On Mon, 20 Sep 2021 23:01:48 +0200 Toke Høiland-Jørgensen wrote:
> > In fact I don't think there is anything infra can do better for
> > flushing than the prog itself:
> >
> > bool mod = false;
> >
> > ptr = bpf_header_pointer(...);
> > ...
> > if (some_cond(...)) {
> > change_packet(...);
> > mod = true;
> > }
> > ...
> > if (mod)
>
> to have an additional check like:
>
> if (mod && ptr == stack)
>
> (or something to that effect). No?
Good point. Do you think we should have the kernel add/inline this
optimization or have the user do it explicitly.
The draft API was:
void *xdp_mb_pointer_flush(struct xdp_buff *xdp_md, u32 flags,
u32 offset, u32 len, void *stack_buf)
Which does not take the ptr returned by header_pointer(), but that's
easy to add (well, easy other than the fact it'd be the 6th arg).
BTW I drafted the API this way to cater to the case where flush()
is called without a prior call to header_pointer(). For when packet
trailer or header is populated directly from a map value. Dunno if
that's actually useful, either.
