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, NULL);
  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 u8 br_port_get_stp_state(const struct net_device *dev)
  68 {
  69         struct net_bridge_port *p;
  70
  71         ASSERT_RTNL();
  72
  73         p = br_port_get_rtnl(dev);
  74         if (!p)
  75                 return BR_STATE_DISABLED;
  76
  77         return p->state;
  78 }
  79 EXPORT_SYMBOL_GPL(br_port_get_stp_state);
  80
  81 /* called under bridge lock */
  82 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  83 {
  84         struct net_bridge_port *p;
  85
  86         list_for_each_entry_rcu(p, &br->port_list, list,
  87                                 lockdep_is_held(&br->lock)) {
  88                 if (p->port_no == port_no)
  89                         return p;
  90         }
  91
  92         return NULL;
  93 }
  94
  95 /* called under bridge lock */
  96 static int br_should_become_root_port(const struct net_bridge_port *p,
  97                                       u16 root_port)
  98 {
  99         struct net_bridge *br;
 100         struct net_bridge_port *rp;
 101         int t;
 102
 103         br = p->br;
 104         if (p->state == BR_STATE_DISABLED ||
 105             br_is_designated_port(p))
 106                 return 0;
 107
 108         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
 109                 return 0;
 110
 111         if (!root_port)
 112                 return 1;
 113
 114         rp = br_get_port(br, root_port);
 115
 116         t = memcmp(&p->designated_root, &rp->designated_root, 8);
 117         if (t < 0)
 118                 return 1;
 119         else if (t > 0)
 120                 return 0;
 121
 122         if (p->designated_cost + p->path_cost <
 123             rp->designated_cost + rp->path_cost)
 124                 return 1;
 125         else if (p->designated_cost + p->path_cost >
 126                  rp->designated_cost + rp->path_cost)
 127                 return 0;
 128
 129         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
 130         if (t < 0)
 131                 return 1;
 132         else if (t > 0)
 133                 return 0;
 134
 135         if (p->designated_port < rp->designated_port)
 136                 return 1;
 137         else if (p->designated_port > rp->designated_port)
 138                 return 0;
 139
 140         if (p->port_id < rp->port_id)
 141                 return 1;
 142
 143         return 0;
 144 }
 145
 146 static void br_root_port_block(const struct net_bridge *br,
 147                                struct net_bridge_port *p)
 148 {
 149
 150         br_notice(br, "port %u(%s) tried to become root port (blocked)",
 151                   (unsigned int) p->port_no, p->dev->name);
 152
 153         br_set_state(p, BR_STATE_LISTENING);
 154         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 155
 156         if (br->forward_delay > 0)
 157                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 158 }
 159
 160 /* called under bridge lock */
 161 static void br_root_selection(struct net_bridge *br)
 162 {
 163         struct net_bridge_port *p;
 164         u16 root_port = 0;
 165
 166         list_for_each_entry(p, &br->port_list, list) {
 167                 if (!br_should_become_root_port(p, root_port))
 168                         continue;
 169
 170                 if (p->flags & BR_ROOT_BLOCK)
 171                         br_root_port_block(br, p);
 172                 else
 173                         root_port = p->port_no;
 174         }
 175
 176         br->root_port = root_port;
 177
 178         if (!root_port) {
 179                 br->designated_root = br->bridge_id;
 180                 br->root_path_cost = 0;
 181         } else {
 182                 p = br_get_port(br, root_port);
 183                 br->designated_root = p->designated_root;
 184                 br->root_path_cost = p->designated_cost + p->path_cost;
 185         }
 186 }
 187
 188 /* called under bridge lock */
 189 void br_become_root_bridge(struct net_bridge *br)
 190 {
 191         br->max_age = br->bridge_max_age;
 192         br->hello_time = br->bridge_hello_time;
 193         br->forward_delay = br->bridge_forward_delay;
 194         br_topology_change_detection(br);
 195         del_timer(&br->tcn_timer);
 196
 197         if (br->dev->flags & IFF_UP) {
 198                 br_config_bpdu_generation(br);
