Implement IP_MULTICAST_LOOP.

IP_MULTICAST_LOOP controls whether or not multicast packets sent on the default
route are looped back. In order to implement this switch, support for sending
and looping back multicast packets on the default route had to be implemented.

For now we only support IPv4 multicast.

PiperOrigin-RevId: 237534603
Change-Id: I490ac7ff8e8ebef417c7eb049a919c29d156ac1c

1 files changed, 26 insertions, 14 deletions

diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index aba1e984c..b366de21d 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -112,7 +112,7 @@ func (f *fakeNetworkEndpoint) Capabilities() stack.LinkEndpointCapabilities {
 	return f.linkEP.Capabilities()
 }
 
-func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, _ uint8) *tcpip.Error {
+func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, _ uint8, loop stack.PacketLooping) *tcpip.Error {
 	// Increment the sent packet count in the protocol descriptor.
 	f.proto.sendPacketCount[int(r.RemoteAddress[0])%len(f.proto.sendPacketCount)]++
 
@@ -122,6 +122,18 @@ func (f *fakeNetworkEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable
 	b[0] = r.RemoteAddress[0]
 	b[1] = f.id.LocalAddress[0]
 	b[2] = byte(protocol)
+
+	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)
+		f.HandlePacket(r, vv)
+	}
+	if loop&stack.PacketOut == 0 {
+		return nil
+	}
+
 	return f.linkEP.WritePacket(r, hdr, payload, fakeNetNumber)
 }
 
@@ -262,7 +274,7 @@ func TestNetworkReceive(t *testing.T) {
 }
 
 func sendTo(t *testing.T, s *stack.Stack, addr tcpip.Address) {
-	r, err := s.FindRoute(0, "", addr, fakeNetNumber)
+	r, err := s.FindRoute(0, "", addr, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute failed: %v", err)
 	}
@@ -354,7 +366,7 @@ func TestNetworkSendMultiRoute(t *testing.T) {
 }
 
 func testRoute(t *testing.T, s *stack.Stack, nic tcpip.NICID, srcAddr, dstAddr, expectedSrcAddr tcpip.Address) {
-	r, err := s.FindRoute(nic, srcAddr, dstAddr, fakeNetNumber)
+	r, err := s.FindRoute(nic, srcAddr, dstAddr, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute failed: %v", err)
 	}
@@ -371,7 +383,7 @@ func testRoute(t *testing.T, s *stack.Stack, nic tcpip.NICID, srcAddr, dstAddr,
 }
 
 func testNoRoute(t *testing.T, s *stack.Stack, nic tcpip.NICID, srcAddr, dstAddr tcpip.Address) {
-	_, err := s.FindRoute(nic, srcAddr, dstAddr, fakeNetNumber)
+	_, err := s.FindRoute(nic, srcAddr, dstAddr, fakeNetNumber, false /* multicastLoop */)
 	if err != tcpip.ErrNoRoute {
 		t.Fatalf("FindRoute returned unexpected error, expected tcpip.ErrNoRoute, got %v", err)
 	}
@@ -514,7 +526,7 @@ func TestDelayedRemovalDueToRoute(t *testing.T) {
 	}
 
 	// Get a route, check that packet is still deliverable.
-	r, err := s.FindRoute(0, "", "\x02", fakeNetNumber)
+	r, err := s.FindRoute(0, "", "\x02", fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute failed: %v", err)
 	}
@@ -584,7 +596,7 @@ func TestPromiscuousMode(t *testing.T) {
 	}
 
 	// Check that we can't get a route as there is no local address.
-	_, err := s.FindRoute(0, "", "\x02", fakeNetNumber)
+	_, err := s.FindRoute(0, "", "\x02", fakeNetNumber, false /* multicastLoop */)
 	if err != tcpip.ErrNoRoute {
 		t.Fatalf("FindRoute returned unexpected status: expected %v, got %v", tcpip.ErrNoRoute, err)
 	}
@@ -622,7 +634,7 @@ func TestAddressSpoofing(t *testing.T) {
 
