5 files changed, 32 insertions, 10 deletions
diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index ed39640c1..5ab542f2c 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -79,7 +79,7 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 
 func (e *endpoint) Close() {}
 
-func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
+func (e *endpoint) WritePacket(*stack.Route, buffer.Prependable, buffer.VectorisedView, tcpip.TransportProtocolNumber, uint8, stack.PacketLooping) *tcpip.Error {
 	return tcpip.ErrNotSupported
 }
 
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index 97a43aece..7eb0e697d 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -177,7 +177,7 @@ func buildIPv4Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 		NIC:         1,
 	}})
 
-	return s.FindRoute(1, local, remote, ipv4.ProtocolNumber)
+	return s.FindRoute(1, local, remote, ipv4.ProtocolNumber, false /* multicastLoop */)
 }
 
 func buildIPv6Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
@@ -191,7 +191,7 @@ func buildIPv6Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 		NIC:         1,
 	}})
 
-	return s.FindRoute(1, local, remote, ipv6.ProtocolNumber)
+	return s.FindRoute(1, local, remote, ipv6.ProtocolNumber, false /* multicastLoop */)
 }
 
 func TestIPv4Send(t *testing.T) {
@@ -221,7 +221,7 @@ func TestIPv4Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(&r, hdr, payload.ToVectorisedView(), 123, 123); err != nil {
+	if err := ep.WritePacket(&r, hdr, payload.ToVectorisedView(), 123, 123, stack.PacketOut); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 }
@@ -450,7 +450,7 @@ func TestIPv6Send(t *testing.T) {
 	if err != nil {
 		t.Fatalf("could not find route: %v", err)
 	}
-	if err := ep.WritePacket(&r, hdr, payload.ToVectorisedView(), 123, 123); err != nil {
+	if err := ep.WritePacket(&r, hdr, payload.ToVectorisedView(), 123, 123, stack.PacketOut); err != nil {
 		t.Fatalf("WritePacket failed: %v", err)
 	}
 }
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index bfc3c08fa..545684032 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -104,7 +104,7 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8, loop stack.PacketLooping) *tcpip.Error {
 	ip := header.IPv4(hdr.Prepend(header.IPv4MinimumSize))
 	length := uint16(hdr.UsedLength() + payload.Size())
 	id := uint32(0)
@@ -123,8 +123,19 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload b
 		DstAddr:     r.RemoteAddress,
 	})
 	ip.SetChecksum(^ip.CalculateChecksum())
-	r.Stats().IP.PacketsSent.Increment()
 
+	if loop&stack.PacketLoop != 0 {
+		views := make([]buffer.View, 1, 1+len(payload.Views()))
+		views[0] = hdr.View()
+		views = append(views, payload.Views()...)
+		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
+		e.HandlePacket(r, vv)
+	}
+	if loop&stack.PacketOut == 0 {
+		return nil
+	}
+
+	r.Stats().IP.PacketsSent.Increment()
 	return e.linkEP.WritePacket(r, hdr, payload, ProtocolNumber)
 }
 
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 797176243..15574bab1 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -161,7 +161,7 @@ func (c *testContext) cleanup() {
 func TestLinkResolution(t *testing.T) {
 	c := newTestContext(t)
 	defer c.cleanup()
-	r, err := c.s0.FindRoute(1, lladdr0, lladdr1, ProtocolNumber)
+	r, err := c.s0.FindRoute(1, lladdr0, lladdr1, ProtocolNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 5f68ef7d5..df3b64c98 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -84,7 +84,7 @@ func (e *endpoint) MaxHeaderLength() uint16 {
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
-func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
+func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8, loop stack.PacketLooping) *tcpip.Error {
 	length := uint16(hdr.UsedLength() + payload.Size())
 	ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
 	ip.Encode(&header.IPv6Fields{
@@ -94,8 +94,19 @@ func (e *endpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload b
 		SrcAddr:       r.LocalAddress,
 		DstAddr:       r.RemoteAddress,
 	})
-	r.Stats().IP.PacketsSent.Increment()
 
+	if loop&stack.PacketLoop != 0 {
+		views := make([]buffer.View, 1, 1+len(payload.Views()))
+		views[0] = hdr.View()
+		views = append(views, payload.Views()...)
+		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
+		e.HandlePacket(r, vv)
+	}
+	if loop&stack.PacketOut == 0 {
+		return nil
+	}
+
+	r.Stats().IP.PacketsSent.Increment()
 	return e.linkEP.WritePacket(r, hdr, payload, ProtocolNumber)
 }