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netns: introduce the net_hash_mix "salt" for hashes

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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>
This commit is contained in:
Pavel Emelyanov 2008-06-16 17:14:11 -07:00 committed by David S. Miller
parent 33de014c63
commit 0b4419162a
5 changed files with 30 additions and 5 deletions
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3
include/linux/udp.h
View File

@ -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 {

3
include/net/inet6_hashtables.h
View File

@ -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)

5
include/net/inet_hashtables.h
View File

@ -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)

3
include/net/inet_sock.h
View File

@ -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)

21
include/net/netns/hash.h Normal file
View File

@ -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