netdev - Re: [RFC bpf-next v2 1/9] net: introduce __init_skb{,_data,

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Date:   Thu, 21 Mar 2019 12:13:13 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Stanislav Fomichev <sdf@...ichev.me>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf@...r.kernel.org, David Miller <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        simon.horman@...ronome.com, Willem de Bruijn <willemb@...gle.com>,
        Petar Penkov <peterpenkov96@...il.com>
Subject: Re: [RFC bpf-next v2 1/9] net: introduce __init_skb{,_data,_shinfo} helpers

On Thu, Mar 21, 2019 at 12:01 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Thu, Mar 21, 2019 at 08:44:33AM -0700, Stanislav Fomichev wrote:
> >
> > If we can agree that we switch everything to xpd-like, do we deprecate the
> > skb-one?
>
> This whole discussion that have been going on for long time is an indication
> that initial bpf flow dissector concept was not thought through
> and I regret on merging it in the first place.
> Adding more hacks on top of it with fake skbs is not going to make it any better.
> Since it's been in the official release we cannot remove it now.

This patch set addresses the only open issue.

That said, if direction is towards an alternative interface, then it would
make sense for the new interface to supplant the existing one for all
use-cases, even if that existing one cannot be removed.

Essentially a BPF_PROG_TYPE_FLOW_DISSECTOR_RAW that
takes a simpler context than skb. And either that or a program of
type BPF_PROG_TYPE_FLOW_DISSECTOR can be attached in
skb_flow_dissector_bpf_prog_attach, but not both.