 	// With address spoofing disabled, FindRoute does not permit an address
 	// that was not added to the NIC to be used as the source.
-	r, err := s.FindRoute(0, srcAddr, dstAddr, fakeNetNumber)
+	r, err := s.FindRoute(0, srcAddr, dstAddr, fakeNetNumber, false /* multicastLoop */)
 	if err == nil {
 		t.Errorf("FindRoute succeeded with route %+v when it should have failed", r)
 	}
@@ -632,7 +644,7 @@ func TestAddressSpoofing(t *testing.T) {
 	if err := s.SetSpoofing(1, true); err != nil {
 		t.Fatalf("SetSpoofing failed: %v", err)
 	}
-	r, err = s.FindRoute(0, srcAddr, dstAddr, fakeNetNumber)
+	r, err = s.FindRoute(0, srcAddr, dstAddr, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute failed: %v", err)
 	}
@@ -654,14 +666,14 @@ func TestBroadcastNeedsNoRoute(t *testing.T) {
 	s.SetRouteTable([]tcpip.Route{})
 
 	// If there is no endpoint, it won't work.
-	if _, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber); err != tcpip.ErrNetworkUnreachable {
+	if _, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */); err != tcpip.ErrNetworkUnreachable {
 		t.Fatalf("got FindRoute(1, %v, %v, %v) = %v, want = %v", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, tcpip.ErrNetworkUnreachable)
 	}
 
 	if err := s.AddAddress(1, fakeNetNumber, header.IPv4Any); err != nil {
 		t.Fatalf("AddAddress(%v, %v) failed: %v", fakeNetNumber, header.IPv4Any, err)
 	}
-	r, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber)
+	r, err := s.FindRoute(1, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */)
 	if err != nil {
 		t.Fatalf("FindRoute(1, %v, %v, %v) failed: %v", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err)
 	}
@@ -675,7 +687,7 @@ func TestBroadcastNeedsNoRoute(t *testing.T) {
 	}
 
 	// If the NIC doesn't exist, it won't work.
-	if _, err := s.FindRoute(2, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber); err != tcpip.ErrNetworkUnreachable {
+	if _, err := s.FindRoute(2, header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, false /* multicastLoop */); err != tcpip.ErrNetworkUnreachable {
 		t.Fatalf("got FindRoute(2, %v, %v, %v) = %v want = %v", header.IPv4Any, header.IPv4Broadcast, fakeNetNumber, err, tcpip.ErrNetworkUnreachable)
 	}
 }
@@ -738,7 +750,7 @@ func TestMulticastOrIPv6LinkLocalNeedsNoRoute(t *testing.T) {
 			}
 
 			// If there is no endpoint, it won't work.
-			if _, err := s.FindRoute(1, anyAddr, tc.address, fakeNetNumber); err != want {
+			if _, err := s.FindRoute(1, anyAddr, tc.address, fakeNetNumber, false /* multicastLoop */); err != want {
 				t.Fatalf("got FindRoute(1, %v, %v, %v) = %v, want = %v", anyAddr, tc.address, fakeNetNumber, err, want)
 			}
 
@@ -746,7 +758,7 @@ func TestMulticastOrIPv6LinkLocalNeedsNoRoute(t *testing.T) {
 				t.Fatalf("AddAddress(%v, %v) failed: %v", fakeNetNumber, anyAddr, err)
 			}
 
-			if r, err := s.FindRoute(1, anyAddr, tc.address, fakeNetNumber); tc.routeNeeded {
+			if r, err := s.FindRoute(1, anyAddr, tc.address, fakeNetNumber, false /* multicastLoop */); tc.routeNeeded {
 				// Route table is empty but we need a route, this should cause an error.
 				if err != tcpip.ErrNoRoute {
 					t.Fatalf("got FindRoute(1, %v, %v, %v) = %v, want = %v", anyAddr, tc.address, fakeNetNumber, err, tcpip.ErrNoRoute)
@@ -763,7 +775,7 @@ func TestMulticastOrIPv6LinkLocalNeedsNoRoute(t *testing.T) {
 				}
 			}
 			// If the NIC doesn't exist, it won't work.
-			if _, err := s.FindRoute(2, anyAddr, tc.address, fakeNetNumber); err != want {
+			if _, err := s.FindRoute(2, anyAddr, tc.address, fakeNetNumber, false /* multicastLoop */); err != want {
 				t.Fatalf("got FindRoute(2, %v, %v, %v) = %v want = %v", anyAddr, tc.address, fakeNetNumber, err, want)
 			}
 		})