net/bridge/br_stp.c

   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         /* Don't change the state of the ports if they are driven by a different
  40          * protocol.
  41          */
  42         if (p->flags & BR_MRP_AWARE)
  43                 return;
  44
  45         p->state = state;
  46         err = switchdev_port_attr_set(p->dev, &attr);
  47         if (err && err != -EOPNOTSUPP)
  48                 br_warn(p->br, "error setting offload STP state on port %u(%s)\n",
  49                                 (unsigned int) p->port_no, p->dev->name);
  50         else
  51                 br_info(p->br, "port %u(%s) entered %s state\n",
  52                                 (unsigned int) p->port_no, p->dev->name,
  53                                 br_port_state_names[p->state]);
  54
  55         if (p->br->stp_enabled == BR_KERNEL_STP) {
  56                 switch (p->state) {
  57                 case BR_STATE_BLOCKING:
  58                         p->stp_xstats.transition_blk++;
  59                         break;
  60                 case BR_STATE_FORWARDING:
  61                         p->stp_xstats.transition_fwd++;
  62                         break;
  63                 }
  64         }
  65 }
  66
  67 /* called under bridge lock */
  68 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  69 {
  70         struct net_bridge_port *p;
  71
  72         list_for_each_entry_rcu(p, &br->port_list, list,
  73                                 lockdep_is_held(&br->lock)) {
  74                 if (p->port_no == port_no)
  75                         return p;
  76         }
  77
  78         return NULL;
  79 }
  80
  81 /* called under bridge lock */
  82 static int br_should_become_root_port(const struct net_bridge_port *p,
  83                                       u16 root_port)
  84 {
  85         struct net_bridge *br;
  86         struct net_bridge_port *rp;
  87         int t;
  88
  89         br = p->br;
  90         if (p->state == BR_STATE_DISABLED ||
  91             br_is_designated_port(p))
  92                 return 0;
  93
  94         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  95                 return 0;
  96
  97         if (!root_port)
  98                 return 1;
  99
 100         rp = br_get_port(br, root_port);
 101
 102         t = memcmp(&p->designated_root, &rp->designated_root, 8);
 103         if (t < 0)
 104                 return 1;
 105         else if (t > 0)
 106                 return 0;
 107
 108         if (p->designated_cost + p->path_cost <
 109             rp->designated_cost + rp->path_cost)
 110                 return 1;
 111         else if (p->designated_cost + p->path_cost >
 112                  rp->designated_cost + rp->path_cost)
 113                 return 0;
 114
 115         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
 116         if (t < 0)
 117                 return 1;
 118         else if (t > 0)
 119                 return 0;
 120
 121         if (p->designated_port < rp->designated_port)
 122                 return 1;
 123         else if (p->designated_port > rp->designated_port)
 124                 return 0;
 125
 126         if (p->port_id < rp->port_id)
 127                 return 1;
 128
 129         return 0;
 130 }
 131
 132 static void br_root_port_block(const struct net_bridge *br,
 133                                struct net_bridge_port *p)
 134 {
 135
 136         br_notice(br, "port %u(%s) tried to become root port (blocked)",
 137                   (unsigned int) p->port_no, p->dev->name);
 138
 139         br_set_state(p, BR_STATE_LISTENING);
 140         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 141
 142         if (br->forward_delay > 0)
 143                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 144 }
 145
 146 /* called under bridge lock */
 147 static void br_root_selection(struct net_bridge *br)
 148 {
 149         struct net_bridge_port *p;
 150         u16 root_port = 0;
 151
 152         list_for_each_entry(p, &br->port_list, list) {
 153                 if (!br_should_become_root_port(p, root_port))
 154                         continue;
 155
 156                 if (p->flags & BR_ROOT_BLOCK)
 157                         br_root_port_block(br, p);
 158                 else
 159                         root_port = p->port_no;
 160         }
 161
 162         br->root_port = root_port;
 163
 164         if (!root_port) {
 165                 br->designated_root = br->bridge_id;
 166                 br->root_path_cost = 0;
 167         } else {
