Author: andre
Date: Fri Jul 30 21:45:53 2010
New Revision: 210666
URL: http://svn.freebsd.org/changeset/base/210666
Log:
Fix a bug in syncache where the initial CWND for new incoming connections
was limited to one segment under the faulty assumption of a retransmit.
Due to this the opportunity to initialize the increased congestion window
according to RFC3390 was missed.
Support for RFC3465 introduced in r187289 uncovered the bug as the ACK
to SYN/ACK no longer caused snd_cwnd increase by MSS (actually, this
increase shouldn't happen as it's explicitly forbidden by RFC3390, but
it's another issue). Snd_cwnd remains really small (1*MSS + 1) and this
causes really bad interaction with delayed acks on other side.
The variable name sc_rxmits is a bit misleading as it counts all transmits,
not just retransmits.
Submitted by: Maxim Dounin <mdounin-at-mdounin-dot-ru>
MFC after: 10 days
Modified:
head/sys/netinet/tcp_syncache.c
Modified: head/sys/netinet/tcp_syncache.c
==============================================================================
--- head/sys/netinet/tcp_syncache.c Fri Jul 30 21:39:28 2010
(r210665)
+++ head/sys/netinet/tcp_syncache.c Fri Jul 30 21:45:53 2010
(r210666)
@@ -804,8 +804,9 @@ syncache_socket(struct syncache *sc, str
/*
* If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
+ * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
*/
- if (sc->sc_rxmits)
+ if (sc->sc_rxmits > 1)
tp->snd_cwnd = tp->t_maxseg;
tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
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