netdev - Re: [PATCH bpf-next 9/9] tools/bpftool: add documentation and sample output for process info

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Date:   Wed, 17 Jun 2020 22:51:25 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>, Hao Luo <haoluo@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Song Liu <songliubraving@...com>
Subject: Re: [PATCH bpf-next 9/9] tools/bpftool: add documentation and sample
 output for process info

On Wed, Jun 17, 2020 at 5:25 PM Quentin Monnet <quentin@...valent.com> wrote:
>
> 2020-06-17 09:18 UTC-0700 ~ Andrii Nakryiko <andriin@...com>
> > Add statements about bpftool being able to discover process info, holding
> > reference to BPF map, prog, link, or BTF. Show example output as well.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> >  tools/bpf/bpftool/Documentation/bpftool-btf.rst  |  5 +++++
> >  tools/bpf/bpftool/Documentation/bpftool-link.rst | 13 ++++++++++++-
> >  tools/bpf/bpftool/Documentation/bpftool-map.rst  |  8 +++++++-
> >  tools/bpf/bpftool/Documentation/bpftool-prog.rst | 11 +++++++++++
> >  4 files changed, 35 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> > index ce3a724f50c1..85f7c82ebb28 100644
> > --- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> > +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> > @@ -36,6 +36,11 @@ DESCRIPTION
> >                 otherwise list all BTF objects currently loaded on the
> >                 system.
> >
> > +               Since Linux 5.8 bpftool is able to discover information about
> > +               processes that hold open file descriptors (FDs) against BPF
> > +               links. On such kernels bpftool will automatically emit this
>
> Copy-paste error: s/BPF links/BTF objects/
>

oops, will fix

> > +               information as well.
> > +
> >       **bpftool btf dump** *BTF_SRC*
> >                 Dump BTF entries from a given *BTF_SRC*.
> >
> > diff --git a/tools/bpf/bpftool/Documentation/bpftool-link.rst b/tools/bpf/bpftool/Documentation/bpftool-link.rst
> > index 0e43d7b06c11..1da7ef65b514 100644
> > --- a/tools/bpf/bpftool/Documentation/bpftool-link.rst
> > +++ b/tools/bpf/bpftool/Documentation/bpftool-link.rst
> > @@ -37,6 +37,11 @@ DESCRIPTION
> >                 zero or more named attributes, some of which depend on type
> >                 of link.
> >
> > +               Since Linux 5.8 bpftool is able to discover information about
> > +               processes that hold open file descriptors (FDs) against BPF
> > +               links. On such kernels bpftool will automatically emit this
> > +               information as well.
> > +
> >       **bpftool link pin** *LINK* *FILE*
> >                 Pin link *LINK* as *FILE*.
> >
> > @@ -82,6 +87,7 @@ EXAMPLES
> >
> >      10: cgroup  prog 25
> >              cgroup_id 614  attach_type egress
> > +            pids test_progs(2238417)
>
> (That's a big PID. Maybe something below the default max pid (32768)
> might be less confusing for users, but also maybe that's just me
> nitpicking too much.)

heh, real system, but yeah, I can make up a smaller PID :)

>
> >
> >  **# bpftool --json --pretty link show**
> >
> > @@ -91,7 +97,12 @@ EXAMPLES
> >              "type": "cgroup",
> >              "prog_id": 25,
> >              "cgroup_id": 614,
> > -            "attach_type": "egress"
> > +            "attach_type": "egress",
> > +            "pids": [{
> > +                    "pid": 2238417,
> > +                    "comm": "test_progs"
> > +                }
> > +            ]
> >          }
> >      ]
> >