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 /* called under bridge lock */
  40 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  41 {
  42         struct net_bridge_port *p;
  43
  44         list_for_each_entry_rcu(p, &br->port_list, list) {
  45                 if (p->port_no == port_no)
  46                         return p;
  47         }
  48
  49         return NULL;
  50 }
  51
  52 /* called under bridge lock */
  53 static int br_should_become_root_port(const struct net_bridge_port *p,
  54                                       u16 root_port)
  55 {
  56         struct net_bridge *br;
  57         struct net_bridge_port *rp;
  58         int t;
  59
  60         br = p->br;
  61         if (p->state == BR_STATE_DISABLED ||
  62             br_is_designated_port(p))
  63                 return 0;
  64
  65         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  66                 return 0;
  67
  68         if (!root_port)
  69                 return 1;
  70
  71         rp = br_get_port(br, root_port);
  72
  73         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  74         if (t < 0)
  75                 return 1;
  76         else if (t > 0)
  77                 return 0;
  78
  79         if (p->designated_cost + p->path_cost <
  80             rp->designated_cost + rp->path_cost)
  81                 return 1;
  82         else if (p->designated_cost + p->path_cost >
  83                  rp->designated_cost + rp->path_cost)
  84                 return 0;
  85
  86         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  87         if (t < 0)
  88                 return 1;
  89         else if (t > 0)
  90                 return 0;
  91
  92         if (p->designated_port < rp->designated_port)
  93                 return 1;
  94         else if (p->designated_port > rp->designated_port)
  95                 return 0;
  96
  97         if (p->port_id < rp->port_id)
  98                 return 1;
  99
 100         return 0;
 101 }
 102
 103 /* called under bridge lock */
 104 static void br_root_selection(struct net_bridge *br)
 105 {
 106         struct net_bridge_port *p;
 107         u16 root_port = 0;
 108
 109         list_for_each_entry(p, &br->port_list, list) {
 110                 if (br_should_become_root_port(p, root_port))
 111                         root_port = p->port_no;
 112         }
 113
 114         br->root_port = root_port;
 115
 116         if (!root_port) {
 117                 br->designated_root = br->bridge_id;
 118                 br->root_path_cost = 0;
 119         } else {
 120                 p = br_get_port(br, root_port);
 121                 br->designated_root = p->designated_root;
 122                 br->root_path_cost = p->designated_cost + p->path_cost;
 123         }
 124 }
 125
 126 /* called under bridge lock */
 127 void br_become_root_bridge(struct net_bridge *br)
 128 {
 129         br->max_age = br->bridge_max_age;
 130         br->hello_time = br->bridge_hello_time;
 131         br->forward_delay = br->bridge_forward_delay;
 132         br_topology_change_detection(br);
 133         del_timer(&br->tcn_timer);
 134
 135         if (br->dev->flags & IFF_UP) {
 136                 br_config_bpdu_generation(br);
 137                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 138         }
 139 }
 140
 141 /* called under bridge lock */
 142 void br_transmit_config(struct net_bridge_port *p)
 143 {
 144         struct br_config_bpdu bpdu;
 145         struct net_bridge *br;
 146
 147         if (timer_pending(&p->hold_timer)) {
 148                 p->config_pending = 1;
 149                 return;
 150         }
 151
 152         br = p->br;
 153
 154         bpdu.topology_change = br->topology_change;
 155         bpdu.topology_change_ack = p->topology_change_ack;
 156         bpdu.root = br->designated_root;
 157         bpdu.root_path_cost = br->root_path_cost;
 158         bpdu.bridge_id = br->bridge_id;
 159         bpdu.port_id = p->port_id;
 160         if (br_is_root_bridge(br))
 161                 bpdu.message_age = 0;
 162         else {
 163                 struct net_bridge_port *root
 164                         = br_get_port(br, br->root_port);
 165                 bpdu.message_age = (jiffies - root->designated_age)
 166                         + MESSAGE_AGE_INCR;
 167         }
 168         bpdu.max_age = br->max_age;
 169         bpdu.hello_time = br->hello_time;
 170         bpdu.forward_delay = br->forward_delay;
 171
 172         if (bpdu.message_age < br->max_age) {
 173                 br_send_config_bpdu(p, &bpdu);
 174                 p->topology_change_ack = 0;
 175                 p->config_pending = 0;
 176                 mod_timer(&p->hold_timer,
 177                           round_jiffies(jiffies + BR_HOLD_TIME));
 178         }
 179 }
 180
 181 /* called under bridge lock */
 182 static void br_record_config_information(struct net_bridge_port *p,
 183                                          const struct br_config_bpdu *bpdu)
 184 {
 185         p->designated_root = bpdu->root;
