centos man page for skb_headroom

SKB_HEADROOM(9) 						 Linux Networking						   SKB_HEADROOM(9)

NAME
       skb_headroom - bytes at buffer head

SYNOPSIS
       unsigned int skb_headroom(const struct sk_buff * skb);

ARGUMENTS
       skb
	   buffer to check

DESCRIPTION
       Return the number of bytes of free space at the head of an sk_buff.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							   SKB_HEADROOM(9)