1// SPDX-License-Identifier: GPL-2.0
2/* IPVS: Maglev Hashing scheduling module
3 *
4 * Authors: Inju Song <inju.song@navercorp.com>
5 *
6 */
7
8/* The mh algorithm is to assign a preference list of all the lookup
9 * table positions to each destination and populate the table with
10 * the most-preferred position of destinations. Then it is to select
11 * destination with the hash key of source IP address through looking
12 * up a the lookup table.
13 *
14 * The algorithm is detailed in:
15 * [3.4 Consistent Hasing]
16https://www.usenix.org/system/files/conference/nsdi16/nsdi16-paper-eisenbud.pdf
17 *
18 */
19
20#define KMSG_COMPONENT "IPVS"
21#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
22
23#include <linux/ip.h>
24#include <linux/slab.h>
25#include <linux/module.h>
26#include <linux/kernel.h>
27#include <linux/skbuff.h>
28
29#include <net/ip_vs.h>
30
31#include <linux/siphash.h>
32#include <linux/bitops.h>
33#include <linux/gcd.h>
34
35#define IP_VS_SVC_F_SCHED_MH_FALLBACK IP_VS_SVC_F_SCHED1 /* MH fallback */
36#define IP_VS_SVC_F_SCHED_MH_PORT IP_VS_SVC_F_SCHED2 /* MH use port */
37
38struct ip_vs_mh_lookup {
39 struct ip_vs_dest __rcu *dest; /* real server (cache) */
40};
41
42struct ip_vs_mh_dest_setup {
43 unsigned int offset; /* starting offset */
44 unsigned int skip; /* skip */
45 unsigned int perm; /* next_offset */
46 int turns; /* weight / gcd() and rshift */
47};
48
49/* Available prime numbers for MH table */
50static int primes[] = {251, 509, 1021, 2039, 4093,
51 8191, 16381, 32749, 65521, 131071};
52
53/* For IPVS MH entry hash table */
54#ifndef CONFIG_IP_VS_MH_TAB_INDEX
55#define CONFIG_IP_VS_MH_TAB_INDEX 12
56#endif
57#define IP_VS_MH_TAB_BITS (CONFIG_IP_VS_MH_TAB_INDEX / 2)
58#define IP_VS_MH_TAB_INDEX (CONFIG_IP_VS_MH_TAB_INDEX - 8)
59#define IP_VS_MH_TAB_SIZE primes[IP_VS_MH_TAB_INDEX]
60
61struct ip_vs_mh_state {
62 struct rcu_head rcu_head;
63 struct ip_vs_mh_lookup *lookup;
64 struct ip_vs_mh_dest_setup *dest_setup;
65 hsiphash_key_t hash1, hash2;
66 int gcd;
67 int rshift;
68};
69
70static inline void generate_hash_secret(hsiphash_key_t *hash1,
71 hsiphash_key_t *hash2)
72{
73 hash1->key[0] = 2654435761UL;
74 hash1->key[1] = 2654435761UL;
75
76 hash2->key[0] = 2654446892UL;
77 hash2->key[1] = 2654446892UL;
78}
79
80/* Helper function to determine if server is unavailable */
81static inline bool is_unavailable(struct ip_vs_dest *dest)
82{
83 return atomic_read(v: &dest->weight) <= 0 ||
84 dest->flags & IP_VS_DEST_F_OVERLOAD;
85}
86
87/* Returns hash value for IPVS MH entry */
88static inline unsigned int
89ip_vs_mh_hashkey(int af, const union nf_inet_addr *addr,
90 __be16 port, hsiphash_key_t *key, unsigned int offset)
91{
92 unsigned int v;
93 __be32 addr_fold = addr->ip;
94
95#ifdef CONFIG_IP_VS_IPV6
96 if (af == AF_INET6)
97 addr_fold = addr->ip6[0] ^ addr->ip6[1] ^
98 addr->ip6[2] ^ addr->ip6[3];
99#endif
100 v = (offset + ntohs(port) + ntohl(addr_fold));
101 return hsiphash(data: &v, len: sizeof(v), key);
102}
103
104/* Reset all the hash buckets of the specified table. */
105static void ip_vs_mh_reset(struct ip_vs_mh_state *s)
106{
107 int i;
108 struct ip_vs_mh_lookup *l;
109 struct ip_vs_dest *dest;
110
111 l = &s->lookup[0];
112 for (i = 0; i < IP_VS_MH_TAB_SIZE; i++) {
113 dest = rcu_dereference_protected(l->dest, 1);
114 if (dest) {
115 ip_vs_dest_put(dest);
116 RCU_INIT_POINTER(l->dest, NULL);
117 }
118 l++;
119 }
120}
121
122static int ip_vs_mh_permutate(struct ip_vs_mh_state *s,
123 struct ip_vs_service *svc)
124{
125 struct list_head *p;
126 struct ip_vs_mh_dest_setup *ds;
127 struct ip_vs_dest *dest;
128 int lw;
129
130 /* If gcd is smaller then 1, number of dests or
131 * all last_weight of dests are zero. So, skip
132 * permutation for the dests.
