[NETFILTER]: Fix possible overflow in netfilters do_replace()
[linux-2.6.git] / net / bridge / br_stp.c
1 /*
2  *      Spanning tree protocol; generic parts
3  *      Linux ethernet bridge
4  *
5  *      Authors:
6  *      Lennert Buytenhek               <buytenh@gnu.org>
7  *
8  *      $Id: br_stp.c,v 1.4 2000/06/19 10:13:35 davem Exp $
9  *
10  *      This program is free software; you can redistribute it and/or
11  *      modify it under the terms of the GNU General Public License
12  *      as published by the Free Software Foundation; either version
13  *      2 of the License, or (at your option) any later version.
14  */
15 #include <linux/kernel.h>
16 #include <linux/smp_lock.h>
17
18 #include "br_private.h"
19 #include "br_private_stp.h"
20
21 /* since time values in bpdu are in jiffies and then scaled (1/256)
22  * before sending, make sure that is at least one.
23  */
24 #define MESSAGE_AGE_INCR        ((HZ < 256) ? 1 : (HZ/256))
25
26 static const char *br_port_state_names[] = {
27         [BR_STATE_DISABLED] = "disabled", 
28         [BR_STATE_LISTENING] = "listening",
29         [BR_STATE_LEARNING] = "learning", 
30         [BR_STATE_FORWARDING] = "forwarding", 
31         [BR_STATE_BLOCKING] = "blocking",
32 };
33
34 void br_log_state(const struct net_bridge_port *p)
35 {
36         pr_info("%s: port %d(%s) entering %s state\n",
37                 p->br->dev->name, p->port_no, p->dev->name, 
38                 br_port_state_names[p->state]);
39
40 }
41
42 /* called under bridge lock */
43 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
44 {
45         struct net_bridge_port *p;
46
47         list_for_each_entry_rcu(p, &br->port_list, list) {
48                 if (p->port_no == port_no)
49                         return p;
50         }
51
52         return NULL;
53 }
54
55 /* called under bridge lock */
56 static int br_should_become_root_port(const struct net_bridge_port *p, 
57                                       u16 root_port)
58 {
59         struct net_bridge *br;
60         struct net_bridge_port *rp;
61         int t;
62
63         br = p->br;
64         if (p->state == BR_STATE_DISABLED ||
65             br_is_designated_port(p))
66                 return 0;
67
68         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
69                 return 0;
70
71         if (!root_port)
72                 return 1;
73
74         rp = br_get_port(br, root_port);
75
76         t = memcmp(&p->designated_root, &rp->designated_root, 8);
77         if (t < 0)
78                 return 1;
79         else if (t > 0)
80                 return 0;
81
82         if (p->designated_cost + p->path_cost <
83             rp->designated_cost + rp->path_cost)
84                 return 1;
85         else if (p->designated_cost + p->path_cost >
86                  rp->designated_cost + rp->path_cost)
87                 return 0;
88
89         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
90         if (t < 0)
91                 return 1;
92         else if (t > 0)
93                 return 0;
94
95         if (p->designated_port < rp->designated_port)
96                 return 1;
97         else if (p->designated_port > rp->designated_port)
98                 return 0;
99
100         if (p->port_id < rp->port_id)
101                 return 1;
102
103         return 0;
104 }
105
106 /* called under bridge lock */
107 static void br_root_selection(struct net_bridge *br)
108 {
109         struct net_bridge_port *p;
110         u16 root_port = 0;
111
112         list_for_each_entry(p, &br->port_list, list) {
113                 if (br_should_become_root_port(p, root_port))
114                         root_port = p->port_no;
115
116         }
117
118         br->root_port = root_port;
119
120         if (!root_port) {
121                 br->designated_root = br->bridge_id;
122                 br->root_path_cost = 0;
123         } else {
124                 p = br_get_port(br, root_port);
125                 br->designated_root = p->designated_root;
126                 br->root_path_cost = p->designated_cost + p->path_cost;
127         }
128 }
129
130 /* called under bridge lock */
131 void br_become_root_bridge(struct net_bridge *br)
132 {
133         br->max_age = br->bridge_max_age;
134         br->hello_time = br->bridge_hello_time;
135         br->forward_delay = br->bridge_forward_delay;
136         br_topology_change_detection(br);
137         del_timer(&br->tcn_timer);
138
139         if (br->dev->flags & IFF_UP) {
140                 br_config_bpdu_generation(br);
141                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
142         }
143 }
144
145 /* called under bridge lock */
146 void br_transmit_config(struct net_bridge_port *p)
147 {
148         struct br_config_bpdu bpdu;
149         struct net_bridge *br;
150
151
152         if (timer_pending(&p->hold_timer)) {
153                 p->config_pending = 1;
154                 return;
155         }
156
157         br = p->br;
158
159         bpdu.topology_change = br->topology_change;
160         bpdu.topology_change_ack = p->topology_change_ack;
161         bpdu.root = br->designated_root;