 186         p->designated_cost = bpdu->root_path_cost;
 187         p->designated_bridge = bpdu->bridge_id;
 188         p->designated_port = bpdu->port_id;
 189         p->designated_age = jiffies - bpdu->message_age;
 190
 191         mod_timer(&p->message_age_timer, jiffies
 192                   + (p->br->max_age - bpdu->message_age));
 193 }
 194
 195 /* called under bridge lock */
 196 static void br_record_config_timeout_values(struct net_bridge *br,
 197                                             const struct br_config_bpdu *bpdu)
 198 {
 199         br->max_age = bpdu->max_age;
 200         br->hello_time = bpdu->hello_time;
 201         br->forward_delay = bpdu->forward_delay;
 202         br->topology_change = bpdu->topology_change;
 203 }
 204
 205 /* called under bridge lock */
 206 void br_transmit_tcn(struct net_bridge *br)
 207 {
 208         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 209 }
 210
 211 /* called under bridge lock */
 212 static int br_should_become_designated_port(const struct net_bridge_port *p)
 213 {
 214         struct net_bridge *br;
 215         int t;
 216
 217         br = p->br;
 218         if (br_is_designated_port(p))
 219                 return 1;
 220
 221         if (memcmp(&p->designated_root, &br->designated_root, 8))
 222                 return 1;
 223
 224         if (br->root_path_cost < p->designated_cost)
 225                 return 1;
 226         else if (br->root_path_cost > p->designated_cost)
 227                 return 0;
 228
 229         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 230         if (t < 0)
 231                 return 1;
 232         else if (t > 0)
 233                 return 0;
 234
 235         if (p->port_id < p->designated_port)
 236                 return 1;
 237
 238         return 0;
 239 }
 240
 241 /* called under bridge lock */
 242 static void br_designated_port_selection(struct net_bridge *br)
 243 {
 244         struct net_bridge_port *p;
 245
 246         list_for_each_entry(p, &br->port_list, list) {
 247                 if (p->state != BR_STATE_DISABLED &&
 248                     br_should_become_designated_port(p))
 249                         br_become_designated_port(p);
 250
 251         }
 252 }
 253
 254 /* called under bridge lock */
 255 static int br_supersedes_port_info(const struct net_bridge_port *p,
 256                                    const struct br_config_bpdu *bpdu)
 257 {
 258         int t;
 259
 260         t = memcmp(&bpdu->root, &p->designated_root, 8);
 261         if (t < 0)
 262                 return 1;
 263         else if (t > 0)
 264                 return 0;
 265
 266         if (bpdu->root_path_cost < p->designated_cost)
 267                 return 1;
 268         else if (bpdu->root_path_cost > p->designated_cost)
 269                 return 0;
 270
 271         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 272         if (t < 0)
 273                 return 1;
 274         else if (t > 0)
 275                 return 0;
 276
 277         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 278                 return 1;
 279
 280         if (bpdu->port_id <= p->designated_port)
 281                 return 1;
 282
 283         return 0;
 284 }
 285
 286 /* called under bridge lock */
 287 static void br_topology_change_acknowledged(struct net_bridge *br)
 288 {
 289         br->topology_change_detected = 0;
 290         del_timer(&br->tcn_timer);
 291 }
 292
 293 /* called under bridge lock */
 294 void br_topology_change_detection(struct net_bridge *br)
 295 {
 296         int isroot = br_is_root_bridge(br);
 297
 298         if (br->stp_enabled != BR_KERNEL_STP)
 299                 return;
 300
 301         br_info(br, "topology change detected, %s\n",
 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 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                 br_ifinfo_notify(RTM_NEWLINK, p);
 366
 367                 del_timer(&p->forward_delay_timer);
 368         }
 369 }
 370
 371 /* called under bridge lock */
 372 static void br_make_forwarding(struct net_bridge_port *p)
 373 {
 374         struct net_bridge *br = p->br;
 375
 376         if (p->state != BR_STATE_BLOCKING)
 377                 return;
 378
 379         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 380                 p->state = BR_STATE_FORWARDING;
 381                 br_topology_change_detection(br);
 382                 del_timer(&p->forward_delay_timer);
 383         } else if (br->stp_enabled == BR_KERNEL_STP)
 384                 p->state = BR_STATE_LISTENING;
 385         else
 386                 p->state = BR_STATE_LEARNING;
 387
 388         br_multicast_enable_port(p);
 389         br_log_state(p);
 390         br_ifinfo_notify(RTM_NEWLINK, p);
 391
 392         if (br->forward_delay != 0)
 393                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 394 }
 395
 396 /* called under bridge lock */
 397 void br_port_state_selection(struct net_bridge *br)
 398 {
 399         struct net_bridge_port *p;
