kernel/2.6.29.6-aldebaran-rt/net/netfilter/ipvs/ip_vs_sh.c

   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  */
  34
  35 #include <linux/ip.h>
  36 #include <linux/module.h>
  37 #include <linux/kernel.h>
  38 #include <linux/skbuff.h>
  39
  40 #include <net/ip_vs.h>
  41
  42
  43 /*
  44  *      IPVS SH bucket
  45  */
  46 struct ip_vs_sh_bucket {
  47         struct ip_vs_dest       *dest;          /* real server (cache) */
  48 };
  49
  50 /*
  51  *     for IPVS SH entry hash table
  52  */
  53 #ifndef CONFIG_IP_VS_SH_TAB_BITS
  54 #define CONFIG_IP_VS_SH_TAB_BITS        8
  55 #endif
  56 #define IP_VS_SH_TAB_BITS               CONFIG_IP_VS_SH_TAB_BITS
  57 #define IP_VS_SH_TAB_SIZE               (1 << IP_VS_SH_TAB_BITS)
  58 #define IP_VS_SH_TAB_MASK               (IP_VS_SH_TAB_SIZE - 1)
  59
  60
  61 /*
  62  *      Returns hash value for IPVS SH entry
  63  */
  64 static inline unsigned ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr)
  65 {
  66         __be32 addr_fold = addr->ip;
  67
  68 #ifdef CONFIG_IP_VS_IPV6
  69         if (af == AF_INET6)
  70                 addr_fold = addr->ip6[0]^addr->ip6[1]^
  71                             addr->ip6[2]^addr->ip6[3];
  72 #endif
  73         return (ntohl(addr_fold)*2654435761UL) & IP_VS_SH_TAB_MASK;
  74 }
  75
  76
  77 /*
  78  *      Get ip_vs_dest associated with supplied parameters.
  79  */
  80 static inline struct ip_vs_dest *
  81 ip_vs_sh_get(int af, struct ip_vs_sh_bucket *tbl,
  82              const union nf_inet_addr *addr)
  83 {
  84         return (tbl[ip_vs_sh_hashkey(af, addr)]).dest;
  85 }
  86
  87
  88 /*
  89  *      Assign all the hash buckets of the specified table with the service.
  90  */
  91 static int
  92 ip_vs_sh_assign(struct ip_vs_sh_bucket *tbl, struct ip_vs_service *svc)
  93 {
  94         int i;
  95         struct ip_vs_sh_bucket *b;
  96         struct list_head *p;
  97         struct ip_vs_dest *dest;
  98
  99         b = tbl;
 100         p = &svc->destinations;
 101         for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
 102                 if (list_empty(p)) {
 103                         b->dest = NULL;
 104                 } else {
 105                         if (p == &svc->destinations)
 106                                 p = p->next;
 107
 108                         dest = list_entry(p, struct ip_vs_dest, n_list);
 109                         atomic_inc(&dest->refcnt);
 110                         b->dest = dest;
 111
 112                         p = p->next;
 113                 }
 114                 b++;
 115         }
 116         return 0;
 117 }
 118
 119
 120 /*
 121  *      Flush all the hash buckets of the specified table.
