From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934950Ab3DGXcl (ORCPT ); Sun, 7 Apr 2013 19:32:41 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46827 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934759Ab3DGXci (ORCPT ); Sun, 7 Apr 2013 19:32:38 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Neal Cardwell" , "Yuchung Cheng" , "David S. Miller" Date: Sun, 07 Apr 2013 23:45:42 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [55/74] tcp: undo spurious timeout after SACK reneging In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:b4b3:7e2a:e2d0:3478 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.43-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Yuchung Cheng [ Upstream commit 7ebe183c6d444ef5587d803b64a1f4734b18c564 ] On SACK reneging the sender immediately retransmits and forces a timeout but disables Eifel (undo). If the (buggy) receiver does not drop any packet this can trigger a false slow-start retransmit storm driven by the ACKs of the original packets. This can be detected with undo and TCP timestamps. Signed-off-by: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/tcp_input.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 1b1f7af..3124e17 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2265,11 +2265,8 @@ void tcp_enter_loss(struct sock *sk, int how) if (tcp_is_reno(tp)) tcp_reset_reno_sack(tp); - if (!how) { - /* Push undo marker, if it was plain RTO and nothing - * was retransmitted. */ - tp->undo_marker = tp->snd_una; - } else { + tp->undo_marker = tp->snd_una; + if (how) { tp->sacked_out = 0; tp->fackets_out = 0; }