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  *      $Id: br_stp.c,v 1.4 2000/06/19 10:13:35 davem Exp $
   9  *
  10  *      This program is free software; you can redistribute it and/or
  11  *      modify it under the terms of the GNU General Public License
  12  *      as published by the Free Software Foundation; either version
  13  *      2 of the License, or (at your option) any later version.
  14  */
  15 #include <linux/kernel.h>
  16 #include <linux/smp_lock.h>
  17
  18 #include "br_private.h"
  19 #include "br_private_stp.h"
  20
  21 /* since time values in bpdu are in jiffies and then scaled (1/256)
  22  * before sending, make sure that is at least one.
  23  */
  24 #define MESSAGE_AGE_INCR        ((HZ < 256) ? 1 : (HZ/256))
  25
  26 static const char *br_port_state_names[] = {
  27         [BR_STATE_DISABLED] = "disabled",
  28         [BR_STATE_LISTENING] = "listening",
  29         [BR_STATE_LEARNING] = "learning",
  30         [BR_STATE_FORWARDING] = "forwarding",
  31         [BR_STATE_BLOCKING] = "blocking",
  32 };
  33
  34 void br_log_state(const struct net_bridge_port *p)
  35 {
  36         pr_info("%s: port %d(%s) entering %s state\n",
  37                 p->br->dev->name, p->port_no, p->dev->name,
  38                 br_port_state_names[p->state]);
  39
  40 }
  41
  42 /* called under bridge lock */
  43 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  44 {
  45         struct net_bridge_port *p;
  46
  47         list_for_each_entry_rcu(p, &br->port_list, list) {
  48                 if (p->port_no == port_no)
  49                         return p;
  50         }
  51
  52         return NULL;
  53 }
  54
  55 /* called under bridge lock */
  56 static int br_should_become_root_port(const struct net_bridge_port *p,
  57                                       u16 root_port)
  58 {
  59         struct net_bridge *br;
  60         struct net_bridge_port *rp;
  61         int t;
  62
  63         br = p->br;
  64         if (p->state == BR_STATE_DISABLED ||
  65             br_is_designated_port(p))
  66                 return 0;
  67
  68         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  69                 return 0;
  70
  71         if (!root_port)
  72                 return 1;
  73
  74         rp = br_get_port(br, root_port);
  75
  76         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  77         if (t < 0)
  78                 return 1;
  79         else if (t > 0)
  80                 return 0;
  81
  82         if (p->designated_cost + p->path_cost <
  83             rp->designated_cost + rp->path_cost)
  84                 return 1;
  85         else if (p->designated_cost + p->path_cost >
  86                  rp->designated_cost + rp->path_cost)
  87                 return 0;
  88
  89         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  90         if (t < 0)
  91                 return 1;
  92         else if (t > 0)
  93                 return 0;
  94
  95         if (p->designated_port < rp->designated_port)
  96                 return 1;
  97         else if (p->designated_port > rp->designated_port)
  98                 return 0;
  99
 100         if (p->port_id < rp->port_id)
 101                 return 1;
 102
 103         return 0;
 104 }
 105
 106 /* called under bridge lock */
 107 static void br_root_selection(struct net_bridge *br)
 108 {
 109         struct net_bridge_port *p;
 110         u16 root_port = 0;
 111
 112         list_for_each_entry(p, &br->port_list, list) {
 113                 if (br_should_become_root_port(p, root_port))
 114                         root_port = p->port_no;
 115
 116         }
 117
 118         br->root_port = root_port;
 119
 120         if (!root_port) {
 121                 br->designated_root = br->bridge_id;
 122                 br->root_path_cost = 0;
 123         } else {
 124                 p = br_get_port(br, root_port);
 125                 br->designated_root = p->designated_root;
 126                 br->root_path_cost = p->designated_cost + p->path_cost;
 127         }
 128 }
 129
 130 /* called under bridge lock */
 131 void br_become_root_bridge(struct net_bridge *br)
 132 {
 133         br->max_age = br->bridge_max_age;
 134         br->hello_time = br->bridge_hello_time;
 135         br->forward_delay = br->bridge_forward_delay;
 136         br_topology_change_detection(br);
 137         del_timer(&br->tcn_timer);
 138
 139         if (br->dev->flags & IFF_UP) {
 140                 br_config_bpdu_generation(br);
 141                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 142         }
 143 }
 144
 145 /* called under bridge lock */
 146 void br_transmit_config(struct net_bridge_port *p)
 147 {
 148         struct br_config_bpdu bpdu;
 149         struct net_bridge *br;
 150
 151
 152         if (timer_pending(&p->hold_timer)) {
 153                 p->config_pending = 1;
 154                 return;
 155         }
 156
 157         br = p->br;
 158
 159         bpdu.topology_change = br->topology_change;
 160         bpdu.topology_change_ack = p->topology_change_ack;
 161         bpdu.root = br->designated_root;
 162         bpdu.root_path_cost = br->root_path_cost;
 163         bpdu.bridge_id = br->bridge_id;
