suse man page for skb_cow_data

SKB_COW_DATA(9) 						 Linux Networking						   SKB_COW_DATA(9)

NAME
       skb_cow_data - Check that a socket buffer's data buffers are writable

SYNOPSIS
       int skb_cow_data(struct sk_buff * skb, int tailbits, struct sk_buff ** trailer);

ARGUMENTS
       skb
	   The socket buffer to check.

       tailbits
	   Amount of trailing space to be added

       trailer
	   Returned pointer to the skb where the tailbits space begins

DESCRIPTION
       Make sure that the data buffers attached to a socket buffer are writable. If they are not, private copies are made of the data buffers and
       the socket buffer is set to use these instead.

       If tailbits is given, make sure that there is space to write tailbits bytes of data beyond current end of socket buffer.  trailer will be
       set to point to the skb in which this space begins.

       The number of scatterlist elements required to completely map the COW'd and extended socket buffer will be returned.

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010							   SKB_COW_DATA(9)