pskb_copy — create copy of an sk_buff with private head.
| struct sk_buff * fsfuncpskb_copy ( | struct sk_buff * skb, | 
| gfp_t gfp_mask ); | 
   Make a copy of both an sk_buff and part of its data, located
   in header. Fragmented data remain shared. This is used when
   the caller wishes to modify only header of sk_buff and needs
   private copy of the header to alter. Returns NULL on failure
   or the pointer to the buffer on success.
   The returned buffer has a reference count of 1.