Re: [PATCH bpf-next v3 4/5] bpf: Add helpers to issue and check SYN cookies in XDP

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Fri, Mar 11, 2022 at 8:36 AM Maxim Mikityanskiy <maximmi@nvidia.com> wrote:
>
> > -----Original Message-----
> > From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> > Sent: 27 February, 2022 05:25
> >
> > On Thu, Feb 24, 2022 at 05:11:44PM +0200, Maxim Mikityanskiy wrote:
> > > @@ -7798,6 +7916,14 @@ xdp_func_proto(enum bpf_func_id func_id, const
> > struct bpf_prog *prog)
> > >             return &bpf_tcp_check_syncookie_proto;
> > >     case BPF_FUNC_tcp_gen_syncookie:
> > >             return &bpf_tcp_gen_syncookie_proto;
> > > +   case BPF_FUNC_tcp_raw_gen_syncookie_ipv4:
> > > +           return &bpf_tcp_raw_gen_syncookie_ipv4_proto;
> > > +   case BPF_FUNC_tcp_raw_gen_syncookie_ipv6:
> > > +           return &bpf_tcp_raw_gen_syncookie_ipv6_proto;
> > > +   case BPF_FUNC_tcp_raw_check_syncookie_ipv4:
> > > +           return &bpf_tcp_raw_check_syncookie_ipv4_proto;
> > > +   case BPF_FUNC_tcp_raw_check_syncookie_ipv6:
> > > +           return &bpf_tcp_raw_check_syncookie_ipv6_proto;
> > >  #endif
> >
> > I understand that the main use case for new helpers is XDP specific,
> > but why limit them to XDP?
> > The feature looks generic and applicable to skb too.
>
> That sounds like an extra feature, rather than a limitation. That's out
> of scope of what I planned to do.
>
> Besides, it sounds kind of useless to me, because the intention of the
> new helpers is to accelerate synproxy, and I doubt BPF over SKBs will
> accelerate anything. Maybe someone else has another use case for these
> helpers and SKBs - in that case I leave the opportunity to add this
> feature up to them.

This patchset will not be accepted until the feature is generalized
to both xdp and skb and tested for both.
"I dont have a use case for it" is not an excuse to narrow down the scope.