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 *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         pr_info("%s: port %d(%s) entering %s state\n",
  35                 p->br->dev->name, p->port_no, p->dev->name,
  36                 br_port_state_names[p->state]);
  37
  38 }
  39
  40 /* called under bridge lock */
  41 struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
  42 {
  43         struct net_bridge_port *p;
  44
  45         list_for_each_entry_rcu(p, &br->port_list, list) {
  46                 if (p->port_no == port_no)
  47                         return p;
  48         }
  49
  50         return NULL;
  51 }
  52
  53 /* called under bridge lock */
  54 static int br_should_become_root_port(const struct net_bridge_port *p,
  55                                       u16 root_port)
  56 {
  57         struct net_bridge *br;
  58         struct net_bridge_port *rp;
  59         int t;
  60
  61         br = p->br;
  62         if (p->state == BR_STATE_DISABLED ||
  63             br_is_designated_port(p))
  64                 return 0;
  65
  66         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  67                 return 0;
  68
  69         if (!root_port)
  70                 return 1;
  71
  72         rp = br_get_port(br, root_port);
  73
  74         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  75         if (t < 0)
  76                 return 1;
  77         else if (t > 0)
  78                 return 0;
  79
  80         if (p->designated_cost + p->path_cost <
  81             rp->designated_cost + rp->path_cost)
  82                 return 1;
  83         else if (p->designated_cost + p->path_cost >
  84                  rp->designated_cost + rp->path_cost)
  85                 return 0;
  86
  87         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  88         if (t < 0)
  89                 return 1;
  90         else if (t > 0)
  91                 return 0;
  92
  93         if (p->designated_port < rp->designated_port)
  94                 return 1;
  95         else if (p->designated_port > rp->designated_port)
  96                 return 0;
  97
  98         if (p->port_id < rp->port_id)
  99                 return 1;
 100
 101         return 0;
 102 }
 103
 104 /* called under bridge lock */
 105 static void br_root_selection(struct net_bridge *br)
 106 {
 107         struct net_bridge_port *p;
 108         u16 root_port = 0;
 109
 110         list_for_each_entry(p, &br->port_list, list) {
 111                 if (br_should_become_root_port(p, root_port))
 112                         root_port = p->port_no;
 113
 114         }
 115
 116         br->root_port = root_port;
 117
 118         if (!root_port) {
 119                 br->designated_root = br->bridge_id;
 120                 br->root_path_cost = 0;
 121         } else {
 122                 p = br_get_port(br, root_port);
 123                 br->designated_root = p->designated_root;
 124                 br->root_path_cost = p->designated_cost + p->path_cost;
 125         }
 126 }
 127
 128 /* called under bridge lock */
 129 void br_become_root_bridge(struct net_bridge *br)
 130 {
 131         br->max_age = br->bridge_max_age;
 132         br->hello_time = br->bridge_hello_time;
 133         br->forward_delay = br->bridge_forward_delay;
 134         br_topology_change_detection(br);
 135         del_timer(&br->tcn_timer);
 136
 137         if (br->dev->flags & IFF_UP) {
 138                 br_config_bpdu_generation(br);
 139                 mod_timer(&br->hello_timer, jiffies + br->hello_time);
 140         }
 141 }
 142
 143 /* called under bridge lock */
 144 void br_transmit_config(struct net_bridge_port *p)
 145 {
 146         struct br_config_bpdu bpdu;
 147         struct net_bridge *br;
 148
 149
 150         if (timer_pending(&p->hold_timer)) {
 151                 p->config_pending = 1;
 152                 return;
 153         }
 154
 155         br = p->br;
 156
 157         bpdu.topology_change = br->topology_change;
 158         bpdu.topology_change_ack = p->topology_change_ack;
 159         bpdu.root = br->designated_root;
 160         bpdu.root_path_cost = br->root_path_cost;
 161         bpdu.bridge_id = br->bridge_id;
 162         bpdu.port_id = p->port_id;
 163         if (br_is_root_bridge(br))
 164                 bpdu.message_age = 0;
 165         else {
 166                 struct net_bridge_port *root
 167                         = br_get_port(br, br->root_port);
 168                 bpdu.message_age = br->max_age
 169                         - (root->message_age_timer.expires - jiffies)
 170                         + MESSAGE_AGE_INCR;
 171         }
 172         bpdu.max_age = br->max_age;
 173         bpdu.hello_time = br->hello_time;
 174         bpdu.forward_delay = br->forward_delay;
 175
 176         if (bpdu.message_age < br->max_age) {
 177                 br_send_config_bpdu(p, &bpdu);
 178                 p->topology_change_ack = 0;
 179                 p->config_pending = 0;
 180                 mod_timer(&p->hold_timer,
 181                           round_jiffies(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         struct net_bridge *br = p->br;
 372
 373         if (p->state != BR_STATE_BLOCKING)
 374                 return;
 375
 376         if (br->forward_delay == 0) {
 377                 p->state = BR_STATE_FORWARDING;
 378                 br_topology_change_detection(br);
 379                 del_timer(&p->forward_delay_timer);
 380         }
 381         else if (p->br->stp_enabled == BR_KERNEL_STP)
 382                 p->state = BR_STATE_LISTENING;
 383         else
 384                 p->state = BR_STATE_LEARNING;
 385
 386         br_log_state(p);
 387
 388         if (br->forward_delay != 0)
 389                 mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
 390 }
 391
 392 /* called under bridge lock */
 393 void br_port_state_selection(struct net_bridge *br)
 394 {
 395         struct net_bridge_port *p;
 396
 397         /* Don't change port states if userspace is handling STP */
 398         if (br->stp_enabled == BR_USER_STP)
 399                 return;
 400
 401         list_for_each_entry(p, &br->port_list, list) {
 402                 if (p->state != BR_STATE_DISABLED) {
 403                         if (p->port_no == br->root_port) {
 404                                 p->config_pending = 0;
 405                                 p->topology_change_ack = 0;
 406                                 br_make_forwarding(p);
 407                         } else if (br_is_designated_port(p)) {
 408                                 del_timer(&p->message_age_timer);
 409                                 br_make_forwarding(p);
 410                         } else {
 411                                 p->config_pending = 0;
 412                                 p->topology_change_ack = 0;
 413                                 br_make_blocking(p);
 414                         }
 415                 }
 416
 417         }
 418 }
 419
 420 /* called under bridge lock */
 421 static inline void br_topology_change_acknowledge(struct net_bridge_port *p)
 422 {
 423         p->topology_change_ack = 1;
 424         br_transmit_config(p);
 425 }
 426
 427 /* called under bridge lock */
 428 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 429 {
 430         struct net_bridge *br;
 431         int was_root;
 432
 433         br = p->br;
 434         was_root = br_is_root_bridge(br);
 435
 436         if (br_supersedes_port_info(p, bpdu)) {
 437                 br_record_config_information(p, bpdu);
 438                 br_configuration_update(br);
 439                 br_port_state_selection(br);
 440
 441                 if (!br_is_root_bridge(br) && was_root) {
 442                         del_timer(&br->hello_timer);
 443                         if (br->topology_change_detected) {
 444                                 del_timer(&br->topology_change_timer);
 445                                 br_transmit_tcn(br);
 446
 447                                 mod_timer(&br->tcn_timer,
 448                                           jiffies + br->bridge_hello_time);
 449                         }
 450                 }
 451
 452                 if (p->port_no == br->root_port) {
 453                         br_record_config_timeout_values(br, bpdu);
 454                         br_config_bpdu_generation(br);
 455                         if (bpdu->topology_change_ack)
 456                                 br_topology_change_acknowledged(br);
 457                 }
 458         } else if (br_is_designated_port(p)) {
 459                 br_reply(p);
 460         }
 461 }
 462
 463 /* called under bridge lock */
 464 void br_received_tcn_bpdu(struct net_bridge_port *p)
 465 {
 466         if (br_is_designated_port(p)) {
 467                 pr_info("%s: received tcn bpdu on port %i(%s)\n",
 468                        p->br->dev->name, p->port_no, p->dev->name);
 469
 470                 br_topology_change_detection(p->br);
 471                 br_topology_change_acknowledge(p);
 472         }
 473 }