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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Randy Dunlap6efd8452005-06-13 14:29:06 -070034#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070035#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
54struct multipath_candidate {
55 struct multipath_candidate *next;
56 int power;
57 struct rtable *rt;
58};
59
60struct 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
71struct multipath_bucket {
72 struct list_head head;
73 spinlock_t lock;
74};
75
76struct 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 */
87static struct multipath_bucket state[MULTIPATH_STATE_SIZE];
88
89/* interface to random number generation */
90static unsigned int RANDOM_SEED = 93186752;
91
92static 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
101static 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
141out:
142 rcu_read_unlock();
143 return weight;
144}
145
146static 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
156static 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*)
Patrick McHardy60d53062005-05-05 14:30:15 -0700176 kmalloc(size_mpc, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177
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
225static 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 *)
Patrick McHardy60d53062005-05-05 14:30:15 -0700248 kmalloc(size_rt, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249
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*)
Patrick McHardy60d53062005-05-05 14:30:15 -0700269 kmalloc(size_dst, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270
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
286static 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
293static 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
301static 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
326static 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
332static int __init wrandom_init(void)
333{
334 wrandom_init_state();
335
336 return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
337}
338
339static void __exit wrandom_exit(void)
340{
341 multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
342}
343
344module_init(wrandom_init);
345module_exit(wrandom_exit);
Randy Dunlap6efd8452005-06-13 14:29:06 -0700346MODULE_LICENSE("GPL");