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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 | 41 | #include <linux/ip.h> |
5a0e3ad6 | 42 | #include <linux/slab.h> |
cb7f6a7b JV |
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 | */ | |
20971a0a | 71 | static inline unsigned ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr) |
cb7f6a7b | 72 | { |
20971a0a JV |
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; | |
cb7f6a7b JV |
81 | } |
82 | ||
83 | ||
84 | /* | |
85 | * Get ip_vs_dest associated with supplied parameters. | |
86 | */ | |
87 | static inline struct ip_vs_dest * | |
20971a0a JV |
88 | ip_vs_dh_get(int af, struct ip_vs_dh_bucket *tbl, |
89 | const union nf_inet_addr *addr) | |
cb7f6a7b | 90 | { |
20971a0a | 91 | return (tbl[ip_vs_dh_hashkey(af, addr)]).dest; |
cb7f6a7b JV |
92 | } |
93 | ||
94 | ||
95 | /* | |
96 | * Assign all the hash buckets of the specified table with the service. | |
97 | */ | |
98 | static int | |
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 | */ | |
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 | ||
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) { | |
1e3e238e | 154 | pr_err("%s(): no memory\n", __func__); |
cb7f6a7b JV |
155 | return -ENOMEM; |
156 | } | |
157 | svc->sched_data = tbl; | |
158 | IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) allocated for " | |
159 | "current service\n", | |
160 | sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE); | |
161 | ||
162 | /* assign the hash buckets with the updated service */ | |
163 | ip_vs_dh_assign(tbl, svc); | |
164 | ||
165 | return 0; | |
166 | } | |
167 | ||
168 | ||
169 | static int ip_vs_dh_done_svc(struct ip_vs_service *svc) | |
170 | { | |
171 | struct ip_vs_dh_bucket *tbl = svc->sched_data; | |
172 | ||
173 | /* got to clean up hash buckets here */ | |
174 | ip_vs_dh_flush(tbl); | |
175 | ||
176 | /* release the table itself */ | |
177 | kfree(svc->sched_data); | |
178 | IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) released\n", | |
179 | sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE); | |
180 | ||
181 | return 0; | |
182 | } | |
183 | ||
184 | ||
185 | static int ip_vs_dh_update_svc(struct ip_vs_service *svc) | |
186 | { | |
187 | struct ip_vs_dh_bucket *tbl = svc->sched_data; | |
188 | ||
189 | /* got to clean up hash buckets here */ | |
190 | ip_vs_dh_flush(tbl); | |
191 | ||
192 | /* assign the hash buckets with the updated service */ | |
193 | ip_vs_dh_assign(tbl, svc); | |
194 | ||
195 | return 0; | |
196 | } | |
197 | ||
198 | ||
199 | /* | |
200 | * If the dest flags is set with IP_VS_DEST_F_OVERLOAD, | |
201 | * consider that the server is overloaded here. | |
202 | */ | |
203 | static inline int is_overloaded(struct ip_vs_dest *dest) | |
204 | { | |
205 | return dest->flags & IP_VS_DEST_F_OVERLOAD; | |
206 | } | |
207 | ||
208 | ||
209 | /* | |
210 | * Destination hashing scheduling | |
211 | */ | |
212 | static struct ip_vs_dest * | |
213 | ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb) | |
214 | { | |
215 | struct ip_vs_dest *dest; | |
216 | struct ip_vs_dh_bucket *tbl; | |
20971a0a JV |
217 | struct ip_vs_iphdr iph; |
218 | ||
219 | ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph); | |
cb7f6a7b | 220 | |
1e3e238e | 221 | IP_VS_DBG(6, "%s(): Scheduling...\n", __func__); |
cb7f6a7b JV |
222 | |
223 | tbl = (struct ip_vs_dh_bucket *)svc->sched_data; | |
20971a0a | 224 | dest = ip_vs_dh_get(svc->af, tbl, &iph.daddr); |
cb7f6a7b JV |
225 | if (!dest |
226 | || !(dest->flags & IP_VS_DEST_F_AVAILABLE) | |
227 | || atomic_read(&dest->weight) <= 0 | |
228 | || is_overloaded(dest)) { | |
229 | return NULL; | |
230 | } | |
231 | ||
20971a0a JV |
232 | IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n", |
233 | IP_VS_DBG_ADDR(svc->af, &iph.daddr), | |
234 | IP_VS_DBG_ADDR(svc->af, &dest->addr), | |
235 | ntohs(dest->port)); | |
cb7f6a7b JV |
236 | |
237 | return dest; | |
238 | } | |
239 | ||
240 | ||
241 | /* | |
242 | * IPVS DH Scheduler structure | |
243 | */ | |
244 | static struct ip_vs_scheduler ip_vs_dh_scheduler = | |
245 | { | |
246 | .name = "dh", | |
247 | .refcnt = ATOMIC_INIT(0), | |
248 | .module = THIS_MODULE, | |
249 | .n_list = LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list), | |
cb7f6a7b JV |
250 | .init_service = ip_vs_dh_init_svc, |
251 | .done_service = ip_vs_dh_done_svc, | |
252 | .update_service = ip_vs_dh_update_svc, | |
253 | .schedule = ip_vs_dh_schedule, | |
254 | }; | |
255 | ||
256 | ||
257 | static int __init ip_vs_dh_init(void) | |
258 | { | |
259 | return register_ip_vs_scheduler(&ip_vs_dh_scheduler); | |
260 | } | |
261 | ||
262 | ||
263 | static void __exit ip_vs_dh_cleanup(void) | |
264 | { | |
265 | unregister_ip_vs_scheduler(&ip_vs_dh_scheduler); | |
266 | } | |
267 | ||
268 | ||
269 | module_init(ip_vs_dh_init); | |
270 | module_exit(ip_vs_dh_cleanup); | |
271 | MODULE_LICENSE("GPL"); |