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   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 <linux/config.h>
  16 #include <asm/system.h>
  17 #include <asm/uaccess.h>
  18 #include <linux/types.h>
  19 #include <linux/sched.h>
  20 #include <linux/errno.h>
  21 #include <linux/timer.h>
  22 #include <linux/mm.h>
  23 #include <linux/kernel.h>
  24 #include <linux/fcntl.h>
  25 #include <linux/stat.h>
  26 #include <linux/socket.h>
  27 #include <linux/in.h>
  28 #include <linux/inet.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/inetdevice.h>
  31 #include <linux/igmp.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/seq_file.h>
  34 #include <linux/module.h>
  35 #include <linux/mroute.h>
  36 #include <linux/init.h>
  37 #include <net/ip.h>
  38 #include <net/protocol.h>
  39 #include <linux/skbuff.h>
  40 #include <net/sock.h>
  41 #include <net/icmp.h>
  42 #include <net/udp.h>
  43 #include <net/raw.h>
  44 #include <linux/notifier.h>
  45 #include <linux/if_arp.h>
  46 #include <linux/netfilter_ipv4.h>
  47 #include <net/ipip.h>
  48 #include <net/checksum.h>
  49 #include <net/ip_fib.h>
  50 #include <net/ip_mp_alg.h>
  51
  52 #define MULTIPATH_STATE_SIZE 15
  53
  54 struct multipath_candidate {
  55         struct multipath_candidate      *next;
  56         int                             power;
  57         struct rtable                   *rt;
  58 };
  59
  60 struct multipath_dest {
  61         struct list_head        list;
  62
  63         const struct fib_nh     *nh_info;
  64         __u32                   netmask;
  65         __u32                   network;
  66         unsigned char           prefixlen;
  67
  68         struct rcu_head         rcu;
  69 };
  70
  71 struct multipath_bucket {
  72         struct list_head        head;
  73         spinlock_t              lock;
  74 };
  75
  76 struct multipath_route {
  77         struct list_head        list;
  78
  79         int                     oif;
  80         __u32                   gw;
  81         struct list_head        dests;
  82
  83         struct rcu_head         rcu;
  84 };
  85
  86 /* state: primarily weight per route information */
  87 static struct multipath_bucket state[MULTIPATH_STATE_SIZE];
  88
  89 /* interface to random number generation */
  90 static unsigned int RANDOM_SEED = 93186752;
  91
  92 static inline unsigned int random(unsigned int ubound)
  93 {
  94         static unsigned int a = 1588635695,
  95                 q = 2,
  96                 r = 1117695901;
  97         RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
  98         return RANDOM_SEED % ubound;
  99 }
 100
 101 static unsigned char __multipath_lookup_weight(const struct flowi *fl,
 102                                                const struct rtable *rt)
 103 {
 104         const int state_idx = rt->idev->dev->ifindex % MULTIPATH_STATE_SIZE;
 105         struct multipath_route *r;
 106         struct multipath_route *target_route = NULL;
 107         struct multipath_dest *d;
 108         int weight = 1;
 109
 110         /* lookup the weight information for a certain route */
 111         rcu_read_lock();
 112
 113         /* find state entry for gateway or add one if necessary */
 114         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
 115                 if (r->gw == rt->rt_gateway &&
 116                     r->oif == rt->idev->dev->ifindex) {
 117                         target_route = r;
 118                         break;
 119                 }
 120         }
 121
 122         if (!target_route) {
 123                 /* this should not happen... but we are prepared */
 124                 printk( KERN_CRIT"%s: missing state for gateway: %u and " \
 125                         "device %d\n", __FUNCTION__, rt->rt_gateway,
 126                         rt->idev->dev->ifindex);
 127                 goto out;
 128         }
 129
 130         /* find state entry for destination */
 131         list_for_each_entry_rcu(d, &target_route->dests, list) {
 132                 __u32 targetnetwork = fl->fl4_dst &
 133                         (0xFFFFFFFF >> (32 - d->prefixlen));
 134
 135                 if ((targetnetwork & d->netmask) == d->network) {
 136                         weight = d->nh_info->nh_weight;
 137                         goto out;
 138                 }
 139         }
 140
 141 out:
 142         rcu_read_unlock();
 143         return weight;
 144 }
 145
 146 static void wrandom_init_state(void)
 147 {
 148         int i;
 149
 150         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 151                 INIT_LIST_HEAD(&state[i].head);
 152                 spin_lock_init(&state[i].lock);
 153         }
 154 }
 155
 156 static void wrandom_select_route(const struct flowi *flp,
 157                                  struct rtable *first,
 158                                  struct rtable **rp)
 159 {
 160         struct rtable *rt;
 161         struct rtable *decision;
 162         struct multipath_candidate *first_mpc = NULL;
 163         struct multipath_candidate *mpc, *last_mpc = NULL;
 164         int power = 0;
 165         int last_power;
 166         int selector;
 167         const size_t size_mpc = sizeof(struct multipath_candidate);
 168
 169         /* collect all candidates and identify their weights */
 170         for (rt = rcu_dereference(first); rt;
 171              rt = rcu_dereference(rt->u.rt_next)) {
 172                 if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
 173                     multipath_comparekeys(&rt->fl, flp)) {
 174                         struct multipath_candidate* mpc =
 175                                 (struct multipath_candidate*)
 176                                 kmalloc(size_mpc, GFP_ATOMIC);
 177
 178                         if (!mpc)
 179                                 return;
 180
 181                         power += __multipath_lookup_weight(flp, rt) * 10000;
 182
 183                         mpc->power = power;
 184                         mpc->rt = rt;
