Remove generic ICMP errors

Generic ICMP errors were required because the transport dispatcher was
given the responsibility of sending ICMP errors in response to transport
packet delivery failures. Instead, the transport dispatcher should let
network layer know it failed to deliver a packet (and why) and let the
network layer make the decision as to what error to send (if any).

Fixes #4068

PiperOrigin-RevId: 333962333

1 files changed, 12 insertions, 1 deletions

diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 5b1cca180..3d070ddea 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -482,7 +482,18 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) {
 				r.Stats().IP.PacketsDelivered.Increment()
 				// TODO(b/152019344): Send an ICMPv6 Parameter Problem, Code 1 error
 				// in response to unrecognized next header values.
-				e.dispatcher.DeliverTransportPacket(r, p, pkt)
+				switch res := e.dispatcher.DeliverTransportPacket(r, p, pkt); res {
+				case stack.TransportPacketHandled:
+				case stack.TransportPacketDestinationPortUnreachable:
+					// As per RFC 4443 section 3.1:
+					//   A destination node SHOULD originate a Destination Unreachable
+					//   message with Code 4 in response to a packet for which the
+					//   transport protocol (e.g., UDP) has no listener, if that transport
+					//   protocol has no alternative means to inform the sender.
+					_ = returnError(r, &icmpReasonPortUnreachable{}, pkt)
+				default:
+					panic(fmt.Sprintf("unrecognized result from DeliverTransportPacket = %d", res))
+				}
 			}
 
 		default: