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 #include <net/tcp.h> 52 #include <linux/udp.h> 53 #include <linux/sctp.h> 54 55 56 /* 57 * IPVS SH bucket 58 */ 59 struct ip_vs_sh_bucket { 60 struct ip_vs_dest __rcu *dest; /* real server (cache) */ 61 }; 62 63 /* 64 * for IPVS SH entry hash table 65 */ 66 #ifndef CONFIG_IP_VS_SH_TAB_BITS 67 #define CONFIG_IP_VS_SH_TAB_BITS 8 68 #endif 69 #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS 70 #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS) 71 #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1) 72 73 struct ip_vs_sh_state { 74 struct rcu_head rcu_head; 75 struct ip_vs_sh_bucket buckets[IP_VS_SH_TAB_SIZE]; 76 }; 77 78 /* Helper function to determine if server is unavailable */ 79 static inline bool is_unavailable(struct ip_vs_dest *dest) 80 { 81 return atomic_read(&dest->weight) <= 0 || 82 dest->flags & IP_VS_DEST_F_OVERLOAD; 83 } 84 85 /* 86 * Returns hash value for IPVS SH entry 87 */ 88 static inline unsigned int 89 ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr, 90 __be16 port, unsigned int offset) 91 { 92 __be32 addr_fold = addr->ip; 93 94 #ifdef CONFIG_IP_VS_IPV6 95 if (af == AF_INET6) 96 addr_fold = addr->ip6[0]^addr->ip6[1]^ 97 addr->ip6[2]^addr->ip6[3]; 98 #endif 99 return (offset + (ntohs(port) + ntohl(addr_fold))*2654435761UL) & 100 IP_VS_SH_TAB_MASK; 101 } 102 103 104 /* 105 * Get ip_vs_dest associated with supplied parameters. 106 */ 107 static inline struct ip_vs_dest * 108 ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s, 109 const union nf_inet_addr *addr, __be16 port) 110 { 111 unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0); 112 struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest); 113 114 return (!dest || is_unavailable(dest)) ? NULL : dest; 115 } 116 117 118 /* As ip_vs_sh_get, but with fallback if selected server is unavailable 119 * 120 * The fallback strategy loops around the table starting from a "random" 121 * point (in fact, it is chosen to be the original hash value to make the 122 * algorithm deterministic) to find a new server. 123 */ 124 static inline struct ip_vs_dest * 125 ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s, 126 const union nf_inet_addr *addr, __be16 port) 127 { 128 unsigned int offset, roffset; 129 unsigned int hash, ihash; 130 struct ip_vs_dest *dest; 131 132 /* first try the dest it's supposed to go to */ 133 ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0); 134 dest = rcu_dereference(s->buckets[ihash].dest); 135 if (!dest) 136 return NULL; 137 if (!is_unavailable(dest)) 138 return dest; 139 140 IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting", 141 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port)); 142 143 /* if the original dest is unavailable, loop around the table 144 * starting from ihash to find a new dest 145 */ 146 for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) { 147 roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE; 148 hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset); 149 dest = rcu_dereference(s->buckets[hash].dest); 150 if (!dest) 151 break; 152 if (!is_unavailable(dest)) 153 return dest; 154 IP_VS_DBG_BUF(6, "SH: selected unavailable " 155 "server %s:%d (offset %d), reselecting", 156 IP_VS_DBG_ADDR(dest->af, &dest->addr), 157 ntohs(dest->port), roffset); 158 } 159 160 return NULL; 161 } 162 163 /* 164 * Assign all the hash buckets of the specified table with the service. 165 */ 166 static int 167 ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc) 168 { 169 int i; 170 struct ip_vs_sh_bucket *b; 171 struct list_head *p; 172 struct ip_vs_dest *dest; 173 int d_count; 174 bool empty; 175 176 b = &s->buckets[0]; 177 p = &svc->destinations; 178 empty = list_empty(p); 179 d_count = 0; 180 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 181 dest = rcu_dereference_protected(b->dest, 1); 182 if (dest) 183 ip_vs_dest_put(dest); 184 if (empty) 185 RCU_INIT_POINTER(b->dest, NULL); 186 else { 187 if (p == &svc->destinations) 188 p = p->next; 189 190 dest = list_entry(p, struct ip_vs_dest, n_list); 191 ip_vs_dest_hold(dest); 192 RCU_INIT_POINTER(b->dest, dest); 193 194 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n", 195 i, IP_VS_DBG_ADDR(dest->af, &dest->addr), 196 atomic_read(&dest->weight)); 197 198 /* Don't move to next dest until filling weight */ 199 if (++d_count >= atomic_read(&dest->weight)) { 200 p = p->next; 201 d_count = 0; 202 } 203 204 } 205 b++; 206 } 207 return 0; 208 } 209 210 211 /* 212 * Flush all the hash buckets of the specified table. 