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 } 463