 199                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 200         }
 201 }
 202
 203 /* called under bridge lock */
 204 void br_transmit_config(struct net_bridge_port *p)
 205 {
 206         struct br_config_bpdu bpdu;
 207         struct net_bridge *br;
 208
 209         if (timer_pending(&p->hold_timer)) {
 210                 p->config_pending = 1;
 211                 return;
 212         }
 213
 214         br = p->br;
 215
 216         bpdu.topology_change = br->topology_change;
 217         bpdu.topology_change_ack = p->topology_change_ack;
 218         bpdu.root = br->designated_root;
 219         bpdu.root_path_cost = br->root_path_cost;
 220         bpdu.bridge_id = br->bridge_id;
 221         bpdu.port_id = p->port_id;
 222         if (br_is_root_bridge(br))
 223                 bpdu.message_age = 0;
 224         else {
 225                 struct net_bridge_port *root
 226                         = br_get_port(br, br->root_port);
 227                 bpdu.message_age = (jiffies - root->designated_age)
 228                         + MESSAGE_AGE_INCR;
 229         }
 230         bpdu.max_age = br->max_age;
 231         bpdu.hello_time = br->hello_time;
 232         bpdu.forward_delay = br->forward_delay;
 233
 234         if (bpdu.message_age < br->max_age) {
 235                 br_send_config_bpdu(p, &bpdu);
 236                 p->topology_change_ack = 0;
 237                 p->config_pending = 0;
 238                 if (p->br->stp_enabled == BR_KERNEL_STP)
 239                         mod_timer(&p->hold_timer,
 240                                   round_jiffies(jiffies + BR_HOLD_TIME));
 241         }
 242 }
 243
 244 /* called under bridge lock */
 245 static void br_record_config_information(struct net_bridge_port *p,
 246                                          const struct br_config_bpdu *bpdu)
 247 {
 248         p->designated_root = bpdu->root;
 249         p->designated_cost = bpdu->root_path_cost;
 250         p->designated_bridge = bpdu->bridge_id;
 251         p->designated_port = bpdu->port_id;
 252         p->designated_age = jiffies - bpdu->message_age;
 253
 254         mod_timer(&p->message_age_timer, jiffies
 255                   + (bpdu->max_age - bpdu->message_age));
 256 }
 257
 258 /* called under bridge lock */
 259 static void br_record_config_timeout_values(struct net_bridge *br,
 260                                             const struct br_config_bpdu *bpdu)
 261 {
 262         br->max_age = bpdu->max_age;
 263         br->hello_time = bpdu->hello_time;
 264         br->forward_delay = bpdu->forward_delay;
 265         __br_set_topology_change(br, bpdu->topology_change);
 266 }
 267
 268 /* called under bridge lock */
 269 void br_transmit_tcn(struct net_bridge *br)
 270 {
 271         struct net_bridge_port *p;
 272
 273         p = br_get_port(br, br->root_port);
 274         if (p)
 275                 br_send_tcn_bpdu(p);
 276         else
 277                 br_notice(br, "root port %u not found for topology notice\n",
 278                           br->root_port);
 279 }
 280
 281 /* called under bridge lock */
 282 static int br_should_become_designated_port(const struct net_bridge_port *p)
 283 {
 284         struct net_bridge *br;
 285         int t;
 286
 287         br = p->br;
 288         if (br_is_designated_port(p))
 289                 return 1;
 290
 291         if (memcmp(&p->designated_root, &br->designated_root, 8))
 292                 return 1;
 293
 294         if (br->root_path_cost < p->designated_cost)
 295                 return 1;
 296         else if (br->root_path_cost > p->designated_cost)
 297                 return 0;
 298
 299         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 300         if (t < 0)
 301                 return 1;
 302         else if (t > 0)
 303                 return 0;
 304
 305         if (p->port_id < p->designated_port)
 306                 return 1;
 307
 308         return 0;
 309 }
 310
 311 /* called under bridge lock */
 312 static void br_designated_port_selection(struct net_bridge *br)
 313 {
 314         struct net_bridge_port *p;
 315
 316         list_for_each_entry(p, &br->port_list, list) {
 317                 if (p->state != BR_STATE_DISABLED &&
 318                     br_should_become_designated_port(p))
 319                         br_become_designated_port(p);
 320
 321         }
 322 }
 323
 324 /* called under bridge lock */
 325 static int br_supersedes_port_info(const struct net_bridge_port *p,
