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 A0A411AF0DC; Thu, 30 Jan 2025 12:06:10 +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=1738238771; cv=none; b=HE7kcZlnobmQ24xPN1pyNbCgXU4peoLW8kduo8c/Sys2H4vlMyo3m+qak93hxphLtQzsaxxl3HquADp1/Z1MSJwTxrpqNRyLQnJjJ1VAWidNkzh7diR/HNf98EjUukyVXujPWGfzzZjp41qbf8GXmpT0qc9l9FxRHH8hQR8hqpI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738238771; c=relaxed/simple; bh=xopmZEADxLu17v8s1oec48v9swghvqcukEWRE5i/ArQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Rg89ZkYP4ZL6PDEwKg+5i1XdCvDfpA7fRzP22ETPFI93fGKu/ebaaCHbwu8WqIs59oSj9N9n3StZqmifvtg1OdMT1PPu1b3XYK2JDWssBWUdyoi0vULxoqI4Gyeuo23Cjs8Sdxxs5MIITL1sj7cABUvtPe4brdxw68d1CTvWy6o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mAR3DGWc; 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="mAR3DGWc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D33C4C4CED2; Thu, 30 Jan 2025 12:05:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738238770; bh=xopmZEADxLu17v8s1oec48v9swghvqcukEWRE5i/ArQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mAR3DGWcYda1w4z0OEHonKPUaUDc0dWMf/3YYEXtK61VMN/NDdh1hVPVJF54ImIb1 fBhqehjqpuNIDlQOBHjtXaWdqlW0quBcdIUcAEdRGZCN+wqL/b+bJOJQWbIyRJhirr GyWrVb0JimepHfBcJTgTUuKieX/YqXI/8fP8hY8jsthxtlOqQZr8hp/xDISGE0owm0 gYGE+ahAYxDoTtKItvF6X3BQEmd4knWu/UJl/DUXleKBH/xvYVzkkLdZlTIYkyik6Z aMwzkD6yE42iXUkpvOEHiEA2T8cB/kSyu05k5dHLcL/Mwp2WUiez14Oo3o2OIxLFtT b3mdKDD/0Nz0Q== Message-ID: <3b5af48e-4155-4b98-b67b-b75d9fb6285e@kernel.org> Date: Thu, 30 Jan 2025 13:05:54 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH bpf-next/net v2 4/7] bpf: Add mptcp_subflow bpf_iter Content-Language: en-GB To: Martin KaFai Lau , Geliang Tang Cc: mptcp@lists.linux.dev, Mat Martineau , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Martin KaFai Lau References: <20241219-bpf-next-net-mptcp-bpf_iter-subflows-v2-0-ae244d3cdbbc@kernel.org> <20241219-bpf-next-net-mptcp-bpf_iter-subflows-v2-4-ae244d3cdbbc@kernel.org> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Martin, Thank you for your review! Sorry for the delay here, Geliang started to work on a new version, but it might take a bit of time as he is currently off for a few days. On 24/01/2025 01:47, Martin KaFai Lau wrote: > On 12/19/24 7:46 AM, Matthieu Baerts (NGI0) wrote: >> From: Geliang Tang >> >> It's necessary to traverse all subflows on the conn_list of an MPTCP >> socket and then call kfunc to modify the fields of each subflow. In >> kernel space, mptcp_for_each_subflow() helper is used for this: >> >>     mptcp_for_each_subflow(msk, subflow) >>         kfunc(subflow); >> >> But in the MPTCP BPF program, this has not yet been implemented. As >> Martin suggested recently, this conn_list walking + modify-by-kfunc >> usage fits the bpf_iter use case. >> >> So this patch adds a new bpf_iter type named "mptcp_subflow" to do >> this and implements its helpers bpf_iter_mptcp_subflow_new()/_next()/ >> _destroy(). And register these bpf_iter mptcp_subflow into mptcp >> common kfunc set. Then bpf_for_each() for mptcp_subflow can be used >> in BPF program like this: >> >>     bpf_for_each(mptcp_subflow, subflow, msk) >>         kfunc(subflow); (...) >> diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c >> index >> c5bfd84c16c43230d9d8e1fd8ff781a767e647b5..e39f0e4fb683c1aa31ee075281daee218dac5878 100644 >> --- a/net/mptcp/bpf.c >> +++ b/net/mptcp/bpf.c (...) >> @@ -47,10 +56,54 @@ bpf_mptcp_subflow_ctx(const struct sock *sk) >>       return NULL; >>   } >>   +__bpf_kfunc static int >> +bpf_iter_mptcp_subflow_new(struct bpf_iter_mptcp_subflow *it, >> +               struct mptcp_sock *msk) >> +{ >> +    struct bpf_iter_mptcp_subflow_kern *kit = (void *)it; >> +    struct sock *sk = (struct sock *)msk; >> + >> +    BUILD_BUG_ON(sizeof(struct bpf_iter_mptcp_subflow_kern) > >> +             sizeof(struct bpf_iter_mptcp_subflow)); >> +    BUILD_BUG_ON(__alignof__(struct bpf_iter_mptcp_subflow_kern) != >> +             __alignof__(struct bpf_iter_mptcp_subflow)); >> + >> +    kit->msk = msk; >> +    if (!msk) > > NULL check is not needed. verifier should have rejected it for > KF_TRUSTED_ARGS. > >> +        return -EINVAL; >> + >> +    if (!sock_owned_by_user_nocheck(sk) && >> +        !spin_is_locked(&sk->sk_lock.slock)) > > I could have missed something. If it is to catch bug, should it be > sock_owned_by_me() that has the lockdep splat? For the cg get/setsockopt > hook here, the lock should have already been held earlier in the kernel. Good point. Because in this series, the kfunc is currently restricted to CG [gs]etsockopt hooks, we should use msk_owned_by_me(msk) here. > This set is only showing the cg sockopt bpf prog but missing the major > struct_ops piece. It is hard to comment. I assumed the lock situation is > the same for the struct_ops where the lock will be held before calling > the struct_ops prog? I understand it is hard to comment on that point. In the 'struct_ops' we are designing, the lock will indeed be held before calling the stuct_ops program. So we will just need to make sure this assumption is correct for all callbacks of our struct_ops. Also, if I understood correctly, it is possible to restrict a kfunc to some specific struct_ops, e.g. not to call this kfunc for the TCP CA struct_ops. So these checks should indeed not be needed, but I will double-check that with Geliang. Cheers, Matt -- Sponsored by the NGI0 Core fund.