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, 182 round_jiffies(jiffies + BR_HOLD_TIME)); 183 } 184 } 185 186 /* called under bridge lock */ 187 static inline void br_record_config_information(struct net_bridge_port *p, 188 const struct br_config_bpdu *bpdu) 189 { 190 p->designated_root = bpdu->root; 191 p->designated_cost = bpdu->root_path_cost; 192 p->designated_bridge = bpdu->bridge_id; 193 p->designated_port = bpdu->port_id; 194 195 mod_timer(&p->message_age_timer, jiffies 196 + (p->br->max_age - bpdu->message_age)); 197 } 198 199 /* called under bridge lock */ 200 static inline void br_record_config_timeout_values(struct net_bridge *br, 201 const struct br_config_bpdu *bpdu) 202 { 203 br->max_age = bpdu->max_age; 204 br->hello_time = bpdu->hello_time; 205 br->forward_delay = bpdu->forward_delay; 206 br->topology_change = bpdu->topology_change; 207 } 208 209 /* called under bridge lock */ 210 void br_transmit_tcn(struct net_bridge *br) 211 { 212 br_send_tcn_bpdu(br_get_port(br, br->root_port)); 213 } 214 215 /* called under bridge lock */ 216 static int br_should_become_designated_port(const struct net_bridge_port *p) 217 { 218 struct net_bridge *br; 219 int t; 220 221 br = p->br; 222 if (br_is_designated_port(p)) 223 return 1; 224 225 if (memcmp(&p->designated_root, &br->designated_root, 8)) 226 return 1; 227 228 if (br->root_path_cost < p->designated_cost) 229 return 1; 230 else if (br->root_path_cost > p->designated_cost) 231 return 0; 232 233 t = memcmp(&br->bridge_id, &p->designated_bridge, 8); 234 if (t < 0) 235 return 1; 236 else if (t > 0) 237 return 0; 238 239 if (p->port_id < p->designated_port) 240 return 1; 241 242 return 0; 243 } 244 245 /* called under bridge lock */ 246 static void br_designated_port_selection(struct net_bridge *br) 247 { 248 struct net_bridge_port *p; 249 250 list_for_each_entry(p, &br->port_list, list) { 251 if (p->state != BR_STATE_DISABLED && 252 br_should_become_designated_port(p)) 253 br_become_designated_port(p); 254 255 } 256 } 257 258 /* called under bridge lock */ 259 static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu) 260 { 261 int t; 262 263 t = memcmp(&bpdu->root, &p->designated_root, 8); 264 if (t < 0) 265 return 1; 266 else if (t > 0) 267 return 0; 268 269 if (bpdu->root_path_cost < p->designated_cost) 270 return 1; 271 else if (bpdu->root_path_cost > p->designated_cost) 272 return 0; 273 274 t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8); 275 if (t < 0) 276 return 1; 277 else if (t > 0) 278 return 0; 279 280 if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8)) 281 return 1; 282 283 if (bpdu->port_id <= p->designated_port) 284 return 1; 285 286 return 0; 287 } 288 289 /* called under bridge lock */ 290 static inline void br_topology_change_acknowledged(struct net_bridge *br) 291 { 292 br->topology_change_detected = 0; 293 del_timer(&br->tcn_timer); 294 } 295 296 /* called under bridge lock */ 297 void br_topology_change_detection(struct net_bridge *br) 298 { 299 int isroot = br_is_root_bridge(br); 300 301 pr_info("%s: topology change detected, %s\n", br->dev->name, 302 isroot ? "propagating" : "sending tcn bpdu"); 303 304 if (isroot) { 305 br->topology_change = 1; 306 mod_timer(&br->topology_change_timer, jiffies 307 + br->bridge_forward_delay + br->bridge_max_age); 308 } else if (!br->topology_change_detected) { 309 br_transmit_tcn(br); 310 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time); 311 } 312 313 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 list_for_each_entry(p, &br->port_list, list) { 322 if (p->state != BR_STATE_DISABLED && 323 br_is_designated_port(p)) 