 185                         mpc->next = NULL;
 186
 187                         if (!first_mpc)
 188                                 first_mpc = mpc;
 189                         else
 190                                 last_mpc->next = mpc;
 191
 192                         last_mpc = mpc;
 193                 }
 194         }
 195
 196         /* choose a weighted random candidate */
 197         decision = first;
 198         selector = random(power);
 199         last_power = 0;
 200
 201         /* select candidate, adjust GC data and cleanup local state */
 202         decision = first;
 203         last_mpc = NULL;
 204         for (mpc = first_mpc; mpc; mpc = mpc->next) {
 205                 mpc->rt->u.dst.lastuse = jiffies;
 206                 if (last_power <= selector && selector < mpc->power)
 207                         decision = mpc->rt;
 208
 209                 last_power = mpc->power;
 210                 if (last_mpc)
 211                         kfree(last_mpc);
 212
 213                 last_mpc = mpc;
 214         }
 215
 216         if (last_mpc) {
 217                 /* concurrent __multipath_flush may lead to !last_mpc */
 218                 kfree(last_mpc);
 219         }
 220
 221         decision->u.dst.__use++;
 222         *rp = decision;
 223 }
 224
 225 static void wrandom_set_nhinfo(__u32 network,
 226                                __u32 netmask,
 227                                unsigned char prefixlen,
 228                                const struct fib_nh *nh)
 229 {
 230         const int state_idx = nh->nh_oif % MULTIPATH_STATE_SIZE;
 231         struct multipath_route *r, *target_route = NULL;
 232         struct multipath_dest *d, *target_dest = NULL;
 233
 234         /* store the weight information for a certain route */
 235         spin_lock(&state[state_idx].lock);
 236
 237         /* find state entry for gateway or add one if necessary */
 238         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
 239                 if (r->gw == nh->nh_gw && r->oif == nh->nh_oif) {
 240                         target_route = r;
 241                         break;
 242                 }
 243         }
 244
 245         if (!target_route) {
 246                 const size_t size_rt = sizeof(struct multipath_route);
 247                 target_route = (struct multipath_route *)
 248                         kmalloc(size_rt, GFP_ATOMIC);
 249
 250                 target_route->gw = nh->nh_gw;
 251                 target_route->oif = nh->nh_oif;
 252                 memset(&target_route->rcu, 0, sizeof(struct rcu_head));
 253                 INIT_LIST_HEAD(&target_route->dests);
 254
 255                 list_add_rcu(&target_route->list, &state[state_idx].head);
 256         }
 257
 258         /* find state entry for destination or add one if necessary */
 259         list_for_each_entry_rcu(d, &target_route->dests, list) {
 260                 if (d->nh_info == nh) {
 261                         target_dest = d;
 262                         break;
 263                 }
 264         }
 265
 266         if (!target_dest) {
 267                 const size_t size_dst = sizeof(struct multipath_dest);
 268                 target_dest = (struct multipath_dest*)
 269                         kmalloc(size_dst, GFP_ATOMIC);
 270
 271                 target_dest->nh_info = nh;
 272                 target_dest->network = network;
 273                 target_dest->netmask = netmask;
 274                 target_dest->prefixlen = prefixlen;
 275                 memset(&target_dest->rcu, 0, sizeof(struct rcu_head));
 276
 277                 list_add_rcu(&target_dest->list, &target_route->dests);
 278         }
 279         /* else: we already stored this info for another destination =>
 280          * we are finished
 281          */
 282
 283         spin_unlock(&state[state_idx].lock);
 284 }
 285
 286 static void __multipath_free(struct rcu_head *head)
 287 {
 288         struct multipath_route *rt = container_of(head, struct multipath_route,
 289                                                   rcu);
 290         kfree(rt);
 291 }
 292
 293 static void __multipath_free_dst(struct rcu_head *head)
 294 {
 295         struct multipath_dest *dst = container_of(head,
 296                                                   struct multipath_dest,
 297                                                   rcu);
 298         kfree(dst);
 299 }
 300
 301 static void wrandom_flush(void)
 302 {
 303         int i;
 304
 305         /* defere delete to all entries */
 306         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 307                 struct multipath_route *r;
 308
 309                 spin_lock(&state[i].lock);
 310                 list_for_each_entry_rcu(r, &state[i].head, list) {
 311                         struct multipath_dest *d;
 312                         list_for_each_entry_rcu(d, &r->dests, list) {
 313                                 list_del_rcu(&d->list);
 314                                 call_rcu(&d->rcu,
 315                                          __multipath_free_dst);
 316                         }
 317                         list_del_rcu(&r->list);
 318                         call_rcu(&r->rcu,
 319                                  __multipath_free);
 320                 }
 321
 322                 spin_unlock(&state[i].lock);
 323         }
 324 }
 325
 326 static struct ip_mp_alg_ops wrandom_ops = {
 327         .mp_alg_select_route    =       wrandom_select_route,
 328         .mp_alg_flush           =       wrandom_flush,
 329         .mp_alg_set_nhinfo      =       wrandom_set_nhinfo,
 330 };
 331
 332 static int __init wrandom_init(void)
 333 {
 334         wrandom_init_state();
 335
 336         return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
 337 }
 338
 339 static void __exit wrandom_exit(void)
 340 {
 341         multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
 342 }
 343
 344 module_init(wrandom_init);
 345 module_exit(wrandom_exit);
 346 MODULE_LICENSE("GPL");