Do not resolve routes immediately

When a response needs to be sent to an incoming packet, the stack should
consult its neighbour table to determine the remote address's link
address.

When an entry does not exist in the stack's neighbor table, the stack
should queue the packet while link resolution completes. See comments.

PiperOrigin-RevId: 336185457

3 files changed, 601 insertions, 0 deletions

diff --git a/pkg/tcpip/tests/integration/BUILD b/pkg/tcpip/tests/integration/BUILD
index 06c7a3cd3..a4f141253 100644
--- a/pkg/tcpip/tests/integration/BUILD
+++ b/pkg/tcpip/tests/integration/BUILD
@@ -6,6 +6,8 @@ go_test(
     name = "integration_test",
     size = "small",
     srcs = [
+        "forward_test.go",
+        "link_resolution_test.go",
         "loopback_test.go",
         "multicast_broadcast_test.go",
     ],
@@ -15,6 +17,8 @@ go_test(
         "//pkg/tcpip/header",
         "//pkg/tcpip/link/channel",
         "//pkg/tcpip/link/loopback",
+        "//pkg/tcpip/link/pipe",
+        "//pkg/tcpip/network/arp",
         "//pkg/tcpip/network/ipv4",
         "//pkg/tcpip/network/ipv6",
         "//pkg/tcpip/stack",
diff --git a/pkg/tcpip/tests/integration/forward_test.go b/pkg/tcpip/tests/integration/forward_test.go
new file mode 100644
index 000000000..ffd38ee1a
--- /dev/null
+++ b/pkg/tcpip/tests/integration/forward_test.go
@@ -0,0 +1,378 @@
+// Copyright 2020 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 integration_test
+
+import (
+	"net"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/link/pipe"
+	"gvisor.dev/gvisor/pkg/tcpip/network/arp"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+	"gvisor.dev/gvisor/pkg/tcpip/transport/udp"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+func TestForwarding(t *testing.T) {
+	const (
+		host1NICLinkAddr   = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x06")
+		routerNIC1LinkAddr = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x07")
+		routerNIC2LinkAddr = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x08")
+		host2NICLinkAddr   = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x09")
+
+		host1NICID   = 1
+		routerNICID1 = 2
+		routerNICID2 = 3
+		host2NICID   = 4
+
+		listenPort = 8080
+	)
+
+	host1IPv4Addr := tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("192.168.0.2").To4()),
+			PrefixLen: 24,
+		},
+	}
+	routerNIC1IPv4Addr := tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("192.168.0.1").To4()),
+			PrefixLen: 24,
+		},
+	}
+	routerNIC2IPv4Addr := tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("10.0.0.1").To4()),
+			PrefixLen: 8,
+		},
+	}
+	host2IPv4Addr := tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("10.0.0.2").To4()),
+			PrefixLen: 8,
+		},
+	}
+	host1IPv6Addr := tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("a::2").To16()),
+			PrefixLen: 64,
+		},
+	}
+	routerNIC1IPv6Addr := tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("a::1").To16()),
+			PrefixLen: 64,
+		},
+	}
+	routerNIC2IPv6Addr := tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("b::1").To16()),
+			PrefixLen: 64,
+		},
+	}
+	host2IPv6Addr := tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("b::2").To16()),
+			PrefixLen: 64,
+		},
+	}
+
+	type endpointAndAddresses struct {
+		serverEP         tcpip.Endpoint
+		serverAddr       tcpip.Address
