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 7ED512C181 for ; Tue, 26 May 2026 08:39:32 +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=1779784773; cv=none; b=XXLL7eJZqfFogzCOSR0WyO19IG4HrgJUoi6tkLH39+MsZGizp2vDyIKcxctvg5u0wD2N0MljBLKmvgASOgosHxJmVc4Aw5wVIfC0/t8mqJoYEBWkGQWVFgvms1f6eaEQxbRkRwVubceduvZAGwd6IpDgrQlxQ/DgfnUh4qoFNIQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779784773; c=relaxed/simple; bh=gjJCeE5ZoHl9mWuglj5zDpq6uvzDqpIrZWpNyprf+Jc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fLD9nuBepH8mMB3Y/zbU4WN/DZRoOXCapEQHXa6hLWrhVkSLNExBgPGL3CD3Q/OvKfamt71W9cCtwxkToUotwgePlo53DzZh+82PPtrFzkSy78L4K2ECWnTT83VNskNnCneh6Ym9wxQT7wjXQqEVx2yuWMlgyISO9JmXbcNXFXk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L8qzL3JP; 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="L8qzL3JP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAB181F000E9; Tue, 26 May 2026 08:39:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779784772; bh=l0fribLA3ITytQFqCr/JcMelKMA66SkRlZ2VuNAhvK4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=L8qzL3JP0fayXd9FeoCyuD1CXWrrAC9Vzc9xykGN52UqciFhWdxd9h87KzhgaEtZm a1xwlFTWglFE0LfdVCdklObfhq0HmxO5mJWAZarFLyETEUWWB5F/VMzMjB3BqlQaaT 4SbiF0glG3ucHA6h1xeEmU+zV3+G98AFUsknKmupkOsnaE/NNBpBvHtZT/bFfCm8dK Kq4bWM5NWxD1T0qseHJcNsZWRAXoT0uFETjLz+WydsBZw/hhYMcO0gFt3fnFshDnaB nyy8ZXzv9/WY99+oMqrQ61hXnRYT5QWCg7vc/iK13ZOGWyOok32HrIo9uMYONe627z 0KPkh07KNl5Jw== Message-ID: <07bf06c0-20dd-4e31-960a-b79f6fffcecc@kernel.org> Date: Tue, 26 May 2026 18:39:26 +1000 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: pm: don't WARN on re-announced addr in kernel PM Content-Language: fr To: Kalpan Jani , mptcp@lists.linux.dev Cc: martineau@kernel.org, pabeni@redhat.com, janak@mpiric.us, shardul.b@mpiricsoftware.com, kalpanjani009@gmail.com, shardulsb08@gmail.com References: <20260525121911.2410171-1-kalpan.jani@mpiricsoftware.com> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Kalpan, On 25/05/2026 22:19, Kalpan Jani wrote: > syzkaller hit the WARN_ON_ONCE() in mptcp_pm_alloc_anno_list() with > the in-kernel path manager, reached via > mptcp_pm_create_subflow_or_signal_addr(). > > The WARN assumes the kernel PM can never reselect an address that is > still in msk->pm.anno_list. That is not true: when an endpoint is > removed and re-added while a previously sent ADD_ADDR is still > awaiting its echo, the endpoint id becomes available again in > id_avail_bitmap, but the matching anno_list entry (with its > retransmit timer) is still alive. The in-progress guard in > mptcp_pm_create_subflow_or_signal_addr() only checks > BIT(MPTCP_ADD_ADDR_SIGNAL), which is already cleared once the option > has been transmitted, so the address gets reselected and reaches > mptcp_pm_alloc_anno_list() a second time. >From what I understand, it means that if a "signal" MPTCP endpoint is removed the echo got received, the in-kernel PM will continue retransmitting the ADD_ADDR. That doesn't seem correct. I didn't check in the code, but I thought that the retransmit timer was at least stopped, but maybe the entry was not removed from the list? Does it also mean that if an ADD_ADDR echo is never received, the entry is never removed, even after having reached the max retransmissions? > This is a benign transient state, so drop the WARN. For the kernel > PM, just bail out: the ADD_ADDR is already in flight, and the PM will > be rescheduled once it completes (or once the stale entry's timer > expires). If I understand correctly, the transient state is not benign, and the WARN should not be dropped. Also, it would be nice to add a new test to validate that. Here, it might be easier with a packetdrill test [1]: start with one sending an ADD_ADDR [2], but don't send the echo, and instead, remove and re-add the endpoint. [1] https://github.com/multipath-tcp/packetdrill [2] https://github.com/multipath-tcp/packetdrill/blob/mptcp-net-next/gtests/net/mptcp/add_addr/add_addr4_server.pkt Cheers, Matt -- Sponsored by the NGI0 Core fund.