Support for receiving outbound packets in AF_PACKET.

Updates #173

PiperOrigin-RevId: 322665518

pkg/abi/linux/socket.go

@@ -134,6 +134,15 @@ const (
 	SHUT_RDWR = 2
 )
 
+// Packet types from <linux/if_packet.h>
+const (
+	PACKET_HOST      = 0 // To us
+	PACKET_BROADCAST = 1 // To all
+	PACKET_MULTICAST = 2 // To group
+	PACKET_OTHERHOST = 3 // To someone else
+	PACKET_OUTGOING  = 4 // Outgoing of any type
+)
+
 // Socket options from socket.h.
 const (
 	SO_DEBUG                 = 1

pkg/sentry/socket/netstack/netstack.go

@@ -26,6 +26,7 @@ package netstack
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"math"
 	"reflect"
@@ -2468,6 +2469,23 @@ func (s *socketOpsCommon) fillCmsgInq(cmsg *socket.ControlMessages) {
 	cmsg.IP.Inq = int32(len(s.readView) + rcvBufUsed)
 }
 
+func toLinuxPacketType(pktType tcpip.PacketType) uint8 {
+	switch pktType {
+	case tcpip.PacketHost:
+		return linux.PACKET_HOST
+	case tcpip.PacketOtherHost:
+		return linux.PACKET_OTHERHOST
+	case tcpip.PacketOutgoing:
+		return linux.PACKET_OUTGOING
+	case tcpip.PacketBroadcast:
+		return linux.PACKET_BROADCAST
+	case tcpip.PacketMulticast:
+		return linux.PACKET_MULTICAST
+	default:
+		panic(fmt.Sprintf("unknown packet type: %d", pktType))
+	}
+}
+
 // nonBlockingRead issues a non-blocking read.
 //
 // TODO(b/78348848): Support timestamps for stream sockets.
@@ -2526,6 +2544,7 @@ func (s *socketOpsCommon) nonBlockingRead(ctx context.Context, dst usermem.IOSeq
 		switch v := addr.(type) {
 		case *linux.SockAddrLink:
 			v.Protocol = htons(uint16(s.linkPacketInfo.Protocol))
+			v.PacketType = toLinuxPacketType(s.linkPacketInfo.PktType)
 		}
 	}
 

pkg/tcpip/link/channel/channel.go

@@ -302,3 +302,7 @@ func (e *Endpoint) RemoveNotify(handle *NotificationHandle) {
 func (*Endpoint) ARPHardwareType() header.ARPHardwareType {
 	return header.ARPHardwareNone
 }
+
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *Endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+}

pkg/tcpip/link/fdbased/endpoint.go

@@ -386,26 +386,33 @@ const (
 	_VIRTIO_NET_HDR_GSO_TCPV6 = 4
 )
 
-// WritePacket writes outbound packets to the file descriptor. If it is not
-// currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	if e.hdrSize > 0 {
 		// Add ethernet header if needed.
 		eth := header.Ethernet(pkt.Header.Prepend(header.EthernetMinimumSize))
 		pkt.LinkHeader = buffer.View(eth)
 		ethHdr := &header.EthernetFields{
-			DstAddr: r.RemoteLinkAddress,
+			DstAddr: remote,
 			Type:    protocol,
 		}
 
 		// Preserve the src address if it's set in the route.
-		if r.LocalLinkAddress != "" {
-			ethHdr.SrcAddr = r.LocalLinkAddress
+		if local != "" {
+			ethHdr.SrcAddr = local
 		} else {
 			ethHdr.SrcAddr = e.addr
 		}
 		eth.Encode(ethHdr)
 	}
+}
+
+// WritePacket writes outbound packets to the file descriptor. If it is not
+// currently writable, the packet is dropped.
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+	if e.hdrSize > 0 {
+		e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
+	}
 
 	var builder iovec.Builder
 
@@ -448,22 +455,8 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, *tc
 	// Send a batch of packets through batchFD.
 	mmsgHdrs := make([]rawfile.MMsgHdr, 0, len(batch))
 	for _, pkt := range batch {
-		var eth header.Ethernet
 		if e.hdrSize > 0 {
-			// Add ethernet header if needed.
-			eth = make(header.Ethernet, header.EthernetMinimumSize)
-			ethHdr := &header.EthernetFields{
-				DstAddr: pkt.EgressRoute.RemoteLinkAddress,
-				Type:    pkt.NetworkProtocolNumber,
-			}
-
-			// Preserve the src address if it's set in the route.
-			if pkt.EgressRoute.LocalLinkAddress != "" {
-				ethHdr.SrcAddr = pkt.EgressRoute.LocalLinkAddress
-			} else {
-				ethHdr.SrcAddr = e.addr
-			}
-			eth.Encode(ethHdr)
+			e.AddHeader(pkt.EgressRoute.LocalLinkAddress, pkt.EgressRoute.RemoteLinkAddress, pkt.NetworkProtocolNumber, pkt)
 		}
 
