Unexpected addr offset on handle_receive_packets

[DragosFalk]

I have a similar setup where I follow the same aproach like in [advanced03-AF_XDP] . I give the frames through the fill queue where lets say that the frames offsets(addr) are something like 0 2048 4096 and so on. When I get back the frames like via handle_receive_packets the addr that I get is shifted by 256 (0+256 2048+256 4096+256) . From what I read there is 256 XDP_HEADROOM but if I look in the memory it seems empty. My main question is it correct also in advanced03-AF_XDP the fact that when xsk_free_umem_frame(xsk, addr); is done to give back the frame it is done with the extra offset of 256 ?
Anyone else experienced this and can advise a bit on what is the proper way to handle this case?