 164         bpdu.port_id = p->port_id;
 165         if (br_is_root_bridge(br))
 166                 bpdu.message_age = 0;
 167         else {
 168                 struct net_bridge_port *root
 169                         = br_get_port(br, br->root_port);
 170                 bpdu.message_age = br->max_age
 171                         - (root->message_age_timer.expires - jiffies)
 172                         + MESSAGE_AGE_INCR;
 173         }
 174         bpdu.max_age = br->max_age;
 175         bpdu.hello_time = br->hello_time;
 176         bpdu.forward_delay = br->forward_delay;
 177
 178         if (bpdu.message_age < br->max_age) {
 179                 br_send_config_bpdu(p, &bpdu);
 180                 p->topology_change_ack = 0;
 181                 p->config_pending = 0;
 182                 mod_timer(&p->hold_timer, jiffies + BR_HOLD_TIME);
 183         }
 184 }
 185
 186 /* called under bridge lock */
 187 static inline void br_record_config_information(struct net_bridge_port *p,
 188                                                 const struct br_config_bpdu *bpdu)
 189 {
 190         p->designated_root = bpdu->root;
 191         p->designated_cost = bpdu->root_path_cost;
 192         p->designated_bridge = bpdu->bridge_id;
 193         p->designated_port = bpdu->port_id;
 194
 195         mod_timer(&p->message_age_timer, jiffies
 196                   + (p->br->max_age - bpdu->message_age));
 197 }
 198
 199 /* called under bridge lock */
 200 static inline void br_record_config_timeout_values(struct net_bridge *br,
 201                                             const struct br_config_bpdu *bpdu)
 202 {
 203         br->max_age = bpdu->max_age;
 204         br->hello_time = bpdu->hello_time;
 205         br->forward_delay = bpdu->forward_delay;
 206         br->topology_change = bpdu->topology_change;
 207 }
 208
 209 /* called under bridge lock */
 210 void br_transmit_tcn(struct net_bridge *br)
 211 {
 212         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 213 }
 214
 215 /* called under bridge lock */
 216 static int br_should_become_designated_port(const struct net_bridge_port *p)
 217 {
 218         struct net_bridge *br;
 219         int t;
 220
 221         br = p->br;
 222         if (br_is_designated_port(p))
 223                 return 1;
 224
 225         if (memcmp(&p->designated_root, &br->designated_root, 8))
 226                 return 1;
 227
 228         if (br->root_path_cost < p->designated_cost)
 229                 return 1;
 230         else if (br->root_path_cost > p->designated_cost)
 231                 return 0;
 232
 233         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 234         if (t < 0)
 235                 return 1;
 236         else if (t > 0)
 237                 return 0;
 238
 239         if (p->port_id < p->designated_port)
 240                 return 1;
 241
 242         return 0;
 243 }
 244
 245 /* called under bridge lock */
 246 static void br_designated_port_selection(struct net_bridge *br)
 247 {
 248         struct net_bridge_port *p;
 249
 250         list_for_each_entry(p, &br->port_list, list) {
 251                 if (p->state != BR_STATE_DISABLED &&
 252                     br_should_become_designated_port(p))
 253                         br_become_designated_port(p);
 254
 255         }
 256 }
 257
 258 /* called under bridge lock */
 259 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 260 {
 261         int t;
 262
 263         t = memcmp(&bpdu->root, &p->designated_root, 8);
 264         if (t < 0)
 265                 return 1;
 266         else if (t > 0)
 267                 return 0;
 268
 269         if (bpdu->root_path_cost < p->designated_cost)
 270                 return 1;
 271         else if (bpdu->root_path_cost > p->designated_cost)
 272                 return 0;
 273
 274         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 275         if (t < 0)
 276                 return 1;
 277         else if (t > 0)
 278                 return 0;
 279
 280         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 281                 return 1;
 282
 283         if (bpdu->port_id <= p->designated_port)
 284                 return 1;
 285
 286         return 0;
 287 }
 288
 289 /* called under bridge lock */
 290 static inline void br_topology_change_acknowledged(struct net_bridge *br)
 291 {
 292         br->topology_change_detected = 0;
 293         del_timer(&br->tcn_timer);
 294 }
 295
 296 /* called under bridge lock */
 297 void br_topology_change_detection(struct net_bridge *br)
 298 {
 299         int isroot = br_is_root_bridge(br);
 300
 301         pr_info("%s: topology change detected, %s\n", br->dev->name,
 302                 isroot ? "propagating" : "sending tcn bpdu");
 303
 304         if (isroot) {
 305                 br->topology_change = 1;
 306                 mod_timer(&br->topology_change_timer, jiffies
 307                           + br->bridge_forward_delay + br->bridge_max_age);
 308         } else if (!br->topology_change_detected) {
 309                 br_transmit_tcn(br);
 310                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 311         }
 312
 313         br->topology_change_detected = 1;
 314 }
 315
 316 /* called under bridge lock */
