tcpip/network/ipv6/icmp_test.go - third_party/netstack - Git at Google

 // Copyright 2018 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 ipv6

 import (
 	"reflect"
 	"strings"
 	"testing"

 	"github.com/google/netstack/tcpip"
 	"github.com/google/netstack/tcpip/buffer"
 	"github.com/google/netstack/tcpip/header"
 	"github.com/google/netstack/tcpip/link/channel"
 	"github.com/google/netstack/tcpip/link/sniffer"
 	"github.com/google/netstack/tcpip/stack"
 	"github.com/google/netstack/tcpip/transport/icmp"
 	"github.com/google/netstack/waiter"
 )

 const (
 	linkAddr0 = tcpip.LinkAddress("\x01\x02\x03\x04\x05\x06")
 	linkAddr1 = tcpip.LinkAddress("\x0a\x0b\x0c\x0d\x0e\x0f")
 )

 var (
 	lladdr0 = header.LinkLocalAddr(linkAddr0)
 	lladdr1 = header.LinkLocalAddr(linkAddr1)
 )

 type stubLinkEndpoint struct {
 	stack.LinkEndpoint
 }

 func (*stubLinkEndpoint) Capabilities() stack.LinkEndpointCapabilities {
 	return 0
 }

 func (*stubLinkEndpoint) MaxHeaderLength() uint16 {
 	return 0
 }

 func (*stubLinkEndpoint) LinkAddress() tcpip.LinkAddress {
 	return ""
 }

 func (*stubLinkEndpoint) WritePacket(*stack.Route, *stack.GSO, buffer.Prependable, buffer.VectorisedView, tcpip.NetworkProtocolNumber) *tcpip.Error {
 	return nil
 }

 func (*stubLinkEndpoint) Attach(stack.NetworkDispatcher) {}

 type stubDispatcher struct {
 	stack.TransportDispatcher
 }

 func (*stubDispatcher) DeliverTransportPacket(*stack.Route, tcpip.TransportProtocolNumber, buffer.View, buffer.VectorisedView) {
 }

 type stubLinkAddressCache struct {
 	stack.LinkAddressCache
 }

 func (*stubLinkAddressCache) CheckLocalAddress(tcpip.NICID, tcpip.NetworkProtocolNumber, tcpip.Address) tcpip.NICID {
 	return 0
 }

 func (*stubLinkAddressCache) AddLinkAddress(tcpip.NICID, tcpip.Address, tcpip.LinkAddress) {
 }

 func TestICMPCounts(t *testing.T) {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocol{NewProtocol()},
 		TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
 	})
 	{
 		if err := s.CreateNIC(1, &stubLinkEndpoint{}); err != nil {
 			t.Fatalf("CreateNIC(_) = %s", err)
 		}
 		if err := s.AddAddress(1, ProtocolNumber, lladdr0); err != nil {
 			t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, lladdr0, err)
 		}
 	}
 	{
 		subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
 		if err != nil {
 			t.Fatal(err)
 		}
 		s.SetRouteTable(
 			[]tcpip.Route{{
 				Destination: subnet,
 				NIC:         1,
 			}},
 		)
 	}

 	netProto := s.NetworkProtocolInstance(ProtocolNumber)
 	if netProto == nil {
 		t.Fatalf("cannot find protocol instance for network protocol %d", ProtocolNumber)
 	}
 	ep, err := netProto.NewEndpoint(0, tcpip.AddressWithPrefix{lladdr1, netProto.DefaultPrefixLen()}, &stubLinkAddressCache{}, &stubDispatcher{}, nil)
 	if err != nil {
 		t.Fatalf("NewEndpoint(_) = _, %s, want = _, nil", err)
 	}

 	r, err := s.FindRoute(1, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute(_) = _, %s, want = _, nil", err)
 	}
 	defer r.Release()

 	types := []struct {
 		typ  header.ICMPv6Type
 		size int
 	}{
 		{header.ICMPv6DstUnreachable, header.ICMPv6DstUnreachableMinimumSize},
 		{header.ICMPv6PacketTooBig, header.ICMPv6PacketTooBigMinimumSize},
 		{header.ICMPv6TimeExceeded, header.ICMPv6MinimumSize},
 		{header.ICMPv6ParamProblem, header.ICMPv6MinimumSize},
 		{header.ICMPv6EchoRequest, header.ICMPv6EchoMinimumSize},
 		{header.ICMPv6EchoReply, header.ICMPv6EchoMinimumSize},
 		{header.ICMPv6RouterSolicit, header.ICMPv6MinimumSize},
 		{header.ICMPv6RouterAdvert, header.ICMPv6MinimumSize},
 		{header.ICMPv6NeighborSolicit, header.ICMPv6NeighborSolicitMinimumSize},
 		{header.ICMPv6NeighborAdvert, header.ICMPv6NeighborAdvertSize},
 		{header.ICMPv6RedirectMsg, header.ICMPv6MinimumSize},
 	}

