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- /*
- * 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:
- *
- */
- /*
- * 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>
- /*
- * 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
- return (offset + (ntohs(port) + ntohl(addr_fold))*2654435761UL) &
- 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 = "sh",
- .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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