Re: [PATCH bpf-next 0/3] samples: bpf: Refactor XDP programs with libbpf

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@gmail.com> wrote:
>
> To avoid confusion caused by the increasing fragmentation of the BPF
> Loader program, this commit would like to convert the previous bpf_load
> loader with the libbpf loader.
>
> Thanks to libbpf's bpf_link interface, managing the tracepoint BPF
> program is much easier. bpf_program__attach_tracepoint manages the
> enable of tracepoint event and attach of BPF programs to it with a
> single interface bpf_link, so there is no need to manage event_fd and
> prog_fd separately.
>
> And due to addition of generic bpf_program__attach() to libbpf, it is
> now possible to attach BPF programs with __attach() instead of
> explicitly calling __attach_<type>().
>
> This patchset refactors xdp_monitor with using this libbpf API, and the
> bpf_load is removed and migrated to libbpf. Also, attach_tracepoint()
> is replaced with the generic __attach() method in xdp_redirect_cpu.
> Moreover, maps in kern program have been converted to BTF-defined map.
>
> Daniel T. Lee (3):
>   samples: bpf: Refactor xdp_monitor with libbpf
>   samples: bpf: Replace attach_tracepoint() to attach() in
>     xdp_redirect_cpu
>   samples: bpf: refactor XDP kern program maps with BTF-defined map
>
>  samples/bpf/Makefile                |   4 +-
>  samples/bpf/xdp_monitor_kern.c      |  60 ++++++------
>  samples/bpf/xdp_monitor_user.c      | 144 +++++++++++++++++++++-------
>  samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++-------------
>  samples/bpf/xdp_sample_pkts_kern.c  |  14 ++-
>  samples/bpf/xdp_sample_pkts_user.c  |   1 -
>  6 files changed, 211 insertions(+), 150 deletions(-)
>
> --
> 2.25.1
>

Thanks for this clean up, Daniel! It's great! I left a few nits here
and there in the appropriate patches.

There still seem to be a bunch of users of bpf_load.c, which would be
nice to get rid of completely. But before you go do that, consider
integrating BPF skeleton into samples/bpf Makefile. That way instead
of all those look ups of maps/programs by name, you'd be writing a
straightforward skel->maps.my_map and similar short and non-failing
code. This should make the overall time spent on conversion much
smaller (and more pleasant, IMO).

You've dealt with a lot of samples/bpf reworking, so it should be too
hard for you to figure out the best way to do this, but check
selftests/bpf's Makefile, if you need some ideas. Or just ask for
help. Thanks!