skb_fclone_busy — check if fclone is busy
| bool skb_fclone_busy ( | const struct sock * sk, | 
| const struct sk_buff * skb ); | 
   Returns true is skb is a fast clone, and its clone is not freed.
   Some drivers call skb_orphan in their ndo_start_xmit,
   so we also check that this didnt happen.