2 * Weighted random policy for multipath.
5 * Version: $Id: multipath_wrandom.c,v 1.1.2.3 2004/09/22 07:51:40 elueck Exp $
7 * Authors: Einar Lueck <elueck@de.ibm.com><lkml@einar-lueck.de>
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.
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>
23 #include <linux/kernel.h>
24 #include <linux/fcntl.h>
25 #include <linux/stat.h>
26 #include <linux/socket.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>
38 #include <net/protocol.h>
39 #include <linux/skbuff.h>
44 #include <linux/notifier.h>
45 #include <linux/if_arp.h>
46 #include <linux/netfilter_ipv4.h>
48 #include <net/checksum.h>
49 #include <net/ip_fib.h>
50 #include <net/ip_mp_alg.h>
52 #define MULTIPATH_STATE_SIZE 15
54 struct multipath_candidate {
55 struct multipath_candidate *next;
60 struct multipath_dest {
61 struct list_head list;
63 const struct fib_nh *nh_info;
66 unsigned char prefixlen;
71 struct multipath_bucket {
72 struct list_head head;
76 struct multipath_route {
77 struct list_head list;
81 struct list_head dests;
86 /* state: primarily weight per route information */
87 static struct multipath_bucket state[MULTIPATH_STATE_SIZE];
89 /* interface to random number generation */
90 static unsigned int RANDOM_SEED = 93186752;
92 static inline unsigned int random(unsigned int ubound)
94 static unsigned int a = 1588635695,
97 RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
98 return RANDOM_SEED % ubound;
101 static unsigned char __multipath_lookup_weight(const struct flowi *fl,
102 const struct rtable *rt)
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;
110 /* lookup the weight information for a certain route */
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) {
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);
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));
135 if ((targetnetwork & d->netmask) == d->network) {
136 weight = d->nh_info->nh_weight;
146 static void wrandom_init_state(void)
150 for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
151 INIT_LIST_HEAD(&state[i].head);
152 spin_lock_init(&state[i].lock);
156 static void wrandom_select_route(const struct flowi *flp,
157 struct rtable *first,
161 struct rtable *decision;
162 struct multipath_candidate *first_mpc = NULL;
163 struct multipath_candidate *mpc, *last_mpc = NULL;
167 const size_t size_mpc = sizeof(struct multipath_candidate);
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);
181 power += __multipath_lookup_weight(flp, rt) * 10000;
190 last_mpc->next = mpc;
196 /* choose a weighted random candidate */
198 selector = random(power);
201 /* select candidate, adjust GC data and cleanup local state */
204 for (mpc = first_mpc; mpc; mpc = mpc->next) {
205 mpc->rt->u.dst.lastuse = jiffies;
206 if (last_power <= selector && selector < mpc->power)
209 last_power = mpc->power;
217 /* concurrent __multipath_flush may lead to !last_mpc */
221 decision->u.dst.__use++;
225 static void wrandom_set_nhinfo(__u32 network,
227 unsigned char prefixlen,
228 const struct fib_nh *nh)
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;
234 /* store the weight information for a certain route */
235 spin_lock(&state[state_idx].lock);
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) {
246 const size_t size_rt = sizeof(struct multipath_route);
247 target_route = (struct multipath_route *)
248 kmalloc(size_rt, GFP_ATOMIC);
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);
255 list_add_rcu(&target_route->list, &state[state_idx].head);
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) {
267 const size_t size_dst = sizeof(struct multipath_dest);
268 target_dest = (struct multipath_dest*)
269 kmalloc(size_dst, GFP_ATOMIC);
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));
277 list_add_rcu(&target_dest->list, &target_route->dests);
279 /* else: we already stored this info for another destination =>
283 spin_unlock(&state[state_idx].lock);
286 static void __multipath_free(struct rcu_head *head)
288 struct multipath_route *rt = container_of(head, struct multipath_route,
293 static void __multipath_free_dst(struct rcu_head *head)
295 struct multipath_dest *dst = container_of(head,
296 struct multipath_dest,
301 static void wrandom_flush(void)
305 /* defere delete to all entries */
306 for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
307 struct multipath_route *r;
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);
315 __multipath_free_dst);
317 list_del_rcu(&r->list);
322 spin_unlock(&state[i].lock);
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,
332 static int __init wrandom_init(void)
334 wrandom_init_state();
336 return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
339 static void __exit wrandom_exit(void)
341 multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
344 module_init(wrandom_init);
345 module_exit(wrandom_exit);
346 MODULE_LICENSE("GPL");