From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELuMOMyLeJIQhZSa9/31c8CpH27RQkfTcINndFLi91tIR6qSYMU0pn/HrCZmqnEEMN38TVPR ARC-Seal: i=1; a=rsa-sha256; t=1520451793; cv=none; d=google.com; s=arc-20160816; b=GdWZE7kj/F9c+fbqifrW3nQ298yYOIZuYcc5cjGcMPB1G3Pj1skzw8Vim8rzWyvBHq t2LR/z371/kDCDqZPl7kBpF/Dm1arVXQ/UukbDH2oBuTJuwhlXjq7ZhJYOFeX5FcxokO wqMGbptajXww3aVisSHPxx5S1anbD4mUzjfZXSzlgy6Hy2I8fKd5YFhIcQGwV18nDqbP V+8hNqM/3/ZoDupRAFN4qTAi1Rcdn6TJVTxhW7aKpaIpQ58DA+vz2scyS1GOctqcN6co vvw8sPQp5NYpmCrCvbdMQ+Jz9HCrTpNIkcL1NvzkXtJpiZi3gQ5+SMONSddVDZL9kY4y FoLQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=nw5vl3bevftyBim6zkajlXLsZ3DwDcrbtG9IiFsMifc=; b=JXS3LGu49h7en1STwnR01IpQRFcnYAeB9OoAojLPRHi5KUoypG8BDIxaaFJuln06qW rEZsptCDgL1kWfHn7to8RA3cFFCMVcndONLhpGgIaCnbObWOUUKBdou6X7kL+4DhzqG2 wo+FhjseN0AvR2ebfJyDQcnjmBaWd6AshWkawRcxR+tqBLXdAWvTu64TTBDWQ8Fzwuha dxTRo5pgGgTvKAFsvGRChFh8cttTdFFP5mtfNq83BI/lovTRSXMvbhdMErJrUYPm6+8J 2+FG6OnRIt5jebHNk4DdvdxwLvmtPB6eOk2so23TnzXaUurQXd3Id2Wbb2Yet75MQlxY /Eqg== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 185.236.200.248 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 185.236.200.248 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Teodor Milkov , Yuchung Cheng , Neal Cardwell , "David S. Miller" Subject: [PATCH 4.15 096/122] tcp: revert F-RTO middle-box workaround Date: Wed, 7 Mar 2018 11:38:28 -0800 Message-Id: <20180307191743.245437591@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180307191729.190879024@linuxfoundation.org> References: <20180307191729.190879024@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1594309259230127880?= X-GMAIL-MSGID: =?utf-8?q?1594309259230127880?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yuchung Cheng [ Upstream commit d4131f09770d9b7471c9da65e6ecd2477746ac5c ] This reverts commit cc663f4d4c97b7297fb45135ab23cfd508b35a77. While fixing some broken middle-boxes that modifies receive window fields, it does not address middle-boxes that strip off SACK options. The best solution is to fully revert this patch and the root F-RTO enhancement. Fixes: cc663f4d4c97 ("tcp: restrict F-RTO to work-around broken middle-boxes") Reported-by: Teodor Milkov Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_input.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 45f750e85714..50963f92a67d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1915,7 +1915,6 @@ void tcp_enter_loss(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); struct net *net = sock_net(sk); struct sk_buff *skb; - bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery; bool is_reneg; /* is receiver reneging on SACKs? */ bool mark_lost; @@ -1974,17 +1973,15 @@ void tcp_enter_loss(struct sock *sk) tp->high_seq = tp->snd_nxt; tcp_ecn_queue_cwr(tp); - /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous - * loss recovery is underway except recurring timeout(s) on - * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing - * - * In theory F-RTO can be used repeatedly during loss recovery. - * In practice this interacts badly with broken middle-boxes that - * falsely raise the receive window, which results in repeated - * timeouts and stop-and-go behavior. + /* F-RTO RFC5682 sec 3.1 step 1 mandates to disable F-RTO + * if a previous recovery is underway, otherwise it may incorrectly + * call a timeout spurious if some previously retransmitted packets + * are s/acked (sec 3.2). We do not apply that retriction since + * retransmitted skbs are permanently tagged with TCPCB_EVER_RETRANS + * so FLAG_ORIG_SACK_ACKED is always correct. But we do disable F-RTO + * on PTMU discovery to avoid sending new data. */ tp->frto = net->ipv4.sysctl_tcp_frto && - (new_recovery || icsk->icsk_retransmits) && !inet_csk(sk)->icsk_mtup.probe_size; } -- 2.14.3