[IPV4]: multipath_set_nhinfo() annotations
[linux-2.6.git] / 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/sched.h>
19 #include <linux/errno.h>
20 #include <linux/timer.h>
21 #include <linux/mm.h>
22 #include <linux/kernel.h>
23 #include <linux/fcntl.h>
24 #include <linux/stat.h>
25 #include <linux/socket.h>
26 #include <linux/in.h>
27 #include <linux/inet.h>
28 #include <linux/netdevice.h>
29 #include <linux/inetdevice.h>
30 #include <linux/igmp.h>
31 #include <linux/proc_fs.h>
32 #include <linux/seq_file.h>
33 #include <linux/module.h>
34 #include <linux/mroute.h>
35 #include <linux/init.h>
36 #include <net/ip.h>
37 #include <net/protocol.h>
38 #include <linux/skbuff.h>
39 #include <net/sock.h>
40 #include <net/icmp.h>
41 #include <net/udp.h>
42 #include <net/raw.h>
43 #include <linux/notifier.h>
44 #include <linux/if_arp.h>
45 #include <linux/netfilter_ipv4.h>
46 #include <net/ipip.h>
47 #include <net/checksum.h>
48 #include <net/ip_fib.h>
49 #include <net/ip_mp_alg.h>
50
51 #define MULTIPATH_STATE_SIZE 15
52
53 struct multipath_candidate {
54         struct multipath_candidate      *next;
55         int                             power;
56         struct rtable                   *rt;
57 };
58
59 struct multipath_dest {
60         struct list_head        list;
61
62         const struct fib_nh     *nh_info;
63         __u32                   netmask;
64         __u32                   network;
65         unsigned char           prefixlen;
66
67         struct rcu_head         rcu;
68 };
69
70 struct multipath_bucket {
71         struct list_head        head;
72         spinlock_t              lock;
73 };
74
75 struct multipath_route {
76         struct list_head        list;
77
78         int                     oif;
79         __u32                   gw;
80         struct list_head        dests;
81
82         struct rcu_head         rcu;
83 };
84
85 /* state: primarily weight per route information */
86 static struct multipath_bucket state[MULTIPATH_STATE_SIZE];
87
88 /* interface to random number generation */
89 static unsigned int RANDOM_SEED = 93186752;
90
91 static inline unsigned int random(unsigned int ubound)
92 {
93         static unsigned int a = 1588635695,
94                 q = 2,
95                 r = 1117695901;
96         RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q);
97         return RANDOM_SEED % ubound;
98 }
99
100 static unsigned char __multipath_lookup_weight(const struct flowi *fl,
101                                                const struct rtable *rt)
102 {
103         const int state_idx = rt->idev->dev->ifindex % MULTIPATH_STATE_SIZE;
104         struct multipath_route *r;
105         struct multipath_route *target_route = NULL;
106         struct multipath_dest *d;
107         int weight = 1;
108
109         /* lookup the weight information for a certain route */
110         rcu_read_lock();
111
112         /* find state entry for gateway or add one if necessary */
113         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
114                 if (r->gw == rt->rt_gateway &&
115                     r->oif == rt->idev->dev->ifindex) {
116                         target_route = r;
117                         break;
118                 }
119         }
120
121         if (!target_route) {
122                 /* this should not happen... but we are prepared */
123                 printk( KERN_CRIT"%s: missing state for gateway: %u and " \
124                         "device %d\n", __FUNCTION__, rt->rt_gateway,
125                         rt->idev->dev->ifindex);
126                 goto out;
127         }
128
129         /* find state entry for destination */
130         list_for_each_entry_rcu(d, &target_route->dests, list) {
131                 __u32 targetnetwork = fl->fl4_dst & 
132                         (0xFFFFFFFF >> (32 - d->prefixlen));
133
134                 if ((targetnetwork & d->netmask) == d->network) {
135                         weight = d->nh_info->nh_weight;
136                         goto out;
137                 }
138         }
139
140 out:
141         rcu_read_unlock();
142         return weight;
143 }
144
145 static void wrandom_init_state(void) 
146 {
147         int i;
148
149         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
150                 INIT_LIST_HEAD(&state[i].head);
151                 spin_lock_init(&state[i].lock);
152         }
153 }
154
155 static void wrandom_select_route(const struct flowi *flp,
156                                  struct rtable *first,
157                                  struct rtable **rp)
158 {
159         struct rtable *rt;
160         struct rtable *decision;
161         struct multipath_candidate *first_mpc = NULL;
162         struct multipath_candidate *mpc, *last_mpc = NULL;
163         int power = 0;
164         int last_power;
165         int selector;
166         const size_t size_mpc = sizeof(struct multipath_candidate);
167
168         /* collect all candidates and identify their weights */
169         for (rt = rcu_dereference(first); rt;
170              rt = rcu_dereference(rt->u.rt_next)) {
171                 if ((rt->u.dst.flags & DST_BALANCED) != 0 &&
172                     multipath_comparekeys(&rt->fl, flp)) {
173                         struct multipath_candidate* mpc =
174                                 (struct multipath_candidate*)
175                                 kmalloc(size_mpc, GFP_ATOMIC);
176
177                         if (!mpc)
178                                 return;
179
180                         power += __multipath_lookup_weight(flp, rt) * 10000;
181
182                         mpc->power = power;
183                         mpc->rt = rt;
184                         mpc->next = NULL;
185