 168                 p = br_get_port(br, root_port);
 169                 br->designated_root = p->designated_root;
 170                 br->root_path_cost = p->designated_cost + p->path_cost;
 171         }
 172 }
 173
 174 /* called under bridge lock */
 175 void br_become_root_bridge(struct net_bridge *br)
 176 {
 177         br->max_age = br->bridge_max_age;
 178         br->hello_time = br->bridge_hello_time;
 179         br->forward_delay = br->bridge_forward_delay;
 180         br_topology_change_detection(br);
 181         del_timer(&br->tcn_timer);
 182
 183         if (br->dev->flags & IFF_UP) {
 184                 br_config_bpdu_generation(br);
 185                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 186         }
 187 }
 188
 189 /* called under bridge lock */
 190 void br_transmit_config(struct net_bridge_port *p)
 191 {
 192         struct br_config_bpdu bpdu;
 193         struct net_bridge *br;
 194
 195         if (timer_pending(&p->hold_timer)) {
 196                 p->config_pending = 1;
 197                 return;
 198         }
 199
 200         br = p->br;
 201
 202         bpdu.topology_change = br->topology_change;
 203         bpdu.topology_change_ack = p->topology_change_ack;
 204         bpdu.root = br->designated_root;
 205         bpdu.root_path_cost = br->root_path_cost;
 206         bpdu.bridge_id = br->bridge_id;
 207         bpdu.port_id = p->port_id;
 208         if (br_is_root_bridge(br))
 209                 bpdu.message_age = 0;
 210         else {
 211                 struct net_bridge_port *root
 212                         = br_get_port(br, br->root_port);
 213                 bpdu.message_age = (jiffies - root->designated_age)
 214                         + MESSAGE_AGE_INCR;
 215         }
 216         bpdu.max_age = br->max_age;
 217         bpdu.hello_time = br->hello_time;
 218         bpdu.forward_delay = br->forward_delay;
 219
 220         if (bpdu.message_age < br->max_age) {
 221                 br_send_config_bpdu(p, &bpdu);
 222                 p->topology_change_ack = 0;
 223                 p->config_pending = 0;
 224                 if (p->br->stp_enabled == BR_KERNEL_STP)
 225                         mod_timer(&p->hold_timer,
 226                                   round_jiffies(jiffies + BR_HOLD_TIME));
 227         }
 228 }
 229
 230 /* called under bridge lock */
 231 static void br_record_config_information(struct net_bridge_port *p,
 232                                          const struct br_config_bpdu *bpdu)
 233 {
 234         p->designated_root = bpdu->root;
 235         p->designated_cost = bpdu->root_path_cost;
 236         p->designated_bridge = bpdu->bridge_id;
 237         p->designated_port = bpdu->port_id;
 238         p->designated_age = jiffies - bpdu->message_age;
 239
 240         mod_timer(&p->message_age_timer, jiffies
 241                   + (bpdu->max_age - bpdu->message_age));
 242 }
 243
 244 /* called under bridge lock */
 245 static void br_record_config_timeout_values(struct net_bridge *br,
 246                                             const struct br_config_bpdu *bpdu)
 247 {
 248         br->max_age = bpdu->max_age;
 249         br->hello_time = bpdu->hello_time;
 250         br->forward_delay = bpdu->forward_delay;
 251         __br_set_topology_change(br, bpdu->topology_change);
 252 }
 253
 254 /* called under bridge lock */
 255 void br_transmit_tcn(struct net_bridge *br)
 256 {
 257         struct net_bridge_port *p;
 258
 259         p = br_get_port(br, br->root_port);
 260         if (p)
 261                 br_send_tcn_bpdu(p);
 262         else
 263                 br_notice(br, "root port %u not found for topology notice\n",
 264                           br->root_port);
 265 }
 266
 267 /* called under bridge lock */
 268 static int br_should_become_designated_port(const struct net_bridge_port *p)
 269 {
 270         struct net_bridge *br;
 271         int t;
 272
 273         br = p->br;
 274         if (br_is_designated_port(p))
 275                 return 1;
 276
 277         if (memcmp(&p->designated_root, &br->designated_root, 8))
 278                 return 1;
 279
 280         if (br->root_path_cost < p->designated_cost)
 281                 return 1;
 282         else if (br->root_path_cost > p->designated_cost)
 283                 return 0;
 284
 285         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 286         if (t < 0)
 287                 return 1;
 288         else if (t > 0)
 289                 return 0;
 290
 291         if (p->port_id < p->designated_port)
