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  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  */
  13 #include <linux/kernel.h>
  14 #include <linux/rculist.h>
  15
  16 #include "br_private.h"
  17 #include "br_private_stp.h"
  18
  19 /* since time values in bpdu are in jiffies and then scaled (1/256)
  20  * before sending, make sure that is at least one STP tick.
  21  */
  22 #define MESSAGE_AGE_INCR        ((HZ / 256) + 1)
  23
  24 static const char *const br_port_state_names[] = {
  25         [BR_STATE_DISABLED] = "disabled",
  26         [BR_STATE_LISTENING] = "listening",
  27         [BR_STATE_LEARNING] = "learning",
  28         [BR_STATE_FORWARDING] = "forwarding",
  29         [BR_STATE_BLOCKING] = "blocking",
  30 };
  31
  32 void br_log_state(const struct net_bridge_port *p)
  33 {
  34         br_info(p->br, "port %u(%s) entered %s state\n",
  35                 (unsigned int) p->port_no, p->dev->name,
  36                 br_port_state_names[p->state]);
  37 }
  38
  39 void br_set_state(struct net_bridge_port *p, unsigned int state)
  40 {
  41         p->state = state;
  42 }
  43
  44 /* called under bridge lock */
  45 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  46 {
  47         struct net_bridge_port *p;
  48
  49         list_for_each_entry_rcu(p, &br->port_list, list) {
  50                 if (p->port_no == port_no)
  51                         return p;
  52         }
  53
  54         return NULL;
  55 }
  56
  57 /* called under bridge lock */
  58 static int br_should_become_root_port(const struct net_bridge_port *p,
  59                                       u16 root_port)
  60 {
  61         struct net_bridge *br;
  62         struct net_bridge_port *rp;
  63         int t;
  64
  65         br = p->br;
  66         if (p->state == BR_STATE_DISABLED ||
  67             br_is_designated_port(p))
  68                 return 0;
  69
  70         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  71                 return 0;
  72
  73         if (!root_port)
  74                 return 1;
  75
  76         rp = br_get_port(br, root_port);
  77
  78         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  79         if (t < 0)
  80                 return 1;
  81         else if (t > 0)
  82                 return 0;
  83
  84         if (p->designated_cost + p->path_cost <
  85             rp->designated_cost + rp->path_cost)
  86                 return 1;
  87         else if (p->designated_cost + p->path_cost >
  88                  rp->designated_cost + rp->path_cost)
  89                 return 0;
  90
  91         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  92         if (t < 0)
  93                 return 1;
  94         else if (t > 0)
  95                 return 0;
  96
  97         if (p->designated_port < rp->designated_port)
  98                 return 1;
  99         else if (p->designated_port > rp->designated_port)
 100                 return 0;
 101
 102         if (p->port_id < rp->port_id)
 103                 return 1;
 104
 105         return 0;
 106 }
 107
 108 static void br_root_port_block(const struct net_bridge *br,
 109                                struct net_bridge_port *p)
 110 {
 111
 112         br_notice(br, "port %u(%s) tried to become root port (blocked)",
 113                   (unsigned int) p->port_no, p->dev->name);
 114
 115         br_set_state(p, BR_STATE_LISTENING);
 116         br_log_state(p);
 117         br_ifinfo_notify(RTM_NEWLINK, p);
 118
 119         if (br->forward_delay > 0)
 120                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 121 }
 122
 123 /* called under bridge lock */
 124 static void br_root_selection(struct net_bridge *br)
 125 {
 126         struct net_bridge_port *p;
 127         u16 root_port = 0;
 128
 129         list_for_each_entry(p, &br->port_list, list) {
 130                 if (!br_should_become_root_port(p, root_port))
 131                         continue;
 132
 133                 if (p->flags & BR_ROOT_BLOCK)
 134                         br_root_port_block(br, p);
 135                 else
 136                         root_port = p->port_no;
 137         }
 138
 139         br->root_port = root_port;
 140
 141         if (!root_port) {
 142                 br->designated_root = br->bridge_id;
 143                 br->root_path_cost = 0;
 144         } else {
 145                 p = br_get_port(br, root_port);
 146                 br->designated_root = p->designated_root;
 147                 br->root_path_cost = p->designated_cost + p->path_cost;
 148         }
 149 }
 150
 151 /* called under bridge lock */
 152 void br_become_root_bridge(struct net_bridge *br)
 153 {
 154         br->max_age = br->bridge_max_age;
 155         br->hello_time = br->bridge_hello_time;
 156         br->forward_delay = br->bridge_forward_delay;
