/*
 *      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 STP tick.
 */
#define MESSAGE_AGE_INCR        ((HZ / 256) + 1)

static const char *const 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)
{
        br_info(p->br, "port %u(%s) entered %s state\n",
                (unsigned int) 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;
}

static void br_root_port_block(const struct net_bridge *br,
                               struct net_bridge_port *p)
{

        br_notice(br, "port %u(%s) tried to become root port (blocked)",
                  (unsigned int) p->port_no, p->dev->name);

        p->state = BR_STATE_LISTENING;
        br_log_state(p);
        br_ifinfo_notify(RTM_NEWLINK, p);

        if (br->forward_delay > 0)
                mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay);
}

/* 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))
                        continue;

                if (p->flags & BR_ROOT_BLOCK)
                        br_root_port_block(br, p);
                else
                        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 = (jiffies - root->designated_age)
                        + 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 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;
        p->designated_age = jiffies - bpdu->message_age;

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

/* called under bridge lock */
static 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)
{
        struct net_bridge_port *p;

        p = br_get_port(br, br->root_port);
        if (p)
                br_send_tcn_bpdu(p);
        else
                br_notice(br, "root port %u not found for topology notice\n",
                          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(const struct net_bridge_port *p,
                                   const 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;
        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);

        if (br->stp_enabled != BR_KERNEL_STP)
                return;

        br_info(br, "topology change detected, %s\n",
                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 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);
                br_ifinfo_notify(RTM_NEWLINK, 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->stp_enabled == BR_NO_STP || br->forward_delay == 0) {
                p->state = BR_STATE_FORWARDING;
                br_topology_change_detection(br);
                del_timer(&p->forward_delay_timer);
        } else if (br->stp_enabled == BR_KERNEL_STP)
                p->state = BR_STATE_LISTENING;
        else
                p->state = BR_STATE_LEARNING;

        br_multicast_enable_port(p);
        br_log_state(p);
        br_ifinfo_notify(RTM_NEWLINK, 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;
        unsigned int liveports = 0;

        list_for_each_entry(p, &br->port_list, list) {
                if (p->state == BR_STATE_DISABLED)
                        continue;

                /* Don't change port states if userspace is handling STP */
                if (br->stp_enabled != BR_USER_STP) {
                        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);
                        }
                }

                if (p->state == BR_STATE_FORWARDING)
                        ++liveports;
        }

        if (liveports == 0)
                netif_carrier_off(br->dev);
        else
                netif_carrier_on(br->dev);
}

/* called under bridge lock */
static 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,
                             const 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)) {
                br_info(p->br, "port %u(%s) received tcn bpdu\n",
                        (unsigned int) p->port_no, p->dev->name);

                br_topology_change_detection(p->br);
                br_topology_change_acknowledge(p);
        }
}

/* Change bridge STP parameter */
int br_set_hello_time(struct net_bridge *br, unsigned long val)
{
        unsigned long t = clock_t_to_jiffies(val);

        if (t < BR_MIN_HELLO_TIME || t > BR_MAX_HELLO_TIME)
                return -ERANGE;

        spin_lock_bh(&br->lock);
        br->bridge_hello_time = t;
        if (br_is_root_bridge(br))
                br->hello_time = br->bridge_hello_time;
        spin_unlock_bh(&br->lock);
        return 0;
}

int br_set_max_age(struct net_bridge *br, unsigned long val)
{
        unsigned long t = clock_t_to_jiffies(val);

        if (t < BR_MIN_MAX_AGE || t > BR_MAX_MAX_AGE)
                return -ERANGE;

        spin_lock_bh(&br->lock);
        br->bridge_max_age = t;
        if (br_is_root_bridge(br))
                br->max_age = br->bridge_max_age;
        spin_unlock_bh(&br->lock);
        return 0;

}

void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
{
        br->bridge_forward_delay = t;
        if (br_is_root_bridge(br))
                br->forward_delay = br->bridge_forward_delay;
}

int br_set_forward_delay(struct net_bridge *br, unsigned long val)
{
        unsigned long t = clock_t_to_jiffies(val);
        int err = -ERANGE;

        spin_lock_bh(&br->lock);
        if (br->stp_enabled != BR_NO_STP &&
            (t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
                goto unlock;

        __br_set_forward_delay(br, t);
        err = 0;

unlock:
        spin_unlock_bh(&br->lock);
        return err;
}