162         bpdu.root_path_cost = br->root_path_cost;
163         bpdu.bridge_id = br->bridge_id;
164         bpdu.port_id = p->port_id;
165         if (br_is_root_bridge(br))
166                 bpdu.message_age = 0;
167         else {
168                 struct net_bridge_port *root
169                         = br_get_port(br, br->root_port);
170                 bpdu.message_age = br->max_age
171                         - (root->message_age_timer.expires - jiffies)
172                         + MESSAGE_AGE_INCR;
173         }
174         bpdu.max_age = br->max_age;
175         bpdu.hello_time = br->hello_time;
176         bpdu.forward_delay = br->forward_delay;
177
178         if (bpdu.message_age < br->max_age) {
179                 br_send_config_bpdu(p, &bpdu);
180                 p->topology_change_ack = 0;
181                 p->config_pending = 0;
182                 mod_timer(&p->hold_timer, jiffies + BR_HOLD_TIME);
183         }
184 }
185
186 /* called under bridge lock */
187 static inline void br_record_config_information(struct net_bridge_port *p, 
188                                                 const struct br_config_bpdu *bpdu)
189 {
190         p->designated_root = bpdu->root;
191         p->designated_cost = bpdu->root_path_cost;
192         p->designated_bridge = bpdu->bridge_id;
193         p->designated_port = bpdu->port_id;
194
195         mod_timer(&p->message_age_timer, jiffies 
196                   + (p->br->max_age - bpdu->message_age));
197 }
198
199 /* called under bridge lock */
200 static inline void br_record_config_timeout_values(struct net_bridge *br, 
201                                             const struct br_config_bpdu *bpdu)
202 {
203         br->max_age = bpdu->max_age;
204         br->hello_time = bpdu->hello_time;
205         br->forward_delay = bpdu->forward_delay;
206         br->topology_change = bpdu->topology_change;
207 }
208
209 /* called under bridge lock */
210 void br_transmit_tcn(struct net_bridge *br)
211 {
212         br_send_tcn_bpdu(br_get_port(br, br->root_port));
213 }
214
215 /* called under bridge lock */
216 static int br_should_become_designated_port(const struct net_bridge_port *p)
217 {
218         struct net_bridge *br;
219         int t;
220
221         br = p->br;
222         if (br_is_designated_port(p))
223                 return 1;
224
225         if (memcmp(&p->designated_root, &br->designated_root, 8))
226                 return 1;
227
228         if (br->root_path_cost < p->designated_cost)
229                 return 1;
230         else if (br->root_path_cost > p->designated_cost)
231                 return 0;
232
233         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
234         if (t < 0)
235                 return 1;
236         else if (t > 0)
237                 return 0;
238
239         if (p->port_id < p->designated_port)
240                 return 1;
241
242         return 0;
243 }
244
245 /* called under bridge lock */
246 static void br_designated_port_selection(struct net_bridge *br)
247 {
248         struct net_bridge_port *p;
249
250         list_for_each_entry(p, &br->port_list, list) {
251                 if (p->state != BR_STATE_DISABLED &&
252                     br_should_become_designated_port(p))
253                         br_become_designated_port(p);
254
255         }
256 }
257
258 /* called under bridge lock */
259 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
260 {
261         int t;
262
263         t = memcmp(&bpdu->root, &p->designated_root, 8);
264         if (t < 0)
265                 return 1;
266         else if (t > 0)
267                 return 0;
268
269         if (bpdu->root_path_cost < p->designated_cost)
270                 return 1;
271         else if (bpdu->root_path_cost > p->designated_cost)
272                 return 0;
273
274         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
275         if (t < 0)
276                 return 1;
277         else if (t > 0)
278                 return 0;
279
280         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
281                 return 1;
282
283         if (bpdu->port_id <= p->designated_port)
284                 return 1;
285
286         return 0;
287 }
288
289 /* called under bridge lock */
290 static inline void br_topology_change_acknowledged(struct net_bridge *br)
291 {
292         br->topology_change_detected = 0;
293         del_timer(&br->tcn_timer);
294 }
295
296 /* called under bridge lock */
297 void br_topology_change_detection(struct net_bridge *br)
298 {
299         int isroot = br_is_root_bridge(br);
300
301         pr_info("%s: topology change detected, %s\n", br->dev->name,
302                 isroot ? "propagating" : "sending tcn bpdu");
303
304         if (isroot) {
305                 br->topology_change = 1;
306                 mod_timer(&br->topology_change_timer, jiffies
307                           + br->bridge_forward_delay + br->bridge_max_age);
308         } else if (!br->topology_change_detected) {
309                 br_transmit_tcn(br);
310                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
311         }
312
313         br->topology_change_detected = 1;
314 }
