linux-kernel - Re: [PATCH bpf-next v4 2/4] bpf: Expose bpf_get_socket

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Date:   Tue, 19 Jan 2021 16:59:38 +0100
From:   Florent Revest <revest@...omium.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        KP Singh <kpsingh@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 2/4] bpf: Expose bpf_get_socket_cookie to
 tracing programs

On Wed, Dec 9, 2020 at 5:35 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 12/9/20 2:26 PM, Florent Revest wrote:
> > This needs two new helpers, one that works in a sleepable context (using
> > sock_gen_cookie which disables/enables preemption) and one that does not
> > (for performance reasons). Both take a struct sock pointer and need to
> > check it for NULLness.
> >
> > This helper could also be useful to other BPF program types such as LSM.
>
> Looks like this commit description is now stale and needs to be updated
> since we only really add one helper?
>
> > Signed-off-by: Florent Revest <revest@...omium.org>
> > ---
> >   include/linux/bpf.h            |  1 +
> >   include/uapi/linux/bpf.h       |  7 +++++++
> >   kernel/trace/bpf_trace.c       |  2 ++
> >   net/core/filter.c              | 12 ++++++++++++
> >   tools/include/uapi/linux/bpf.h |  7 +++++++
> >   5 files changed, 29 insertions(+)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 07cb5d15e743..5a858e8c3f1a 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1860,6 +1860,7 @@ extern const struct bpf_func_proto bpf_per_cpu_ptr_proto;
> >   extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
> >   extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
> >   extern const struct bpf_func_proto bpf_sock_from_file_proto;
> > +extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
> >
> >   const struct bpf_func_proto *bpf_tracing_func_proto(
> >       enum bpf_func_id func_id, const struct bpf_prog *prog);
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index ba59309f4d18..9ac66cf25959 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -1667,6 +1667,13 @@ union bpf_attr {
> >    *  Return
> >    *          A 8-byte long unique number.
> >    *
> > + * u64 bpf_get_socket_cookie(void *sk)
> > + *   Description
> > + *           Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
> > + *           *sk*, but gets socket from a BTF **struct sock**.
>
> Maybe add a small comment that this one also works for sleepable [tracing] progs?
>
> > + *   Return
> > + *           A 8-byte long unique number.
>
> ... or 0 if *sk* is NULL.

Argh, I somehow missed this email during my holidays, I'm sending a
v5. Thank you Daniel!