/* * Spanning tree protocol; generic parts * Linux ethernet bridge * * Authors: * Lennert Buytenhek <buytenh@gnu.org> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/kernel.h> #include <linux/rculist.h> #include "br_private.h" #include "br_private_stp.h" /* since time values in bpdu are in jiffies and then scaled (1/256) * before sending, make sure that is at least one. */ #define MESSAGE_AGE_INCR ((HZ < 256) ? 1 : (HZ/256)) static const char *br_port_state_names[] = { [BR_STATE_DISABLED] = "disabled", [BR_STATE_LISTENING] = "listening", [BR_STATE_LEARNING] = "learning", [BR_STATE_FORWARDING] = "forwarding", [BR_STATE_BLOCKING] = "blocking", }; void br_log_state(const struct net_bridge_port *p) { pr_info("%s: port %d(%s) entering %s state\n", p->br->dev->name, p->port_no, p->dev->name, br_port_state_names[p->state]); } /* called under bridge lock */ struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no) { struct net_bridge_port *p; list_for_each_entry_rcu(p, &br->port_list, list) { if (p->port_no == port_no) return p; } return NULL; } /* called under bridge lock */ static int br_should_become_root_port(const struct net_bridge_port *p, u16 root_port) { struct net_bridge *br; struct net_bridge_port *rp; int t; br = p->br; if (p->state == BR_STATE_DISABLED || br_is_designated_port(p)) return 0; if (memcmp(&br->bridge_id, &p->designated_root, 8) <= 0) return 0; if (!root_port) return 1; rp = br_get_port(br, root_port); t = memcmp(&p->designated_root, &rp->designated_root, 8); if (t < 0) return 1; else if (t > 0) return 0; if (p->designated_cost + p->path_cost < rp->designated_cost + rp->path_cost) return 1; else if (p->designated_cost + p->path_cost > rp->designated_cost + rp->path_cost) return 0; t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8); if (t < 0) return 1; else if (t > 0) return 0; if (p->designated_port < rp->designated_port) return 1; else if (p->designated_port > rp->designated_port) return 0; if (p->port_id < rp->port_id) return 1; return 0; } /* called under bridge lock */ static void br_root_selection(struct net_bridge *br) { struct net_bridge_port *p; u16 root_port = 0; list_for_each_entry(p, &br->port_list, list) { if (br_should_become_root_port(p, root_port)) root_port = p->port_no; } br->root_port = root_port; if (!root_port) { br->designated_root = br->bridge_id; br->root_path_cost = 0; } else { p = br_get_port(br, root_port); br->designated_root = p->designated_root; br->root_path_cost = p->designated_cost + p->path_cost; } } /* called under bridge lock */ void br_become_root_bridge(struct net_bridge *br) { br->max_age = br->bridge_max_age; br->hello_time = br->bridge_hello_time; br->forward_delay = br->bridge_forward_delay; br_topology_change_detection(br); del_timer(&br->tcn_timer); if (br->dev->flags & IFF_UP) { br_config_bpdu_generation(br); mod_timer(&br->hello_timer, jiffies + br->hello_time); } } /* called under bridge lock */ void br_transmit_config(struct net_bridge_port *p) { struct br_config_bpdu bpdu; struct net_bridge *br; if (timer_pending(&p->hold_timer)) { p->config_pending = 1; return; } br = p->br; bpdu.topology_change = br->topology_change; bpdu.topology_change_ack = p->topology_change_ack; bpdu.root = br->designated_root; bpdu.root_path_cost = br->root_path_cost; bpdu.bridge_id = br->bridge_id; bpdu.port_id = p->port_id; if (br_is_root_bridge(br)) bpdu.message_age = 0; else { struct net_bridge_port *root = br_get_port(br, br->root_port); bpdu.message_age = br->max_age - (root->message_age_timer.expires - jiffies) + MESSAGE_AGE_INCR; } bpdu.max_age = br->max_age; bpdu.hello_time = br->hello_time; bpdu.forward_delay = br->forward_delay; if (bpdu.message_age < br->max_age) { br_send_config_bpdu(p, &bpdu); p->topology_change_ack = 0; p->config_pending = 0; mod_timer(&p->hold_timer, round_jiffies(jiffies + BR_HOLD_TIME)); } } /* called under bridge lock */ static inline void br_record_config_information(struct net_bridge_port *p, const struct br_config_bpdu *bpdu) { p->designated_root = bpdu->root; p->designated_cost = bpdu->root_path_cost; p->designated_bridge = bpdu->bridge_id; p->designated_port = bpdu->port_id; mod_timer(&p->message_age_timer, jiffies + (p->br->max_age - bpdu->message_age)); } /* called under bridge lock */ static inline void br_record_config_timeout_values(struct net_bridge *br, const struct br_config_bpdu *bpdu) { br->max_age = bpdu->max_age; br->hello_time = bpdu->hello_time; br->forward_delay = bpdu->forward_delay; br->topology_change = bpdu->topology_change; } /* called under bridge lock */ void br_transmit_tcn(struct net_bridge *br) { br_send_tcn_bpdu(br_get_port(br, br->root_port)); } /* called under bridge lock */ static int br_should_become_designated_port(const struct net_bridge_port *p) { struct net_bridge *br; int t; br = p->br; if (br_is_designated_port(p)) return 1; if (memcmp(&p->designated_root, &br->designated_root, 8)) return 1; if (br->root_path_cost < p->designated_cost) return 1; else if (br->root_path_cost > p->designated_cost) return 0; t = memcmp(&br->bridge_id, &p->designated_bridge, 8); if (t < 0) return 1; else if (t > 