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Linux/net/bridge/br_stp.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  *      Spanning tree protocol; generic parts
  4  *      Linux ethernet bridge
  5  *
  6  *      Authors:
  7  *      Lennert Buytenhek               <buytenh@gnu.org>
  8  */
  9 #include <linux/kernel.h>
 10 #include <linux/rculist.h>
 11 #include <net/switchdev.h>
 12 
 13 #include "br_private.h"
 14 #include "br_private_stp.h"
 15 
 16 /* since time values in bpdu are in jiffies and then scaled (1/256)
 17  * before sending, make sure that is at least one STP tick.
 18  */
 19 #define MESSAGE_AGE_INCR        ((HZ / 256) + 1)
 20 
 21 static const char *const br_port_state_names[] = {
 22         [BR_STATE_DISABLED] = "disabled",
 23         [BR_STATE_LISTENING] = "listening",
 24         [BR_STATE_LEARNING] = "learning",
 25         [BR_STATE_FORWARDING] = "forwarding",
 26         [BR_STATE_BLOCKING] = "blocking",
 27 };
 28 
 29 void br_set_state(struct net_bridge_port *p, unsigned int state)
 30 {
 31         struct switchdev_attr attr = {
 32                 .orig_dev = p->dev,
 33                 .id = SWITCHDEV_ATTR_ID_PORT_STP_STATE,
 34                 .flags = SWITCHDEV_F_DEFER,
 35                 .u.stp_state = state,
 36         };
 37         int err;
 38 
 39         p->state = state;
 40         err = switchdev_port_attr_set(p->dev, &attr);
 41         if (err && err != -EOPNOTSUPP)
 42                 br_warn(p->br, "error setting offload STP state on port %u(%s)\n",
 43                                 (unsigned int) p->port_no, p->dev->name);
 44         else
 45                 br_info(p->br, "port %u(%s) entered %s state\n",
 46                                 (unsigned int) p->port_no, p->dev->name,
 47                                 br_port_state_names[p->state]);
 48 }
 49 
 50 /* called under bridge lock */
 51 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
 52 {
 53         struct net_bridge_port *p;
 54 
 55         list_for_each_entry_rcu(p, &br->port_list, list) {
 56                 if (p->port_no == port_no)
 57                         return p;
 58         }
 59 
 60         return NULL;
 61 }
 62 
 63 /* called under bridge lock */
 64 static int br_should_become_root_port(const struct net_bridge_port *p,
 65                                       u16 root_port)
 66 {
 67         struct net_bridge *br;
 68         struct net_bridge_port *rp;
 69         int t;
 70 
 71         br = p->br;
 72         if (p->state == BR_STATE_DISABLED ||
 73             br_is_designated_port(p))
 74                 return 0;
 75 
 76         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
 77                 return 0;
 78 
 79         if (!root_port)
 80                 return 1;
 81 
 82         rp = br_get_port(br, root_port);
 83 
 84         t = memcmp(&p->designated_root, &rp->designated_root, 8);
 85         if (t < 0)
 86                 return 1;
 87         else if (t > 0)
 88                 return 0;
 89 
 90         if (p->designated_cost + p->path_cost <
 91             rp->designated_cost + rp->path_cost)
 92                 return 1;
 93         else if (p->designated_cost + p->path_cost >
 94                  rp->designated_cost + rp->path_cost)
 95                 return 0;
 96 
 97         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
 98         if (t < 0)
 99                 return 1;
100         else if (t > 0)
101                 return 0;
102 
103         if (p->designated_port < rp->designated_port)
104                 return 1;
105         else if (p->designated_port > rp->designated_port)
106                 return 0;
107 
108         if (p->port_id < rp->port_id)
109                 return 1;
110 
111         return 0;
112 }
113 
114 static void br_root_port_block(const struct net_bridge *br,
115                                struct net_bridge_port *p)
116 {
117 
118         br_notice(br, "port %u(%s) tried to become root port (blocked)",
119                   (unsigned int) p->port_no, p->dev->name);
120 
121         br_set_state(p, BR_STATE_LISTENING);
122         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
123 
124         if (br->forward_delay > 0)
125                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
126 }
127 
128 /* called under bridge lock */
129 static void br_root_selection(struct net_bridge *br)
130 {
131         struct net_bridge_port *p;
132         u16 root_port = 0;
133 
134         list_for_each_entry(p, &br->port_list, list) {
