1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * IPVS: Source Hashing scheduling module 4 * 5 * Authors: Wensong Zhang <wensong@gnuchina.org> 6 * 7 * Changes: 8 */ 9 10 /* 11 * The sh algorithm is to select server by the hash key of source IP 12 * address. The pseudo code is as follows: 13 * 14 * n <- servernode[src_ip]; 15 * if (n is dead) OR 16 * (n is overloaded) or (n.weight <= 0) then 17 * return NULL; 18 * 19 * return n; 20 * 21 * Notes that servernode is a 256-bucket hash table that maps the hash 22 * index derived from packet source IP address to the current server 23 * array. If the sh scheduler is used in cache cluster, it is good to 24 * combine it with cache_bypass feature. When the statically assigned 25 * server is dead or overloaded, the load balancer can bypass the cache 26 * server and send requests to the original server directly. 27 * 28 * The weight destination attribute can be used to control the 29 * distribution of connections to the destinations in servernode. The 30 * greater the weight, the more connections the destination 31 * will receive. 32 * 33 */ 34 35 #define KMSG_COMPONENT "IPVS" 36 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 37 38 #include <linux/ip.h> 39 #include <linux/slab.h> 40 #include <linux/module.h> 41 #include <linux/kernel.h> 42 #include <linux/skbuff.h> 43 44 #include <net/ip_vs.h> 45 46 #include <net/tcp.h> 47 #include <linux/udp.h> 48 #include <linux/sctp.h> 49 50 51 /* 52 * IPVS SH bucket 53 */ 54 struct ip_vs_sh_bucket { 55 struct ip_vs_dest __rcu *dest; /* real server (cache) */ 56 }; 57 58 /* 59 * for IPVS SH entry hash table 60 */ 61 #ifndef CONFIG_IP_VS_SH_TAB_BITS 62 #define CONFIG_IP_VS_SH_TAB_BITS 8 63 #endif 64 #define IP_VS_SH_TAB_BITS CONFIG_IP_VS_SH_TAB_BITS 65 #define IP_VS_SH_TAB_SIZE (1 << IP_VS_SH_TAB_BITS) 66 #define IP_VS_SH_TAB_MASK (IP_VS_SH_TAB_SIZE - 1) 67 68 struct ip_vs_sh_state { 69 struct rcu_head rcu_head; 70 struct ip_vs_sh_bucket buckets[IP_VS_SH_TAB_SIZE]; 71 }; 72 73 /* Helper function to determine if server is unavailable */ 74 static inline bool is_unavailable(struct ip_vs_dest *dest) 75 { 76 return atomic_read(&dest->weight) <= 0 || 77 dest->flags & IP_VS_DEST_F_OVERLOAD; 78 } 79 80 /* 81 * Returns hash value for IPVS SH entry 82 */ 83 static inline unsigned int 84 ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr, 85 __be16 port, unsigned int offset) 86 { 87 __be32 addr_fold = addr->ip; 88 89 #ifdef CONFIG_IP_VS_IPV6 90 if (af == AF_INET6) 91 addr_fold = addr->ip6[0]^addr->ip6[1]^ 92 addr->ip6[2]^addr->ip6[3]; 93 #endif 94 return (offset + hash_32(ntohs(port) + ntohl(addr_fold), 95 IP_VS_SH_TAB_BITS)) & 96 IP_VS_SH_TAB_MASK; 97 } 98 99 100 /* 101 * Get ip_vs_dest associated with supplied parameters. 102 */ 103 static inline struct ip_vs_dest * 104 ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s, 105 const union nf_inet_addr *addr, __be16 port) 106 { 107 unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0); 108 struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest); 109 110 return (!dest || is_unavailable(dest)) ? NULL : dest; 111 } 112 113 114 /* As ip_vs_sh_get, but with fallback if selected server is unavailable 115 * 116 * The fallback strategy loops around the table starting from a "random" 117 * point (in fact, it is chosen to be the original hash value to make the 118 * algorithm deterministic) to find a new server. 