress{}
+	}
+	if header.IsV6LinkLocalUnicastAddress(dstAddr) || header.IsV6LinkLocalMulticastAddress(dstAddr) {
+		return &ip.ErrLinkLocalDestinationAddress{}
 	}
 
 	hopLimit := h.HopLimit()
@@ -945,7 +948,12 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 		//   packet and originate an ICMPv6 Time Exceeded message with Code 0 to
 		//   the source of the packet.  This indicates either a routing loop or
 		//   too small an initial Hop Limit value.
-		return e.protocol.returnError(&icmpReasonHopLimitExceeded{}, pkt)
+		//
+		// We return the original error rather than the result of returning
+		// the ICMP packet because the original error is more relevant to
+		// the caller.
+		_ = e.protocol.returnError(&icmpReasonHopLimitExceeded{}, pkt)
+		return &ip.ErrTTLExceeded{}
 	}
 
 	// Check if the destination is owned by the stack.
@@ -955,8 +963,16 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	}
 
 	r, err := e.protocol.stack.FindRoute(0, "", dstAddr, ProtocolNumber, false /* multicastLoop */)
-	if err != nil {
-		return err
+	switch err.(type) {
+	case nil:
+	case *tcpip.ErrNoRoute, *tcpip.ErrNetworkUnreachable:
+		// We return the original error rather than the result of returning
+		// the ICMP packet because the original error is more relevant to
+		// the caller.
+		_ = e.protocol.returnError(&icmpReasonNetUnreachable{}, pkt)
+		return &ip.ErrNoRoute{}
+	default:
+		return &ip.ErrOther{Err: err}
 	}
 	defer r.Release()
 
@@ -971,10 +987,13 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) tcpip.Error {
 	//                       each node that forwards the packet.
 	newHdr.SetHopLimit(hopLimit - 1)
 
-	return r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
+	if err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{
 		ReserveHeaderBytes: int(r.MaxHeaderLength()),
 		Data:               buffer.View(newHdr).ToVectorisedView(),
-	}))
+	})); err != nil {
+		return &ip.ErrOther{Err: err}
+	}
+	return nil
 }
 
 // HandlePacket is called by the link layer when new ipv6 packets arrive for
@@ -1075,8 +1094,21 @@ func (e *endpoint) handleValidatedPacket(h header.IPv6, pkt *stack.PacketBuffer)
 			stats.InvalidDestinationAddressesReceived.Increment()
 			return
 		}
-
-		_ = e.forwardPacket(pkt)
+		switch err := e.forwardPacket(pkt); err.(type) {
+		case nil:
+			return
+		case *ip.ErrLinkLocalSourceAddress:
+			e.stats.ip.Forwarding.LinkLocalSource.Increment()
+		case *ip.ErrLinkLocalDestinationAddress:
+			e.stats.ip.Forwarding.LinkLocalDestination.Increment()
+		case *ip.ErrTTLExceeded:
+			e.stats.ip.Forwarding.ExhaustedTTL.Increment()
+		case *ip.ErrNoRoute:
+			e.stats.ip.Forwarding.Unrouteable.Increment()
+		default:
+			panic(fmt.Sprintf("unexpected error %s while trying to forward packet: %#v", err, pkt))
+		}
+		e.stats.ip.Forwarding.Errors.Increment()
 		return
 	}
 
diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go
index 40a793d6b..4fbe39528 100644
--- a/pkg/tcpip/network/ipv6/ipv6_test.go
+++ b/pkg/tcpip/network/ipv6/ipv6_test.go
@@ -3019,36 +3019,94 @@ func TestForwarding(t *testing.T) {
 	}
 	remoteIPv6Addr1 := tcpip.Address(net.ParseIP("10::2").To16())
 	remoteIPv6Addr2 := tcpip.Address(net.ParseIP("11::2").To16())
+	unreachableIPv6Addr := tcpip.Address(net.ParseIP("12::2").To16())
+	multicastIPv6Addr := tcpip.Address(net.ParseIP("ff00::").To16())
+	linkLocalIPv6Addr := tcpip.Address(net.ParseIP("fe80::").To16())
 