 	handleIPv6Payload := func(hdr buffer.Prependable) {
 		payloadLength := hdr.UsedLength()
 		ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
 		ip.Encode(&header.IPv6Fields{
 			PayloadLength: uint16(payloadLength),
 			NextHeader:    uint8(header.ICMPv6ProtocolNumber),
 			HopLimit:      ndpHopLimit,
 			SrcAddr:       r.LocalAddress,
 			DstAddr:       r.RemoteAddress,
 		})
 		ep.HandlePacket(&r, hdr.View().ToVectorisedView())
 	}

 	for _, typ := range types {
 		hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size)
 		pkt := header.ICMPv6(hdr.Prepend(typ.size))
 		pkt.SetType(typ.typ)
 		pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))

 		handleIPv6Payload(hdr)
 	}

 	// Construct an empty ICMP packet so that
 	// Stats().ICMP.ICMPv6ReceivedPacketStats.Invalid is incremented.
 	handleIPv6Payload(buffer.NewPrependable(header.IPv6MinimumSize))

 	icmpv6Stats := s.Stats().ICMP.V6PacketsReceived
 	visitStats(reflect.ValueOf(&icmpv6Stats).Elem(), func(name string, s *tcpip.StatCounter) {
 		if got, want := s.Value(), uint64(1); got != want {
 			t.Errorf("got %s = %d, want = %d", name, got, want)
 		}
 	})
 	if t.Failed() {
 		t.Logf("stats:\n%+v", s.Stats())
 	}
 }

 func visitStats(v reflect.Value, f func(string, *tcpip.StatCounter)) {
 	t := v.Type()
 	for i := 0; i < v.NumField(); i++ {
 		v := v.Field(i)
 		if s, ok := v.Interface().(*tcpip.StatCounter); ok {
 			f(t.Field(i).Name, s)
 		} else {
 			visitStats(v, f)
 		}
 	}
 }

 type testContext struct {
 	s0 *stack.Stack
 	s1 *stack.Stack

 	linkEP0 *channel.Endpoint
 	linkEP1 *channel.Endpoint
 }

 type endpointWithResolutionCapability struct {
 	stack.LinkEndpoint
 }

 func (e endpointWithResolutionCapability) Capabilities() stack.LinkEndpointCapabilities {
 	return e.LinkEndpoint.Capabilities() | stack.CapabilityResolutionRequired
 }

 func newTestContext(t *testing.T) *testContext {
 	c := &testContext{
 		s0: stack.New(stack.Options{
 			NetworkProtocols:   []stack.NetworkProtocol{NewProtocol()},
 			TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
 		}),
 		s1: stack.New(stack.Options{
 			NetworkProtocols:   []stack.NetworkProtocol{NewProtocol()},
 			TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
 		}),
 	}

 	const defaultMTU = 65536
 	c.linkEP0 = channel.New(256, defaultMTU, linkAddr0)

 	wrappedEP0 := stack.LinkEndpoint(endpointWithResolutionCapability{LinkEndpoint: c.linkEP0})
 	if testing.Verbose() {
 		wrappedEP0 = sniffer.New(wrappedEP0)
 	}
 	if err := c.s0.CreateNIC(1, wrappedEP0); err != nil {
 		t.Fatalf("CreateNIC s0: %v", err)
 	}
 	if err := c.s0.AddAddress(1, ProtocolNumber, lladdr0); err != nil {
 		t.Fatalf("AddAddress lladdr0: %v", err)
 	}

 	c.linkEP1 = channel.New(256, defaultMTU, linkAddr1)
 	wrappedEP1 := stack.LinkEndpoint(endpointWithResolutionCapability{LinkEndpoint: c.linkEP1})
 	if err := c.s1.CreateNIC(1, wrappedEP1); err != nil {
 		t.Fatalf("CreateNIC failed: %v", err)
 	}
 	if err := c.s1.AddAddress(1, ProtocolNumber, lladdr1); err != nil {
 		t.Fatalf("AddAddress lladdr1: %v", err)
 	}

