netns: introduce the net_hash_mix "salt" for hashes

xemul · davem330 · commit 0b4419162aa6 · 2008-06-16T17:14:11.000-07:00
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 &lt;xemul@openvz.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/include/linux/udp.h b/include/linux/udp.h
@@ -38,6 +38,7 @@ struct udphdr {
 #ifdef __KERNEL__
 #include <net/inet_sock.h>
 #include <linux/skbuff.h>
+#include <net/netns/hash.h>
 
 static inline struct udphdr *udp_hdr(const struct sk_buff *skb)
 {
@@ -48,7 +49,7 @@ static inline struct udphdr *udp_hdr(const struct sk_buff *skb)
 
 static inline int udp_hashfn(struct net *net, const unsigned num)
 {
-	return num & (UDP_HTABLE_SIZE - 1);
+	return (num + net_hash_mix(net)) & (UDP_HTABLE_SIZE - 1);
 }
 
 struct udp_sock {
diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
@@ -24,6 +24,7 @@
 #include <net/inet_sock.h>
 
 #include <net/ipv6.h>
+#include <net/netns/hash.h>
 
 struct inet_hashinfo;
 
@@ -36,7 +37,7 @@ static inline unsigned int inet6_ehashfn(struct net *net,
 
 	return jhash_3words((__force u32)laddr->s6_addr32[3],
 			    (__force u32)faddr->s6_addr32[3],
-			    ports, inet_ehash_secret);
+			    ports, inet_ehash_secret + net_hash_mix(net));
 }
 
 static inline int inet6_sk_ehashfn(const struct sock *sk)
diff --git 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)
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
@@ -25,6 +25,7 @@
 #include <net/sock.h>
 #include <net/request_sock.h>
 #include <net/route.h>
+#include <net/netns/hash.h>
 
 /** struct ip_options - IP Options
  *
@@ -178,7 +179,7 @@ static inline unsigned int inet_ehashfn(struct net *net,
 	return jhash_3words((__force __u32) laddr,
 			    (__force __u32) faddr,
 			    ((__u32) lport) << 16 | (__force __u32)fport,
-			    inet_ehash_secret);
+			    inet_ehash_secret + net_hash_mix(net));
 }
 
 static inline int inet_sk_ehashfn(const struct sock *sk)
diff --git a/include/net/netns/hash.h b/include/net/netns/hash.h
@@ -0,0 +1,21 @@
+#ifndef __NET_NS_HASH_H__
+#define __NET_NS_HASH_H__
+
+#include <asm/cache.h>
+
+struct net;
+
+static inline unsigned net_hash_mix(struct net *net)
+{
+#ifdef CONFIG_NET_NS
+	/*
+	 * shift this right to eliminate bits, that are
+	 * always zeroed
+	 */
+
+	return (unsigned)(((unsigned long)net) >> L1_CACHE_SHIFT);
+#else
+	return 0;
+#endif
+}
+#endif

Original file line number	Diff line number	Diff line change
`@@ -38,6 +38,7 @@ struct udphdr {`
`38`	`38`	`#ifdef __KERNEL__`
`39`	`39`	`#include <net/inet_sock.h>`
`40`	`40`	`#include <linux/skbuff.h>`
	`41`	`+#include <net/netns/hash.h>`
`41`	`42`
`42`	`43`	`static inline struct udphdr udp_hdr(const struct sk_buff skb)`
`43`	`44`	`{`
`@@ -48,7 +49,7 @@ static inline struct udphdr udp_hdr(const struct sk_buff skb)`
`48`	`49`
`49`	`50`	`static inline int udp_hashfn(struct net *net, const unsigned num)`
`50`	`51`	`{`
`51`		`- return num & (UDP_HTABLE_SIZE - 1);`
	`52`	`+ return (num + net_hash_mix(net)) & (UDP_HTABLE_SIZE - 1);`
`52`	`53`	`}`
`53`	`54`
`54`	`55`	`struct udp_sock {`
Original file line number	Diff line number	Diff line change
`@@ -29,6 +29,7 @@`
`29`	`29`	`#include <net/inet_sock.h>`
`30`	`30`	`#include <net/sock.h>`
`31`	`31`	`#include <net/tcp_states.h>`
	`32`	`+#include <net/netns/hash.h>`
`32`	`33`
`33`	`34`	`#include <asm/atomic.h>`
`34`	`35`	`#include <asm/byteorder.h>`
`@@ -204,7 +205,7 @@ extern void inet_bind_bucket_destroy(struct kmem_cache *cachep,`
`204`	`205`	`static inline int inet_bhashfn(struct net *net,`
`205`	`206`	`const __u16 lport, const int bhash_size)`
`206`	`207`	`{`
`207`		`- return lport & (bhash_size - 1);`
	`208`	`+ return (lport + net_hash_mix(net)) & (bhash_size - 1);`
`208`	`209`	`}`
`209`	`210`
`210`	`211`	`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,`
`213`	`214`	`/* These can have wildcards, don't try too hard. */`
`214`	`215`	`static inline int inet_lhashfn(struct net *net, const unsigned short num)`
`215`	`216`	`{`
`216`		`- return num & (INET_LHTABLE_SIZE - 1);`
	`217`	`+ return (num + net_hash_mix(net)) & (INET_LHTABLE_SIZE - 1);`
`217`	`218`	`}`
`218`	`219`
`219`	`220`	`static inline int inet_sk_listen_hashfn(const struct sock *sk)`
Original file line number	Diff line number	Diff line change
`@@ -25,6 +25,7 @@`
`25`	`25`	`#include <net/sock.h>`
`26`	`26`	`#include <net/request_sock.h>`
`27`	`27`	`#include <net/route.h>`
	`28`	`+#include <net/netns/hash.h>`
`28`	`29`
`29`	`30`	`/** struct ip_options - IP Options`
`30`	`31`	`*`
`@@ -178,7 +179,7 @@ static inline unsigned int inet_ehashfn(struct net *net,`
`178`	`179`	`return jhash_3words((__force __u32) laddr,`
`179`	`180`	`(__force __u32) faddr,`
`180`	`181`	`((__u32) lport) << 16 \| (__force __u32)fport,`
`181`		`- inet_ehash_secret);`
	`182`	`+ inet_ehash_secret + net_hash_mix(net));`
`182`	`183`	`}`
`183`	`184`
`184`	`185`	`static inline int inet_sk_ehashfn(const struct sock *sk)`