 		var vnetHdrBuf []byte
@@ -493,7 +486,6 @@ func (e *endpoint) sendBatch(batchFD int, batch []*stack.PacketBuffer) (int, *tc
 
 		var builder iovec.Builder
 		builder.Add(vnetHdrBuf)
-		builder.Add(eth)
 		builder.Add(pkt.Header.View())
 		for _, v := range pkt.Data.Views() {
 			builder.Add(v)

pkg/tcpip/link/fdbased/endpoint_test.go

@@ -107,6 +107,10 @@ func (c *context) DeliverNetworkPacket(remote tcpip.LinkAddress, local tcpip.Lin
 	c.ch <- packetInfo{remote, protocol, pkt}
 }
 
+func (c *context) DeliverOutboundPacket(remote tcpip.LinkAddress, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func TestNoEthernetProperties(t *testing.T) {
 	c := newContext(t, &Options{MTU: mtu})
 	defer c.cleanup()
@@ -510,6 +514,10 @@ func (d *fakeNetworkDispatcher) DeliverNetworkPacket(remote, local tcpip.LinkAdd
 	d.pkts = append(d.pkts, pkt)
 }
 
+func (d *fakeNetworkDispatcher) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func TestDispatchPacketFormat(t *testing.T) {
 	for _, test := range []struct {
 		name          string

pkg/tcpip/link/loopback/loopback.go

@@ -118,3 +118,6 @@ func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
 func (*endpoint) ARPHardwareType() header.ARPHardwareType {
 	return header.ARPHardwareLoopback
 }
+
+func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+}

pkg/tcpip/link/muxed/injectable.go

@@ -135,6 +135,10 @@ func (*InjectableEndpoint) ARPHardwareType() header.ARPHardwareType {
 	panic("unsupported operation")
 }
 
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (*InjectableEndpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+}
+
 // NewInjectableEndpoint creates a new multi-endpoint injectable endpoint.
 func NewInjectableEndpoint(routes map[tcpip.Address]stack.InjectableLinkEndpoint) *InjectableEndpoint {
 	return &InjectableEndpoint{

pkg/tcpip/link/nested/nested.go

@@ -61,6 +61,16 @@ func (e *Endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protoco
 	}
 }
 
+// DeliverOutboundPacket implements stack.NetworkDispatcher.DeliverOutboundPacket.
+func (e *Endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.mu.RLock()
+	d := e.dispatcher
+	e.mu.RUnlock()
+	if d != nil {
+		d.DeliverOutboundPacket(remote, local, protocol, pkt)
+	}
+}
+
 // Attach implements stack.LinkEndpoint.
 func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.mu.Lock()
@@ -135,3 +145,8 @@ func (e *Endpoint) GSOMaxSize() uint32 {
 func (e *Endpoint) ARPHardwareType() header.ARPHardwareType {
 	return e.child.ARPHardwareType()
 }
+
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *Endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.child.AddHeader(local, remote, protocol, pkt)
+}

pkg/tcpip/link/nested/nested_test.go

@@ -55,6 +55,10 @@ func (d *counterDispatcher) DeliverNetworkPacket(tcpip.LinkAddress, tcpip.LinkAd
 	d.count++
 }
 
+func (d *counterDispatcher) DeliverOutboundPacket(tcpip.LinkAddress, tcpip.LinkAddress, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func TestNestedLinkEndpoint(t *testing.T) {
 	const emptyAddress = tcpip.LinkAddress("")
 

pkg/tcpip/link/packetsocket/BUILD

@@ -0,0 +1,14 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "packetsocket",
+    srcs = ["endpoint.go"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/tcpip",
+        "//pkg/tcpip/link/nested",
+        "//pkg/tcpip/stack",
+    ],
+)

