From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D72CE200A5 for ; Mon, 6 Nov 2023 13:06:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1FnslwhV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 520F6C433C8; Mon, 6 Nov 2023 13:06:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699275966; bh=l4MxhmhEWiMLs+LbkvR3wAlC/H2pdSFYpuoNNjsLPyA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1FnslwhVhOsHAjfz/iy697nCn6RF/RGh10acIYHOO6hmypHGXZngXUwXJluhvOZkP FIZnSielX6eU203AbfSf2c8MYNR+kt/QLzrO6INu6F+d0VxtGIm7wLlxF4OWtmaGm2 8s+OwI/ots97GZuXV6x3X08wM6pm7RWfFPBQyX4U= 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 4.14 07/48] tcp: fix wrong RTO timeout when received SACK reneging Date: Mon, 6 Nov 2023 14:02:58 +0100 Message-ID: <20231106130258.109864930@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106130257.862199836@linuxfoundation.org> References: <20231106130257.862199836@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.14-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 491c16d8e9ddc..e65daf71a52d7 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2069,16 +2069,17 @@ 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; @@ -2870,7 +2871,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked, 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