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 1.1.1.1 2007-08-03 18:53:50 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 25static 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 33void 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 */ 42struct 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 */ 55static 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 */ 106static 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 */ 130void 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 */ 145void 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 */ 187static 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 */ 200static 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 */ 210void 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 */ 216static 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 */ 246static 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 */ 259static 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 */ 290static 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 */ 297void 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 u32 ratio = HZ/10; 306 br->topology_change = 1; 307 mod_timer(&br->topology_change_timer, jiffies 308 + (br->bridge_forward_delay + br->bridge_max_age)/ratio); 309 } else if (!br->topology_change_detected) { 310 br_transmit_tcn(br); 311 mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time); 312 } 313 314 br->topology_change_detected = 1; 315} 316 317/* called under bridge lock */ 318void br_config_bpdu_generation(struct net_bridge *br) 319{ 320 struct net_bridge_port *p; 321 322 list_for_each_entry(p, &br->port_list, list) { 323 if (p->state != BR_STATE_DISABLED && 324 br_is_designated_port(p)) 325 br_transmit_config(p); 326 } 327} 328 329/* called under bridge lock */ 330static inline void br_reply(struct net_bridge_port *p) 331{ 332 br_transmit_config(p); 333} 334 335/* called under bridge lock */ 336void br_configuration_update(struct net_bridge *br) 337{ 338 br_root_selection(br); 339 br_designated_port_selection(br); 340} 341 342/* called under bridge lock */ 343void br_become_designated_port(struct net_bridge_port *p) 344{ 345 struct net_bridge *br; 346 347 br = p->br; 348 p->designated_root = br->designated_root; 349 p->designated_cost = br->root_path_cost; 350 p->designated_bridge = br->bridge_id; 351 p->designated_port = p->port_id; 352} 353 354 355/* called under bridge lock */ 356static void br_make_blocking(struct net_bridge_port *p) 357{ 358 if (p->state != BR_STATE_DISABLED && 359 p->state != BR_STATE_BLOCKING) { 360 if (p->state == BR_STATE_FORWARDING || 361 p->state == BR_STATE_LEARNING) 362 br_topology_change_detection(p->br); 363 364 p->state = BR_STATE_BLOCKING; 365 br_log_state(p); 366 del_timer(&p->forward_delay_timer); 367 } 368} 369 370/* called under bridge lock */ 371static void br_make_forwarding(struct net_bridge_port *p) 372{ 373 if (p->state == BR_STATE_BLOCKING) { 374 if (p->br->stp_enabled == BR_KERNEL_STP) 375 p->state = BR_STATE_LISTENING; 376 else 377 p->state = BR_STATE_LEARNING; 378 379 br_log_state(p); 380 mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay); } 381} 382 383/* called under bridge lock */ 384void br_port_state_selection(struct net_bridge *br) 385{ 386 struct net_bridge_port *p; 387 388 /* Don't change port states if userspace is handling STP */ 389 if (br->stp_enabled == BR_USER_STP) 390 return; 391 392 list_for_each_entry(p, &br->port_list, list) { 393 if (p->state != BR_STATE_DISABLED) { 394 if (p->port_no == br->root_port) { 395 p->config_pending = 0; 396 p->topology_change_ack = 0; 397 br_make_forwarding(p); 398 } else if (br_is_designated_port(p)) { 399 del_timer(&p->message_age_timer); 400 br_make_forwarding(p); 401 } else { 402 p->config_pending = 0; 403 p->topology_change_ack = 0; 404 br_make_blocking(p); 405 } 406 } 407 408 } 409} 410 411/* called under bridge lock */ 412static inline void br_topology_change_acknowledge(struct net_bridge_port *p) 413{ 414 p->topology_change_ack = 1; 415 br_transmit_config(p); 416} 417 418/* called under bridge lock */ 419void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu) 420{ 421 struct net_bridge *br; 422 int was_root; 423 424 br = p->br; 425 was_root = br_is_root_bridge(br); 426 427 if (br_supersedes_port_info(p, bpdu)) { 428 br_record_config_information(p, bpdu); 429 br_configuration_update(br); 430 br_port_state_selection(br); 431 432 if (!br_is_root_bridge(br) && was_root) { 433 del_timer(&br->hello_timer); 434 if (br->topology_change_detected) { 435 del_timer(&br->topology_change_timer); 436 br_transmit_tcn(br); 437 438 mod_timer(&br->tcn_timer, 439 jiffies + br->bridge_hello_time); 440 } 441 } 442 443 if (p->port_no == br->root_port) { 444 br_record_config_timeout_values(br, bpdu); 445 br_config_bpdu_generation(br); 446 if (bpdu->topology_change_ack) 447 br_topology_change_acknowledged(br); 448 } 449 } else if (br_is_designated_port(p)) { 450 br_reply(p); 451 } 452} 453 454/* called under bridge lock */ 455void br_received_tcn_bpdu(struct net_bridge_port *p) 456{ 457 if (br_is_designated_port(p)) { 458 pr_info("%s: received tcn bpdu on port %i(%s)\n", 459 p->br->dev->name, p->port_no, p->dev->name); 460 461 br_topology_change_detection(p->br); 462 br_topology_change_acknowledge(p); 463 } 464} 465