1 /*
2 * IPVS: Destination Hashing scheduling module
3 *
4 * Authors: Wensong Zhang <wensong@gnuchina.org>
5 *
6 * Inspired by the consistent hashing scheduler patch from
7 * Thomas Proell <proellt@gmx.de>
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * as published by the Free Software Foundation; either version
12 * 2 of the License, or (at your option) any later version.
13 *
14 * Changes:
15 *
16 */
17
18 /*
19 * The dh algorithm is to select server by the hash key of destination IP
20 * address. The pseudo code is as follows:
21 *
22 * n <- servernode[dest_ip];
23 * if (n is dead) OR
24 * (n is overloaded) OR (n.weight <= 0) then
25 * return NULL;
26 *
27 * return n;
28 *
29 * Notes that servernode is a 256-bucket hash table that maps the hash
30 * index derived from packet destination IP address to the current server
31 * array. If the dh scheduler is used in cache cluster, it is good to
32 * combine it with cache_bypass feature. When the statically assigned
33 * server is dead or overloaded, the load balancer can bypass the cache
34 * server and send requests to the original server directly.
35 *
36 */
37
38 #define KMSG_COMPONENT "IPVS"
39 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
40
41 #include <linux/ip.h>
42 #include <linux/slab.h>
43 #include <linux/module.h>
44 #include <linux/kernel.h>
45 #include <linux/skbuff.h>
46
47 #include <net/ip_vs.h>
48
49
50 /*
51 * IPVS DH bucket
52 */
53 struct ip_vs_dh_bucket {
54 struct ip_vs_dest *dest; /* real server (cache) */
55 };
56
57 /*
58 * for IPVS DH entry hash table
59 */
60 #ifndef CONFIG_IP_VS_DH_TAB_BITS
61 #define CONFIG_IP_VS_DH_TAB_BITS 8
62 #endif
63 #define IP_VS_DH_TAB_BITS CONFIG_IP_VS_DH_TAB_BITS
64 #define IP_VS_DH_TAB_SIZE (1 << IP_VS_DH_TAB_BITS)
65 #define IP_VS_DH_TAB_MASK (IP_VS_DH_TAB_SIZE - 1)
66
67
68 /*
69 * Returns hash value for IPVS DH entry
70 */
ip_vs_dh_hashkey(int af,const union nf_inet_addr * addr)71 static inline unsigned ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr)
72 {
73 __be32 addr_fold = addr->ip;
74
75 #ifdef CONFIG_IP_VS_IPV6
76 if (af == AF_INET6)
77 addr_fold = addr->ip6[0]^addr->ip6[1]^
78 addr->ip6[2]^addr->ip6[3];
79 #endif
80 return (ntohl(addr_fold)*2654435761UL) & IP_VS_DH_TAB_MASK;
81 }
82
83
84 /*
85 * Get ip_vs_dest associated with supplied parameters.
86 */
87 static inline struct ip_vs_dest *
ip_vs_dh_get(int af,struct ip_vs_dh_bucket * tbl,const union nf_inet_addr * addr)88 ip_vs_dh_get(int af, struct ip_vs_dh_bucket *tbl,
89 const union nf_inet_addr *addr)
90 {
91 return (tbl[ip_vs_dh_hashkey(af, addr)]).dest;
92 }
93
94
95 /*
96 * Assign all the hash buckets of the specified table with the service.
97 */
98 static int
ip_vs_dh_assign(struct ip_vs_dh_bucket * tbl,struct ip_vs_service * svc)99 ip_vs_dh_assign(struct ip_vs_dh_bucket *tbl, struct ip_vs_service *svc)
100 {
101 int i;
102 struct ip_vs_dh_bucket *b;
103 struct list_head *p;
104 struct ip_vs_dest *dest;
105
106 b = tbl;
107 p = &svc->destinations;
108 for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
109 if (list_empty(p)) {
110 b->dest = NULL;
111 } else {
112 if (p == &svc->destinations)
113 p = p->next;
114
115 dest = list_entry(p, struct ip_vs_dest, n_list);
116 atomic_inc(&dest->refcnt);
117 b->dest = dest;
118
119 p = p->next;
120 }
121 b++;
122 }
123 return 0;
124 }
125
126
127 /*
128 * Flush all the hash buckets of the specified table.
