netns: introduce the net_hash_mix "salt" for hashes

There are many possible ways to add this "salt", thus I made this
patch to be the last in the series to change it if required.

Currently I propose to use the struct net pointer itself as this 
salt, but since this pointer is most often cache-line aligned, shift 
this right to eliminate the bits, that are most often zeroed.

After this, simply add this mix to prepared hashfn-s.

For CONFIG_NET_NS=n case this salt is 0 and no changes in hashfn
appear.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 26336cdcdc11..bb619d80f2e2 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -29,6 +29,7 @@
 #include <net/inet_sock.h>
 #include <net/sock.h>
 #include <net/tcp_states.h>
+#include <net/netns/hash.h>
 
 #include <asm/atomic.h>
 #include <asm/byteorder.h>
@@ -204,7 +205,7 @@ extern void inet_bind_bucket_destroy(struct kmem_cache *cachep,
 static inline int inet_bhashfn(struct net *net,
                 const __u16 lport, const int bhash_size)
 {
-        return lport & (bhash_size - 1);
+        return (lport + net_hash_mix(net)) & (bhash_size - 1);
 }
 
 extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
@@ -213,7 +214,7 @@ extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 /* These can have wildcards, don't try too hard. */
 static inline int inet_lhashfn(struct net *net, const unsigned short num)
 {
-        return num & (INET_LHTABLE_SIZE - 1);
+        return (num + net_hash_mix(net)) & (INET_LHTABLE_SIZE - 1);
 }
 
 static inline int inet_sk_listen_hashfn(const struct sock *sk)