 122  */
 123 static void ip_vs_sh_flush(struct ip_vs_sh_bucket *tbl)
 124 {
 125         int i;
 126         struct ip_vs_sh_bucket *b;
 127
 128         b = tbl;
 129         for (i=0; i<IP_VS_SH_TAB_SIZE; i++) {
 130                 if (b->dest) {
 131                         atomic_dec(&b->dest->refcnt);
 132                         b->dest = NULL;
 133                 }
 134                 b++;
 135         }
 136 }
 137
 138
 139 static int ip_vs_sh_init_svc(struct ip_vs_service *svc)
 140 {
 141         struct ip_vs_sh_bucket *tbl;
 142
 143         /* allocate the SH table for this service */
 144         tbl = kmalloc(sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE,
 145                       GFP_ATOMIC);
 146         if (tbl == NULL) {
 147                 IP_VS_ERR("ip_vs_sh_init_svc(): no memory\n");
 148                 return -ENOMEM;
 149         }
 150         svc->sched_data = tbl;
 151         IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) allocated for "
 152                   "current service\n",
 153                   sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
 154
 155         /* assign the hash buckets with the updated service */
 156         ip_vs_sh_assign(tbl, svc);
 157
 158         return 0;
 159 }
 160
 161
 162 static int ip_vs_sh_done_svc(struct ip_vs_service *svc)
 163 {
 164         struct ip_vs_sh_bucket *tbl = svc->sched_data;
 165
 166         /* got to clean up hash buckets here */
 167         ip_vs_sh_flush(tbl);
 168
 169         /* release the table itself */
 170         kfree(svc->sched_data);
 171         IP_VS_DBG(6, "SH hash table (memory=%Zdbytes) released\n",
 172                   sizeof(struct ip_vs_sh_bucket)*IP_VS_SH_TAB_SIZE);
 173
 174         return 0;
 175 }
 176
 177
 178 static int ip_vs_sh_update_svc(struct ip_vs_service *svc)
 179 {
 180         struct ip_vs_sh_bucket *tbl = svc->sched_data;
 181
 182         /* got to clean up hash buckets here */
 183         ip_vs_sh_flush(tbl);
 184
 185         /* assign the hash buckets with the updated service */
 186         ip_vs_sh_assign(tbl, svc);
 187
 188         return 0;
 189 }
 190
 191
 192 /*
 193  *      If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
 194  *      consider that the server is overloaded here.
 195  */
 196 static inline int is_overloaded(struct ip_vs_dest *dest)
 197 {
 198         return dest->flags & IP_VS_DEST_F_OVERLOAD;
 199 }
 200
 201
 202 /*
 203  *      Source Hashing scheduling
 204  */
 205 static struct ip_vs_dest *
 206 ip_vs_sh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
 207 {
 208         struct ip_vs_dest *dest;
 209         struct ip_vs_sh_bucket *tbl;
 210         struct ip_vs_iphdr iph;
 211
 212         ip_vs_fill_iphdr(svc->af, skb_network_header(skb), &iph);
 213
 214         IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
 215
 216         tbl = (struct ip_vs_sh_bucket *)svc->sched_data;
 217         dest = ip_vs_sh_get(svc->af, tbl, &iph.saddr);
 218         if (!dest
 219             || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
 220             || atomic_read(&dest->weight) <= 0
 221             || is_overloaded(dest)) {
 222                 IP_VS_ERR_RL("SH: no destination available\n");
 223                 return NULL;
 224         }
 225
 226         IP_VS_DBG_BUF(6, "SH: source IP address %s --> server %s:%d\n",
 227                       IP_VS_DBG_ADDR(svc->af, &iph.saddr),
 228                       IP_VS_DBG_ADDR(svc->af, &dest->addr),
 229                       ntohs(dest->port));
 230
 231         return dest;
 232 }
 233
 234
 235 /*
 236  *      IPVS SH Scheduler structure
 237  */
 238 static struct ip_vs_scheduler ip_vs_sh_scheduler =
 239 {
 240         .name =                 "sh",
 241         .refcnt =               ATOMIC_INIT(0),
 242         .module =               THIS_MODULE,
 243         .n_list  =              LIST_HEAD_INIT(ip_vs_sh_scheduler.n_list),
 244         .init_service =         ip_vs_sh_init_svc,
 245         .done_service =         ip_vs_sh_done_svc,
 246         .update_service =       ip_vs_sh_update_svc,
 247         .schedule =             ip_vs_sh_schedule,
 248 };
 249
 250
 251 static int __init ip_vs_sh_init(void)
 252 {
 253         return register_ip_vs_scheduler(&ip_vs_sh_scheduler);
 254 }
 255
 256
 257 static void __exit ip_vs_sh_cleanup(void)
 258 {
 259         unregister_ip_vs_scheduler(&ip_vs_sh_scheduler);
 260 }
 261
 262
 263 module_init(ip_vs_sh_init);
 264 module_exit(ip_vs_sh_cleanup);
 265 MODULE_LICENSE("GPL");