On 18/08/02 (木) 20:45, Jesper Dangaard Brouer wrote:

On Thu,  2 Aug 2018 19:55:09 +0900
Toshiaki Makita [off-list ref] wrote:

quoted

+	headroom = frame->data - delta - (void *)frame;

Your calculation of headroom is still adding an assumption that
xdp_frame is located in the top of data area, that is unnecessary.

The headroom can be calculated as:

  headroom = sizeof(struct xdp_frame) + frame->headroom - delta;

Thanks. But I'm not sure I get what you are requesting.
Supposing xdp_frame is not located in the top of data area, what ensures 
that additional sizeof(struct xdp_frame) can be used?

Toshiaki Makita