Extract ICMP error sender from UDP

Store transport protocol number on packet buffers for use in ICMP error
generation.

Updates #2211.

PiperOrigin-RevId: 333252762

1 files changed, 11 insertions, 0 deletions

diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 464608dee..fa73cfa47 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -1987,3 +1987,14 @@ func DeleteDanglingEndpoint(e Endpoint) {
 // AsyncLoading is the global barrier for asynchronous endpoint loading
 // activities.
 var AsyncLoading sync.WaitGroup
+
+// ICMPReason is a marker interface for network protocol agnostic ICMP errors.
+type ICMPReason interface {
+	isICMP()
+}
+
+// ICMPReasonPortUnreachable is an error where the transport protocol has no
+// listener and no alternative means to inform the sender.
+type ICMPReasonPortUnreachable struct{}
+
+func (*ICMPReasonPortUnreachable) isICMP() {}