+		serverReadableCH chan struct{}
+
+		clientEP         tcpip.Endpoint
+		clientAddr       tcpip.Address
+		clientReadableCH chan struct{}
+	}
+
+	newEP := func(t *testing.T, s *stack.Stack, transProto tcpip.TransportProtocolNumber, netProto tcpip.NetworkProtocolNumber) (tcpip.Endpoint, chan struct{}) {
+		t.Helper()
+		var wq waiter.Queue
+		we, ch := waiter.NewChannelEntry(nil)
+		wq.EventRegister(&we, waiter.EventIn)
+		ep, err := s.NewEndpoint(transProto, netProto, &wq)
+		if err != nil {
+			t.Fatalf("s.NewEndpoint(%d, %d, _): %s", transProto, netProto, err)
+		}
+
+		t.Cleanup(func() {
+			wq.EventUnregister(&we)
+		})
+
+		return ep, ch
+	}
+
+	tests := []struct {
+		name       string
+		epAndAddrs func(t *testing.T, host1Stack, routerStack, host2Stack *stack.Stack) endpointAndAddresses
+	}{
+		{
+			name: "IPv4 host1 server with host2 client",
+			epAndAddrs: func(t *testing.T, host1Stack, routerStack, host2Stack *stack.Stack) endpointAndAddresses {
+				ep1, ep1WECH := newEP(t, host1Stack, udp.ProtocolNumber, ipv4.ProtocolNumber)
+				ep2, ep2WECH := newEP(t, host2Stack, udp.ProtocolNumber, ipv4.ProtocolNumber)
+				return endpointAndAddresses{
+					serverEP:         ep1,
+					serverAddr:       host1IPv4Addr.AddressWithPrefix.Address,
+					serverReadableCH: ep1WECH,
+
+					clientEP:         ep2,
+					clientAddr:       host2IPv4Addr.AddressWithPrefix.Address,
+					clientReadableCH: ep2WECH,
+				}
+			},
+		},
+		{
+			name: "IPv6 host2 server with host1 client",
+			epAndAddrs: func(t *testing.T, host1Stack, routerStack, host2Stack *stack.Stack) endpointAndAddresses {
+				ep1, ep1WECH := newEP(t, host2Stack, udp.ProtocolNumber, ipv6.ProtocolNumber)
+				ep2, ep2WECH := newEP(t, host1Stack, udp.ProtocolNumber, ipv6.ProtocolNumber)
+				return endpointAndAddresses{
+					serverEP:         ep1,
+					serverAddr:       host2IPv6Addr.AddressWithPrefix.Address,
+					serverReadableCH: ep1WECH,
+
+					clientEP:         ep2,
+					clientAddr:       host1IPv6Addr.AddressWithPrefix.Address,
+					clientReadableCH: ep2WECH,
+				}
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			stackOpts := stack.Options{
+				NetworkProtocols:   []stack.NetworkProtocolFactory{arp.NewProtocol, ipv4.NewProtocol, ipv6.NewProtocol},
+				TransportProtocols: []stack.TransportProtocolFactory{udp.NewProtocol},
+			}
+
+			host1Stack := stack.New(stackOpts)
+			routerStack := stack.New(stackOpts)
+			host2Stack := stack.New(stackOpts)
+
+			host1NIC, routerNIC1 := pipe.New(host1NICLinkAddr, routerNIC1LinkAddr, stack.CapabilityResolutionRequired)
+			routerNIC2, host2NIC := pipe.New(routerNIC2LinkAddr, host2NICLinkAddr, stack.CapabilityResolutionRequired)
+
+			if err := host1Stack.CreateNIC(host1NICID, host1NIC); err != nil {
+				t.Fatalf("host1Stack.CreateNIC(%d, _): %s", host1NICID, err)
+			}
+			if err := routerStack.CreateNIC(routerNICID1, routerNIC1); err != nil {
+				t.Fatalf("routerStack.CreateNIC(%d, _): %s", routerNICID1, err)
+			}
+			if err := routerStack.CreateNIC(routerNICID2, routerNIC2); err != nil {
+				t.Fatalf("routerStack.CreateNIC(%d, _): %s", routerNICID2, err)
+			}
+			if err := host2Stack.CreateNIC(host2NICID, host2NIC); err != nil {
+				t.Fatalf("host2Stack.CreateNIC(%d, _): %s", host2NICID, err)
+			}
+
+			if err := routerStack.SetForwarding(ipv4.ProtocolNumber, true); err != nil {
