pskb_expand_head — reallocate header of sk_buff
buffer to reallocate
room to add at head
room to add at tail
allocation priority
Expands (or creates identical copy, if nhead and ntail are zero) header of skb. sk_buff itself is not changed. sk_buff MUST have reference count of 1. Returns zero in the case of success or error, if expansion failed. In the last case, sk_buff is not changed.
All the pointers pointing into skb header may change and must be reloaded after call to this function.