neigh: Factor out ___neigh_lookup_noref

While looking at the mpls code I found myself writing yet another
version of neigh_lookup_noref.  We currently have __ipv4_lookup_noref
and __ipv6_lookup_noref.

So to make my work a little easier and to make it a smidge easier to
verify/maintain the mpls code in the future I stopped and wrote
___neigh_lookup_noref.  Then I rewote __ipv4_lookup_noref and
__ipv6_lookup_noref in terms of this new function.  I tested my new
version by verifying that the same code is generated in
ip_finish_output2 and ip6_finish_output2 where these functions are
inlined.

To get to ___neigh_lookup_noref I added a new neighbour cache table
function key_eq.  So that the static size of the key would be
available.

I also added __neigh_lookup_noref for people who want to to lookup
a neighbour table entry quickly but don't know which neibhgour table
they are going to look up.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 6b8aad6a..5f5c674 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -122,6 +122,7 @@
  *	Interface to generic neighbour cache.
  */
 static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 *hash_rnd);
+static bool arp_key_eq(const struct neighbour *n, const void *pkey);
 static int arp_constructor(struct neighbour *neigh);
 static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
 static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
@@ -154,6 +155,7 @@
 	.key_len	= 4,
 	.protocol	= cpu_to_be16(ETH_P_IP),
 	.hash		= arp_hash,
+	.key_eq		= arp_key_eq,
 	.constructor	= arp_constructor,
 	.proxy_redo	= parp_redo,
 	.id		= "arp_cache",
@@ -209,7 +211,12 @@
 		    const struct net_device *dev,
 		    __u32 *hash_rnd)
 {
-	return arp_hashfn(*(u32 *)pkey, dev, *hash_rnd);
+	return arp_hashfn(pkey, dev, hash_rnd);
+}
+
+static bool arp_key_eq(const struct neighbour *neigh, const void *pkey)
+{
+	return neigh_key_eq32(neigh, pkey);
 }
 
 static int arp_constructor(struct neighbour *neigh)