1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPVS: Locality-Based Least-Connection scheduling module
4 *
5 * Authors: Wensong Zhang <wensong@gnuchina.org>
6 *
7 * Changes:
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
17 */
18
19/*
20 * The lblc algorithm is as follows (pseudo code):
21 *
22 * if cachenode[dest_ip] is null then
23 * n, cachenode[dest_ip] <- {weighted least-conn node};
24 * else
25 * n <- cachenode[dest_ip];
26 * if (n is dead) OR
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};
30 *
31 * return n;
32 *
33 * Thanks must go to Wenzhuo Zhang for talking WCCP to me and pushing
34 * me to write this module.
35 */
36
37#define KMSG_COMPONENT "IPVS"
38#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
39
40#include <linux/ip.h>
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>
47
48/* for sysctl */
49#include <linux/fs.h>
50#include <linux/sysctl.h>
51
52#include <net/ip_vs.h>
53
54
55/*
56 * It is for garbage collection of stale IPVS lblc entries,
57 * when the table is full.
58 */
59#define CHECK_EXPIRE_INTERVAL (60*HZ)
60#define ENTRY_TIMEOUT (6*60*HZ)
61
62#define DEFAULT_EXPIRATION (24*60*60*HZ)
63
64/*
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.
69 */
70#define COUNT_FOR_FULL_EXPIRATION 30
71
72
73/*
74 * for IPVS lblc entry hash table
75 */
76#ifndef CONFIG_IP_VS_LBLC_TAB_BITS
77#define CONFIG_IP_VS_LBLC_TAB_BITS 10
78#endif
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)
82
83
84/*
85 * IPVS lblc entry represents an association between destination
86 * IP address and its destination server
87 */
88struct 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;
95};
96
97
98/*
99 * IPVS lblc hash table
100 */
101struct 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 */
110 bool dead;
111};
112
113
114/*
115 * IPVS LBLC sysctl table
116 */
117#ifdef CONFIG_SYSCTL
118static struct ctl_table vs_vars_table[] = {
119 {
120 .procname = "lblc_expiration",
121 .data = NULL,
122 .maxlen = sizeof(int),
123 .mode = 0644,
124 .proc_handler = proc_dointvec_jiffies,
125 },
126 { }
127};
128#endif
129
130static void ip_vs_lblc_rcu_free(struct rcu_head *head)
131{
132 struct ip_vs_lblc_entry *en = container_of(head,
133 struct ip_vs_lblc_entry,
134 rcu_head);
135
136 ip_vs_dest_put_and_free(dest: en->dest);
137 kfree(objp: en);
138}
139
140static inline void ip_vs_lblc_del(struct ip_vs_lblc_entry *en)
141{
142 hlist_del_rcu(n: &en->list);
143 call_rcu(head: &en->rcu_head, func: ip_vs_lblc_rcu_free);
144}
145
146/*
147 * Returns hash value for IPVS LBLC entry
148 */
149static inline unsigned int
150ip_vs_lblc_hashkey(int af, const union nf_inet_addr *addr)
151{
152 __be32 addr_fold = addr->ip;
153
154#ifdef CONFIG_IP_VS_IPV6
155 if (af == AF_INET6)
156 addr_fold = addr->ip6[0]^addr->ip6[1]^
157 addr->ip6[2]^addr->ip6[3];
158#endif
159 return hash_32(ntohl(addr_fold), IP_VS_LBLC_TAB_BITS);
160}
161
162
163/*
164 * Hash an entry in the ip_vs_lblc_table.
165 * returns bool success.
166 */
167static void
168ip_vs_lblc_hash(struct ip_vs_lblc_table *tbl, struct ip_vs_lblc_entry *en)
169{
170 unsigned int hash = ip_vs_lblc_hashkey(af: en->af, addr: &en->addr);
171
172 hlist_add_head_rcu(n: &en->list, h: &tbl->bucket[hash]);
173 atomic_inc(v: &tbl->entries);
174}
175
176
177/* Get ip_vs_lblc_entry associated with supplied parameters. */
178static inline struct ip_vs_lblc_entry *
179ip_vs_lblc_get(int af, struct ip_vs_lblc_table *tbl,
180 const union nf_inet_addr *addr)
181{
182 unsigned int hash = ip_vs_lblc_hashkey(af, addr);
183 struct ip_vs_lblc_entry *en;
184
185 hlist_for_each_entry_rcu(en, &tbl->bucket[hash], list)
186 if (ip_vs_addr_equal(af, a: &en->addr, b: addr))
187 return en;
188
189 return NULL;
190}
191
192
193/*
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.
