Re: [PATCH bpf-next 2/4] bpf: Craft non-linear skbs in BPF_PROG_TEST_RUN

[Paul Chaignon <paul.chaignon@gmail.com>]

On Fri, Sep 05, 2025 at 09:34:54AM -0700, Amery Hung wrote:
> On Fri, Sep 5, 2025 at 6:24 AM Paul Chaignon <paul.chaignon@gmail.com> wrote:
> >
> > On Thu, Sep 04, 2025 at 09:27:58AM -0700, Amery Hung wrote:

[...]

> > > How about letting users specify the linear size through ctx->data_end? I am
> > > working on a set that introduces a kfunc, bpf_xdp_pull_data(). A part of is
> > > to support non-linear xdp_buff in test_run_xdp, and I am doing it through
> > > ctx->data_end. Is it something reasonable for test_run_skb?
> >
> > Oh, nice! That was next on my list :)
> >
> > Why use data_end though? I guess it'd work for skb, but can't we just
> > add a new field to the anonymous struct for BPF_PROG_TEST_RUN?
> >
> 
> I choose to use ctx_in because it doesn't change the interface and
> feels natural. kattr->test.ctx_in is already copied from users and
> shows users' expectation about the input ctx. I think we should honor
> that (as long as the value makes sense). WDYT?

Ok, I think I see your point of view. To me, test.ctx_in *is* the
context and not metadata about it. I'm worried it would be weird to
users if we overload that field. I'm not against using that though if
it's the consensus.

> 
> Thanks for working on this. It would be great if there is some
> consistency between test_run_skb and test_run_xdp.

Definitely agree! Do you have a prototype anywhere I could check? If
not, you can always flag any inconsistency when I send the v2.

[...]