[xdp-hints] Re: [PATCH bpf-next 06/11] xdp: Carry over xdp metadata into skb context

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Stanislav Fomichev <sdf@google.com> writes:

> On Tue, Nov 15, 2022 at 3:20 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> > index b444b1118c4f..71e3bc7ad839 100644
>> > --- a/include/uapi/linux/bpf.h
>> > +++ b/include/uapi/linux/bpf.h
>> > @@ -6116,6 +6116,12 @@ enum xdp_action {
>> >       XDP_REDIRECT,
>> >  };
>> >
>> > +/* Subset of XDP metadata exported to skb context.
>> > + */
>> > +struct xdp_skb_metadata {
>> > +     __u64 rx_timestamp;
>> > +};
>>
>> Okay, so given Alexei's comment about __randomize_struct not actually
>> working, I think we need to come up with something else for this. Just
>> sticking this in a regular UAPI header seems like a bad idea; we'd just
>> be inviting people to use it as-is.
>>
>> Do we actually need the full definition here? It's just a pointer
>> declaration below, so is an opaque forward-definition enough? Then we
>> could have the full definition in an internal header, moving the full
>> definition back to being in vmlinux.h only?
>
> Looks like having a uapi-declaration only (and moving the definition
> into the kernel headers) might work. At least it does in my limited
> testing :-) So let's go with that for now. Alexei, thanks for the
> context on __randomize_struct!

Sounds good! :)

-Toke