/*
 *      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_config_bpdu_generation(br);
        br_timer_set(&br->hello_timer, jiffies);
}

/* 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 - 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);
}