happy eyesockets

["Jonathan A. Kollasch" <jakllsch%kollasch.net@localhost>]

Attached is a patch to actually treat ICMP(v6) host/net/port unreachables
during TCP establishment in a way that doesn't cause ~75 second delays
waiting for multiple retransmits to all be reported as unreachable before
actually letting getaddrinfo(3) fall back to the next address.

Linux seems to handle this like this already.

Commitable?

	Jonathan Kollasch

Index: sys/netinet/tcp_subr.c
===================================================================
RCS file: /cvsroot/src/sys/netinet/tcp_subr.c,v
retrieving revision 1.298
diff -d -u -a -p -r1.298 tcp_subr.c
--- sys/netinet/tcp_subr.c	26 Feb 2025 04:49:45 -0000	1.298
+++ sys/netinet/tcp_subr.c	23 Mar 2025 00:01:00 -0000
@@ -1260,6 +1260,10 @@ tcp_notify(struct inpcb *inp, int error)
 	      error == EHOSTDOWN)) {
 		return;
 	} else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 &&
+	    (error == EHOSTUNREACH || error == ENETUNREACH ||
+	     error == ECONNREFUSED)) {
+		so->so_error = error;
+	} else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 &&
 	    tp->t_rxtshift > 3 && tp->t_softerror)
 		so->so_error = error;
 	else