119 */ 120 static inline struct ip_vs_dest * 121 ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s, 122 const union nf_inet_addr *addr, __be16 port) 123 { 124 unsigned int offset, roffset; 125 unsigned int hash, ihash; 126 struct ip_vs_dest *dest; 127 128 /* first try the dest it's supposed to go to */ 129 ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0); 130 dest = rcu_dereference(s->buckets[ihash].dest); 131 if (!dest) 132 return NULL; 133 if (!is_unavailable(dest)) 134 return dest; 135 136 IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting", 137 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port)); 138 139 /* if the original dest is unavailable, loop around the table 140 * starting from ihash to find a new dest 141 */ 142 for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) { 143 roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE; 144 hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset); 145 dest = rcu_dereference(s->buckets[hash].dest); 146 if (!dest) 147 break; 148 if (!is_unavailable(dest)) 149 return dest; 150 IP_VS_DBG_BUF(6, "SH: selected unavailable " 151 "server %s:%d (offset %d), reselecting", 152 IP_VS_DBG_ADDR(dest->af, &dest->addr), 153 ntohs(dest->port), roffset); 154 } 155 156 return NULL; 157 } 158 159 /* 160 * Assign all the hash buckets of the specified table with the service. 161 */ 162 static int 163 ip_vs_sh_reassign(struct ip_vs_sh_state *s, struct ip_vs_service *svc) 164 { 165 int i; 166 struct ip_vs_sh_bucket *b; 167 struct list_head *p; 168 struct ip_vs_dest *dest; 169 int d_count; 170 bool empty; 171 172 b = &s->buckets[0]; 173 p = &svc->destinations; 174 empty = list_empty(p); 175 d_count = 0; 176 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 177 dest = rcu_dereference_protected(b->dest, 1); 178 if (dest) 179 ip_vs_dest_put(dest); 180 if (empty) 181 RCU_INIT_POINTER(b->dest, NULL); 182 else { 183 if (p == &svc->destinations) 184 p = p->next; 185 186 dest = list_entry(p, struct ip_vs_dest, n_list); 187 ip_vs_dest_hold(dest); 188 RCU_INIT_POINTER(b->dest, dest); 189 190 IP_VS_DBG_BUF(6, "assigned i: %d dest: %s weight: %d\n", 191 i, IP_VS_DBG_ADDR(dest->af, &dest->addr), 192 atomic_read(&dest->weight)); 193 194 /* Don't move to next dest until filling weight */ 195 if (++d_count >= atomic_read(&dest->weight)) { 196 p = p->next; 197 d_count = 0; 198 } 199 200 } 201 b++; 202 } 203 return 0; 204 } 205 206 207 /* 208 * Flush all the hash buckets of the specified table. 209 */ 210 static void ip_vs_sh_flush(struct ip_vs_sh_state *s) 211 { 212 int i; 213 struct ip_vs_sh_bucket *b; 214 struct ip_vs_dest *dest; 215 216 b = &s->buckets[0]; 217 for (i=0; i<IP_VS_SH_TAB_SIZE; i++) { 218 dest = rcu_dereference_protected(b->dest, 1); 219 if (dest) { 220 ip_vs_dest_put(dest); 221 RCU_INIT_POINTER(b->dest, NULL); 222 } 223 b++; 224 } 225 } 226 227 228 static int ip_vs_sh_init_svc(struct ip_vs_service *svc) 229 { 230 struct ip_vs_sh_state *s; 231 232 /* allocate the SH table for this service */ 233 s = kzalloc(sizeof(struct ip_vs_sh_state), GFP_KERNEL); 234 if (s == NULL) 235 return -ENOMEM; 236 237 svc->sched_data = s; 238 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) allocated for " 239 "current service\n", 240 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 241 242 /* assign the hash buckets with current dests */ 243 ip_vs_sh_reassign(s, svc); 244 245 return 0; 246 } 247 248 