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