svn commit: r215926 - stable/7/sys/netinet

Lawrence Stewart lstewart at
Sat Nov 27 03:12:39 UTC 2010

Author: lstewart
Date: Sat Nov 27 03:12:39 2010
New Revision: 215926

  Partially MFC r215166:
  Disable priming the congestion window from the host cache. The current method
  interacts poorly with delayed ack amongst other things, resulting in undesired
  delay during a connection's opening slow start.  Even if we did fix the issues,
  the current method is still dubious at best and needs to be thought through
  Due to a mistake on my behalf, the change described above was committed to head
  as part of a larger patch in revision 215166. Instead of waiting for the MFC of
  215166, I'm merging just this small portion for the upcoming release without
  bringing the mergeinfo for r215166 along. The mergeinfo will sort itself out
  when r215166 is eventually merged.
  This is an intentional direct commit to the 7-STABLE branch.
  Reported by:    Maxim Dounin <mdounin at mdounin ru> and others
  Submitted by:   andre


Modified: stable/7/sys/netinet/tcp_input.c
--- stable/7/sys/netinet/tcp_input.c	Sat Nov 27 02:18:55 2010	(r215925)
+++ stable/7/sys/netinet/tcp_input.c	Sat Nov 27 03:12:39 2010	(r215926)
@@ -2987,10 +2987,14 @@ tcp_mss(struct tcpcb *tp, int offer)
 	 * hostcache when cwnd collapses so next connection doesn't
 	 * overloads the path again.
+	 * XXXAO: Initializing the CWND from the hostcache is broken
+	 * and in its current form not RFC conformant.  It is disabled
+	 * until fixed or removed entirely.
+	 *
 	 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
 	 * We currently check only in syncache_socket for that.
+/* #define TCP_METRICS_CWND */
 	if (metrics.rmx_cwnd)
 		tp->snd_cwnd = max(mss,

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