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>

1 files changed, 4 insertions, 15 deletions

diff --git a/include/net/arp.h b/include/net/arp.h
index 21ee1860abbc..5e0f891d476c 100644
--- a/include/net/arp.h
+++ b/include/net/arp.h
@@ -9,28 +9,17 @@
 
 extern struct neigh_table arp_tbl;
 
-static inline u32 arp_hashfn(u32 key, const struct net_device *dev, u32 hash_rnd)
+static inline u32 arp_hashfn(const void *pkey, const struct net_device *dev, u32 *hash_rnd)
 {
+        u32 key = *(const u32 *)pkey;
         u32 val = key ^ hash32_ptr(dev);
 
-        return val * hash_rnd;
+        return val * hash_rnd[0];
 }
 
 static inline struct neighbour *__ipv4_neigh_lookup_noref(struct net_device *dev, u32 key)
 {
-        struct neigh_hash_table *nht = rcu_dereference_bh(arp_tbl.nht);
-        struct neighbour *n;
-        u32 hash_val;
-
-        hash_val = arp_hashfn(key, dev, nht->hash_rnd[0]) >> (32 - nht->hash_shift);
-        for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);
-             n != NULL;
-             n = rcu_dereference_bh(n->next)) {
-                if (n->dev == dev && *(u32 *)n->primary_key == key)
-                        return n;
-        }
-
-        return NULL;
+        return ___neigh_lookup_noref(&arp_tbl, neigh_key_eq32, arp_hashfn, &key, dev);
 }
 
 static inline struct neighbour *__ipv4_neigh_lookup(struct net_device *dev, u32 key)