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From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 6 Nov 2009 16:55:05 +0000 (UTC)
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Subject: svn commit: r198990 - head/sys/netinet
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Author: jhb
Date: Fri Nov  6 16:55:05 2009
New Revision: 198990
URL: http://svn.freebsd.org/changeset/base/198990

Log:
  Several years ago a feature was added to TCP that casued soreceive() to
  send an ACK right away if data was drained from a TCP socket that had
  previously advertised a zero-sized window.  The current code requires the
  receive window to be exactly zero for this to kick in.  If window scaling is
  enabled and the window is smaller than the scale, then the effective window
  that is advertised is zero.  However, in that case the zero-sized window
  handling is not enabled because the window is not exactly zero.  The fix
  changes the code to check the raw window value against zero.
  
  Reviewed by:	bz
  MFC after:	1 week

Modified:
  head/sys/netinet/tcp_output.c

Modified: head/sys/netinet/tcp_output.c
==============================================================================
--- head/sys/netinet/tcp_output.c	Fri Nov  6 15:24:48 2009	(r198989)
+++ head/sys/netinet/tcp_output.c	Fri Nov  6 16:55:05 2009	(r198990)
@@ -992,7 +992,7 @@ send:
 	 * to read more data than can be buffered prior to transmitting on
 	 * the connection.
 	 */
-	if (recwin == 0)
+	if (th->th_win == 0)
 		tp->t_flags |= TF_RXWIN0SENT;
 	else
 		tp->t_flags &= ~TF_RXWIN0SENT;