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ip_vs_sh with fixed hash shift
/*
* IPVS: Source Hashing scheduling module
*
* Authors: Wensong Zhang <wensong@gnuchina.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Changes:
* * Fix multiplicative hash to correctly divide by 2^32.
*
*/
/*
* The sh algorithm is to select server by the hash key of source IP
* address. The pseudo code is as follows:
*
* n <- servernode[src_ip];
* if (n is dead) OR
* (n is overloaded) or (n.weight <= 0) then
* return NULL;
*
* return n;
*
* Notes that servernode is a 256-bucket hash table that maps the hash
* index derived from packet source IP address to the current server
* array. If the sh scheduler is used in cache cluster, it is good to
* combine it with cache_bypass feature. When the statically assigned
* server is dead or overloaded, the load balancer can bypass the cache
* server and send requests to the original server directly.
*
* The weight destination attribute can be used to control the
* distribution of connections to the destinations in servernode. The
* greater the weight, the more connections the destination
* will receive.
*
*/
#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/ip.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <net/ip_vs.h>
#include <net/tcp.h>
#include <linux/udp.h>
#include <linux/sctp.h>
/*
* Sky stuff.
*/
MODULE_AUTHOR("Sky Core Team (DL-cirrus-core-engineering@bskyb.com)");
MODULE_DESCRIPTION("A modified sh scheduler with improved hash properties.");
MODULE_VERSION("0.1");
/*
* IPVS SH bucket
*/
struct ip_vs_sh_bucket {
struct ip_vs_dest __rcu *dest; /* real server (cache) */
};
/*
* for IPVS SH entry hash table
*/
#ifndef CONFIG_IP_VS_SH_TAB_BITS
#define CONFIG_IP_VS_SH_TAB_BITS 8
#endif
#define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS
#define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS)
#define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1)
struct ip_vs_sh_state {
struct rcu_head rcu_head;
struct ip_vs_sh_bucket buckets[IP_VS_SH_TAB_SIZE];
};
/* Helper function to determine if server is unavailable */
static inline bool is_unavailable(struct ip_vs_dest *dest)
{
return atomic_read(&dest->weight) <= 0 ||
dest->flags & IP_VS_DEST_F_OVERLOAD;
}
/*
* Returns hash value for IPVS SH entry
*/
static inline unsigned int
ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr,
__be16 port, unsigned int offset)
{
__be32 addr_fold = addr->ip;
#ifdef CONFIG_IP_VS_IPV6
if (af == AF_INET6)
addr_fold = addr->ip6[0]^addr->ip6[1]^
addr->ip6[2]^addr->ip6[3];
#endif
/* sky: fix by dividing by 2^32 */
return ((offset + (ntohs(port) + ntohl(addr_fold))*2654435761UL) >> 32) &
IP_VS_SH_TAB_MASK;
}
/*
* Get ip_vs_dest associated with supplied parameters.
*/
static inline struct ip_vs_dest *
ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
const union nf_inet_addr *addr, __be16 port)
{
unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest);
return (!dest || is_unavailable(dest)) ? NULL : dest;
}
/* As ip_vs_sh_get, but with fallback if selected server is unavailable
*
* The fallback strategy loops around the table starting from a "random"
* point (in fact, it is chosen to be the original hash value to make the
* algorithm deterministic) to find a new server.
*/
static inline struct ip_vs_dest *
ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
const union nf_inet_addr *addr, __be16 port)
{
unsigned int offset, roffset;
unsigned int hash, ihash;
struct ip_vs_dest *dest;
/* first try the dest it's supposed to go to */
ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
dest = rcu_dereference(s->buckets[ihash].dest);
if (!dest)
return NULL;
if (!is_unavailable(dest))
return dest;
IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
/* if the original dest is unavailable, loop around the table
* starting from ihash to find a new dest
*/
for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset);
dest = rcu_dereference(s->buckets[hash].dest);
if (!dest)
break;
if (!is_unavailable(dest))
return dest;
IP_VS_DBG_BUF(6, "SH: selected unavailable "
"server %s:%d (offset %d), reselecting",
IP_VS_DBG_ADDR(dest->af, &dest->addr),
ntohs(dest->port), roffset);
}
return NULL;
}
/*
* Assign all the hash buckets of the specified table with the service.
