2 * IPVS: Source Hashing scheduling module
4 * Authors: Wensong Zhang <wensong@gnuchina.org>
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
16 * The sh algorithm is to select server by the hash key of source IP
17 * address. The pseudo code is as follows:
19 * n <- servernode[src_ip];
21 * (n is overloaded) or (n.weight <= 0) then
26 * Notes that servernode is a 256-bucket hash table that maps the hash
27 * index derived from packet source IP address to the current server
28 * array. If the sh scheduler is used in cache cluster, it is good to
29 * combine it with cache_bypass feature. When the statically assigned
30 * server is dead or overloaded, the load balancer can bypass the cache
31 * server and send requests to the original server directly.
33 * The weight destination attribute can be used to control the
34 * distribution of connections to the destinations in servernode. The
35 * greater the weight, the more connections the destination
40 #define KMSG_COMPONENT "IPVS"
41 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
44 #include <linux/slab.h>
45 #include <linux/module.h>
46 #include <linux/kernel.h>
47 #include <linux/skbuff.h>
49 #include <net/ip_vs.h>
52 #include <linux/udp.h>
53 #include <linux/sctp.h>
59 struct ip_vs_sh_bucket {
60 struct ip_vs_dest __rcu *dest; /* real server (cache) */
64 * for IPVS SH entry hash table
66 #ifndef CONFIG_IP_VS_SH_TAB_BITS
67 #define CONFIG_IP_VS_SH_TAB_BITS 8
69 #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS
70 #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS)
71 #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1)
73 struct ip_vs_sh_state {
74 struct rcu_head rcu_head;
75 struct ip_vs_sh_bucket buckets[IP_VS_SH_TAB_SIZE];
78 /* Helper function to determine if server is unavailable */
79 static inline bool is_unavailable(struct ip_vs_dest *dest)
81 return atomic_read(&dest->weight) <= 0 ||
82 dest->flags & IP_VS_DEST_F_OVERLOAD;
86 * Returns hash value for IPVS SH entry
88 static inline unsigned int
89 ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr,
90 __be16 port, unsigned int offset)
92 __be32 addr_fold = addr->ip;
94 #ifdef CONFIG_IP_VS_IPV6
96 addr_fold = addr->ip6[0]^addr->ip6[1]^
97 addr->ip6[2]^addr->ip6[3];
99 return (offset + hash_32(ntohs(port) + ntohl(addr_fold),
100 IP_VS_SH_TAB_BITS)) &
106 * Get ip_vs_dest associated with supplied parameters.
108 static inline struct ip_vs_dest *
109 ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
110 const union nf_inet_addr *addr, __be16 port)
112 unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
113 struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest);
115 return (!dest || is_unavailable(dest)) ? NULL : dest;
119 /* As ip_vs_sh_get, but with fallback if selected server is unavailable
121 * The fallback strategy loops around the table starting from a "random"
122 * point (in fact, it is chosen to be the original hash value to make the
123 * algorithm deterministic) to find a new server.
125 static inline struct ip_vs_dest *
126 ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
127 const union nf_inet_addr *addr, __be16 port)
129 unsigned int offset, roffset;
130 unsigned int hash, ihash;
131 struct ip_vs_dest *dest;
133 /* first try the dest it's supposed to go to */
134 ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
135 dest = rcu_dereference(s->buckets[ihash].dest);
138 if (!is_unavailable(dest))
141 IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
142 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
144 /* if the original dest is unavailable, loop around the table
145 * starting from ihash to find a new dest
147 for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
148 roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
149 hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset);
150 dest = rcu_dereference(s->buckets[hash].dest);
153 if (!is_unavailable(dest))
155 IP_VS_DBG_BUF(6, "SH: selected unavailable "
156 "server %s:%d (offset %d), reselecting",
157 IP_VS_DBG_ADDR(dest->af, &dest->addr),
158 ntohs(dest->port), roffset);
165 * Assign all the hash buckets of the specified table with the service.