 	subnet0, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
 	if err != nil {
 		t.Fatal(err)
 	}
 	c.s0.SetRouteTable(
 		[]tcpip.Route{{
 			Destination: subnet0,
 			NIC:         1,
 		}},
 	)
 	subnet1, err := tcpip.NewSubnet(lladdr0, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr0))))
 	if err != nil {
 		t.Fatal(err)
 	}
 	c.s1.SetRouteTable(
 		[]tcpip.Route{{
 			Destination: subnet1,
 			NIC:         1,
 		}},
 	)

 	return c
 }

 func (c *testContext) cleanup() {
 	close(c.linkEP0.C)
 	close(c.linkEP1.C)
 }

 type routeArgs struct {
 	src, dst *channel.Endpoint
 	typ      header.ICMPv6Type
 }

 func routeICMPv6Packet(t *testing.T, args routeArgs, fn func(*testing.T, header.ICMPv6)) {
 	t.Helper()

 	pkt := <-args.src.C

 	{
 		views := []buffer.View{pkt.Header, pkt.Payload}
 		size := len(pkt.Header) + len(pkt.Payload)
 		vv := buffer.NewVectorisedView(size, views)
 		args.dst.InjectLinkAddr(pkt.Proto, args.dst.LinkAddress(), vv)
 	}

 	if pkt.Proto != ProtocolNumber {
 		t.Errorf("unexpected protocol number %d", pkt.Proto)
 		return
 	}
 	ipv6 := header.IPv6(pkt.Header)
 	transProto := tcpip.TransportProtocolNumber(ipv6.NextHeader())
 	if transProto != header.ICMPv6ProtocolNumber {
 		t.Errorf("unexpected transport protocol number %d", transProto)
 		return
 	}
 	icmpv6 := header.ICMPv6(ipv6.Payload())
 	if got, want := icmpv6.Type(), args.typ; got != want {
 		t.Errorf("got ICMPv6 type = %d, want = %d", got, want)
 		return
 	}
 	if fn != nil {
 		fn(t, icmpv6)
 	}
 }

 func TestLinkResolution(t *testing.T) {
 	c := newTestContext(t)
 	defer c.cleanup()

 	r, err := c.s0.FindRoute(1, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute(_) = _, %s, want = _, nil", err)
 	}
 	defer r.Release()

 	hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6EchoMinimumSize)
 	pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
 	pkt.SetType(header.ICMPv6EchoRequest)
 	pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
 	payload := tcpip.SlicePayload(hdr.View())

 	// We can't send our payload directly over the route because that
 	// doesn't provoke NDP discovery.
 	var wq waiter.Queue
 	ep, err := c.s0.NewEndpoint(header.ICMPv6ProtocolNumber, ProtocolNumber, &wq)
 	if err != nil {
 		t.Fatalf("NewEndpoint(_) = _, %s, want = _, nil", err)
 	}

 	for {
 		_, resCh, err := ep.Write(payload, tcpip.WriteOptions{To: &tcpip.FullAddress{NIC: 1, Addr: lladdr1}})
 		if resCh != nil {
 			if err != tcpip.ErrNoLinkAddress {
 				t.Fatalf("ep.Write(_) = _, <non-nil>, %s, want = _, <non-nil>, tcpip.ErrNoLinkAddress", err)
 			}
 			for _, args := range []routeArgs{
 				{src: c.linkEP0, dst: c.linkEP1, typ: header.ICMPv6NeighborSolicit},
 				{src: c.linkEP1, dst: c.linkEP0, typ: header.ICMPv6NeighborAdvert},
 			} {
 				routeICMPv6Packet(t, args, func(t *testing.T, icmpv6 header.ICMPv6) {
 					if got, want := tcpip.Address(icmpv6[8:][:16]), lladdr1; got != want {
 						t.Errorf("%d: got target = %s, want = %s", icmpv6.Type(), got, want)
 					}
 				})
 			}
 			<-resCh
 			continue
 		}
 		if err != nil {
 			t.Fatalf("ep.Write(_) = _, _, %s", err)
 		}
 		break
 	}

 	for _, args := range []routeArgs{
 		{src: c.linkEP0, dst: c.linkEP1, typ: header.ICMPv6EchoRequest},
 		{src: c.linkEP1, dst: c.linkEP0, typ: header.ICMPv6EchoReply},
 	} {
 		routeICMPv6Packet(t, args, nil)
 	}
 }
	// Copyright 2018 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 ipv6

	import (
	"reflect"
	"strings"
	"testing"