 326                                    const struct br_config_bpdu *bpdu)
 327 {
 328         int t;
 329
 330         t = memcmp(&bpdu->root, &p->designated_root, 8);
 331         if (t < 0)
 332                 return 1;
 333         else if (t > 0)
 334                 return 0;
 335
 336         if (bpdu->root_path_cost < p->designated_cost)
 337                 return 1;
 338         else if (bpdu->root_path_cost > p->designated_cost)
 339                 return 0;
 340
 341         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 342         if (t < 0)
 343                 return 1;
 344         else if (t > 0)
 345                 return 0;
 346
 347         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 348                 return 1;
 349
 350         if (bpdu->port_id <= p->designated_port)
 351                 return 1;
 352
 353         return 0;
 354 }
 355
 356 /* called under bridge lock */
 357 static void br_topology_change_acknowledged(struct net_bridge *br)
 358 {
 359         br->topology_change_detected = 0;
 360         del_timer(&br->tcn_timer);
 361 }
 362
 363 /* called under bridge lock */
 364 void br_topology_change_detection(struct net_bridge *br)
 365 {
 366         int isroot = br_is_root_bridge(br);
 367
 368         if (br->stp_enabled != BR_KERNEL_STP)
 369                 return;
 370
 371         br_info(br, "topology change detected, %s\n",
 372                 isroot ? "propagating" : "sending tcn bpdu");
 373
 374         if (isroot) {
 375                 __br_set_topology_change(br, 1);
 376                 mod_timer(&br->topology_change_timer, jiffies
 377                           + br->bridge_forward_delay + br->bridge_max_age);
 378         } else if (!br->topology_change_detected) {
 379                 br_transmit_tcn(br);
 380                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 381         }
 382
 383         br->topology_change_detected = 1;
 384 }
 385
 386 /* called under bridge lock */
 387 void br_config_bpdu_generation(struct net_bridge *br)
 388 {
 389         struct net_bridge_port *p;
 390
 391         list_for_each_entry(p, &br->port_list, list) {
 392                 if (p->state != BR_STATE_DISABLED &&
 393                     br_is_designated_port(p))
 394                         br_transmit_config(p);
 395         }
 396 }
 397
 398 /* called under bridge lock */
 399 static void br_reply(struct net_bridge_port *p)
 400 {
 401         br_transmit_config(p);
 402 }
 403
 404 /* called under bridge lock */
 405 void br_configuration_update(struct net_bridge *br)
 406 {
 407         br_root_selection(br);
 408         br_designated_port_selection(br);
 409 }
 410
 411 /* called under bridge lock */
 412 void br_become_designated_port(struct net_bridge_port *p)
 413 {
 414         struct net_bridge *br;
 415
 416         br = p->br;
 417         p->designated_root = br->designated_root;
 418         p->designated_cost = br->root_path_cost;
 419         p->designated_bridge = br->bridge_id;
 420         p->designated_port = p->port_id;
 421 }
 422
 423
 424 /* called under bridge lock */
 425 static void br_make_blocking(struct net_bridge_port *p)
 426 {
 427         if (p->state != BR_STATE_DISABLED &&
 428             p->state != BR_STATE_BLOCKING) {
 429                 if (p->state == BR_STATE_FORWARDING ||
 430                     p->state == BR_STATE_LEARNING)
 431                         br_topology_change_detection(p->br);
 432
 433                 br_set_state(p, BR_STATE_BLOCKING);
 434                 br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 435
 436                 del_timer(&p->forward_delay_timer);
 437         }
 438 }
 439
 440 /* called under bridge lock */
 441 static void br_make_forwarding(struct net_bridge_port *p)
 442 {
 443         struct net_bridge *br = p->br;
 444
 445         if (p->state != BR_STATE_BLOCKING)
 446                 return;
 447
 448         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 449                 br_set_state(p, BR_STATE_FORWARDING);
 450                 br_topology_change_detection(br);
 451                 del_timer(&p->forward_delay_timer);
 452         } else if (br->stp_enabled == BR_KERNEL_STP)
 453                 br_set_state(p, BR_STATE_LISTENING);
 454         else
 455                 br_set_state(p, BR_STATE_LEARNING);
 456
 457         br_ifinfo_notify(RTM_NEWLINK, NULL, p);
 458
 459         if (br->forward_delay != 0)