 157         br_topology_change_detection(br);
 158         del_timer(&br->tcn_timer);
 159
 160         if (br->dev->flags & IFF_UP) {
 161                 br_config_bpdu_generation(br);
 162                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 163         }
 164 }
 165
 166 /* called under bridge lock */
 167 void br_transmit_config(struct net_bridge_port *p)
 168 {
 169         struct br_config_bpdu bpdu;
 170         struct net_bridge *br;
 171
 172         if (timer_pending(&p->hold_timer)) {
 173                 p->config_pending = 1;
 174                 return;
 175         }
 176
 177         br = p->br;
 178
 179         bpdu.topology_change = br->topology_change;
 180         bpdu.topology_change_ack = p->topology_change_ack;
 181         bpdu.root = br->designated_root;
 182         bpdu.root_path_cost = br->root_path_cost;
 183         bpdu.bridge_id = br->bridge_id;
 184         bpdu.port_id = p->port_id;
 185         if (br_is_root_bridge(br))
 186                 bpdu.message_age = 0;
 187         else {
 188                 struct net_bridge_port *root
 189                         = br_get_port(br, br->root_port);
 190                 bpdu.message_age = (jiffies - root->designated_age)
 191                         + MESSAGE_AGE_INCR;
 192         }
 193         bpdu.max_age = br->max_age;
 194         bpdu.hello_time = br->hello_time;
 195         bpdu.forward_delay = br->forward_delay;
 196
 197         if (bpdu.message_age < br->max_age) {
 198                 br_send_config_bpdu(p, &bpdu);
 199                 p->topology_change_ack = 0;
 200                 p->config_pending = 0;
 201                 mod_timer(&p->hold_timer,
 202                           round_jiffies(jiffies + BR_HOLD_TIME));
 203         }
 204 }
 205
 206 /* called under bridge lock */
 207 static void br_record_config_information(struct net_bridge_port *p,
 208                                          const struct br_config_bpdu *bpdu)
 209 {
 210         p->designated_root = bpdu->root;
 211         p->designated_cost = bpdu->root_path_cost;
 212         p->designated_bridge = bpdu->bridge_id;
 213         p->designated_port = bpdu->port_id;
 214         p->designated_age = jiffies - bpdu->message_age;
 215
 216         mod_timer(&p->message_age_timer, jiffies
 217                   + (bpdu->max_age - bpdu->message_age));
 218 }
 219
 220 /* called under bridge lock */
 221 static void br_record_config_timeout_values(struct net_bridge *br,
 222                                             const struct br_config_bpdu *bpdu)
 223 {
 224         br->max_age = bpdu->max_age;
 225         br->hello_time = bpdu->hello_time;
 226         br->forward_delay = bpdu->forward_delay;
 227         br->topology_change = bpdu->topology_change;
 228 }
 229
 230 /* called under bridge lock */
 231 void br_transmit_tcn(struct net_bridge *br)
 232 {
 233         struct net_bridge_port *p;
 234
 235         p = br_get_port(br, br->root_port);
 236         if (p)
 237                 br_send_tcn_bpdu(p);
 238         else
 239                 br_notice(br, "root port %u not found for topology notice\n",
 240                           br->root_port);
 241 }
 242
 243 /* called under bridge lock */
 244 static int br_should_become_designated_port(const struct net_bridge_port *p)
 245 {
 246         struct net_bridge *br;
 247         int t;
 248
 249         br = p->br;
 250         if (br_is_designated_port(p))
 251                 return 1;
 252
 253         if (memcmp(&p->designated_root, &br->designated_root, 8))
 254                 return 1;
 255
 256         if (br->root_path_cost < p->designated_cost)
 257                 return 1;
 258         else if (br->root_path_cost > p->designated_cost)
 259                 return 0;
 260
 261         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 262         if (t < 0)
 263                 return 1;
 264         else if (t > 0)
 265                 return 0;
 266
 267         if (p->port_id < p->designated_port)
 268                 return 1;
 269
 270         return 0;
 271 }
 272
 273 /* called under bridge lock */
 274 static void br_designated_port_selection(struct net_bridge *br)
 275 {
 276         struct net_bridge_port *p;
 277
 278         list_for_each_entry(p, &br->port_list, list) {
 279                 if (p->state != BR_STATE_DISABLED &&
 280                     br_should_become_designated_port(p))
 281                         br_become_designated_port(p);
 282
 283         }
 284 }
 285
 286 /* called under bridge lock */
 287 static int br_supersedes_port_info(const struct net_bridge_port *p,
 288                                    const struct br_config_bpdu *bpdu)
 289 {
 290         int t;
 291
 292         t = memcmp(&bpdu->root, &p->designated_root, 8);
 293         if (t < 0)
 294                 return 1;
 295         else if (t > 0)
 296                 return 0;
