From 71bf90c55bd888f9b9c493533ca5e4b2b4b3d21d Mon Sep 17 00:00:00 2001
From: Bhasker Hariharan <bhaskerh@google.com>
Date: Wed, 22 Jul 2020 15:12:56 -0700
Subject: Support for receiving outbound packets in AF_PACKET.

Updates #173

PiperOrigin-RevId: 322665518
---
 pkg/tcpip/link/fdbased/endpoint.go      | 36 +++++++++++++--------------------
 pkg/tcpip/link/fdbased/endpoint_test.go |  8 ++++++++
 2 files changed, 22 insertions(+), 22 deletions(-)

(limited to 'pkg/tcpip/link/fdbased')

diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 6aa1badc7..c18bb91fb 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/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)
diff --git a/pkg/tcpip/link/fdbased/endpoint_test.go b/pkg/tcpip/link/fdbased/endpoint_test.go
index 4bad930c7..7b995b85a 100644
--- a/pkg/tcpip/link/fdbased/endpoint_test.go
+++ b/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
-- 
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