213 */ 214 static void ip_vs_sh_flush(struct ip_vs_sh_state *s) 215 { 216 int i; 217 struct ip_vs_sh_bucket *b; 218 struct ip_vs_dest *dest; 219 220 b = &s->buckets[0]; 221 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 222 dest = rcu_dereference_protected(b->dest, 1); 223 if (dest) { 224 ip_vs_dest_put(dest); 225 RCU_INIT_POINTER(b->dest, NULL); 226 } 227 b++; 228 } 229 } 230 231 232 static int ip_vs_sh_init_svc(struct ip_vs_service *svc) 233 { 234 struct ip_vs_sh_state *s; 235 236 /* allocate the SH table for this service */ 237 s = kzalloc(sizeof(struct ip_vs_sh_state), GFP_KERNEL); 238 if (s == NULL) 239 return -ENOMEM; 240 241 svc->sched_data = s; 242 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for " 243 "current service\n", 244 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 245 246 /* assign the hash buckets with current dests */ 247 ip_vs_sh_reassign(s, svc); 248 249 return 0; 250 } 251 252 253 static void ip_vs_sh_done_svc(struct ip_vs_service *svc) 254 { 255 struct ip_vs_sh_state *s = svc->sched_data; 256 257 /* got to clean up hash buckets here */ 258 ip_vs_sh_flush(s); 259 260 /* release the table itself */ 261 kfree_rcu(s, rcu_head); 262 IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n", 263 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 264 } 265 266 267 static int ip_vs_sh_dest_changed(struct ip_vs_service *svc, 268 struct ip_vs_dest *dest) 269 { 270 struct ip_vs_sh_state *s = svc->sched_data; 271 272 /* assign the hash buckets with the updated service */ 273 ip_vs_sh_reassign(s, svc); 274 275 return 0; 276 } 277 278 279 /* Helper function to get port number */ 280 static inline __be16 281 ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph) 282 { 283 __be16 _ports[2], *ports; 284 285 /* At this point we know that we have a valid packet of some kind. 286 * Because ICMP packets are only guaranteed to have the first 8 287 * bytes, let's just grab the ports. Fortunately they're in the 288 * same position for all three of the protocols we care about. 289 */ 290 switch (iph->protocol) { 291 case IPPROTO_TCP: 292 case IPPROTO_UDP: 293 case IPPROTO_SCTP: 294 ports = skb_header_pointer(skb, iph->len, sizeof(_ports), 295 &_ports); 296 if (unlikely(!ports)) 297 return 0; 298 299 if (likely(!ip_vs_iph_inverse(iph))) 300 return ports[0]; 301 else 302 return ports[1]; 303 default: 304 return 0; 305 } 306 } 307 308 309 /* 310 * Source Hashing scheduling 311 */ 312 static struct ip_vs_dest * 313 ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb, 314 struct ip_vs_iphdr *iph) 315 { 316 struct ip_vs_dest *dest; 317 struct ip_vs_sh_state *s; 318 __be16 port = 0; 319 const union nf_inet_addr *hash_addr; 320 321 hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr; 322 323 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n"); 324 325 if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT) 326 port = ip_vs_sh_get_port(skb, iph); 327 328 s = (struct ip_vs_sh_state *) svc->sched_data; 329 330 if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK) 331 dest = ip_vs_sh_get_fallback(svc, s, hash_addr, port); 332 else 333 dest = ip_vs_sh_get(svc, s, hash_addr, port); 334 335 if (!dest) { 336 ip_vs_scheduler_err(svc, "no destination available"); 337 return NULL; 338 } 339 340 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n", 341 IP_VS_DBG_ADDR(svc->af, hash_addr), 342 IP_VS_DBG_ADDR(dest->af, &dest->addr), 343 ntohs(dest->port)); 344 345 return dest; 346 } 347 348 349 /* 350 * IPVS SH Scheduler structure 351 */ 352 static struct ip_vs_scheduler ip_vs_sh_scheduler = 353 { 354 .name = "sh", 355 .refcnt = ATOMIC_INIT(0), 356 .module = THIS_MODULE, 357 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list), 358 .init_service = ip_vs_sh_init_svc, 359 .done_service = ip_vs_sh_done_svc, 360 .add_dest = ip_vs_sh_dest_changed, 361 .del_dest = ip_vs_sh_dest_changed, 362 .upd_dest = ip_vs_sh_dest_changed, 363 .schedule = ip_vs_sh_schedule, 364 }; 365 366 367 static int __init ip_vs_sh_init(void) 368 { 369 return register_ip_vs_scheduler(&ip_vs_sh_scheduler); 370 } 371 372 373 static void __exit ip_vs_sh_cleanup(void) 374 { 375 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler); 376 synchronize_rcu(); 377 } 378 379 380 module_init(ip_vs_sh_init); 381 module_exit(ip_vs_sh_cleanup); 382 MODULE_LICENSE("GPL"); 383