Skb_cow but only making the head writable
int skb_cow_head(struct sk_buff * skb, unsigned int headroom);
skb
buffer to cow
headroom
needed headroom
This function is identical to skb_cow except that we replace the skb_cloned check by skb_header_cloned. It should be used when you only need to push on some header and do not need to modify the data.