 460                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 461 }
 462
 463 /* called under bridge lock */
 464 void br_port_state_selection(struct net_bridge *br)
 465 {
 466         struct net_bridge_port *p;
 467         unsigned int liveports = 0;
 468
 469         list_for_each_entry(p, &br->port_list, list) {
 470                 if (p->state == BR_STATE_DISABLED)
 471                         continue;
 472
 473                 /* Don't change port states if userspace is handling STP */
 474                 if (br->stp_enabled != BR_USER_STP) {
 475                         if (p->port_no == br->root_port) {
 476                                 p->config_pending = 0;
 477                                 p->topology_change_ack = 0;
 478                                 br_make_forwarding(p);
 479                         } else if (br_is_designated_port(p)) {
 480                                 del_timer(&p->message_age_timer);
 481                                 br_make_forwarding(p);
 482                         } else {
 483                                 p->config_pending = 0;
 484                                 p->topology_change_ack = 0;
 485                                 br_make_blocking(p);
 486                         }
 487                 }
 488
 489                 if (p->state != BR_STATE_BLOCKING)
 490                         br_multicast_enable_port(p);
 491                 /* Multicast is not disabled for the port when it goes in
 492                  * blocking state because the timers will expire and stop by
 493                  * themselves without sending more queries.
 494                  */
 495                 if (p->state == BR_STATE_FORWARDING)
 496                         ++liveports;
 497         }
 498
 499         if (liveports == 0)
 500                 netif_carrier_off(br->dev);
 501         else
 502                 netif_carrier_on(br->dev);
 503 }
 504
 505 /* called under bridge lock */
 506 static void br_topology_change_acknowledge(struct net_bridge_port *p)
 507 {
 508         p->topology_change_ack = 1;
 509         br_transmit_config(p);
 510 }
 511
 512 /* called under bridge lock */
 513 void br_received_config_bpdu(struct net_bridge_port *p,
 514                              const struct br_config_bpdu *bpdu)
 515 {
 516         struct net_bridge *br;
 517         int was_root;
 518
 519         p->stp_xstats.rx_bpdu++;
 520
 521         br = p->br;
 522         was_root = br_is_root_bridge(br);
 523
 524         if (br_supersedes_port_info(p, bpdu)) {
 525                 br_record_config_information(p, bpdu);
 526                 br_configuration_update(br);
 527                 br_port_state_selection(br);
 528
 529                 if (!br_is_root_bridge(br) && was_root) {
 530                         del_timer(&br->hello_timer);
 531                         if (br->topology_change_detected) {
 532                                 del_timer(&br->topology_change_timer);
 533                                 br_transmit_tcn(br);
 534
 535                                 mod_timer(&br->tcn_timer,
 536                                           jiffies + br->bridge_hello_time);
 537                         }
 538                 }
 539
 540                 if (p->port_no == br->root_port) {
 541                         br_record_config_timeout_values(br, bpdu);
 542                         br_config_bpdu_generation(br);
 543                         if (bpdu->topology_change_ack)
 544                                 br_topology_change_acknowledged(br);
 545                 }
 546         } else if (br_is_designated_port(p)) {
 547                 br_reply(p);
 548         }
 549 }
 550
 551 /* called under bridge lock */
 552 void br_received_tcn_bpdu(struct net_bridge_port *p)
 553 {
 554         p->stp_xstats.rx_tcn++;
 555
 556         if (br_is_designated_port(p)) {
 557                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 558                         (unsigned int) p->port_no, p->dev->name);
 559
 560                 br_topology_change_detection(p->br);
 561                 br_topology_change_acknowledge(p);
 562         }
 563 }
 564
 565 /* Change bridge STP parameter */
 566 int br_set_hello_time(struct net_bridge *br, unsigned long val)
 567 {
 568         unsigned long t = clock_t_to_jiffies(val);
 569
 570         if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
 571                 return -ERANGE;
 572
 573         spin_lock_bh(&br->lock);