0) return 0; if (p->port_id < p->designated_port) return 1; return 0; } /* called under bridge lock */ static void br_designated_port_selection(struct net_bridge *br) { struct net_bridge_port *p; list_for_each_entry(p, &br->port_list, list) { if (p->state != BR_STATE_DISABLED && br_should_become_designated_port(p)) br_become_designated_port(p); } } /* called under bridge lock */ static int br_supersedes_port_info(struct net_bridge_port *p, struct br_config_bpdu *bpdu) { int t; t = memcmp(&bpdu->root, &p->designated_root, 8); if (t < 0) return 1; else if (t > 0) return 0; if (bpdu->root_path_cost < p->designated_cost) return 1; else if (bpdu->root_path_cost > p->designated_cost) return 0; t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8); if (t < 0) return 1; else if (t > 0) return 0; if (memcmp(&bpdu->bridge_id, &p->br->bridge_id, 8)) return 1; if (bpdu->port_id <= p->designated_port) return 1; return 0; } /* called under bridge lock */ static inline void br_topology_change_acknowledged(struct net_bridge *br) { br->topology_change_detected = 0; del_timer(&br->tcn_timer); } /* called under bridge lock */ void br_topology_change_detection(struct net_bridge *br) { int isroot = br_is_root_bridge(br); pr_info("%s: topology change detected, %s\n", br->dev->name, isroot ? "propagating" : "sending tcn bpdu"); if (isroot) { br->topology_change = 1; mod_timer(&br->topology_change_timer, jiffies + br->bridge_forward_delay + br->bridge_max_age); } else if (!br->topology_change_detected) { br_transmit_tcn(br); mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time); } br->topology_change_detected = 1; } /* called under bridge lock */ void br_config_bpdu_generation(struct net_bridge *br) { struct net_bridge_port *p; list_for_each_entry(p, &br->port_list, list) { if (p->state != BR_STATE_DISABLED && br_is_designated_port(p)) br_transmit_config(p); } } /* called under bridge lock */ static inline void br_reply(struct net_bridge_port *p) { br_transmit_config(p); } /* called under bridge lock */ void br_configuration_update(struct net_bridge *br) { br_root_selection(br); br_designated_port_selection(br); } /* called under bridge lock */ void br_become_designated_port(struct net_bridge_port *p) { struct net_bridge *br; br = p->br; p->designated_root = br->designated_root; p->designated_cost = br->root_path_cost; p->designated_bridge = br->bridge_id; p->designated_port = p->port_id; } /* called under bridge lock */ static void br_make_blocking(struct net_bridge_port *p) { if (p->state != BR_STATE_DISABLED && p->state != BR_STATE_BLOCKING) { if (p->state == BR_STATE_FORWARDING || p->state == BR_STATE_LEARNING) br_topology_change_detection(p->br); p->state = BR_STATE_BLOCKING; br_log_state(p); del_timer(&p->forward_delay_timer); } } /* called under bridge lock */ static void br_make_forwarding(struct net_bridge_port *p) { struct net_bridge *br = p->br; if (p->state != BR_STATE_BLOCKING) return; if (br->forward_delay == 0) { p->state = BR_STATE_FORWARDING; br_topology_change_detection(br); del_timer(&p->forward_delay_timer); } else if (p->br->stp_enabled == BR_KERNEL_STP) p->state = BR_STATE_LISTENING; else p->state = BR_STATE_LEARNING; br_log_state(p); if (br->forward_delay != 0) mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay); } /* called under bridge lock */ void br_port_state_selection(struct net_bridge *br) { struct net_bridge_port *p; /* Don't change port states if userspace is handling STP */ if (br->stp_enabled == BR_USER_STP) return; list_for_each_entry(p, &br->port_list, list) { if (p->state != BR_STATE_DISABLED) { if (p->port_no == br->root_port) { p->config_pending = 0; p->topology_change_ack = 0; br_make_forwarding(p); } else if (br_is_designated_port(p)) { del_timer(&p->message_age_timer); br_make_forwarding(p); } else { p->config_pending = 0; p->topology_change_ack = 0; br_make_blocking(p); } } } } /* called under bridge lock */ static inline void br_topology_change_acknowledge(struct net_bridge_port *p) { p->topology_change_ack = 1; br_transmit_config(p); } /* called under bridge lock */ void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu) { struct net_bridge *br; int was_root; br = p->br; was_root = br_is_root_bridge(br); if (br_supersedes_port_info(p, bpdu)) { br_record_config_information(p, bpdu); br_configuration_update(br); br_port_state_selection(br); if (!br_is_root_bridge(br) && was_root) { del_timer(&br->hello_timer); if (br->topology_change_detected) { del_timer(&br->topology_change_timer); br_transmit_tcn(br); mod_timer(&br->tcn_timer, jiffies + br->bridge_hello_time); } } if (p->port_no == br->root_port) { br_record_config_timeout_values(br, bpdu); br_config_bpdu_generation(br); if (bpdu->topology_change_ack) br_topology_change_acknowledged(br); } } else if (br_is_designated_port(p)) { br_reply(p); } } /* called under bridge lock */ void br_received_tcn_bpdu(struct net_bridge_port *p) { if (br_is_designated_port(p)) { pr_info("%s: received tcn bpdu on port %i(%s)\n", p->br->dev->name, p->port_no, p->dev->name); br_topology_change_detection(p->br); br_topology_change_acknowledge(p); } }