186                         if (!first_mpc)
187                                 first_mpc = mpc;
188                         else
189                                 last_mpc->next = mpc;
190
191                         last_mpc = mpc;
192                 }
193         }
194
195         /* choose a weighted random candidate */
196         decision = first;
197         selector = random(power);
198         last_power = 0;
199
200         /* select candidate, adjust GC data and cleanup local state */
201         decision = first;
202         last_mpc = NULL;
203         for (mpc = first_mpc; mpc; mpc = mpc->next) {
204                 mpc->rt->u.dst.lastuse = jiffies;
205                 if (last_power <= selector && selector < mpc->power)
206                         decision = mpc->rt;
207
208                 last_power = mpc->power;
209                 kfree(last_mpc);
210                 last_mpc = mpc;
211         }
212
213         /* concurrent __multipath_flush may lead to !last_mpc */
214         kfree(last_mpc);
215
216         decision->u.dst.__use++;
217         *rp = decision;
218 }
219
220 static void wrandom_set_nhinfo(__be32 network,
221                                __be32 netmask,
222                                unsigned char prefixlen,
223                                const struct fib_nh *nh)
224 {
225         const int state_idx = nh->nh_oif % MULTIPATH_STATE_SIZE;
226         struct multipath_route *r, *target_route = NULL;
227         struct multipath_dest *d, *target_dest = NULL;
228
229         /* store the weight information for a certain route */
230         spin_lock_bh(&state[state_idx].lock);
231
232         /* find state entry for gateway or add one if necessary */
233         list_for_each_entry_rcu(r, &state[state_idx].head, list) {
234                 if (r->gw == nh->nh_gw && r->oif == nh->nh_oif) {
235                         target_route = r;
236                         break;
237                 }
238         }
239
240         if (!target_route) {
241                 const size_t size_rt = sizeof(struct multipath_route);
242                 target_route = (struct multipath_route *)
243                         kmalloc(size_rt, GFP_ATOMIC);
244
245                 target_route->gw = nh->nh_gw;
246                 target_route->oif = nh->nh_oif;
247                 memset(&target_route->rcu, 0, sizeof(struct rcu_head));
248                 INIT_LIST_HEAD(&target_route->dests);
249
250                 list_add_rcu(&target_route->list, &state[state_idx].head);
251         }
252
253         /* find state entry for destination or add one if necessary */
254         list_for_each_entry_rcu(d, &target_route->dests, list) {
255                 if (d->nh_info == nh) {
256                         target_dest = d;
257                         break;
258                 }
259         }
260
261         if (!target_dest) {
262                 const size_t size_dst = sizeof(struct multipath_dest);
263                 target_dest = (struct multipath_dest*)
264                         kmalloc(size_dst, GFP_ATOMIC);
265
266                 target_dest->nh_info = nh;
267                 target_dest->network = network;
268                 target_dest->netmask = netmask;
269                 target_dest->prefixlen = prefixlen;
270                 memset(&target_dest->rcu, 0, sizeof(struct rcu_head));
271
272                 list_add_rcu(&target_dest->list, &target_route->dests);
273         }
274         /* else: we already stored this info for another destination =>
275          * we are finished
276          */
277
278         spin_unlock_bh(&state[state_idx].lock);
279 }
280
281 static void __multipath_free(struct rcu_head *head)
282 {
283         struct multipath_route *rt = container_of(head, struct multipath_route,
284                                                   rcu);
285         kfree(rt);
286 }
287
288 static void __multipath_free_dst(struct rcu_head *head)
289 {
290         struct multipath_dest *dst = container_of(head,
291                                                   struct multipath_dest,
292                                                   rcu);
293         kfree(dst);
294 }
295
296 static void wrandom_flush(void)
297 {
298         int i;
299
300         /* defere delete to all entries */
301         for (i = 0; i < MULTIPATH_STATE_SIZE; ++i) {
302                 struct multipath_route *r;
303
304                 spin_lock_bh(&state[i].lock);
305                 list_for_each_entry_rcu(r, &state[i].head, list) {
306                         struct multipath_dest *d;
307                         list_for_each_entry_rcu(d, &r->dests, list) {
308                                 list_del_rcu(&d->list);
309                                 call_rcu(&d->rcu,
310                                          __multipath_free_dst);
311                         }
312                         list_del_rcu(&r->list);
313                         call_rcu(&r->rcu,
314                                  __multipath_free);
315                 }
316
317                 spin_unlock_bh(&state[i].lock);
318         }
319 }
320
321 static struct ip_mp_alg_ops wrandom_ops = {
322         .mp_alg_select_route    =       wrandom_select_route,
323         .mp_alg_flush           =       wrandom_flush,
324         .mp_alg_set_nhinfo      =       wrandom_set_nhinfo,
325 };
326
327 static int __init wrandom_init(void)
328 {
329         wrandom_init_state();
330
331         return multipath_alg_register(&wrandom_ops, IP_MP_ALG_WRANDOM);
332 }
333
334 static void __exit wrandom_exit(void)
335 {
336         multipath_alg_unregister(&wrandom_ops, IP_MP_ALG_WRANDOM);
337 }
338
339 module_init(wrandom_init);
340 module_exit(wrandom_exit);
341 MODULE_LICENSE("GPL");