133 */
134 if (s->gcd < 1)
135 return 0;
136
137 /* Set dest_setup for the dests permutation */
138 p = &svc->destinations;
139 ds = &s->dest_setup[0];
140 while ((p = p->next) != &svc->destinations) {
141 dest = list_entry(p, struct ip_vs_dest, n_list);
142
143 ds->offset = ip_vs_mh_hashkey(af: svc->af, addr: &dest->addr,
144 port: dest->port, key: &s->hash1, offset: 0) %
145 IP_VS_MH_TAB_SIZE;
146 ds->skip = ip_vs_mh_hashkey(af: svc->af, addr: &dest->addr,
147 port: dest->port, key: &s->hash2, offset: 0) %
148 (IP_VS_MH_TAB_SIZE - 1) + 1;
149 ds->perm = ds->offset;
150
151 lw = atomic_read(v: &dest->last_weight);
152 ds->turns = ((lw / s->gcd) >> s->rshift) ? : (lw != 0);
153 ds++;
154 }
155
156 return 0;
157}
158
159static int ip_vs_mh_populate(struct ip_vs_mh_state *s,
160 struct ip_vs_service *svc)
161{
162 int n, c, dt_count;
163 unsigned long *table;
164 struct list_head *p;
165 struct ip_vs_mh_dest_setup *ds;
166 struct ip_vs_dest *dest, *new_dest;
167
168 /* If gcd is smaller then 1, number of dests or
169 * all last_weight of dests are zero. So, skip
170 * the population for the dests and reset lookup table.
171 */
172 if (s->gcd < 1) {
173 ip_vs_mh_reset(s);
174 return 0;
175 }
176
177 table = bitmap_zalloc(IP_VS_MH_TAB_SIZE, GFP_KERNEL);
178 if (!table)
179 return -ENOMEM;
180
181 p = &svc->destinations;
182 n = 0;
183 dt_count = 0;
184 while (n < IP_VS_MH_TAB_SIZE) {
185 if (p == &svc->destinations)
186 p = p->next;
187
188 ds = &s->dest_setup[0];
189 while (p != &svc->destinations) {
190 /* Ignore added server with zero weight */
191 if (ds->turns < 1) {
192 p = p->next;
193 ds++;
194 continue;
195 }
196
197 c = ds->perm;
198 while (test_bit(c, table)) {
199 /* Add skip, mod IP_VS_MH_TAB_SIZE */
200 ds->perm += ds->skip;
201 if (ds->perm >= IP_VS_MH_TAB_SIZE)
202 ds->perm -= IP_VS_MH_TAB_SIZE;
203 c = ds->perm;
204 }
205
206 __set_bit(c, table);
207
208 dest = rcu_dereference_protected(s->lookup[c].dest, 1);
209 new_dest = list_entry(p, struct ip_vs_dest, n_list);
210 if (dest != new_dest) {
211 if (dest)
212 ip_vs_dest_put(dest);
213 ip_vs_dest_hold(dest: new_dest);
214 RCU_INIT_POINTER(s->lookup[c].dest, new_dest);
215 }
216
217 if (++n == IP_VS_MH_TAB_SIZE)
218 goto out;
219
220 if (++dt_count >= ds->turns) {
221 dt_count = 0;
222 p = p->next;
223 ds++;
224 }
225 }
226 }
227
228out:
229 bitmap_free(bitmap: table);
230 return 0;
231}
232
233/* Get ip_vs_dest associated with supplied parameters. */
234static inline struct ip_vs_dest *
235ip_vs_mh_get(struct ip_vs_service *svc, struct ip_vs_mh_state *s,
236 const union nf_inet_addr *addr, __be16 port)
237{
238 unsigned int hash = ip_vs_mh_hashkey(af: svc->af, addr, port, key: &s->hash1, offset: 0)
239 % IP_VS_MH_TAB_SIZE;
240 struct ip_vs_dest *dest = rcu_dereference(s->lookup[hash].dest);
