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 ABA0F3D45FE for ; Sun, 20 Sep 2026 06:29:07 +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=1789885748; cv=none; b=qj/8r2/d3l+Bw++O/cTVix9YjmjMq5wyCYvzDtEJNu+qBU3vuITscOjjTYD1TKCe6MdF7Pnr1s0S+B8Mgl1+lXGoT7qtWH3UEnTJiXgP/AIon+OnOfM4uPUHB9XMZZQUFYvnIphAfSaYM/iPWnOp0MlYzyeTp1MIrNtiwpzs9Bk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789885748; c=relaxed/simple; bh=4/jtPHCZHyVSfIwUWmxPsqMcBinJzwyy1yOg7ergpB4=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=GGd3oGiy99KK1hdPQv3nX/DaoP9uQVHcfTTIvTOcuu2d7dY9W5jjYP1HLxH4gqaI0QSF0i7TCx+GFcIq8jzXoBiCcCc2QKzyPyzfWy8AkDH6yRfIJHx9kNqO9ya3K3gt1fI8t7dvHbcYETVam6hdA7kEwK4HSNPekER1jfthHBE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HUFnhea8; 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="HUFnhea8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21C3B1F000FF; Sun, 20 Sep 2026 06:29:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789885747; bh=XZQVgV7G4cs538b30n9W2qqR3XfB237DH3rsa/dqrek=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=HUFnhea8oQgGNfjBYJiu/IK9u2zM1ZUXexd7K9bVUynmBC+DBS0lStaW/BnyeeyqE COv8lJakLKwEvOYs+8K5KR4SfOiEOHjPTSvxlhITZZOZTcJ8hY60UuXE/eC4hgGeKC aFY99n+3CyDxg2Feag/Vn4GhC1qiTQgdsWk4dQsRAAC0OnrJrZqAHwpxGGSKW69th6 O4g4lFl2t9yZeD6FiIJhCj7uqwOhWbCgoLF0WcvO0Sf7SLShGdQrqiarLwchltQnTg pr7lg7K6FlJndPJ5xezdo2NFLloNFebi5z0D5bdFMf+9GM//8R2qvhJygyo4MpBrWt 7jDWbQJ0jzfEw== From: sashiko-bot@kernel.org Subject: Re: [PATCH v3] mptcp: do not use Fast Open on MP_JOIN subflows Reply-To: sashiko-reviews@lists.linux.dev To: "Yilin Zhang" Cc: mptcp@lists.linux.dev In-Reply-To: <20260920061904.3575780-1-yilinzhang@moonshot.ai> References: <20260903094010.4066892-1-yilinzhang@moonshot.ai> <20260920061904.3575780-1-yilinzhang@moonshot.ai> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 20 Sep 2026 06:29:06 +0000 Message-Id: <20260920062907.21C3B1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [Medium] mptcp: disabled TCP timestamps on MP_JOIN with TFO due to wrong = logic order -- commit 7c8131d455e6d16e5fa896b1f57ebf371c13798d Author: Yilin Zhang mptcp: do not use Fast Open on MP_JOIN subflows This commit disables TCP Fast Open on MP_JOIN subflows, as data on a subflow requires a completed HMAC exchange. It updates the SYN processing path to fallback to a regular handshake and strips the TFO cookie from MP_JOIN SYN/ACKs. > diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c > index f0a6725d2c376..7bf94aea5f681 100644 > --- a/net/mptcp/subflow.c > +++ b/net/mptcp/subflow.c > @@ -348,6 +348,10 @@ static void subflow_prep_synack(const struct sock *s= k, struct request_sock *req, > if (foc && foc->len > -1) > ireq->tstamp_ok =3D 0; > =20 > + /* MP_JOIN cannot use TFO, do not send a cookie in the SYN/ACK */ > + if (foc && mptcp_subflow_rsk(req)->mp_join) > + foc->len =3D -1; > + [Severity: Medium] Does this logic order introduce a regression that unnecessarily disables TCP timestamps on MP_JOIN subflows? When a client initiates an MP_JOIN connection with a TCP Fast Open cookie request, the original code in subflow_prep_synack() evaluates foc && foc->len > -1 and sets ireq->tstamp_ok =3D 0. Right after that, the newly added patch logic checks mp_join and sets foc->len =3D -1 to reject TFO. Because the timestamp check happens before the cookie is disabled, the SYN/= ACK is sent without both the TFO cookie and the TCP timestamp. Any remote client can trigger this by simply adding a TFO option to their MP_JOIN SYN packet. Could reversing the order of these checks preserve TCP timestamps by causing the timestamp condition to evaluate to false when foc->len is updated to -1? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260920061904.3575= 780-1-yilinzhang@moonshot.ai?part=3D1