135                 if (!br_should_become_root_port(p, root_port))
136                         continue;
137 
138                 if (p->flags & BR_ROOT_BLOCK)
139                         br_root_port_block(br, p);
140                 else
141                         root_port = p->port_no;
142         }
143 
144         br->root_port = root_port;
145 
146         if (!root_port) {
147                 br->designated_root = br->bridge_id;
148                 br->root_path_cost = 0;
149         } else {
150                 p = br_get_port(br, root_port);
151                 br->designated_root = p->designated_root;
152                 br->root_path_cost = p->designated_cost + p->path_cost;
153         }
154 }
155 
156 /* called under bridge lock */
157 void br_become_root_bridge(struct net_bridge *br)
158 {
159         br->max_age = br->bridge_max_age;
160         br->hello_time = br->bridge_hello_time;
161         br->forward_delay = br->bridge_forward_delay;
162         br_topology_change_detection(br);
163         del_timer(&br->tcn_timer);
164 
165         if (br->dev->flags & IFF_UP) {
166                 br_config_bpdu_generation(br);
167                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
168         }
169 }
170 
171 /* called under bridge lock */
172 void br_transmit_config(struct net_bridge_port *p)
173 {
174         struct br_config_bpdu bpdu;
175         struct net_bridge *br;
176 
177         if (timer_pending(&p->hold_timer)) {
178                 p->config_pending = 1;
179                 return;
180         }
181 
182         br = p->br;
183 
184         bpdu.topology_change = br->topology_change;
185         bpdu.topology_change_ack = p->topology_change_ack;
186         bpdu.root = br->designated_root;
187         bpdu.root_path_cost = br->root_path_cost;
188         bpdu.bridge_id = br->bridge_id;
189         bpdu.port_id = p->port_id;
190         if (br_is_root_bridge(br))
191                 bpdu.message_age = 0;
192         else {
193                 struct net_bridge_port *root
194                         = br_get_port(br, br->root_port);
195                 bpdu.message_age = (jiffies - root->designated_age)
196                         + MESSAGE_AGE_INCR;
197         }
198         bpdu.max_age = br->max_age;
199         bpdu.hello_time = br->hello_time;
200         bpdu.forward_delay = br->forward_delay;
201 
202         if (bpdu.message_age < br->max_age) {
203                 br_send_config_bpdu(p, &bpdu);
204                 p->topology_change_ack = 0;
205                 p->config_pending = 0;
206                 if (p->br->stp_enabled == BR_KERNEL_STP)
207                         mod_timer(&p->hold_timer,
208                                   round_jiffies(jiffies + BR_HOLD_TIME));
209         }
210 }
211 
212 /* called under bridge lock */
213 static void br_record_config_information(struct net_bridge_port *p,
214                                          const struct br_config_bpdu *bpdu)
215 {
216         p->designated_root = bpdu->root;
217         p->designated_cost = bpdu->root_path_cost;
218         p->designated_bridge = bpdu->bridge_id;
219         p->designated_port = bpdu->port_id;
220         p->designated_age = jiffies - bpdu->message_age;
221 
222         mod_timer(&p->message_age_timer, jiffies
223                   + (bpdu->max_age - bpdu->message_age));
224 }
225 
226 /* called under bridge lock */
227 static void br_record_config_timeout_values(struct net_bridge *br,
228                                             const struct br_config_bpdu *bpdu)
229 {
230         br->max_age = bpdu->max_age;
231         br->hello_time = bpdu->hello_time;
232         br->forward_delay = bpdu->forward_delay;
233         __br_set_topology_change(br, bpdu->topology_change);
234 }
235 
236 /* called under bridge lock */
237 void br_transmit_tcn(struct net_bridge *br)
238 {
239         struct net_bridge_port *p;
240 
241         p = br_get_port(br, br->root_port);
242         if (p)
243                 br_send_tcn_bpdu(p);
244         else
245                 br_notice(br, "root port %u not found for topology notice\n",
246                           br->root_port);
247 }
248 
249 /* called under bridge lock */
250 static int br_should_become_designated_port(const struct net_bridge_port *p)
251 {
252         struct net_bridge *br;
253         int t;
254 
255         br = p->br;
256         if (br_is_designated_port(p))
257                 return 1;
258 
259         if (memcmp(&p->designated_root, &br->designated_root, 8))
260                 return 1;
261 
262         if (br->root_path_cost < p->designated_cost)