241
242 return (!dest || is_unavailable(dest)) ? NULL : dest;
243}
244
245/* As ip_vs_mh_get, but with fallback if selected server is unavailable */
246static inline struct ip_vs_dest *
247ip_vs_mh_get_fallback(struct ip_vs_service *svc, struct ip_vs_mh_state *s,
248 const union nf_inet_addr *addr, __be16 port)
249{
250 unsigned int offset, roffset;
251 unsigned int hash, ihash;
252 struct ip_vs_dest *dest;
253
254 /* First try the dest it's supposed to go to */
255 ihash = ip_vs_mh_hashkey(af: svc->af, addr, port,
256 key: &s->hash1, offset: 0) % IP_VS_MH_TAB_SIZE;
257 dest = rcu_dereference(s->lookup[ihash].dest);
258 if (!dest)
259 return NULL;
260 if (!is_unavailable(dest))
261 return dest;
262
263 IP_VS_DBG_BUF(6, "MH: selected unavailable server %s:%u, reselecting",
264 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
265
266 /* If the original dest is unavailable, loop around the table
267 * starting from ihash to find a new dest
268 */
269 for (offset = 0; offset < IP_VS_MH_TAB_SIZE; offset++) {
270 roffset = (offset + ihash) % IP_VS_MH_TAB_SIZE;
271 hash = ip_vs_mh_hashkey(af: svc->af, addr, port, key: &s->hash1,
272 offset: roffset) % IP_VS_MH_TAB_SIZE;
273 dest = rcu_dereference(s->lookup[hash].dest);
274 if (!dest)
275 break;
276 if (!is_unavailable(dest))
277 return dest;
278 IP_VS_DBG_BUF(6,
279 "MH: selected unavailable server %s:%u (offset %u), reselecting",
280 IP_VS_DBG_ADDR(dest->af, &dest->addr),
281 ntohs(dest->port), roffset);
282 }
283
284 return NULL;
285}
286
287/* Assign all the hash buckets of the specified table with the service. */
288static int ip_vs_mh_reassign(struct ip_vs_mh_state *s,
289 struct ip_vs_service *svc)
290{
291 int ret;
292
293 if (svc->num_dests > IP_VS_MH_TAB_SIZE)
294 return -EINVAL;
295
296 if (svc->num_dests >= 1) {
297 s->dest_setup = kcalloc(n: svc->num_dests,
298 size: sizeof(struct ip_vs_mh_dest_setup),
299 GFP_KERNEL);
300 if (!s->dest_setup)
301 return -ENOMEM;
302 }
303
304 ip_vs_mh_permutate(s, svc);
305
306 ret = ip_vs_mh_populate(s, svc);
307 if (ret < 0)
308 goto out;
309
310 IP_VS_DBG_BUF(6, "MH: reassign lookup table of %s:%u\n",
311 IP_VS_DBG_ADDR(svc->af, &svc->addr),
312 ntohs(svc->port));
313
314out:
315 if (svc->num_dests >= 1) {
316 kfree(objp: s->dest_setup);
317 s->dest_setup = NULL;
318 }
319 return ret;
320}
321
322static int ip_vs_mh_gcd_weight(struct ip_vs_service *svc)
323{
324 struct ip_vs_dest *dest;
325 int weight;
326 int g = 0;
327
328 list_for_each_entry(dest, &svc->destinations, n_list) {
329 weight = atomic_read(v: &dest->last_weight);
330 if (weight > 0) {
331 if (g > 0)
332 g = gcd(a: weight, b: g);
333 else
334 g = weight;
335 }
336 }
337 return g;
338}
339
340/* To avoid assigning huge weight for the MH table,
341 * calculate shift value with gcd.
