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From 6b142c33b94fd1c35b6a19be0982ae408ce8d162 Mon Sep 17 00:00:00 2001
From: Yuchung Cheng <ycheng@google.com>
Date: Mon, 30 Apr 2012 06:00:18 +0000
Subject: [PATCH 18/56] tcp: fix infinite cwnd in tcp_complete_cwr()
[ Upstream commit 1cebce36d660c83bd1353e41f3e66abd4686f215 ]
When the cwnd reduction is done, ssthresh may be infinite
if TCP enters CWR via ECN or F-RTO. If cwnd is not undone, i.e.,
undo_marker is set, tcp_complete_cwr() falsely set cwnd to the
infinite ssthresh value. The correct operation is to keep cwnd
intact because it has been updated in ECN or F-RTO.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/tcp_input.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index daedc07..db07c9e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2868,11 +2868,14 @@ static inline void tcp_complete_cwr(struct sock *sk)
/* Do not moderate cwnd if it's already undone in cwr or recovery. */
if (tp->undo_marker) {
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR)
+ if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
- else /* PRR */
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ } else if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH) {
+ /* PRR algorithm. */
tp->snd_cwnd = tp->snd_ssthresh;
- tp->snd_cwnd_stamp = tcp_time_stamp;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ }
}
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
}
--
1.7.7.6
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