net/bridge/br_stp.c

/*
 *	Spanning tree protocol; generic parts
 *	Linux ethernet bridge
 *
 *	Authors:
 *	Lennert Buytenhek		<buytenh@gnu.org>
 *
 *	$Id: br_stp.c,v 1.4 2000/06/19 10:13:35 davem Exp $
 *
 *	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/if_bridge.h>
#include <linux/smp_lock.h>
#include <asm/uaccess.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))

/* called under ioctl_lock or bridge lock */
int br_is_root_bridge(struct net_bridge *br)
{
	return !memcmp(&br->bridge_id, &br->designated_root, 8);
}

/* called under bridge lock */
int br_is_designated_port(struct net_bridge_port *p)
{
	return !memcmp(&p->designated_bridge, &p->br->bridge_id, 8) &&
		(p->designated_port == p->port_id);
}

/* called under ioctl_lock or bridge lock */
struct net_bridge_port *br_get_port(struct net_bridge *br, int port_no)
{
	struct net_bridge_port *p;

	p = br->port_list;
	while (p != NULL) {
		if (p->port_no == port_no)
			return p;

		p = p->next;
	}

	return NULL;
}

/* called under bridge lock */
static int br_should_become_root_port(struct net_bridge_port *p, int 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;
	int root_port;

	root_port = 0;

	p = br->port_list;
	while (p != NULL) {
		if (br_should_become_root_port(p, root_port))
			root_port = p->port_no;

		p = p->next;
	}

	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);
	br_timer_clear(&br->tcn_timer);

	br_timer_set(&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 (br_timer_is_running(&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;

		root = br_get_port(br, br->root_port);
		bpdu.message_age =  br_timer_get_residue(&root->message_age_timer)
			+ 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;
		br_timer_set(&p->hold_timer, jiffies);
	}
}

/* called under bridge lock */
static void br_record_config_information(struct net_bridge_port *p, 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;

	br_timer_set(&p->message_age_timer, jiffies + 
		     (p->br->max_age - bpdu->message_age));
}

/* called under bridge lock */
static void br_record_config_timeout_values(struct net_bridge *br, 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(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;

	p = br->port_list;
	while (p != NULL) {
		if (p->state != BR_STATE_DISABLED &&
		    br_should_become_designated_port(p))
			br_become_designated_port(p);

		p = p->next;
	}
}

/* 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 void br_topology_change_acknowledged(struct net_bridge *br)
{
	br->topology_change_detected = 0;
	br_timer_clear(&br->tcn_timer);
}

/* called under bridge lock */
void br_topology_change_detection(struct net_bridge *br)
{
	printk(KERN_INFO "%s: topology change detected", br->dev.name);

	if (br_is_root_bridge(br)) {
		printk(", propagating");
		br->topology_change = 1;
		br_timer_set(&br->topology_change_timer, jiffies);
	} else if (!br->topology_change_detected) {
		printk(", sending tcn bpdu");
		br_transmit_tcn(br);
		br_timer_set(&br->tcn_timer, jiffies);
	}

	printk("\n");
	br->topology_change_detected = 1;
}

/* called under bridge lock */
void br_config_bpdu_generation(struct net_bridge *br)
{
	struct net_bridge_port *p;

	p = br->port_list;
	while (p != NULL) {
		if (p->state != BR_STATE_DISABLED &&
		    br_is_designated_port(p))
			br_transmit_config(p);

		p = p->next;
	}
}

/* called under bridge lock */
static 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);

		printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
		       p->br->dev.name, p->port_no, p->dev->name, "blocking");

		p->state = BR_STATE_BLOCKING;
		br_timer_clear(&p->forward_delay_timer);
	}
}

/* called under bridge lock */
static void br_make_forwarding(struct net_bridge_port *p)
{
	if (p->state == BR_STATE_BLOCKING) {
		if (p->br->stp_enabled) {
			printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
			       p->br->dev.name, p->port_no, p->dev->name,
			       "listening");

			p->state = BR_STATE_LISTENING;
		} else {
			printk(KERN_INFO "%s: port %i(%s) entering %s state\n",
			       p->br->dev.name, p->port_no, p->dev->name,
			       "learning");

			p->state = BR_STATE_LEARNING;
		}
		br_timer_set(&p->forward_delay_timer, jiffies);
	}
}

/* called under bridge lock */
void br_port_state_selection(struct net_bridge *br)
{
	struct net_bridge_port *p;

	p = br->port_list;
	while (p != NULL) {
		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)) {
				br_timer_clear(&p->message_age_timer);
				br_make_forwarding(p);
			} else {
				p->config_pending = 0;
				p->topology_change_ack = 0;
				br_make_blocking(p);
			}
		}

		p = p->next;
	}
}

/* called under bridge lock */
static void br_topology_change_acknowledge(struct net_bridge_port *p)
{
	p->topology_change_ack = 1;
	br_transmit_config(p);
}

/* lock-safe */
void br_received_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
{
	struct net_bridge *br;
	int was_root;

	if (p->state == BR_STATE_DISABLED)
		return;

	br = p->br;
	read_lock(&br->lock);

	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) {
			br_timer_clear(&br->hello_timer);
			if (br->topology_change_detected) {
				br_timer_clear(&br->topology_change_timer);
				br_transmit_tcn(br);
				br_timer_set(&br->tcn_timer, jiffies);
			}
		}

		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);		
	}

	read_unlock(&br->lock);
}

/* lock-safe */
void br_received_tcn_bpdu(struct net_bridge_port *p)
{
	read_lock(&p->br->lock);
	if (p->state != BR_STATE_DISABLED &&
	    br_is_designated_port(p)) {
		printk(KERN_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);
	}
	read_unlock(&p->br->lock);
}