*/
static int
ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc)
{
int i;
struct ip_vs_sh_bucket *b;
struct list_head *p;
struct ip_vs_dest *dest;
int d_count;
bool empty;
b = &s->buckets[0];
p = &svc->destinations;
empty = list_empty(p);
d_count = 0;
for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
dest = rcu_dereference_protected(b->dest, 1);
if (dest)
ip_vs_dest_put(dest);
if (empty)
RCU_INIT_POINTER(b->dest, NULL);
else {
if (p == &svc->destinations)
p = p->next;
dest = list_entry(p, struct ip_vs_dest, n_list);
ip_vs_dest_hold(dest);
RCU_INIT_POINTER(b->dest, dest);
IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
i, IP_VS_DBG_ADDR(dest->af, &dest->addr),
atomic_read(&dest->weight));
/* Don't move to next dest until filling weight */
if (++d_count >= atomic_read(&dest->weight)) {
p = p->next;
d_count = 0;
}
}
b++;
}
return 0;
}
/*
* Flush all the hash buckets of the specified table.
*/
static void ip_vs_sh_flush(struct ip_vs_sh_state *s)
{
int i;
struct ip_vs_sh_bucket *b;
struct ip_vs_dest *dest;
b = &s->buckets[0];
for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
dest = rcu_dereference_protected(b->dest, 1);
if (dest) {
ip_vs_dest_put(dest);
RCU_INIT_POINTER(b->dest, NULL);
}
b++;
}
}
static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
{
struct ip_vs_sh_state *s;
/* allocate the SH table for this service */
s = kzalloc(sizeof(struct ip_vs_sh_state), GFP_KERNEL);
if (s == NULL)
return -ENOMEM;
svc->sched_data = s;
IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for "
"current service\n",
sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
/* assign the hash buckets with current dests */
ip_vs_sh_reassign(s, svc);
return 0;
}
static void ip_vs_sh_done_svc(struct ip_vs_service *svc)
{
struct ip_vs_sh_state *s = svc->sched_data;
/* got to clean up hash buckets here */
ip_vs_sh_flush(s);
/* release the table itself */
kfree_rcu(s, rcu_head);
IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n",
sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
}
static int ip_vs_sh_dest_changed(struct ip_vs_service *svc,
struct ip_vs_dest *dest)
{
struct ip_vs_sh_state *s = svc->sched_data;
/* assign the hash buckets with the updated service */
ip_vs_sh_reassign(s, svc);
return 0;
}
/* Helper function to get port number */
static inline __be16
ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
{
__be16 _ports[2], *ports;
/* At this point we know that we have a valid packet of some kind.
* Because ICMP packets are only guaranteed to have the first 8
* bytes, let's just grab the ports. Fortunately they're in the
* same position for all three of the protocols we care about.
*/
switch (iph->protocol) {
case IPPROTO_TCP:
case IPPROTO_UDP:
case IPPROTO_SCTP:
ports = skb_header_pointer(skb, iph->len, sizeof(_ports),
&_ports);
if (unlikely(!ports))
return 0;
if (likely(!ip_vs_iph_inverse(iph)))
return ports[0];
else
return ports[1];
default:
return 0;
}
}
/*
* Source Hashing scheduling
*/
static struct ip_vs_dest *
ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
struct ip_vs_iphdr *iph)
{
struct ip_vs_dest *dest;
struct ip_vs_sh_state *s;
__be16 port = 0;
const union nf_inet_addr *hash_addr;
hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT)
port = ip_vs_sh_get_port(skb, iph);
s = (struct ip_vs_sh_state *) svc->sched_data;
if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK)
dest = ip_vs_sh_get_fallback(svc, s, hash_addr, port);
else
dest = ip_vs_sh_get(svc, s, hash_addr, port);
if (!dest) {
ip_vs_scheduler_err(svc, "no destination available");
return NULL;
}
IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
IP_VS_DBG_ADDR(svc->af, hash_addr),
IP_VS_DBG_ADDR(dest->af, &dest->addr),
ntohs(dest->port));
return dest;
}
/*
* IPVS SH Scheduler structure
*/
static struct ip_vs_scheduler ip_vs_sh_scheduler =
{
.name = "coresh",
.refcnt = ATOMIC_INIT(0),
.module = THIS_MODULE,
.n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list),
.init_service = ip_vs_sh_init_svc,
.done_service = ip_vs_sh_done_svc,
.add_dest = ip_vs_sh_dest_changed,
.del_dest = ip_vs_sh_dest_changed,
.upd_dest = ip_vs_sh_dest_changed,
.schedule = ip_vs_sh_schedule,
};
static int __init ip_vs_sh_init(void)
{
return register_ip_vs_scheduler(&ip_vs_sh_scheduler);
}
static void __exit ip_vs_sh_cleanup(void)
{
unregister_ip_vs_scheduler(&ip_vs_sh_scheduler);
synchronize_rcu();
}
module_init(ip_vs_sh_init);
module_exit(ip_vs_sh_cleanup);
MODULE_LICENSE("GPL");
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