Do not resolve remote link address at transport layer

Link address resolution is performed at the link layer (if required) so
we can defer it from the transport layer. When link resolution is
required, packets will be queued and sent once link resolution
completes. If link resolution fails, the transport layer will receive a
control message indicating that the stack failed to route the packet.

tcpip.Endpoint.Write no longer returns a channel now that writes do not
wait for link resolution at the transport layer.

tcpip.ErrNoLinkAddress is no longer used so it is removed.

Removed calls to stack.Route.ResolveWith from the transport layer so
that link resolution is performed when a route is created in response
to an incoming packet (e.g. to complete TCP handshakes or send a RST).

Tests:
- integration_test.TestForwarding
- integration_test.TestTCPLinkResolutionFailure

Fixes #4458

RELNOTES: n/a
PiperOrigin-RevId: 351684158

1 files changed, 7 insertions, 7 deletions

diff --git a/pkg/tcpip/tests/integration/route_test.go b/pkg/tcpip/tests/integration/route_test.go
index 52cf89b54..76f7f54c6 100644
--- a/pkg/tcpip/tests/integration/route_test.go
+++ b/pkg/tcpip/tests/integration/route_test.go
@@ -197,10 +197,10 @@ func TestLocalPing(t *testing.T) {
 
 			payload := tcpip.SlicePayload(test.icmpBuf(t))
 			var wOpts tcpip.WriteOptions
-			if n, _, err := ep.Write(payload, wOpts); err != nil {
+			if n, err := ep.Write(payload, wOpts); err != nil {
 				t.Fatalf("ep.Write(%#v, %#v): %s", payload, wOpts, err)
 			} else if n != int64(len(payload)) {
-				t.Fatalf("got ep.Write(%#v, %#v) = (%d, _, nil), want = (%d, _, nil)", payload, wOpts, n, len(payload))
+				t.Fatalf("got ep.Write(%#v, %#v) = (%d, nil), want = (%d, nil)", payload, wOpts, n, len(payload))
 			}
 
 			// Wait for the endpoint to become readable.
@@ -335,14 +335,14 @@ func TestLocalUDP(t *testing.T) {
 						wOpts := tcpip.WriteOptions{
 							To: &serverAddr,
 						}
-						if n, _, err := client.Write(clientPayload, wOpts); err != subTest.expectedWriteErr {
-							t.Fatalf("got client.Write(%#v, %#v) = (%d, _, %s_), want = (_, _, %s)", clientPayload, wOpts, n, err, subTest.expectedWriteErr)
+						if n, err := client.Write(clientPayload, wOpts); err != subTest.expectedWriteErr {
+							t.Fatalf("got client.Write(%#v, %#v) = (%d, %s), want = (_, %s)", clientPayload, wOpts, n, err, subTest.expectedWriteErr)
 						} else if subTest.expectedWriteErr != nil {
 							// Nothing else to test if we expected not to be able to send the
 							// UDP packet.
 							return
 						} else if n != int64(len(clientPayload)) {
-							t.Fatalf("got client.Write(%#v, %#v) = (%d, _, nil), want = (%d, _, nil)", clientPayload, wOpts, n, len(clientPayload))
+							t.Fatalf("got client.Write(%#v, %#v) = (%d, nil), want = (%d, nil)", clientPayload, wOpts, n, len(clientPayload))
 						}
 					}
 
@@ -382,10 +382,10 @@ func TestLocalUDP(t *testing.T) {
 						wOpts := tcpip.WriteOptions{
 							To: &clientAddr,
 						}
-						if n, _, err := server.Write(serverPayload, wOpts); err != nil {
+						if n, err := server.Write(serverPayload, wOpts); err != nil {
 							t.Fatalf("server.Write(%#v, %#v): %s", serverPayload, wOpts, err)
 						} else if n != int64(len(serverPayload)) {
-							t.Fatalf("got server.Write(%#v, %#v) = (%d, _, nil), want = (%d, _, nil)", serverPayload, wOpts, n, len(serverPayload))
+							t.Fatalf("got server.Write(%#v, %#v) = (%d, nil), want = (%d, nil)", serverPayload, wOpts, n, len(serverPayload))
 						}
 					}