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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72720C2D0DB for ; Wed, 22 Jan 2020 09:36:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4651324687 for ; Wed, 22 Jan 2020 09:36:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579685811; bh=dFYKqZc6dYI9weUBdmlfJSBiQmCkdRyAKsj4+kb9y9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mDORRifnPLT7vBhgfpRGzcU252V+wn2iLi43bUYf6vhz1TQ2jBDb6KnfE4eF3fcL/ m+YjsVloB1A4bSfPfJkG+aax7yZlLSeBP1GxrlbYoyR6sjP7Iqshvn7cK2BIhmM1+h gA+xfmAKa2YNXGF5qRbv7B3x9AmxtNDxUXwRiCdg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732137AbgAVJgt (ORCPT ); Wed, 22 Jan 2020 04:36:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:52342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731991AbgAVJgp (ORCPT ); Wed, 22 Jan 2020 04:36:45 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CA6B424687; Wed, 22 Jan 2020 09:36:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579685804; bh=dFYKqZc6dYI9weUBdmlfJSBiQmCkdRyAKsj4+kb9y9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XOv9N/9PPDFOFYMRwKtsl1nTxpTFT31chRkTGeEjCf+hHjjJ7zMNSig52E4zGtd+U 8ivHyz2Vbh0PueX2uHFMQIoFaLW0s3FnUDcLaBFMsrdWsgY60Jmx2MOHuwMObTIADC BF0biuOBULoUaGGFunpfZgAzoIAnRPKzxizlQYQQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pengcheng Yang , Neal Cardwell , "David S. Miller" Subject: [PATCH 4.9 85/97] tcp: fix marked lost packets not being retransmitted Date: Wed, 22 Jan 2020 10:29:29 +0100 Message-Id: <20200122092809.980970083@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200122092755.678349497@linuxfoundation.org> References: <20200122092755.678349497@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pengcheng Yang [ Upstream commit e176b1ba476cf36f723cfcc7a9e57f3cb47dec70 ] When the packet pointed to by retransmit_skb_hint is unlinked by ACK, retransmit_skb_hint will be set to NULL in tcp_clean_rtx_queue(). If packet loss is detected at this time, retransmit_skb_hint will be set to point to the current packet loss in tcp_verify_retransmit_hint(), then the packets that were previously marked lost but not retransmitted due to the restriction of cwnd will be skipped and cannot be retransmitted. To fix this, when retransmit_skb_hint is NULL, retransmit_skb_hint can be reset only after all marked lost packets are retransmitted (retrans_out >= lost_out), otherwise we need to traverse from tcp_rtx_queue_head in tcp_xmit_retransmit_queue(). Packetdrill to demonstrate: // Disable RACK and set max_reordering to keep things simple 0 `sysctl -q net.ipv4.tcp_recovery=0` +0 `sysctl -q net.ipv4.tcp_max_reordering=3` // Establish a connection +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +.1 < S 0:0(0) win 32792 +0 > S. 0:0(0) ack 1 <...> +.01 < . 1:1(0) ack 1 win 257 +0 accept(3, ..., ...) = 4 // Send 8 data segments +0 write(4, ..., 8000) = 8000 +0 > P. 1:8001(8000) ack 1 // Enter recovery and 1:3001 is marked lost +.01 < . 1:1(0) ack 1 win 257 +0 < . 1:1(0) ack 1 win 257 +0 < . 1:1(0) ack 1 win 257 // Retransmit 1:1001, now retransmit_skb_hint points to 1001:2001 +0 > . 1:1001(1000) ack 1 // 1001:2001 was ACKed causing retransmit_skb_hint to be set to NULL +.01 < . 1:1(0) ack 2001 win 257 // Now retransmit_skb_hint points to 4001:5001 which is now marked lost // BUG: 2001:3001 was not retransmitted +0 > . 2001:3001(1000) ack 1 Signed-off-by: Pengcheng Yang Acked-by: Neal Cardwell Tested-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_input.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -923,9 +923,10 @@ static void tcp_update_reordering(struct /* This must be called before lost_out is incremented */ static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) { - if (!tp->retransmit_skb_hint || - before(TCP_SKB_CB(skb)->seq, - TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) + if ((!tp->retransmit_skb_hint && tp->retrans_out >= tp->lost_out) || + (tp->retransmit_skb_hint && + before(TCP_SKB_CB(skb)->seq, + TCP_SKB_CB(tp->retransmit_skb_hint)->seq))) tp->retransmit_skb_hint = skb; if (!tp->lost_out ||