Re: [PATCHv6 bpf-next 2/3] sample/bpf: add xdp_redirect_map_multicast test

[Hangbin Liu]

On Fri, Jul 10, 2020 at 12:40:11AM +0200, Daniel Borkmann wrote:
> > +SEC("xdp_redirect_map_multi")
> > +int xdp_redirect_map_multi_prog(struct xdp_md *ctx)
> > +{
> > +   long *value;
> > +   u32 key = 0;
> > +
> > +   /* count packet in global counter */
> > +   value = bpf_map_lookup_elem(&rxcnt, &key);
> > +   if (value)
> > +           *value += 1;
> > +
> > +   return bpf_redirect_map_multi(&forward_map, &null_map,
> > +                                 BPF_F_EXCLUDE_INGRESS);
> 
> Why not extending to allow use-case like ...
> 
>   return bpf_redirect_map_multi(&fwd_map, NULL, BPF_F_EXCLUDE_INGRESS);
> 
> ... instead of requiring a dummy/'null' map?
> 

I planed to let user set NULL, but the arg2_type is ARG_CONST_MAP_PTR, which
not allow NULL pointer.

Thanks
Hangbin