 	tests := []struct {
-		name            string
-		TTL             uint8
-		expectErrorICMP bool
+		name                         string
+		TTL                          uint8
+		expectErrorICMP              bool
+		expectPacketForwarded        bool
+		countUnrouteablePackets      uint64
+		sourceAddr                   tcpip.Address
+		destAddr                     tcpip.Address
+		icmpType                     header.ICMPv6Type
+		icmpCode                     header.ICMPv6Code
+		expectPacketUnrouteableError bool
+		expectLinkLocalSourceError   bool
+		expectLinkLocalDestError     bool
 	}{
 		{
 			name:            "TTL of zero",
 			TTL:             0,
 			expectErrorICMP: true,
+			sourceAddr:      remoteIPv6Addr1,
+			destAddr:        remoteIPv6Addr2,
+			icmpType:        header.ICMPv6TimeExceeded,
+			icmpCode:        header.ICMPv6HopLimitExceeded,
 		},
 		{
 			name:            "TTL of one",
 			TTL:             1,
 			expectErrorICMP: true,
+			sourceAddr:      remoteIPv6Addr1,
+			destAddr:        remoteIPv6Addr2,
+			icmpType:        header.ICMPv6TimeExceeded,
+			icmpCode:        header.ICMPv6HopLimitExceeded,
+		},
+		{
+			name:                  "TTL of two",
+			TTL:                   2,
+			expectPacketForwarded: true,
+			sourceAddr:            remoteIPv6Addr1,
+			destAddr:              remoteIPv6Addr2,
+		},
+		{
+			name:                  "TTL of three",
+			TTL:                   3,
+			expectPacketForwarded: true,
+			sourceAddr:            remoteIPv6Addr1,
+			destAddr:              remoteIPv6Addr2,
+		},
+		{
+			name:                  "Max TTL",
+			TTL:                   math.MaxUint8,
+			expectPacketForwarded: true,
+			sourceAddr:            remoteIPv6Addr1,
+			destAddr:              remoteIPv6Addr2,
+		},
+		{
+			name:                         "Network unreachable",
+			TTL:                          2,
+			expectErrorICMP:              true,
+			sourceAddr:                   remoteIPv6Addr1,
+			destAddr:                     unreachableIPv6Addr,
+			icmpType:                     header.ICMPv6DstUnreachable,
+			icmpCode:                     header.ICMPv6NetworkUnreachable,
+			expectPacketUnrouteableError: true,
 		},
 		{
-			name:            "TTL of two",
-			TTL:             2,
-			expectErrorICMP: false,
+			name:                         "Multicast destination",
+			TTL:                          2,
+			countUnrouteablePackets:      1,
+			sourceAddr:                   remoteIPv6Addr1,
+			destAddr:                     multicastIPv6Addr,
+			expectPacketUnrouteableError: true,
 		},
 		{
-			name:            "TTL of three",
-			TTL:             3,
-			expectErrorICMP: false,
+			name:                     "Link local destination",
+			TTL:                      2,
+			sourceAddr:               remoteIPv6Addr1,
+			destAddr:                 linkLocalIPv6Addr,
+			expectLinkLocalDestError: true,
 		},
 		{
-			name:            "Max TTL",
-			TTL:             math.MaxUint8,
-			expectErrorICMP: false,
+			name:                       "Link local source",
+			TTL:                        2,
+			sourceAddr:                 linkLocalIPv6Addr,
+			destAddr:                   remoteIPv6Addr2,
+			expectLinkLocalSourceError: true,
 		},
 	}
 
@@ -3101,35 +3159,35 @@ func TestForwarding(t *testing.T) {
 			icmp.SetChecksum(0)
 			icmp.SetChecksum(header.ICMPv6Checksum(header.ICMPv6ChecksumParams{
 				Header: icmp,
-				Src:    remoteIPv6Addr1,
-				Dst:    remoteIPv6Addr2,
+				Src:    test.sourceAddr,
+				Dst:    test.destAddr,
 			}))
 			ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
 			ip.Encode(&header.IPv6Fields{
 				PayloadLength:     header.ICMPv6MinimumSize,
 				TransportProtocol: header.ICMPv6ProtocolNumber,
 				HopLimit:          test.TTL,
-				SrcAddr:           remoteIPv6Addr1,
-				DstAddr:           remoteIPv6Addr2,
+				SrcAddr:           test.sourceAddr,
+				DstAddr:           test.destAddr,
 			})
 			requestPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 				Data: hdr.View().ToVectorisedView(),
 			})
 			e1.InjectInbound(ProtocolNumber, requestPkt)
 
