skb_share_check — check if buffer is shared and if so clone it
buffer to check
priority for memory allocation
If the buffer is shared the buffer is cloned and the old copy drops a reference. A new clone with a single reference is returned. If the buffer is not shared the original buffer is returned. When being called from interrupt status or with spinlocks held pri must be GFP_ATOMIC.
NULL is returned on a memory allocation failure.