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.
  21  */
  22 #define MESSAGE_AGE_INCR        ((HZ < 256) ? 1 : (HZ/256))
  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) entering %s state\n",
  35                 (unsigned) p->port_no, p->dev->name,
  36                 br_port_state_names[p->state]);
  37 }
  38
  39 /* called under bridge lock */
  40 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  41 {
  42         struct net_bridge_port *p;
  43
  44         list_for_each_entry_rcu(p, &br->port_list, list) {
  45                 if (p->port_no == port_no)
  46                         return p;
  47         }
  48
  49         return NULL;
  50 }
  51
  52 /* called under bridge lock */
  53 static int br_should_become_root_port(const struct net_bridge_port *p,
  54                                       u16 root_port)
  55 {
  56         struct net_bridge *br;
  57         struct net_bridge_port *rp;
  58         int t;
  59
  60         br = p->br;
  61         if (p->state == BR_STATE_DISABLED ||
  62             br_is_designated_port(p))
  63                 return 0;
  64
  65         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  66                 return 0;
  67
  68         if (!root_port)
  69                 return 1;
  70
  71         rp = br_get_port(br, root_port);
  72
  73         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  74         if (t < 0)
  75                 return 1;
  76         else if (t > 0)
  77                 return 0;
  78
  79         if (p->designated_cost + p->path_cost <
  80             rp->designated_cost + rp->path_cost)
  81                 return 1;
  82         else if (p->designated_cost + p->path_cost >
  83                  rp->designated_cost + rp->path_cost)
  84                 return 0;
  85
  86         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  87         if (t < 0)
  88                 return 1;
  89         else if (t > 0)
  90                 return 0;
  91
  92         if (p->designated_port < rp->designated_port)
  93                 return 1;
  94         else if (p->designated_port > rp->designated_port)
  95                 return 0;
  96
  97         if (p->port_id < rp->port_id)
  98                 return 1;
  99
 100         return 0;
 101 }
 102
 103 /* called under bridge lock */
 104 static void br_root_selection(struct net_bridge *br)
 105 {
 106         struct net_bridge_port *p;
 107         u16 root_port = 0;
 108
 109         list_for_each_entry(p, &br->port_list, list) {
 110                 if (br_should_become_root_port(p, root_port))
 111                         root_port = p->port_no;
 112
 113         }
 114
 115         br->root_port = root_port;
 116
 117         if (!root_port) {
 118                 br->designated_root = br->bridge_id;
 119                 br->root_path_cost = 0;
 120         } else {
 121                 p = br_get_port(br, root_port);
 122                 br->designated_root = p->designated_root;
 123                 br->root_path_cost = p->designated_cost + p->path_cost;
 124         }
 125 }
 126
 127 /* called under bridge lock */
 128 void br_become_root_bridge(struct net_bridge *br)
 129 {
 130         br->max_age = br->bridge_max_age;
 131         br->hello_time = br->bridge_hello_time;
 132         br->forward_delay = br->bridge_forward_delay;
 133         br_topology_change_detection(br);
 134         del_timer(&br->tcn_timer);
 135
 136         if (br->dev->flags & IFF_UP) {
 137                 br_config_bpdu_generation(br);
 138                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 139         }
 140 }
 141
 142 /* called under bridge lock */
 143 void br_transmit_config(struct net_bridge_port *p)
 144 {
 145         struct br_config_bpdu bpdu;
 146         struct net_bridge *br;
 147
 148
 149         if (timer_pending(&p->hold_timer)) {
 150                 p->config_pending = 1;
 151                 return;
 152         }
 153
 154         br = p->br;
 155
 156         bpdu.topology_change = br->topology_change;
 157         bpdu.topology_change_ack = p->topology_change_ack;
 158         bpdu.root = br->designated_root;
 159         bpdu.root_path_cost = br->root_path_cost;
 160         bpdu.bridge_id = br->bridge_id;
 161         bpdu.port_id = p->port_id;
 162         if (br_is_root_bridge(br))
 163                 bpdu.message_age = 0;
 164         else {
 165                 struct net_bridge_port *root
 166                         = br_get_port(br, br->root_port);
 167                 bpdu.message_age = br->max_age
 168                         - (root->message_age_timer.expires - jiffies)
 169                         + MESSAGE_AGE_INCR;
 170         }
 171         bpdu.max_age = br->max_age;
 172         bpdu.hello_time = br->hello_time;
 173         bpdu.forward_delay = br->forward_delay;
 174
 175         if (bpdu.message_age < br->max_age) {
 176                 br_send_config_bpdu(p, &bpdu);
 177                 p->topology_change_ack = 0;
 178                 p->config_pending = 0;
 179                 mod_timer(&p->hold_timer,
 180                           round_jiffies(jiffies + BR_HOLD_TIME));
