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