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 } 474