	"github.com/google/netstack/tcpip"
	"github.com/google/netstack/tcpip/buffer"
	"github.com/google/netstack/tcpip/header"
	"github.com/google/netstack/tcpip/link/channel"
	"github.com/google/netstack/tcpip/link/sniffer"
	"github.com/google/netstack/tcpip/stack"
	"github.com/google/netstack/tcpip/transport/icmp"
	"github.com/google/netstack/waiter"
	)

	const (
	linkAddr0 = tcpip.LinkAddress("\x01\x02\x03\x04\x05\x06")
	linkAddr1 = tcpip.LinkAddress("\x0a\x0b\x0c\x0d\x0e\x0f")
	)

	var (
	lladdr0 = header.LinkLocalAddr(linkAddr0)
	lladdr1 = header.LinkLocalAddr(linkAddr1)
	)

	type stubLinkEndpoint struct {
	stack.LinkEndpoint
	}

	func (*stubLinkEndpoint) Capabilities() stack.LinkEndpointCapabilities {
	return 0
	}

	func (*stubLinkEndpoint) MaxHeaderLength() uint16 {
	return 0
	}

	func (*stubLinkEndpoint) LinkAddress() tcpip.LinkAddress {
	return ""
	}

	func (stubLinkEndpoint) WritePacket(stack.Route, stack.GSO, buffer.Prependable, buffer.VectorisedView, tcpip.NetworkProtocolNumber) tcpip.Error {
	return nil
	}

	func (*stubLinkEndpoint) Attach(stack.NetworkDispatcher) {}

	type stubDispatcher struct {
	stack.TransportDispatcher
	}

	func (stubDispatcher) DeliverTransportPacket(stack.Route, tcpip.TransportProtocolNumber, buffer.View, buffer.VectorisedView) {
	}

	type stubLinkAddressCache struct {
	stack.LinkAddressCache
	}

	func (*stubLinkAddressCache) CheckLocalAddress(tcpip.NICID, tcpip.NetworkProtocolNumber, tcpip.Address) tcpip.NICID {
	return 0
	}

	func (*stubLinkAddressCache) AddLinkAddress(tcpip.NICID, tcpip.Address, tcpip.LinkAddress) {
	}

	func TestICMPCounts(t *testing.T) {
	s := stack.New(stack.Options{
	NetworkProtocols: []stack.NetworkProtocol{NewProtocol()},
	TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
	})
	{
	if err := s.CreateNIC(1, &stubLinkEndpoint{}); err != nil {
	t.Fatalf("CreateNIC(_) = %s", err)
	}
	if err := s.AddAddress(1, ProtocolNumber, lladdr0); err != nil {
	t.Fatalf("AddAddress(_, %d, %s) = %s", ProtocolNumber, lladdr0, err)
	}
	}
	{
	subnet, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
	if err != nil {
	t.Fatal(err)
	}
	s.SetRouteTable(
	[]tcpip.Route{{
	Destination: subnet,
	NIC: 1,
	}},
	)
	}

	netProto := s.NetworkProtocolInstance(ProtocolNumber)
	if netProto == nil {
	t.Fatalf("cannot find protocol instance for network protocol %d", ProtocolNumber)
	}
	ep, err := netProto.NewEndpoint(0, tcpip.AddressWithPrefix{lladdr1, netProto.DefaultPrefixLen()}, &stubLinkAddressCache{}, &stubDispatcher{}, nil)
	if err != nil {
	t.Fatalf("NewEndpoint(_) = _, %s, want = _, nil", err)
	}

	r, err := s.FindRoute(1, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
	if err != nil {
	t.Fatalf("FindRoute(_) = _, %s, want = _, nil", err)
	}
	defer r.Release()