 400         unsigned int liveports = 0;
 401
 402         list_for_each_entry(p, &br->port_list, list) {
 403                 if (p->state == BR_STATE_DISABLED)
 404                         continue;
 405
 406                 /* Don't change port states if userspace is handling STP */
 407                 if (br->stp_enabled != BR_USER_STP) {
 408                         if (p->port_no == br->root_port) {
 409                                 p->config_pending = 0;
 410                                 p->topology_change_ack = 0;
 411                                 br_make_forwarding(p);
 412                         } else if (br_is_designated_port(p)) {
 413                                 del_timer(&p->message_age_timer);
 414                                 br_make_forwarding(p);
 415                         } else {
 416                                 p->config_pending = 0;
 417                                 p->topology_change_ack = 0;
 418                                 br_make_blocking(p);
 419                         }
 420                 }
 421
 422                 if (p->state == BR_STATE_FORWARDING)
 423                         ++liveports;
 424         }
 425
 426         if (liveports == 0)
 427                 netif_carrier_off(br->dev);
 428         else
 429                 netif_carrier_on(br->dev);
 430 }
 431
 432 /* called under bridge lock */
 433 static void br_topology_change_acknowledge(struct net_bridge_port *p)
 434 {
 435         p->topology_change_ack = 1;
 436         br_transmit_config(p);
 437 }
 438
 439 /* called under bridge lock */
 440 void br_received_config_bpdu(struct net_bridge_port *p,
 441                              const struct br_config_bpdu *bpdu)
 442 {
 443         struct net_bridge *br;
 444         int was_root;
 445
 446         br = p->br;
 447         was_root = br_is_root_bridge(br);
 448
 449         if (br_supersedes_port_info(p, bpdu)) {
 450                 br_record_config_information(p, bpdu);
 451                 br_configuration_update(br);
 452                 br_port_state_selection(br);
 453
 454                 if (!br_is_root_bridge(br) && was_root) {
 455                         del_timer(&br->hello_timer);
 456                         if (br->topology_change_detected) {
 457                                 del_timer(&br->topology_change_timer);
 458                                 br_transmit_tcn(br);
 459
 460                                 mod_timer(&br->tcn_timer,
 461                                           jiffies + br->bridge_hello_time);
 462                         }
 463                 }
 464
 465                 if (p->port_no == br->root_port) {
 466                         br_record_config_timeout_values(br, bpdu);
 467                         br_config_bpdu_generation(br);
 468                         if (bpdu->topology_change_ack)
 469                                 br_topology_change_acknowledged(br);
 470                 }
 471         } else if (br_is_designated_port(p)) {
 472                 br_reply(p);
 473         }
 474 }
 475
 476 /* called under bridge lock */
 477 void br_received_tcn_bpdu(struct net_bridge_port *p)
 478 {
 479         if (br_is_designated_port(p)) {
 480                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 481                         (unsigned int) p->port_no, p->dev->name);
 482
 483                 br_topology_change_detection(p->br);
 484                 br_topology_change_acknowledge(p);
 485         }
 486 }
 487
 488 /* Change bridge STP parameter */
 489 int br_set_hello_time(struct net_bridge *br, unsigned long val)
 490 {
 491         unsigned long t = clock_t_to_jiffies(val);
 492
 493         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
 494                 return -ERANGE;
 495
 496         spin_lock_bh(&br->lock);
 497         br->bridge_hello_time = t;
 498         if (br_is_root_bridge(br))
 499                 br->hello_time = br->bridge_hello_time;
 500         spin_unlock_bh(&br->lock);
 501         return 0;
 502 }
 503
 504 int br_set_max_age(struct net_bridge *br, unsigned long val)
 505 {
 506         unsigned long t = clock_t_to_jiffies(val);
 507
 508         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
 509                 return -ERANGE;
 510
 511         spin_lock_bh(&br->lock);
 512         br->bridge_max_age = t;
 513         if (br_is_root_bridge(br))
 514                 br->max_age = br->bridge_max_age;
 515         spin_unlock_bh(&br->lock);
 516         return 0;
 517
 518 }
 519
 520 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
 521 {
 522         unsigned long t = clock_t_to_jiffies(val);
 523
 524         if (br->stp_enabled != BR_NO_STP &&
 525             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
 526                 return -ERANGE;
 527
 528         spin_lock_bh(&br->lock);
 529         br->bridge_forward_delay = t;
 530         if (br_is_root_bridge(br))
 531                 br->forward_delay = br->bridge_forward_delay;
 532         spin_unlock_bh(&br->lock);
 533         return 0;
 534 }