On Fri, Sep 17, 2021 at 11:33 AM Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > > > > > > Alternatively how about we produce a variation on skb_header_pointer() > > > (use on-stack buffer or direct access if the entire region is in one > > > frag). > > If bpf_xdp_load_bytes() / bpf_xdp_store_bytes() works for most we > can start with that. In all honesty I don't know what the exact > use cases for looking at data are, either. I'm primarily worried > about exposing the kernel internals too early. I don't mind the xdp equivalent of skb_load_bytes, but skb_header_pointer() idea is superior. When we did xdp with data/data_end there was no refine_retval_range concept in the verifier (iirc or we just missed that opportunity). We'd need something more advanced: a pointer with valid range refined by input argument 'len' or NULL. The verifier doesn't have such thing yet, but it fits as a combination of value_or_null plus refine_retval_range. The bpf_xdp_header_pointer() and bpf_skb_header_pointer() would probably simplify bpf programs as well. There would be no need to deal with data/data_end.
