BPF_CALL_2(bpf_skb_pull_data, struct sk_buff *, skb, u32, len)
{
	/* Idea is the following: should the needed direct read/write
	 * test fail during runtime, we can pull in more data and redo
	 * again, since implicitly, we invalidate previous checks here.
	 *
	 * Or, since we know how much we need to make read/writeable,
	 * this can be done once at the program beginning for direct
	 * access case. By this we overcome limitations of only current
	 * headroom being accessible.
	 */
	return bpf_try_make_writable(skb, len ? : skb_headlen(skb));
}
Unknown