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 7AD7E346E75 for ; Sun, 16 Aug 2026 16:12:29 +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=1786896750; cv=none; b=uT84afvliUDmL9iAdHJm7DuSx5N907+lU3QuWdIcjqoWthEaE+jaxiyBYzV/OSbmSHmRGVqnZSlUYWhwZdgF5vw77TN2tb/TtTUFJ3gDEFyKpFiYYgp6fo1O1XVW7JdRv8TgRz0iyGngkyb78Hi5OQJg9/Su8t3stmUD5NY79vY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786896750; c=relaxed/simple; bh=Zz2GFz+Ku/4c64lVKr+crqrnl++Fl9gMWIRKbr3XP2k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=I8V13JGvZZUGHHmT5K4OB9iRy8E8I76pB66VnX6Xbf7SZPzrfSUJkzvuwOryw81vdDRqDeunmNGvEnWYDxgFKzdnxIUJB+ELe2ekMg3cPV1RUNnSevCPsxSUygRPxMNLcASeShi2JHtTYbO6pHhYxTAvcMnbYPPEVTLduCGgkKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n5F0BVtW; 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="n5F0BVtW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 480811F000E9; Sun, 16 Aug 2026 16:12:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786896749; bh=hT49ysomEbTWJK78ajs/M3cDOcYz8UzpEOwwb/kOFj8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=n5F0BVtWteA+Kz/ZokscDlauiw4+iBTXdVkLpVF1K7xGqqh9VmA34pCHQtnenclT4 LjNdjPLA7fIaLPQVvrwOjP8uPYnB3vEkkHLx3JTLvEWPD/PKAB1Hr8F+hnT3fKt819 O4GeX0qendQ4Zv9dTJyHoMEBBWJ0toZ6WcNG5N78p66CfRwl4w/QFzx4wz+4USNLIe 8+0ul8D5fj7cEPZ8YkSir/s4CPxcYCwn+DQh+hWKLTInZ5eme83+L7bXMJaT85uwv2 GijbOc/FTYuoExVTF+bDLvpej+w1pVau1gfXJCLNJAjuXggF70Xy423kILKClu08bc sgbXtBJP2x4Ww== Message-ID: <687bd2da-28b5-4753-b942-d18cb53d9239@kernel.org> Date: Sun, 16 Aug 2026 18:12:26 +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 2/3] mptcp: reject MP_JOIN earlier Content-Language: fr To: MPTCP Linux Cc: Paolo Abeni , Chenguang Zhao , gang.yan@linux.dev References: <20260814-mptcp-reset-mpj-early-v1-0-3ca3260f9474@kernel.org> <20260814-mptcp-reset-mpj-early-v1-2-3ca3260f9474@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hello, On 14/08/2026 20:31, Matthieu Baerts (NGI0) wrote: > When a SYN + MP_JOIN is received, it is good to check directly if the > MP_JOIN is allowed, then checking that later at the establishment of the > new subflow. > > This avoids situations where the 3WHS is done, then the joined subflow > is rejected. > > This changes the behaviour, and the new behaviour is tracked with the > MPJoinDisallow MIB counter. > > TODO: adapt the selftests to be able to run on older kernels: if the new > counter is not available, increment syn_ack and syn_rej instead. (...) > @@ -217,17 +228,19 @@ static int subflow_check_req(struct request_sock *req, > SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT); > > } else if (opt_mp_join && listener->request_mptcp) { > + u8 reason; > + > subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq; > subflow_req->mp_join = 1; > subflow_req->backup = mp_opt.backup; > subflow_req->remote_id = mp_opt.join_id; > subflow_req->token = mp_opt.token; > subflow_req->remote_nonce = mp_opt.nonce; > - subflow_req->msk = subflow_token_join_request(req); > + subflow_req->msk = subflow_token_join_request(req, &reason); > > /* Can't fall back to TCP in this case. */ > if (!subflow_req->msk) { > - subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP); > + subflow_add_reset_reason(skb, reason); > return -EPERM; > } Note: the call to mptcp_can_accept_new_subflow() here below, when handling req->syncookies, is no longer needed as it is now done earlier for all cases, in subflow_token_join_request(). Cheers, Matt -- Sponsored by the NGI0 Core fund.