ipv6: add ipv6_addr_hash() helper

Introduce ipv6_addr_hash() helper doing a XOR on all bits
of an IPv6 address, with an optimized x86_64 version.

Use it in flow dissector, as suggested by Andrew McGregor,
to reduce hash collision probabilities in fq_codel (and other
users of flow dissector)

Use it in ip6_tunnel.c and use more bit shuffling, as suggested
by David Laight, as existing hash was ignoring most of them.

Use it in sunrpc and use more bit shuffling, using hash_32().

Use it in net/ipv6/addrconf.c, using hash_32() as well.

As a cleanup, use it in net/ipv4/tcp_metrics.c

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrew McGregor <andrewmcgr@gmail.com>
Cc: Dave Taht <dave.taht@gmail.com>
Cc: Tom Herbert <therbert@google.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 8 deletions

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index db32846..9a1d5fe 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -40,6 +40,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/netfilter_ipv6.h>
 #include <linux/slab.h>
+#include <linux/hash.h>
 
 #include <asm/uaccess.h>
 #include <linux/atomic.h>
@@ -70,11 +71,15 @@ MODULE_ALIAS_NETDEV("ip6tnl0");
 #define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
 #define IPV6_TCLASS_SHIFT 20
 
-#define HASH_SIZE  32
+#define HASH_SIZE_SHIFT  5
+#define HASH_SIZE (1 << HASH_SIZE_SHIFT)
 
-#define HASH(addr) ((__force u32)((addr)->s6_addr32[0] ^ (addr)->s6_addr32[1] ^ \
-		     (addr)->s6_addr32[2] ^ (addr)->s6_addr32[3]) & \
-		    (HASH_SIZE - 1))
+static u32 HASH(const struct in6_addr *addr1, const struct in6_addr *addr2)
+{
+	u32 hash = ipv6_addr_hash(addr1) ^ ipv6_addr_hash(addr2);
+
+	return hash_32(hash, HASH_SIZE_SHIFT);
+}
 
 static int ip6_tnl_dev_init(struct net_device *dev);
 static void ip6_tnl_dev_setup(struct net_device *dev);
@@ -166,12 +171,11 @@ static inline void ip6_tnl_dst_store(struct ip6_tnl *t, struct dst_entry *dst)
 static struct ip6_tnl *
 ip6_tnl_lookup(struct net *net, const struct in6_addr *remote, const struct in6_addr *local)
 {
-	unsigned int h0 = HASH(remote);
-	unsigned int h1 = HASH(local);
+	unsigned int hash = HASH(remote, local);
 	struct ip6_tnl *t;
 	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 
-	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[h0 ^ h1]) {
+	for_each_ip6_tunnel_rcu(ip6n->tnls_r_l[hash]) {
 		if (ipv6_addr_equal(local, &t->parms.laddr) &&
 		    ipv6_addr_equal(remote, &t->parms.raddr) &&
 		    (t->dev->flags & IFF_UP))
@@ -205,7 +209,7 @@ ip6_tnl_bucket(struct ip6_tnl_net *ip6n, const struct ip6_tnl_parm *p)
 
 	if (!ipv6_addr_any(remote) || !ipv6_addr_any(local)) {
 		prio = 1;
-		h = HASH(remote) ^ HASH(local);
+		h = HASH(remote, local);
 	}
 	return &ip6n->tnls[prio][h];
 }