net/ipv4/multipath_wrandom.c

   1 /*
   2  *              Weighted random policy for multipath.
   3  *
   4  *
   5  * Version:     $Id: multipath_wrandom.c,v 1.1.2.3 2004/09/22 07:51:40 elueck Exp $
   6  *
   7  * Authors:     Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.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
  15 #include <asm/system.h>
  16 #include <asm/uaccess.h>
  17 #include <linux/types.h>
  18 #include <linux/sched.h>
  19 #include <linux/errno.h>
  20 #include <linux/timer.h>
  21 #include <linux/mm.h>
  22 #include <linux/kernel.h>
  23 #include <linux/fcntl.h>
  24 #include <linux/stat.h>
  25 #include <linux/socket.h>
  26 #include <linux/in.h>
  27 #include <linux/inet.h>
  28 #include <linux/netdevice.h>
  29 #include <linux/inetdevice.h>
  30 #include <linux/igmp.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/seq_file.h>
  33 #include <linux/module.h>
  34 #include <linux/mroute.h>
  35 #include <linux/init.h>
  36 #include <net/ip.h>
  37 #include <net/protocol.h>
  38 #include <linux/skbuff.h>
  39 #include <net/sock.h>
  40 #include <net/icmp.h>
  41 #include <net/udp.h>
  42 #include <net/raw.h>
  43 #include <linux/notifier.h>
  44 #include <linux/if_arp.h>
  45 #include <linux/netfilter_ipv4.h>
  46 #include <net/ipip.h>
  47 #include <net/checksum.h>
  48 #include <net/ip_fib.h>
  49 #include <net/ip_mp_alg.h>
  50
  51 #define MULTIPATH_STATE_SIZE 15
  52
  53 struct multipath_candidate {
  54         struct multipath_candidate      *next;
  55         int                             power;
  56         struct rtable                   *rt;
  57 };
  58
  59 struct multipath_dest {
  60         struct list_head        list;
  61
  62         const struct fib_nh     *nh_info;
  63         __be32                  netmask;
  64         __be32                  network;
  65         unsigned char           prefixlen;
  66
  67         struct rcu_head         rcu;
  68 };
  69
  70 struct multipath_bucket {
  71         struct list_head        head;
  72         spinlock_t              lock;
  73 };
  74
  75 struct multipath_route {
  76         struct list_head        list;
  77
  78         int                     oif;
  79         __be32                  gw;
  80         struct list_head        dests;
  81
  82         struct rcu_head         rcu;
  83 };
  84
  85 /* state: primarily weight per route information */
  86 static struct multipath_bucket state[MULTIPATH_STATE_SIZE];
  87
  88 /* interface to random number generation */
  89 static unsigned int RANDOM_SEED = 93186752;
  90
  91 static inline unsigned int random(unsigned int ubound)
  92 {
  93         static unsigned int a = 1588635695,
  94                 q = 2,
  95                 r = 1117695901;
  96         RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
  97         return RANDOM_SEED % ubound;
  98 }
  99
 100 static unsigned char __multipath_lookup_weight(const struct flowi *fl,
 101                                                const struct rtable *rt)
 102 {
 103         const int state_idx = rt->idev->dev->ifindex % MULTIPATH_STATE_SIZE;
 104         struct multipath_route *r;
 105         struct multipath_route *target_route = NULL;
 106         struct multipath_dest *d;
 107         int weight = 1;
 108
 109         /* lookup the weight information for a certain route */
 110         rcu_read_lock();
 111
 112         /* find state entry for gateway or add one if necessary */
 113         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
 114                 if (r->gw == rt->rt_gateway &&
 115                     r->oif == rt->idev->dev->ifindex) {
 116                         target_route = r;
 117                         break;
 118                 }
 119         }
 120
 121         if (!target_route) {
 122                 /* this should not happen... but we are prepared */
 123                 printk( KERN_CRIT"%s: missing state for gateway: %u and " \
 124                         "device %d\n", __FUNCTION__, rt->rt_gateway,
 125                         rt->idev->dev->ifindex);
 126                 goto out;
 127         }
 128
 129         /* find state entry for destination */
 130         list_for_each_entry_rcu(d, &target_route->dests, list) {
 131                 __be32 targetnetwork = fl->fl4_dst &
 132                         inet_make_mask(d->prefixlen);
 133
 134                 if ((targetnetwork & d->netmask) == d->network) {
 135                         weight = d->nh_info->nh_weight;
 136                         goto out;
 137                 }
 138         }
 139
 140 out:
 141         rcu_read_unlock();
 142         return weight;
 143 }
 144
 145 static void wrandom_init_state(void)
 146 {
 147         int i;
 148
 149         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 150                 INIT_LIST_HEAD(&state[i].head);
 151                 spin_lock_init(&state[i].lock);
 152         }
 153 }
 154
 155 static void wrandom_select_route(const struct flowi *flp,
 156                                  struct rtable *first,
 157                                  struct rtable **rp)
 158 {
 159         struct rtable *rt;
 160         struct rtable *decision;
 161         struct multipath_candidate *first_mpc = NULL;
 162         struct multipath_candidate *mpc, *last_mpc = NULL;
 163         int power = 0;
 164         int last_power;
 165         int selector;
 166         const size_t size_mpc = sizeof(struct multipath_candidate);
 167
 168         /* collect all candidates and identify their weights */
 169         for (rt = rcu_dereference(first); rt;
 170              rt = rcu_dereference(rt->u.rt_next)) {
 171                 if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
 172                     multipath_comparekeys(&rt->fl, flp)) {
 173                         struct multipath_candidate* mpc =
 174                                 (struct multipath_candidate*)
 175                                 kmalloc(size_mpc, GFP_ATOMIC);
 176
 177                         if (!mpc)
 178                                 return;
 179
