From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A048C4332F for ; Mon, 6 Nov 2023 13:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232438AbjKFNWS (ORCPT ); Mon, 6 Nov 2023 08:22:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232431AbjKFNWR (ORCPT ); Mon, 6 Nov 2023 08:22:17 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17B35A9 for ; Mon, 6 Nov 2023 05:22:15 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 555BDC433C7; Mon, 6 Nov 2023 13:22:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699276934; bh=c5xDF9uDEd+IYBrffuSZT1wMjf14r/4fPEjQXguxRgc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mGXYtqzwAjH92hpAerFGeNG+Pi6LJ6qRzfiqwItoGtnrO4UKAprG5dD9Kvyy5aPrw ymhwaYhhTP47QBme513y1MCq8Xal/8eTgAGWgVWkU/kMlACBrEHhpMDWGGMOC5hObY qr+DXkn6r6m4c1Bx1y/JjJkdXdMcIqtzd6hjT9Gs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fred Chen , Neal Cardwell , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 17/74] tcp: fix wrong RTO timeout when received SACK reneging Date: Mon, 6 Nov 2023 14:03:37 +0100 Message-ID: <20231106130302.302397789@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106130301.687882731@linuxfoundation.org> References: <20231106130301.687882731@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fred Chen [ Upstream commit d2a0fc372aca561556e765d0a9ec365c7c12f0ad ] This commit fix wrong RTO timeout when received SACK reneging. When an ACK arrived pointing to a SACK reneging, tcp_check_sack_reneging() will rearm the RTO timer for min(1/2*srtt, 10ms) into to the future. But since the commit 62d9f1a6945b ("tcp: fix TLP timer not set when CA_STATE changes from DISORDER to OPEN") merged, the tcp_set_xmit_timer() is moved after tcp_fastretrans_alert()(which do the SACK reneging check), so the RTO timeout will be overwrited by tcp_set_xmit_timer() with icsk_rto instead of 1/2*srtt. Here is a packetdrill script to check this bug: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 // simulate srtt to 100ms +0 < S 0:0(0) win 32792 +0 > S. 0:0(0) ack 1 +.1 < . 1:1(0) ack 1 win 1024 +0 accept(3, ..., ...) = 4 +0 write(4, ..., 10000) = 10000 +0 > P. 1:10001(10000) ack 1 // inject sack +.1 < . 1:1(0) ack 1 win 257 +0 > . 1:1001(1000) ack 1 // inject sack reneging +.1 < . 1:1(0) ack 1001 win 257 // we expect rto fired in 1/2*srtt (50ms) +.05 > . 1001:2001(1000) ack 1 This fix remove the FLAG_SET_XMIT_TIMER from ack_flag when tcp_check_sack_reneging() set RTO timer with 1/2*srtt to avoid being overwrited later. Fixes: 62d9f1a6945b ("tcp: fix TLP timer not set when CA_STATE changes from DISORDER to OPEN") Signed-off-by: Fred Chen Reviewed-by: Neal Cardwell Tested-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv4/tcp_input.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index ec3c23adbab44..c3f227c4c3567 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2057,16 +2057,17 @@ void tcp_enter_loss(struct sock *sk) * restore sanity to the SACK scoreboard. If the apparent reneging * persists until this RTO then we'll clear the SACK scoreboard. */ -static bool tcp_check_sack_reneging(struct sock *sk, int flag) +static bool tcp_check_sack_reneging(struct sock *sk, int *ack_flag) { - if (flag & FLAG_SACK_RENEGING && - flag & FLAG_SND_UNA_ADVANCED) { + if (*ack_flag & FLAG_SACK_RENEGING && + *ack_flag & FLAG_SND_UNA_ADVANCED) { struct tcp_sock *tp = tcp_sk(sk); unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4), msecs_to_jiffies(10)); inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, delay, TCP_RTO_MAX); + *ack_flag &= ~FLAG_SET_XMIT_TIMER; return true; } return false; @@ -2840,7 +2841,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una, tp->prior_ssthresh = 0; /* B. In all the states check for reneging SACKs. */ - if (tcp_check_sack_reneging(sk, flag)) + if (tcp_check_sack_reneging(sk, ack_flag)) return; /* C. Check consistency of the current state. */ -- 2.42.0