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 <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                 kfree(last_mpc);
 211                 last_mpc = mpc;
 212         }
 213
 214         /* concurrent __multipath_flush may lead to !last_mpc */
 215         kfree(last_mpc);
 216
 217         decision->u.dst.__use++;
 218         *rp = decision;
 219 }
 220
 221 static void wrandom_set_nhinfo(__u32 network,
 222                                __u32 netmask,
 223                                unsigned char prefixlen,
 224                                const struct fib_nh *nh)
 225 {
 226         const int state_idx = nh->nh_oif % MULTIPATH_STATE_SIZE;
 227         struct multipath_route *r, *target_route = NULL;
 228         struct multipath_dest *d, *target_dest = NULL;
 229
 230         /* store the weight information for a certain route */
 231         spin_lock_bh(&state[state_idx].lock);
 232
 233         /* find state entry for gateway or add one if necessary */
 234         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
 235                 if (r->gw == nh->nh_gw && r->oif == nh->nh_oif) {
 236                         target_route = r;
 237                         break;
 238                 }
 239         }
 240
 241         if (!target_route) {
 242                 const size_t size_rt = sizeof(struct multipath_route);
 243                 target_route = (struct multipath_route *)
 244                         kmalloc(size_rt, GFP_ATOMIC);
 245
 246                 target_route->gw = nh->nh_gw;
 247                 target_route->oif = nh->nh_oif;
 248                 memset(&target_route->rcu, 0, sizeof(struct rcu_head));
 249                 INIT_LIST_HEAD(&target_route->dests);
 250
 251                 list_add_rcu(&target_route->list, &state[state_idx].head);
 252         }
 253
 254         /* find state entry for destination or add one if necessary */
 255         list_for_each_entry_rcu(d, &target_route->dests, list) {
 256                 if (d->nh_info == nh) {
 257                         target_dest = d;
 258                         break;
 259                 }
 260         }
 261
 262         if (!target_dest) {
 263                 const size_t size_dst = sizeof(struct multipath_dest);
 264                 target_dest = (struct multipath_dest*)
 265                         kmalloc(size_dst, GFP_ATOMIC);
 266
 267                 target_dest->nh_info = nh;
 268                 target_dest->network = network;
 269                 target_dest->netmask = netmask;
 270                 target_dest->prefixlen = prefixlen;
 271                 memset(&target_dest->rcu, 0, sizeof(struct rcu_head));
 272
 273                 list_add_rcu(&target_dest->list, &target_route->dests);
 274         }
 275         /* else: we already stored this info for another destination =>
 276          * we are finished
 277          */
 278
 279         spin_unlock_bh(&state[state_idx].lock);
 280 }
 281
 282 static void __multipath_free(struct rcu_head *head)
 283 {
 284         struct multipath_route *rt = container_of(head, struct multipath_route,
 285                                                   rcu);
 286         kfree(rt);
 287 }
 288
 289 static void __multipath_free_dst(struct rcu_head *head)
 290 {
 291         struct multipath_dest *dst = container_of(head,
 292                                                   struct multipath_dest,
 293                                                   rcu);
 294         kfree(dst);
 295 }
 296
 297 static void wrandom_flush(void)
 298 {
 299         int i;
 300
 301         /* defere delete to all entries */
 302         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
 303                 struct multipath_route *r;
 304
 305                 spin_lock_bh(&state[i].lock);
 306                 list_for_each_entry_rcu(r, &state[i].head, list) {
 307                         struct multipath_dest *d;
 308                         list_for_each_entry_rcu(d, &r->dests, list) {
 309                                 list_del_rcu(&d->list);
 310                                 call_rcu(&d->rcu,
 311                                          __multipath_free_dst);
 312                         }
 313                         list_del_rcu(&r->list);
 314                         call_rcu(&r->rcu,
 315                                  __multipath_free);
 316                 }
 317
 318                 spin_unlock_bh(&state[i].lock);
 319         }
 320 }
 321
 322 static struct ip_mp_alg_ops wrandom_ops = {
 323         .mp_alg_select_route    =       wrandom_select_route,
 324         .mp_alg_flush           =       wrandom_flush,
 325         .mp_alg_set_nhinfo      =       wrandom_set_nhinfo,
 326 };
 327
 328 static int __init wrandom_init(void)
 329 {
 330         wrandom_init_state();
 331
 332         return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
 333 }
 334
 335 static void __exit wrandom_exit(void)
 336 {
 337         multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
 338 }
 339
 340 module_init(wrandom_init);
 341 module_exit(wrandom_exit);
 342 MODULE_LICENSE("GPL");