linux-kernel - [PATCH 4.4 70/78] tcp: fix under-evaluated ssthresh in TCP Vegas

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Message-Id: <20171222084604.854576933@linuxfoundation.org>
Date:   Fri, 22 Dec 2017 09:46:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hoang Tran <hoang.tran@...ouvain.be>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 70/78] tcp: fix under-evaluated ssthresh in TCP Vegas

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hoang Tran <tranviethoang.vn@...il.com>


[ Upstream commit cf5d74b85ef40c202c76d90959db4d850f301b95 ]

With the commit 76174004a0f19785 (tcp: do not slow start when cwnd equals
ssthresh), the comparison to the reduced cwnd in tcp_vegas_ssthresh() would
under-evaluate the ssthresh.

Signed-off-by: Hoang Tran <hoang.tran@...ouvain.be>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp_vegas.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -158,7 +158,7 @@ EXPORT_SYMBOL_GPL(tcp_vegas_cwnd_event);
 
 static inline u32 tcp_vegas_ssthresh(struct tcp_sock *tp)
 {
-	return  min(tp->snd_ssthresh, tp->snd_cwnd-1);
+	return  min(tp->snd_ssthresh, tp->snd_cwnd);
 }
 
 static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)