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From: Michael Tuexen <tuexen@FreeBSD.org>
Date: Sat, 7 Apr 2018 15:16:57 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r332178 - stable/11/sys/netinet
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X-List-Received-Date: Sat, 07 Apr 2018 15:16:58 -0000
Author: tuexen
Date: Sat Apr 7 15:16:57 2018
New Revision: 332178
URL: https://svnweb.freebsd.org/changeset/base/332178
Log:
MFC r322967:
Fix blackhole detection.
There were two bugs related to the blackhole detection:
* The smalles size was tried more than two times.
* The restored MSS was not the original one, but the second
candidate.
Sponsored by: Netflix, Inc.
Modified:
stable/11/sys/netinet/tcp_timer.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/netinet/tcp_timer.c
==============================================================================
--- stable/11/sys/netinet/tcp_timer.c Sat Apr 7 15:10:08 2018 (r332177)
+++ stable/11/sys/netinet/tcp_timer.c Sat Apr 7 15:16:57 2018 (r332178)
@@ -687,19 +687,21 @@ tcp_timer_rexmt(void * xtp)
*/
if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
(TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
- (tp->t_rxtshift >= 2 && tp->t_rxtshift % 2 == 0)) {
+ (tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
+ tp->t_rxtshift % 2 == 0)) {
/*
* Enter Path MTU Black-hole Detection mechanism:
* - Disable Path MTU Discovery (IP "DF" bit).
* - Reduce MTU to lower value than what we
* negotiated with peer.
*/
- /* Record that we may have found a black hole. */
- tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
+ if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
+ /* Record that we may have found a black hole. */
+ tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
+ /* Keep track of previous MSS. */
+ tp->t_pmtud_saved_maxseg = tp->t_maxseg;
+ }
- /* Keep track of previous MSS. */
- tp->t_pmtud_saved_maxseg = tp->t_maxseg;
-
/*
* Reduce the MSS to blackhole value or to the default
* in an attempt to retransmit.
@@ -757,7 +759,7 @@ tcp_timer_rexmt(void * xtp)
* stage (1448, 1188, 524) 2 chances to recover.
*/
if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
- (tp->t_rxtshift > 6)) {
+ (tp->t_rxtshift >= 6)) {
tp->t_flags2 |= TF2_PLPMTU_PMTUD;
tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
tp->t_maxseg = tp->t_pmtud_saved_maxseg;