centos man page for pskb_expand_head

PSKB_EXPAND_HEAD(9)						 Linux Networking					       PSKB_EXPAND_HEAD(9)

NAME
       pskb_expand_head - reallocate header of sk_buff

SYNOPSIS
       int pskb_expand_head(struct sk_buff * skb, int nhead, int ntail, gfp_t gfp_mask);

ARGUMENTS
       skb
	   buffer to reallocate

       nhead
	   room to add at head

       ntail
	   room to add at tail

       gfp_mask
	   allocation priority

DESCRIPTION
       Expands (or creates identical copy, if nhead and ntail are zero) header of skb.	sk_buff itself is not changed.	sk_buff MUST have
       reference count of 1. Returns zero in the case of success or error, if expansion failed. In the last case, sk_buff is not changed.

       All the pointers pointing into skb header may change and must be reloaded after call to this function.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						       PSKB_EXPAND_HEAD(9)