168 ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc)
171 struct ip_vs_sh_bucket *b;
173 struct ip_vs_dest *dest;
178 p = &svc->destinations;
179 empty = list_empty(p);
181 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
182 dest = rcu_dereference_protected(b->dest, 1);
184 ip_vs_dest_put(dest);
186 RCU_INIT_POINTER(b->dest, NULL);
188 if (p == &svc->destinations)
191 dest = list_entry(p, struct ip_vs_dest, n_list);
192 ip_vs_dest_hold(dest);
193 RCU_INIT_POINTER(b->dest, dest);
195 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
196 i, IP_VS_DBG_ADDR(dest->af, &dest->addr),
197 atomic_read(&dest->weight));
199 /* Don't move to next dest until filling weight */
200 if (++d_count >= atomic_read(&dest->weight)) {
213 * Flush all the hash buckets of the specified table.
215 static void ip_vs_sh_flush(struct ip_vs_sh_state *s)
218 struct ip_vs_sh_bucket *b;
219 struct ip_vs_dest *dest;
222 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
223 dest = rcu_dereference_protected(b->dest, 1);
225 ip_vs_dest_put(dest);
226 RCU_INIT_POINTER(b->dest, NULL);
233 static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
235 struct ip_vs_sh_state *s;
237 /* allocate the SH table for this service */
238 s = kzalloc(sizeof(struct ip_vs_sh_state), GFP_KERNEL);
243 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) allocated for "
245 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
247 /* assign the hash buckets with current dests */
248 ip_vs_sh_reassign(s, svc);
254 static void ip_vs_sh_done_svc(struct ip_vs_service *svc)
256 struct ip_vs_sh_state *s = svc->sched_data;
258 /* got to clean up hash buckets here */
261 /* release the table itself */
262 kfree_rcu(s, rcu_head);
263 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) released\n",
264 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
268 static int ip_vs_sh_dest_changed(struct ip_vs_service *svc,
269 struct ip_vs_dest *dest)
271 struct ip_vs_sh_state *s = svc->sched_data;
273 /* assign the hash buckets with the updated service */
274 ip_vs_sh_reassign(s, svc);
280 /* Helper function to get port number */
282 ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
284 __be16 _ports[2], *ports;
286 /* At this point we know that we have a valid packet of some kind.
287 * Because ICMP packets are only guaranteed to have the first 8
288 * bytes, let's just grab the ports. Fortunately they're in the
289 * same position for all three of the protocols we care about.
291 switch (iph->protocol) {
295 ports = skb_header_pointer(skb, iph->len, sizeof(_ports),
297 if (unlikely(!ports))
300 if (likely(!ip_vs_iph_inverse(iph)))
311 * Source Hashing scheduling
313 static struct ip_vs_dest *
314 ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
315 struct ip_vs_iphdr *iph)
317 struct ip_vs_dest *dest;
318 struct ip_vs_sh_state *s;
320 const union nf_inet_addr *hash_addr;
322 hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
324 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
326 if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT)
327 port = ip_vs_sh_get_port(skb, iph);
329 s = (struct ip_vs_sh_state *) svc->sched_data;
331 if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK)
332 dest = ip_vs_sh_get_fallback(svc, s, hash_addr, port);
334 dest = ip_vs_sh_get(svc, s, hash_addr, port);
337 ip_vs_scheduler_err(svc, "no destination available");
341 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
342 IP_VS_DBG_ADDR(svc->af, hash_addr),
343 IP_VS_DBG_ADDR(dest->af, &dest->addr),
351 * IPVS SH Scheduler structure
353 static struct ip_vs_scheduler ip_vs_sh_scheduler =
356 .refcnt = ATOMIC_INIT(0),
357 .module = THIS_MODULE,
358 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list),
359 .init_service = ip_vs_sh_init_svc,
360 .done_service = ip_vs_sh_done_svc,
361 .add_dest = ip_vs_sh_dest_changed,
362 .del_dest = ip_vs_sh_dest_changed,
363 .upd_dest = ip_vs_sh_dest_changed,
364 .schedule = ip_vs_sh_schedule,
368 static int __init ip_vs_sh_init(void)
370 return register_ip_vs_scheduler(&ip_vs_sh_scheduler);
374 static void __exit ip_vs_sh_cleanup(void)
376 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler);
381 module_init(ip_vs_sh_init);
382 module_exit(ip_vs_sh_cleanup);
383 MODULE_LICENSE("GPL");