129 */
ip_vs_dh_flush(struct ip_vs_dh_bucket * tbl)130 static void ip_vs_dh_flush(struct ip_vs_dh_bucket *tbl)
131 {
132 int i;
133 struct ip_vs_dh_bucket *b;
134
135 b = tbl;
136 for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
137 if (b->dest) {
138 atomic_dec(&b->dest->refcnt);
139 b->dest = NULL;
140 }
141 b++;
142 }
143 }
144
145
ip_vs_dh_init_svc(struct ip_vs_service * svc)146 static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
147 {
148 struct ip_vs_dh_bucket *tbl;
149
150 /* allocate the DH table for this service */
151 tbl = kmalloc(sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE,
152 GFP_ATOMIC);
153 if (tbl == NULL)
154 return -ENOMEM;
155
156 svc->sched_data = tbl;
157 IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) allocated for "
158 "current service\n",
159 sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
160
161 /* assign the hash buckets with the updated service */
162 ip_vs_dh_assign(tbl, svc);
163
164 return 0;
165 }
166
167
ip_vs_dh_done_svc(struct ip_vs_service * svc)168 static int ip_vs_dh_done_svc(struct ip_vs_service *svc)
169 {
170 struct ip_vs_dh_bucket *tbl = svc->sched_data;
171
172 /* got to clean up hash buckets here */
173 ip_vs_dh_flush(tbl);
174
175 /* release the table itself */
176 kfree(svc->sched_data);
177 IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) released\n",
178 sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
179
180 return 0;
181 }
182
183
ip_vs_dh_update_svc(struct ip_vs_service * svc)184 static int ip_vs_dh_update_svc(struct ip_vs_service *svc)
185 {
186 struct ip_vs_dh_bucket *tbl = svc->sched_data;
187
188 /* got to clean up hash buckets here */
189 ip_vs_dh_flush(tbl);
190
191 /* assign the hash buckets with the updated service */
192 ip_vs_dh_assign(tbl, svc);
193
194 return 0;
195 }
196
197
198 /*
199 * If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
200 * consider that the server is overloaded here.
201 */
is_overloaded(struct ip_vs_dest * dest)202 static inline int is_overloaded(struct ip_vs_dest *dest)
203 {
204 return dest->flags & IP_VS_DEST_F_OVERLOAD;
205 }
206
207
208 /*
209 * Destination hashing scheduling
210 */
211 static struct ip_vs_dest *
ip_vs_dh_schedule(struct ip_vs_service * svc,const struct sk_buff * skb)212 ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
213 {
214 struct ip_vs_dest *dest;
215 struct ip_vs_dh_bucket *tbl;
216 struct ip_vs_iphdr iph;
217
218 ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph);
219
220 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
221
222 tbl = (struct ip_vs_dh_bucket *)svc->sched_data;
223 dest = ip_vs_dh_get(svc->af, tbl, &iph.daddr);
224 if (!dest
225 || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
226 || atomic_read(&dest->weight) <= 0
227 || is_overloaded(dest)) {
228 return NULL;
229 }
230
231 IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n",
232 IP_VS_DBG_ADDR(svc->af, &iph.daddr),
233 IP_VS_DBG_ADDR(svc->af, &dest->addr),
234 ntohs(dest->port));
235
236 return dest;
237 }
238
239
240 /*
241 * IPVS DH Scheduler structure
242 */
243 static struct ip_vs_scheduler ip_vs_dh_scheduler =
244 {
245 .name = "dh",
246 .refcnt = ATOMIC_INIT(0),
247 .module = THIS_MODULE,
248 .n_list = LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
249 .init_service = ip_vs_dh_init_svc,
250 .done_service = ip_vs_dh_done_svc,
251 .update_service = ip_vs_dh_update_svc,
252 .schedule = ip_vs_dh_schedule,
253 };
254
255
ip_vs_dh_init(void)256 static int __init ip_vs_dh_init(void)
257 {
258 return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
259 }
260
261
ip_vs_dh_cleanup(void)262 static void __exit ip_vs_dh_cleanup(void)
263 {
264 unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
265 }
266
267
268 module_init(ip_vs_dh_init);
269 module_exit(ip_vs_dh_cleanup);
270 MODULE_LICENSE("GPL");
271