+			reply, ok := e1.Read()
 			if test.expectErrorICMP {
-				reply, ok := e1.Read()
 				if !ok {
-					t.Fatal("expected ICMP Hop Limit Exceeded packet through incoming NIC")
+					t.Fatalf("expected ICMP packet type %d through incoming NIC", test.icmpType)
 				}
 
 				checker.IPv6(t, header.IPv6(stack.PayloadSince(reply.Pkt.NetworkHeader())),
 					checker.SrcAddr(ipv6Addr1.Address),
-					checker.DstAddr(remoteIPv6Addr1),
+					checker.DstAddr(test.sourceAddr),
 					checker.TTL(DefaultTTL),
 					checker.ICMPv6(
-						checker.ICMPv6Type(header.ICMPv6TimeExceeded),
-						checker.ICMPv6Code(header.ICMPv6HopLimitExceeded),
+						checker.ICMPv6Type(test.icmpType),
+						checker.ICMPv6Code(test.icmpCode),
 						checker.ICMPv6Payload([]byte(hdr.View())),
 					),
 				)
@@ -3137,15 +3195,19 @@ func TestForwarding(t *testing.T) {
 				if n := e2.Drain(); n != 0 {
 					t.Fatalf("got e2.Drain() = %d, want = 0", n)
 				}
-			} else {
-				reply, ok := e2.Read()
+			} else if ok {
+				t.Fatalf("expected no ICMP packet through incoming NIC, instead found: %#v", reply)
+			}
+
+			reply, ok = e2.Read()
+			if test.expectPacketForwarded {
 				if !ok {
 					t.Fatal("expected ICMP Echo Request packet through outgoing NIC")
 				}
 
 				checker.IPv6(t, header.IPv6(stack.PayloadSince(reply.Pkt.NetworkHeader())),
-					checker.SrcAddr(remoteIPv6Addr1),
-					checker.DstAddr(remoteIPv6Addr2),
+					checker.SrcAddr(test.sourceAddr),
+					checker.DstAddr(test.destAddr),
 					checker.TTL(test.TTL-1),
 					checker.ICMPv6(
 						checker.ICMPv6Type(header.ICMPv6EchoRequest),
@@ -3157,6 +3219,35 @@ func TestForwarding(t *testing.T) {
 				if n := e1.Drain(); n != 0 {
 					t.Fatalf("got e1.Drain() = %d, want = 0", n)
 				}
+			} else if ok {
+				t.Fatalf("expected no ICMP Echo packet through outgoing NIC, instead found: %#v", reply)
+			}
+
+			boolToInt := func(val bool) uint64 {
+				if val {
+					return 1
+				}
+				return 0
+			}
+
+			if got, want := s.Stats().IP.Forwarding.LinkLocalSource.Value(), boolToInt(test.expectLinkLocalSourceError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.LinkLocalSource.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.LinkLocalDestination.Value(), boolToInt(test.expectLinkLocalDestError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.LinkLocalDestination.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.ExhaustedTTL.Value(), boolToInt(test.TTL <= 1); got != want {
+				t.Errorf("got rt.Stats().IP.Forwarding.ExhaustedTTL.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.Unrouteable.Value(), boolToInt(test.expectPacketUnrouteableError); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.Unrouteable.Value() = %d, want = %d", got, want)
+			}
+
+			if got, want := s.Stats().IP.Forwarding.Errors.Value(), boolToInt(!test.expectPacketForwarded); got != want {
+				t.Errorf("got s.Stats().IP.Forwarding.Errors.Value() = %d, want = %d", got, want)
 			}
 		})
 	}
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index d8a10065d..d5f941c5f 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -1528,6 +1528,30 @@ type IGMPStats struct {
 	// LINT.ThenChange(network/ipv4/stats.go:multiCounterIGMPStats)
 }
 
+// IPForwardingStats collects stats related to IP forwarding (both v4 and v6).
+type IPForwardingStats struct {
+	// Unrouteable is the number of IP packets received which were dropped
+	// because the netstack could not construct a route to their
+	// destination.
+	Unrouteable *StatCounter
+
+	// ExhaustedTTL is the number of IP packets received which were dropped
+	// because their TTL was exhausted.
+	ExhaustedTTL *StatCounter
+
+	// LinkLocalSource is the number of IP packets which were dropped
+	// because they contained a link-local source address.
+	LinkLocalSource *StatCounter
+
+	// LinkLocalDestination is the number of IP packets which were dropped
+	// because they contained a link-local destination address.
+	LinkLocalDestination *StatCounter
+
+	// Errors is the number of IP packets received which could not be
+	// successfully forwarded.
+	Errors *StatCounter
+}
+
 // IPStats collects IP-specific stats (both v4 and v6).
 type IPStats struct {
 	// LINT.IfChange(IPStats)
@@ -1596,6 +1620,9 @@ type IPStats struct {
 	// OptionUnknownReceived is the number of unknown IP options seen.
 	OptionUnknownReceived *StatCounter
 
+	// Forwarding collects stats related to IP forwarding.
+	Forwarding IPForwardingStats
+
 	// LINT.ThenChange(network/internal/ip/stats.go:MultiCounterIPStats)
 }