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tcp: fix infinite cwnd in tcp_complete_cwr()

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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>
This commit is contained in:
Yuchung Cheng 2012-04-30 06:00:18 +00:00 committed by David S. Miller
parent 05be18241e
commit 1cebce36d6
1 changed files with 6 additions and 3 deletions
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9
net/ipv4/tcp_input.c
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@ -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);
}