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Date:   Fri, 6 Jan 2023 15:43:39 +0100
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Subject: Re: [PATCH bpf-next v3 00/16] bpfilter
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To:     Florian Westphal <fw@strlen.de>
CC:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>,
        Dmitrii Banshchikov <me@ubique.spb.ru>,
        <linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>,
        <linux-kselftest@vger.kernel.org>, <netdev@vger.kernel.org>,
        Kernel Team <kernel-team@meta.com>
References: <20221224000402.476079-1-qde@naccy.de>
 <20230103114540.GB13151@breakpoint.cc>
From:   Quentin Deslandes <qde@naccy.de>
In-Reply-To: <20230103114540.GB13151@breakpoint.cc>
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Le 03/01/2023 à 12:45, Florian Westphal a écrit :
> Quentin Deslandes <qde@naccy.de> wrote:
>> The patchset is based on the patches from David S. Miller [1],
>> Daniel Borkmann [2], and Dmitrii Banshchikov [3].
>>
>> Note: I've partially sent this patchset earlier due to a
>> mistake on my side, sorry for then noise.
>>
>> The main goal of the patchset is to prepare bpfilter for
>> iptables' configuration blob parsing and code generation.
>>
>> The patchset introduces data structures and code for matches,
>> targets, rules and tables. Beside that the code generation
>> is introduced.
>>
>> The first version of the code generation supports only "inline"
>> mode - all chains and their rules emit instructions in linear
>> approach.
>>
>> Things that are not implemented yet:
>>    1) The process of switching from the previous BPF programs to the
>>       new set isn't atomic.
> 
> You can't make this atomic from userspace perspective, the
> get/setsockopt API of iptables uses a read-modify-write model.

This refers to updating the programs from bpfilter's side. It won't
be atomic from iptables point of view, but currently bpfilter will
remove the program associated to a table, before installing the new
one. This means packets received in between those operations are
not filtered. I assume a better solution is possible.

> Tentatively I'd try to extend libnftnl and generate bpf code there,
> since its used by both iptables(-nft) and nftables we'd automatically
> get support for both.

That's one of the option, this could also remain in the kernel
tree or in a dedicated git repository. I don't know which one would
be the best, I'm open to suggestions.

> I was planning to look into "attach bpf progs to raw netfilter hooks"
> in Q1 2023, once the initial nf-bpf-codegen is merged.

Is there any plan to support non raw hooks? That's mainly out
of curiosity, I don't even know whether that would be a good thing
or not.