svn commit: r347085 - stable/12/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Sat May  4 09:18:19 2019
New Revision: 347085
URL: https://svnweb.freebsd.org/changeset/base/347085

Log:
  MFC r343770:
  Only reduce the PMTU after the send call. The only way to increase it, is
  via PMTUD.
  
  This fixes an MTU issue reported by Timo Voelker.

Modified:
  stable/12/sys/netinet/sctp_output.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/netinet/sctp_output.c
==============================================================================
--- stable/12/sys/netinet/sctp_output.c	Sat May  4 09:15:57 2019	(r347084)
+++ stable/12/sys/netinet/sctp_output.c	Sat May  4 09:18:19 2019	(r347085)
@@ -4287,10 +4287,12 @@ sctp_lowlevel_chunk_output(struct sctp_inpcb *inp,
 						if (net->port) {
 							mtu -= sizeof(struct udphdr);
 						}
-						if ((stcb != NULL) && (stcb->asoc.smallest_mtu > mtu)) {
-							sctp_mtu_size_reset(inp, &stcb->asoc, mtu);
+						if (mtu < net->mtu) {
+							if ((stcb != NULL) && (stcb->asoc.smallest_mtu > mtu)) {
+								sctp_mtu_size_reset(inp, &stcb->asoc, mtu);
+							}
+							net->mtu = mtu;
 						}
-						net->mtu = mtu;
 					}
 				} else if (ro->ro_rt == NULL) {
 					/* route was freed */
@@ -4645,10 +4647,12 @@ sctp_lowlevel_chunk_output(struct sctp_inpcb *inp,
 						if (net->port) {
 							mtu -= sizeof(struct udphdr);
 						}
-						if ((stcb != NULL) && (stcb->asoc.smallest_mtu > mtu)) {
-							sctp_mtu_size_reset(inp, &stcb->asoc, mtu);
+						if (mtu < net->mtu) {
+							if ((stcb != NULL) && (stcb->asoc.smallest_mtu > mtu)) {
+								sctp_mtu_size_reset(inp, &stcb->asoc, mtu);
+							}
+							net->mtu = mtu;
 						}
-						net->mtu = mtu;
 					}
 				} else if (ifp) {
 					if (ND_IFINFO(ifp)->linkmtu &&