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/*

 *      Spanning tree protocol; generic parts

 *      Linux ethernet bridge

 *

 *      Authors:

 *      Lennert Buytenhek               <buytenh@gnu.org>

 *

 *      $Id: br_stp.c,v 1.1.1.1 2004-04-15 01:16:25 phoenix 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"

/* 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;

        bpdu.message_age = 0;

        if (!br_is_root_bridge(br)) {

                struct net_bridge_port *root;

                unsigned long age;

                root = br_get_port(br, br->root_port);

                age = br_timer_get_residue(&root->message_age_timer) + 1;

                bpdu.message_age = age;

        }

        bpdu.max_age = br->max_age;

        bpdu.hello_time = br->hello_time;

        bpdu.forward_delay = br->forward_delay;

        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);

}