netdev - Re: [PATCH bpf-next 0/3] move AF

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Date:   Thu, 9 Jun 2022 22:52:46 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Magnus Karlsson <magnus.karlsson@...il.com>,
        Hangbin Liu <liuhangbin@...il.com>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>, Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, bpf <bpf@...r.kernel.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: Re: [PATCH bpf-next 0/3] move AF_XDP APIs to libxdp

On 6/9/22 10:29 PM, Andrii Nakryiko wrote:
> On Wed, Jun 8, 2022 at 3:18 AM Magnus Karlsson
> <magnus.karlsson@...il.com> wrote:
>> On Wed, Jun 8, 2022 at 9:55 AM Hangbin Liu <liuhangbin@...il.com> wrote:
>>> On Tue, Jun 07, 2022 at 11:31:57AM +0200, Toke Høiland-Jørgensen wrote:
>>>> Hangbin Liu <liuhangbin@...il.com> writes:
>>>>
>>>>> libbpf APIs for AF_XDP are deprecated starting from v0.7.
>>>>> Let's move to libxdp.
>>>>>
>>>>> The first patch removed the usage of bpf_prog_load_xattr(). As we
>>>>> will remove the GCC diagnostic declaration in later patches.
>>>>
>>>> Kartikeya started working on moving some of the XDP-related samples into
>>>> the xdp-tools repo[0]; maybe it's better to just include these AF_XDP
>>>> programs into that instead of adding a build-dep on libxdp to the kernel
>>>> samples?
>>>
>>> OK, makes sense to me. Should we remove these samples after the xdp-tools PR
>>> merged? What about xdpxceiver.c in selftests/bpf? Should that also be moved to
>>> xdp-tools?
>>
>> Andrii has submitted a patch [1] for moving xsk.[ch] from libbpf to
>> the xsk selftests so it can be used by xdpxceiver. This is a good idea
>> since xdpxceiver tests the low level kernel interfaces and should not
>> be in libxdp. I can also use those files as a start for implementing
>> control interface tests which are in the planning stages. But the
>> xdpsock sample shows how to use libxdp to write an AF_XDP program and
>> belongs more naturally with libxdp. So good that Kartikeya is moving
>> it over. Thanks!
>>
>> Another option would be to keep the xdpsock sample and require libxdp
>> as in your patch set, but you would have to make sure that everything
>> else in samples/bpf compiles neatly even if you do not have libxdp.
>> Test for the presence of libxdp in the Makefile and degrade gracefully
>> if you do not. But we would then have to freeze the xdpsock app as all
>> new development of samples should be in libxdp. Or we just turn
>> xdpsock into a README file and direct people to the samples in libxdp?
>> What do you think?
> 
> I think adding libxdp dependency for samples/bpf is a bad idea. Moving
> samples to near libxdp makes more sense to me.

+1 on moving them out from samples/bpf/ to somewhere near libxdp repo given
it'll be usage example of libxdp.

More generally, the useful XDP-related things could migrate from samples/bpf/
over to either https://github.com/xdp-project/bpf-examples/ or
https://github.com/xdp-project/xdp-tools and then we could potentially toss
the samples/bpf/ dir from the kernel tree.

These days there are tons of howtos and example progs out in the wild and
better tooling/framework available for users to get started. Taking XDP
aside for a bit, a lot of stuff in samples/bpf/ is just outdated.

Brendan recently also started drafting guidelines (wip) for newbies getting
into development with pointers where to look [0]. So really, there's less and
less good reason for samples/bpf/ these days.

   [0] http://vger.kernel.org/bpfconf2022_material/lsfmmbpf2022-bpf-wip-guidelines.pdf

>> [1] https://lore.kernel.org/bpf/20220603190155.3924899-2-andrii@kernel.org/
>>
>>> Thanks
>>> Hangbin