netdev - [PATCH] tcp: tcp_process_frto() should not set snd

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Date:	Sat, 02 Feb 2013 07:14:35 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Pasi Kärkkäinen <pasik@....fi>,
	David Miller <davem@...emloft.net>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev@...r.kernel.org, Neal Cardwell <ncardwell@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH] tcp: tcp_process_frto() should not set snd_cwnd to 0

From: Eric Dumazet <edumazet@...gle.com>

snd_cwnd minimal value is 1, not 0, or tcp_slow_start()
is broken : infinite loop since commit 9dc274151a548
(tcp: fix ABC in tcp_slow_start())

A separate patch will make tcp_slow_start() more robust.

Reported-by: Pasi Kärkkäinen <pasik@....fi>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
Cc: Yuchung Cheng <ycheng@...gle.com>
---
 net/ipv4/tcp_input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8aca4ee..37760df 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3506,7 +3506,7 @@ static bool tcp_process_frto(struct sock *sk, int flag)
 		if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) {
 			/* Prevent sending of new data. */
 			tp->snd_cwnd = min(tp->snd_cwnd,
-					   tcp_packets_in_flight(tp));
+					   max(tcp_packets_in_flight(tp), 1U));
 			return true;
 		}
 


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