 292                 return 1;
 293
 294         return 0;
 295 }
 296
 297 /* called under bridge lock */
 298 static void br_designated_port_selection(struct net_bridge *br)
 299 {
 300         struct net_bridge_port *p;
 301
 302         list_for_each_entry(p, &br->port_list, list) {
 303                 if (p->state != BR_STATE_DISABLED &&
 304                     br_should_become_designated_port(p))
 305                         br_become_designated_port(p);
 306
 307         }
 308 }
 309
 310 /* called under bridge lock */
 311 static int br_supersedes_port_info(const struct net_bridge_port *p,
 312                                    const struct br_config_bpdu *bpdu)
 313 {
 314         int t;
 315
 316         t = memcmp(&bpdu->root, &p->designated_root, 8);
 317         if (t < 0)
 318                 return 1;
 319         else if (t > 0)
 320                 return 0;
 321
 322         if (bpdu->root_path_cost < p->designated_cost)
 323                 return 1;
 324         else if (bpdu->root_path_cost > p->designated_cost)
 325                 return 0;
 326
 327         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 328         if (t < 0)
 329                 return 1;
 330         else if (t > 0)
 331                 return 0;
 332
 333         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 334                 return 1;
 335
 336         if (bpdu->port_id <= p->designated_port)
 337                 return 1;
 338
 339         return 0;
 340 }
 341
 342 /* called under bridge lock */
 343 static void br_topology_change_acknowledged(struct net_bridge *br)
 344 {
 345         br->topology_change_detected = 0;
 346         del_timer(&br->tcn_timer);
 347 }
 348
 349 /* called under bridge lock */
 350 void br_topology_change_detection(struct net_bridge *br)
 351 {
 352         int isroot = br_is_root_bridge(br);
 353
 354         if (br->stp_enabled != BR_KERNEL_STP)
 355                 return;
 356
 357         br_info(br, "topology change detected, %s\n",
 358                 isroot ? "propagating" : "sending tcn bpdu");
 359
 360         if (isroot) {
 361                 __br_set_topology_change(br, 1);
 362                 mod_timer(&br->topology_change_timer, jiffies
 363                           + br->bridge_forward_delay + br->bridge_max_age);
 364         } else if (!br->topology_change_detected) {
 365                 br_transmit_tcn(br);
 366                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 367         }
 368
 369         br->topology_change_detected = 1;
 370 }
 371
 372 /* called under bridge lock */
 373 void br_config_bpdu_generation(struct net_bridge *br)
 374 {
 375         struct net_bridge_port *p;
 376
 377         list_for_each_entry(p, &br->port_list, list) {
 378                 if (p->state != BR_STATE_DISABLED &&
 379                     br_is_designated_port(p))
 380                         br_transmit_config(p);
 381         }
 382 }
 383
 384 /* called under bridge lock */
 385 static void br_reply(struct net_bridge_port *p)
 386 {
 387         br_transmit_config(p);
 388 }
 389
 390 /* called under bridge lock */
 391 void br_configuration_update(struct net_bridge *br)
 392 {
 393         br_root_selection(br);
 394         br_designated_port_selection(br);
 395 }
 396
 397 /* called under bridge lock */
 398 void br_become_designated_port(struct net_bridge_port *p)
 399 {
 400         struct net_bridge *br;
 401
 402         br = p->br;
 403         p->designated_root = br->designated_root;
 404         p->designated_cost = br->root_path_cost;
 405         p->designated_bridge = br->bridge_id;
 406         p->designated_port = p->port_id;
 407 }
 408
 409
 410 /* called under bridge lock */
 411 static void br_make_blocking(struct net_bridge_port *p)
 412 {
 413         if (p->state != BR_STATE_DISABLED &&
 414             p->state != BR_STATE_BLOCKING) {
 415                 if (p->state == BR_STATE_FORWARDING ||
 416                     p->state == BR_STATE_LEARNING)
 417                         br_topology_change_detection(p->br);
 418
 419                 br_set_state(p, BR_STATE_BLOCKING);
 420                 br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 421
 422                 del_timer(&p->forward_delay_timer);
 423         }
 424 }
 425
 426 /* called under bridge lock */
 427 static void br_make_forwarding(struct net_bridge_port *p)
 428 {
 429         struct net_bridge *br = p->br;
 430
 431         if (p->state != BR_STATE_BLOCKING)
 432                 return;
 433
