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
  17 #include "br_private.h"
  18 #include "br_private_stp.h"
  19
  20 /* since time values in bpdu are in jiffies and then scaled (1/256)
  21  * before sending, make sure that is at least one.
  22  */
  23 #define MESSAGE_AGE_INCR        ((HZ < 256) ? 1 : (HZ/256))
  24
  25 static const char *br_port_state_names[] = {
  26         [BR_STATE_DISABLED] = "disabled",
  27         [BR_STATE_LISTENING] = "listening",
  28         [BR_STATE_LEARNING] = "learning",
  29         [BR_STATE_FORWARDING] = "forwarding",
  30         [BR_STATE_BLOCKING] = "blocking",
  31 };
  32
  33 void br_log_state(const struct net_bridge_port *p)
  34 {
  35         pr_info("%s: port %d(%s) entering %s state\n",
  36                 p->br->dev->name, p->port_no, p->dev->name,
  37                 br_port_state_names[p->state]);
  38
  39 }
  40
  41 /* called under bridge lock */
  42 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  43 {
  44         struct net_bridge_port *p;
  45
  46         list_for_each_entry_rcu(p, &br->port_list, list) {
  47                 if (p->port_no == port_no)
  48                         return p;
  49         }
  50
  51         return NULL;
  52 }
  53
  54 /* called under bridge lock */
  55 static int br_should_become_root_port(const struct net_bridge_port *p,
  56                                       u16 root_port)
  57 {
  58         struct net_bridge *br;
  59         struct net_bridge_port *rp;
  60         int t;
  61
  62         br = p->br;
  63         if (p->state == BR_STATE_DISABLED ||
  64             br_is_designated_port(p))
  65                 return 0;
  66
  67         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  68                 return 0;
  69
  70         if (!root_port)
  71                 return 1;
  72
  73         rp = br_get_port(br, root_port);
  74
  75         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  76         if (t < 0)
  77                 return 1;
  78         else if (t > 0)
  79                 return 0;
  80
  81         if (p->designated_cost + p->path_cost <
  82             rp->designated_cost + rp->path_cost)
  83                 return 1;
  84         else if (p->designated_cost + p->path_cost >
  85                  rp->designated_cost + rp->path_cost)
  86                 return 0;
  87
  88         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  89         if (t < 0)
  90                 return 1;
  91         else if (t > 0)
  92                 return 0;
  93
  94         if (p->designated_port < rp->designated_port)
  95                 return 1;
  96         else if (p->designated_port > rp->designated_port)
  97                 return 0;
  98
  99         if (p->port_id < rp->port_id)
 100                 return 1;
 101
 102         return 0;
 103 }
 104
 105 /* called under bridge lock */
 106 static void br_root_selection(struct net_bridge *br)
 107 {
 108         struct net_bridge_port *p;
 109         u16 root_port = 0;
 110
 111         list_for_each_entry(p, &br->port_list, list) {
 112                 if (br_should_become_root_port(p, root_port))
 113                         root_port = p->port_no;
 114
 115         }
 116
 117         br->root_port = root_port;
 118
 119         if (!root_port) {
 120                 br->designated_root = br->bridge_id;
 121                 br->root_path_cost = 0;
 122         } else {
 123                 p = br_get_port(br, root_port);
 124                 br->designated_root = p->designated_root;
 125                 br->root_path_cost = p->designated_cost + p->path_cost;
 126         }
 127 }
 128
 129 /* called under bridge lock */
 130 void br_become_root_bridge(struct net_bridge *br)
 131 {
 132         br->max_age = br->bridge_max_age;
 133         br->hello_time = br->bridge_hello_time;
 134         br->forward_delay = br->bridge_forward_delay;
 135         br_topology_change_detection(br);
 136         del_timer(&br->tcn_timer);
 137
 138         if (br->dev->flags & IFF_UP) {
 139                 br_config_bpdu_generation(br);
 140                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 141         }
 142 }
 143
 144 /* called under bridge lock */
 145 void br_transmit_config(struct net_bridge_port *p)
 146 {
 147         struct br_config_bpdu bpdu;
 148         struct net_bridge *br;
 149
 150
 151         if (timer_pending(&p->hold_timer)) {
 152                 p->config_pending = 1;
