1 /* 2 * IPVS: Source Hashing scheduling module 3 * 4 * Authors: Wensong Zhang <wensong@gnuchina.org> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 * Changes: 12 * 13 */ 14 15 /* 16 * The sh algorithm is to select server by the hash key of source IP 17 * address. The pseudo code is as follows: 18 * 19 * n <- servernode[src_ip]; 20 * if (n is dead) OR 21 * (n is overloaded) or (n.weight <= 0) then 22 * return NULL; 23 * 24 * return n; 25 * 26 * Notes that servernode is a 256-bucket hash table that maps the hash 27 * index derived from packet source IP address to the current server 28 * array. If the sh scheduler is used in cache cluster, it is good to 29 * combine it with cache_bypass feature. When the statically assigned 30 * server is dead or overloaded, the load balancer can bypass the cache 31 * server and send requests to the original server directly. 32 * 33 * The weight destination attribute can be used to control the 34 * distribution of connections to the destinations in servernode. The 35 * greater the weight, the more connections the destination 36 * will receive. 37 * 38 */ 39 40 #define KMSG_COMPONENT "IPVS" 41 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 42 43 #include <linux/ip.h> 44 #include <linux/slab.h> 45 #include <linux/module.h> 46 #include <linux/kernel.h> 47 #include <linux/skbuff.h> 48 49 #include <net/ip_vs.h> 50 51 52 /* 53 * IPVS SH bucket 54 */ 55 struct ip_vs_sh_bucket { 56 struct ip_vs_dest *dest; /* real server (cache) */ 57 }; 58 59 /* 60 * for IPVS SH entry hash table 61 */ 62 #ifndef CONFIG_IP_VS_SH_TAB_BITS 63 #define CONFIG_IP_VS_SH_TAB_BITS 8 64 #endif 65 #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS 66 #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS) 67 #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1) 68 69 70 /* 71 * Returns hash value for IPVS SH entry 72 */ 73 static inline unsigned int ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr) 74 { 75 __be32 addr_fold = addr->ip; 76 77 #ifdef CONFIG_IP_VS_IPV6 78 if (af == AF_INET6) 79 addr_fold = addr->ip6[0]^addr->ip6[1]^ 80 addr->ip6[2]^addr->ip6[3]; 81 #endif 82 return (ntohl(addr_fold)*2654435761UL) & IP_VS_SH_TAB_MASK; 83 } 84 85 86 /* 87 * Get ip_vs_dest associated with supplied parameters. 88 */ 89 static inline struct ip_vs_dest * 90 ip_vs_sh_get(int af, struct ip_vs_sh_bucket *tbl, 91 const union nf_inet_addr *addr) 92 { 93 return (tbl[ip_vs_sh_hashkey(af, addr)]).dest; 94 } 95 96 97 /* 98 * Assign all the hash buckets of the specified table with the service. 99 */ 100 static int 101 ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc) 102 { 103 int i; 104 struct ip_vs_sh_bucket *b; 105 struct list_head *p; 106 struct ip_vs_dest *dest; 107 int d_count; 108 109 b = tbl; 110 p = &svc->destinations; 111 d_count = 0; 112 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 113 if (list_empty(p)) { 114 b->dest = NULL; 115 } else { 116 if (p == &svc->destinations) 117 p = p->next; 118 119 dest = list_entry(p, struct ip_vs_dest, n_list); 120 atomic_inc(&dest->refcnt); 121 b->dest = dest; 122 123 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n", 124 i, IP_VS_DBG_ADDR(svc->af, &dest->addr), 125 atomic_read(&dest->weight)); 126 127 /* Don't move to next dest until filling weight */ 128 if (++d_count >= atomic_read(&dest->weight)) { 129 p = p->next; 130 d_count = 0; 131 } 132 133 } 134 b++; 135 } 136 return 0; 137 } 138 139 140 /* 141 * Flush all the hash buckets of the specified table. 