	types := []struct {
	typ header.ICMPv6Type
	size int
	}{
	{header.ICMPv6DstUnreachable, header.ICMPv6DstUnreachableMinimumSize},
	{header.ICMPv6PacketTooBig, header.ICMPv6PacketTooBigMinimumSize},
	{header.ICMPv6TimeExceeded, header.ICMPv6MinimumSize},
	{header.ICMPv6ParamProblem, header.ICMPv6MinimumSize},
	{header.ICMPv6EchoRequest, header.ICMPv6EchoMinimumSize},
	{header.ICMPv6EchoReply, header.ICMPv6EchoMinimumSize},
	{header.ICMPv6RouterSolicit, header.ICMPv6MinimumSize},
	{header.ICMPv6RouterAdvert, header.ICMPv6MinimumSize},
	{header.ICMPv6NeighborSolicit, header.ICMPv6NeighborSolicitMinimumSize},
	{header.ICMPv6NeighborAdvert, header.ICMPv6NeighborAdvertSize},
	{header.ICMPv6RedirectMsg, header.ICMPv6MinimumSize},
	}

	handleIPv6Payload := func(hdr buffer.Prependable) {
	payloadLength := hdr.UsedLength()
	ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
	ip.Encode(&header.IPv6Fields{
	PayloadLength: uint16(payloadLength),
	NextHeader: uint8(header.ICMPv6ProtocolNumber),
	HopLimit: ndpHopLimit,
	SrcAddr: r.LocalAddress,
	DstAddr: r.RemoteAddress,
	})
	ep.HandlePacket(&r, hdr.View().ToVectorisedView())
	}

	for _, typ := range types {
	hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size)
	pkt := header.ICMPv6(hdr.Prepend(typ.size))
	pkt.SetType(typ.typ)
	pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))

	handleIPv6Payload(hdr)
	}

	// Construct an empty ICMP packet so that
	// Stats().ICMP.ICMPv6ReceivedPacketStats.Invalid is incremented.
	handleIPv6Payload(buffer.NewPrependable(header.IPv6MinimumSize))

	icmpv6Stats := s.Stats().ICMP.V6PacketsReceived
	visitStats(reflect.ValueOf(&icmpv6Stats).Elem(), func(name string, s *tcpip.StatCounter) {
	if got, want := s.Value(), uint64(1); got != want {
	t.Errorf("got %s = %d, want = %d", name, got, want)
	}
	})
	if t.Failed() {
	t.Logf("stats:\n%+v", s.Stats())
	}
	}

	func visitStats(v reflect.Value, f func(string, *tcpip.StatCounter)) {
	t := v.Type()
	for i := 0; i < v.NumField(); i++ {
	v := v.Field(i)
	if s, ok := v.Interface().(*tcpip.StatCounter); ok {
	f(t.Field(i).Name, s)
	} else {
	visitStats(v, f)
	}
	}
	}

	type testContext struct {
	s0 *stack.Stack
	s1 *stack.Stack

	linkEP0 *channel.Endpoint
	linkEP1 *channel.Endpoint
	}

	type endpointWithResolutionCapability struct {
	stack.LinkEndpoint
	}

	func (e endpointWithResolutionCapability) Capabilities() stack.LinkEndpointCapabilities {
	return e.LinkEndpoint.Capabilities() \| stack.CapabilityResolutionRequired
	}

	func newTestContext(t testing.T) testContext {
	c := &testContext{
	s0: stack.New(stack.Options{
	NetworkProtocols: []stack.NetworkProtocol{NewProtocol()},
	TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
	}),
	s1: stack.New(stack.Options{
	NetworkProtocols: []stack.NetworkProtocol{NewProtocol()},
	TransportProtocols: []stack.TransportProtocol{icmp.NewProtocol6()},
	}),
	}

	const defaultMTU = 65536
	c.linkEP0 = channel.New(256, defaultMTU, linkAddr0)

	wrappedEP0 := stack.LinkEndpoint(endpointWithResolutionCapability{LinkEndpoint: c.linkEP0})
	if testing.Verbose() {
	wrappedEP0 = sniffer.New(wrappedEP0)
	}
	if err := c.s0.CreateNIC(1, wrappedEP0); err != nil {
	t.Fatalf("CreateNIC s0: %v", err)
	}
	if err := c.s0.AddAddress(1, ProtocolNumber, lladdr0); err != nil {
	t.Fatalf("AddAddress lladdr0: %v", err)
	}

	c.linkEP1 = channel.New(256, defaultMTU, linkAddr1)
	wrappedEP1 := stack.LinkEndpoint(endpointWithResolutionCapability{LinkEndpoint: c.linkEP1})
	if err := c.s1.CreateNIC(1, wrappedEP1); err != nil {
	t.Fatalf("CreateNIC failed: %v", err)
	}
	if err := c.s1.AddAddress(1, ProtocolNumber, lladdr1); err != nil {
	t.Fatalf("AddAddress lladdr1: %v", err)
	}

