/*
   *	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 <net/switchdev.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_set_state(struct net_bridge_port *p, unsigned int state)
  {

  	struct switchdev_attr attr = {

  		.orig_dev = p->dev,

  		.id = SWITCHDEV_ATTR_ID_PORT_STP_STATE,

  		.flags = SWITCHDEV_F_DEFER,

  		.u.stp_state = state,

  	};

  	int err;

  	p->state = state;

  	err = switchdev_port_attr_set(p->dev, &attr);

  	if (err && err != -EOPNOTSUPP)

  		br_warn(p->br, "error setting offload STP state on port %u(%s)
  ",
  				(unsigned int) p->port_no, p->dev->name);

  	else
  		br_info(p->br, "port %u(%s) entered %s state
  ",
  				(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);

  	br_set_state(p, BR_STATE_LISTENING);

  	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;

  		if (p->br->stp_enabled == BR_KERNEL_STP)
  			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_set_topology_change(br, 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
  ",
  			  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
  ",

  		isroot ? "propagating" : "sending tcn bpdu");
  
  	if (isroot) {

  		__br_set_topology_change(br, 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);

  		br_set_state(p, BR_STATE_BLOCKING);

  		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) {

  		br_set_state(p, BR_STATE_FORWARDING);

  		br_topology_change_detection(br);
  		del_timer(&p->forward_delay_timer);

  	} else if (br->stp_enabled == BR_KERNEL_STP)

  		br_set_state(p, BR_STATE_LISTENING);

  	else

  		br_set_state(p, BR_STATE_LEARNING);

  	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_BLOCKING)
  			br_multicast_enable_port(p);

  		/* Multicast is not disabled for the port when it goes in
  		 * blocking state because the timers will expire and stop by
  		 * themselves without sending more queries.
  		 */

  		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
  ",

  			(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;
  
  }

  /* called under bridge lock */
  int __set_ageing_time(struct net_device *dev, unsigned long t)
  {
  	struct switchdev_attr attr = {
  		.orig_dev = dev,
  		.id = SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME,
  		.flags = SWITCHDEV_F_SKIP_EOPNOTSUPP | SWITCHDEV_F_DEFER,
  		.u.ageing_time = jiffies_to_clock_t(t),
  	};
  	int err;
  
  	err = switchdev_port_attr_set(dev, &attr);
  	if (err && err != -EOPNOTSUPP)
  		return err;
  
  	return 0;
  }

  /* Set time interval that dynamic forwarding entries live
   * For pure software bridge, allow values outside the 802.1
   * standard specification for special cases:
   *  0 - entry never ages (all permanant)
   *  1 - entry disappears (no persistance)
   *
   * Offloaded switch entries maybe more restrictive
   */

  int br_set_ageing_time(struct net_bridge *br, clock_t ageing_time)

  {

  	unsigned long t = clock_t_to_jiffies(ageing_time);
  	int err;

  	err = __set_ageing_time(br->dev, t);
  	if (err)

  		return err;

  	spin_lock_bh(&br->lock);
  	br->bridge_ageing_time = t;

  	br->ageing_time = t;

  	spin_unlock_bh(&br->lock);

  	mod_delayed_work(system_long_wq, &br->gc_work, 0);

  
  	return 0;
  }

  /* called under bridge lock */
  void __br_set_topology_change(struct net_bridge *br, unsigned char val)
  {

  	unsigned long t;
  	int err;
  
  	if (br->stp_enabled == BR_KERNEL_STP && br->topology_change != val) {
  		/* On topology change, set the bridge ageing time to twice the
  		 * forward delay. Otherwise, restore its default ageing time.
  		 */
  
  		if (val) {
  			t = 2 * br->forward_delay;
  			br_debug(br, "decreasing ageing time to %lu
  ", t);
  		} else {
  			t = br->bridge_ageing_time;
  			br_debug(br, "restoring ageing time to %lu
  ", t);
  		}
  
  		err = __set_ageing_time(br->dev, t);
  		if (err)
  			br_warn(br, "error offloading ageing time
  ");
  		else
  			br->ageing_time = t;
  	}

  	br->topology_change = val;
  }

  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;

  }