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 */ 59struct 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 73struct 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 */ 79static 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 */ 88static inline unsigned int 89ip_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 */ 107static inline struct ip_vs_dest * 108ip_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 */ 124static inline struct ip_vs_dest * 125ip_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 */ 166static int 167ip_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 */ 214static 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 232static 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 253static 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 267static 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 */ 280static inline __be16 281ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph) 282{ 283 __be16 port; 284 struct tcphdr _tcph, *th; 285 struct udphdr _udph, *uh; 286 sctp_sctphdr_t _sctph, *sh; 287 288 switch (iph->protocol) { 289 case IPPROTO_TCP: 290 th = skb_header_pointer(skb, iph->len, sizeof(_tcph), &_tcph); 291 if (unlikely(th == NULL)) 292 return 0; 293 port = th->source; 294 break; 295 case IPPROTO_UDP: 296 uh = skb_header_pointer(skb, iph->len, sizeof(_udph), &_udph); 297 if (unlikely(uh == NULL)) 298 return 0; 299 port = uh->source; 300 break; 301 case IPPROTO_SCTP: 302 sh = skb_header_pointer(skb, iph->len, sizeof(_sctph), &_sctph); 303 if (unlikely(sh == NULL)) 304 return 0; 305 port = sh->source; 306 break; 307 default: 308 port = 0; 309 } 310 311 return port; 312} 313 314 315/* 316 * Source Hashing scheduling 317 */ 318static struct ip_vs_dest * 319ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb, 320 struct ip_vs_iphdr *iph) 321{ 322 struct ip_vs_dest *dest; 323 struct ip_vs_sh_state *s; 324 __be16 port = 0; 325 326 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n"); 327 328 if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT) 329 port = ip_vs_sh_get_port(skb, iph); 330 331 s = (struct ip_vs_sh_state *) svc->sched_data; 332 333 if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK) 334 dest = ip_vs_sh_get_fallback(svc, s, &iph->saddr, port); 335 else 336 dest = ip_vs_sh_get(svc, s, &iph->saddr, port); 337 338 if (!dest) { 339 ip_vs_scheduler_err(svc, "no destination available"); 340 return NULL; 341 } 342 343 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n", 344 IP_VS_DBG_ADDR(svc->af, &iph->saddr), 345 IP_VS_DBG_ADDR(dest->af, &dest->addr), 346 ntohs(dest->port)); 347 348 return dest; 349} 350 351 352/* 353 * IPVS SH Scheduler structure 354 */ 355static struct ip_vs_scheduler ip_vs_sh_scheduler = 356{ 357 .name = "sh", 358 .refcnt = ATOMIC_INIT(0), 359 .module = THIS_MODULE, 360 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list), 361 .init_service = ip_vs_sh_init_svc, 362 .done_service = ip_vs_sh_done_svc, 363 .add_dest = ip_vs_sh_dest_changed, 364 .del_dest = ip_vs_sh_dest_changed, 365 .upd_dest = ip_vs_sh_dest_changed, 366 .schedule = ip_vs_sh_schedule, 367}; 368 369 370static int __init ip_vs_sh_init(void) 371{ 372 return register_ip_vs_scheduler(&ip_vs_sh_scheduler); 373} 374 375 376static void __exit ip_vs_sh_cleanup(void) 377{ 378 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler); 379 synchronize_rcu(); 380} 381 382 383module_init(ip_vs_sh_init); 384module_exit(ip_vs_sh_cleanup); 385MODULE_LICENSE("GPL"); 386