196 */
197static inline struct ip_vs_lblc_entry *
198ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
199 u16 af, struct ip_vs_dest *dest)
200{
201 struct ip_vs_lblc_entry *en;
202
203 en = ip_vs_lblc_get(af, tbl, addr: daddr);
204 if (en) {
205 if (en->dest == dest)
206 return en;
207 ip_vs_lblc_del(en);
208 }
209 en = kmalloc(size: sizeof(*en), GFP_ATOMIC);
210 if (!en)
211 return NULL;
212
213 en->af = af;
214 ip_vs_addr_copy(af, dst: &en->addr, src: daddr);
215 en->lastuse = jiffies;
216
217 ip_vs_dest_hold(dest);
218 en->dest = dest;
219
220 ip_vs_lblc_hash(tbl, en);
221
222 return en;
223}
224
225
226/*
227 * Flush all the entries of the specified table.
228 */
229static void ip_vs_lblc_flush(struct ip_vs_service *svc)
230{
231 struct ip_vs_lblc_table *tbl = svc->sched_data;
232 struct ip_vs_lblc_entry *en;
233 struct hlist_node *next;
234 int i;
235
236 spin_lock_bh(lock: &svc->sched_lock);
237 tbl->dead = true;
238 for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
239 hlist_for_each_entry_safe(en, next, &tbl->bucket[i], list) {
240 ip_vs_lblc_del(en);
241 atomic_dec(v: &tbl->entries);
242 }
243 }
244 spin_unlock_bh(lock: &svc->sched_lock);
245}
246
247static int sysctl_lblc_expiration(struct ip_vs_service *svc)
248{
249#ifdef CONFIG_SYSCTL
250 return svc->ipvs->sysctl_lblc_expiration;
251#else
252 return DEFAULT_EXPIRATION;
253#endif
254}
255
256static inline void ip_vs_lblc_full_check(struct ip_vs_service *svc)
257{
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;
262 int i, j;
263
264 for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
265 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
266
267 spin_lock(lock: &svc->sched_lock);
268 hlist_for_each_entry_safe(en, next, &tbl->bucket[j], list) {
269 if (time_before(now,
270 en->lastuse +
271 sysctl_lblc_expiration(svc)))
272 continue;
273
274 ip_vs_lblc_del(en);
275 atomic_dec(v: &tbl->entries);
276 }
277 spin_unlock(lock: &svc->sched_lock);
278 }
279 tbl->rover = j;
280}
281
282
283/*
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.
287 *
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
291 * of the table.
292 * The full expiration check is for this purpose now.
293 */
294static void ip_vs_lblc_check_expire(struct timer_list *t)
295{
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;
299 int goal;
300 int i, j;
301 struct ip_vs_lblc_entry *en;
302 struct hlist_node *next;
303
304 if ((tbl->counter % COUNT_FOR_FULL_EXPIRATION) == 0) {
305 /* do full expiration check */
306 ip_vs_lblc_full_check(svc);
307 tbl->counter = 1;
308 goto out;
309 }
310
311 if (atomic_read(v: &tbl->entries) <= tbl->max_size) {
312 tbl->counter++;
313 goto out;
314 }
315
316 goal = (atomic_read(v: &tbl->entries) - tbl->max_size)*4/3;
317 if (goal > tbl->max_size/2)
318 goal = tbl->max_size/2;
319
320 for (i = 0, j = tbl->rover; i < IP_VS_LBLC_TAB_SIZE; i++) {
321 j = (j + 1) & IP_VS_LBLC_TAB_MASK;
322
323 spin_lock(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))
326 continue;
327
328 ip_vs_lblc_del(en);
329 atomic_dec(v: &tbl->entries);
330 goal--;
331 }
332 spin_unlock(lock: &svc->sched_lock);
333 if (goal <= 0)
334 break;
335 }
336 tbl->rover = j;
337
338 out:
339 mod_timer(timer: &tbl->periodic_timer, expires: jiffies + CHECK_EXPIRE_INTERVAL);
340}
341
342
343static int ip_vs_lblc_init_svc(struct ip_vs_service *svc)
344{
345 int i;
346 struct ip_vs_lblc_table *tbl;
347
348 /*
349 * Allocate the ip_vs_lblc_table for this service
350 */
351 tbl = kmalloc(size: sizeof(*tbl), GFP_KERNEL);
352 if (tbl == NULL)
353 return -ENOMEM;
354
355 svc->sched_data = tbl;
356 IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) allocated for "
