From: Thomas Graf <tgraf@redhat.com>
Date: Fri, 23 Jul 2010 15:37:40 -0400
Subject: [net] tcp: tcp_vegas ssthresh bug fix
Message-id: <20100723153740.GP14925@lsx.localdomain>
Patchwork-id: 27074
O-Subject: [RHEL5.6 PATCH 14/14] tcp: tcp_vegas ssthresh bug fix
Bugzilla: 612709
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>

commit a6af2d6ba5797c556fba0cd3a19e5f3bc9a99b76
Author: Doug Leith <doug.leith@nuim.ie>
Date:   Thu Dec 4 17:17:18 2008 -0800

    tcp: tcp_vegas ssthresh bug fix

    This patch fixes a bug in tcp_vegas.c.  At the moment this code leaves
    ssthresh untouched.  However, this means that the vegas congestion
    control algorithm is effectively unable to reduce cwnd below the
    ssthresh value (if the vegas update lowers the cwnd below ssthresh,
    then slow start is activated to raise it back up).  One example where
    this matters is when during slow start cwnd overshoots the link
    capacity and a flow then exits slow start with ssthresh set to a value
    above where congestion avoidance would like to adjust it.

    Signed-off-by: Doug Leith <doug.leith@nuim.ie>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index d497f83..8a57a56 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -264,6 +264,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack,
 				tp->snd_cwnd = 2;
 			else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
 				tp->snd_cwnd = tp->snd_cwnd_clamp;
+
+			tp->snd_ssthresh = tcp_current_ssthresh(sk);
 		}
 
 		/* Wipe the slate clean for the next RTT. */