 297
 298         if (bpdu->root_path_cost < p->designated_cost)
 299                 return 1;
 300         else if (bpdu->root_path_cost > p->designated_cost)
 301                 return 0;
 302
 303         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 304         if (t < 0)
 305                 return 1;
 306         else if (t > 0)
 307                 return 0;
 308
 309         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 310                 return 1;
 311
 312         if (bpdu->port_id <= p->designated_port)
 313                 return 1;
 314
 315         return 0;
 316 }
 317
 318 /* called under bridge lock */
 319 static void br_topology_change_acknowledged(struct net_bridge *br)
 320 {
 321         br->topology_change_detected = 0;
 322         del_timer(&br->tcn_timer);
 323 }
 324
 325 /* called under bridge lock */
 326 void br_topology_change_detection(struct net_bridge *br)
 327 {
 328         int isroot = br_is_root_bridge(br);
 329
 330         if (br->stp_enabled != BR_KERNEL_STP)
 331                 return;
 332
 333         br_info(br, "topology change detected, %s\n",
 334                 isroot ? "propagating" : "sending tcn bpdu");
 335
 336         if (isroot) {
 337                 br->topology_change = 1;
 338                 mod_timer(&br->topology_change_timer, jiffies
 339                           + br->bridge_forward_delay + br->bridge_max_age);
 340         } else if (!br->topology_change_detected) {
 341                 br_transmit_tcn(br);
 342                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 343         }
 344
 345         br->topology_change_detected = 1;
 346 }
 347
 348 /* called under bridge lock */
 349 void br_config_bpdu_generation(struct net_bridge *br)
 350 {
 351         struct net_bridge_port *p;
 352
 353         list_for_each_entry(p, &br->port_list, list) {
 354                 if (p->state != BR_STATE_DISABLED &&
 355                     br_is_designated_port(p))
 356                         br_transmit_config(p);
 357         }
 358 }
 359
 360 /* called under bridge lock */
 361 static void br_reply(struct net_bridge_port *p)
 362 {
 363         br_transmit_config(p);
 364 }
 365
 366 /* called under bridge lock */
 367 void br_configuration_update(struct net_bridge *br)
 368 {
 369         br_root_selection(br);
 370         br_designated_port_selection(br);
 371 }
 372
 373 /* called under bridge lock */
 374 void br_become_designated_port(struct net_bridge_port *p)
 375 {
 376         struct net_bridge *br;
 377
 378         br = p->br;
 379         p->designated_root = br->designated_root;
 380         p->designated_cost = br->root_path_cost;
 381         p->designated_bridge = br->bridge_id;
 382         p->designated_port = p->port_id;
 383 }
 384
 385
 386 /* called under bridge lock */
 387 static void br_make_blocking(struct net_bridge_port *p)
 388 {
 389         if (p->state != BR_STATE_DISABLED &&
 390             p->state != BR_STATE_BLOCKING) {
 391                 if (p->state == BR_STATE_FORWARDING ||
 392                     p->state == BR_STATE_LEARNING)
 393                         br_topology_change_detection(p->br);
 394
 395                 br_set_state(p, BR_STATE_BLOCKING);
 396                 br_log_state(p);
 397                 br_ifinfo_notify(RTM_NEWLINK, p);
 398
 399                 del_timer(&p->forward_delay_timer);
 400         }
 401 }
 402
 403 /* called under bridge lock */
 404 static void br_make_forwarding(struct net_bridge_port *p)
 405 {
 406         struct net_bridge *br = p->br;
 407
 408         if (p->state != BR_STATE_BLOCKING)
 409                 return;
 410
 411         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 412                 br_set_state(p, BR_STATE_FORWARDING);
 413                 br_topology_change_detection(br);
 414                 del_timer(&p->forward_delay_timer);
 415         } else if (br->stp_enabled == BR_KERNEL_STP)
 416                 br_set_state(p, BR_STATE_LISTENING);
 417         else
 418                 br_set_state(p, BR_STATE_LEARNING);
 419
 420         br_multicast_enable_port(p);
 421         br_log_state(p);
 422         br_ifinfo_notify(RTM_NEWLINK, p);
 423
 424         if (br->forward_delay != 0)
 425                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 426 }
 427
 428 /* called under bridge lock */
 429 void br_port_state_selection(struct net_bridge *br)
 430 {
 431         struct net_bridge_port *p;
 432         unsigned int liveports = 0;
 433
 434         list_for_each_entry(p, &br->port_list, list) {
 435                 if (p->state == BR_STATE_DISABLED)
 436                         continue;
 437
 438                 /* Don't change port states if userspace is handling STP */
 439                 if (br->stp_enabled != BR_USER_STP) {
 440                         if (p->port_no == br->root_port) {