357 "current service\n", sizeof(*tbl));
358
359 /*
360 * Initialize the hash buckets
361 */
362 for (i = 0; i < IP_VS_LBLC_TAB_SIZE; i++) {
363 INIT_HLIST_HEAD(&tbl->bucket[i]);
364 }
365 tbl->max_size = IP_VS_LBLC_TAB_SIZE*16;
366 tbl->rover = 0;
367 tbl->counter = 1;
368 tbl->dead = false;
369 tbl->svc = svc;
370 atomic_set(v: &tbl->entries, i: 0);
371
372 /*
373 * Hook periodic timer for garbage collection
374 */
375 timer_setup(&tbl->periodic_timer, ip_vs_lblc_check_expire, 0);
376 mod_timer(timer: &tbl->periodic_timer, expires: jiffies + CHECK_EXPIRE_INTERVAL);
377
378 return 0;
379}
380
381
382static void ip_vs_lblc_done_svc(struct ip_vs_service *svc)
383{
384 struct ip_vs_lblc_table *tbl = svc->sched_data;
385
386 /* remove periodic timer */
387 timer_shutdown_sync(timer: &tbl->periodic_timer);
388
389 /* got to clean up table entries here */
390 ip_vs_lblc_flush(svc);
391
392 /* release the table itself */
393 kfree_rcu(tbl, rcu_head);
394 IP_VS_DBG(6, "LBLC hash table (memory=%zdbytes) released\n",
395 sizeof(*tbl));
396}
397
398
399static inline struct ip_vs_dest *
400__ip_vs_lblc_schedule(struct ip_vs_service *svc)
401{
402 struct ip_vs_dest *dest, *least;
403 int loh, doh;
404
405 /*
406 * We use the following formula to estimate the load:
407 * (dest overhead) / dest->weight
408 *
409 * Remember -- no floats in kernel mode!!!
410 * The comparison of h1*w2 > h2*w1 is equivalent to that of
411 * h1/w1 > h2/w2
412 * if every weight is larger than zero.
413 *
414 * The server with weight=0 is quiesced and will not receive any
415 * new connection.
416 */
417 list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
418 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
419 continue;
420 if (atomic_read(v: &dest->weight) > 0) {
421 least = dest;
422 loh = ip_vs_dest_conn_overhead(dest: least);
423 goto nextstage;
424 }
425 }
426 return NULL;
427
428 /*
429 * Find the destination with the least load.
430 */
431 nextstage:
432 list_for_each_entry_continue_rcu(dest, &svc->destinations, n_list) {
433 if (dest->flags & IP_VS_DEST_F_OVERLOAD)
434 continue;
435
436 doh = ip_vs_dest_conn_overhead(dest);
437 if ((__s64)loh * atomic_read(v: &dest->weight) >
438 (__s64)doh * atomic_read(v: &least->weight)) {
439 least = dest;
440 loh = doh;
441 }
442 }
443
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),
447 ntohs(least->port),
448 atomic_read(&least->activeconns),
449 refcount_read(&least->refcnt),
450 atomic_read(&least->weight), loh);
451
452 return least;
453}
454
455
456/*
457 * If this destination server is overloaded and there is a less loaded
458 * server, then return true.
459 */
460static inline int
461is_overloaded(struct ip_vs_dest *dest, struct ip_vs_service *svc)
462{
463 if (atomic_read(v: &dest->activeconns) > atomic_read(v: &dest->weight)) {
464 struct ip_vs_dest *d;
465
466 list_for_each_entry_rcu(d, &svc->destinations, n_list) {
467 if (atomic_read(v: &d->activeconns)*2
468 < atomic_read(v: &d->weight)) {
469 return 1;
470 }
471 }
472 }
473 return 0;
474}
475
476
477/*
478 * Locality-Based (weighted) Least-Connection scheduling
479 */
480static struct ip_vs_dest *
481ip_vs_lblc_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
482 struct ip_vs_iphdr *iph)
483{
484 struct ip_vs_lblc_table *tbl = svc->sched_data;
485 struct ip_vs_dest *dest = NULL;
486 struct ip_vs_lblc_entry *en;
487
488 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
489
490 /* First look in our cache */
491 en = ip_vs_lblc_get(af: svc->af, tbl, addr: &iph->daddr);
492 if (en) {
493 /* We only hold a read lock, but this is atomic */
494 en->lastuse = jiffies;
495
496 /*
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.
