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 A702547CA80 for ; Tue, 18 Aug 2026 16:19:50 +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=1787069991; cv=none; b=avbX/3Hxi20MrTwaMjWnQ89l4WqgKr8P8Znjh7vkd8obHAMtn3rcLNCRN9ITVfo6IbuT9bKvR2dhQ2EJA9t7XB1MZbmP48T1KdJGhwVE/c6nobF3za+/16jFjj6dYePZ+eKVuttiRNmO3ui0BXD4wq9MU65UIaqE58t2x70gYzg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787069991; c=relaxed/simple; bh=WY7m0uVjGu44sh593QNM/IcV1AZfA5FgZPsDu+hrWnM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u/kKUs4h9qJXLQYiLohscrBQPcmfU9C8LQi+uQtjpXgo8aTBbc/g6fHHZJii3KDGppij+l82OSn86TGPg2fif/rNZYMsV4OMvYRa740O/69CgAEwjlSBcXUUOZz6nNiGBFwO9PY2TcbvGq2PVPH6k/lAmWeULDTvK01pVeHhd/c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V7JlKrQ4; 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="V7JlKrQ4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C3971F000E9; Tue, 18 Aug 2026 16:19:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787069990; bh=mJijs80dwZwNAgQzNaJWFi8oGTxb37UB8cS+kRBHPTI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=V7JlKrQ4KpY4RShtqJYnt6vJSkpvhAMF5zcbyrLIEO8C2yiidf7WcMnYIZcMJhAKa 85IZi7XCNslXhEZKR5k/j0msF/rG1cMtlONu3G6jxHJoMf5a6f9gBDHKwNXbRlVGPP B77LZJko3T/etHjCeUzadGXhD0L1ySx4JfBTOaMA41UQv6qSbWzgNFQzckAZ1jw9+I 6ZmA5yYaNzKxxVh2iqrP6XUGfMMxTETky25m6NXSa+Zgu3Xbjq7eEuPio+fIOpN6MD R4TJh/nQJSAIxdarJ6ZEU4jh+0mf7TqZhewy3aXwRvXkt486Nt3gi1MxxtCAEuplfH MD4Nn6DB4a7Sw== Message-ID: <68791a9e-9310-4368-854e-d379ce0b416c@kernel.org> Date: Tue, 18 Aug 2026 18:19:46 +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 mptcp-next RFC v4 2/2] mptcp: send MP_FAIL and infinite mapping on the same ACK Content-Language: fr To: Chenguang Zhao , mptcp@lists.linux.dev Cc: Chenguang Zhao References: <20260818091417.2200986-1-chenguang.zhao@linux.dev> <20260818091417.2200986-3-chenguang.zhao@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Chenguang, On 18/08/2026 11:14, Chenguang Zhao wrote: > From: Chenguang Zhao > > On a single subflow, accepting MP_FAIL must leave MPTCP mode at once > (RFC8684 §3.7). Emit the infinite mapping on the MP_FAIL reply ACK, > then call mptcp_try_fallback() immediately after. I think Sashiko is right about the issue of lacking option space to have both the MP_FAIL and the infinite mapping sent together. Please also note this from RFC 8684 §3.7.11 [1]: > This infinite mapping will be a DSS option (Section 3.3) on the first > new packet, containing a Data Sequence Mapping that acts retroactively The "on the first new packet" seems to suggest the infinite mapping shouldn't be attached to the MP_FAIL. [1] https://datatracker.ietf.org/doc/html/rfc8684#section-3.7-11 Maybe a fallback for the single subflow without csum is enough? Or maybe nothing needs to be done? Or maybe this fallback is just an optimisation, and can be done in net-next (and both commits can be combined)? WDYT? > Fixes: 1e39e5a32ad7 ("mptcp: infinite mapping sending") > Signed-off-by: Chenguang Zhao > --- > net/mptcp/options.c | 33 ++++++++++++++++++++++++++++++++- > net/mptcp/pm.c | 5 +++++ > net/mptcp/protocol.c | 8 +------- > 3 files changed, 38 insertions(+), 8 deletions(-) > > diff --git a/net/mptcp/options.c b/net/mptcp/options.c > index 97da22668dbe..ecf77e77d2de 100644 > --- a/net/mptcp/options.c > +++ b/net/mptcp/options.c > @@ -638,7 +638,29 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb, > opts->csum_reqd = READ_ONCE(msk->csum_enabled); > mpext = skb ? mptcp_get_ext(skb) : NULL; > > - if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) { > + if (unlikely(subflow->send_infinite_map)) { > + unsigned int map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64; > + > + if (opts->csum_reqd) > + map_size += TCPOLEN_MPTCP_DSS_CHECKSUM; > + > + if (mpext) { > + opts->ext_copy = *mpext; > + opts->ext_copy.infinite_map = 1; > + opts->ext_copy.data_len = 0; > + } else { > + opts->ext_copy.use_map = 1; > + opts->ext_copy.dsn64 = 1;> + opts->ext_copy.infinite_map = 1; > + opts->ext_copy.data_len = 0; > + opts->ext_copy.data_seq = READ_ONCE(msk->snd_nxt); > + opts->ext_copy.subflow_seq = subflow->rel_write_seq; > + } You probably also need to reset "csum". Note that common fields (infinite_map and data_len) can also be set once here. (...) Cheers, Matt -- Sponsored by the NGI0 Core fund.