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 5C99232E734; Wed, 5 Nov 2025 14:39:51 +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=1762353592; cv=none; b=smasg+hkCc6S8NXukrgnhdaYE36SfQ0eFtQMg8iSwjb+wIJ/+JMji3BlPtj3m1psZ5pVPu4yuqrUp7YkSSg3t+GnGxnxpULyFl+k0yKXMbz5YewKtUN85QlCpK38zDVPsxUVwK6cNsxbqxENAezW1252CLLKv+HcEvbpjEE7rGs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762353592; c=relaxed/simple; bh=+mv6NfioSiuInevvVRb70iVEPo0SPK5TgrVbTAcEEVw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ErOxJNiiuRfh7ZTmloTgrPRDqIVU+No3aTkX22JvH++figWEPfgoGDy2awEFGWhRTYRjGSJqCnwoqL61f91Ih9tQWLCYU4dlP0eWdsNSWWMTPmqBBKnsLTD6W1SgMFj1RDQT4BK4iTnsELmogYMcI2xBuQBVIOP7gKRwnG29660= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BF+mmeds; 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="BF+mmeds" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 582BAC4CEFB; Wed, 5 Nov 2025 14:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762353591; bh=+mv6NfioSiuInevvVRb70iVEPo0SPK5TgrVbTAcEEVw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=BF+mmedsn7rXygxZ+LKjynR0FAIelUrh6mynAB6b+oZDeMuHxxH+gG4Nw+DPMz3hw 5xDtMMkYrGdDC7TjeM+0A18SjFEhgTfOriSOm11yiJTBvO4C7WgOboXIiWU/dyHiPn 2tTjDrp9kGo8hGz9XOi1ucA0Js4JKwdzbvz9vyVKT+Hu2pf6H8vQMTLM74WvoilJXK jAIoTZdUwY8gemEk0fa5vAGJorMi+Q/slZJmvgsiRnRn0SfWBb9jZK5PpYN7d4dmcr 5eJRpqdMx0irin9hO4qaCB5v8EdsOdxs5txeLQ4nl7x651VQk5fjlDd3kc0kTQeas1 pGhKuodBV77xw== Message-ID: <291e0c4c-fdd2-44dc-abe5-a4b7fb9f34be@kernel.org> Date: Wed, 5 Nov 2025 15:39:40 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net v4 1/3] mptcp: disallow MPTCP subflows from sockmap Content-Language: en-GB, fr-BE To: Jiayuan Chen , mptcp@lists.linux.dev Cc: stable@vger.kernel.org, Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Florian Westphal , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20251105113625.148900-1-jiayuan.chen@linux.dev> <20251105113625.148900-2-jiayuan.chen@linux.dev> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20251105113625.148900-2-jiayuan.chen@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jiayuan, On 05/11/2025 12:36, Jiayuan Chen wrote: > The sockmap feature allows bpf syscall from userspace using , or based (is there a word missing before the ','?) > on bpf sockops, replacing the sk_prot of sockets during protocol stack > processing with sockmap's custom read/write interfaces. > ''' > tcp_rcv_state_process() > subflow_syn_recv_sock() > tcp_init_transfer(BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB) > bpf_skops_established <== sockops > bpf_sock_map_update(sk) <== call bpf helper > tcp_bpf_update_proto() <== update sk_prot > ''' > Consider two scenarios: > > 1. When the server has MPTCP enabled and the client also requests MPTCP, > the sk passed to the BPF program is a subflow sk. Since subflows only > handle partial data, replacing their sk_prot is meaningless and will > cause traffic disruption. > > 2. When the server has MPTCP enabled but the client sends a TCP SYN > without MPTCP, subflow_syn_recv_sock() performs a fallback on the > subflow, replacing the subflow sk's sk_prot with the native sk_prot. > ''' > subflow_ulp_fallback() > subflow_drop_ctx() > mptcp_subflow_ops_undo_override() > ''' > Subsequently, accept::mptcp_stream_accept::mptcp_fallback_tcp_ops() > converts the subflow to plain TCP. > > For the first case, we should prevent it from being combined with sockmap > by setting sk_prot->psock_update_sk_prot to NULL, which will be blocked by > sockmap's own flow. > > For the second case, since subflow_syn_recv_sock() has already restored > sk_prot to native tcp_prot/tcpv6_prot, no further action is needed. > > Fixes: 0b4f33def7bb ("mptcp: fix tcp fallback crash") It should not change anything for the backport, but for this patch, the Fixes tag can be older I think, e.g. Fixes: cec37a6e41aa ("mptcp: Handle MP_CAPABLE options for outgoing connections") If you need to send a v5, please use this one. Reviewed-by: Matthieu Baerts (NGI0) Cheers, Matt -- Sponsored by the NGI0 Core fund.