324 br_transmit_config(p); 325 } 326 } 327 328 /* called under bridge lock */ 329 static inline void br_reply(struct net_bridge_port *p) 330 { 331 br_transmit_config(p); 332 } 333 334 /* called under bridge lock */ 335 void br_configuration_update(struct net_bridge *br) 336 { 337 br_root_selection(br); 338 br_designated_port_selection(br); 339 } 340 341 /* called under bridge lock */ 342 void br_become_designated_port(struct net_bridge_port *p) 343 { 344 struct net_bridge *br; 345 346 br = p->br; 347 p->designated_root = br->designated_root; 348 p->designated_cost = br->root_path_cost; 349 p->designated_bridge = br->bridge_id; 350 p->designated_port = p->port_id; 351 } 352 353 354 /* called under bridge lock */ 355 static void br_make_blocking(struct net_bridge_port *p) 356 { 357 if (p->state != BR_STATE_DISABLED && 358 p->state != BR_STATE_BLOCKING) { 359 if (p->state == BR_STATE_FORWARDING || 360 p->state == BR_STATE_LEARNING) 361 br_topology_change_detection(p->br); 362 363 p->state = BR_STATE_BLOCKING; 364 br_log_state(p); 365 del_timer(&p->forward_delay_timer); 366 } 367 } 368 369 /* called under bridge lock */ 370 static void br_make_forwarding(struct net_bridge_port *p) 371 { 372 if (p->state == BR_STATE_BLOCKING) { 373 if (p->br->stp_enabled == BR_KERNEL_STP) 374 p->state = BR_STATE_LISTENING; 375 else 376 p->state = BR_STATE_LEARNING; 377 378 br_log_state(p); 379 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay); } 380 } 381 382 /* called under bridge lock */ 383 void br_port_state_selection(struct net_bridge *br) 384 { 385 struct net_bridge_port *p; 386 387 /* Don't change port states if userspace is handling STP */ 388 if (br->stp_enabled == BR_USER_STP) 389 return; 390 391 list_for_each_entry(p, &br->port_list, list) { 392 if (p->state != BR_STATE_DISABLED) { 393 if (p->port_no == br->root_port) { 394 p->config_pending = 0; 395 p->topology_change_ack = 0; 396 br_make_forwarding(p); 397 } else if (br_is_designated_port(p)) { 398 del_timer(&p->message_age_timer); 399 br_make_forwarding(p); 400 } else { 401 p->config_pending = 0; 402 p->topology_change_ack = 0; 403 br_make_blocking(p); 404 } 405 } 406 407 } 408 } 409 410 /* called under bridge lock */ 411 static inline void br_topology_change_acknowledge(struct net_bridge_port *p) 412 { 413 p->topology_change_ack = 1; 414 br_transmit_config(p); 415 } 416 417 /* called under bridge lock */ 418 void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu) 419 { 420 struct net_bridge *br; 421 int was_root; 422 423 br = p->br; 424 was_root = br_is_root_bridge(br); 425 426 if (br_supersedes_port_info(p, bpdu)) { 427 br_record_config_information(p, bpdu); 428 br_configuration_update(br); 429 br_port_state_selection(br); 430 431 if (!br_is_root_bridge(br) && was_root) { 432 del_timer(&br->hello_timer); 433 if (br->topology_change_detected) { 434 del_timer(&br->topology_change_timer); 435 br_transmit_tcn(br); 436 437 mod_timer(&br->tcn_timer, 438 jiffies + br->bridge_hello_time); 439 } 440 } 441 442 if (p->port_no == br->root_port) { 443 br_record_config_timeout_values(br, bpdu); 444 br_config_bpdu_generation(br); 445 if (bpdu->topology_change_ack) 446 br_topology_change_acknowledged(br); 447 } 448 } else if (br_is_designated_port(p)) { 449 br_reply(p); 450 } 451 } 452 453 /* called under bridge lock */ 454 void br_received_tcn_bpdu(struct net_bridge_port *p) 455 { 456 if (br_is_designated_port(p)) { 457 pr_info("%s: received tcn bpdu on port %i(%s)\n", 458 p->br->dev->name, p->port_no, p->dev->name); 459 460 br_topology_change_detection(p->br); 461 br_topology_change_acknowledge(p); 462 } 463 } 464