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

On Thu, 10 Jul 2025 15:35:32 +0000 Song, Yoong Siang wrote:

Would it be advisable to update the documentation to indicate that drivers are expected to copy any device-reserved metadata from the metadata area? This would ensure that xdp_buff->data_meta is equal to xdp_buff->data before a BPF program is executed. This approach would allow BPF programs to freely manipulate the metadata area in XDP_REDIRECT scenarios.

Documenting sounds good.

Additionally, I am uncertain about the need to overriding metadata in XDP_PASS scenarios. Should BPF programs refrain from overriding the metadata in this case?

IIRC XDP_PASS was the initial use case for the metadata area. The driver needs to evacuate any HW metadata before handing over to the XDP program.