blob: 338668f88fe286a9b9c3cfaa05e32c7c334b01ea [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * IPVS: Source Hashing scheduling module
3 *
4 * Version: $Id: ip_vs_sh.c,v 1.5 2002/09/15 08:14:08 wensong Exp $
5 *
6 * Authors: Wensong Zhang <wensong@gnuchina.org>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version
11 * 2 of the License, or (at your option) any later version.
12 *
13 * Changes:
14 *
15 */
16
17/*
18 * The sh algorithm is to select server by the hash key of source IP
19 * address. The pseudo code is as follows:
20 *
21 * n <- servernode[src_ip];
22 * if (n is dead) OR
23 * (n is overloaded) or (n.weight <= 0) then
24 * return NULL;
25 *
26 * return n;
27 *
28 * Notes that servernode is a 256-bucket hash table that maps the hash
29 * index derived from packet source IP address to the current server
30 * array. If the sh scheduler is used in cache cluster, it is good to
31 * combine it with cache_bypass feature. When the statically assigned
32 * server is dead or overloaded, the load balancer can bypass the cache
33 * server and send requests to the original server directly.
34 *
35 */
36
Arnaldo Carvalho de Melo14c85022005-12-27 02:43:12 -020037#include <linux/ip.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <linux/module.h>
39#include <linux/kernel.h>
Arnaldo Carvalho de Melo14c85022005-12-27 02:43:12 -020040#include <linux/skbuff.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070041
42#include <net/ip_vs.h>
43
44
45/*
46 * IPVS SH bucket
47 */
48struct ip_vs_sh_bucket {
49 struct ip_vs_dest *dest; /* real server (cache) */
50};
51
52/*
53 * for IPVS SH entry hash table
54 */
55#ifndef CONFIG_IP_VS_SH_TAB_BITS
56#define CONFIG_IP_VS_SH_TAB_BITS 8
57#endif
58#define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS
59#define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS)
60#define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1)
61
62
63/*
64 * Returns hash value for IPVS SH entry
65 */
Al Viro014d7302006-09-28 14:29:52 -070066static inline unsigned ip_vs_sh_hashkey(__be32 addr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070067{
68 return (ntohl(addr)*2654435761UL) & IP_VS_SH_TAB_MASK;
69}
70
71
72/*
73 * Get ip_vs_dest associated with supplied parameters.
74 */
75static inline struct ip_vs_dest *
Al Viro014d7302006-09-28 14:29:52 -070076ip_vs_sh_get(struct ip_vs_sh_bucket *tbl, __be32 addr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070077{
78 return (tbl[ip_vs_sh_hashkey(addr)]).dest;
79}
80
81
82/*
83 * Assign all the hash buckets of the specified table with the service.
84 */
85static int
86ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc)
87{
88 int i;
89 struct ip_vs_sh_bucket *b;
90 struct list_head *p;
91 struct ip_vs_dest *dest;
92
93 b = tbl;
94 p = &svc->destinations;
95 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
96 if (list_empty(p)) {
97 b->dest = NULL;
98 } else {
99 if (p == &svc->destinations)
100 p = p->next;
101
102 dest = list_entry(p, struct ip_vs_dest, n_list);
103 atomic_inc(&dest->refcnt);
104 b->dest = dest;
105
106 p = p->next;
107 }
108 b++;
109 }
110 return 0;
111}
112
113
114/*
115 * Flush all the hash buckets of the specified table.
116 */
117static void ip_vs_sh_flush(struct ip_vs_sh_bucket *tbl)
118{
119 int i;
120 struct ip_vs_sh_bucket *b;
121
122 b = tbl;
123 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
124 if (b->dest) {
125 atomic_dec(&b->dest->refcnt);
126 b->dest = NULL;
127 }
128 b++;
129 }
130}
131
132
133static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
134{
135 struct ip_vs_sh_bucket *tbl;
136
137 /* allocate the SH table for this service */
138 tbl = kmalloc(sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE,
139 GFP_ATOMIC);
140 if (tbl == NULL) {
141 IP_VS_ERR("ip_vs_sh_init_svc(): no memory\n");
142 return -ENOMEM;
143 }
144 svc->sched_data = tbl;
145 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for "
146 "current service\n",
147 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
148
149 /* assign the hash buckets with the updated service */
150 ip_vs_sh_assign(tbl, svc);
151
152 return 0;
153}
154
155
156static int ip_vs_sh_done_svc(struct ip_vs_service *svc)
157{
158 struct ip_vs_sh_bucket *tbl = svc->sched_data;
159
160 /* got to clean up hash buckets here */
161 ip_vs_sh_flush(tbl);
162
163 /* release the table itself */
164 kfree(svc->sched_data);
165 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n",
166 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
167
168 return 0;
169}
170
171
172static int ip_vs_sh_update_svc(struct ip_vs_service *svc)
173{
174 struct ip_vs_sh_bucket *tbl = svc->sched_data;
175
176 /* got to clean up hash buckets here */
177 ip_vs_sh_flush(tbl);
178
179 /* assign the hash buckets with the updated service */
180 ip_vs_sh_assign(tbl, svc);
181
182 return 0;
183}
184
185
186/*
187 * If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
188 * consider that the server is overloaded here.
189 */
190static inline int is_overloaded(struct ip_vs_dest *dest)
191{
192 return dest->flags & IP_VS_DEST_F_OVERLOAD;
193}
194
195
196/*
197 * Source Hashing scheduling
198 */
199static struct ip_vs_dest *
200ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
201{
202 struct ip_vs_dest *dest;
203 struct ip_vs_sh_bucket *tbl;
204 struct iphdr *iph = skb->nh.iph;
205
206 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
207
208 tbl = (struct ip_vs_sh_bucket *)svc->sched_data;
209 dest = ip_vs_sh_get(tbl, iph->saddr);
210 if (!dest
211 || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
212 || atomic_read(&dest->weight) <= 0
213 || is_overloaded(dest)) {
214 return NULL;
215 }
216
217 IP_VS_DBG(6, "SH: source IP address %u.%u.%u.%u "
218 "--> server %u.%u.%u.%u:%d\n",
219 NIPQUAD(iph->saddr),
220 NIPQUAD(dest->addr),
221 ntohs(dest->port));
222
223 return dest;
224}
225
226
227/*
228 * IPVS SH Scheduler structure
229 */
230static struct ip_vs_scheduler ip_vs_sh_scheduler =
231{
232 .name = "sh",
233 .refcnt = ATOMIC_INIT(0),
234 .module = THIS_MODULE,
235 .init_service = ip_vs_sh_init_svc,
236 .done_service = ip_vs_sh_done_svc,
237 .update_service = ip_vs_sh_update_svc,
238 .schedule = ip_vs_sh_schedule,
239};
240
241
242static int __init ip_vs_sh_init(void)
243{
244 INIT_LIST_HEAD(&ip_vs_sh_scheduler.n_list);
245 return register_ip_vs_scheduler(&ip_vs_sh_scheduler);
246}
247
248
249static void __exit ip_vs_sh_cleanup(void)
250{
251 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler);
252}
253
254
255module_init(ip_vs_sh_init);
256module_exit(ip_vs_sh_cleanup);
257MODULE_LICENSE("GPL");