netdev - Re: [PATCH bpf-next 08/13] bpf: add bpf_skb_adjust_room flag BPF_F_ADJ_ROOM_FIXED

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Date:   Thu, 21 Mar 2019 10:00:48 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Peter Oskolkov <posk@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH bpf-next 08/13] bpf: add bpf_skb_adjust_room flag BPF_F_ADJ_ROOM_FIXED_GSO

On Thu, Mar 21, 2019 at 9:43 AM Alan Maguire <alan.maguire@...cle.com> wrote:
>
>
>
> On Wed, 20 Mar 2019, Willem de Bruijn wrote:
>
> > From: Willem de Bruijn <willemb@...gle.com>
> >
> > bpf_skb_adjust_room adjusts gso_size of gso packets to account for the
> > pushed or popped header room.
> >
> > This is not allowed with UDP, where gso_size delineates datagrams. Add
> > an option to avoid these updates and allow this call for datagrams.
> >
> > It can also be used with TCP, when MSS is known to allow headroom,
> > e.g., through MSS clamping or route MTU.
> >
> > Link: https://patchwork.ozlabs.org/patch/1052497/
> > Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> > ---
> >  include/uapi/linux/bpf.h |  4 ++++
> >  net/core/filter.c        | 36 +++++++++++++++++++++++++-----------
> >  2 files changed, 29 insertions(+), 11 deletions(-)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 4f5c918e6fcf4..0eda8f564a381 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -2593,6 +2593,10 @@ enum bpf_func_id {
> >  /* Current network namespace */
> >  #define BPF_F_CURRENT_NETNS          (-1L)
> >
> > +/* BPF_FUNC_skb_adjust_room flags. */
> > +#define BPF_F_ADJ_ROOM_FIXED_GSO     (1ULL << 0)
>
> minor nit - could we add this flag to the documentation for
> bpf_skb_adjust_room? Same suggestion for the encap flags in
> patch 8 too. Thanks!
>
> Reviewed-by: Alan Maguire <alan.maguire@...cle.com>

Definitely, will do in v2. Thanks.