From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B90B932570D for ; Mon, 12 Oct 2026 13:28:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791811732; cv=none; b=r2hfHAWtkMmePxk0aaWlCP/HqFwDzhFPomyUCTUBYHzFhtP9y3/BImgyCHLXYDbDnOi1BM1mruFrIAw4xCFMdmVer3IiFPUczS7rgDIiYwa+7iDICBAySZ52dYV6D7Ibkn4182gm5X52LTApN8A1KHXfF601IkjfV/GVdakbRvo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791811732; c=relaxed/simple; bh=+IR7rUBKXwZcd8Lj3UMr+KmJXKrL5fJwUDv9YtZBe38=; h=Message-ID:Date:MIME-Version:Subject:To:References:From:Cc: In-Reply-To:Content-Type; b=SVAzb9p0R+cBoqm1wAk0Rx94R31aM6YyODAUfBI7wyBbbtrlXNOP/QwgxNKeo5QIt/CfbggnHCdxVNCs+ID5iG5o/C4iBCJK/R2TFhR4AlmD5WDX/Ez3JQEoSJGYQzU+068krXnCFG4soeCw7087WfE620296ztE0dNWItewV0Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fv8/ErW2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fv8/ErW2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88D771F0089B; Mon, 12 Oct 2026 13:28:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791811731; bh=QYAY+zkeNWacH9t661vnDnRJgy5aywGDi+e4lgDEUjo=; h=Date:Subject:To:References:From:Cc:In-Reply-To; b=fv8/ErW2QAc0ZjQa4zpNFpAON4/rCC7FXxEmfM9IlsBnmEmEo45tydfJNAYa4HDcU W6EFl0orTaj3Jhxi09RWMm5ktVBbXFWrFSBY2OkHBovNKVRDrqw5Y74Eja2Rz39i+2 3KjNcrTZCiDilcOX3Tf+m/F1bcuwyv+QDENisbYPAMJmvu3BJybXRZXDXMumLV4UKb TWkKneoDTGmYZ8PDnjePrA21PnFnF0mvDionQCRTUOQarRZQS8b5QHB6CRj9whIn5q hIwFaexv3Gl6Kbp7RJynLcZCByxbXe10ZHeTfRdng90An9O+sU1nCTNPiP86JanxGT T2itYMn6XF/TA== Message-ID: Date: Mon, 12 Oct 2026 15:28:48 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH v4] mptcp: push queued data on passive TFO subflows becoming established Content-Language: fr To: T S RAMESHKUMAR References: <20261008121602.206507-1-rameshkumar.t@phytecembedded.in> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi T S, +cc Petar. On 12/10/2026 12:00, T S RAMESHKUMAR wrote: > Hi Matt, Petar, > > Thank you both! > > I have prepared [PATCH mptcp-net v2] based on the export branch. > In v2: > - Reverted bitfield modifications: check_fully_established() is only > called once upon receiving the MPC 3rd-ACK, so is_mptfo is read-only at > that stage and safe from concurrency races. > - Added "Suggested-by: Petar Sakic " and > "Reported-by: Petar Sakic ". > - Kept the Fixes tag pointing to fb7084501a61 ("mptcp: add support for > TCP_FASTOPEN sockopt") to ensure backports cover 6.8 and all stable trees. Thank you. I will try to review this after the automated tests. > Regarding Packetdrill: > I have prepared the packetdrill test case (server-TCP_FASTOPEN-early- > write.pkt) which simulates the server writing data in SYN_RECV before > the 3rd ACK arrives and verifies that the 100 bytes are pushed > immediately with DSS mapping once the 3rd ACK is received. All 51 > fastopen tests pass. > > I can submit the packetdrill test via a PR on https://github.com/ > multipath-tcp/packetdrill packetdrill>, or send it directly to the list if preferred. Here is the > test script for reference: Please open a new PR. > --- server-TCP_FASTOPEN-early-write.pkt --- > // SPDX-License-Identifier: GPL-2.0 > // Test MPTCP passive Fast Open early write before 3rd ACK arrives > --tolerance_usecs=100000 > `../common/defaults.sh` > >  0.0    socket(..., SOCK_STREAM, IPPROTO_MPTCP) = 3 > +0.0    setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 > +0.0    setsockopt(3, SOL_TCP, TCP_FASTOPEN, [2], 4) = 0 > > +0.0    bind(3, ..., ...) = 0 > +0.0    listen(3, 1) = 0 > > // Client connects with TFO Cookie and 500 bytes of SYN data > +0.1      <  S   0:500(500)                win 65535   TS val 100 ecr 0,   nop, wscale 8, FO TFO_COOKIE, nop, nop, mpcapable v1 > flags[flag_h] nokey> > +0.0      >  S.  0:0(0)          ack 501               TS val 100 ecr 100, nop, wscale 8,                          mpcapable v1 > flags[flag_h] key[skey]> > > // Server accepts while still in SYN_RECV and reads the SYN data > +0.0    accept(3, ..., ...) = 4 > +0.0    read(4, ..., 500) = 500 > > // Server writes early reply data before receiving client's 3rd ACK > +0.0    write(4, ..., 100) = 100 > > // Client's 3rd ACK arrives with no data, establishing the MPTCP connection > +0.2      <   .  501:501(0)      ack 1     win 450    <                 >                                                              mpcapable > v1 flags[flag_h] key[ckey, skey]> Here, you are dropping TCP Timestamps (TS) negotiated before. Probably better to keep it (or you don't inject it in he first SYN, clearer). > // Server must immediately push the queued 100 bytes with DSS mapping > +0.0      >  P.  1:101(100)      ack 501               100 ecr 100, dss dack8=0 dsn8=1 ssn=1 dll=100 nocs> "dack8=0"? That's strange... Also, TCP options are not padded correctly to ensure TCP header is a multiple of 4 bytes: 2 excess bytes → you are missing two "nop" at the end. How did you test it? $ cd /gtests/net $ run_all.py -lv mptcp/fastopen/server-TCP_FASTOPEN-early-write.pkt Don't forget to add the "Assisted-by: LLM" tag if used, and mention what you did, how you tested things. You can use this docker image to ease the testing part: https://github.com/multipath-tcp/mptcp-upstream-virtme-docker Cheers, Matt -- Sponsored by the NGI0 Core fund.