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, 13 insertions, 0 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index f695f39..01c34b3 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -419,6 +419,19 @@ static inline bool ipv6_addr_any(const struct in6_addr *a)
 #endif
 }
 
+static inline u32 ipv6_addr_hash(const struct in6_addr *a)
+{
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
+	const unsigned long *ul = (const unsigned long *)a;
+	unsigned long x = ul[0] ^ ul[1];
+
+	return (u32)(x ^ (x >> 32));
+#else
+	return (__force u32)(a->s6_addr32[0] ^ a->s6_addr32[1] ^
+			     a->s6_addr32[2] ^ a->s6_addr32[3]);
+#endif
+}
+
 static inline bool ipv6_addr_loopback(const struct in6_addr *a)
 {
 	return (a->s6_addr32[0] | a->s6_addr32[1] |