263                 return 1;
264         else if (br->root_path_cost > p->designated_cost)
265                 return 0;
266 
267         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
268         if (t < 0)
269                 return 1;
270         else if (t > 0)
271                 return 0;
272 
273         if (p->port_id < p->designated_port)
274                 return 1;
275 
276         return 0;
277 }
278 
279 /* called under bridge lock */
280 static void br_designated_port_selection(struct net_bridge *br)
281 {
282         struct net_bridge_port *p;
283 
284         list_for_each_entry(p, &br->port_list, list) {
285                 if (p->state != BR_STATE_DISABLED &&
286                     br_should_become_designated_port(p))
287                         br_become_designated_port(p);
288 
289         }
290 }
291 
292 /* called under bridge lock */
293 static int br_supersedes_port_info(const struct net_bridge_port *p,
294                                    const struct br_config_bpdu *bpdu)
295 {
296         int t;
297 
298         t = memcmp(&bpdu->root, &p->designated_root, 8);
299         if (t < 0)
300                 return 1;
301         else if (t > 0)
302                 return 0;
303 
304         if (bpdu->root_path_cost < p->designated_cost)
305                 return 1;
306         else if (bpdu->root_path_cost > p->designated_cost)
307                 return 0;
308 
309         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
310         if (t < 0)
311                 return 1;
312         else if (t > 0)
313                 return 0;
314 
315         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
316                 return 1;
317 
318         if (bpdu->port_id <= p->designated_port)
319                 return 1;
320 
321         return 0;
322 }
323 
324 /* called under bridge lock */
325 static void br_topology_change_acknowledged(struct net_bridge *br)
326 {
327         br->topology_change_detected = 0;
328         del_timer(&br->tcn_timer);
329 }
330 
331 /* called under bridge lock */
332 void br_topology_change_detection(struct net_bridge *br)
333 {
334         int isroot = br_is_root_bridge(br);
335 
336         if (br->stp_enabled != BR_KERNEL_STP)
337                 return;
338 
339         br_info(br, "topology change detected, %s\n",
340                 isroot ? "propagating" : "sending tcn bpdu");
341 
342         if (isroot) {
343                 __br_set_topology_change(br, 1);
344                 mod_timer(&br->topology_change_timer, jiffies
345                           + br->bridge_forward_delay + br->bridge_max_age);
346         } else if (!br->topology_change_detected) {
347                 br_transmit_tcn(br);
348                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
349         }
350 
351         br->topology_change_detected = 1;
352 }
353 
354 /* called under bridge lock */
355 void br_config_bpdu_generation(struct net_bridge *br)
356 {
357         struct net_bridge_port *p;
358 
359         list_for_each_entry(p, &br->port_list, list) {
360                 if (p->state != BR_STATE_DISABLED &&
361                     br_is_designated_port(p))
362                         br_transmit_config(p);
363         }
364 }
365 
366 /* called under bridge lock */
367 static void br_reply(struct net_bridge_port *p)
368 {
369         br_transmit_config(p);
370 }
371 
372 /* called under bridge lock */
373 void br_configuration_update(struct net_bridge *br)
374 {
375         br_root_selection(br);
376         br_designated_port_selection(br);
377 }
378 
379 /* called under bridge lock */
380 void br_become_designated_port(struct net_bridge_port *p)
381 {
382         struct net_bridge *br;
383 
384         br = p->br;
385         p->designated_root = br->designated_root;
386         p->designated_cost = br->root_path_cost;
387         p->designated_bridge = br->bridge_id;
388         p->designated_port = p->port_id;
389 }
390 
391 
392 /* called under bridge lock */
393 static void br_make_blocking(struct net_bridge_port *p)
394 {
395         if (p->state != BR_STATE_DISABLED &&
396             p->state != BR_STATE_BLOCKING) {
397                 if (p->state == BR_STATE_FORWARDING ||
398                     p->state == BR_STATE_LEARNING)
399                         br_topology_change_detection(p->br);
400 
401                 br_set_state(p, BR_STATE_BLOCKING);
402                 br_ifinfo_notify(RTM_NEWLINK, NULL, p);
403 
404                 del_timer(&p->forward_delay_timer);
405         }
406 }
407 
