svn commit: r319397 - stable/11/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Thu Jun  1 08:19:45 2017
New Revision: 319397
URL: https://svnweb.freebsd.org/changeset/base/319397

Log:
  MFC r314155:
  
  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
  Differential Revision:	https://reviews.freebsd.org/D9475

Modified:
  stable/11/sys/netinet/tcp_output.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet/tcp_output.c
==============================================================================
--- stable/11/sys/netinet/tcp_output.c	Thu Jun  1 08:15:33 2017	(r319396)
+++ stable/11/sys/netinet/tcp_output.c	Thu Jun  1 08:19:45 2017	(r319397)
@@ -688,6 +688,8 @@ after_sack_rexmit:
 		     recwin <= (long)(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: