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, jiffies + BR_HOLD_TIME);
 182         }
 183 }
 184
 185 /* called under bridge lock */
 186 static inline void br_record_config_information(struct net_bridge_port *p,
 187                                                 const struct br_config_bpdu *bpdu)
 188 {
 189         p->designated_root = bpdu->root;
 190         p->designated_cost = bpdu->root_path_cost;
 191         p->designated_bridge = bpdu->bridge_id;
 192         p->designated_port = bpdu->port_id;
 193
 194         mod_timer(&p->message_age_timer, jiffies
 195                   + (p->br->max_age - bpdu->message_age));
 196 }
 197
 198 /* called under bridge lock */
 199 static inline void br_record_config_timeout_values(struct net_bridge *br,
 200                                             const struct br_config_bpdu *bpdu)
 201 {
 202         br->max_age = bpdu->max_age;
 203         br->hello_time = bpdu->hello_time;
 204         br->forward_delay = bpdu->forward_delay;
 205         br->topology_change = bpdu->topology_change;
 206 }
 207
 208 /* called under bridge lock */
 209 void br_transmit_tcn(struct net_bridge *br)
 210 {
 211         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 212 }
 213
 214 /* called under bridge lock */
 215 static int br_should_become_designated_port(const struct net_bridge_port *p)
 216 {
 217         struct net_bridge *br;
 218         int t;
 219
 220         br = p->br;
 221         if (br_is_designated_port(p))
 222                 return 1;
 223
 224         if (memcmp(&p->designated_root, &br->designated_root, 8))
 225                 return 1;
 226
 227         if (br->root_path_cost < p->designated_cost)
 228                 return 1;
 229         else if (br->root_path_cost > p->designated_cost)
 230                 return 0;
 231
 232         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 233         if (t < 0)
 234                 return 1;
 235         else if (t > 0)
 236                 return 0;
 237
 238         if (p->port_id < p->designated_port)
 239                 return 1;
 240
 241         return 0;
 242 }
 243
 244 /* called under bridge lock */
 245 static void br_designated_port_selection(struct net_bridge *br)
 246 {
 247         struct net_bridge_port *p;
 248
 249         list_for_each_entry(p, &br->port_list, list) {
 250                 if (p->state != BR_STATE_DISABLED &&
 251                     br_should_become_designated_port(p))
 252                         br_become_designated_port(p);
 253
 254         }
 255 }
 256
 257 /* called under bridge lock */
 258 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 259 {
 260         int t;
 261
 262         t = memcmp(&bpdu->root, &p->designated_root, 8);
 263         if (t < 0)
 264                 return 1;
 265         else if (t > 0)
 266                 return 0;
 267
 268         if (bpdu->root_path_cost < p->designated_cost)
 269                 return 1;
 270         else if (bpdu->root_path_cost > p->designated_cost)
 271                 return 0;
 272
 273         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 274         if (t < 0)
 275                 return 1;
 276         else if (t > 0)
 277                 return 0;
 278
 279         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 280                 return 1;
 281
 282         if (bpdu->port_id <= p->designated_port)
 283                 return 1;
 284
 285         return 0;
 286 }
 287
 288 /* called under bridge lock */
 289 static inline void br_topology_change_acknowledged(struct net_bridge *br)
 290 {
 291         br->topology_change_detected = 0;
 292         del_timer(&br->tcn_timer);
 293 }
 294
 295 /* called under bridge lock */
 296 void br_topology_change_detection(struct net_bridge *br)
 297 {
 298         int isroot = br_is_root_bridge(br);
 299
 300         pr_info("%s: topology change detected, %s\n", br->dev->name,
 301                 isroot ? "propagating" : "sending tcn bpdu");
 302
 303         if (isroot) {
 304                 br->topology_change = 1;
 305                 mod_timer(&br->topology_change_timer, jiffies
 306                           + br->bridge_forward_delay + br->bridge_max_age);
 307         } else if (!br->topology_change_detected) {
 308                 br_transmit_tcn(br);
 309                 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time);
 310         }
 311
 312         br->topology_change_detected = 1;
 313 }
 314
 315 /* called under bridge lock */
 316 void br_config_bpdu_generation(struct net_bridge *br)
 317 {
 318         struct net_bridge_port *p;
 319
 320         list_for_each_entry(p, &br->port_list, list) {
 321                 if (p->state != BR_STATE_DISABLED &&
 322                     br_is_designated_port(p))
 323                         br_transmit_config(p);
 324         }
 325 }
 326
 327 /* called under bridge lock */
 328 static inline void br_reply(struct net_bridge_port *p)
