[PATCH] add likely/unlikely to pskb_may_pull

Code that deals with received headers needs to be robust and use pskb_may_pull 
in many
places, but except in the case of DOS attacks, the packets are always correctly 
formed
so optimize for that case.

diff -Nru a/include/linux/skbuff.h b/include/linux/skbuff.h
--- a/include/linux/skbuff.h    Wed Jul 30 15:50:31 2003
+++ b/include/linux/skbuff.h    Wed Jul 30 15:50:31 2003
@@ -904,9 +904,9 @@
 
 static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
 {
-       if (len <= skb_headlen(skb))
+       if (likely(len <= skb_headlen(skb)))
                return 1;
-       if (len > skb->len)
+       if (unlikely(len > skb->len))
                return 0;
        return __pskb_pull_tail(skb, len-skb_headlen(skb)) != NULL;
 }