The skb_queue_head_init function prepares an sk_buff_head for
use by the other skb_ functions, and should be called after
declaring and allocating memory for any sk_buff_head elements.
Specifically, skb_queue_head_init sets the prev and next
pointers of the list to point back at the list itself,
and sets the list length to 0. The use of sk_buff_head elements
which have not been initialized with this function is undocumented and
may produce irregular results.