From d28b9e89a9cbb9f62dc842ba71595ea8bd30788b Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 4 Feb 2011 14:13:15 +0000
Subject: [PATCH] When turning off TCP_NOPUSH, only call tcp_output() to
 immediately flush any pending data if the connection is established.

Submitted by:	csjp
Reviewed by:	lstewart
MFC after:	1 week
---
 sys/netinet/tcp_usrreq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index b2fce82d629..6acf9dad83c 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -1328,9 +1328,10 @@ tcp_ctloutput(struct socket *so, struct sockopt *sopt)
 			INP_WLOCK_RECHECK(inp);
 			if (optval)
 				tp->t_flags |= TF_NOPUSH;
-			else {
+			else if (tp->t_flags & TF_NOPUSH) {
 				tp->t_flags &= ~TF_NOPUSH;
-				error = tcp_output(tp);
+				if (TCPS_HAVEESTABLISHED(tp->t_state))
+					error = tcp_output(tp);
 			}
 			INP_WUNLOCK(inp);
 			break;