netdev - Re: [PATCH bpf-next v5 0/3] libbpf: use func name when pinning programs with LIBBPF_STRICT_SEC

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Date:   Fri, 22 Oct 2021 16:57:15 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH bpf-next v5 0/3] libbpf: use func name when pinning
 programs with LIBBPF_STRICT_SEC_NAME

On Thu, Oct 21, 2021 at 2:48 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Commit 15669e1dcd75 ("selftests/bpf: Normalize all the rest SEC() uses")
> broke flow dissector tests. With the strict section names, bpftool isn't
> able to pin all programs of the objects (all section names are the
> same now). To bring it back to life let's do the following:
>
> - teach libbpf to pin by func name with LIBBPF_STRICT_SEC_NAME
> - enable strict mode in bpftool (breaking cli change)
> - fix custom flow_dissector loader to use strict mode
> - fix flow_dissector tests to use new pin names (func vs sec)
>
> v5:
> - get rid of error when retrying with '/' (Quentin Monnet)
>
> v4:
> - fix comment spelling (Quentin Monnet)
> - retry progtype without / (Quentin Monnet)
>
> v3:
> - clarify program pinning in LIBBPF_STRICT_SEC_NAME,
>   for real this time (Andrii Nakryiko)
> - fix possible segfault in __bpf_program__pin_name (Andrii Nakryiko)
>
> v2:
> - add github issue (Andrii Nakryiko)
> - remove sec_name from bpf_program.pin_name comment (Andrii Nakryiko)
> - add cover letter (Andrii Nakryiko)
>
> Stanislav Fomichev (3):
>   libbpf: use func name when pinning programs with
>     LIBBPF_STRICT_SEC_NAME
>   bpftool: conditionally append / to the progtype
>   selftests/bpf: fix flow dissector tests

I've applied patches #1 and #3, as they have to happen regardless of
how bpftool incompatibility is going to be handled. Please see
comments from John about bpftool. I think we should try to preserve
bpftool's backwards compatibility, or at the very least give users
some way to fall back to non-strict mode during the transition period.
I trust you, John and Quentin will figure out the best way forward
there.

Also, please move this flow_dissector_load selftest into test_progs,
so that we exercise it regularly.

>
>  tools/bpf/bpftool/main.c                      |  4 +++
>  tools/bpf/bpftool/prog.c                      | 35 ++++++++++---------
>  tools/lib/bpf/libbpf.c                        | 13 +++++--
>  tools/lib/bpf/libbpf_legacy.h                 |  3 ++
>  .../selftests/bpf/flow_dissector_load.c       | 18 ++++++----
>  .../selftests/bpf/flow_dissector_load.h       | 10 ++----
>  .../selftests/bpf/test_flow_dissector.sh      | 10 +++---
>  7 files changed, 55 insertions(+), 38 deletions(-)
>
> --
> 2.33.0.1079.g6e70778dc9-goog
>