Date: Mon, 28 Aug 2017 11:41:18 +0000 (UTC) From: Michael Tuexen <tuexen@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r322967 - head/sys/netinet Message-ID: <201708281141.v7SBfItt011158@repo.freebsd.org>
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Author: tuexen Date: Mon Aug 28 11:41:18 2017 New Revision: 322967 URL: https://svnweb.freebsd.org/changeset/base/322967 Log: 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. MFC after: 1 week Sponsored by: Netflix, Inc. Modified: head/sys/netinet/tcp_timer.c Modified: head/sys/netinet/tcp_timer.c ============================================================================== --- head/sys/netinet/tcp_timer.c Mon Aug 28 10:02:47 2017 (r322966) +++ head/sys/netinet/tcp_timer.c Mon Aug 28 11:41:18 2017 (r322967) @@ -726,19 +726,21 @@ 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. @@ -796,7 +798,7 @@ 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;
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