 153                 return;
 154         }
 155
 156         br = p->br;
 157
 158         bpdu.topology_change = br->topology_change;
 159         bpdu.topology_change_ack = p->topology_change_ack;
 160         bpdu.root = br->designated_root;
 161         bpdu.root_path_cost = br->root_path_cost;
 162         bpdu.bridge_id = br->bridge_id;
 163         bpdu.port_id = p->port_id;
 164         if (br_is_root_bridge(br))
 165                 bpdu.message_age = 0;
 166         else {
 167                 struct net_bridge_port *root
 168                         = br_get_port(br, br->root_port);
 169                 bpdu.message_age = br->max_age
 170                         - (root->message_age_timer.expires - jiffies)
 171                         + MESSAGE_AGE_INCR;
 172         }
 173         bpdu.max_age = br->max_age;
 174         bpdu.hello_time = br->hello_time;
 175         bpdu.forward_delay = br->forward_delay;
 176
 177         if (bpdu.message_age < br->max_age) {
 178                 br_send_config_bpdu(p, &bpdu);
 179                 p->topology_change_ack = 0;
 180                 p->config_pending = 0;
 181                 mod_timer(&p->hold_timer,
 182                           round_jiffies(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 == BR_KERNEL_STP)
 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         /* Don't change port states if userspace is handling STP */
 388         if (br->stp_enabled == BR_USER_STP)
 389                 return;
 390
 391         list_for_each_entry(p, &br->port_list, list) {
 392                 if (p->state != BR_STATE_DISABLED) {
 393                         if (p->port_no == br->root_port) {
 394                                 p->config_pending = 0;
 395                                 p->topology_change_ack = 0;
 396                                 br_make_forwarding(p);
 397                         } else if (br_is_designated_port(p)) {
 398                                 del_timer(&p->message_age_timer);
 399                                 br_make_forwarding(p);
 400                         } else {
 401                                 p->config_pending = 0;
 402                                 p->topology_change_ack = 0;
 403                                 br_make_blocking(p);
 404                         }
 405                 }
 406
 407         }
 408 }
 409
 410 /* called under bridge lock */
 411 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 412 {
 413         p->topology_change_ack = 1;
 414         br_transmit_config(p);
 415 }
 416
 417 /* called under bridge lock */
 418 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 419 {
 420         struct net_bridge *br;
 421         int was_root;
 422
 423         br = p->br;
 424         was_root = br_is_root_bridge(br);
 425
 426         if (br_supersedes_port_info(p, bpdu)) {
 427                 br_record_config_information(p, bpdu);
 428                 br_configuration_update(br);
 429                 br_port_state_selection(br);
 430
 431                 if (!br_is_root_bridge(br) && was_root) {
 432                         del_timer(&br->hello_timer);
 433                         if (br->topology_change_detected) {
 434                                 del_timer(&br->topology_change_timer);
 435                                 br_transmit_tcn(br);
 436
 437                                 mod_timer(&br->tcn_timer,
 438                                           jiffies + br->bridge_hello_time);
 439                         }
 440                 }
 441
 442                 if (p->port_no == br->root_port) {
 443                         br_record_config_timeout_values(br, bpdu);
 444                         br_config_bpdu_generation(br);
 445                         if (bpdu->topology_change_ack)
 446                                 br_topology_change_acknowledged(br);
 447                 }
 448         } else if (br_is_designated_port(p)) {
 449                 br_reply(p);
 450         }
 451 }
 452
 453 /* called under bridge lock */
 454 void br_received_tcn_bpdu(struct net_bridge_port *p)
 455 {
 456         if (br_is_designated_port(p)) {
 457                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
 458                        p->br->dev->name, p->port_no, p->dev->name);
 459
 460                 br_topology_change_detection(p->br);
 461                 br_topology_change_acknowledge(p);
 462         }
 463 }