pkg/tcpip/link/packetsocket/endpoint.go

@@ -0,0 +1,50 @@
+// 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 packetsocket provides a link layer endpoint that provides the ability
+// to loop outbound packets to any AF_PACKET sockets that may be interested in
+// the outgoing packet.
+package packetsocket
+
+import (
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/link/nested"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+type endpoint struct {
+	nested.Endpoint
+}
+
+// New creates a new packetsocket LinkEndpoint.
+func New(lower stack.LinkEndpoint) stack.LinkEndpoint {
+	e := &endpoint{}
+	e.Endpoint.Init(lower, e)
+	return e
+}
+
+// WritePacket implements stack.LinkEndpoint.WritePacket.
+func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+	e.Endpoint.DeliverOutboundPacket(r.RemoteLinkAddress, r.LocalLinkAddress, protocol, pkt)
+	return e.Endpoint.WritePacket(r, gso, protocol, pkt)
+}
+
+// WritePackets implements stack.LinkEndpoint.WritePackets.
+func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
+		e.Endpoint.DeliverOutboundPacket(pkt.EgressRoute.RemoteLinkAddress, pkt.EgressRoute.LocalLinkAddress, pkt.NetworkProtocolNumber, pkt)
+	}
+
+	return e.Endpoint.WritePackets(r, gso, pkts, proto)
+}

pkg/tcpip/link/qdisc/fifo/endpoint.go

@@ -107,6 +107,11 @@ func (e *endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protoco
 	e.dispatcher.DeliverNetworkPacket(remote, local, protocol, pkt)
 }
 
+// DeliverOutboundPacket implements stack.NetworkDispatcher.DeliverOutboundPacket.
+func (e *endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.dispatcher.DeliverOutboundPacket(remote, local, protocol, pkt)
+}
+
 // Attach implements stack.LinkEndpoint.Attach.
 func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.dispatcher = dispatcher
@@ -194,6 +199,8 @@ func (e *endpoint) WritePackets(_ *stack.Route, _ *stack.GSO, pkts stack.PacketB
 
 // WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
 func (e *endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
+	// TODO(gvisor.dev/issue/3267/): Queue these packets as well once
+	// WriteRawPacket takes PacketBuffer instead of VectorisedView.
 	return e.lower.WriteRawPacket(vv)
 }
 
@@ -213,3 +220,8 @@ func (e *endpoint) Wait() {
 func (e *endpoint) ARPHardwareType() header.ARPHardwareType {
 	return e.lower.ARPHardwareType()
 }
+
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.lower.AddHeader(local, remote, protocol, pkt)
+}

pkg/tcpip/link/sharedmem/sharedmem.go

@@ -183,22 +183,29 @@ func (e *endpoint) LinkAddress() tcpip.LinkAddress {
 	return e.addr
 }
 
-// WritePacket writes outbound packets to the file descriptor. If it is not
-// currently writable, the packet is dropped.
-func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
-	// Add the ethernet header here.
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	// Add ethernet header if needed.
 	eth := header.Ethernet(pkt.Header.Prepend(header.EthernetMinimumSize))
 	pkt.LinkHeader = buffer.View(eth)
 	ethHdr := &header.EthernetFields{
-		DstAddr: r.RemoteLinkAddress,
+		DstAddr: remote,
 		Type:    protocol,
 	}
-	if r.LocalLinkAddress != "" {
-		ethHdr.SrcAddr = r.LocalLinkAddress
+
+	// Preserve the src address if it's set in the route.
+	if local != "" {
+		ethHdr.SrcAddr = local
 	} else {
 		ethHdr.SrcAddr = e.addr
 	}
 	eth.Encode(ethHdr)
+}
+
+// WritePacket writes outbound packets to the file descriptor. If it is not
+// currently writable, the packet is dropped.
+func (e *endpoint) WritePacket(r *stack.Route, _ *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+	e.AddHeader(r.LocalLinkAddress, r.RemoteLinkAddress, protocol, pkt)
 
 	v := pkt.Data.ToView()
 	// Transmit the packet.

pkg/tcpip/link/sharedmem/sharedmem_test.go

@@ -143,6 +143,10 @@ func (c *testContext) DeliverNetworkPacket(remoteLinkAddr, localLinkAddr tcpip.L
 	c.packetCh <- struct{}{}
 }
 
+func (c *testContext) DeliverOutboundPacket(remoteLinkAddr, localLinkAddr tcpip.LinkAddress, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func (c *testContext) cleanup() {
 	c.ep.Close()
 	closeFDs(&c.txCfg)

pkg/tcpip/link/sniffer/sniffer.go

@@ -123,6 +123,11 @@ func (e *endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protoco
 	e.Endpoint.DeliverNetworkPacket(remote, local, protocol, pkt)
 }
 