 181         }
 182 }
 183
 184 /* called under bridge lock */
 185 static inline void br_record_config_information(struct net_bridge_port *p,
 186                                                 const struct br_config_bpdu *bpdu)
 187 {
 188         p->designated_root = bpdu->root;
 189         p->designated_cost = bpdu->root_path_cost;
 190         p->designated_bridge = bpdu->bridge_id;
 191         p->designated_port = bpdu->port_id;
 192
 193         mod_timer(&p->message_age_timer, jiffies
 194                   + (p->br->max_age - bpdu->message_age));
 195 }
 196
 197 /* called under bridge lock */
 198 static inline void br_record_config_timeout_values(struct net_bridge *br,
 199                                             const struct br_config_bpdu *bpdu)
 200 {
 201         br->max_age = bpdu->max_age;
 202         br->hello_time = bpdu->hello_time;
 203         br->forward_delay = bpdu->forward_delay;
 204         br->topology_change = bpdu->topology_change;
 205 }
 206
 207 /* called under bridge lock */
 208 void br_transmit_tcn(struct net_bridge *br)
 209 {
 210         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 211 }
 212
 213 /* called under bridge lock */
 214 static int br_should_become_designated_port(const struct net_bridge_port *p)
 215 {
 216         struct net_bridge *br;
 217         int t;
 218
 219         br = p->br;
 220         if (br_is_designated_port(p))
 221                 return 1;
 222
 223         if (memcmp(&p->designated_root, &br->designated_root, 8))
 224                 return 1;
 225
 226         if (br->root_path_cost < p->designated_cost)
 227                 return 1;
 228         else if (br->root_path_cost > p->designated_cost)
 229                 return 0;
 230
 231         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 232         if (t < 0)
 233                 return 1;
 234         else if (t > 0)
 235                 return 0;
 236
 237         if (p->port_id < p->designated_port)
 238                 return 1;
 239
 240         return 0;
 241 }
 242
 243 /* called under bridge lock */
 244 static void br_designated_port_selection(struct net_bridge *br)
 245 {
 246         struct net_bridge_port *p;
 247
 248         list_for_each_entry(p, &br->port_list, list) {
 249                 if (p->state != BR_STATE_DISABLED &&
 250                     br_should_become_designated_port(p))
 251                         br_become_designated_port(p);
 252
 253         }
 254 }
 255
 256 /* called under bridge lock */
 257 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 258 {
 259         int t;
 260
 261         t = memcmp(&bpdu->root, &p->designated_root, 8);
 262         if (t < 0)
 263                 return 1;
 264         else if (t > 0)
 265                 return 0;
 266
 267         if (bpdu->root_path_cost < p->designated_cost)
 268                 return 1;
 269         else if (bpdu->root_path_cost > p->designated_cost)
 270                 return 0;
 271
 272         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 273         if (t < 0)
 274                 return 1;
 275         else if (t > 0)
 276                 return 0;
 277
 278         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 279                 return 1;
 280
 281         if (bpdu->port_id <= p->designated_port)
 282                 return 1;
 283
 284         return 0;
 285 }
 286
 287 /* called under bridge lock */
 288 static inline void br_topology_change_acknowledged(struct net_bridge *br)
 289 {
 290         br->topology_change_detected = 0;
 291         del_timer(&br->tcn_timer);
 292 }
 293
 294 /* called under bridge lock */
 295 void br_topology_change_detection(struct net_bridge *br)
 296 {
 297         int isroot = br_is_root_bridge(br);
 298
 299         if (br->stp_enabled != BR_KERNEL_STP)
 300                 return;
 301
 302         br_info(br, "topology change detected, %s\n",
 303                 isroot ? "propagating" : "sending tcn bpdu");
 304
 305         if (isroot) {
 306                 br->topology_change = 1;
 307                 mod_timer(&br->topology_change_timer, jiffies
 308                           + br->bridge_forward_delay + br->bridge_max_age);
 309         } else if (!br->topology_change_detected) {
 310                 br_transmit_tcn(br);
 311                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 312         }
 313
 314         br->topology_change_detected = 1;
 315 }
 316
 317 /* called under bridge lock */
 318 void br_config_bpdu_generation(struct net_bridge *br)
 319 {
 320         struct net_bridge_port *p;
 321
 322         list_for_each_entry(p, &br->port_list, list) {
 323                 if (p->state != BR_STATE_DISABLED &&
 324                     br_is_designated_port(p))
 325                         br_transmit_config(p);
 326         }
 327 }
 328
 329 /* called under bridge lock */
 330 static inline void br_reply(struct net_bridge_port *p)
 331 {
 332         br_transmit_config(p);
 333 }
 334
 335 /* called under bridge lock */
 336 void br_configuration_update(struct net_bridge *br)
 337 {
