Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754174AbdHKWKI (ORCPT ); Fri, 11 Aug 2017 18:10:08 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33628 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753517AbdHKWCk (ORCPT ); Fri, 11 Aug 2017 18:02:40 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yuchung Cheng , Neal Cardwell , Eric Dumazet , "David S. Miller" Subject: [PATCH 4.4 01/15] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states Date: Fri, 11 Aug 2017 15:02:15 -0700 Message-Id: <20170811220219.500017035@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170811220219.438083791@linuxfoundation.org> References: <20170811220219.438083791@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1507 Lines: 39 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yuchung Cheng [ Upstream commit ed254971edea92c3ac5c67c6a05247a92aa6075e ] 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 Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2503,8 +2503,8 @@ static inline void tcp_end_cwnd_reductio 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; }