142 */ 143 static void ip_vs_sh_flush(struct ip_vs_sh_bucket *tbl) 144 { 145 int i; 146 struct ip_vs_sh_bucket *b; 147 148 b = tbl; 149 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 150 if (b->dest) { 151 atomic_dec(&b->dest->refcnt); 152 b->dest = NULL; 153 } 154 b++; 155 } 156 } 157 158 159 static int ip_vs_sh_init_svc(struct ip_vs_service *svc) 160 { 161 struct ip_vs_sh_bucket *tbl; 162 163 /* allocate the SH table for this service */ 164 tbl = kmalloc(sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE, 165 GFP_KERNEL); 166 if (tbl == NULL) 167 return -ENOMEM; 168 169 svc->sched_data = tbl; 170 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for " 171 "current service\n", 172 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 173 174 /* assign the hash buckets with the updated service */ 175 ip_vs_sh_assign(tbl, svc); 176 177 return 0; 178 } 179 180 181 static int ip_vs_sh_done_svc(struct ip_vs_service *svc) 182 { 183 struct ip_vs_sh_bucket *tbl = svc->sched_data; 184 185 /* got to clean up hash buckets here */ 186 ip_vs_sh_flush(tbl); 187 188 /* release the table itself */ 189 kfree(svc->sched_data); 190 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n", 191 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 192 193 return 0; 194 } 195 196 197 static int ip_vs_sh_update_svc(struct ip_vs_service *svc) 198 { 199 struct ip_vs_sh_bucket *tbl = svc->sched_data; 200 201 /* got to clean up hash buckets here */ 202 ip_vs_sh_flush(tbl); 203 204 /* assign the hash buckets with the updated service */ 205 ip_vs_sh_assign(tbl, svc); 206 207 return 0; 208 } 209 210 211 /* 212 * If the dest flags is set with IP_VS_DEST_F_OVERLOAD, 213 * consider that the server is overloaded here. 214 */ 215 static inline int is_overloaded(struct ip_vs_dest *dest) 216 { 217 return dest->flags & IP_VS_DEST_F_OVERLOAD; 218 } 219 220 221 /* 222 * Source Hashing scheduling 223 */ 224 static struct ip_vs_dest * 225 ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb) 226 { 227 struct ip_vs_dest *dest; 228 struct ip_vs_sh_bucket *tbl; 229 struct ip_vs_iphdr iph; 230 231 ip_vs_fill_iph_addr_only(svc->af, skb, &iph); 232 233 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n"); 234 235 tbl = (struct ip_vs_sh_bucket *)svc->sched_data; 236 dest = ip_vs_sh_get(svc->af, tbl, &iph.saddr); 237 if (!dest 238 || !(dest->flags & IP_VS_DEST_F_AVAILABLE) 239 || atomic_read(&dest->weight) <= 0 240 || is_overloaded(dest)) { 241 ip_vs_scheduler_err(svc, "no destination available"); 242 return NULL; 243 } 244 245 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n", 246 IP_VS_DBG_ADDR(svc->af, &iph.saddr), 247 IP_VS_DBG_ADDR(svc->af, &dest->addr), 248 ntohs(dest->port)); 249 250 return dest; 251 } 252 253 254 /* 255 * IPVS SH Scheduler structure 256 */ 257 static struct ip_vs_scheduler ip_vs_sh_scheduler = 258 { 259 .name = "sh", 260 .refcnt = ATOMIC_INIT(0), 261 .module = THIS_MODULE, 262 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list), 263 .init_service = ip_vs_sh_init_svc, 264 .done_service = ip_vs_sh_done_svc, 265 .update_service = ip_vs_sh_update_svc, 266 .schedule = ip_vs_sh_schedule, 267 }; 268 269 270 static int __init ip_vs_sh_init(void) 271 { 272 return register_ip_vs_scheduler(&ip_vs_sh_scheduler); 273 } 274 275 276 static void __exit ip_vs_sh_cleanup(void) 277 { 278 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler); 279 } 280 281 282 module_init(ip_vs_sh_init); 283 module_exit(ip_vs_sh_cleanup); 284 MODULE_LICENSE("GPL"); 285