Man page 9 : __pskb_pull_tail

__pskb_pull_tail - advance tail of skb header

unsigned char * __pskb_pull_tail(struct sk_buff *  skb , int  delta );

skb
    buffer to reallocate

delta
    number of bytes to advance tail

The function makes a sense only on a fragmented sk_buff, it expands header moving its tail forward and copying necessary data from fragmented part.

sk_buff MUST have reference count of 1.

Returns NULL (and sk_buff does not change) if pull failed or value of new tail of skb in the case of success.

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