+				t.Fatalf("routerStack.SetForwarding(%d): %s", ipv4.ProtocolNumber, err)
+			}
+			if err := routerStack.SetForwarding(ipv6.ProtocolNumber, true); err != nil {
+				t.Fatalf("routerStack.SetForwarding(%d): %s", ipv6.ProtocolNumber, err)
+			}
+
+			if err := host1Stack.AddAddress(host1NICID, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("host1Stack.AddAddress(%d, %d, %s): %s", host1NICID, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+			if err := routerStack.AddAddress(routerNICID1, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("routerStack.AddAddress(%d, %d, %s): %s", routerNICID1, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+			if err := routerStack.AddAddress(routerNICID2, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("routerStack.AddAddress(%d, %d, %s): %s", routerNICID2, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+			if err := host2Stack.AddAddress(host2NICID, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("host2Stack.AddAddress(%d, %d, %s): %s", host2NICID, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+
+			if err := host1Stack.AddProtocolAddress(host1NICID, host1IPv4Addr); err != nil {
+				t.Fatalf("host1Stack.AddProtocolAddress(%d, %#v): %s", host1NICID, host1IPv4Addr, err)
+			}
+			if err := routerStack.AddProtocolAddress(routerNICID1, routerNIC1IPv4Addr); err != nil {
+				t.Fatalf("routerStack.AddProtocolAddress(%d, %#v): %s", routerNICID1, routerNIC1IPv4Addr, err)
+			}
+			if err := routerStack.AddProtocolAddress(routerNICID2, routerNIC2IPv4Addr); err != nil {
+				t.Fatalf("routerStack.AddProtocolAddress(%d, %#v): %s", routerNICID2, routerNIC2IPv4Addr, err)
+			}
+			if err := host2Stack.AddProtocolAddress(host2NICID, host2IPv4Addr); err != nil {
+				t.Fatalf("host2Stack.AddProtocolAddress(%d, %#v): %s", host2NICID, host2IPv4Addr, err)
+			}
+			if err := host1Stack.AddProtocolAddress(host1NICID, host1IPv6Addr); err != nil {
+				t.Fatalf("host1Stack.AddProtocolAddress(%d, %#v): %s", host1NICID, host1IPv6Addr, err)
+			}
+			if err := routerStack.AddProtocolAddress(routerNICID1, routerNIC1IPv6Addr); err != nil {
+				t.Fatalf("routerStack.AddProtocolAddress(%d, %#v): %s", routerNICID1, routerNIC1IPv6Addr, err)
+			}
+			if err := routerStack.AddProtocolAddress(routerNICID2, routerNIC2IPv6Addr); err != nil {
+				t.Fatalf("routerStack.AddProtocolAddress(%d, %#v): %s", routerNICID2, routerNIC2IPv6Addr, err)
+			}
+			if err := host2Stack.AddProtocolAddress(host2NICID, host2IPv6Addr); err != nil {
+				t.Fatalf("host2Stack.AddProtocolAddress(%d, %#v): %s", host2NICID, host2IPv6Addr, err)
+			}
+
+			host1Stack.SetRouteTable([]tcpip.Route{
+				tcpip.Route{
+					Destination: host1IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         host1NICID,
+				},
+				tcpip.Route{
+					Destination: host1IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         host1NICID,
+				},
+				tcpip.Route{
+					Destination: host2IPv4Addr.AddressWithPrefix.Subnet(),
+					Gateway:     routerNIC1IPv4Addr.AddressWithPrefix.Address,
+					NIC:         host1NICID,
+				},
+				tcpip.Route{
+					Destination: host2IPv6Addr.AddressWithPrefix.Subnet(),
+					Gateway:     routerNIC1IPv6Addr.AddressWithPrefix.Address,
+					NIC:         host1NICID,
+				},
+			})
+			routerStack.SetRouteTable([]tcpip.Route{
+				tcpip.Route{
