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Message-ID: <1342620366.2626.2764.camel@edumazet-glaptop>
Date: Wed, 18 Jul 2012 16:06:06 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Laight <David.Laight@...LAB.COM>
Cc: David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Andrew McGregor <andrewmcgr@...il.com>,
Dave Taht <dave.taht@...il.com>,
Tom Herbert <therbert@...gle.com>
Subject: RE: [PATCH net-next] ipv6: add ipv6_addr_hash() helper
From: Eric Dumazet <edumazet@...gle.com>
On Wed, 2012-07-18 at 13:28 +0100, David Laight wrote:
> > #define HASH_SIZE 32
> >
> > -#define HASH(addr) ((__force u32)((addr)->s6_addr32[0] ^ (addr)->s6_addr32[1] ^ \
> > - (addr)->s6_addr32[2] ^ (addr)->s6_addr32[3]) & \
> > - (HASH_SIZE - 1))
> > +#define HASH(addr) (ipv6_addr_hash(addr) & (HASH_SIZE - 1))
>
> That hash doesn't seem to include many variable bits at all!
> Especially on LE systems where it doesn't contain any of
> the low bits of a mac address based IPv6 address.
>
Good point.
Apparently nobody uses a lot of ipv6 tunnels ;)
Thanks
[PATCH net-next v2] 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().
As cleanup, use it in net/ipv4/tcp_metrics.c
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Andrew McGregor <andrewmcgr@...il.com>
Cc: Dave Taht <dave.taht@...il.com>
Cc: Tom Herbert <therbert@...gle.com>
Cc: David Laight <David.Laight@...LAB.COM>
---
include/net/ipv6.h | 13 +++++++++++++
net/core/flow_dissector.c | 5 +++--
net/ipv4/tcp_metrics.c | 15 +++------------
net/ipv6/ip6_tunnel.c | 20 ++++++++++++--------
net/sunrpc/svcauth_unix.c | 22 ++++------------------
5 files changed, 35 insertions(+), 40 deletions(-)
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index f695f39..56ff725 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 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] |
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index a225089..466820b 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -4,6 +4,7 @@
#include <linux/ipv6.h>
#include <linux/if_vlan.h>
#include <net/ip.h>
+#include <net/ipv6.h>
#include <linux/if_tunnel.h>
#include <linux/if_pppox.h>
#include <linux/ppp_defs.h>
@@ -55,8 +56,8 @@ ipv6:
return false;
ip_proto = iph->nexthdr;
- flow->src = iph->saddr.s6_addr32[3];
- flow->dst = iph->daddr.s6_addr32[3];
+ flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
+ flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
nhoff += sizeof(struct ipv6hdr);
break;
}
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 5a38a2d..1a115b6 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -211,10 +211,7 @@ static struct tcp_metrics_block *__tcp_get_metrics_req(struct request_sock *req,
break;
case AF_INET6:
*(struct in6_addr *)addr.addr.a6 = inet6_rsk(req)->rmt_addr;
- hash = ((__force unsigned int) addr.addr.a6[0] ^
- (__force unsigned int) addr.addr.a6[1] ^
- (__force unsigned int) addr.addr.a6[2] ^
- (__force unsigned int) addr.addr.a6[3]);
+ hash = ipv6_addr_hash(&inet6_rsk(req)->rmt_addr);
break;
default:
return NULL;
@@ -251,10 +248,7 @@ static struct tcp_metrics_block *__tcp_get_metrics_tw(struct inet_timewait_sock
case AF_INET6:
tw6 = inet6_twsk((struct sock *)tw);
*(struct in6_addr *)addr.addr.a6 = tw6->tw_v6_daddr;
- hash = ((__force unsigned int) addr.addr.a6[0] ^
- (__force unsigned int) addr.addr.a6[1] ^
- (__force unsigned int) addr.addr.a6[2] ^
- (__force unsigned int) addr.addr.a6[3]);
+ hash = ipv6_addr_hash(&tw6->tw_v6_daddr);
break;
default:
return NULL;
@@ -291,10 +285,7 @@ static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
break;
case AF_INET6:
*(struct in6_addr *)addr.addr.a6 = inet6_sk(sk)->daddr;
- hash = ((__force unsigned int) addr.addr.a6[0] ^
- (__force unsigned int) addr.addr.a6[1] ^
- (__force unsigned int) addr.addr.a6[2] ^
- (__force unsigned int) addr.addr.a6[3]);
+ hash = ipv6_addr_hash(&inet6_sk(sk)->daddr);
break;
default:
return NULL;
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];
}
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 2777fa8..4d01292 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -104,23 +104,9 @@ static void ip_map_put(struct kref *kref)
kfree(im);
}
-#if IP_HASHBITS == 8
-/* hash_long on a 64 bit machine is currently REALLY BAD for
- * IP addresses in reverse-endian (i.e. on a little-endian machine).
- * So use a trivial but reliable hash instead
- */
-static inline int hash_ip(__be32 ip)
-{
- int hash = (__force u32)ip ^ ((__force u32)ip>>16);
- return (hash ^ (hash>>8)) & 0xff;
-}
-#endif
-static inline int hash_ip6(struct in6_addr ip)
+static inline int hash_ip6(const struct in6_addr *ip)
{
- return (hash_ip(ip.s6_addr32[0]) ^
- hash_ip(ip.s6_addr32[1]) ^
- hash_ip(ip.s6_addr32[2]) ^
- hash_ip(ip.s6_addr32[3]));
+ return hash_32(ipv6_addr_hash(ip), IP_HASHBITS);
}
static int ip_map_match(struct cache_head *corig, struct cache_head *cnew)
{
@@ -301,7 +287,7 @@ static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class,
ip.m_addr = *addr;
ch = sunrpc_cache_lookup(cd, &ip.h,
hash_str(class, IP_HASHBITS) ^
- hash_ip6(*addr));
+ hash_ip6(addr));
if (ch)
return container_of(ch, struct ip_map, h);
@@ -331,7 +317,7 @@ static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
ip.h.expiry_time = expiry;
ch = sunrpc_cache_update(cd, &ip.h, &ipm->h,
hash_str(ipm->m_class, IP_HASHBITS) ^
- hash_ip6(ipm->m_addr));
+ hash_ip6(&ipm->m_addr));
if (!ch)
return -ENOMEM;
cache_put(ch, cd);
--
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