From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D943C1758F for ; Mon, 9 Sep 2024 16:50:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725900600; cv=none; b=GyNwyIuMslWHmn5H1tDD3RHmrAtrsHEBLMNaF4w8nE7nluO2DgbJrpAMPHTMCb6UNcUiD1dzSoh60VNt33wmU/8triODYgD95Es6/K4n+a95B00xgCIM1OW2xCWWR03+W2tvIr/oe26eRwUjB3hOmUDsYVaXoryfvLg2dH+yDWE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725900600; c=relaxed/simple; bh=K8NXXZ8EDphiablOrAVv62Y4Z7F2Y79eN6OpjwJkoKE=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=aya6RL4t2hjqkVked6xXrNVA6+FimB5rKhV7KZyECnh9t9oaL4etHZhYqsKdm2dwLioXseDxh2yFFX2iKyh5NZIiMxBMqv4UDjttvyplODrqP7j2fhT4aiD/bcJw79syWogqgsCfETPWddANqKezYE7blAMOWXfP/QNJpNT2ce4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ce0A9wc2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ce0A9wc2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DD14C4CEC5 for ; Mon, 9 Sep 2024 16:49:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1725900600; bh=K8NXXZ8EDphiablOrAVv62Y4Z7F2Y79eN6OpjwJkoKE=; h=Date:Subject:To:References:From:In-Reply-To:From; b=Ce0A9wc2fD9k9iWs84teof2mZe4YXUiFAWhrxrfAC0f56fBbS9lheHvoU+ZudbDEk KYLhHRDvbYasy7V0qqOgHnWFapatCNTmnLMdJOE4X2vTYW0/egFyVXc1vlKUijTMSi NOLTupI2kIKpQR5dzri8gq79wr+PYSlgqHB0XwFIdcOs6pflpBsC/okmefnx/kZW0v 8EjR29ZezkIJC6BjnOLOcVe6QkXMgjg8q9/QgNgAT/Nzd+Jdlgs2Vnqw0lOUbKT1um rajgrgzijaHqgbqnNitkgucBX2OHq7I125ciq6LxcOlj+zKjtcblU/LkhNBlZrrLxS Op8vhDttppxJg== Message-ID: <86a8a9ee-1dd8-41f6-984f-240bf83ce596@kernel.org> Date: Mon, 9 Sep 2024 18:49:58 +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 0/3] mptcp: fallback to TCP after 3 MPC drop + cache Content-Language: en-GB To: MPTCP Linux References: <20240902-mptcp-fallback-x-mpc-v1-0-86d9170ddff7@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hello, On 02/09/2024 11:09, Matthieu Baerts (NGI0) wrote: > The SYN + MPTCP_CAPABLE packets could be explicitly dropped by firewall > somewhere in the network, e.g. with: > > iptables -t filter -A FORWARD -p tcp --tcp-option 30 -j DROP > > The idea of this series is to fallback to TCP after 3 SYN+MPC drop > (patch 2). If the connection succeeds after the fallback, it very likely > means a blackhole has been detected. In this case (patch 3), MPTCP can > be disabled for a certain period of time, 1h by default. If after this > period, MPTCP is still blocked, the period is doubled. > > This should help applications which want to use MPTCP by default on the > client side if available. > > This series has been validated by a new packetdrill test: > > https://github.com/multipath-tcp/packetdrill/pull/156 > > Some questions: > > - Should we let the user changes the number of retransmissions (2) > before falling back to TCP? For TFO, the data are never retransmitted > in a SYN. Maybe that's different here? A sysctl knob could always be > added later on. > - Should we globally disable all MPTCP connections if any retransmission > after the fallback is a success instead of only the first one? I guess > we reduce risks of accidents by only looking at the following > retransmission after the fallback. > - Is one hour a good time for the fallback? > > For later: > > - The restriction could be done per oif (sk_dst_get(ssk)->dev), but we > would need to store it somehow, or per MPTCP entrypoint. Or let the PM > calling mptcp_active_enable() when a new endpoint is added. > - Other cases could trigger mptcp_active_disable(): e.g. some fallbacks > or corruptions in the middle of the connections. I suggest addressing these questions later. Due to some external circumstances, it is not possible to have more reviews for the moment. I think there is no need to block that longer, fixes can always be addressed later on. New patches for t/upstream: - a09026a9e8c4: mptcp: export mptcp_subflow_early_fallback() - 4216aa51fb10: mptcp: fallback to TCP after SYN+MPC drops - d0c7c7172eac: mptcp: disable active MPTCP in case of blackhole - 0fd52c49c60b: conflict in t/mptcp-annotate-data-races-around-subflow-fully_established - Results: 29da3bae8ab9..fc8995744495 (export) Tests are now in progress: - export: https://github.com/multipath-tcp/mptcp_net-next/commit/ca4d36d160ee56fa9bd50dc0006ad34d454d8f48/checks Cheers, Matt -- Sponsored by the NGI0 Core fund.