 180                         power += __multipath_lookup_weight(flp, rt) * 10000;
 181
 182                         mpc->power = power;
 183                         mpc->rt = rt;
 184                         mpc->next = NULL;
 185
 186                         if (!first_mpc)
 187                                 first_mpc = mpc;
 188                         else
 189                                 last_mpc->next = mpc;
 190
 191                         last_mpc = mpc;
 192                 }
 193         }
 194
 195         /* choose a weighted random candidate */
 196         decision = first;
 197         selector = random(power);
 198         last_power = 0;
 199
 200         /* select candidate, adjust GC data and cleanup local state */
 201         decision = first;
 202         last_mpc = NULL;
 203         for (mpc = first_mpc; mpc; mpc = mpc->next) {
 204                 mpc->rt->u.dst.lastuse = jiffies;
 205                 if (last_power <= selector && selector < mpc->power)
 206                         decision = mpc->rt;
 207
 208                 last_power = mpc->power;
 209                 kfree(last_mpc);
 210                 last_mpc = mpc;
 211         }
 212
 213         /* concurrent __multipath_flush may lead to !last_mpc */
 214         kfree(last_mpc);
 215
 216         decision->u.dst.__use++;
 217         *rp = decision;
 218 }
 219
 220 static void wrandom_set_nhinfo(__be32 network,
 221                                __be32 netmask,
 222                                unsigned char prefixlen,
 223                                const struct fib_nh *nh)
 224 {
 225         const int state_idx = nh->nh_oif % MULTIPATH_STATE_SIZE;
 226         struct multipath_route *r, *target_route = NULL;
 227         struct multipath_dest *d, *target_dest = NULL;
 228
 229         /* store the weight information for a certain route */
 230         spin_lock_bh(&state[state_idx].lock);
 231
 232         /* find state entry for gateway or add one if necessary */
 233         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
 234                 if (r->gw == nh->nh_gw && r->oif == nh->nh_oif) {
 235                         target_route = r;
 236                         break;
 237                 }
 238         }
 239
 240         if (!target_route) {
 241                 const size_t size_rt = sizeof(struct multipath_route);
 242                 target_route = (struct multipath_route *)
 243                         kmalloc(size_rt, GFP_ATOMIC);
 244
 245                 target_route->gw = nh->nh_gw;
 246                 target_route->oif = nh->nh_oif;
 247                 memset(&target_route->rcu, 0, sizeof(struct rcu_head));
 248                 INIT_LIST_HEAD(&target_route->dests);
 249
 250                 list_add_rcu(&target_route->list, &state[state_idx].head);
 251         }
 252
 253         /* find state entry for destination or add one if necessary */
 254         list_for_each_entry_rcu(d, &target_route->dests, list) {
 255                 if (d->nh_info == nh) {
 256                         target_dest = d;
 257                         break;
 258                 }
 259         }
 260
 261         if (!target_dest) {
 262                 const size_t size_dst = sizeof(struct multipath_dest);
 263                 target_dest = (struct multipath_dest*)
 264                         kmalloc(size_dst, GFP_ATOMIC);
 265
 266                 target_dest->nh_info = nh;
 267                 target_dest->network = network;
 268                 target_dest->netmask = netmask;
 269                 target_dest->prefixlen = prefixlen;
 270                 memset(&target_dest->rcu, 0, sizeof(struct rcu_head));
 271
 272                 list_add_rcu(&target_dest->list, &target_route->dests);
 273         }
 274         /* else: we already stored this info for another destination =>
 275          * we are finished
 276          */
 277
 278         spin_unlock_bh(&state[state_idx].lock);
 279 }
 280
 281 static void __multipath_free(struct rcu_head *head)
 282 {
 283         struct multipath_route *rt = container_of(head, struct multipath_route,
 284                                                   rcu);
 285         kfree(rt);
 286 }
 287
 288 static void __multipath_free_dst(struct rcu_head *head)
 289 {
 290         struct multipath_dest *dst = container_of(head,
 291                                                   struct multipath_dest,
 292                                                   rcu);
 293         kfree(dst);
 294 }
 295
 296 static void wrandom_flush(void)
 297 {
 298         int i;
 299
 300         /* defere delete to all entries */
 301         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 302                 struct multipath_route *r;
 303
 304                 spin_lock_bh(&state[i].lock);
 305                 list_for_each_entry_rcu(r, &state[i].head, list) {
 306                         struct multipath_dest *d;
 307                         list_for_each_entry_rcu(d, &r->dests, list) {
 308                                 list_del_rcu(&d->list);
 309                                 call_rcu(&d->rcu,
 310                                          __multipath_free_dst);
 311                         }
 312                         list_del_rcu(&r->list);
 313                         call_rcu(&r->rcu,
 314                                  __multipath_free);
 315                 }
 316
 317                 spin_unlock_bh(&state[i].lock);
 318         }
 319 }
 320
 321 static struct ip_mp_alg_ops wrandom_ops = {
 322         .mp_alg_select_route    =       wrandom_select_route,
 323         .mp_alg_flush           =       wrandom_flush,
 324         .mp_alg_set_nhinfo      =       wrandom_set_nhinfo,
 325 };
 326
 327 static int __init wrandom_init(void)
 328 {
 329         wrandom_init_state();
 330
 331         return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
 332 }
 333
 334 static void __exit wrandom_exit(void)
 335 {
 336         multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
 337 }
 338
 339 module_init(wrandom_init);
 340 module_exit(wrandom_exit);
 341 MODULE_LICENSE("GPL");