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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7ECAFC433EF for ; Wed, 25 May 2022 12:45:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230295AbiEYMpO (ORCPT ); Wed, 25 May 2022 08:45:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230107AbiEYMpN (ORCPT ); Wed, 25 May 2022 08:45:13 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4505C703CF for ; Wed, 25 May 2022 05:45:12 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id D16CCCE1EF2 for ; Wed, 25 May 2022 12:45:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B295AC385B8; Wed, 25 May 2022 12:45:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653482708; bh=pVWwr7+FF8OgYwK7bh8aYLUXHBCmP7TNwC3/yJ24khY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a53vSCs4Fe/JPC+Do+XVkh7KYS3IhLusXANKTpwCgBwFHyZed7VAylTJ/RIFYXCUI xPd4RwdvPrYXXYupym/+NQfUxIY0UQ3x/3N5WiSD0MPGmHqB84LPE9kteTosIgVqHW Ib1EDoe0nmCvSYu/niDPIos+cDsr+f4dvxtU6DW8= Date: Wed, 25 May 2022 14:45:05 +0200 From: Greg KH To: Matthieu Baerts Cc: Mat Martineau , stable@vger.kernel.org, sashal@kernel.org, Paolo Abeni , "David S . Miller" , MPTCP Upstream Subject: Re: [PATCH] mptcp: Do TCP fallback on early DSS checksum failure Message-ID: References: <20220524181041.19543-1-mathew.j.martineau@linux.intel.com> <0648dc99-7465-871c-90a1-8a69f60d893c@tessares.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Wed, May 25, 2022 at 02:36:10PM +0200, Matthieu Baerts wrote: > On 25/05/2022 14:25, Greg KH wrote: > > On Wed, May 25, 2022 at 12:32:04PM +0200, Matthieu Baerts wrote: > >> Hi Greg, Mat, > >> > >> On 25/05/2022 09:51, Greg KH wrote: > >>> On Tue, May 24, 2022 at 11:10:41AM -0700, Mat Martineau wrote: > >>>> [ Upstream commit ae66fb2ba6c3dcaf8b9612b65aa949a1a4bed150 ] > >>>> > >>>> RFC 8684 section 3.7 describes several opportunities for a MPTCP > >>>> connection to "fall back" to regular TCP early in the connection > >>>> process, before it has been confirmed that MPTCP options can be > >>>> successfully propagated on all SYN, SYN/ACK, and data packets. If a peer > >>>> acknowledges the first received data packet with a regular TCP header > >>>> (no MPTCP options), fallback is allowed. > >>>> > >>>> If the recipient of that first data packet finds a MPTCP DSS checksum > >>>> error, this provides an opportunity to fail gracefully with a TCP > >>>> fallback rather than resetting the connection (as might happen if a > >>>> checksum failure were detected later). > >>>> > >>>> This commit modifies the checksum failure code to attempt fallback on > >>>> the initial subflow of a MPTCP connection, only if it's a failure in the > >>>> first data mapping. In cases where the peer initiates the connection, > >>>> requests checksums, is the first to send data, and the peer is sending > >>>> incorrect checksums (see > >>>> https://github.com/multipath-tcp/mptcp_net-next/issues/275), this allows > >>>> the connection to proceed as TCP rather than reset. > >>>> > >>>> Cc: # 5.17.x > >>>> Cc: # 5.15.x > >>>> Fixes: dd8bcd1768ff ("mptcp: validate the data checksum") > >>>> Acked-by: Paolo Abeni > >>>> Signed-off-by: Mat Martineau > >>>> Signed-off-by: David S. Miller > >>>> [mathew.j.martineau: backport: Resolved bitfield conflict in protocol.h] > >>>> Signed-off-by: Mat Martineau > >>>> --- > >>>> > >>>> This patch is already in 5.17.10-rc1 and 5.15.42-rc1, but involves a > >>>> context dependency on upstream commit 4cf86ae84c71 which I have > >>>> requested to be dropped from the stable queues. > >>>> > >>>> I'm posting this backport without the protocol.h conflict to > >>>> (hopefully?) make it easier for the stable maintainers to drop > >>>> 4cf86ae84c71. > >>>> > >>>> For context see https://lore.kernel.org/stable/fa953ec-288f-7715-c6fb-47a222e85270@linux.intel.com/ > >>> > >>> THanks, will take this after this round of releases. > >> > >> It might already be too late but is it possible to have this patch > >> ("mptcp: Do TCP fallback on early DSS checksum failure") and "mptcp: fix > >> checksum byte order" in the same stable release? > >> > >> Note that "mptcp: fix checksum byte order" patch has been recently > >> queued by Sasha at the same time as "mptcp: Do TCP fallback on early DSS > >> checksum failure". > >> > >> A bit of context: "mptcp: fix checksum byte order" fixes an important > >> encoding issue but it also breaks the interoperability with previous > >> Linux versions not having this patch. > >> > >> The patch from Mat ("mptcp: Do TCP fallback on early DSS checksum > >> failure") improves the situation when there is this interoperability > >> issue with a previous Linux versions not implementing the RFC properly. > >> The improvement is there to make the MPTCP connections falling back to > >> TCP instead of resetting them: at least there is a connection. > >> > >> In other words, that would be really nice to have these two commits > >> backported together. If it is easier, it looks best to me to delay the > >> main fix ("mptcp: fix checksum byte order") than having the two patches > >> in different stable versions. But I understand it was not clear and > >> maybe too late to do these modifications. > >> > >> Anyway, thank you for your work maintaining these stable versions! :) > > > > I have already done a release with the first change in it, sorry, but > > have queued this up now. Given that this is fixing a problem with that > > commit, I'll go do a release right now for 5.17 and 5.15. > > I'm sorry for the troubles this is causing you but thank you for doing that! > > Please note that on the bright side, the DSS Checksum feature is > disabled by default so hopefully, this interoperability issue should not > affect too many people. It is hard to quantify but I guess there is no > need to rush if you prefer to wait before doing this release. No worries, it was easy to do a new release, now done! greg k-h