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cb7f6a7b JV |
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 | ||
9aada7ac HE |
38 | #define KMSG_COMPONENT "IPVS" |
39 | #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt | |
40 | ||
cb7f6a7b JV |
41 | #include <linux/ip.h> |
42 | #include <linux/module.h> | |
43 | #include <linux/kernel.h> | |
44 | #include <linux/skbuff.h> | |
45 | ||
46 | #include <net/ip_vs.h> | |
47 | ||
48 | ||
49 | /* | |
50 | * IPVS DH bucket | |
51 | */ | |
52 | struct ip_vs_dh_bucket { | |
53 | struct ip_vs_dest *dest; /* real server (cache) */ | |
54 | }; | |
55 | ||
56 | /* | |
57 | * for IPVS DH entry hash table | |
58 | */ | |
59 | #ifndef CONFIG_IP_VS_DH_TAB_BITS | |
60 | #define CONFIG_IP_VS_DH_TAB_BITS 8 | |
61 | #endif | |
62 | #define IP_VS_DH_TAB_BITS CONFIG_IP_VS_DH_TAB_BITS | |
63 | #define IP_VS_DH_TAB_SIZE (1 << IP_VS_DH_TAB_BITS) | |
64 | #define IP_VS_DH_TAB_MASK (IP_VS_DH_TAB_SIZE - 1) | |
65 | ||
66 | ||
67 | /* | |
68 | * Returns hash value for IPVS DH entry | |
69 | */ | |
20971a0a | 70 | static inline unsigned ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr) |
cb7f6a7b | 71 | { |
20971a0a JV |
72 | __be32 addr_fold = addr->ip; |
73 | ||
74 | #ifdef CONFIG_IP_VS_IPV6 | |
75 | if (af == AF_INET6) | |
76 | addr_fold = addr->ip6[0]^addr->ip6[1]^ | |
77 | addr->ip6[2]^addr->ip6[3]; | |
78 | #endif | |
79 | return (ntohl(addr_fold)*2654435761UL) & IP_VS_DH_TAB_MASK; | |
cb7f6a7b JV |
80 | } |
81 | ||
82 | ||
83 | /* | |
84 | * Get ip_vs_dest associated with supplied parameters. | |
85 | */ | |
86 | static inline struct ip_vs_dest * | |
20971a0a JV |
87 | ip_vs_dh_get(int af, struct ip_vs_dh_bucket *tbl, |
88 | const union nf_inet_addr *addr) | |
cb7f6a7b | 89 | { |
20971a0a | 90 | return (tbl[ip_vs_dh_hashkey(af, addr)]).dest; |
cb7f6a7b JV |
91 | } |
92 | ||
93 | ||
94 | /* | |
95 | * Assign all the hash buckets of the specified table with the service. | |
96 | */ | |
97 | static int | |
98 | ip_vs_dh_assign(struct ip_vs_dh_bucket *tbl, struct ip_vs_service *svc) | |
99 | { | |
100 | int i; | |
101 | struct ip_vs_dh_bucket *b; | |
102 | struct list_head *p; | |
103 | struct ip_vs_dest *dest; | |
104 | ||
105 | b = tbl; | |
106 | p = &svc->destinations; | |
107 | for (i=0; i<IP_VS_DH_TAB_SIZE; i++) { | |
108 | if (list_empty(p)) { | |
109 | b->dest = NULL; | |
110 | } else { | |
111 | if (p == &svc->destinations) | |
112 | p = p->next; | |
113 | ||
114 | dest = list_entry(p, struct ip_vs_dest, n_list); | |
115 | atomic_inc(&dest->refcnt); | |
116 | b->dest = dest; | |
117 | ||
118 | p = p->next; | |
119 | } | |
120 | b++; | |
121 | } | |
122 | return 0; | |
123 | } | |
124 | ||
125 | ||
126 | /* | |
127 | * Flush all the hash buckets of the specified table. | |
128 | */ | |
129 | static void ip_vs_dh_flush(struct ip_vs_dh_bucket *tbl) | |
130 | { | |
131 | int i; | |
132 | struct ip_vs_dh_bucket *b; | |
133 | ||
134 | b = tbl; | |
135 | for (i=0; i<IP_VS_DH_TAB_SIZE; i++) { | |
136 | if (b->dest) { | |
137 | atomic_dec(&b->dest->refcnt); | |
138 | b->dest = NULL; | |
139 | } | |
140 | b++; | |
141 | } | |
142 | } | |
143 | ||
144 | ||
145 | static int ip_vs_dh_init_svc(struct ip_vs_service *svc) | |
146 | { | |
147 | struct ip_vs_dh_bucket *tbl; | |
148 | ||
149 | /* allocate the DH table for this service */ | |
150 | tbl = kmalloc(sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE, | |
151 | GFP_ATOMIC); | |
152 | if (tbl == NULL) { | |
1e3e238e | 153 | pr_err("%s(): no memory\n", __func__); |
cb7f6a7b JV |
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 | ||
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 | ||
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 | */ | |
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 * | |
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; | |
20971a0a JV |
216 | struct ip_vs_iphdr iph; |
217 | ||
218 | ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph); | |
cb7f6a7b | 219 | |
1e3e238e | 220 | IP_VS_DBG(6, "%s(): Scheduling...\n", __func__); |
cb7f6a7b JV |
221 | |
222 | tbl = (struct ip_vs_dh_bucket *)svc->sched_data; | |
20971a0a | 223 | dest = ip_vs_dh_get(svc->af, tbl, &iph.daddr); |
cb7f6a7b JV |
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 | ||
20971a0a JV |
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)); | |
cb7f6a7b JV |
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), | |
cb7f6a7b JV |
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 | ||
256 | static int __init ip_vs_dh_init(void) | |
257 | { | |
258 | return register_ip_vs_scheduler(&ip_vs_dh_scheduler); | |
259 | } | |
260 | ||
261 | ||
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"); |