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/rculist.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,
 183                           round_jiffies(jiffies + BR_HOLD_TIME));
 184         }
 185 }
 186
 187 /* called under bridge lock */
 188 static inline void br_record_config_information(struct net_bridge_port *p,
 189                                                 const struct br_config_bpdu *bpdu)
 190 {
 191         p->designated_root = bpdu->root;
 192         p->designated_cost = bpdu->root_path_cost;
 193         p->designated_bridge = bpdu->bridge_id;
 194         p->designated_port = bpdu->port_id;
 195
 196         mod_timer(&p->message_age_timer, jiffies
 197                   + (p->br->max_age - bpdu->message_age));
 198 }
 199
 200 /* called under bridge lock */
 201 static inline void br_record_config_timeout_values(struct net_bridge *br,
 202                                             const struct br_config_bpdu *bpdu)
 203 {
 204         br->max_age = bpdu->max_age;
 205         br->hello_time = bpdu->hello_time;
 206         br->forward_delay = bpdu->forward_delay;
 207         br->topology_change = bpdu->topology_change;
 208 }
 209
 210 /* called under bridge lock */
 211 void br_transmit_tcn(struct net_bridge *br)
 212 {
 213         br_send_tcn_bpdu(br_get_port(br, br->root_port));
 214 }
 215
 216 /* called under bridge lock */
 217 static int br_should_become_designated_port(const struct net_bridge_port *p)
 218 {
 219         struct net_bridge *br;
 220         int t;
 221
 222         br = p->br;
 223         if (br_is_designated_port(p))
 224                 return 1;
 225
 226         if (memcmp(&p->designated_root, &br->designated_root, 8))
 227                 return 1;
 228
 229         if (br->root_path_cost < p->designated_cost)
 230                 return 1;
 231         else if (br->root_path_cost > p->designated_cost)
 232                 return 0;
 233
 234         t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
 235         if (t < 0)
 236                 return 1;
 237         else if (t > 0)
 238                 return 0;
 239
 240         if (p->port_id < p->designated_port)
 241                 return 1;
 242
 243         return 0;
 244 }
 245
 246 /* called under bridge lock */
 247 static void br_designated_port_selection(struct net_bridge *br)
 248 {
 249         struct net_bridge_port *p;
 250
 251         list_for_each_entry(p, &br->port_list, list) {
 252                 if (p->state != BR_STATE_DISABLED &&
 253                     br_should_become_designated_port(p))
 254                         br_become_designated_port(p);
 255
 256         }
 257 }
 258
 259 /* called under bridge lock */
 260 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 261 {
 262         int t;
 263
 264         t = memcmp(&bpdu->root, &p->designated_root, 8);
 265         if (t < 0)
 266                 return 1;
 267         else if (t > 0)
 268                 return 0;
 269
 270         if (bpdu->root_path_cost < p->designated_cost)
 271                 return 1;
 272         else if (bpdu->root_path_cost > p->designated_cost)
 273                 return 0;
 274
 275         t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
 276         if (t < 0)
 277                 return 1;
 278         else if (t > 0)
 279                 return 0;
 280
 281         if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8))
 282                 return 1;
 283
 284         if (bpdu->port_id <= p->designated_port)
 285                 return 1;
 286
 287         return 0;
 288 }
 289
 290 /* called under bridge lock */
 291 static inline void br_topology_change_acknowledged(struct net_bridge *br)
 292 {
 293         br->topology_change_detected = 0;
 294         del_timer(&br->tcn_timer);
 295 }
 296
 297 /* called under bridge lock */
 298 void br_topology_change_detection(struct net_bridge *br)
 299 {
 300         int isroot = br_is_root_bridge(br);
 301
 302         pr_info("%s: topology change detected, %s\n", br->dev->name,
 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         if (p->state == BR_STATE_BLOCKING) {
 374                 if (p->br->stp_enabled == BR_KERNEL_STP)
 375                         p->state = BR_STATE_LISTENING;
 376                 else
 377                         p->state = BR_STATE_LEARNING;
 378
 379                 br_log_state(p);
 380                 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay);     }
 381 }
 382
 383 /* called under bridge lock */
 384 void br_port_state_selection(struct net_bridge *br)
 385 {
 386         struct net_bridge_port *p;
 387
 388         /* Don't change port states if userspace is handling STP */
 389         if (br->stp_enabled == BR_USER_STP)
 390                 return;
 391
 392         list_for_each_entry(p, &br->port_list, list) {
 393                 if (p->state != BR_STATE_DISABLED) {
 394                         if (p->port_no == br->root_port) {
 395                                 p->config_pending = 0;
 396                                 p->topology_change_ack = 0;
 397                                 br_make_forwarding(p);
 398                         } else if (br_is_designated_port(p)) {
 399                                 del_timer(&p->message_age_timer);
 400                                 br_make_forwarding(p);
 401                         } else {
 402                                 p->config_pending = 0;
 403                                 p->topology_change_ack = 0;
 404                                 br_make_blocking(p);
 405                         }
 406                 }
 407
 408         }
 409 }
 410
 411 /* called under bridge lock */
 412 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 413 {
 414         p->topology_change_ack = 1;
 415         br_transmit_config(p);
 416 }
 417
 418 /* called under bridge lock */
 419 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 420 {
 421         struct net_bridge *br;
 422         int was_root;
 423
 424         br = p->br;
 425         was_root = br_is_root_bridge(br);
 426
 427         if (br_supersedes_port_info(p, bpdu)) {
 428                 br_record_config_information(p, bpdu);
 429                 br_configuration_update(br);
 430                 br_port_state_selection(br);
 431
 432                 if (!br_is_root_bridge(br) && was_root) {
 433                         del_timer(&br->hello_timer);
 434                         if (br->topology_change_detected) {
 435                                 del_timer(&br->topology_change_timer);
 436                                 br_transmit_tcn(br);
 437
 438                                 mod_timer(&br->tcn_timer,
 439                                           jiffies + br->bridge_hello_time);
 440                         }
 441                 }
 442
 443                 if (p->port_no == br->root_port) {
 444                         br_record_config_timeout_values(br, bpdu);
 445                         br_config_bpdu_generation(br);
 446                         if (bpdu->topology_change_ack)
 447                                 br_topology_change_acknowledged(br);
 448                 }
 449         } else if (br_is_designated_port(p)) {
 450                 br_reply(p);
 451         }
 452 }
 453
 454 /* called under bridge lock */
 455 void br_received_tcn_bpdu(struct net_bridge_port *p)
 456 {
 457         if (br_is_designated_port(p)) {
 458                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
 459                        p->br->dev->name, p->port_no, p->dev->name);
 460
 461                 br_topology_change_detection(p->br);
 462                 br_topology_change_acknowledge(p);
 463         }
 464 }