From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuchung Cheng Subject: [PATCH net] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states Date: Tue, 1 Aug 2017 13:22:32 -0700 Message-ID: <20170801202232.162176-1-ycheng@google.com> Cc: netdev@vger.kernel.org, ncardwell@google.com, edumazet@google.com, Yuchung Cheng To: davem@davemloft.net Return-path: Received: from mail-pf0-f176.google.com ([209.85.192.176]:33516 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752025AbdHAUWm (ORCPT ); Tue, 1 Aug 2017 16:22:42 -0400 Received: by mail-pf0-f176.google.com with SMTP id d67so12147105pfc.0 for ; Tue, 01 Aug 2017 13:22:42 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: 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 Signed-off-by: Neal Cardwell --- 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 2920e0cb09f8..dad026fcfd09 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2520,8 +2520,8 @@ static inline void tcp_end_cwnd_reduction(struct sock *sk) return; /* 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_jiffies32; } -- 2.14.0.rc1.383.gd1ce394fe2-goog