1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPVS: Source Hashing scheduling module
4 *
5 * Authors: Wensong Zhang <wensong@gnuchina.org>
6 *
7 * Changes:
8 */
9
10/*
11 * The sh algorithm is to select server by the hash key of source IP
12 * address. The pseudo code is as follows:
13 *
14 * n <- servernode[src_ip];
15 * if (n is dead) OR
16 * (n is overloaded) or (n.weight <= 0) then
17 * return NULL;
18 *
19 * return n;
20 *
21 * Notes that servernode is a 256-bucket hash table that maps the hash
22 * index derived from packet source IP address to the current server
23 * array. If the sh scheduler is used in cache cluster, it is good to
24 * combine it with cache_bypass feature. When the statically assigned
25 * server is dead or overloaded, the load balancer can bypass the cache
26 * server and send requests to the original server directly.
27 *
28 * The weight destination attribute can be used to control the
29 * distribution of connections to the destinations in servernode. The
30 * greater the weight, the more connections the destination
31 * will receive.
32 *
33 */
34
35#define KMSG_COMPONENT "IPVS"
36#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
37
38#include <linux/ip.h>
39#include <linux/slab.h>
40#include <linux/module.h>
41#include <linux/kernel.h>
42#include <linux/skbuff.h>
43
44#include <net/ip_vs.h>
45
46#include <net/tcp.h>
47#include <linux/udp.h>
48#include <linux/sctp.h>
49
50
51/*
52 * IPVS SH bucket
53 */
54struct ip_vs_sh_bucket {
55 struct ip_vs_dest __rcu *dest; /* real server (cache) */
56};
57
58/*
59 * for IPVS SH entry hash table
60 */
61#ifndef CONFIG_IP_VS_SH_TAB_BITS
62#define CONFIG_IP_VS_SH_TAB_BITS 8
63#endif
64#define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS
65#define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS)
66#define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1)
67
68struct ip_vs_sh_state {
69 struct rcu_head rcu_head;
70 struct ip_vs_sh_bucket buckets[IP_VS_SH_TAB_SIZE];
71};
72
73/* Helper function to determine if server is unavailable */
74static inline bool is_unavailable(struct ip_vs_dest *dest)
75{
76 return atomic_read(v: &dest->weight) <= 0 ||
77 dest->flags & IP_VS_DEST_F_OVERLOAD;
78}
79
80/*
81 * Returns hash value for IPVS SH entry
82 */
83static inline unsigned int
84ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr,
85 __be16 port, unsigned int offset)
86{
87 __be32 addr_fold = addr->ip;
88
89#ifdef CONFIG_IP_VS_IPV6
90 if (af == AF_INET6)
91 addr_fold = addr->ip6[0]^addr->ip6[1]^
92 addr->ip6[2]^addr->ip6[3];
93#endif
94 return (offset + hash_32(ntohs(port) + ntohl(addr_fold),
95 IP_VS_SH_TAB_BITS)) &
96 IP_VS_SH_TAB_MASK;
97}
98
99
100/*
101 * Get ip_vs_dest associated with supplied parameters.
102 */
103static inline struct ip_vs_dest *
104ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
105 const union nf_inet_addr *addr, __be16 port)
106{
107 unsigned int hash = ip_vs_sh_hashkey(af: svc->af, addr, port, offset: 0);
108 struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest);
109
110 return (!dest || is_unavailable(dest)) ? NULL : dest;
111}
112
113
114/* As ip_vs_sh_get, but with fallback if selected server is unavailable
115 *
116 * The fallback strategy loops around the table starting from a "random"
117 * point (in fact, it is chosen to be the original hash value to make the
118 * algorithm deterministic) to find a new server.
119 */
120static inline struct ip_vs_dest *
121ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
122 const union nf_inet_addr *addr, __be16 port)
123{
124 unsigned int offset, roffset;
125 unsigned int hash, ihash;
126 struct ip_vs_dest *dest;
127
128 /* first try the dest it's supposed to go to */
129 ihash = ip_vs_sh_hashkey(af: svc->af, addr, port, offset: 0);
130 dest = rcu_dereference(s->buckets[ihash].dest);
131 if (!dest)
132 return NULL;
133 if (!is_unavailable(dest))
134 return dest;
135
136 IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
137 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
138
139 /* if the original dest is unavailable, loop around the table
140 * starting from ihash to find a new dest
141 */
142 for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
143 roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
144 hash = ip_vs_sh_hashkey(af: svc->af, addr, port, offset: roffset);
145 dest = rcu_dereference(s->buckets[hash].dest);
146 if (!dest)
147 break;
148 if (!is_unavailable(dest))
149 return dest;
150 IP_VS_DBG_BUF(6, "SH: selected unavailable "
151 "server %s:%d (offset %d), reselecting",
152 IP_VS_DBG_ADDR(dest->af, &dest->addr),
153 ntohs(dest->port), roffset);
154 }
155
156 return NULL;
157}
158
159/*
160 * Assign all the hash buckets of the specified table with the service.
