netdev - Re: [PATCH bpf-next 1/7] bpf/flow_dissector: pass input flags to BPF flow dissector program

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Date:   Wed, 24 Jul 2019 15:45:22 -0700
From:   Song Liu <liu.song.a23@...il.com>
To:     Stanislav Fomichev <sdf@...ichev.me>
Cc:     Stanislav Fomichev <sdf@...gle.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Petar Penkov <ppenkov@...gle.com>
Subject: Re: [PATCH bpf-next 1/7] bpf/flow_dissector: pass input flags to BPF
 flow dissector program

On Wed, Jul 24, 2019 at 3:32 PM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> On 07/24, Song Liu wrote:
> > On Wed, Jul 24, 2019 at 10:11 AM Stanislav Fomichev <sdf@...gle.com> wrote:
> > >
> > > C flow dissector supports input flags that tell it to customize parsing
> > > by either stopping early or trying to parse as deep as possible. Pass
> > > those flags to the BPF flow dissector so it can make the same
> > > decisions. In the next commits I'll add support for those flags to
> > > our reference bpf_flow.c
> > >
> > > Cc: Willem de Bruijn <willemb@...gle.com>
> > > Cc: Petar Penkov <ppenkov@...gle.com>
> > > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > > ---
> > >  include/linux/skbuff.h       | 2 +-
> > >  include/net/flow_dissector.h | 4 ----
> > >  include/uapi/linux/bpf.h     | 5 +++++
> > >  net/bpf/test_run.c           | 2 +-
> > >  net/core/flow_dissector.c    | 5 +++--
> > >  5 files changed, 10 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > > index 718742b1c505..9b7a8038beec 100644
> > > --- a/include/linux/skbuff.h
> > > +++ b/include/linux/skbuff.h
> > > @@ -1271,7 +1271,7 @@ static inline int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
> > >
> > >  struct bpf_flow_dissector;
> > >  bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
> > > -                     __be16 proto, int nhoff, int hlen);
> > > +                     __be16 proto, int nhoff, int hlen, unsigned int flags);
> > >
> > >  bool __skb_flow_dissect(const struct net *net,
> > >                         const struct sk_buff *skb,
> > > diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
> > > index 90bd210be060..3e2642587b76 100644
> > > --- a/include/net/flow_dissector.h
> > > +++ b/include/net/flow_dissector.h
> > > @@ -253,10 +253,6 @@ enum flow_dissector_key_id {
> > >         FLOW_DISSECTOR_KEY_MAX,
> > >  };
> > >
> > > -#define FLOW_DISSECTOR_F_PARSE_1ST_FRAG                BIT(0)
> > > -#define FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL    BIT(1)
> > > -#define FLOW_DISSECTOR_F_STOP_AT_ENCAP         BIT(2)
> > > -
> > >  struct flow_dissector_key {
> > >         enum flow_dissector_key_id key_id;
> > >         size_t offset; /* offset of struct flow_dissector_key_*
> > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > index fa1c753dcdbc..b4ad19bd6aa8 100644
> > > --- a/include/uapi/linux/bpf.h
> > > +++ b/include/uapi/linux/bpf.h
> > > @@ -3507,6 +3507,10 @@ enum bpf_task_fd_type {
> > >         BPF_FD_TYPE_URETPROBE,          /* filename + offset */
> > >  };
> > >
> > > +#define FLOW_DISSECTOR_F_PARSE_1ST_FRAG                (1U << 0)
> > > +#define FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL    (1U << 1)
> > > +#define FLOW_DISSECTOR_F_STOP_AT_ENCAP         (1U << 2)
> >
> > Do we have to move these?
> These have to be a part of UAPI one way or another. The easiest thing
> we can do is to call the existing flags a UAPI and move them into
> exported headers. Alternatively, we can introduce new set of UAPI flags
> and do some kind of conversion between exported and internal ones.
>
> Since it's pretty easy to add/deprecate them (see cover letter), I've
> decided to just move them instead of adding another set and doing
> conversion. I'm open to suggestions if you think otherwise.

I see. This looks good to me. Thanks for the explanation.

Acked-by: Song Liu <songliubraving@...com>