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