Provided by: linux-doc-2.6.15_2.6.15-23.39_all
skb_cow - copy header of skb when it is required
int skb_cow (struct sk_buff * skb, unsigned int headroom);
skb buffer to cow
If the skb passed lacks sufficient headroom or its data part is shared,
data is reallocated. If reallocation fails, an error is returned and
original skb is not changed.
The result is skb with writable area skb->head...skb->tail and at least
headroom of space at head.