net/netfilter/ipvs/ip_vs_dh.c

   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
  38 #define KMSG_COMPONENT "IPVS"
  39 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  40
  41 #include <linux/ip.h>
  42 #include <linux/slab.h>
  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 __rcu *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 struct ip_vs_dh_state {
  68         struct ip_vs_dh_bucket          buckets[IP_VS_DH_TAB_SIZE];
  69         struct rcu_head                 rcu_head;
  70 };
  71
  72 /*
  73  *      Returns hash value for IPVS DH entry
  74  */
  75 static inline unsigned int ip_vs_dh_hashkey(int af, const union nf_inet_addr *addr)
  76 {
  77         __be32 addr_fold = addr->ip;
  78
  79 #ifdef CONFIG_IP_VS_IPV6
  80         if (af == AF_INET6)
  81                 addr_fold = addr->ip6[0]^addr->ip6[1]^
  82                             addr->ip6[2]^addr->ip6[3];
  83 #endif
  84         return (ntohl(addr_fold)*2654435761UL) & IP_VS_DH_TAB_MASK;
  85 }
  86
  87
  88 /*
  89  *      Get ip_vs_dest associated with supplied parameters.
  90  */
  91 static inline struct ip_vs_dest *
  92 ip_vs_dh_get(int af, struct ip_vs_dh_state *s, const union nf_inet_addr *addr)
  93 {
  94         return rcu_dereference(s->buckets[ip_vs_dh_hashkey(af, addr)].dest);
  95 }
  96
  97
  98 /*
  99  *      Assign all the hash buckets of the specified table with the service.
 100  */
 101 static int
 102 ip_vs_dh_reassign(struct ip_vs_dh_state *s, struct ip_vs_service *svc)
 103 {
 104         int i;
 105         struct ip_vs_dh_bucket *b;
 106         struct list_head *p;
 107         struct ip_vs_dest *dest;
 108         bool empty;
 109
 110         b = &s->buckets[0];
 111         p = &svc->destinations;
 112         empty = list_empty(p);
 113         for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
 114                 dest = rcu_dereference_protected(b->dest, 1);
 115                 if (dest)
 116                         ip_vs_dest_put(dest);
 117                 if (empty)
 118                         RCU_INIT_POINTER(b->dest, NULL);
 119                 else {
 120                         if (p == &svc->destinations)
 121                                 p = p->next;
 122
 123                         dest = list_entry(p, struct ip_vs_dest, n_list);
 124                         ip_vs_dest_hold(dest);
 125                         RCU_INIT_POINTER(b->dest, dest);
 126
 127                         p = p->next;
 128                 }
 129                 b++;
 130         }
 131         return 0;
 132 }
 133
 134
 135 /*
 136  *      Flush all the hash buckets of the specified table.
 137  */
 138 static void ip_vs_dh_flush(struct ip_vs_dh_state *s)
 139 {
 140         int i;
 141         struct ip_vs_dh_bucket *b;
 142         struct ip_vs_dest *dest;
 143
 144         b = &s->buckets[0];
 145         for (i=0; i<IP_VS_DH_TAB_SIZE; i++) {
 146                 dest = rcu_dereference_protected(b->dest, 1);
 147                 if (dest) {
 148                         ip_vs_dest_put(dest);
 149                         RCU_INIT_POINTER(b->dest, NULL);
 150                 }
 151                 b++;
 152         }
 153 }
 154
 155
 156 static int ip_vs_dh_init_svc(struct ip_vs_service *svc)
 157 {
 158         struct ip_vs_dh_state *s;
 159
 160         /* allocate the DH table for this service */
 161         s = kzalloc(sizeof(struct ip_vs_dh_state), GFP_KERNEL);
 162         if (s == NULL)
 163                 return -ENOMEM;
 164
 165         svc->sched_data = s;
 166         IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) allocated for "
 167                   "current service\n",
 168                   sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
 169
 170         /* assign the hash buckets with current dests */
 171         ip_vs_dh_reassign(s, svc);
 172
 173         return 0;
 174 }
 175
 176
 177 static void ip_vs_dh_done_svc(struct ip_vs_service *svc)
 178 {
 179         struct ip_vs_dh_state *s = svc->sched_data;
 180
 181         /* got to clean up hash buckets here */
 182         ip_vs_dh_flush(s);
 183
 184         /* release the table itself */
 185         kfree_rcu(s, rcu_head);
 186         IP_VS_DBG(6, "DH hash table (memory=%Zdbytes) released\n",
 187                   sizeof(struct ip_vs_dh_bucket)*IP_VS_DH_TAB_SIZE);
 188 }
 189
 190
 191 static int ip_vs_dh_dest_changed(struct ip_vs_service *svc,
 192                                  struct ip_vs_dest *dest)
 193 {
 194         struct ip_vs_dh_state *s = svc->sched_data;
 195
 196         /* assign the hash buckets with the updated service */
 197         ip_vs_dh_reassign(s, svc);
 198
 199         return 0;
 200 }
 201
 202
 203 /*
 204  *      If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
 205  *      consider that the server is overloaded here.
 206  */
 207 static inline int is_overloaded(struct ip_vs_dest *dest)
 208 {
 209         return dest->flags & IP_VS_DEST_F_OVERLOAD;
 210 }
 211
 212
 213 /*
 214  *      Destination hashing scheduling
 215  */
 216 static struct ip_vs_dest *
 217 ip_vs_dh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
 218                   struct ip_vs_iphdr *iph)
 219 {
 220         struct ip_vs_dest *dest;
 221         struct ip_vs_dh_state *s;
 222
 223         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
 224
 225         s = (struct ip_vs_dh_state *) svc->sched_data;
 226         dest = ip_vs_dh_get(svc->af, s, &iph->daddr);
 227         if (!dest
 228             || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
 229             || atomic_read(&dest->weight) <= 0
 230             || is_overloaded(dest)) {
 231                 ip_vs_scheduler_err(svc, "no destination available");
 232                 return NULL;
 233         }
 234
 235         IP_VS_DBG_BUF(6, "DH: destination IP address %s --> server %s:%d\n",
 236                       IP_VS_DBG_ADDR(svc->af, &iph->daddr),
 237                       IP_VS_DBG_ADDR(dest->af, &dest->addr),
 238                       ntohs(dest->port));
 239
 240         return dest;
 241 }
 242
 243
 244 /*
 245  *      IPVS DH Scheduler structure
 246  */
 247 static struct ip_vs_scheduler ip_vs_dh_scheduler =
 248 {
 249         .name =                 "dh",
 250         .refcnt =               ATOMIC_INIT(0),
 251         .module =               THIS_MODULE,
 252         .n_list =               LIST_HEAD_INIT(ip_vs_dh_scheduler.n_list),
 253         .init_service =         ip_vs_dh_init_svc,
 254         .done_service =         ip_vs_dh_done_svc,
 255         .add_dest =             ip_vs_dh_dest_changed,
 256         .del_dest =             ip_vs_dh_dest_changed,
 257         .schedule =             ip_vs_dh_schedule,
 258 };
 259
 260
 261 static int __init ip_vs_dh_init(void)
 262 {
 263         return register_ip_vs_scheduler(&ip_vs_dh_scheduler);
 264 }
 265
 266
 267 static void __exit ip_vs_dh_cleanup(void)
 268 {
 269         unregister_ip_vs_scheduler(&ip_vs_dh_scheduler);
 270         synchronize_rcu();
 271 }
 272
 273
 274 module_init(ip_vs_dh_init);
 275 module_exit(ip_vs_dh_cleanup);
 276 MODULE_LICENSE("GPL");