netdev - Re: [PATCH bpf-next] bpf: allow BPF read access to qdisc pkt

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Date:   Fri, 30 Nov 2018 18:42:45 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     liu.song.a23@...il.com
Cc:     Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Petar Penkov <peterpenkov96@...il.com>,
        Vlad Dumitrescu <vladum@...gle.com>,
        Petar Penkov <ppenkov@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH bpf-next] bpf: allow BPF read access to qdisc pkt_len

On Fri, Nov 30, 2018 at 5:48 PM Song Liu <liu.song.a23@...il.com> wrote:
>
> On Fri, Nov 30, 2018 at 12:09 PM Willem de Bruijn
> <willemdebruijn.kernel@...il.com> wrote:
> >
> > From: Petar Penkov <ppenkov@...gle.com>
> >
> > The pkt_len field in qdisc_skb_cb stores the skb length as it will
> > appear on the wire after segmentation. For byte accounting, this value
> > is more accurate than skb->len. It is computed on entry to the TC
> > layer, so only valid there.
> >
> > Allow read access to this field from BPF tc classifier and action
> > programs. The implementation is analogous to tc_classid, aside from
> > restricting to read access.
> >
> > Signed-off-by: Petar Penkov <ppenkov@...gle.com>
> > Signed-off-by: Vlad Dumitrescu <vladum@...gle.com>
> > Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> > ---
> >  include/uapi/linux/bpf.h                    |  1 +
> >  net/core/filter.c                           | 16 +++++++++++
> >  tools/include/uapi/linux/bpf.h              |  1 +
> >  tools/testing/selftests/bpf/test_verifier.c | 32 +++++++++++++++++++++
> >  4 files changed, 50 insertions(+)
>
> Please split this into 3 patches:
> 1 for include/uapi/linux/bpf.h and filter.c
> 1 for tools/include/uapi/linux/bpf.h
> 1 for tools/testing/selftests/bpf/test_verifier.c
>
> Other than this
> Acked-by: Song Liu <songliubraving@...com>

Thanks for the fast review.

I'm happy to resend in three parts, of course, but am curious: what is
the rationale for splitting this up?

This patch follows the process for commit  f11216b24219 ("bpf: add
skb->tstamp r/w access from tc clsact and cg skb progs"), which went
in as a single patch just last week.