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, 8 insertions, 5 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 25b180fa5..ddbed7e46 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1507,7 +1507,7 @@ func (e *endpoint) isEndpointWritableLocked() (int, *tcpip.Error) {
 }
 
 // Write writes data to the endpoint's peer.
-func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *tcpip.Error) {
+func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, *tcpip.Error) {
 	// Linux completely ignores any address passed to sendto(2) for TCP sockets
 	// (without the MSG_FASTOPEN flag). Corking is unimplemented, so opts.More
 	// and opts.EndOfRecord are also ignored.
@@ -1520,7 +1520,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 		e.sndBufMu.Unlock()
 		e.UnlockUser()
 		e.stats.WriteErrors.WriteClosed.Increment()
-		return 0, nil, err
+		return 0, err
 	}
 
 	// We can release locks while copying data.
@@ -1541,7 +1541,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 			e.sndBufMu.Unlock()
 			e.UnlockUser()
 		}
-		return 0, nil, perr
+		return 0, perr
 	}
 
 	if !opts.Atomic {
@@ -1555,7 +1555,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 			e.sndBufMu.Unlock()
 			e.UnlockUser()
 			e.stats.WriteErrors.WriteClosed.Increment()
-			return 0, nil, err
+			return 0, err
 		}
 
 		// Discard any excess data copied in due to avail being reduced due
@@ -1575,7 +1575,7 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 	// Do the work inline.
 	e.handleWrite()
 	e.UnlockUser()
-	return int64(len(v)), nil, nil
+	return int64(len(v)), nil
 }
 
 // selectWindowLocked returns the new window without checking for shrinking or scaling
@@ -2779,6 +2779,9 @@ func (e *endpoint) HandleControlPacket(typ stack.ControlType, extra uint32, pkt
 	case stack.ControlNoRoute:
 		e.onICMPError(tcpip.ErrNoRoute, byte(header.ICMPv4DstUnreachable), byte(header.ICMPv4HostUnreachable), extra, pkt)
 
+	case stack.ControlAddressUnreachable:
+		e.onICMPError(tcpip.ErrNoRoute, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6AddressUnreachable), extra, pkt)
+
 	case stack.ControlNetworkUnreachable:
 		e.onICMPError(tcpip.ErrNetworkUnreachable, byte(header.ICMPv6DstUnreachable), byte(header.ICMPv6NetworkUnreachable), extra, pkt)
 	}