svn commit: r314155 - head/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Thu Feb 23 18:14:36 2017
New Revision: 314155
URL: https://svnweb.freebsd.org/changeset/base/314155

Log:
  TCP window updates are only sent if the window can be increased by at
  least 2 * MSS. However, if the receive buffer size is small, this might
  be impossible. Add back a criterion to send a TCP window update if
  the window can be increased by at least half of the receive buffer size.
  This condition was removed in r242252. This patch simply brings it back.
  PR:			211003
  Reviewed by:		gnn
  MFC after:		1 week
  Sponsored by:		Netflix, Inc.
  Differential Revision:	https://reviews.freebsd.org/D9475

Modified:
  head/sys/netinet/tcp_output.c

Modified: head/sys/netinet/tcp_output.c
==============================================================================
--- head/sys/netinet/tcp_output.c	Thu Feb 23 17:56:24 2017	(r314154)
+++ head/sys/netinet/tcp_output.c	Thu Feb 23 18:14:36 2017	(r314155)
@@ -696,6 +696,8 @@ after_sack_rexmit:
 		     recwin <= (so->so_rcv.sb_hiwat / 8) ||
 		     so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
 			goto send;
+		if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat)
+			goto send;
 	}
 dontupdate: