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 CF6C3C433EF for ; Wed, 25 May 2022 12:25:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241046AbiEYMZj (ORCPT ); Wed, 25 May 2022 08:25:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231726AbiEYMZi (ORCPT ); Wed, 25 May 2022 08:25:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 347E16D3AC for ; Wed, 25 May 2022 05:25:37 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 81BFB61711 for ; Wed, 25 May 2022 12:25:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78442C34113; Wed, 25 May 2022 12:25:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653481535; bh=2znGh1s/eVsz7Fjr0CgOkei6MenX44CicFVVkPOfXxE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=saoKls/Fx8b3fgAV9Yu1nyt0HN09NXCU1YYMPxcG9+KD8TdHvHnO4Bt2aU6BW75Mv BmRknH6uukaZjsbt23JyHxV+Nm2E+IP9KJoTP0tlFXYXGnsdztO2boiJGucH8JZ8cS MGbI+ktJoSss1Vn3Y1LtJt8Itzs3qgUr+wmpV380= Date: Wed, 25 May 2022 14:25:32 +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: <0648dc99-7465-871c-90a1-8a69f60d893c@tessares.net> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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. thanks, greg k-h