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

Daniel Borkmann
2020-07-10T14:32:38Z

On 7/10/20 8:41 AM, Hangbin Liu wrote:
> 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.

Right, but then why not adding a new type ARG_CONST_MAP_PTR_OR_NULL ?