1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * IPVS: Locality-Based Least-Connection scheduling module
5 * Authors: Wensong Zhang <wensong@gnuchina.org>
8 * Martin Hamilton : fixed the terrible locking bugs
9 * *lock(tbl->lock) ==> *lock(&tbl->lock)
10 * Wensong Zhang : fixed the uninitialized tbl->lock bug
11 * Wensong Zhang : added doing full expiration check to
12 * collect stale entries of 24+ hours when
13 * no partial expire check in a half hour
14 * Julian Anastasov : replaced del_timer call with del_timer_sync
15 * to avoid the possible race between timer
16 * handler and del_timer thread in SMP
20 * The lblc algorithm is as follows (pseudo code):
22 * if cachenode[dest_ip] is null then
23 * n, cachenode[dest_ip] <- {weighted least-conn node};
25 * n <- cachenode[dest_ip];
27 * (n.conns>n.weight AND
28 * there is a node m with m.conns<m.weight/2) then
29 * n, cachenode[dest_ip] <- {weighted least-conn node};
33 * Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
34 * me to write this module.
37 #define KMSG_COMPONENT "IPVS"
38 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
41 #include <linux/slab.h>
42 #include <linux/module.h>
43 #include <linux/kernel.h>
44 #include <linux/skbuff.h>
45 #include <linux/jiffies.h>
46 #include <linux/hash.h>
50 #include <linux/sysctl.h>
52 #include <net/ip_vs.h>
56 * It is for garbage collection of stale IPVS lblc entries,
57 * when the table is full.
59 #define CHECK_EXPIRE_INTERVAL (60*HZ)
60 #define ENTRY_TIMEOUT (6*60*HZ)
62 #define DEFAULT_EXPIRATION (24*60*60*HZ)
65 * It is for full expiration check.
66 * When there is no partial expiration check (garbage collection)
67 * in a half hour, do a full expiration check to collect stale
68 * entries that haven't been touched for a day.
70 #define COUNT_FOR_FULL_EXPIRATION 30
74 * for IPVS lblc entry hash table
76 #ifndef CONFIG_IP_VS_LBLC_TAB_BITS
77 #define CONFIG_IP_VS_LBLC_TAB_BITS 10
79 #define IP_VS_LBLC_TAB_BITS CONFIG_IP_VS_LBLC_TAB_BITS
80 #define IP_VS_LBLC_TAB_SIZE (1 << IP_VS_LBLC_TAB_BITS)
81 #define IP_VS_LBLC_TAB_MASK (IP_VS_LBLC_TAB_SIZE - 1)
85 * IPVS lblc entry represents an association between destination
86 * IP address and its destination server
88 struct ip_vs_lblc_entry {
89 struct hlist_node list;
90 int af; /* address family */
91 union nf_inet_addr addr; /* destination IP address */
92 struct ip_vs_dest *dest; /* real server (cache) */
93 unsigned long lastuse; /* last used time */
94 struct rcu_head rcu_head;
99 * IPVS lblc hash table
101 struct ip_vs_lblc_table {
102 struct rcu_head rcu_head;
103 struct hlist_head bucket[IP_VS_LBLC_TAB_SIZE]; /* hash bucket */
104 struct timer_list periodic_timer; /* collect stale entries */
105 struct ip_vs_service *svc; /* pointer back to service */
106 atomic_t entries; /* number of entries */
107 int max_size; /* maximum size of entries */
108 int rover; /* rover for expire check */
109 int counter; /* counter for no expire */
115 * IPVS LBLC sysctl table
118 static struct ctl_table vs_vars_table[] = {
120 .procname = "lblc_expiration",
122 .maxlen = sizeof(int),
124 .proc_handler = proc_dointvec_jiffies,
130 static void ip_vs_lblc_rcu_free(struct rcu_head *head)
132 struct ip_vs_lblc_entry *en = container_of(head,
133 struct ip_vs_lblc_entry,
136 ip_vs_dest_put_and_free(en->dest);
140 static inline void ip_vs_lblc_del(struct ip_vs_lblc_entry *en)
142 hlist_del_rcu(&en->list);
143 call_rcu(&en->rcu_head, ip_vs_lblc_rcu_free);
147 * Returns hash value for IPVS LBLC entry
149 static inline unsigned int
150 ip_vs_lblc_hashkey(int af, const union nf_inet_addr *addr)
152 __be32 addr_fold = addr->ip;
154 #ifdef CONFIG_IP_VS_IPV6
156 addr_fold = addr->ip6[0]^addr->ip6[1]^
157 addr->ip6[2]^addr->ip6[3];
159 return hash_32(ntohl(addr_fold), IP_VS_LBLC_TAB_BITS);
164 * Hash an entry in the ip_vs_lblc_table.
