From: Thomas Graf <tgraf@redhat.com>
Date: Fri, 23 Jul 2010 15:34:51 -0400
Subject: [net] tcp: htcp last_cong bug fix
Message-id: <20100723153451.GJ14925@lsx.localdomain>
Patchwork-id: 27068
O-Subject: [RHEL5.6 PATCH 8/14] tcp: htcp last_cong bug fix
Bugzilla: 612709
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>

commit 8f65b5354b1a34a536641bd915958662e8af5320
Author: Doug Leith <doug.leith@nuim.ie>
Date:   Wed Nov 12 01:41:09 2008 -0800

    tcp_htcp: last_cong bug fix

    This patch fixes a minor bug in tcp_htcp.c which has been
    highlighted by Lachlan Andrew and Lawrence Stewart.  Currently, the
    time since the last congestion event, which is stored in variable
    last_cong, is reset whenever there is a state change into
    TCP_CA_Open.  This includes transitions of the type
    TCP_CA_Open->TCP_CA_Disorder->TCP_CA_Open which are not associated
    with backoff of cwnd.  The patch changes last_cong to be updated
    only on transitions into TCP_CA_Open that occur after experiencing
    the congestion-related states TCP_CA_Loss, TCP_CA_Recovery,
    TCP_CA_CWR.

    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_htcp.c b/net/ipv4/tcp_htcp.c
index 6edfe5e..01b8dbc 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -67,9 +67,14 @@ static u32 htcp_cwnd_undo(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct htcp *ca = inet_csk_ca(sk);
-	ca->last_cong = ca->undo_last_cong;
-	ca->maxRTT = ca->undo_maxRTT;
-	ca->old_maxB = ca->undo_old_maxB;
+
+	if (ca->undo_last_cong) {
+		ca->last_cong = ca->undo_last_cong;
+		ca->maxRTT = ca->undo_maxRTT;
+		ca->old_maxB = ca->undo_old_maxB;
+		ca->undo_last_cong = 0;
+	}
+
 	return max(tp->snd_cwnd, (tp->snd_ssthresh<<7)/ca->beta);
 }
 
@@ -262,7 +267,10 @@ static void htcp_state(struct sock *sk, u8 new_state)
 	case TCP_CA_Open:
 		{
 			struct htcp *ca = inet_csk_ca(sk);
-			ca->last_cong = jiffies;
+			if (ca->undo_last_cong) {
+				ca->last_cong = jiffies;
+				ca->undo_last_cong = 0;
+			}
 		}
 		break;
 	case TCP_CA_CWR: