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
  16 #include <linux/kernel.h>
  17 #include <linux/if_bridge.h>
  18 #include <linux/smp_lock.h>
  19 #include <asm/uaccess.h>
  20 #include "br_private.h"
  21 #include "br_private_stp.h"
  22
  23 /* since time values in bpdu are in jiffies and then scaled (1/256)
  24  * before sending, make sure that is at least one.
  25  */
  26 #define MESSAGE_AGE_INCR        ((HZ < 256) ? 1 : (HZ/256))
  27
  28 /* called under ioctl_lock or bridge lock */
  29 int br_is_root_bridge(struct net_bridge *br)
  30 {
  31         return !memcmp(&br->bridge_id, &br->designated_root, 8);
  32 }
  33
  34 /* called under bridge lock */
  35 int br_is_designated_port(struct net_bridge_port *p)
  36 {
  37         return !memcmp(&p->designated_bridge, &p->br->bridge_id, 8) &&
  38                 (p->designated_port == p->port_id);
  39 }
  40
  41 /* called under ioctl_lock or bridge lock */
  42 struct net_bridge_port *br_get_port(struct net_bridge *br, int port_no)
  43 {
  44         struct net_bridge_port *p;
  45
  46         p = br->port_list;
  47         while (p != NULL) {
  48                 if (p->port_no == port_no)
  49                         return p;
  50
  51                 p = p->next;
  52         }
  53
  54         return NULL;
  55 }
  56
  57 /* called under bridge lock */
  58 static int br_should_become_root_port(struct net_bridge_port *p, int root_port)
  59 {
  60         struct net_bridge *br;
  61         struct net_bridge_port *rp;
  62         int t;
  63
  64         br = p->br;
  65         if (p->state == BR_STATE_DISABLED ||
  66             br_is_designated_port(p))
  67                 return 0;
  68
  69         if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0)
  70                 return 0;
  71
  72         if (!root_port)
  73                 return 1;
  74
  75         rp = br_get_port(br, root_port);
  76
  77         t = memcmp(&p->designated_root, &rp->designated_root, 8);
  78         if (t < 0)
  79                 return 1;
  80         else if (t > 0)
  81                 return 0;
  82
  83         if (p->designated_cost + p->path_cost <
  84             rp->designated_cost + rp->path_cost)
  85                 return 1;
  86         else if (p->designated_cost + p->path_cost >
  87                  rp->designated_cost + rp->path_cost)
  88                 return 0;
  89
  90         t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
  91         if (t < 0)
  92                 return 1;
  93         else if (t > 0)
  94                 return 0;
  95
  96         if (p->designated_port < rp->designated_port)
  97                 return 1;
  98         else if (p->designated_port > rp->designated_port)
  99                 return 0;
 100
 101         if (p->port_id < rp->port_id)
 102                 return 1;
 103
 104         return 0;
 105 }
 106
 107 /* called under bridge lock */
 108 static void br_root_selection(struct net_bridge *br)
 109 {
 110         struct net_bridge_port *p;
 111         int root_port;
 112
 113         root_port = 0;
 114
 115         p = br->port_list;
 116         while (p != NULL) {
 117                 if (br_should_become_root_port(p, root_port))
 118                         root_port = p->port_no;
 119
 120                 p = p->next;
 121         }
 122
 123         br->root_port = root_port;
 124
 125         if (!root_port) {
 126                 br->designated_root = br->bridge_id;
 127                 br->root_path_cost = 0;
 128         } else {
 129                 p = br_get_port(br, root_port);
 130                 br->designated_root = p->designated_root;
 131                 br->root_path_cost = p->designated_cost + p->path_cost;
 132         }
 133 }
 134
 135 /* called under bridge lock */
 136 void br_become_root_bridge(struct net_bridge *br)
 137 {
 138         br->max_age = br->bridge_max_age;
 139         br->hello_time = br->bridge_hello_time;
 140         br->forward_delay = br->bridge_forward_delay;
 141         br_topology_change_detection(br);
 142         br_timer_clear(&br->tcn_timer);
 143
 144         br_timer_set(&br->hello_timer, jiffies - br->hello_time);
 145 }
 146
 147 /* called under bridge lock */
 148 void br_transmit_config(struct net_bridge_port *p)
 149 {
 150         struct br_config_bpdu bpdu;
 151         struct net_bridge *br;
 152
 153         if (br_timer_is_running(&p->hold_timer)) {
 154                 p->config_pending = 1;
 155                 return;
 156         }
 157
 158         br = p->br;
 159
 160         bpdu.topology_change = br->topology_change;
 161         bpdu.topology_change_ack = p->topology_change_ack;
 162         bpdu.root = br->designated_root;
 163         bpdu.root_path_cost = br->root_path_cost;
 164         bpdu.bridge_id = br->bridge_id;
 165         bpdu.port_id = p->port_id;
 166         if (br_is_root_bridge(br))
 167                 bpdu.message_age = 0;
 168         else {
 169                 struct net_bridge_port *root;
 170
 171                 root = br_get_port(br, br->root_port);
 172                 bpdu.message_age =  br_timer_get_residue(&root->message_age_timer)
 173                         + MESSAGE_AGE_INCR;
 174         }
 175         bpdu.max_age = br->max_age;
 176         bpdu.hello_time = br->hello_time;
 177         bpdu.forward_delay = br->forward_delay;
 178
 179         if (bpdu.message_age < br->max_age) {
 180                 br_send_config_bpdu(p, &bpdu);
 181
 182                 p->topology_change_ack = 0;
 183                 p->config_pending = 0;
 184                 br_timer_set(&p->hold_timer, jiffies);
 185         }
 186 }
 187
 188 /* called under bridge lock */
 189 static void br_record_config_information(struct net_bridge_port *p, 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         br_timer_set(&p->message_age_timer, jiffies - bpdu->message_age);
 197 }
 198
 199 /* called under bridge lock */
 200 static void br_record_config_timeout_values(struct net_bridge *br, 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(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         p = br->port_list;
 250         while (p != NULL) {
 251                 if (p->state != BR_STATE_DISABLED &&
 252                     br_should_become_designated_port(p))
 253                         br_become_designated_port(p);
 254
 255                 p = p->next;
 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 void br_topology_change_acknowledged(struct net_bridge *br)
 292 {
 293         br->topology_change_detected = 0;
 294         br_timer_clear(&br->tcn_timer);
 295 }
 296
 297 /* called under bridge lock */
 298 void br_topology_change_detection(struct net_bridge *br)
 299 {
 300         printk(KERN_INFO "%s: topology change detected", br->dev.name);
 301
 302         if (br_is_root_bridge(br)) {
 303                 printk(", propagating");
 304                 br->topology_change = 1;
 305                 br_timer_set(&br->topology_change_timer, jiffies);
 306         } else if (!br->topology_change_detected) {
 307                 printk(", sending tcn bpdu");
 308                 br_transmit_tcn(br);
 309                 br_timer_set(&br->tcn_timer, jiffies);
 310         }
 311
 312         printk("\n");
 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         p = br->port_list;
 322         while (p != NULL) {
 323                 if (p->state != BR_STATE_DISABLED &&
 324                     br_is_designated_port(p))
 325                         br_transmit_config(p);
 326
 327                 p = p->next;
 328         }
 329 }
 330
 331 /* called under bridge lock */
 332 static void br_reply(struct net_bridge_port *p)
 333 {
 334         br_transmit_config(p);
 335 }
 336
 337 /* called under bridge lock */
 338 void br_configuration_update(struct net_bridge *br)
 339 {
 340         br_root_selection(br);
 341         br_designated_port_selection(br);
 342 }
 343
 344 /* called under bridge lock */
 345 void br_become_designated_port(struct net_bridge_port *p)
 346 {
 347         struct net_bridge *br;
 348
 349         br = p->br;
 350         p->designated_root = br->designated_root;
 351         p->designated_cost = br->root_path_cost;
 352         p->designated_bridge = br->bridge_id;
 353         p->designated_port = p->port_id;
 354 }
 355
 356 /* called under bridge lock */
 357 static void br_make_blocking(struct net_bridge_port *p)
 358 {
 359         if (p->state != BR_STATE_DISABLED &&
 360             p->state != BR_STATE_BLOCKING) {
 361                 if (p->state == BR_STATE_FORWARDING ||
 362                     p->state == BR_STATE_LEARNING)
 363                         br_topology_change_detection(p->br);
 364
 365                 printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
 366                        p->br->dev.name, p->port_no, p->dev->name, "blocking");
 367
 368                 p->state = BR_STATE_BLOCKING;
 369                 br_timer_clear(&p->forward_delay_timer);
 370         }
 371 }
 372
 373 /* called under bridge lock */
 374 static void br_make_forwarding(struct net_bridge_port *p)
 375 {
 376         if (p->state == BR_STATE_BLOCKING) {
 377                 if (p->br->stp_enabled) {
 378                         printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
 379                                p->br->dev.name, p->port_no, p->dev->name,
 380                                "listening");
 381
 382                         p->state = BR_STATE_LISTENING;
 383                 } else {
 384                         printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
 385                                p->br->dev.name, p->port_no, p->dev->name,
 386                                "learning");
 387
 388                         p->state = BR_STATE_LEARNING;
 389                 }
 390                 br_timer_set(&p->forward_delay_timer, jiffies);
 391         }
 392 }
 393
 394 /* called under bridge lock */
 395 void br_port_state_selection(struct net_bridge *br)
 396 {
 397         struct net_bridge_port *p;
 398
 399         p = br->port_list;
 400         while (p != NULL) {
 401                 if (p->state != BR_STATE_DISABLED) {
 402                         if (p->port_no == br->root_port) {
 403                                 p->config_pending = 0;
 404                                 p->topology_change_ack = 0;
 405                                 br_make_forwarding(p);
 406                         } else if (br_is_designated_port(p)) {
 407                                 br_timer_clear(&p->message_age_timer);
 408                                 br_make_forwarding(p);
 409                         } else {
 410                                 p->config_pending = 0;
 411                                 p->topology_change_ack = 0;
 412                                 br_make_blocking(p);
 413                         }
 414                 }
 415
 416                 p = p->next;
 417         }
 418 }
 419
 420 /* called under bridge lock */
 421 static 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 /* lock-safe */
 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         if (p->state == BR_STATE_DISABLED)
 434                 return;
 435
 436         br = p->br;
 437         read_lock(&br->lock);
 438
 439         was_root = br_is_root_bridge(br);
 440         if (br_supersedes_port_info(p, bpdu)) {
 441                 br_record_config_information(p, bpdu);
 442                 br_configuration_update(br);
 443                 br_port_state_selection(br);
 444
 445                 if (!br_is_root_bridge(br) && was_root) {
 446                         br_timer_clear(&br->hello_timer);
 447                         if (br->topology_change_detected) {
 448                                 br_timer_clear(&br->topology_change_timer);
 449                                 br_transmit_tcn(br);
 450                                 br_timer_set(&br->tcn_timer, jiffies);
 451                         }
 452                 }
 453
 454                 if (p->port_no == br->root_port) {
 455                         br_record_config_timeout_values(br, bpdu);
 456                         br_config_bpdu_generation(br);
 457                         if (bpdu->topology_change_ack)
 458                                 br_topology_change_acknowledged(br);
 459                 }
 460         } else if (br_is_designated_port(p)) {
 461                 br_reply(p);
 462         }
 463
 464         read_unlock(&br->lock);
 465 }
 466
 467 /* lock-safe */
 468 void br_received_tcn_bpdu(struct net_bridge_port *p)
 469 {
 470         read_lock(&p->br->lock);
 471         if (p->state != BR_STATE_DISABLED &&
 472             br_is_designated_port(p)) {
 473                 printk(KERN_INFO "%s: received tcn bpdu on port %i(%s)\n",
 474                        p->br->dev.name, p->port_no, p->dev->name);
 475
 476                 br_topology_change_detection(p->br);
 477                 br_topology_change_acknowledge(p);
 478         }
 479         read_unlock(&p->br->lock);
 480 }