netdev - Re: [PATCH bpf-next 07/10] bpf: Add helpers to query conntrack info

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Date:   Wed, 20 Oct 2021 11:48:15 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Florian Westphal <fw@...len.de>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     Maxim Mikityanskiy <maximmi@...dia.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Joe Stringer <joe@...ium.io>,
        Lorenz Bauer <lmb@...udflare.com>,
        Tariq Toukan <tariqt@...dia.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH bpf-next 07/10] bpf: Add helpers to query conntrack info

Florian Westphal <fw@...len.de> writes:

> Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
>> On Tue, Oct 19, 2021 at 08:16:52PM IST, Maxim Mikityanskiy wrote:
>> > The new helpers (bpf_ct_lookup_tcp and bpf_ct_lookup_udp) allow to query
>> > connection tracking information of TCP and UDP connections based on
>> > source and destination IP address and port. The helper returns a pointer
>> > to struct nf_conn (if the conntrack entry was found), which needs to be
>> > released with bpf_ct_release.
>> >
>> > Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
>> > Reviewed-by: Tariq Toukan <tariqt@...dia.com>
>> 
>> The last discussion on this [0] suggested that stable BPF helpers for conntrack
>> were not desired, hence the recent series [1] to extend kfunc support to modules
>> and base the conntrack work on top of it, which I'm working on now (supporting
>> both CT lookup and insert).
>
> This will sabotage netfilter pipeline and the way things work more and
> more 8-(

Why?

> If you want to use netfilter with ebpf, please have a look at the RFC
> I posted and lets work on adding a netfilter specific program type
> that can run ebpf programs directly from any of the existing netfilter
> hook points.

Accelerating netfilter using BPF is a worthy goal in itself, but I also
think having the ability to lookup into conntrack from XDP is useful for
cases where someone wants to bypass the stack entirely (for accelerating
packet forwarding, say). I don't think these goals are in conflict
either, what makes you say they are?

-Toke