408 /* called under bridge lock */
409 static void br_make_forwarding(struct net_bridge_port *p)
410 {
411         struct net_bridge *br = p->br;
412 
413         if (p->state != BR_STATE_BLOCKING)
414                 return;
415 
416         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
417                 br_set_state(p, BR_STATE_FORWARDING);
418                 br_topology_change_detection(br);
419                 del_timer(&p->forward_delay_timer);
420         } else if (br->stp_enabled == BR_KERNEL_STP)
421                 br_set_state(p, BR_STATE_LISTENING);
422         else
423                 br_set_state(p, BR_STATE_LEARNING);
424 
425         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
426 
427         if (br->forward_delay != 0)
428                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
429 }
430 
431 /* called under bridge lock */
432 void br_port_state_selection(struct net_bridge *br)
433 {
434         struct net_bridge_port *p;
435         unsigned int liveports = 0;
436 
437         list_for_each_entry(p, &br->port_list, list) {
438                 if (p->state == BR_STATE_DISABLED)
439                         continue;
440 
441                 /* Don't change port states if userspace is handling STP */
442                 if (br->stp_enabled != BR_USER_STP) {
443                         if (p->port_no == br->root_port) {
444                                 p->config_pending = 0;
445                                 p->topology_change_ack = 0;
446                                 br_make_forwarding(p);
447                         } else if (br_is_designated_port(p)) {
448                                 del_timer(&p->message_age_timer);
449                                 br_make_forwarding(p);
450                         } else {
451                                 p->config_pending = 0;
452                                 p->topology_change_ack = 0;
453                                 br_make_blocking(p);
454                         }
455                 }
456 
457                 if (p->state != BR_STATE_BLOCKING)
458                         br_multicast_enable_port(p);
459                 /* Multicast is not disabled for the port when it goes in
460                  * blocking state because the timers will expire and stop by
461                  * themselves without sending more queries.
462                  */
463                 if (p->state == BR_STATE_FORWARDING)
464                         ++liveports;
465         }
466 
467         if (liveports == 0)
468                 netif_carrier_off(br->dev);
469         else
470                 netif_carrier_on(br->dev);
471 }
472 
473 /* called under bridge lock */
474 static void br_topology_change_acknowledge(struct net_bridge_port *p)
475 {
476         p->topology_change_ack = 1;
477         br_transmit_config(p);
478 }
479 
480 /* called under bridge lock */
481 void br_received_config_bpdu(struct net_bridge_port *p,
482                              const struct br_config_bpdu *bpdu)
483 {
484         struct net_bridge *br;
485         int was_root;
486 
487         br = p->br;
488         was_root = br_is_root_bridge(br);
489 
490         if (br_supersedes_port_info(p, bpdu)) {
491                 br_record_config_information(p, bpdu);
492                 br_configuration_update(br);
493                 br_port_state_selection(br);
494 
495                 if (!br_is_root_bridge(br) && was_root) {
496                         del_timer(&br->hello_timer);
497                         if (br->topology_change_detected) {
498                                 del_timer(&br->topology_change_timer);
499                                 br_transmit_tcn(br);
500 
501                                 mod_timer(&br->tcn_timer,
502                                           jiffies + br->bridge_hello_time);
503                         }
504                 }
505 
506                 if (p->port_no == br->root_port) {
507                         br_record_config_timeout_values(br, bpdu);
508                         br_config_bpdu_generation(br);
509                         if (bpdu->topology_change_ack)
510                                 br_topology_change_acknowledged(br);
511                 }
512         } else if (br_is_designated_port(p)) {
513                 br_reply(p);
514         }
515 }
516 
517 /* called under bridge lock */
518 void br_received_tcn_bpdu(struct net_bridge_port *p)
519 {
520         if (br_is_designated_port(p)) {
521                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
