netdev - Re: [PATCH bpf-next v3 00/16] bpfilter

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Date:   Tue, 3 Jan 2023 12:45:40 +0100
From:   Florian Westphal <fw@...len.de>
To:     Quentin Deslandes <qde@...cy.de>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        Dmitrii Banshchikov <me@...que.spb.ru>,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        Kernel Team <kernel-team@...a.com>
Subject: Re: [PATCH bpf-next v3 00/16] bpfilter

Quentin Deslandes <qde@...cy.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.

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.

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