Adds a WriteRawPacket method to the InjectableLinkEndpoint interface.

Also exposes ipv4.MaxTotalSize since it is a generally useful constant.

PiperOrigin-RevId: 235799755
Change-Id: I1fa8d5294bf355acf5527cfdf274b3687d3c8b13

2 files changed, 27 insertions, 1 deletions

diff --git a/pkg/tcpip/link/muxed/injectable.go b/pkg/tcpip/link/muxed/injectable.go
index 9d85bda60..29073afae 100644
--- a/pkg/tcpip/link/muxed/injectable.go
+++ b/pkg/tcpip/link/muxed/injectable.go
@@ -94,7 +94,17 @@ func (m *InjectableEndpoint) WritePacket(r *stack.Route, hdr buffer.Prependable,
 	return tcpip.ErrNoRoute
 }
 
-// NewInjectableEndpoint creates a new multi-fd-based injectable endpoint.
+// WriteRawPacket writes outbound packets to the appropriate
+// LinkInjectableEndpoint based on the dest address.
+func (m *InjectableEndpoint) WriteRawPacket(dest tcpip.Address, packet []byte) *tcpip.Error {
+	endpoint, ok := m.routes[dest]
+	if !ok {
+		return tcpip.ErrNoRoute
+	}
+	return endpoint.WriteRawPacket(dest, packet)
+}
+
+// NewInjectableEndpoint creates a new multi-endpoint injectable endpoint.
 func NewInjectableEndpoint(routes map[tcpip.Address]stack.InjectableLinkEndpoint, mtu uint32) (tcpip.LinkEndpointID, *InjectableEndpoint) {
 	e := &InjectableEndpoint{
 		routes: routes,
diff --git a/pkg/tcpip/link/muxed/injectable_test.go b/pkg/tcpip/link/muxed/injectable_test.go
index 65db14b5d..d1d2875cc 100644
--- a/pkg/tcpip/link/muxed/injectable_test.go
+++ b/pkg/tcpip/link/muxed/injectable_test.go
@@ -28,8 +28,24 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
 )
 
+func TestInjectableEndpointRawDispatch(t *testing.T) {
+	endpoint, sock, dstIP := makeTestInjectableEndpoint(t)
+
+	endpoint.WriteRawPacket(dstIP, []byte{0xFA})
+
+	buf := make([]byte, ipv4.MaxTotalSize)
+	bytesRead, err := sock.Read(buf)
+	if err != nil {
+		t.Fatalf("Unable to read from socketpair: %v", err)
+	}
+	if got, want := buf[:bytesRead], []byte{0xFA}; !bytes.Equal(got, want) {
+		t.Fatalf("Read %v from the socketpair, wanted %v", got, want)
+	}
+}
+
 func TestInjectableEndpointDispatch(t *testing.T) {
 	endpoint, sock, dstIP := makeTestInjectableEndpoint(t)
+
 	hdr := buffer.NewPrependable(1)
 	hdr.Prepend(1)[0] = 0xFA
 	packetRoute := stack.Route{RemoteAddress: dstIP}