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 ABB841D5AC6 for ; Fri, 24 Jan 2025 09:11:10 +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=1737709870; cv=none; b=tcCNmBe2pgnfA9+HSsAoFriOlAGOy0JdxjMcAY3CQVLszthN7A5kt2NgE5GhWUExOGtQlNvM6aHguPitPEFymXTm+aueTnYF12sC9MxGCdXIe6Nhj+oryN/PWBt+CUHsltV211o5c9ngXBtIzRiZ9et5hvf/MwgNxzEONh96Qf8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737709870; c=relaxed/simple; bh=ikimO1VKpqZ3Gn4pIIUy0cWPTTJTVHD6QtN5C0aNjUE=; h=Message-ID:Date:MIME-Version:Subject:To:References:Cc:From: In-Reply-To:Content-Type; b=p5MNXVRsTEgczF9aJsDLl2oOhFw6Bw/BJhb6KPgXSDUhMdRH3awbouApHUF81e/NooAfsMpDQ3gyziKckgsxcyezBR89ncf0Z073ebYMJRPHuEB8twurg5tngZhenPvSYBzlranmAGvNABurKHpJupEsYumlKPyU75Sfkl2B6ig= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RAz8v128; 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="RAz8v128" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 916A4C4CED2; Fri, 24 Jan 2025 09:11:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737709870; bh=ikimO1VKpqZ3Gn4pIIUy0cWPTTJTVHD6QtN5C0aNjUE=; h=Date:Subject:To:References:Cc:From:In-Reply-To:From; b=RAz8v1285JKnC5G3XF+BDWlDv83Si4Ja1iJaBeKXWYVFXVEUr4JR7ibjlBZHjcn1/ vgPrQhxxKQrjxONEKrWxZTCvyEGvT+IE+02yaoHyHQfAy/ndRkBhLNkhsWTAI3P0pz ZBXFwc+geqFsCPA3gZXwB335qhi+Lhv8sfEYm6oIGLp8syAuuXOWXHJpSb6rU4ybCd qZcVQiKiAgxrtxv+CvAqYZ5J9P08ysFMSCinz8huiTJIxlHdnUdg+oFAWaS+UCCkJ/ tJkl/bDa4A/qZE2PfftzvBRnYrsngLyGTgrVW6clzNSeqocAhg6ZXn7IYGtLiTKFE+ xtXnS/FDFUu2g== Message-ID: <378683da-ce3e-4c6d-b933-265d404a716c@kernel.org> Date: Fri, 24 Jan 2025 10:10:58 +0100 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 bpf-next/net v2 4/7] bpf: Add mptcp_subflow bpf_iter Content-Language: en-GB To: Geliang Tang 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> Cc: MPTCP Linux From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Geliang, (only with the MPTCP list) 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); >> >> Suggested-by: Martin KaFai Lau >> Signed-off-by: Geliang Tang >> Reviewed-by: Mat Martineau >> Signed-off-by: Matthieu Baerts (NGI0) >> --- >> Notes: >>   - v2: >>     - Add BUILD_BUG_ON() checks, similar to the ones done with other >>       bpf_iter_(...) helpers. >>     - Replace msk_owned_by_me() by sock_owned_by_user_nocheck() and >>       !spin_is_locked() (Martin). >> >> A few versions of this single patch have been previously posted to the >> BPF mailing list by Geliang, before continuing to the MPTCP mailing list >> only, with other patches of this series. The version of the whole series >> has been reset to 1, but here is the ChangeLog for the previous ones: >>   - v2: remove msk->pm.lock in _new() and _destroy() (Martin) >>         drop DEFINE_BPF_ITER_FUNC, change opaque[3] to opaque[2] (Andrii) >>   - v3: drop bpf_iter__mptcp_subflow >>   - v4: if msk is NULL, initialize kit->msk to NULL in _new() and check >>         it in _next() (Andrii) >>   - v5: use list_is_last() instead of list_entry_is_head() add >>         KF_ITER_NEW/NEXT/DESTROY flags add msk_owned_by_me in _new() >>   - v6: add KF_TRUSTED_ARGS flag (Andrii, Martin) >> --- >>   net/mptcp/bpf.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++ >> ++++++ >>   1 file changed, 53 insertions(+) >> >> 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 >> @@ -35,6 +35,15 @@ static const struct btf_kfunc_id_set >> bpf_mptcp_fmodret_set = { >>       .set   = &bpf_mptcp_fmodret_ids, >>   }; >>   +struct bpf_iter_mptcp_subflow { >> +    __u64 __opaque[2]; >> +} __aligned(8); >> + >> +struct bpf_iter_mptcp_subflow_kern { >> +    struct mptcp_sock *msk; >> +    struct list_head *pos; >> +} __aligned(8); >> + >>   __bpf_kfunc_start_defs(); >>     __bpf_kfunc static struct mptcp_subflow_context * >> @@ -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. :) So from what I understand: either we need these checks because this helper could technically be called when these conditions are not met. Or we don't need them, and we can have sock_owned_by_me() (without the return that was in the v1) for lockdep. > 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? Can we restrict the use of this helper only for some specific callbacks? Or for only some specific struct_ops? Last time I looked, I thought that you could only restrict it like that: "this helper can be used by (any) struct_ops". But then does it mean this helper could be called from a TCP BPF CC ops or another unrelated one for example? How can we avoid that? Cheers, Matt -- Sponsored by the NGI0 Core fund.