 574         br->bridge_hello_time = t;
 575         if (br_is_root_bridge(br))
 576                 br->hello_time = br->bridge_hello_time;
 577         spin_unlock_bh(&br->lock);
 578         return 0;
 579 }
 580
 581 int br_set_max_age(struct net_bridge *br, unsigned long val)
 582 {
 583         unsigned long t = clock_t_to_jiffies(val);
 584
 585         if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
 586                 return -ERANGE;
 587
 588         spin_lock_bh(&br->lock);
 589         br->bridge_max_age = t;
 590         if (br_is_root_bridge(br))
 591                 br->max_age = br->bridge_max_age;
 592         spin_unlock_bh(&br->lock);
 593         return 0;
 594
 595 }
 596
 597 /* called under bridge lock */
 598 int __set_ageing_time(struct net_device *dev, unsigned long t)
 599 {
 600         struct switchdev_attr attr = {
 601                 .orig_dev = dev,
 602                 .id = SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME,
 603                 .flags = SWITCHDEV_F_SKIP_EOPNOTSUPP | SWITCHDEV_F_DEFER,
 604                 .u.ageing_time = jiffies_to_clock_t(t),
 605         };
 606         int err;
 607
 608         err = switchdev_port_attr_set(dev, &attr, NULL);
 609         if (err && err != -EOPNOTSUPP)
 610                 return err;
 611
 612         return 0;
 613 }
 614
 615 /* Set time interval that dynamic forwarding entries live
 616  * For pure software bridge, allow values outside the 802.1
 617  * standard specification for special cases:
 618  *  0 - entry never ages (all permanent)
 619  *  1 - entry disappears (no persistence)
 620  *
 621  * Offloaded switch entries maybe more restrictive
 622  */
 623 int br_set_ageing_time(struct net_bridge *br, clock_t ageing_time)
 624 {
 625         unsigned long t = clock_t_to_jiffies(ageing_time);
 626         int err;
 627
 628         err = __set_ageing_time(br->dev, t);
 629         if (err)
 630                 return err;
 631
 632         spin_lock_bh(&br->lock);
 633         br->bridge_ageing_time = t;
 634         br->ageing_time = t;
 635         spin_unlock_bh(&br->lock);
 636
 637         mod_delayed_work(system_long_wq, &br->gc_work, 0);
 638
 639         return 0;
 640 }
 641
 642 clock_t br_get_ageing_time(const struct net_device *br_dev)
 643 {
 644         const struct net_bridge *br;
 645
 646         if (!netif_is_bridge_master(br_dev))
 647                 return 0;
 648
 649         br = netdev_priv(br_dev);
 650
 651         return jiffies_to_clock_t(br->ageing_time);
 652 }
 653 EXPORT_SYMBOL_GPL(br_get_ageing_time);
 654
 655 /* called under bridge lock */
 656 void __br_set_topology_change(struct net_bridge *br, unsigned char val)
 657 {
 658         unsigned long t;
 659         int err;
 660
 661         if (br->stp_enabled == BR_KERNEL_STP && br->topology_change != val) {
 662                 /* On topology change, set the bridge ageing time to twice the
 663                  * forward delay. Otherwise, restore its default ageing time.
 664                  */
 665
 666                 if (val) {
 667                         t = 2 * br->forward_delay;
 668                         br_debug(br, "decreasing ageing time to %lu\n", t);
 669                 } else {
 670                         t = br->bridge_ageing_time;
 671                         br_debug(br, "restoring ageing time to %lu\n", t);
 672                 }
 673
 674                 err = __set_ageing_time(br->dev, t);
 675                 if (err)
 676                         br_warn(br, "error offloading ageing time\n");
 677                 else
 678                         br->ageing_time = t;
 679         }
 680
 681         br->topology_change = val;
 682 }
 683
 684 void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
 685 {
 686         br->bridge_forward_delay = t;
 687         if (br_is_root_bridge(br))
 688                 br->forward_delay = br->bridge_forward_delay;
 689 }
 690
 691 int br_set_forward_delay(struct net_bridge *br, unsigned long val)
 692 {
 693         unsigned long t = clock_t_to_jiffies(val);
 694         int err = -ERANGE;
 695
 696         spin_lock_bh(&br->lock);
 697         if (br->stp_enabled != BR_NO_STP &&
 698             (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
 699                 goto unlock;
 700
 701         __br_set_forward_delay(br, t);
 702         err = 0;
 703
 704 unlock:
 705         spin_unlock_bh(&br->lock);
 706         return err;
 707 }