Re: libxsk move from libbpf to libxdp

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Magnus Karlsson <magnus.karlsson@gmail.com> writes:

> On Tue, Oct 26, 2021 at 6:18 AM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
>>
>> On Mon, Oct 25, 2021 at 9:03 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>> >
>> > Magnus Karlsson <magnus.karlsson@gmail.com> writes:
>> >
>> > > On Fri, Oct 22, 2021 at 7:49 PM Andrii Nakryiko
>> > > <andrii.nakryiko@gmail.com> wrote:
>> > >>
>> > >> Hey guys,
>> > >>
>> > >> It's been a while since we chatted about libxsk move. I believe last
>> > >> time we were already almost ready to recommend libxdp for this, but
>> > >> I'd like to double-check. Can one of you please own [0], validate that
>> > >> whatever APIs are provided by libxdp are equivalent to what libbpf
>> > >> provides, and start marking xdk.h APIs as deprecated? Thanks!
>> > >
>> > > Resending since Gmail had jumped out of plain text mode again.
>> > >
>> > > No problem, I will own this. I will verify the APIs are the same then
>> > > submit a patch marking the ones in libbpf's xsk.h as deprecated.
>> > >
>> > > One question is what to do with the samples and the selftests for xsk.
>> > > They currently rely on libbpf's xsk support. Two options that I see:
>> > >
>> > > 1: Require libxdp on the system. Do not try to compile the xsk samples
>> > > and selftests if libxdp is not available so the rest of the bpf
>> > > samples and selftests are not impacted.
>> > > 2: Provide a standalone mock-up file of xsk.c and xsk.h that samples
>> > > and selftests could use.
>> > >
>> > > I prefer #1 as it is better for the long-term. #2 means I would have
>> > > to maintain that mock-up file as libxdp features are added. Sounds
>> > > like double the amount of work to me. Thoughts?
>> >
>> > I agree #1 is preferable of those two. Another option is to move the
>> > samples to the xdp-tools repo instead? Doesn't work for selftests, of
>> > course; if it's acceptable to conditionally-compile the XSK tests
>> > depending on system library availability that would be fine by me...
>>
>> Seems like the only thing that uses xsk.h is xdpxceiver.c which is
>> tested through test_xsk.sh. It's not part of test_progs and so isn't
>> run regularly by BPF CI or maintainers. It makes sense to me to move
>> such test closer to the library it's supposed to be testing (i.e.,
>> libxdp)?
>
> xdpxceiver.c tests kernel functionality, not libxdp functionality,
> though it does use libxdp (and libbpf) to make the implementation
> simpler. So it should remain here and use strategy #1. libxdp tests
> are on another level and should definitely go into the libxdp repo.
> The xsk samples in samples/bpf/, we could just stop developing/retire
> (or even remove) in the Linux repo and move them to the xdp-tools
> repo. They just show how to use the xsk.h api:s and it makes more
> sense to have them together with libxdp.

SGTM :)

-Toke