From: Artem Germanov <agermanov@anchorfree.com>
Date: Wed, 7 Sep 2016 17:49:36 +0000 (-0700)
Subject: tcp: cwnd does not increase in TCP YeAH
X-Git-Tag: firefly_0821_release~176^2~4^2~27^2~68
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=98418550e124ec047918df8b3bb587e60bd39a8a;p=firefly-linux-kernel-4.4.55.git

tcp: cwnd does not increase in TCP YeAH

[ Upstream commit db7196a0d0984b933ccf2cd6a60e26abf466e8a3 ]

Commit 76174004a0f19785a328f40388e87e982bbf69b9
(tcp: do not slow start when cwnd equals ssthresh )
introduced regression in TCP YeAH. Using 100ms delay 1% loss virtual
ethernet link kernel 4.2 shows bandwidth ~500KB/s for single TCP
connection and kernel 4.3 and above (including 4.8-rc4) shows bandwidth
~100KB/s.
   That is caused by stalled cwnd when cwnd equals ssthresh. This patch
fixes it by proper increasing cwnd in this case.

Signed-off-by: Artem Germanov <agermanov@anchorfree.com>
Acked-by: Dmitry Adamushko <d.adamushko@anchorfree.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Holger Hoffstätte <holger@applied-asynchrony.com>
---

diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index 3e6a472e6b88..92ab5bc91592 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -75,7 +75,7 @@ static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 	if (!tcp_is_cwnd_limited(sk))
 		return;
 
-	if (tp->snd_cwnd <= tp->snd_ssthresh)
+	if (tcp_in_slow_start(tp))
 		tcp_slow_start(tp, acked);
 
 	else if (!yeah->doing_reno_now) {