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