BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
{
	unsigned long metalen = xdp_get_metalen(xdp);
	void *data_start = xdp->data_hard_start + metalen;
	void *data = xdp->data + offset;

	if (unlikely(data < data_start ||
		     data > xdp->data_end - ETH_HLEN))
		return -EINVAL;

	if (metalen)
		memmove(xdp->data_meta + offset,
			xdp->data_meta, metalen);
	xdp->data_meta += offset;
	xdp->data = data;

	return 0;
}
Unknown