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=-11.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 59AEFC4360F for ; Wed, 3 Apr 2019 15:52:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1ADBC206BA for ; Wed, 3 Apr 2019 15:52:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="WCrErmxY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727403AbfDCPwO (ORCPT ); Wed, 3 Apr 2019 11:52:14 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:39439 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbfDCPwO (ORCPT ); Wed, 3 Apr 2019 11:52:14 -0400 Received: by mail-wr1-f68.google.com with SMTP id j9so22076938wrn.6 for ; Wed, 03 Apr 2019 08:52:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=m7qplqu/2+oy26DB0Pm6tiDZFg+/RROap+cgmPWZPC8=; b=WCrErmxYI+LrXDFsd+5LvTzh9uDixA+IxHshBjviGKEfGfnqqEengQsRlj01EY+UNL wjvakVt+zUba41q0DCxNrSQ4A/5zcHIUeztvjyA5/CY/g2I/hKjQpAunt04p/2xZJu81 yNT3f2pz4+0H1ToVCdCyHo9g56lYNuer5atl2hUeADGRk46i2BFqGYYje9SiS8MwSG0x w5rwDHiGkZMoMjX0eOWf0avt53qNXYjJ5wD+l5TZwyeYoAyQ9vi246mmSuKA9k/hjLrr 2FblCmMD+NjxOXEHpEcLLRPVxCHOh4uGD5xNWZ7Vy7x8JjwgpzHtf17YQzK5p5QzaDIx tfdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=m7qplqu/2+oy26DB0Pm6tiDZFg+/RROap+cgmPWZPC8=; b=sCTySI01dnDojNw14V0+zMkkaZoD7wvObPBlughXB4SS/7RtlxPiOOVLIcOJQVK88G pTTGNJVsqkOLn4OFXuCUUrsmcUMH5vnyj9IG465uIgaZGZeER50ZWSd83hDWs1qgiFtb OiP3Yy2P8XD+my/6zuvdksElvBeKebcXhJlSJkTCfLxan5MsDS2trvD6dEYKLwEX13N7 PIh2uKkygp9DFrT2HW+fF8ayeNTg1/qiW+SKNOnZ4RYY5KGpzIzDndF0Y4np2Mof3hOZ Lh7yM0VZr2fynIzJbsZSJC2Qbk5LzACRGRYfEorOe1q3ote3qpjxghbc+rXNKDZuQ4ZH cNXA== X-Gm-Message-State: APjAAAUc5wOyflJvfHxqGgL989zXdS5stEctEKJb1lkDa31NDRuqwXV3 IOthtPmbjcnn7rdGnkknPhqug3eYdaUSMv0ZRYRuiQ== X-Google-Smtp-Source: APXvYqzuf0bnJVTeRGST9QEGrXNaCv0YJpyYQSmpz+mZTZTXSGlCyz5zX9Qv8HXWVBHDdom1zOW1h4HHDQ7p7XrqQCo= X-Received: by 2002:adf:f8c1:: with SMTP id f1mr169928wrq.151.1554306732143; Wed, 03 Apr 2019 08:52:12 -0700 (PDT) MIME-Version: 1.0 References: <20190403134915.6616-1-olivier.tilmans@nokia-bell-labs.com> In-Reply-To: From: Yuchung Cheng Date: Wed, 3 Apr 2019 08:51:35 -0700 Message-ID: Subject: Re: [PATCH net-next] tcp: Accept ECT on SYN in the presence of RFC8311 To: Neal Cardwell Cc: "Tilmans, Olivier (Nokia - BE/Antwerp)" , Bob Briscoe , "De Schepper, Koen (Nokia - BE/Antwerp)" , Eric Dumazet , "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 3, 2019 at 8:39 AM Neal Cardwell wrote: > > On Wed, Apr 3, 2019 at 9:50 AM Tilmans, Olivier (Nokia - BE/Antwerp) > wrote: > > > > Linux currently disable ECN for incoming connections when the SYN > > requests ECN and the IP header has ECT(0)/ECT(1) set, as some > > networks were reportedly mangling the ToS byte, hence could later > > trigger false congestion notifications. > > > > RFC8311 =C2=A74.3 relaxes RFC3168's requirements such that ECT can be s= et > > one TCP control packets (including SYNs). The main benefit of this > > is the decreased probability of losing a SYN in a congested > > ECN-capable network (i.e., it avoids the initial 1s timeout). > > Additionally, this allows the development of newer TCP extensions, > > such as AccECN. > > > > This patch relaxes the previous check, by enabling ECN on incoming > > connections using SYN+ECT if at least one bit of the reserved flags > > of the TCP header is set. Such bit would indicate that the sender of > > the SYN is using a newer TCP feature than what the host implements, > > such as AccECN, and is thus implementing RFC8311. This enables > > end-hosts not supporting such extensions to still negociate ECN, and > > to have some of the benefits of using ECN on control packets. > > > > Signed-off-by: Olivier Tilmans > > Suggested-by: Bob Briscoe > > Cc: Koen De Schepper > > Acked-by: Neal Cardwell Acked-by: Yuchung Cheng > > Thank you for this patch, Olivier and Bob. > > thanks, > neal