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 static void br_root_port_block(const struct net_bridge *br,
 104                                struct net_bridge_port *p)
 105 {
 106
 107         br_notice(br, "port %u(%s) tried to become root port (blocked)",
 108                   (unsigned int) p->port_no, p->dev->name);
 109
 110         p->state = BR_STATE_LISTENING;
 111         br_log_state(p);
 112         br_ifinfo_notify(RTM_NEWLINK, p);
 113
 114         if (br->forward_delay > 0)
 115                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 116 }
 117
 118 /* called under bridge lock */
 119 static void br_root_selection(struct net_bridge *br)
 120 {
 121         struct net_bridge_port *p;
 122         u16 root_port = 0;
 123
 124         list_for_each_entry(p, &br->port_list, list) {
 125                 if (!br_should_become_root_port(p, root_port))
 126                         continue;
 127
 128                 if (p->flags & BR_ROOT_BLOCK)
 129                         br_root_port_block(br, p);
 130                 else
 131                         root_port = p->port_no;
 132         }
 133
 134         br->root_port = root_port;
 135
 136         if (!root_port) {
 137                 br->designated_root = br->bridge_id;
 138                 br->root_path_cost = 0;
 139         } else {
 140                 p = br_get_port(br, root_port);
 141                 br->designated_root = p->designated_root;
 142                 br->root_path_cost = p->designated_cost + p->path_cost;
 143         }
 144 }
 145
 146 /* called under bridge lock */
 147 void br_become_root_bridge(struct net_bridge *br)
 148 {
 149         br->max_age = br->bridge_max_age;
 150         br->hello_time = br->bridge_hello_time;
 151         br->forward_delay = br->bridge_forward_delay;
 152         br_topology_change_detection(br);
 153         del_timer(&br->tcn_timer);
 154
 155         if (br->dev->flags & IFF_UP) {
 156                 br_config_bpdu_generation(br);
 157                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 158         }
 159 }
 160
 161 /* called under bridge lock */
 162 void br_transmit_config(struct net_bridge_port *p)
 163 {
 164         struct br_config_bpdu bpdu;
 165         struct net_bridge *br;
 166
 167         if (timer_pending(&p->hold_timer)) {
 168                 p->config_pending = 1;
 169                 return;
 170         }
 171
 172         br = p->br;
 173
 174         bpdu.topology_change = br->topology_change;
 175         bpdu.topology_change_ack = p->topology_change_ack;
 176         bpdu.root = br->designated_root;
 177         bpdu.root_path_cost = br->root_path_cost;
 178         bpdu.bridge_id = br->bridge_id;
 179         bpdu.port_id = p->port_id;
 180         if (br_is_root_bridge(br))
 181                 bpdu.message_age = 0;
 182         else {
 183                 struct net_bridge_port *root
 184                         = br_get_port(br, br->root_port);
 185                 bpdu.message_age = (jiffies - root->designated_age)
 186                         + MESSAGE_AGE_INCR;
 187         }
 188         bpdu.max_age = br->max_age;
 189         bpdu.hello_time = br->hello_time;
 190         bpdu.forward_delay = br->forward_delay;
 191
 192         if (bpdu.message_age < br->max_age) {
 193                 br_send_config_bpdu(p, &bpdu);
 194                 p->topology_change_ack = 0;
 195                 p->config_pending = 0;
 196                 mod_timer(&p->hold_timer,
 197                           round_jiffies(jiffies + BR_HOLD_TIME));
 198         }
 199 }
 200
 201 /* called under bridge lock */
 202 static void br_record_config_information(struct net_bridge_port *p,
 203                                          const struct br_config_bpdu *bpdu)
 204 {
 205         p->designated_root = bpdu->root;
 206         p->designated_cost = bpdu->root_path_cost;
 207         p->designated_bridge = bpdu->bridge_id;
 208         p->designated_port = bpdu->port_id;
 209         p->designated_age = jiffies - bpdu->message_age;
 210
 211         mod_timer(&p->message_age_timer, jiffies
 212                   + (p->br->max_age - bpdu->message_age));
 213 }
 214
 215 /* called under bridge lock */
 216 static void br_record_config_timeout_values(struct net_bridge *br,
 217                                             const struct br_config_bpdu *bpdu)
 218 {
 219         br->max_age = bpdu->max_age;
 220         br->hello_time = bpdu->hello_time;
 221         br->forward_delay = bpdu->forward_delay;
 222         br->topology_change = bpdu->topology_change;
 223 }
 224
 225 /* called under bridge lock */
 226 void br_transmit_tcn(struct net_bridge *br)
 227 {
 228         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 229 }
 230
 231 /* called under bridge lock */
 232 static int br_should_become_designated_port(const struct net_bridge_port *p)
 233 {
 234         struct net_bridge *br;
 235         int t;
 236
 237         br = p->br;
 238         if (br_is_designated_port(p))
 239                 return 1;
 240
 241         if (memcmp(&p->designated_root, &br->designated_root, 8))
 242                 return 1;
 243
 244         if (br->root_path_cost < p->designated_cost)
 245                 return 1;
 246         else if (br->root_path_cost > p->designated_cost)
