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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * IPVS: Destination Hashing scheduling module
3 *
4 * Version: $Id: ip_vs_dh.c,v 1.5 2002/09/15 08:14:08 wensong Exp $
5 *
6 * Authors: Wensong Zhang <wensong@gnuchina.org>
7 *
8 * Inspired by the consistent hashing scheduler patch from
9 * Thomas Proell <proellt@gmx.de>
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version
14 * 2 of the License, or (at your option) any later version.
15 *
16 * Changes:
17 *
18 */
19
20/*
21 * The dh algorithm is to select server by the hash key of destination IP
22 * address. The pseudo code is as follows:
23 *
24 * n <- servernode[dest_ip];
25 * if (n is dead) OR
26 * (n is overloaded) OR (n.weight <= 0) then
27 * return NULL;
28 *
29 * return n;
30 *
31 * Notes that servernode is a 256-bucket hash table that maps the hash
32 * index derived from packet destination IP address to the current server
33 * array. If the dh scheduler is used in cache cluster, it is good to
34 * combine it with cache_bypass feature. When the statically assigned
35 * server is dead or overloaded, the load balancer can bypass the cache
36 * server and send requests to the original server directly.
37 *
38 */
39
Arnaldo Carvalho de Melo14c85022005-12-27 02:43:12 -020040#include <linux/ip.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070041#include <linux/module.h>
42#include <linux/kernel.h>
Arnaldo Carvalho de Melo14c85022005-12-27 02:43:12 -020043#include <linux/skbuff.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45#include <net/ip_vs.h>
46
47
48/*
49 * IPVS DH bucket
50 */
51struct ip_vs_dh_bucket {
52 struct ip_vs_dest *dest; /* real server (cache) */
53};
54
55/*
56 * for IPVS DH entry hash table
57 */
58#ifndef CONFIG_IP_VS_DH_TAB_BITS
59#define CONFIG_IP_VS_DH_TAB_BITS 8
60#endif
61#define IP_VS_DH_TAB_BITS CONFIG_IP_VS_DH_TAB_BITS
62#define IP_VS_DH_TAB_SIZE (1 << IP_VS_DH_TAB_BITS)
63#define IP_VS_DH_TAB_MASK (IP_VS_DH_TAB_SIZE - 1)
64
65
66/*
67 * Returns hash value for IPVS DH entry
68 */
Al Viro014d7302006-09-28 14:29:52 -070069static inline unsigned ip_vs_dh_hashkey(__be32 addr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070070{
71 return (ntohl(addr)*2654435761UL) & IP_VS_DH_TAB_MASK;
72}
73
74
75/*
76 * Get ip_vs_dest associated with supplied parameters.
77 */
78static inline struct ip_vs_dest *
Al Viro014d7302006-09-28 14:29:52 -070079ip_vs_dh_get(struct ip_vs_dh_bucket *tbl, __be32 addr)
Linus Torvalds1da177e2005-04-16 15:20:36 -070080{
81 return (tbl[ip_vs_dh_hashkey(addr)]).dest;
82}
83
84
85/*
86 * Assign all the hash buckets of the specified table with the service.
87 */
88static int
89ip_vs_dh_assign(struct ip_vs_dh_bucket *tbl, struct ip_vs_service *svc)
90{
91 int i;
92 struct ip_vs_dh_bucket *b;
93 struct list_head *p;
94 struct ip_vs_dest *dest;
95
96 b = tbl;
97 p = &svc->destinations;
98 for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
99 if (list_empty(p)) {
100 b->dest = NULL;
101 } else {
102 if (p == &svc->destinations)
103 p = p->next;
104
105 dest = list_entry(p, struct ip_vs_dest, n_list);
106 atomic_inc(&dest->refcnt);
107 b->dest = dest;
108
109 p = p->next;
110 }
111 b++;
112 }
113 return 0;
114}
115
116
117/*
118 * Flush all the hash buckets of the specified table.