+					Destination: routerNIC1IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         routerNICID1,
+				},
+				tcpip.Route{
+					Destination: routerNIC1IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         routerNICID1,
+				},
+				tcpip.Route{
+					Destination: routerNIC2IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         routerNICID2,
+				},
+				tcpip.Route{
+					Destination: routerNIC2IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         routerNICID2,
+				},
+			})
+			host2Stack.SetRouteTable([]tcpip.Route{
+				tcpip.Route{
+					Destination: host2IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         host2NICID,
+				},
+				tcpip.Route{
+					Destination: host2IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         host2NICID,
+				},
+				tcpip.Route{
+					Destination: host1IPv4Addr.AddressWithPrefix.Subnet(),
+					Gateway:     routerNIC2IPv4Addr.AddressWithPrefix.Address,
+					NIC:         host2NICID,
+				},
+				tcpip.Route{
+					Destination: host1IPv6Addr.AddressWithPrefix.Subnet(),
+					Gateway:     routerNIC2IPv6Addr.AddressWithPrefix.Address,
+					NIC:         host2NICID,
+				},
+			})
+
+			epsAndAddrs := test.epAndAddrs(t, host1Stack, routerStack, host2Stack)
+			defer epsAndAddrs.serverEP.Close()
+			defer epsAndAddrs.clientEP.Close()
+
+			serverAddr := tcpip.FullAddress{Addr: epsAndAddrs.serverAddr, Port: listenPort}
+			if err := epsAndAddrs.serverEP.Bind(serverAddr); err != nil {
+				t.Fatalf("epsAndAddrs.serverEP.Bind(%#v): %s", serverAddr, err)
+			}
+			clientAddr := tcpip.FullAddress{Addr: epsAndAddrs.clientAddr}
+			if err := epsAndAddrs.clientEP.Bind(clientAddr); err != nil {
+				t.Fatalf("epsAndAddrs.clientEP.Bind(%#v): %s", clientAddr, err)
+			}
+
+			write := func(ep tcpip.Endpoint, data []byte, to *tcpip.FullAddress) {
+				t.Helper()
+
+				dataPayload := tcpip.SlicePayload(data)
+				wOpts := tcpip.WriteOptions{To: to}
+				n, ch, err := ep.Write(dataPayload, wOpts)
+				if err == tcpip.ErrNoLinkAddress {
+					// Wait for link resolution to complete.
+					<-ch
+
+					n, _, err = ep.Write(dataPayload, wOpts)
+				} else if err != nil {
+					t.Fatalf("ep.Write(_, _): %s", err)
+				}
+
+				if err != nil {
+					t.Fatalf("ep.Write(_, _): %s", err)
+				}
+				if want := int64(len(data)); n != want {
+					t.Fatalf("got ep.Write(_, _) = (%d, _, _), want = (%d, _, _)", n, want)
+				}
+			}
+
+			data := []byte{1, 2, 3, 4}
+			write(epsAndAddrs.clientEP, data, &serverAddr)
+
+			read := func(ch chan struct{}, ep tcpip.Endpoint, data []byte, expectedFrom tcpip.Address) tcpip.FullAddress {
+				t.Helper()
+
+				// Wait for the endpoint to be readable.
+				<-ch
+
+				var addr tcpip.FullAddress
+				v, _, err := ep.Read(&addr)
+				if err != nil {
+					t.Fatalf("ep.Read(_): %s", err)
+				}
+
+				if diff := cmp.Diff(v, buffer.View(data)); diff != "" {
+					t.Errorf("received data mismatch (-want +got):\n%s", diff)
+				}
+				if addr.Addr != expectedFrom {
+					t.Errorf("got addr.Addr = %s, want = %s", addr.Addr, expectedFrom)
+				}
+
+				if t.Failed() {
+					t.FailNow()
+				}
+
+				return addr
+			}
+
+			addr := read(epsAndAddrs.serverReadableCH, epsAndAddrs.serverEP, data, epsAndAddrs.clientAddr)
+			// Unspecify the NIC since NIC IDs are meaningless across stacks.