 441                                 p->config_pending = 0;
 442                                 p->topology_change_ack = 0;
 443                                 br_make_forwarding(p);
 444                         } else if (br_is_designated_port(p)) {
 445                                 del_timer(&p->message_age_timer);
 446                                 br_make_forwarding(p);
 447                         } else {
 448                                 p->config_pending = 0;
 449                                 p->topology_change_ack = 0;
 450                                 br_make_blocking(p);
 451                         }
 452                 }
 453
 454                 if (p->state == BR_STATE_FORWARDING)
 455                         ++liveports;
 456         }
 457
 458         if (liveports == 0)
 459                 netif_carrier_off(br->dev);
 460         else
 461                 netif_carrier_on(br->dev);
 462 }
 463
 464 /* called under bridge lock */
 465 static void br_topology_change_acknowledge(struct net_bridge_port *p)
 466 {
 467         p->topology_change_ack = 1;
 468         br_transmit_config(p);
 469 }
 470
 471 /* called under bridge lock */
 472 void br_received_config_bpdu(struct net_bridge_port *p,
 473                              const struct br_config_bpdu *bpdu)
 474 {
 475         struct net_bridge *br;
 476         int was_root;
 477
 478         br = p->br;
 479         was_root = br_is_root_bridge(br);
 480
 481         if (br_supersedes_port_info(p, bpdu)) {
 482                 br_record_config_information(p, bpdu);
 483                 br_configuration_update(br);
 484                 br_port_state_selection(br);
 485
 486                 if (!br_is_root_bridge(br) && was_root) {
 487                         del_timer(&br->hello_timer);
 488                         if (br->topology_change_detected) {
 489                                 del_timer(&br->topology_change_timer);
 490                                 br_transmit_tcn(br);
 491
 492                                 mod_timer(&br->tcn_timer,
 493                                           jiffies + br->bridge_hello_time);
 494                         }
 495                 }
 496
 497                 if (p->port_no == br->root_port) {
 498                         br_record_config_timeout_values(br, bpdu);
 499                         br_config_bpdu_generation(br);
 500                         if (bpdu->topology_change_ack)
 501                                 br_topology_change_acknowledged(br);
 502                 }
 503         } else if (br_is_designated_port(p)) {
 504                 br_reply(p);
 505         }
 506 }
 507
 508 /* called under bridge lock */
 509 void br_received_tcn_bpdu(struct net_bridge_port *p)
 510 {
 511         if (br_is_designated_port(p)) {
 512                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 513                         (unsigned int) p->port_no, p->dev->name);
 514
 515                 br_topology_change_detection(p->br);
 516                 br_topology_change_acknowledge(p);
 517         }
 518 }
 519
 520 /* Change bridge STP parameter */
 521 int br_set_hello_time(struct net_bridge *br, unsigned long val)
 522 {
 523         unsigned long t = clock_t_to_jiffies(val);
 524
 525         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
 526                 return -ERANGE;
 527
 528         spin_lock_bh(&br->lock);
 529         br->bridge_hello_time = t;
 530         if (br_is_root_bridge(br))
 531                 br->hello_time = br->bridge_hello_time;
 532         spin_unlock_bh(&br->lock);
 533         return 0;
 534 }
 535
 536 int br_set_max_age(struct net_bridge *br, unsigned long val)
 537 {
 538         unsigned long t = clock_t_to_jiffies(val);
 539
 540         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
 541                 return -ERANGE;
 542
 543         spin_lock_bh(&br->lock);
 544         br->bridge_max_age = t;
 545         if (br_is_root_bridge(br))
 546                 br->max_age = br->bridge_max_age;
 547         spin_unlock_bh(&br->lock);
 548         return 0;
 549
 550 }
 551
 552 void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
 553 {
 554         br->bridge_forward_delay = t;
 555         if (br_is_root_bridge(br))
 556                 br->forward_delay = br->bridge_forward_delay;
 557 }
 558
 559 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
 560 {
 561         unsigned long t = clock_t_to_jiffies(val);
 562         int err = -ERANGE;
 563
 564         spin_lock_bh(&br->lock);
 565         if (br->stp_enabled != BR_NO_STP &&
 566             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
 567                 goto unlock;
 568
 569         __br_set_forward_delay(br, t);
 570         err = 0;
 571
 572 unlock:
 573         spin_unlock_bh(&br->lock);
 574         return err;
 575 }