161 */
162static int
163ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc)
164{
165 int i;
166 struct ip_vs_sh_bucket *b;
167 struct list_head *p;
168 struct ip_vs_dest *dest;
169 int d_count;
170 bool empty;
171
172 b = &s->buckets[0];
173 p = &svc->destinations;
174 empty = list_empty(head: p);
175 d_count = 0;
176 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
177 dest = rcu_dereference_protected(b->dest, 1);
178 if (dest)
179 ip_vs_dest_put(dest);
180 if (empty)
181 RCU_INIT_POINTER(b->dest, NULL);
182 else {
183 if (p == &svc->destinations)
184 p = p->next;
185
186 dest = list_entry(p, struct ip_vs_dest, n_list);
187 ip_vs_dest_hold(dest);
188 RCU_INIT_POINTER(b->dest, dest);
189
190 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n",
191 i, IP_VS_DBG_ADDR(dest->af, &dest->addr),
192 atomic_read(&dest->weight));
193
194 /* Don't move to next dest until filling weight */
195 if (++d_count >= atomic_read(v: &dest->weight)) {
196 p = p->next;
197 d_count = 0;
198 }
199
200 }
201 b++;
202 }
203 return 0;
204}
205
206
207/*
208 * Flush all the hash buckets of the specified table.
209 */
210static void ip_vs_sh_flush(struct ip_vs_sh_state *s)
211{
212 int i;
213 struct ip_vs_sh_bucket *b;
214 struct ip_vs_dest *dest;
215
216 b = &s->buckets[0];
217 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
218 dest = rcu_dereference_protected(b->dest, 1);
219 if (dest) {
220 ip_vs_dest_put(dest);
221 RCU_INIT_POINTER(b->dest, NULL);
222 }
223 b++;
224 }
225}
226
227
228static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
229{
230 struct ip_vs_sh_state *s;
231
232 /* allocate the SH table for this service */
233 s = kzalloc(size: sizeof(struct ip_vs_sh_state), GFP_KERNEL);
234 if (s == NULL)
235 return -ENOMEM;
236
237 svc->sched_data = s;
238 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) allocated for "
239 "current service\n",
240 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
241
242 /* assign the hash buckets with current dests */
243 ip_vs_sh_reassign(s, svc);
244
245 return 0;
246}
247
248
249static void ip_vs_sh_done_svc(struct ip_vs_service *svc)
250{
251 struct ip_vs_sh_state *s = svc->sched_data;
252
253 /* got to clean up hash buckets here */
254 ip_vs_sh_flush(s);
255
256 /* release the table itself */
257 kfree_rcu(s, rcu_head);
258 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) released\n",
259 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
260}
261
262
263static int ip_vs_sh_dest_changed(struct ip_vs_service *svc,
264 struct ip_vs_dest *dest)
265{
266 struct ip_vs_sh_state *s = svc->sched_data;
267
268 /* assign the hash buckets with the updated service */
269 ip_vs_sh_reassign(s, svc);
270
271 return 0;
272}
273
274
275/* Helper function to get port number */
276static inline __be16
277ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
278{
279 __be16 _ports[2], *ports;
280
281 /* At this point we know that we have a valid packet of some kind.
282 * Because ICMP packets are only guaranteed to have the first 8
283 * bytes, let's just grab the ports. Fortunately they're in the
284 * same position for all three of the protocols we care about.
285 */
286 switch (iph->protocol) {
287 case IPPROTO_TCP:
288 case IPPROTO_UDP:
289 case IPPROTO_SCTP:
290 ports = skb_header_pointer(skb, offset: iph->len, len: sizeof(_ports),
291 buffer: &_ports);
292 if (unlikely(!ports))
293 return 0;
294
295 if (likely(!ip_vs_iph_inverse(iph)))
296 return ports[0];
297 else
298 return ports[1];
299 default:
300 return 0;
301 }
302}
303
304
305/*
306 * Source Hashing scheduling
307 */
308static struct ip_vs_dest *
309ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
310 struct ip_vs_iphdr *iph)
311{
312 struct ip_vs_dest *dest;
313 struct ip_vs_sh_state *s;
314 __be16 port = 0;
315 const union nf_inet_addr *hash_addr;
316
317 hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
318
319 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
320
321 if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT)
322 port = ip_vs_sh_get_port(skb, iph);
323
324 s = (struct ip_vs_sh_state *) svc->sched_data;
325
326 if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK)
327 dest = ip_vs_sh_get_fallback(svc, s, addr: hash_addr, port);
328 else
329 dest = ip_vs_sh_get(svc, s, addr: hash_addr, port);
330
331 if (!dest) {
332 ip_vs_scheduler_err(svc, msg: "no destination available");
333 return NULL;
334 }
335
336 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
337 IP_VS_DBG_ADDR(svc->af, hash_addr),
338 IP_VS_DBG_ADDR(dest->af, &dest->addr),
339 ntohs(dest->port));
340
341 return dest;
342}
343
344
345/*
346 * IPVS SH Scheduler structure
347 */
348static struct ip_vs_scheduler ip_vs_sh_scheduler =
349{
350 .name = "sh",
351 .refcnt = ATOMIC_INIT(0),
352 .module = THIS_MODULE,
353 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list),
354 .init_service = ip_vs_sh_init_svc,
355 .done_service = ip_vs_sh_done_svc,
356 .add_dest = ip_vs_sh_dest_changed,
357 .del_dest = ip_vs_sh_dest_changed,
358 .upd_dest = ip_vs_sh_dest_changed,
359 .schedule = ip_vs_sh_schedule,
360};
361
362
363static int __init ip_vs_sh_init(void)
364{
365 return register_ip_vs_scheduler(scheduler: &ip_vs_sh_scheduler);
366}
367
368
369static void __exit ip_vs_sh_cleanup(void)
370{
371 unregister_ip_vs_scheduler(scheduler: &ip_vs_sh_scheduler);
372 synchronize_rcu();
373}
374
375
376module_init(ip_vs_sh_init);
377module_exit(ip_vs_sh_cleanup);
378MODULE_LICENSE("GPL");
379MODULE_DESCRIPTION("ipvs source hashing scheduler");
380

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