netdev - Re: [PATCH bpf-next v4 07/10] net/netfilter: Add unstable CT lookup helpers for XDP and TC-BPF

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Date:   Fri, 17 Dec 2021 14:10:03 +0530
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org,
        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>,
        Maxim Mikityanskiy <maximmi@...dia.com>,
        Florian Westphal <fw@...len.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next v4 07/10] net/netfilter: Add unstable CT lookup
 helpers for XDP and TC-BPF

On Fri, Dec 17, 2021 at 01:48:19PM IST, Pablo Neira Ayuso wrote:
> On Fri, Dec 17, 2021 at 07:20:28AM +0530, Kumar Kartikeya Dwivedi wrote:
> > This change adds conntrack lookup helpers using the unstable kfunc call
> > interface for the XDP and TC-BPF hooks. The primary usecase is
> > implementing a synproxy in XDP, see Maxim's patchset at [0].
> >
> > Export get_net_ns_by_id as nf_conntrack needs to call it.
> >
> > Note that we search for acquire, release, and null returning kfuncs in
> > the intersection of those sets and main set.
> >
> > This implies that the kfunc_btf_id_list acq_set, rel_set, null_set may
> > contain BTF ID not in main set, this is explicitly allowed and
> > recommended (to save on definining more and more sets), since
> > check_kfunc_call verifier operation would filter out the invalid BTF ID
> > fairly early, so later checks for acquire, release, and ret_type_null
> > kfunc will only consider allowed BTF IDs for that program that are
> > allowed in main set. This is why the nf_conntrack_acq_ids set has BTF
> > IDs for both xdp and tc hook kfuncs.
> >
> >   [0]: https://lore.kernel.org/bpf/20211019144655.3483197-1-maximmi@nvidia.com
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > ---
> >  include/linux/btf.h               |   2 +
> >  kernel/bpf/btf.c                  |   1 +
> >  net/core/filter.c                 |  24 +++
> >  net/core/net_namespace.c          |   1 +
> >  net/netfilter/nf_conntrack_core.c | 278 ++++++++++++++++++++++++++++++
>
> Toke proposed to move it to net/netfilter/nf_conntrack_bpf.c

Ugh, sorry. I think I completely missed that mail, but I see it now.

I'll wait for this review cycle to conclude, and then put the code in its own
file in the next version.

Thanks.

--
Kartikeya