315
316 /* called under bridge lock */
317 void br_config_bpdu_generation(struct net_bridge *br)
318 {
319         struct net_bridge_port *p;
320
321         list_for_each_entry(p, &br->port_list, list) {
322                 if (p->state != BR_STATE_DISABLED &&
323                     br_is_designated_port(p))
324                         br_transmit_config(p);
325         }
326 }
327
328 /* called under bridge lock */
329 static inline void br_reply(struct net_bridge_port *p)
330 {
331         br_transmit_config(p);
332 }
333
334 /* called under bridge lock */
335 void br_configuration_update(struct net_bridge *br)
336 {
337         br_root_selection(br);
338         br_designated_port_selection(br);
339 }
340
341 /* called under bridge lock */
342 void br_become_designated_port(struct net_bridge_port *p)
343 {
344         struct net_bridge *br;
345
346         br = p->br;
347         p->designated_root = br->designated_root;
348         p->designated_cost = br->root_path_cost;
349         p->designated_bridge = br->bridge_id;
350         p->designated_port = p->port_id;
351 }
352
353
354 /* called under bridge lock */
355 static void br_make_blocking(struct net_bridge_port *p)
356 {
357         if (p->state != BR_STATE_DISABLED &&
358             p->state != BR_STATE_BLOCKING) {
359                 if (p->state == BR_STATE_FORWARDING ||
360                     p->state == BR_STATE_LEARNING)
361                         br_topology_change_detection(p->br);
362
363                 p->state = BR_STATE_BLOCKING;
364                 br_log_state(p);
365                 del_timer(&p->forward_delay_timer);
366         }
367 }
368
369 /* called under bridge lock */
370 static void br_make_forwarding(struct net_bridge_port *p)
371 {
372         if (p->state == BR_STATE_BLOCKING) {
373                 if (p->br->stp_enabled) {
374                         p->state = BR_STATE_LISTENING;
375                 } else {
376                         p->state = BR_STATE_LEARNING;
377                 }
378                 br_log_state(p);
379                 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay);     }
380 }
381
382 /* called under bridge lock */
383 void br_port_state_selection(struct net_bridge *br)
384 {
385         struct net_bridge_port *p;
386
387         list_for_each_entry(p, &br->port_list, list) {
388                 if (p->state != BR_STATE_DISABLED) {
389                         if (p->port_no == br->root_port) {
390                                 p->config_pending = 0;
391                                 p->topology_change_ack = 0;
392                                 br_make_forwarding(p);
393                         } else if (br_is_designated_port(p)) {
394                                 del_timer(&p->message_age_timer);
395                                 br_make_forwarding(p);
396                         } else {
397                                 p->config_pending = 0;
398                                 p->topology_change_ack = 0;
399                                 br_make_blocking(p);
400                         }
401                 }
402
403         }
404 }
405
406 /* called under bridge lock */
407 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
408 {
409         p->topology_change_ack = 1;
410         br_transmit_config(p);
411 }
412
413 /* called under bridge lock */
414 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
415 {
416         struct net_bridge *br;
417         int was_root;
418  
419         br = p->br;
420         was_root = br_is_root_bridge(br);
421
422         if (br_supersedes_port_info(p, bpdu)) {
423                 br_record_config_information(p, bpdu);
424                 br_configuration_update(br);
425                 br_port_state_selection(br);
426
427                 if (!br_is_root_bridge(br) && was_root) {
428                         del_timer(&br->hello_timer);
429                         if (br->topology_change_detected) {
430                                 del_timer(&br->topology_change_timer);
431                                 br_transmit_tcn(br);
432
433                                 mod_timer(&br->tcn_timer, 
434                                           jiffies + br->bridge_hello_time);
435                         }
436                 }
437
438                 if (p->port_no == br->root_port) {
439                         br_record_config_timeout_values(br, bpdu);
440                         br_config_bpdu_generation(br);
441                         if (bpdu->topology_change_ack)
442                                 br_topology_change_acknowledged(br);
443                 }
444         } else if (br_is_designated_port(p)) {          
445                 br_reply(p);            
446         }
447 }
448
449 /* called under bridge lock */
450 void br_received_tcn_bpdu(struct net_bridge_port *p)
451 {
452         if (br_is_designated_port(p)) {
453                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
454                        p->br->dev->name, p->port_no, p->dev->name);
455
456                 br_topology_change_detection(p->br);
457                 br_topology_change_acknowledge(p);
458         }
459 }