503 */
504
505 dest = en->dest;
506 if ((dest->flags & IP_VS_DEST_F_AVAILABLE) &&
507 atomic_read(v: &dest->weight) > 0 && !is_overloaded(dest, svc))
508 goto out;
509 }
510
511 /* No cache entry or it is invalid, time to schedule */
512 dest = __ip_vs_lblc_schedule(svc);
513 if (!dest) {
514 ip_vs_scheduler_err(svc, msg: "no destination available");
515 return NULL;
516 }
517
518 /* If we fail to create a cache entry, we'll just use the valid dest */
519 spin_lock_bh(lock: &svc->sched_lock);
520 if (!tbl->dead)
521 ip_vs_lblc_new(tbl, daddr: &iph->daddr, af: svc->af, dest);
522 spin_unlock_bh(lock: &svc->sched_lock);
523
524out:
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));
528
529 return dest;
530}
531
532
533/*
534 * IPVS LBLC Scheduler structure
535 */
536static struct ip_vs_scheduler ip_vs_lblc_scheduler = {
537 .name = "lblc",
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,
544};
545
546/*
547 * per netns init.
548 */
549#ifdef CONFIG_SYSCTL
550static int __net_init __ip_vs_lblc_init(struct net *net)
551{
552 struct netns_ipvs *ipvs = net_ipvs(net);
553 size_t vars_table_size = ARRAY_SIZE(vs_vars_table);
554
555 if (!ipvs)
556 return -ENOENT;
557
558 if (!net_eq(net1: net, net2: &init_net)) {
559 ipvs->lblc_ctl_table = kmemdup(p: vs_vars_table,
560 size: sizeof(vs_vars_table),
561 GFP_KERNEL);
562 if (ipvs->lblc_ctl_table == NULL)
563 return -ENOMEM;
564
565 /* Don't export sysctls to unprivileged users */
566 if (net->user_ns != &init_user_ns) {
567 ipvs->lblc_ctl_table[0].procname = NULL;
568 vars_table_size = 0;
569 }
570
571 } else
572 ipvs->lblc_ctl_table = vs_vars_table;
573 ipvs->sysctl_lblc_expiration = DEFAULT_EXPIRATION;
574 ipvs->lblc_ctl_table[0].data = &ipvs->sysctl_lblc_expiration;
575
576 ipvs->lblc_ctl_header = register_net_sysctl_sz(net, path: "net/ipv4/vs",
577 table: ipvs->lblc_ctl_table,
578 table_size: vars_table_size);
579 if (!ipvs->lblc_ctl_header) {
580 if (!net_eq(net1: net, net2: &init_net))
581 kfree(objp: ipvs->lblc_ctl_table);
582 return -ENOMEM;
583 }
584
585 return 0;
586}
587
588static void __net_exit __ip_vs_lblc_exit(struct net *net)
589{
590 struct netns_ipvs *ipvs = net_ipvs(net);
591
592 unregister_net_sysctl_table(header: ipvs->lblc_ctl_header);
593
594 if (!net_eq(net1: net, net2: &init_net))
595 kfree(objp: ipvs->lblc_ctl_table);
596}
597
598#else
599
600static int __net_init __ip_vs_lblc_init(struct net *net) { return 0; }
601static void __net_exit __ip_vs_lblc_exit(struct net *net) { }
602
603#endif
604
605static struct pernet_operations ip_vs_lblc_ops = {
606 .init = __ip_vs_lblc_init,
607 .exit = __ip_vs_lblc_exit,
608};
609
610static int __init ip_vs_lblc_init(void)
611{
612 int ret;
613
614 ret = register_pernet_subsys(&ip_vs_lblc_ops);
615 if (ret)
616 return ret;
617
618 ret = register_ip_vs_scheduler(scheduler: &ip_vs_lblc_scheduler);
619 if (ret)
620 unregister_pernet_subsys(&ip_vs_lblc_ops);
621 return ret;
622}
623
624static void __exit ip_vs_lblc_cleanup(void)
625{
626 unregister_ip_vs_scheduler(scheduler: &ip_vs_lblc_scheduler);
627 unregister_pernet_subsys(&ip_vs_lblc_ops);
628 rcu_barrier();
629}
630
631
632module_init(ip_vs_lblc_init);
633module_exit(ip_vs_lblc_cleanup);
634MODULE_LICENSE("GPL");
635MODULE_DESCRIPTION("ipvs locality-based least-connection scheduler");
636

source code of linux/net/netfilter/ipvs/ip_vs_lblc.c