 247                 return 0;
 248
 249         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 250         if (t < 0)
 251                 return 1;
 252         else if (t > 0)
 253                 return 0;
 254
 255         if (p->port_id < p->designated_port)
 256                 return 1;
 257
 258         return 0;
 259 }
 260
 261 /* called under bridge lock */
 262 static void br_designated_port_selection(struct net_bridge *br)
 263 {
 264         struct net_bridge_port *p;
 265
 266         list_for_each_entry(p, &br->port_list, list) {
 267                 if (p->state != BR_STATE_DISABLED &&
 268                     br_should_become_designated_port(p))
 269                         br_become_designated_port(p);
 270
 271         }
 272 }
 273
 274 /* called under bridge lock */
 275 static int br_supersedes_port_info(const struct net_bridge_port *p,
 276                                    const struct br_config_bpdu *bpdu)
 277 {
 278         int t;
 279
 280         t = memcmp(&bpdu->root, &p->designated_root, 8);
 281         if (t < 0)
 282                 return 1;
 283         else if (t > 0)
 284                 return 0;
 285
 286         if (bpdu->root_path_cost < p->designated_cost)
 287                 return 1;
 288         else if (bpdu->root_path_cost > p->designated_cost)
 289                 return 0;
 290
 291         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 292         if (t < 0)
 293                 return 1;
 294         else if (t > 0)
 295                 return 0;
 296
 297         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 298                 return 1;
 299
 300         if (bpdu->port_id <= p->designated_port)
 301                 return 1;
 302
 303         return 0;
 304 }
 305
 306 /* called under bridge lock */
 307 static void br_topology_change_acknowledged(struct net_bridge *br)
 308 {
 309         br->topology_change_detected = 0;
 310         del_timer(&br->tcn_timer);
 311 }
 312
 313 /* called under bridge lock */
 314 void br_topology_change_detection(struct net_bridge *br)
 315 {
 316         int isroot = br_is_root_bridge(br);
 317
 318         if (br->stp_enabled != BR_KERNEL_STP)
 319                 return;
 320
 321         br_info(br, "topology change detected, %s\n",
 322                 isroot ? "propagating" : "sending tcn bpdu");
 323
 324         if (isroot) {
 325                 br->topology_change = 1;
 326                 mod_timer(&br->topology_change_timer, jiffies
 327                           + br->bridge_forward_delay + br->bridge_max_age);
 328         } else if (!br->topology_change_detected) {
 329                 br_transmit_tcn(br);
 330                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 331         }
 332
 333         br->topology_change_detected = 1;
 334 }
 335
 336 /* called under bridge lock */
 337 void br_config_bpdu_generation(struct net_bridge *br)
 338 {
 339         struct net_bridge_port *p;
 340
 341         list_for_each_entry(p, &br->port_list, list) {
 342                 if (p->state != BR_STATE_DISABLED &&
 343                     br_is_designated_port(p))
 344                         br_transmit_config(p);
 345         }
 346 }
 347
 348 /* called under bridge lock */
 349 static void br_reply(struct net_bridge_port *p)
 350 {
 351         br_transmit_config(p);
 352 }
 353
 354 /* called under bridge lock */
 355 void br_configuration_update(struct net_bridge *br)
 356 {
 357         br_root_selection(br);
 358         br_designated_port_selection(br);
 359 }
 360
 361 /* called under bridge lock */
 362 void br_become_designated_port(struct net_bridge_port *p)
 363 {
 364         struct net_bridge *br;
 365
 366         br = p->br;
 367         p->designated_root = br->designated_root;
 368         p->designated_cost = br->root_path_cost;
 369         p->designated_bridge = br->bridge_id;
 370         p->designated_port = p->port_id;
 371 }
 372
 373
 374 /* called under bridge lock */
 375 static void br_make_blocking(struct net_bridge_port *p)
 376 {
 377         if (p->state != BR_STATE_DISABLED &&
 378             p->state != BR_STATE_BLOCKING) {
 379                 if (p->state == BR_STATE_FORWARDING ||
 380                     p->state == BR_STATE_LEARNING)
 381                         br_topology_change_detection(p->br);
 382
 383                 p->state = BR_STATE_BLOCKING;
 384                 br_log_state(p);
 385                 br_ifinfo_notify(RTM_NEWLINK, p);
 386
 387                 del_timer(&p->forward_delay_timer);
 388         }
 389 }
 390
 391 /* called under bridge lock */
 392 static void br_make_forwarding(struct net_bridge_port *p)
 393 {
 394         struct net_bridge *br = p->br;
 395
 396         if (p->state != BR_STATE_BLOCKING)
 397                 return;
 398
 399         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 400                 p->state = BR_STATE_FORWARDING;
 401                 br_topology_change_detection(br);
 402                 del_timer(&p->forward_delay_timer);
 403         } else if (br->stp_enabled == BR_KERNEL_STP)
 404                 p->state = BR_STATE_LISTENING;
 405         else
 406                 p->state = BR_STATE_LEARNING;
 407
 408         br_multicast_enable_port(p);
 409         br_log_state(p);
 410         br_ifinfo_notify(RTM_NEWLINK, p);
 411
