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Date: Wed, 1 Nov 2017 22:26:23 +0100 From: Willy Tarreau <w@....eu> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, linux@...ck-us.net Cc: Yuchung Cheng <ycheng@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, "David S . Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu> Subject: [PATCH 3.10 082/139] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states From: Yuchung Cheng <ycheng@...gle.com> commit ed254971edea92c3ac5c67c6a05247a92aa6075e upstream. If the sender switches the congestion control during ECN-triggered cwnd-reduction state (CA_CWR), upon exiting recovery cwnd is set to the ssthresh value calculated by the previous congestion control. If the previous congestion control is BBR that always keep ssthresh to TCP_INIFINITE_SSTHRESH, cwnd ends up being infinite. The safe step is to avoid assigning invalid ssthresh value when recovery ends. Signed-off-by: Yuchung Cheng <ycheng@...gle.com> Signed-off-by: Neal Cardwell <ncardwell@...gle.com> Acked-by: Eric Dumazet <edumazet@...gle.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Willy Tarreau <w@....eu> --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 70f217c..828835c 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2554,8 +2554,8 @@ static inline void tcp_end_cwnd_reduction(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */ - if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || - (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) { + if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH && + (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || tp->undo_marker)) { tp->snd_cwnd = tp->snd_ssthresh; tp->snd_cwnd_stamp = tcp_time_stamp; } -- 2.8.0.rc2.1.gbe9624a
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