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=ham 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 819B7C33CAF for ; Wed, 22 Jan 2020 09:42:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52FB52467B for ; Wed, 22 Jan 2020 09:42:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579686178; bh=H1Lcg5rw+RgdPVHED2wBfHLTyKq6l7C8E9zOH9Hlf1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=KNYNSkM6KjwmPADFw3yVu6jbO3MwA4LeGGzT1xfMUzMC+j50oWPXcXUUlh1jtnwI3 8QCnugdjDJfmEAsq3o20xTjhNsZ5Xgl9CRVD82g6dH0I/L0rv6Vn7UiocYToXEYs7O GHJQsIZL4miD9TfVja57/6wr78lw3t5dmuDZ4IPk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733105AbgAVJm5 (ORCPT ); Wed, 22 Jan 2020 04:42:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:35026 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387795AbgAVJm4 (ORCPT ); Wed, 22 Jan 2020 04:42:56 -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 B0EC624686; Wed, 22 Jan 2020 09:42:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579686175; bh=H1Lcg5rw+RgdPVHED2wBfHLTyKq6l7C8E9zOH9Hlf1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=giCUcAIFGD6gg0oUYgxhj2FHSan9Un2l1fonJ6F2Cdhj47nxgkbWRsn9ADG3dJ+Rt lAXkH4OW9vdCRviBiQQABbGALYUHKVE8Wg9yLXrcBUV1scsHZXqP/vO+yHHq0hr25x U2eZTB8KT2tJ3MFwCbYaSWUNXlgso58DlYnBvu7w= 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 4.19 075/103] tcp: fix marked lost packets not being retransmitted Date: Wed, 22 Jan 2020 10:29:31 +0100 Message-Id: <20200122092814.391579511@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200122092803.587683021@linuxfoundation.org> References: <20200122092803.587683021@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -901,9 +901,10 @@ static void tcp_check_sack_reordering(st /* 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; }