 329 {
 330         br_transmit_config(p);
 331 }
 332
 333 /* called under bridge lock */
 334 void br_configuration_update(struct net_bridge *br)
 335 {
 336         br_root_selection(br);
 337         br_designated_port_selection(br);
 338 }
 339
 340 /* called under bridge lock */
 341 void br_become_designated_port(struct net_bridge_port *p)
 342 {
 343         struct net_bridge *br;
 344
 345         br = p->br;
 346         p->designated_root = br->designated_root;
 347         p->designated_cost = br->root_path_cost;
 348         p->designated_bridge = br->bridge_id;
 349         p->designated_port = p->port_id;
 350 }
 351
 352
 353 /* called under bridge lock */
 354 static void br_make_blocking(struct net_bridge_port *p)
 355 {
 356         if (p->state != BR_STATE_DISABLED &&
 357             p->state != BR_STATE_BLOCKING) {
 358                 if (p->state == BR_STATE_FORWARDING ||
 359                     p->state == BR_STATE_LEARNING)
 360                         br_topology_change_detection(p->br);
 361
 362                 p->state = BR_STATE_BLOCKING;
 363                 br_log_state(p);
 364                 del_timer(&p->forward_delay_timer);
 365         }
 366 }
 367
 368 /* called under bridge lock */
 369 static void br_make_forwarding(struct net_bridge_port *p)
 370 {
 371         if (p->state == BR_STATE_BLOCKING) {
 372                 if (p->br->stp_enabled == BR_KERNEL_STP)
 373                         p->state = BR_STATE_LISTENING;
 374                 else
 375                         p->state = BR_STATE_LEARNING;
 376
 377                 br_log_state(p);
 378                 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay);     }
 379 }
 380
 381 /* called under bridge lock */
 382 void br_port_state_selection(struct net_bridge *br)
 383 {
 384         struct net_bridge_port *p;
 385
 386         /* Don't change port states if userspace is handling STP */
 387         if (br->stp_enabled == BR_USER_STP)
 388                 return;
 389
 390         list_for_each_entry(p, &br->port_list, list) {
 391                 if (p->state != BR_STATE_DISABLED) {
 392                         if (p->port_no == br->root_port) {
 393                                 p->config_pending = 0;
 394                                 p->topology_change_ack = 0;
 395                                 br_make_forwarding(p);
 396                         } else if (br_is_designated_port(p)) {
 397                                 del_timer(&p->message_age_timer);
 398                                 br_make_forwarding(p);
 399                         } else {
 400                                 p->config_pending = 0;
 401                                 p->topology_change_ack = 0;
 402                                 br_make_blocking(p);
 403                         }
 404                 }
 405
 406         }
 407 }
 408
 409 /* called under bridge lock */
 410 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 411 {
 412         p->topology_change_ack = 1;
 413         br_transmit_config(p);
 414 }
 415
 416 /* called under bridge lock */
 417 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 418 {
 419         struct net_bridge *br;
 420         int was_root;
 421
 422         br = p->br;
 423         was_root = br_is_root_bridge(br);
 424
 425         if (br_supersedes_port_info(p, bpdu)) {
 426                 br_record_config_information(p, bpdu);
 427                 br_configuration_update(br);
 428                 br_port_state_selection(br);
 429
 430                 if (!br_is_root_bridge(br) && was_root) {
 431                         del_timer(&br->hello_timer);
 432                         if (br->topology_change_detected) {
 433                                 del_timer(&br->topology_change_timer);
 434                                 br_transmit_tcn(br);
 435
 436                                 mod_timer(&br->tcn_timer,
 437                                           jiffies + br->bridge_hello_time);
 438                         }
 439                 }
 440
 441                 if (p->port_no == br->root_port) {
 442                         br_record_config_timeout_values(br, bpdu);
 443                         br_config_bpdu_generation(br);
 444                         if (bpdu->topology_change_ack)
 445                                 br_topology_change_acknowledged(br);
 446                 }
 447         } else if (br_is_designated_port(p)) {
 448                 br_reply(p);
 449         }
 450 }
 451
 452 /* called under bridge lock */
 453 void br_received_tcn_bpdu(struct net_bridge_port *p)
 454 {
 455         if (br_is_designated_port(p)) {
 456                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
 457                        p->br->dev->name, p->port_no, p->dev->name);
 458
 459                 br_topology_change_detection(p->br);
 460                 br_topology_change_acknowledge(p);
 461         }
 462 }