 412         if (br->forward_delay != 0)
 413                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 414 }
 415
 416 /* called under bridge lock */
 417 void br_port_state_selection(struct net_bridge *br)
 418 {
 419         struct net_bridge_port *p;
 420         unsigned int liveports = 0;
 421
 422         list_for_each_entry(p, &br->port_list, list) {
 423                 if (p->state == BR_STATE_DISABLED)
 424                         continue;
 425
 426                 /* Don't change port states if userspace is handling STP */
 427                 if (br->stp_enabled != BR_USER_STP) {
 428                         if (p->port_no == br->root_port) {
 429                                 p->config_pending = 0;
 430                                 p->topology_change_ack = 0;
 431                                 br_make_forwarding(p);
 432                         } else if (br_is_designated_port(p)) {
 433                                 del_timer(&p->message_age_timer);
 434                                 br_make_forwarding(p);
 435                         } else {
 436                                 p->config_pending = 0;
 437                                 p->topology_change_ack = 0;
 438                                 br_make_blocking(p);
 439                         }
 440                 }
 441
 442                 if (p->state == BR_STATE_FORWARDING)
 443                         ++liveports;
 444         }
 445
 446         if (liveports == 0)
 447                 netif_carrier_off(br->dev);
 448         else
 449                 netif_carrier_on(br->dev);
 450 }
 451
 452 /* called under bridge lock */
 453 static void br_topology_change_acknowledge(struct net_bridge_port *p)
 454 {
 455         p->topology_change_ack = 1;
 456         br_transmit_config(p);
 457 }
 458
 459 /* called under bridge lock */
 460 void br_received_config_bpdu(struct net_bridge_port *p,
 461                              const struct br_config_bpdu *bpdu)
 462 {
 463         struct net_bridge *br;
 464         int was_root;
 465
 466         br = p->br;
 467         was_root = br_is_root_bridge(br);
 468
 469         if (br_supersedes_port_info(p, bpdu)) {
 470                 br_record_config_information(p, bpdu);
 471                 br_configuration_update(br);
 472                 br_port_state_selection(br);
 473
 474                 if (!br_is_root_bridge(br) && was_root) {
 475                         del_timer(&br->hello_timer);
 476                         if (br->topology_change_detected) {
 477                                 del_timer(&br->topology_change_timer);
 478                                 br_transmit_tcn(br);
 479
 480                                 mod_timer(&br->tcn_timer,
 481                                           jiffies + br->bridge_hello_time);
 482                         }
 483                 }
 484
 485                 if (p->port_no == br->root_port) {
 486                         br_record_config_timeout_values(br, bpdu);
 487                         br_config_bpdu_generation(br);
 488                         if (bpdu->topology_change_ack)
 489                                 br_topology_change_acknowledged(br);
 490                 }
 491         } else if (br_is_designated_port(p)) {
 492                 br_reply(p);
 493         }
 494 }
 495
 496 /* called under bridge lock */
 497 void br_received_tcn_bpdu(struct net_bridge_port *p)
 498 {
 499         if (br_is_designated_port(p)) {
 500                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 501                         (unsigned int) p->port_no, p->dev->name);
 502
 503                 br_topology_change_detection(p->br);
 504                 br_topology_change_acknowledge(p);
 505         }
 506 }
 507
 508 /* Change bridge STP parameter */
 509 int br_set_hello_time(struct net_bridge *br, unsigned long val)
 510 {
 511         unsigned long t = clock_t_to_jiffies(val);
 512
 513         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
 514                 return -ERANGE;
 515
 516         spin_lock_bh(&br->lock);
 517         br->bridge_hello_time = t;
 518         if (br_is_root_bridge(br))
 519                 br->hello_time = br->bridge_hello_time;
 520         spin_unlock_bh(&br->lock);
 521         return 0;
 522 }
 523
 524 int br_set_max_age(struct net_bridge *br, unsigned long val)
 525 {
 526         unsigned long t = clock_t_to_jiffies(val);
 527
 528         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
 529                 return -ERANGE;
 530
 531         spin_lock_bh(&br->lock);
 532         br->bridge_max_age = t;
 533         if (br_is_root_bridge(br))
 534                 br->max_age = br->bridge_max_age;
 535         spin_unlock_bh(&br->lock);
 536         return 0;
 537
 538 }
 539
 540 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
 541 {
 542         unsigned long t = clock_t_to_jiffies(val);
 543
 544         if (br->stp_enabled != BR_NO_STP &&
 545             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
 546                 return -ERANGE;
 547
 548         spin_lock_bh(&br->lock);
 549         br->bridge_forward_delay = t;
 550         if (br_is_root_bridge(br))
 551                 br->forward_delay = br->bridge_forward_delay;
 552         spin_unlock_bh(&br->lock);
 553         return 0;
 554 }