 338         br_root_selection(br);
 339         br_designated_port_selection(br);
 340 }
 341
 342 /* called under bridge lock */
 343 void br_become_designated_port(struct net_bridge_port *p)
 344 {
 345         struct net_bridge *br;
 346
 347         br = p->br;
 348         p->designated_root = br->designated_root;
 349         p->designated_cost = br->root_path_cost;
 350         p->designated_bridge = br->bridge_id;
 351         p->designated_port = p->port_id;
 352 }
 353
 354
 355 /* called under bridge lock */
 356 static void br_make_blocking(struct net_bridge_port *p)
 357 {
 358         if (p->state != BR_STATE_DISABLED &&
 359             p->state != BR_STATE_BLOCKING) {
 360                 if (p->state == BR_STATE_FORWARDING ||
 361                     p->state == BR_STATE_LEARNING)
 362                         br_topology_change_detection(p->br);
 363
 364                 p->state = BR_STATE_BLOCKING;
 365                 br_log_state(p);
 366                 del_timer(&p->forward_delay_timer);
 367         }
 368 }
 369
 370 /* called under bridge lock */
 371 static void br_make_forwarding(struct net_bridge_port *p)
 372 {
 373         struct net_bridge *br = p->br;
 374
 375         if (p->state != BR_STATE_BLOCKING)
 376                 return;
 377
 378         if (br->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
 379                 p->state = BR_STATE_FORWARDING;
 380                 br_topology_change_detection(br);
 381                 del_timer(&p->forward_delay_timer);
 382         }
 383         else if (br->stp_enabled == BR_KERNEL_STP)
 384                 p->state = BR_STATE_LISTENING;
 385         else
 386                 p->state = BR_STATE_LEARNING;
 387
 388         br_multicast_enable_port(p);
 389
 390         br_log_state(p);
 391
 392         if (br->forward_delay != 0)
 393                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 394 }
 395
 396 /* called under bridge lock */
 397 void br_port_state_selection(struct net_bridge *br)
 398 {
 399         struct net_bridge_port *p;
 400
 401         /* Don't change port states if userspace is handling STP */
 402         if (br->stp_enabled == BR_USER_STP)
 403                 return;
 404
 405         list_for_each_entry(p, &br->port_list, list) {
 406                 if (p->state != BR_STATE_DISABLED) {
 407                         if (p->port_no == br->root_port) {
 408                                 p->config_pending = 0;
 409                                 p->topology_change_ack = 0;
 410                                 br_make_forwarding(p);
 411                         } else if (br_is_designated_port(p)) {
 412                                 del_timer(&p->message_age_timer);
 413                                 br_make_forwarding(p);
 414                         } else {
 415                                 p->config_pending = 0;
 416                                 p->topology_change_ack = 0;
 417                                 br_make_blocking(p);
 418                         }
 419                 }
 420
 421         }
 422 }
 423
 424 /* called under bridge lock */
 425 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 426 {
 427         p->topology_change_ack = 1;
 428         br_transmit_config(p);
 429 }
 430
 431 /* called under bridge lock */
 432 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 433 {
 434         struct net_bridge *br;
 435         int was_root;
 436
 437         br = p->br;
 438         was_root = br_is_root_bridge(br);
 439
 440         if (br_supersedes_port_info(p, bpdu)) {
 441                 br_record_config_information(p, bpdu);
 442                 br_configuration_update(br);
 443                 br_port_state_selection(br);
 444
 445                 if (!br_is_root_bridge(br) && was_root) {
 446                         del_timer(&br->hello_timer);
 447                         if (br->topology_change_detected) {
 448                                 del_timer(&br->topology_change_timer);
 449                                 br_transmit_tcn(br);
 450
 451                                 mod_timer(&br->tcn_timer,
 452                                           jiffies + br->bridge_hello_time);
 453                         }
 454                 }
 455
 456                 if (p->port_no == br->root_port) {
 457                         br_record_config_timeout_values(br, bpdu);
 458                         br_config_bpdu_generation(br);
 459                         if (bpdu->topology_change_ack)
 460                                 br_topology_change_acknowledged(br);
 461                 }
 462         } else if (br_is_designated_port(p)) {
 463                 br_reply(p);
 464         }
 465 }
 466
 467 /* called under bridge lock */
 468 void br_received_tcn_bpdu(struct net_bridge_port *p)
 469 {
 470         if (br_is_designated_port(p)) {
 471                 br_info(p->br, "port %u(%s) received tcn bpdu\n",
 472                         (unsigned) p->port_no, p->dev->name);
 473
 474                 br_topology_change_detection(p->br);
 475                 br_topology_change_acknowledge(p);
 476         }
 477 }