522                         (unsigned int) p->port_no, p->dev->name);
523 
524                 br_topology_change_detection(p->br);
525                 br_topology_change_acknowledge(p);
526         }
527 }
528 
529 /* Change bridge STP parameter */
530 int br_set_hello_time(struct net_bridge *br, unsigned long val)
531 {
532         unsigned long t = clock_t_to_jiffies(val);
533 
534         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
535                 return -ERANGE;
536 
537         spin_lock_bh(&br->lock);
538         br->bridge_hello_time = t;
539         if (br_is_root_bridge(br))
540                 br->hello_time = br->bridge_hello_time;
541         spin_unlock_bh(&br->lock);
542         return 0;
543 }
544 
545 int br_set_max_age(struct net_bridge *br, unsigned long val)
546 {
547         unsigned long t = clock_t_to_jiffies(val);
548 
549         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
550                 return -ERANGE;
551 
552         spin_lock_bh(&br->lock);
553         br->bridge_max_age = t;
554         if (br_is_root_bridge(br))
555                 br->max_age = br->bridge_max_age;
556         spin_unlock_bh(&br->lock);
557         return 0;
558 
559 }
560 
561 /* called under bridge lock */
562 int __set_ageing_time(struct net_device *dev, unsigned long t)
563 {
564         struct switchdev_attr attr = {
565                 .orig_dev = dev,
566                 .id = SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME,
567                 .flags = SWITCHDEV_F_SKIP_EOPNOTSUPP | SWITCHDEV_F_DEFER,
568                 .u.ageing_time = jiffies_to_clock_t(t),
569         };
570         int err;
571 
572         err = switchdev_port_attr_set(dev, &attr);
573         if (err && err != -EOPNOTSUPP)
574                 return err;
575 
576         return 0;
577 }
578 
579 /* Set time interval that dynamic forwarding entries live
580  * For pure software bridge, allow values outside the 802.1
581  * standard specification for special cases:
582  *  0 - entry never ages (all permanant)
583  *  1 - entry disappears (no persistance)
584  *
585  * Offloaded switch entries maybe more restrictive
586  */
587 int br_set_ageing_time(struct net_bridge *br, clock_t ageing_time)
588 {
589         unsigned long t = clock_t_to_jiffies(ageing_time);
590         int err;
591 
592         err = __set_ageing_time(br->dev, t);
593         if (err)
594                 return err;
595 
596         spin_lock_bh(&br->lock);
597         br->bridge_ageing_time = t;
598         br->ageing_time = t;
599         spin_unlock_bh(&br->lock);
600 
601         mod_delayed_work(system_long_wq, &br->gc_work, 0);
602 
603         return 0;
604 }
605 
606 /* called under bridge lock */
607 void __br_set_topology_change(struct net_bridge *br, unsigned char val)
608 {
609         unsigned long t;
610         int err;
611 
612         if (br->stp_enabled == BR_KERNEL_STP && br->topology_change != val) {
613                 /* On topology change, set the bridge ageing time to twice the
614                  * forward delay. Otherwise, restore its default ageing time.
615                  */
616 
617                 if (val) {
618                         t = 2 * br->forward_delay;
619                         br_debug(br, "decreasing ageing time to %lu\n", t);
620                 } else {
621                         t = br->bridge_ageing_time;
622                         br_debug(br, "restoring ageing time to %lu\n", t);
623                 }
624 
625                 err = __set_ageing_time(br->dev, t);
626                 if (err)
627                         br_warn(br, "error offloading ageing time\n");
628                 else
629                         br->ageing_time = t;
630         }
631 
632         br->topology_change = val;
633 }
634 
635 void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
636 {
637         br->bridge_forward_delay = t;
638         if (br_is_root_bridge(br))
639                 br->forward_delay = br->bridge_forward_delay;
640 }
641 
642 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
643 {
644         unsigned long t = clock_t_to_jiffies(val);
645         int err = -ERANGE;
646 
647         spin_lock_bh(&br->lock);
648         if (br->stp_enabled != BR_NO_STP &&
649             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
650                 goto unlock;
651 
652         __br_set_forward_delay(br, t);
653         err = 0;
654 
655 unlock:
656         spin_unlock_bh(&br->lock);
657         return err;
658 }
659 

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