+			addr.NIC = 0
+
+			data = tcpip.SlicePayload([]byte{5, 6, 7, 8, 9, 10, 11, 12})
+			write(epsAndAddrs.serverEP, data, &addr)
+			addr = read(epsAndAddrs.clientReadableCH, epsAndAddrs.clientEP, data, epsAndAddrs.serverAddr)
+			if addr.Port != listenPort {
+				t.Errorf("got addr.Port = %d, want = %d", addr.Port, listenPort)
+			}
+		})
+	}
+}
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
new file mode 100644
index 000000000..bf3a6f6ee
--- /dev/null
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -0,0 +1,219 @@
+// Copyright 2020 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 integration_test
+
+import (
+	"net"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/link/pipe"
+	"gvisor.dev/gvisor/pkg/tcpip/network/arp"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+	"gvisor.dev/gvisor/pkg/tcpip/transport/icmp"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+var (
+	host1NICLinkAddr = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x06")
+	host2NICLinkAddr = tcpip.LinkAddress("\x02\x03\x03\x04\x05\x09")
+
+	host1IPv4Addr = tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("192.168.0.1").To4()),
+			PrefixLen: 24,
+		},
+	}
+	host2IPv4Addr = tcpip.ProtocolAddress{
+		Protocol: ipv4.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("192.168.0.2").To4()),
+			PrefixLen: 8,
+		},
+	}
+	host1IPv6Addr = tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("a::1").To16()),
+			PrefixLen: 64,
+		},
+	}
+	host2IPv6Addr = tcpip.ProtocolAddress{
+		Protocol: ipv6.ProtocolNumber,
+		AddressWithPrefix: tcpip.AddressWithPrefix{
+			Address:   tcpip.Address(net.ParseIP("a::2").To16()),
+			PrefixLen: 64,
+		},
+	}
+)
+
+// TestPing tests that two hosts can ping eachother when link resolution is
+// enabled.
+func TestPing(t *testing.T) {
+	const (
+		host1NICID = 1
+		host2NICID = 4
+
+		// icmpDataOffset is the offset to the data in both ICMPv4 and ICMPv6 echo
+		// request/reply packets.
+		icmpDataOffset = 8
+	)
+
+	tests := []struct {
+		name       string
+		transProto tcpip.TransportProtocolNumber
+		netProto   tcpip.NetworkProtocolNumber
+		remoteAddr tcpip.Address
+		icmpBuf    func(*testing.T) buffer.View
+	}{
+		{
+			name:       "IPv4 Ping",
+			transProto: icmp.ProtocolNumber4,
+			netProto:   ipv4.ProtocolNumber,
+			remoteAddr: host2IPv4Addr.AddressWithPrefix.Address,
+			icmpBuf: func(t *testing.T) buffer.View {
+				data := [8]byte{1, 2, 3, 4, 5, 6, 7, 8}
+				hdr := header.ICMPv4(make([]byte, header.ICMPv4MinimumSize+len(data)))
+				hdr.SetType(header.ICMPv4Echo)
+				if n := copy(hdr.Payload(), data[:]); n != len(data) {
+					t.Fatalf("copied %d bytes but expected to copy %d bytes", n, len(data))
+				}
+				return buffer.View(hdr)
+			},
+		},
+		{
+			name:       "IPv6 Ping",
+			transProto: icmp.ProtocolNumber6,
+			netProto:   ipv6.ProtocolNumber,
+			remoteAddr: host2IPv6Addr.AddressWithPrefix.Address,
+			icmpBuf: func(t *testing.T) buffer.View {
+				data := [8]byte{1, 2, 3, 4, 5, 6, 7, 8}
+				hdr := header.ICMPv6(make([]byte, header.ICMPv6MinimumSize+len(data)))
+				hdr.SetType(header.ICMPv6EchoRequest)
+				if n := copy(hdr.Payload(), data[:]); n != len(data) {
+					t.Fatalf("copied %d bytes but expected to copy %d bytes", n, len(data))
+				}
+				return buffer.View(hdr)
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			stackOpts := stack.Options{
+				NetworkProtocols:   []stack.NetworkProtocolFactory{arp.NewProtocol, ipv4.NewProtocol, ipv6.NewProtocol},
+				TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol4, icmp.NewProtocol6},
+			}
+
+			host1Stack := stack.New(stackOpts)
+			host2Stack := stack.New(stackOpts)
