RE: [PATCH bpf-next,v3 2/2] selftests/bpf: Enhance XDP Rx metadata handling

[Song, Yoong Siang]

On Friday, July 4, 2025 1:05 AM, Jesper Dangaard Brouer <hawk@xxxxxxxxxx> wrote:
>On 02/07/2025 18.57, Song Yoong Siang wrote:
>> Introduce the XDP_METADATA_SIZE macro as a conservative measure to
>> accommodate any metadata areas reserved by Ethernet devices.
>>
>
>This seems like a sloppy workaround :-(
>
>To me, the problem arise because AF_XDP is lacking the ability to
>communicate the size of the data_meta area.  If we had this capability,
>then we could allow the IGC driver to take some of the space, have the
>BPF-prog expand it futher (bpf_xdp_adjust_meta) and then userspace
>AF_XDP would simply be able to see the size of the data_meta area, and
>apply the struct xdp_meta at right offset.
>
Thanks for your input.

I agree with you that the implementation will be simple if user application
able to get the size of data_meta area. The intention of this patch set is to let
developer aware of such limitations before we have a perfect solution.

Btw, do you got any suggestion on how to expose the metadata length?
I not sure whether xdp_desc.options is a simple and good idea or not?