342 */
343static int ip_vs_mh_shift_weight(struct ip_vs_service *svc, int gcd)
344{
345 struct ip_vs_dest *dest;
346 int new_weight, weight = 0;
347 int mw, shift;
348
349 /* If gcd is smaller then 1, number of dests or
350 * all last_weight of dests are zero. So, return
351 * shift value as zero.
352 */
353 if (gcd < 1)
354 return 0;
355
356 list_for_each_entry(dest, &svc->destinations, n_list) {
357 new_weight = atomic_read(v: &dest->last_weight);
358 if (new_weight > weight)
359 weight = new_weight;
360 }
361
362 /* Because gcd is greater than zero,
363 * the maximum weight and gcd are always greater than zero
364 */
365 mw = weight / gcd;
366
367 /* shift = occupied bits of weight/gcd - MH highest bits */
368 shift = fls(x: mw) - IP_VS_MH_TAB_BITS;
369 return (shift >= 0) ? shift : 0;
370}
371
372static void ip_vs_mh_state_free(struct rcu_head *head)
373{
374 struct ip_vs_mh_state *s;
375
376 s = container_of(head, struct ip_vs_mh_state, rcu_head);
377 kfree(objp: s->lookup);
378 kfree(objp: s);
379}
380
381static int ip_vs_mh_init_svc(struct ip_vs_service *svc)
382{
383 int ret;
384 struct ip_vs_mh_state *s;
385
386 /* Allocate the MH table for this service */
387 s = kzalloc(size: sizeof(*s), GFP_KERNEL);
388 if (!s)
389 return -ENOMEM;
390
391 s->lookup = kcalloc(IP_VS_MH_TAB_SIZE, size: sizeof(struct ip_vs_mh_lookup),
392 GFP_KERNEL);
393 if (!s->lookup) {
394 kfree(objp: s);
395 return -ENOMEM;
396 }
397
398 generate_hash_secret(hash1: &s->hash1, hash2: &s->hash2);
399 s->gcd = ip_vs_mh_gcd_weight(svc);
400 s->rshift = ip_vs_mh_shift_weight(svc, gcd: s->gcd);
401
402 IP_VS_DBG(6,
403 "MH lookup table (memory=%zdbytes) allocated for current service\n",
404 sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE);
405
406 /* Assign the lookup table with current dests */
407 ret = ip_vs_mh_reassign(s, svc);
408 if (ret < 0) {
409 ip_vs_mh_reset(s);
410 ip_vs_mh_state_free(head: &s->rcu_head);
411 return ret;
412 }
413
414 /* No more failures, attach state */
415 svc->sched_data = s;
416 return 0;
417}
418
419static void ip_vs_mh_done_svc(struct ip_vs_service *svc)
420{
421 struct ip_vs_mh_state *s = svc->sched_data;
422
423 /* Got to clean up lookup entry here */
424 ip_vs_mh_reset(s);
425
426 call_rcu(head: &s->rcu_head, func: ip_vs_mh_state_free);
427 IP_VS_DBG(6, "MH lookup table (memory=%zdbytes) released\n",
428 sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE);
429}
430
431static int ip_vs_mh_dest_changed(struct ip_vs_service *svc,
432 struct ip_vs_dest *dest)
433{
434 struct ip_vs_mh_state *s = svc->sched_data;
435
436 s->gcd = ip_vs_mh_gcd_weight(svc);
437 s->rshift = ip_vs_mh_shift_weight(svc, gcd: s->gcd);
438
439 /* Assign the lookup table with the updated service */
440 return ip_vs_mh_reassign(s, svc);
441}
442
443/* Helper function to get port number */
444static inline __be16
445ip_vs_mh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
446{
447 __be16 _ports[2], *ports;
448
449 /* At this point we know that we have a valid packet of some kind.
