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 290F53BCD15 for ; Mon, 17 Aug 2026 11:07:26 +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=1786964847; cv=none; b=fUIPgC90ZSsvYYrP/V0fFJvUqwXnCInJv+yABqCm/hfA2qk1lwIloAZL9MYF6U8w3AUY2MLqFSOm73tQ8+vZYPa5C/xLzsFESWetyHB5HInsZp3fhm6EiigSWksGcy2xPn4DLf7lNKFYpFtrbWQl+nTEehdt0H/WUWkVoURW92I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786964847; c=relaxed/simple; bh=zrVyvn/mCM1Qm17BIcTtC3cEaZe46WXOncuAwXpj+FM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uki5Beebsvd+TCxJx/1ZjGme0HzDUdOYVgooGxYlHOO/wMQh4chbUUJcMCoEjSHtG7oHIQQ8L+YP0ezxHOuwid8RZz3W4GcwG+v0pDnFHhfaHuW/xZZgBqkeO/krnxH6AMWOYCEikOMhPK9ALYHePiWw4LPg0GVLar8xlEX73gY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mM0yFF00; 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="mM0yFF00" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDDA91F000E9; Mon, 17 Aug 2026 11:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786964846; bh=pEB9/e/jLaToIpAulcetkdxTBJa0VX6kc/CDit1TTwQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mM0yFF00AF2gWDBLynmr2c7Q0+LiJBHObQqvbu6c3KJSutkjdq0dg2lyvABjNtkc1 HYeUre95UG1myNwFcp6Jw+1Dfqxna8bkN8+7dkKaa7vw6rY9dzA2+3bnqyTTvzVbvK iquFssEJiS5Q4xBuAiLc52OLK7eRcLY0owlN6/Pn22LW1XK7tz1MSlEDDijUwR3fVs k2Vh/M8gWig9aIQ8Xu2Y2sWx1j3YfrGiTzIPs+xlkzYgcQtXcr2Kawz64p/tGOeWKi WjSHk+HTJ3vISUgj9tc9ycxoEbgChHM1SFhZ9t9axJQfYc/DxHFqyZPNEeTlP8gR9M WO2tZ86l63RPQ== Message-ID: <2e2b6eff-0d2c-40b9-b66c-f650bb5d1104@kernel.org> Date: Mon, 17 Aug 2026 13:07:22 +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 3/3] mptcp: pm: kernel: skip operating on closing connections Content-Language: fr To: Paolo Abeni , MPTCP Linux Cc: Chenguang Zhao , gang.yan@linux.dev References: <20260814-mptcp-reset-mpj-early-v1-0-3ca3260f9474@kernel.org> <20260814-mptcp-reset-mpj-early-v1-3-3ca3260f9474@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Paolo, On 17/08/2026 09:39, Paolo Abeni wrote: > On 8/14/26 8:31 PM, Matthieu Baerts (NGI0) wrote: >> When iterating over each MPTCP connection after having manipulated MPTCP >> endpoints, there is no need to operate on closing (or not ready) >> connections. >> >> We can then safely skip those. >> >> Note that mptcp_nl_add_subflow_or_signal_addr() was already checking the >> fully_established state, but it is better to check the connection state, >> which is what mptcp_is_fully_established() is doing. >> >> Signed-off-by: Matthieu Baerts (NGI0) >> --- >> net/mptcp/pm_kernel.c | 16 +++++++++++----- >> 1 file changed, 11 insertions(+), 5 deletions(-) >> >> diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c >> index d3014bf57bf3..c185e53fe42b 100644 >> --- a/net/mptcp/pm_kernel.c >> +++ b/net/mptcp/pm_kernel.c >> @@ -969,7 +969,7 @@ static int mptcp_nl_add_subflow_or_signal_addr(struct net *net, >> struct sock *sk = (struct sock *)msk; >> struct mptcp_addr_info mpc_addr; >> >> - if (!READ_ONCE(msk->fully_established) || >> + if (!mptcp_is_fully_established(sk) || >> mptcp_pm_is_userspace(msk)) >> goto next; > > I'm a little double-minded here. > > The add/removal operations are issued by the user space to update > subflows, as a consequence of endpoint addition/removal. > > Possibly removing the subflow even for not fully established connections > could be the right thing to do, I'm not 110% sure either way. Possibly > worth to call this out with a comment? Indeed, I'm also not sure. Initially, I only converted this READ_ONCE(msk->fully_established), also because later in mptcp_pm_create_subflow_or_signal_addr(), mptcp_is_fully_established() is used. Probably best to stick to this one. On the other hand, I just noticed that there is no check for "fallback done" here: so the operations leading to a notification (ADD_ADDR, RM_ADDR) will send a dup-ACK (pure ACK without MPTCP options), and adding an MPTCP endpoint will lead to... the creation of a new subflow, even after a fallback, e.g. -------------------------- 8< -------------------------- C > S: Flags [S], seq 0, win 65535, options [mss 1460,sackOK,nop,nop,nop,wscale 6,mptcp 4 capable v1], length 0 S > C: Flags [S.], seq 2252073282, ack 1, win 65535, options [mss 1460,nop,nop,sackOK,nop,wscale 8,mptcp 12 capable v1 {0xb80fe7957527e1f7}], length 0 C > S: Flags [.], ack 1, win 2048, options [mptcp 20 capable v1 {0x200000000000000,0xb80fe7957527e1f7}], length 0 C > S: Flags [P.], seq 1:501, ack 1, win 2048, options [mptcp 22 capable v1 {0xb80fe7957527e1f7,0x200000000000000},nop,nop], length 500: HTTP S > C: Flags [.], ack 501, win 1049, options [mptcp 12 dss ack 13263177308786789273], length 0 // Here, the client receives the ACK without MPTCP options due to middleboxes → fallback S > C: Flags [P.], seq 1:101, ack 501, win 1049, options [mptcp 26 dss ack 13263177308786789273 seq 14591534807969507511 subseq 1 len 100,nop,nop], length 100: HTTP C > S: Flags [.], ack 101, win 2048, length 0 // fallback on the server side C > S: Flags [P.], seq 501:601, ack 101, win 2048, length 100: HTTP S > C: Flags [.], ack 601, win 1049, length 0 // Data OK // Adding a new subflow endpoint now: S2 > C: Flags [S], seq 618398320, win 65535, options [mss 1460,sackOK,TS val 3041525989 ecr 0,nop,wscale 8,mptcp 12 join id 1 token 0xd86e8112 nonce 0x6cca79f5], length 0 -------------------------- 8< -------------------------- Oops. Still, not a big deal, but probably better and safer to avoid that, no? Maybe patch 1 (reset fully_estab after a fallback) and this patch here but only looking at READ_ONCE(msk->fully_established) is enough? Patch 2 would be for -next. > Also the asymmetry with the user-space PM is a bit strange. I can't > recall why it was needed in the first place?!? Are you talking about all the mptcp_pm_is_userspace() checks? If yes, they are required because the pm_type sysctl could be changed, and we could end-up with a mix of msk handled by different PMs in the same netns. It would be better to do the opposite I guess: if (!mptcp_pm_is_kernel(msk)) goto next; Cheers, Matt -- Sponsored by the NGI0 Core fund.