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