+
+			host1NIC, host2NIC := pipe.New(host1NICLinkAddr, host2NICLinkAddr, stack.CapabilityResolutionRequired)
+
+			if err := host1Stack.CreateNIC(host1NICID, host1NIC); err != nil {
+				t.Fatalf("host1Stack.CreateNIC(%d, _): %s", host1NICID, err)
+			}
+			if err := host2Stack.CreateNIC(host2NICID, host2NIC); err != nil {
+				t.Fatalf("host2Stack.CreateNIC(%d, _): %s", host2NICID, err)
+			}
+
+			if err := host1Stack.AddAddress(host1NICID, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("host1Stack.AddAddress(%d, %d, %s): %s", host1NICID, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+			if err := host2Stack.AddAddress(host2NICID, arp.ProtocolNumber, arp.ProtocolAddress); err != nil {
+				t.Fatalf("host2Stack.AddAddress(%d, %d, %s): %s", host2NICID, arp.ProtocolNumber, arp.ProtocolAddress, err)
+			}
+
+			if err := host1Stack.AddProtocolAddress(host1NICID, host1IPv4Addr); err != nil {
+				t.Fatalf("host1Stack.AddProtocolAddress(%d, %#v): %s", host1NICID, host1IPv4Addr, err)
+			}
+			if err := host2Stack.AddProtocolAddress(host2NICID, host2IPv4Addr); err != nil {
+				t.Fatalf("host2Stack.AddProtocolAddress(%d, %#v): %s", host2NICID, host2IPv4Addr, err)
+			}
+			if err := host1Stack.AddProtocolAddress(host1NICID, host1IPv6Addr); err != nil {
+				t.Fatalf("host1Stack.AddProtocolAddress(%d, %#v): %s", host1NICID, host1IPv6Addr, err)
+			}
+			if err := host2Stack.AddProtocolAddress(host2NICID, host2IPv6Addr); err != nil {
+				t.Fatalf("host2Stack.AddProtocolAddress(%d, %#v): %s", host2NICID, host2IPv6Addr, err)
+			}
+
+			host1Stack.SetRouteTable([]tcpip.Route{
+				tcpip.Route{
+					Destination: host1IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         host1NICID,
+				},
+				tcpip.Route{
+					Destination: host1IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         host1NICID,
+				},
+			})
+			host2Stack.SetRouteTable([]tcpip.Route{
+				tcpip.Route{
+					Destination: host2IPv4Addr.AddressWithPrefix.Subnet(),
+					NIC:         host2NICID,
+				},
+				tcpip.Route{
+					Destination: host2IPv6Addr.AddressWithPrefix.Subnet(),
+					NIC:         host2NICID,
+				},
+			})
+
+			var wq waiter.Queue
+			we, waiterCH := waiter.NewChannelEntry(nil)
+			wq.EventRegister(&we, waiter.EventIn)
+			ep, err := host1Stack.NewEndpoint(test.transProto, test.netProto, &wq)
+			if err != nil {
+				t.Fatalf("host1Stack.NewEndpoint(%d, %d, _): %s", test.transProto, test.netProto, err)
+			}
+			defer ep.Close()
+
+			// The first write should trigger link resolution.
+			icmpBuf := test.icmpBuf(t)
+			wOpts := tcpip.WriteOptions{To: &tcpip.FullAddress{Addr: test.remoteAddr}}
+			if _, ch, err := ep.Write(tcpip.SlicePayload(icmpBuf), wOpts); err != tcpip.ErrNoLinkAddress {
+				t.Fatalf("got ep.Write(_, _) = %s, want = %s", err, tcpip.ErrNoLinkAddress)
+			} else {
+				// Wait for link resolution to complete.
+				<-ch
+			}
+			if n, _, err := ep.Write(tcpip.SlicePayload(icmpBuf), wOpts); err != nil {
+				t.Fatalf("ep.Write(_, _): %s", err)
+			} else if want := int64(len(icmpBuf)); n != want {
+				t.Fatalf("got ep.Write(_, _) = (%d, _, _), want = (%d, _, _)", n, want)
+			}
+
+			// Wait for the endpoint to be readable.
+			<-waiterCH
+
+			var addr tcpip.FullAddress
+			v, _, err := ep.Read(&addr)
+			if err != nil {
+				t.Fatalf("ep.Read(_): %s", err)
+			}
+			if diff := cmp.Diff(v[icmpDataOffset:], icmpBuf[icmpDataOffset:]); diff != "" {
+				t.Errorf("received data mismatch (-want +got):\n%s", diff)
+			}
+			if addr.Addr != test.remoteAddr {
+				t.Errorf("got addr.Addr = %s, want = %s", addr.Addr, test.remoteAddr)
+			}
+		})
+	}
+}