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