249 static void ip_vs_sh_done_svc(struct ip_vs_service *svc) 250 { 251 struct ip_vs_sh_state *s = svc->sched_data; 252 253 /* got to clean up hash buckets here */ 254 ip_vs_sh_flush(s); 255 256 /* release the table itself */ 257 kfree_rcu(s, rcu_head); 258 IP_VS_DBG(6, "SH hash table (memory=%zdbytes) released\n", 259 sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE); 260 } 261 262 263 static int ip_vs_sh_dest_changed(struct ip_vs_service *svc, 264 struct ip_vs_dest *dest) 265 { 266 struct ip_vs_sh_state *s = svc->sched_data; 267 268 /* assign the hash buckets with the updated service */ 269 ip_vs_sh_reassign(s, svc); 270 271 return 0; 272 } 273 274 275 /* Helper function to get port number */ 276 static inline __be16 277 ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph) 278 { 279 __be16 _ports[2], *ports; 280 281 /* At this point we know that we have a valid packet of some kind. 282 * Because ICMP packets are only guaranteed to have the first 8 283 * bytes, let's just grab the ports. Fortunately they're in the 284 * same position for all three of the protocols we care about. 285 */ 286 switch (iph->protocol) { 287 case IPPROTO_TCP: 288 case IPPROTO_UDP: 289 case IPPROTO_SCTP: 290 ports = skb_header_pointer(skb, iph->len, sizeof(_ports), 291 &_ports); 292 if (unlikely(!ports)) 293 return 0; 294 295 if (likely(!ip_vs_iph_inverse(iph))) 296 return ports[0]; 297 else 298 return ports[1]; 299 default: 300 return 0; 301 } 302 } 303 304 305 /* 306 * Source Hashing scheduling 307 */ 308 static struct ip_vs_dest * 309 ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb, 310 struct ip_vs_iphdr *iph) 311 { 312 struct ip_vs_dest *dest; 313 struct ip_vs_sh_state *s; 314 __be16 port = 0; 315 const union nf_inet_addr *hash_addr; 316 317 hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr; 318 319 IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n"); 320 321 if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT) 322 port = ip_vs_sh_get_port(skb, iph); 323 324 s = (struct ip_vs_sh_state *) svc->sched_data; 325 326 if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK) 327 dest = ip_vs_sh_get_fallback(svc, s, hash_addr, port); 328 else 329 dest = ip_vs_sh_get(svc, s, hash_addr, port); 330 331 if (!dest) { 332 ip_vs_scheduler_err(svc, "no destination available"); 333 return NULL; 334 } 335 336 IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n", 337 IP_VS_DBG_ADDR(svc->af, hash_addr), 338 IP_VS_DBG_ADDR(dest->af, &dest->addr), 339 ntohs(dest->port)); 340 341 return dest; 342 } 343 344 345 /* 346 * IPVS SH Scheduler structure 347 */ 348 static struct ip_vs_scheduler ip_vs_sh_scheduler = 349 { 350 .name = "sh", 351 .refcnt = ATOMIC_INIT(0), 352 .module = THIS_MODULE, 353 .n_list = LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list), 354 .init_service = ip_vs_sh_init_svc, 355 .done_service = ip_vs_sh_done_svc, 356 .add_dest = ip_vs_sh_dest_changed, 357 .del_dest = ip_vs_sh_dest_changed, 358 .upd_dest = ip_vs_sh_dest_changed, 359 .schedule = ip_vs_sh_schedule, 360 }; 361 362 363 static int __init ip_vs_sh_init(void) 364 { 365 return register_ip_vs_scheduler(&ip_vs_sh_scheduler); 366 } 367 368 369 static void __exit ip_vs_sh_cleanup(void) 370 { 371 unregister_ip_vs_scheduler(&ip_vs_sh_scheduler); 372 synchronize_rcu(); 373 } 374 375 376 module_init(ip_vs_sh_init); 377 module_exit(ip_vs_sh_cleanup); 378 MODULE_LICENSE("GPL"); 379