165 * returns bool success.
168 ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
170 unsigned int hash = ip_vs_lblc_hashkey(en->af, &en->addr);
172 hlist_add_head_rcu(&en->list, &tbl->bucket[hash]);
173 atomic_inc(&tbl->entries);
177 /* Get ip_vs_lblc_entry associated with supplied parameters. */
178 static inline struct ip_vs_lblc_entry *
179 ip_vs_lblc_get(int af, struct ip_vs_lblc_table *tbl,
180 const union nf_inet_addr *addr)
182 unsigned int hash = ip_vs_lblc_hashkey(af, addr);
183 struct ip_vs_lblc_entry *en;
185 hlist_for_each_entry_rcu(en, &tbl->bucket[hash], list)
186 if (ip_vs_addr_equal(af, &en->addr, addr))
194 * Create or update an ip_vs_lblc_entry, which is a mapping of a destination IP
195 * address to a server. Called under spin lock.
197 static inline struct ip_vs_lblc_entry *
198 ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
199 u16 af, struct ip_vs_dest *dest)
201 struct ip_vs_lblc_entry *en;
203 en = ip_vs_lblc_get(af, tbl, daddr);
205 if (en->dest == dest)
209 en = kmalloc(sizeof(*en), GFP_ATOMIC);
214 ip_vs_addr_copy(af, &en->addr, daddr);
215 en->lastuse = jiffies;
217 ip_vs_dest_hold(dest);
220 ip_vs_lblc_hash(tbl, en);
227 * Flush all the entries of the specified table.
229 static void ip_vs_lblc_flush(struct ip_vs_service *svc)
231 struct ip_vs_lblc_table *tbl = svc->sched_data;
232 struct ip_vs_lblc_entry *en;
233 struct hlist_node *next;
236 spin_lock_bh(&svc->sched_lock);
238 for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
239 hlist_for_each_entry_safe(en, next, &tbl->bucket[i], list) {
241 atomic_dec(&tbl->entries);
244 spin_unlock_bh(&svc->sched_lock);
247 static int sysctl_lblc_expiration(struct ip_vs_service *svc)
250 return svc->ipvs->sysctl_lblc_expiration;
252 return DEFAULT_EXPIRATION;
256 static inline void ip_vs_lblc_full_check(struct ip_vs_service *svc)
258 struct ip_vs_lblc_table *tbl = svc->sched_data;
259 struct ip_vs_lblc_entry *en;
260 struct hlist_node *next;
261 unsigned long now = jiffies;
264 for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
265 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
267 spin_lock(&svc->sched_lock);
268 hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
271 sysctl_lblc_expiration(svc)))
275 atomic_dec(&tbl->entries);
277 spin_unlock(&svc->sched_lock);
284 * Periodical timer handler for IPVS lblc table
285 * It is used to collect stale entries when the number of entries
286 * exceeds the maximum size of the table.
288 * Fixme: we probably need more complicated algorithm to collect
289 * entries that have not been used for a long time even
290 * if the number of entries doesn't exceed the maximum size
292 * The full expiration check is for this purpose now.