 434         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 435                 br_set_state(p, BR_STATE_FORWARDING);
 436                 br_topology_change_detection(br);
 437                 del_timer(&p->forward_delay_timer);
 438         } else if (br->stp_enabled == BR_KERNEL_STP)
 439                 br_set_state(p, BR_STATE_LISTENING);
 440         else
 441                 br_set_state(p, BR_STATE_LEARNING);
 442
 443         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 444
 445         if (br->forward_delay != 0)
 446                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 447 }
 448
 449 /* called under bridge lock */
 450 void br_port_state_selection(struct net_bridge *br)
 451 {
 452         struct net_bridge_port *p;
 453         unsigned int liveports = 0;
 454
 455         list_for_each_entry(p, &br->port_list, list) {
 456                 if (p->state == BR_STATE_DISABLED)
 457                         continue;
 458
 459                 /* Don't change port states if userspace is handling STP */
 460                 if (br->stp_enabled != BR_USER_STP) {
 461                         if (p->port_no == br->root_port) {
 462                                 p->config_pending = 0;
 463                                 p->topology_change_ack = 0;
 464                                 br_make_forwarding(p);
 465                         } else if (br_is_designated_port(p)) {
 466                                 del_timer(&p->message_age_timer);
 467                                 br_make_forwarding(p);
 468                         } else {
 469                                 p->config_pending = 0;
 470                                 p->topology_change_ack = 0;
 471                                 br_make_blocking(p);
 472                         }
 473                 }
 474
 475                 if (p->state != BR_STATE_BLOCKING)
 476                         br_multicast_enable_port(p);
 477                 /* Multicast is not disabled for the port when it goes in
 478                  * blocking state because the timers will expire and stop by
 479                  * themselves without sending more queries.
 480                  */
 481                 if (p->state == BR_STATE_FORWARDING)
 482                         ++liveports;
 483         }
 484
 485         if (liveports == 0)
 486                 netif_carrier_off(br->dev);
 487         else
 488                 netif_carrier_on(br->dev);
 489 }
 490
 491 /* called under bridge lock */
 492 static void br_topology_change_acknowledge(struct net_bridge_port *p)
 493 {
 494         p->topology_change_ack = 1;
 495         br_transmit_config(p);
 496 }
 497
 498 /* called under bridge lock */
 499 void br_received_config_bpdu(struct net_bridge_port *p,
 500                              const struct br_config_bpdu *bpdu)
 501 {
 502         struct net_bridge *br;
 503         int was_root;
 504
 505         p->stp_xstats.rx_bpdu++;
 506
 507         br = p->br;
 508         was_root = br_is_root_bridge(br);
 509
 510         if (br_supersedes_port_info(p, bpdu)) {
 511                 br_record_config_information(p, bpdu);
 512                 br_configuration_update(br);
 513                 br_port_state_selection(br);
 514
 515                 if (!br_is_root_bridge(br) && was_root) {
 516                         del_timer(&br->hello_timer);
 517                         if (br->topology_change_detected) {
 518                                 del_timer(&br->topology_change_timer);
 519                                 br_transmit_tcn(br);
 520
 521                                 mod_timer(&br->tcn_timer,
 522                                           jiffies + br->bridge_hello_time);
 523                         }
 524                 }
 525
 526                 if (p->port_no == br->root_port) {
 527                         br_record_config_timeout_values(br, bpdu);
 528                         br_config_bpdu_generation(br);
 529                         if (bpdu->topology_change_ack)
 530                                 br_topology_change_acknowledged(br);
 531                 }
 532         } else if (br_is_designated_port(p)) {
 533                 br_reply(p);
 534         }
 535 }
 536
 537 /* called under bridge lock */
 538 void br_received_tcn_bpdu(struct net_bridge_port *p)
 539 {
 540         p->stp_xstats.rx_tcn++;
 541
 542         if (br_is_designated_port(p)) {
 543                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 544                         (unsigned int) p->port_no, p->dev->name);