	subnet0, err := tcpip.NewSubnet(lladdr1, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr1))))
	if err != nil {
	t.Fatal(err)
	}
	c.s0.SetRouteTable(
	[]tcpip.Route{{
	Destination: subnet0,
	NIC: 1,
	}},
	)
	subnet1, err := tcpip.NewSubnet(lladdr0, tcpip.AddressMask(strings.Repeat("\xff", len(lladdr0))))
	if err != nil {
	t.Fatal(err)
	}
	c.s1.SetRouteTable(
	[]tcpip.Route{{
	Destination: subnet1,
	NIC: 1,
	}},
	)

	return c
	}

	func (c *testContext) cleanup() {
	close(c.linkEP0.C)
	close(c.linkEP1.C)
	}

	type routeArgs struct {
	src, dst *channel.Endpoint
	typ header.ICMPv6Type
	}

	func routeICMPv6Packet(t testing.T, args routeArgs, fn func(testing.T, header.ICMPv6)) {
	t.Helper()

	pkt := <-args.src.C

	{
	views := []buffer.View{pkt.Header, pkt.Payload}
	size := len(pkt.Header) + len(pkt.Payload)
	vv := buffer.NewVectorisedView(size, views)
	args.dst.InjectLinkAddr(pkt.Proto, args.dst.LinkAddress(), vv)
	}

	if pkt.Proto != ProtocolNumber {
	t.Errorf("unexpected protocol number %d", pkt.Proto)
	return
	}
	ipv6 := header.IPv6(pkt.Header)
	transProto := tcpip.TransportProtocolNumber(ipv6.NextHeader())
	if transProto != header.ICMPv6ProtocolNumber {
	t.Errorf("unexpected transport protocol number %d", transProto)
	return
	}
	icmpv6 := header.ICMPv6(ipv6.Payload())
	if got, want := icmpv6.Type(), args.typ; got != want {
	t.Errorf("got ICMPv6 type = %d, want = %d", got, want)
	return
	}
	if fn != nil {
	fn(t, icmpv6)
	}
	}

	func TestLinkResolution(t *testing.T) {
	c := newTestContext(t)
	defer c.cleanup()

	r, err := c.s0.FindRoute(1, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
	if err != nil {
	t.Fatalf("FindRoute(_) = _, %s, want = _, nil", err)
	}
	defer r.Release()

	hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6EchoMinimumSize)
	pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
	pkt.SetType(header.ICMPv6EchoRequest)
	pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
	payload := tcpip.SlicePayload(hdr.View())

	// We can't send our payload directly over the route because that
	// doesn't provoke NDP discovery.
	var wq waiter.Queue
	ep, err := c.s0.NewEndpoint(header.ICMPv6ProtocolNumber, ProtocolNumber, &wq)
	if err != nil {
	t.Fatalf("NewEndpoint(_) = _, %s, want = _, nil", err)
	}

	for {
	_, resCh, err := ep.Write(payload, tcpip.WriteOptions{To: &tcpip.FullAddress{NIC: 1, Addr: lladdr1}})
	if resCh != nil {
	if err != tcpip.ErrNoLinkAddress {
	t.Fatalf("ep.Write(_) = _, <non-nil>, %s, want = _, <non-nil>, tcpip.ErrNoLinkAddress", err)
	}
	for _, args := range []routeArgs{
	{src: c.linkEP0, dst: c.linkEP1, typ: header.ICMPv6NeighborSolicit},
	{src: c.linkEP1, dst: c.linkEP0, typ: header.ICMPv6NeighborAdvert},
	} {
	routeICMPv6Packet(t, args, func(t *testing.T, icmpv6 header.ICMPv6) {
	if got, want := tcpip.Address(icmpv6[8:][:16]), lladdr1; got != want {
	t.Errorf("%d: got target = %s, want = %s", icmpv6.Type(), got, want)
	}
	})
	}
	<-resCh
	continue
	}
	if err != nil {
	t.Fatalf("ep.Write(_) = _, _, %s", err)
	}
	break
	}

	for _, args := range []routeArgs{
	{src: c.linkEP0, dst: c.linkEP1, typ: header.ICMPv6EchoRequest},
	{src: c.linkEP1, dst: c.linkEP0, typ: header.ICMPv6EchoReply},
	} {
	routeICMPv6Packet(t, args, nil)
	}
	}