294 static void ip_vs_lblc_check_expire(struct timer_list *t)
296 struct ip_vs_lblc_table *tbl = from_timer(tbl, t, periodic_timer);
297 struct ip_vs_service *svc = tbl->svc;
298 unsigned long now = jiffies;
301 struct ip_vs_lblc_entry *en;
302 struct hlist_node *next;
304 if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
305 /* do full expiration check */
306 ip_vs_lblc_full_check(svc);
311 if (atomic_read(&tbl->entries) <= tbl->max_size) {
316 goal = (atomic_read(&tbl->entries) - tbl->max_size)*4/3;
317 if (goal > tbl->max_size/2)
318 goal = tbl->max_size/2;
320 for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
321 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
323 spin_lock(&svc->sched_lock);
324 hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
325 if (time_before(now, en->lastuse + ENTRY_TIMEOUT))
329 atomic_dec(&tbl->entries);
332 spin_unlock(&svc->sched_lock);
339 mod_timer(&tbl->periodic_timer, jiffies + CHECK_EXPIRE_INTERVAL);
343 static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
346 struct ip_vs_lblc_table *tbl;
349 * Allocate the ip_vs_lblc_table for this service
351 tbl = kmalloc(sizeof(*tbl), GFP_KERNEL);
355 svc->sched_data = tbl;
356 IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) allocated for "
357 "current service\n", sizeof(*tbl));
360 * Initialize the hash buckets
362 for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
363 INIT_HLIST_HEAD(&tbl->bucket[i]);
365 tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
370 atomic_set(&tbl->entries, 0);
373 * Hook periodic timer for garbage collection
375 timer_setup(&tbl->periodic_timer, ip_vs_lblc_check_expire, 0);
376 mod_timer(&tbl->periodic_timer, jiffies + CHECK_EXPIRE_INTERVAL);
382 static void ip_vs_lblc_done_svc(struct ip_vs_service *svc)
384 struct ip_vs_lblc_table *tbl = svc->sched_data;
386 /* remove periodic timer */
387 timer_shutdown_sync(&tbl->periodic_timer);
389 /* got to clean up table entries here */
390 ip_vs_lblc_flush(svc);
392 /* release the table itself */
393 kfree_rcu(tbl, rcu_head);
394 IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) released\n",
399 static inline struct ip_vs_dest *
400 __ip_vs_lblc_schedule(struct ip_vs_service *svc)
402 struct ip_vs_dest *dest, *least;
406 * We use the following formula to estimate the load:
407 * (dest overhead) / dest->weight
409 * Remember -- no floats in kernel mode!!!
410 * The comparison of h1*w2 > h2*w1 is equivalent to that of
412 * if every weight is larger than zero.
414 * The server with weight=0 is quiesced and will not receive any
417 list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
418 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
420 if (atomic_read(&dest->weight) > 0) {
422 loh = ip_vs_dest_conn_overhead(least);
429 * Find the destination with the least load.
432 list_for_each_entry_continue_rcu(dest, &svc->destinations, n_list) {
433 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
436 doh = ip_vs_dest_conn_overhead(dest);
437 if ((__s64)loh * atomic_read(&dest->weight) >
438 (__s64)doh * atomic_read(&least->weight)) {
444 IP_VS_DBG_BUF(6, "LBLC: server %s:%d "
445 "activeconns %d refcnt %d weight %d overhead %d\n",
446 IP_VS_DBG_ADDR(least->af, &least->addr),
448 atomic_read(&least->activeconns),
449 refcount_read(&least->refcnt),
450 atomic_read(&least->weight), loh);
457 * If this destination server is overloaded and there is a less loaded
458 * server, then return true.
461 is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
463 if (atomic_read(&dest->activeconns) > atomic_read(&dest->weight)) {
464 struct ip_vs_dest *d;
466 list_for_each_entry_rcu(d, &svc->destinations, n_list) {
467 if (atomic_read(&d->activeconns)*2
468 < atomic_read(&d->weight)) {
478 * Locality-Based (weighted) Least-Connection scheduling
480 static struct ip_vs_dest *
481 ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
482 struct ip_vs_iphdr *iph)
484 struct ip_vs_lblc_table *tbl = svc->sched_data;
485 struct ip_vs_dest *dest = NULL;
486 struct ip_vs_lblc_entry *en;
488 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
490 /* First look in our cache */
491 en = ip_vs_lblc_get(svc->af, tbl, &iph->daddr);
493 /* We only hold a read lock, but this is atomic */
494 en->lastuse = jiffies;
497 * If the destination is not available, i.e. it's in the trash,
498 * we must ignore it, as it may be removed from under our feet,
499 * if someone drops our reference count. Our caller only makes
500 * sure that destinations, that are not in the trash, are not
501 * moved to the trash, while we are scheduling. But anyone can
502 * free up entries from the trash at any time.