 317 void br_config_bpdu_generation(struct net_bridge *br)
 318 {
 319         struct net_bridge_port *p;
 320
 321         list_for_each_entry(p, &br->port_list, list) {
 322                 if (p->state != BR_STATE_DISABLED &&
 323                     br_is_designated_port(p))
 324                         br_transmit_config(p);
 325         }
 326 }
 327
 328 /* called under bridge lock */
 329 static inline void br_reply(struct net_bridge_port *p)
 330 {
 331         br_transmit_config(p);
 332 }
 333
 334 /* called under bridge lock */
 335 void br_configuration_update(struct net_bridge *br)
 336 {
 337         br_root_selection(br);
 338         br_designated_port_selection(br);
 339 }
 340
 341 /* called under bridge lock */
 342 void br_become_designated_port(struct net_bridge_port *p)
 343 {
 344         struct net_bridge *br;
 345
 346         br = p->br;
 347         p->designated_root = br->designated_root;
 348         p->designated_cost = br->root_path_cost;
 349         p->designated_bridge = br->bridge_id;
 350         p->designated_port = p->port_id;
 351 }
 352
 353
 354 /* called under bridge lock */
 355 static void br_make_blocking(struct net_bridge_port *p)
 356 {
 357         if (p->state != BR_STATE_DISABLED &&
 358             p->state != BR_STATE_BLOCKING) {
 359                 if (p->state == BR_STATE_FORWARDING ||
 360                     p->state == BR_STATE_LEARNING)
 361                         br_topology_change_detection(p->br);
 362
 363                 p->state = BR_STATE_BLOCKING;
 364                 br_log_state(p);
 365                 del_timer(&p->forward_delay_timer);
 366         }
 367 }
 368
 369 /* called under bridge lock */
 370 static void br_make_forwarding(struct net_bridge_port *p)
 371 {
 372         if (p->state == BR_STATE_BLOCKING) {
 373                 if (p->br->stp_enabled) {
 374                         p->state = BR_STATE_LISTENING;
 375                 } else {
 376                         p->state = BR_STATE_LEARNING;
 377                 }
 378                 br_log_state(p);
 379                 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay);     }
 380 }
 381
 382 /* called under bridge lock */
 383 void br_port_state_selection(struct net_bridge *br)
 384 {
 385         struct net_bridge_port *p;
 386
 387         list_for_each_entry(p, &br->port_list, list) {
 388                 if (p->state != BR_STATE_DISABLED) {
 389                         if (p->port_no == br->root_port) {
 390                                 p->config_pending = 0;
 391                                 p->topology_change_ack = 0;
 392                                 br_make_forwarding(p);
 393                         } else if (br_is_designated_port(p)) {
 394                                 del_timer(&p->message_age_timer);
 395                                 br_make_forwarding(p);
 396                         } else {
 397                                 p->config_pending = 0;
 398                                 p->topology_change_ack = 0;
 399                                 br_make_blocking(p);
 400                         }
 401                 }
 402
 403         }
 404 }
 405
 406 /* called under bridge lock */
 407 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 408 {
 409         p->topology_change_ack = 1;
 410         br_transmit_config(p);
 411 }
 412
 413 /* called under bridge lock */
 414 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 415 {
 416         struct net_bridge *br;
 417         int was_root;
 418
 419         br = p->br;
 420         was_root = br_is_root_bridge(br);
 421
 422         if (br_supersedes_port_info(p, bpdu)) {
 423                 br_record_config_information(p, bpdu);
 424                 br_configuration_update(br);
 425                 br_port_state_selection(br);
 426
 427                 if (!br_is_root_bridge(br) && was_root) {
 428                         del_timer(&br->hello_timer);
 429                         if (br->topology_change_detected) {
 430                                 del_timer(&br->topology_change_timer);
 431                                 br_transmit_tcn(br);
 432
 433                                 mod_timer(&br->tcn_timer,
 434                                           jiffies + br->bridge_hello_time);
 435                         }
 436                 }
 437
 438                 if (p->port_no == br->root_port) {
 439                         br_record_config_timeout_values(br, bpdu);
 440                         br_config_bpdu_generation(br);
 441                         if (bpdu->topology_change_ack)
 442                                 br_topology_change_acknowledged(br);
 443                 }
 444         } else if (br_is_designated_port(p)) {
 445                 br_reply(p);
 446         }
 447 }
 448
 449 /* called under bridge lock */
 450 void br_received_tcn_bpdu(struct net_bridge_port *p)
 451 {
 452         if (br_is_designated_port(p)) {
 453                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
 454                        p->br->dev->name, p->port_no, p->dev->name);
 455
 456                 br_topology_change_detection(p->br);
 457                 br_topology_change_acknowledge(p);
 458         }
 459 }