+// DeliverOutboundPacket implements stack.NetworkDispatcher.DeliverOutboundPacket.
+func (e *endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.Endpoint.DeliverOutboundPacket(remote, local, protocol, pkt)
+}
+
 func (e *endpoint) dumpPacket(prefix string, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
 	writer := e.writer
 	if writer == nil && atomic.LoadUint32(&LogPackets) == 1 {

pkg/tcpip/link/tun/device.go

@@ -272,21 +272,9 @@ func (d *Device) encodePkt(info *channel.PacketInfo) (buffer.View, bool) {
 	if d.hasFlags(linux.IFF_TAP) {
 		// Add ethernet header if not provided.
 		if info.Pkt.LinkHeader == nil {
-			hdr := &header.EthernetFields{
-				SrcAddr: info.Route.LocalLinkAddress,
-				DstAddr: info.Route.RemoteLinkAddress,
-				Type:    info.Proto,
-			}
-			if hdr.SrcAddr == "" {
-				hdr.SrcAddr = d.endpoint.LinkAddress()
-			}
-
-			eth := make(header.Ethernet, header.EthernetMinimumSize)
-			eth.Encode(hdr)
-			vv.AppendView(buffer.View(eth))
-		} else {
-			vv.AppendView(info.Pkt.LinkHeader)
+			d.endpoint.AddHeader(info.Route.LocalLinkAddress, info.Route.RemoteLinkAddress, info.Proto, info.Pkt)
 		}
+		vv.AppendView(info.Pkt.LinkHeader)
 	}
 
 	// Append upper headers.
@@ -366,3 +354,30 @@ func (e *tunEndpoint) ARPHardwareType() header.ARPHardwareType {
 	}
 	return header.ARPHardwareNone
 }
+
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *tunEndpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	if !e.isTap {
+		return
+	}
+	eth := header.Ethernet(pkt.Header.Prepend(header.EthernetMinimumSize))
+	pkt.LinkHeader = buffer.View(eth)
+	hdr := &header.EthernetFields{
+		SrcAddr: local,
+		DstAddr: remote,
+		Type:    protocol,
+	}
+	if hdr.SrcAddr == "" {
+		hdr.SrcAddr = e.LinkAddress()
+	}
+
+	eth.Encode(hdr)
+}
+
+// MaxHeaderLength returns the maximum size of the link layer header.
+func (e *tunEndpoint) MaxHeaderLength() uint16 {
+	if e.isTap {
+		return header.EthernetMinimumSize
+	}
+	return 0
+}

pkg/tcpip/link/waitable/waitable.go

@@ -60,6 +60,15 @@ func (e *Endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protoco
 	e.dispatchGate.Leave()
 }
 
+// DeliverOutboundPacket implements stack.NetworkDispatcher.DeliverOutboundPacket.
+func (e *Endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	if !e.dispatchGate.Enter() {
+		return
+	}
+	e.dispatcher.DeliverOutboundPacket(remote, local, protocol, pkt)
+	e.dispatchGate.Leave()
+}
+
 // Attach implements stack.LinkEndpoint.Attach. It saves the dispatcher and
 // registers with the lower endpoint as its dispatcher so that "e" is called
 // for inbound packets.
@@ -153,3 +162,8 @@ func (e *Endpoint) Wait() {}
 func (e *Endpoint) ARPHardwareType() header.ARPHardwareType {
 	return e.lower.ARPHardwareType()
 }
+
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *Endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	e.lower.AddHeader(local, remote, protocol, pkt)
+}

pkg/tcpip/link/waitable/waitable_test.go

@@ -40,6 +40,10 @@ func (e *countedEndpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress,
 	e.dispatchCount++
 }
 
+func (e *countedEndpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func (e *countedEndpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.attachCount++
 	e.dispatcher = dispatcher
@@ -90,6 +94,11 @@ func (*countedEndpoint) ARPHardwareType() header.ARPHardwareType {
 // Wait implements stack.LinkEndpoint.Wait.
 func (*countedEndpoint) Wait() {}
 
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *countedEndpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("unimplemented")
+}
+
 func TestWaitWrite(t *testing.T) {
 	ep := &countedEndpoint{}
 	wep := New(ep)

pkg/tcpip/network/ip_test.go

@@ -185,6 +185,11 @@ func (*testObject) ARPHardwareType() header.ARPHardwareType {
 	panic("not implemented")
 }
 
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (*testObject) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+	panic("not implemented")
+}
+
 func buildIPv4Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 	s := stack.New(stack.Options{
 		NetworkProtocols:   []stack.NetworkProtocol{ipv4.NewProtocol()},

pkg/tcpip/stack/forwarder_test.go

@@ -307,6 +307,11 @@ func (*fwdTestLinkEndpoint) ARPHardwareType() header.ARPHardwareType {
 	panic("not implemented")
 }
 
+// AddHeader implements stack.LinkEndpoint.AddHeader.
+func (e *fwdTestLinkEndpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) {
+	panic("not implemented")
+}
+
 func fwdTestNetFactory(t *testing.T, proto *fwdTestNetworkProtocol) (ep1, ep2 *fwdTestLinkEndpoint) {
 	// Create a stack with the network protocol and two NICs.
 	s := New(Options{