119 */
120static void ip_vs_dh_flush(struct ip_vs_dh_bucket *tbl)
121{
122 int i;
123 struct ip_vs_dh_bucket *b;
124
125 b = tbl;
126 for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
127 if (b->dest) {
128 atomic_dec(&b->dest->refcnt);
129 b->dest = NULL;
130 }
131 b++;
132 }
133}
134
135
136static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
137{
138 struct ip_vs_dh_bucket *tbl;
139
140 /* allocate the DH table for this service */
141 tbl = kmalloc(sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE,
142 GFP_ATOMIC);
143 if (tbl == NULL) {
144 IP_VS_ERR("ip_vs_dh_init_svc(): no memory\n");
145 return -ENOMEM;
146 }
147 svc->sched_data = tbl;
148 IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) allocated for "
149 "current service\n",
150 sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
151
152 /* assign the hash buckets with the updated service */
153 ip_vs_dh_assign(tbl, svc);
154
155 return 0;
156}
157
158
159static int ip_vs_dh_done_svc(struct ip_vs_service *svc)
160{
161 struct ip_vs_dh_bucket *tbl = svc->sched_data;
162
163 /* got to clean up hash buckets here */
164 ip_vs_dh_flush(tbl);
165
166 /* release the table itself */
167 kfree(svc->sched_data);
168 IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) released\n",
169 sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
170
171 return 0;
172}
173
174
175static int ip_vs_dh_update_svc(struct ip_vs_service *svc)
176{
177 struct ip_vs_dh_bucket *tbl = svc->sched_data;
178
179 /* got to clean up hash buckets here */
180 ip_vs_dh_flush(tbl);
181
182 /* assign the hash buckets with the updated service */
183 ip_vs_dh_assign(tbl, svc);
184
185 return 0;
186}
187
188
189/*
190 * If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
191 * consider that the server is overloaded here.
192 */
193static inline int is_overloaded(struct ip_vs_dest *dest)
194{
195 return dest->flags & IP_VS_DEST_F_OVERLOAD;
196}
197
198
199/*
200 * Destination hashing scheduling
201 */
202static struct ip_vs_dest *
203ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
204{
205 struct ip_vs_dest *dest;
206 struct ip_vs_dh_bucket *tbl;
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -0700207 struct iphdr *iph = ip_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208
209 IP_VS_DBG(6, "ip_vs_dh_schedule(): Scheduling...\n");
210
211 tbl = (struct ip_vs_dh_bucket *)svc->sched_data;
212 dest = ip_vs_dh_get(tbl, iph->daddr);
213 if (!dest
214 || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
215 || atomic_read(&dest->weight) <= 0
216 || is_overloaded(dest)) {
217 return NULL;
218 }
219
220 IP_VS_DBG(6, "DH: destination IP address %u.%u.%u.%u "
221 "--> server %u.%u.%u.%u:%d\n",
222 NIPQUAD(iph->daddr),
223 NIPQUAD(dest->addr),
224 ntohs(dest->port));
225
226 return dest;
227}
228
229
230/*
231 * IPVS DH Scheduler structure
232 */
233static struct ip_vs_scheduler ip_vs_dh_scheduler =
234{
235 .name = "dh",
236 .refcnt = ATOMIC_INIT(0),
237 .module = THIS_MODULE,
238 .init_service = ip_vs_dh_init_svc,
239 .done_service = ip_vs_dh_done_svc,
240 .update_service = ip_vs_dh_update_svc,
241 .schedule = ip_vs_dh_schedule,
242};
243
244
245static int __init ip_vs_dh_init(void)
246{
247 INIT_LIST_HEAD(&ip_vs_dh_scheduler.n_list);
248 return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
249}
250
251
252static void __exit ip_vs_dh_cleanup(void)
253{
254 unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
255}
256
257
258module_init(ip_vs_dh_init);
259module_exit(ip_vs_dh_cleanup);
260MODULE_LICENSE("GPL");