netdev - Re: [PATCH v3 bpf-next 2/9] libbpf: introduce concept of bpf

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Message-ID: <CAEf4BzbB6G5jTvS+K0+0zPXWLFmAePHU2RtALogWrh7h7OV03A@mail.gmail.com>
Date:   Fri, 28 Jun 2019 09:42:18 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...ichev.me>
Cc:     Andrii Nakryiko <andriin@...com>, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v3 bpf-next 2/9] libbpf: introduce concept of bpf_link

On Fri, Jun 28, 2019 at 9:02 AM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> On 06/27, Andrii Nakryiko wrote:
> > bpf_link is and abstraction of an association of a BPF program and one
> > of many possible BPF attachment points (hooks). This allows to have
> > uniform interface for detaching BPF programs regardless of the nature of
> > link and how it was created. Details of creation and setting up of
> > a specific bpf_link is handled by corresponding attachment methods
> > (bpf_program__attach_xxx) added in subsequent commits. Once successfully
> > created, bpf_link has to be eventually destroyed with
> > bpf_link__destroy(), at which point BPF program is disassociated from
> > a hook and all the relevant resources are freed.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> >  tools/lib/bpf/libbpf.c   | 17 +++++++++++++++++
> >  tools/lib/bpf/libbpf.h   |  4 ++++
> >  tools/lib/bpf/libbpf.map |  3 ++-
> >  3 files changed, 23 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 6e6ebef11ba3..455795e6f8af 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3941,6 +3941,23 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> >       return 0;
> >  }
> >
> > +struct bpf_link {
> Maybe call it bpf_attachment? You call the bpf_program__attach_to_blah
> and you get an attachment?

I wanted to keep it as short as possible, bpf_attachment is way too
long (it's also why as an alternative I've proposed bpf_assoc, not
bpf_association, but bpf_attach isn't great shortening).

>
> > +     int (*destroy)(struct bpf_link *link);
> > +};
> > +
> > +int bpf_link__destroy(struct bpf_link *link)
> > +{
> > +     int err;
> > +
> > +     if (!link)
> > +             return 0;
> > +
> > +     err = link->destroy(link);
> > +     free(link);
> > +
> > +     return err;
> > +}
> > +
> >  enum bpf_perf_event_ret
> >  bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
> >                          void **copy_mem, size_t *copy_size,
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index d639f47e3110..5082a5ebb0c2 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -165,6 +165,10 @@ LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
> >  LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
> >  LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
> >
> > +struct bpf_link;
> > +
> > +LIBBPF_API int bpf_link__destroy(struct bpf_link *link);
> > +
> >  struct bpf_insn;
> >
> >  /*
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index 2c6d835620d2..3cde850fc8da 100644
> > --- a/tools/lib/bpf/libbpf.map
> > +++ b/tools/lib/bpf/libbpf.map
> > @@ -167,10 +167,11 @@ LIBBPF_0.0.3 {
> >
> >  LIBBPF_0.0.4 {
> >       global:
> > +             bpf_link__destroy;
> > +             bpf_object__load_xattr;
> >               btf_dump__dump_type;
> >               btf_dump__free;
> >               btf_dump__new;
> >               btf__parse_elf;
> > -             bpf_object__load_xattr;
> >               libbpf_num_possible_cpus;
> >  } LIBBPF_0.0.3;
> > --
> > 2.17.1
> >