 545
 546                 br_topology_change_detection(p->br);
 547                 br_topology_change_acknowledge(p);
 548         }
 549 }
 550
 551 /* Change bridge STP parameter */
 552 int br_set_hello_time(struct net_bridge *br, unsigned long val)
 553 {
 554         unsigned long t = clock_t_to_jiffies(val);
 555
 556         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
 557                 return -ERANGE;
 558
 559         spin_lock_bh(&br->lock);
 560         br->bridge_hello_time = t;
 561         if (br_is_root_bridge(br))
 562                 br->hello_time = br->bridge_hello_time;
 563         spin_unlock_bh(&br->lock);
 564         return 0;
 565 }
 566
 567 int br_set_max_age(struct net_bridge *br, unsigned long val)
 568 {
 569         unsigned long t = clock_t_to_jiffies(val);
 570
 571         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
 572                 return -ERANGE;
 573
 574         spin_lock_bh(&br->lock);
 575         br->bridge_max_age = t;
 576         if (br_is_root_bridge(br))
 577                 br->max_age = br->bridge_max_age;
 578         spin_unlock_bh(&br->lock);
 579         return 0;
 580
 581 }
 582
 583 /* called under bridge lock */
 584 int __set_ageing_time(struct net_device *dev, unsigned long t)
 585 {
 586         struct switchdev_attr attr = {
 587                 .orig_dev = dev,
 588                 .id = SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME,
 589                 .flags = SWITCHDEV_F_SKIP_EOPNOTSUPP | SWITCHDEV_F_DEFER,
 590                 .u.ageing_time = jiffies_to_clock_t(t),
 591         };
 592         int err;
 593
 594         err = switchdev_port_attr_set(dev, &attr);
 595         if (err && err != -EOPNOTSUPP)
 596                 return err;
 597
 598         return 0;
 599 }
 600
 601 /* Set time interval that dynamic forwarding entries live
 602  * For pure software bridge, allow values outside the 802.1
 603  * standard specification for special cases:
 604  *  0 - entry never ages (all permanant)
 605  *  1 - entry disappears (no persistance)
 606  *
 607  * Offloaded switch entries maybe more restrictive
 608  */
 609 int br_set_ageing_time(struct net_bridge *br, clock_t ageing_time)
 610 {
 611         unsigned long t = clock_t_to_jiffies(ageing_time);
 612         int err;
 613
 614         err = __set_ageing_time(br->dev, t);
 615         if (err)
 616                 return err;
 617
 618         spin_lock_bh(&br->lock);
 619         br->bridge_ageing_time = t;
 620         br->ageing_time = t;
 621         spin_unlock_bh(&br->lock);
 622
 623         mod_delayed_work(system_long_wq, &br->gc_work, 0);
 624
 625         return 0;
 626 }
 627
 628 /* called under bridge lock */
 629 void __br_set_topology_change(struct net_bridge *br, unsigned char val)
 630 {
 631         unsigned long t;
 632         int err;
 633
 634         if (br->stp_enabled == BR_KERNEL_STP && br->topology_change != val) {
 635                 /* On topology change, set the bridge ageing time to twice the
 636                  * forward delay. Otherwise, restore its default ageing time.
 637                  */
 638
 639                 if (val) {
 640                         t = 2 * br->forward_delay;
 641                         br_debug(br, "decreasing ageing time to %lu\n", t);
 642                 } else {
 643                         t = br->bridge_ageing_time;
 644                         br_debug(br, "restoring ageing time to %lu\n", t);
 645                 }
 646
 647                 err = __set_ageing_time(br->dev, t);
 648                 if (err)
 649                         br_warn(br, "error offloading ageing time\n");
 650                 else
 651                         br->ageing_time = t;
 652         }
 653
 654         br->topology_change = val;
 655 }
 656
 657 void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
 658 {
 659         br->bridge_forward_delay = t;
 660         if (br_is_root_bridge(br))
 661                 br->forward_delay = br->bridge_forward_delay;
 662 }
 663
 664 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
 665 {
 666         unsigned long t = clock_t_to_jiffies(val);
 667         int err = -ERANGE;
 668
 669         spin_lock_bh(&br->lock);
 670         if (br->stp_enabled != BR_NO_STP &&
 671             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
 672                 goto unlock;
 673
 674         __br_set_forward_delay(br, t);
 675         err = 0;
 676
 677 unlock:
 678         spin_unlock_bh(&br->lock);
 679         return err;
 680 }