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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WNc1c5GM; 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="WNc1c5GM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC978C4CEC4; Fri, 6 Sep 2024 10:02:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1725616967; bh=iYA90GDpqgtTo5U9amp1FTYHBndZHESotRROhndrYU0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=WNc1c5GMH4SIZuzb1eANockt0P5pTnrLkblRvSprYWFrga6f2eDQWlb3eJYiLluJN euS7IGc+M3YKuzfBj9bWjvXR1ttNBbGDZsvAN/7EbgMbkMNPV203la4KYDc37w4NZE IygNJRkl82JmxuHqVbbWmWBsqpq7uHkMWCmMJVpKLqzGnxF60saiL9UxR8SDBD/3iz G4Kf/F7C5ARnKCRhr3IgYc3j9vRcWvKfBvdpfOptmmL0WupkSfDGzhfZjzTWgYb4hQ d0aonECpvj7sqITmF2JCDDq6OE+Z7nrGltQ3vEJ+2ulYp+CSVNPY+qnfGyO1h8xhjz 8x7tbRIXiTWhA== Message-ID: <18eb1fcd91e7283fda1932ff72e2d0cc53dc9e56.camel@kernel.org> Subject: Re: [PATCH mptcp-next 1/4] bpf: Add mptcp_subflow bpf_iter From: Geliang Tang To: Martin KaFai Lau , mptcp@lists.linux.dev Cc: Geliang Tang , Martin KaFai Lau , bpf Date: Fri, 06 Sep 2024 18:02:43 +0800 In-Reply-To: <288ad1c2-501a-4319-bc1e-e7a7e276ff63@linux.dev> References: <288ad1c2-501a-4319-bc1e-e7a7e276ff63@linux.dev> Autocrypt: addr=geliang@kernel.org; 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charset="UTF-8" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Martin, On Thu, 2024-09-05 at 11:24 -0700, Martin KaFai Lau wrote: > On 9/5/24 6:52 AM, Geliang Tang 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. > > > > This patch adds a new bpf_iter type named "mptcp_subflow" to do > > this. > > > > Suggested-by: Martin KaFai Lau > > Signed-off-by: Geliang Tang > > --- > >   kernel/bpf/helpers.c |  3 +++ > >   net/mptcp/bpf.c      | 57 > > ++++++++++++++++++++++++++++++++++++++++++++ > >   2 files changed, 60 insertions(+) > > > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > > index b5f0adae8293..2340ba967444 100644 > > --- a/kernel/bpf/helpers.c > > +++ b/kernel/bpf/helpers.c > > @@ -3023,6 +3023,9 @@ BTF_ID_FLAGS(func, bpf_preempt_enable) > >   BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW) > >   BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | > > KF_RET_NULL) > >   BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY) > > +BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_new) > > +BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_next) > > +BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_destroy) > >   BTF_KFUNCS_END(common_btf_ids) > >   > >   static const struct btf_kfunc_id_set common_kfunc_set = { > > diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c > > index 9672a70c24b0..cda09bbfd617 100644 > > --- a/net/mptcp/bpf.c > > +++ b/net/mptcp/bpf.c > > @@ -204,6 +204,63 @@ static const struct btf_kfunc_id_set > > bpf_mptcp_fmodret_set = { > >    .set   = &bpf_mptcp_fmodret_ids, > >   }; > >   > > +struct bpf_iter__mptcp_subflow { > > + __bpf_md_ptr(struct bpf_iter_meta *, meta); > > + __bpf_md_ptr(struct mptcp_sock *, msk); > > + __bpf_md_ptr(struct list_head *, pos); > > +}; > > + > > +DEFINE_BPF_ITER_FUNC(mptcp_subflow, struct bpf_iter_meta *meta, > > +      struct mptcp_sock *msk, struct list_head *pos) > > + > > +struct bpf_iter_mptcp_subflow { > > + __u64 __opaque[3]; > > +} __attribute__((aligned(8))); > > + > > +struct bpf_iter_mptcp_subflow_kern { > > + struct mptcp_sock *msk; > > + struct list_head *pos; > > +} __attribute__((aligned(8))); > > + > > +__bpf_kfunc_start_defs(); > > + > > +__bpf_kfunc 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; > > + > > + kit->msk = msk; > > + kit->pos = &msk->conn_list; > > + spin_lock_bh(&msk->pm.lock); > > I don't think spin_lock here without unlock can be used. e.g. What if > bpf_iter_mptcp_subflow_new() is called twice back-to-back. > > I haven't looked at the mptcp details, some questions: > The list is protected by msk->pm.lock? > What happen to the sk_lock of the msk? > Can this be rcu-ify? or it needs some cares when walking the > established TCP > subflow? Thank you for your review. msk->pm.lock shouldn't be used here. The conn_list is not protected by msk->pm.lock. I will remove it in v2. > > > [ Please cc the bpf list. Helping to review patches is a good way to > contribute > back to the mailing list. ] This patch is for "mptcp-next", it depends on the "new MPTCP subflow subtest" which is under review on the bpf list. We will send it to the bpf list very soon. Thanks, -Geliang > > > + > > + return 0; > > +} > > + > > +__bpf_kfunc struct mptcp_subflow_context * > > +bpf_iter_mptcp_subflow_next(struct bpf_iter_mptcp_subflow *it) > > +{ > > + struct bpf_iter_mptcp_subflow_kern *kit = (void *)it; > > + struct mptcp_subflow_context *subflow; > > + struct mptcp_sock *msk = kit->msk; > > + > > + subflow = list_entry((kit->pos)->next, struct > > mptcp_subflow_context, node); > > + if (list_entry_is_head(subflow, &msk->conn_list, node)) > > + return NULL; > > + > > + kit->pos = &subflow->node; > > + return subflow; > > +} > > + > > +__bpf_kfunc void bpf_iter_mptcp_subflow_destroy(struct > > bpf_iter_mptcp_subflow *it) > > +{ > > + struct bpf_iter_mptcp_subflow_kern *kit = (void *)it; > > + struct mptcp_sock *msk = kit->msk; > > + > > + spin_unlock_bh(&msk->pm.lock); > > +} > > + > > +__bpf_kfunc_end_defs(); > > + > >   __diag_push(); > >   __diag_ignore_all("-Wmissing-prototypes", > >      "kfuncs which will be used in BPF programs"); >