netdev - Re: [PATCH bpf-next 0/5] libbpf: error reporting changes for v1.0

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Date:   Mon, 24 May 2021 12:18:54 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 0/5] libbpf: error reporting changes for v1.0

On Sun, May 23, 2021 at 11:36 PM John Fastabend
<john.fastabend@...il.com> wrote:
>
> Andrii Nakryiko wrote:
> > Implement error reporting changes discussed in "Libbpf: the road to v1.0"
> > ([0]) document.
> >
> > Libbpf gets a new API, libbpf_set_strict_mode() which accepts a set of flags
> > that turn on a set of libbpf 1.0 changes, that might be potentially breaking.
> > It's possible to opt-in into all current and future 1.0 features by specifying
> > LIBBPF_STRICT_ALL flag.
> >
> > When some of the 1.0 "features" are requested, libbpf APIs might behave
> > differently. In this patch set a first set of changes are implemented, all
> > related to the way libbpf returns errors. See individual patches for details.
> >
> > Patch #1 adds a no-op libbpf_set_strict_mode() functionality to enable
> > updating selftests.
> >
> > Patch #2 gets rid of all the bad code patterns that will break in libbpf 1.0
> > (exact -1 comparison for low-level APIs, direct IS_ERR() macro usage to check
> > pointer-returning APIs for error, etc). These changes make selftest work in
> > both legacy and 1.0 libbpf modes. Selftests also opt-in into 100% libbpf 1.0
> > mode to automatically gain all the subsequent changes, which will come in
> > follow up patches.
> >
> > Patch #3 streamlines error reporting for low-level APIs wrapping bpf() syscall.
> >
> > Patch #4 streamlines errors for all the rest APIs.
> >
> > Patch #5 ensures that BPF skeletons propagate errors properly as well, as
> > currently on error some APIs will return NULL with no way of checking exact
> > error code.
> >
> >   [0] https://docs.google.com/document/d/1UyjTZuPFWiPFyKk1tV5an11_iaRuec6U-ZESZ54nNTY
> >
> > Andrii Nakryiko (5):
> >   libbpf: add libbpf_set_strict_mode() API to turn on libbpf 1.0
> >     behaviors
> >   selftests/bpf: turn on libbpf 1.0 mode and fix all IS_ERR checks
> >   libbpf: streamline error reporting for low-level APIs
> >   libbpf: streamline error reporting for high-level APIs
> >   bpftool: set errno on skeleton failures and propagate errors
> >
>
> LGTM for the series,
>
> Acked-by: John Fastabend <john.fastabend@...il.com>

Thanks, John!

Toke, Stanislav, you cared about these aspects of libbpf 1.0 (by
commenting on the doc itself), do you mind also taking a brief look
and letting me know if this works for your use cases? Thanks!