450 * Because ICMP packets are only guaranteed to have the first 8
451 * bytes, let's just grab the ports. Fortunately they're in the
452 * same position for all three of the protocols we care about.
453 */
454 switch (iph->protocol) {
455 case IPPROTO_TCP:
456 case IPPROTO_UDP:
457 case IPPROTO_SCTP:
458 ports = skb_header_pointer(skb, offset: iph->len, len: sizeof(_ports),
459 buffer: &_ports);
460 if (unlikely(!ports))
461 return 0;
462
463 if (likely(!ip_vs_iph_inverse(iph)))
464 return ports[0];
465 else
466 return ports[1];
467 default:
468 return 0;
469 }
470}
471
472/* Maglev Hashing scheduling */
473static struct ip_vs_dest *
474ip_vs_mh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
475 struct ip_vs_iphdr *iph)
476{
477 struct ip_vs_dest *dest;
478 struct ip_vs_mh_state *s;
479 __be16 port = 0;
480 const union nf_inet_addr *hash_addr;
481
482 hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
483
484 IP_VS_DBG(6, "%s : Scheduling...\n", __func__);
485
486 if (svc->flags & IP_VS_SVC_F_SCHED_MH_PORT)
487 port = ip_vs_mh_get_port(skb, iph);
488
489 s = (struct ip_vs_mh_state *)svc->sched_data;
490
491 if (svc->flags & IP_VS_SVC_F_SCHED_MH_FALLBACK)
492 dest = ip_vs_mh_get_fallback(svc, s, addr: hash_addr, port);
493 else
494 dest = ip_vs_mh_get(svc, s, addr: hash_addr, port);
495
496 if (!dest) {
497 ip_vs_scheduler_err(svc, msg: "no destination available");
498 return NULL;
499 }
500
501 IP_VS_DBG_BUF(6, "MH: source IP address %s:%u --> server %s:%u\n",
502 IP_VS_DBG_ADDR(svc->af, hash_addr),
503 ntohs(port),
504 IP_VS_DBG_ADDR(dest->af, &dest->addr),
505 ntohs(dest->port));
506
507 return dest;
508}
509
510/* IPVS MH Scheduler structure */
511static struct ip_vs_scheduler ip_vs_mh_scheduler = {
512 .name = "mh",
513 .refcnt = ATOMIC_INIT(0),
514 .module = THIS_MODULE,
515 .n_list = LIST_HEAD_INIT(ip_vs_mh_scheduler.n_list),
516 .init_service = ip_vs_mh_init_svc,
517 .done_service = ip_vs_mh_done_svc,
518 .add_dest = ip_vs_mh_dest_changed,
519 .del_dest = ip_vs_mh_dest_changed,
520 .upd_dest = ip_vs_mh_dest_changed,
521 .schedule = ip_vs_mh_schedule,
522};
523
524static int __init ip_vs_mh_init(void)
525{
526 return register_ip_vs_scheduler(scheduler: &ip_vs_mh_scheduler);
527}
528
529static void __exit ip_vs_mh_cleanup(void)
530{
531 unregister_ip_vs_scheduler(scheduler: &ip_vs_mh_scheduler);
532 rcu_barrier();
533}
534
535module_init(ip_vs_mh_init);
536module_exit(ip_vs_mh_cleanup);
537MODULE_DESCRIPTION("Maglev hashing ipvs scheduler");
538MODULE_LICENSE("GPL v2");
539MODULE_AUTHOR("Inju Song <inju.song@navercorp.com>");
540

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