506 if ((dest->flags & IP_VS_DEST_F_AVAILABLE) &&
507 atomic_read(&dest->weight) > 0 && !is_overloaded(dest, svc))
511 /* No cache entry or it is invalid, time to schedule */
512 dest = __ip_vs_lblc_schedule(svc);
514 ip_vs_scheduler_err(svc, "no destination available");
518 /* If we fail to create a cache entry, we'll just use the valid dest */
519 spin_lock_bh(&svc->sched_lock);
521 ip_vs_lblc_new(tbl, &iph->daddr, svc->af, dest);
522 spin_unlock_bh(&svc->sched_lock);
525 IP_VS_DBG_BUF(6, "LBLC: destination IP address %s --> server %s:%d\n",
526 IP_VS_DBG_ADDR(svc->af, &iph->daddr),
527 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
534 * IPVS LBLC Scheduler structure
536 static struct ip_vs_scheduler ip_vs_lblc_scheduler = {
538 .refcnt = ATOMIC_INIT(0),
539 .module = THIS_MODULE,
540 .n_list = LIST_HEAD_INIT(ip_vs_lblc_scheduler.n_list),
541 .init_service = ip_vs_lblc_init_svc,
542 .done_service = ip_vs_lblc_done_svc,
543 .schedule = ip_vs_lblc_schedule,
550 static int __net_init __ip_vs_lblc_init(struct net *net)
552 struct netns_ipvs *ipvs = net_ipvs(net);
557 if (!net_eq(net, &init_net)) {
558 ipvs->lblc_ctl_table = kmemdup(vs_vars_table,
559 sizeof(vs_vars_table),
561 if (ipvs->lblc_ctl_table == NULL)
564 /* Don't export sysctls to unprivileged users */
565 if (net->user_ns != &init_user_ns)
566 ipvs->lblc_ctl_table[0].procname = NULL;
569 ipvs->lblc_ctl_table = vs_vars_table;
570 ipvs->sysctl_lblc_expiration = DEFAULT_EXPIRATION;
571 ipvs->lblc_ctl_table[0].data = &ipvs->sysctl_lblc_expiration;
573 ipvs->lblc_ctl_header =
574 register_net_sysctl(net, "net/ipv4/vs", ipvs->lblc_ctl_table);
575 if (!ipvs->lblc_ctl_header) {
576 if (!net_eq(net, &init_net))
577 kfree(ipvs->lblc_ctl_table);
584 static void __net_exit __ip_vs_lblc_exit(struct net *net)
586 struct netns_ipvs *ipvs = net_ipvs(net);
588 unregister_net_sysctl_table(ipvs->lblc_ctl_header);
590 if (!net_eq(net, &init_net))
591 kfree(ipvs->lblc_ctl_table);
596 static int __net_init __ip_vs_lblc_init(struct net *net) { return 0; }
597 static void __net_exit __ip_vs_lblc_exit(struct net *net) { }
601 static struct pernet_operations ip_vs_lblc_ops = {
602 .init = __ip_vs_lblc_init,
603 .exit = __ip_vs_lblc_exit,
606 static int __init ip_vs_lblc_init(void)
610 ret = register_pernet_subsys(&ip_vs_lblc_ops);
614 ret = register_ip_vs_scheduler(&ip_vs_lblc_scheduler);
616 unregister_pernet_subsys(&ip_vs_lblc_ops);
620 static void __exit ip_vs_lblc_cleanup(void)
622 unregister_ip_vs_scheduler(&ip_vs_lblc_scheduler);
623 unregister_pernet_subsys(&ip_vs_lblc_ops);
628 module_init(ip_vs_lblc_init);
629 module_exit(ip_vs_lblc_cleanup);
630 MODULE_LICENSE("GPL");