From f1f4b9579ff536e2997733e1ef8bfb6f76d5a3e3 Mon Sep 17 00:00:00 2001
From: tuexen <tuexen@ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f>
Date: Thu, 24 Nov 2011 17:58:14 +0000
Subject: [PATCH] MFC r227540:

Set the MTU of an path to an approriate value if the interface MTU
can't be determined.

Approved by: re@


git-svn-id: svn://svn.freebsd.org/base/releng/9.0@227943 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
---
 sys/netinet/sctp_pcb.c | 42 ++++++++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/sys/netinet/sctp_pcb.c b/sys/netinet/sctp_pcb.c
index 73dcb5fc..15618b3b 100644
--- a/sys/netinet/sctp_pcb.c
+++ b/sys/netinet/sctp_pcb.c
@@ -4064,13 +4064,8 @@ sctp_add_remote_addr(struct sctp_tcb *stcb, struct sockaddr *newaddr,
 		/* Now get the interface MTU */
 		if (net->ro._s_addr && net->ro._s_addr->ifn_p) {
 			net->mtu = SCTP_GATHER_MTU_FROM_INTFC(net->ro._s_addr->ifn_p);
-		} else {
-			net->mtu = 0;
 		}
-		if (net->mtu == 0) {
-			/* Huh ?? */
-			net->mtu = SCTP_DEFAULT_MTU;
-		} else {
+		if (net->mtu > 0) {
 			uint32_t rmtu;
 
 			rmtu = SCTP_GATHER_MTU_FROM_ROUTE(net->ro._s_addr, &net->ro._l_addr.sa, net->ro.ro_rt);
@@ -4090,11 +4085,31 @@ sctp_add_remote_addr(struct sctp_tcb *stcb, struct sockaddr *newaddr,
 				net->mtu = rmtu;
 			}
 		}
-		if (from == SCTP_ALLOC_ASOC) {
-			stcb->asoc.smallest_mtu = net->mtu;
+	}
+	if (net->mtu == 0) {
+		switch (newaddr->sa_family) {
+#ifdef INET
+		case AF_INET:
+			net->mtu = SCTP_DEFAULT_MTU;
+			break;
+#endif
+#ifdef INET6
+		case AF_INET6:
+			net->mtu = 1280;
+			break;
+#endif
+		default:
+			break;
 		}
-	} else {
-		net->mtu = stcb->asoc.smallest_mtu;
+	}
+	if (net->port) {
+		net->mtu -= (uint32_t) sizeof(struct udphdr);
+	}
+	if (from == SCTP_ALLOC_ASOC) {
+		stcb->asoc.smallest_mtu = net->mtu;
+	}
+	if (stcb->asoc.smallest_mtu > net->mtu) {
+		stcb->asoc.smallest_mtu = net->mtu;
 	}
 #ifdef INET6
 	if (newaddr->sa_family == AF_INET6) {
@@ -4104,12 +4119,7 @@ sctp_add_remote_addr(struct sctp_tcb *stcb, struct sockaddr *newaddr,
 		(void)sa6_recoverscope(sin6);
 	}
 #endif
-	if (net->port) {
-		net->mtu -= sizeof(struct udphdr);
-	}
-	if (stcb->asoc.smallest_mtu > net->mtu) {
-		stcb->asoc.smallest_mtu = net->mtu;
-	}
+
 	/* JRS - Use the congestion control given in the CC module */
 	if (stcb->asoc.cc_functions.sctp_set_initial_cc_param != NULL)
 		(*stcb->asoc.cc_functions.sctp_set_initial_cc_param) (stcb, net);
-- 
2.42.0