text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   *	Spanning tree protocol; interface code
   *	Linux ethernet bridge
   *
   *	Authors:
   *	Lennert Buytenhek		<buytenh@gnu.org>
   */
  
  #include <linux/kernel.h>
  #include <linux/kmod.h>
  #include <linux/etherdevice.h>
  #include <linux/rtnetlink.h>
  #include <net/switchdev.h>
  
  #include "br_private.h"
  #include "br_private_stp.h"
  
  
  /* Port id is composed of priority and port number.
   * NB: some bits of priority are dropped to
   *     make room for more ports.
   */
  static inline port_id br_make_port_id(__u8 priority, __u16 port_no)
  {
  	return ((u16)priority << BR_PORT_BITS)
  		| (port_no & ((1<<BR_PORT_BITS)-1));
  }
  
  #define BR_MAX_PORT_PRIORITY ((u16)~0 >> BR_PORT_BITS)
  
  /* called under bridge lock */
  void br_init_port(struct net_bridge_port *p)
  {
  	int err;
  
  	p->port_id = br_make_port_id(p->priority, p->port_no);
  	br_become_designated_port(p);
  	br_set_state(p, BR_STATE_BLOCKING);
  	p->topology_change_ack = 0;
  	p->config_pending = 0;
  
  	err = __set_ageing_time(p->dev, p->br->ageing_time);
  	if (err)
  		netdev_err(p->dev, "failed to offload ageing time\n");
  }
  
  /* NO locks held */
  void br_stp_enable_bridge(struct net_bridge *br)
  {
  	struct net_bridge_port *p;
  
  	spin_lock_bh(&br->lock);
  	if (br->stp_enabled == BR_KERNEL_STP)
  		mod_timer(&br->hello_timer, jiffies + br->hello_time);
  	mod_delayed_work(system_long_wq, &br->gc_work, HZ / 10);
  
  	br_config_bpdu_generation(br);
  
  	list_for_each_entry(p, &br->port_list, list) {
  		if (netif_running(p->dev) && netif_oper_up(p->dev))
  			br_stp_enable_port(p);
  
  	}
  	spin_unlock_bh(&br->lock);
  }
  
  /* NO locks held */
  void br_stp_disable_bridge(struct net_bridge *br)
  {
  	struct net_bridge_port *p;
  
  	spin_lock_bh(&br->lock);
  	list_for_each_entry(p, &br->port_list, list) {
  		if (p->state != BR_STATE_DISABLED)
  			br_stp_disable_port(p);
  
  	}
  
  	__br_set_topology_change(br, 0);
  	br->topology_change_detected = 0;
  	spin_unlock_bh(&br->lock);
  
  	del_timer_sync(&br->hello_timer);
  	del_timer_sync(&br->topology_change_timer);
  	del_timer_sync(&br->tcn_timer);
  	cancel_delayed_work_sync(&br->gc_work);
  }
  
  /* called under bridge lock */
  void br_stp_enable_port(struct net_bridge_port *p)
  {
  	br_init_port(p);
  	br_port_state_selection(p->br);
  	br_ifinfo_notify(RTM_NEWLINK, NULL, p);
  }
  
  /* called under bridge lock */
  void br_stp_disable_port(struct net_bridge_port *p)
  {
  	struct net_bridge *br = p->br;
  	int wasroot;
  
  	wasroot = br_is_root_bridge(br);
  	br_become_designated_port(p);
  	br_set_state(p, BR_STATE_DISABLED);
  	p->topology_change_ack = 0;
  	p->config_pending = 0;
  
  	br_ifinfo_notify(RTM_NEWLINK, NULL, p);
  
  	del_timer(&p->message_age_timer);
  	del_timer(&p->forward_delay_timer);
  	del_timer(&p->hold_timer);
  
  	if (!rcu_access_pointer(p->backup_port))
  		br_fdb_delete_by_port(br, p, 0, 0);
  	br_multicast_disable_port(p);
  
  	br_configuration_update(br);
  
  	br_port_state_selection(br);
  
  	if (br_is_root_bridge(br) && !wasroot)
  		br_become_root_bridge(br);
  }
  
  static int br_stp_call_user(struct net_bridge *br, char *arg)
  {
  	char *argv[] = { BR_STP_PROG, br->dev->name, arg, NULL };
  	char *envp[] = { NULL };
  	int rc;
  
  	/* call userspace STP and report program errors */
  	rc = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
  	if (rc > 0) {
  		if (rc & 0xff)
  			br_debug(br, BR_STP_PROG " received signal %d\n",
  				 rc & 0x7f);
  		else
  			br_debug(br, BR_STP_PROG " exited with code %d\n",
  				 (rc >> 8) & 0xff);
  	}
  
  	return rc;
  }
  
  static void br_stp_start(struct net_bridge *br)
  {
  	int err = -ENOENT;
  
  	if (net_eq(dev_net(br->dev), &init_net))
  		err = br_stp_call_user(br, "start");
  
  	if (err && err != -ENOENT)
  		br_err(br, "failed to start userspace STP (%d)\n", err);
  
  	spin_lock_bh(&br->lock);
  
  	if (br->bridge_forward_delay < BR_MIN_FORWARD_DELAY)
  		__br_set_forward_delay(br, BR_MIN_FORWARD_DELAY);
  	else if (br->bridge_forward_delay > BR_MAX_FORWARD_DELAY)
  		__br_set_forward_delay(br, BR_MAX_FORWARD_DELAY);
  
  	if (!err) {
  		br->stp_enabled = BR_USER_STP;
  		br_debug(br, "userspace STP started\n");
  	} else {
  		br->stp_enabled = BR_KERNEL_STP;
  		br_debug(br, "using kernel STP\n");
  
  		/* To start timers on any ports left in blocking */
  		if (br->dev->flags & IFF_UP)
  			mod_timer(&br->hello_timer, jiffies + br->hello_time);
  		br_port_state_selection(br);
  	}
  
  	spin_unlock_bh(&br->lock);
  }
  
  static void br_stp_stop(struct net_bridge *br)
  {
  	int err;
  
  	if (br->stp_enabled == BR_USER_STP) {
  		err = br_stp_call_user(br, "stop");
  		if (err)
  			br_err(br, "failed to stop userspace STP (%d)\n", err);
  
  		/* To start timers on any ports left in blocking */
  		spin_lock_bh(&br->lock);
  		br_port_state_selection(br);
  		spin_unlock_bh(&br->lock);
  	}
  
  	br->stp_enabled = BR_NO_STP;
  }
  
  void br_stp_set_enabled(struct net_bridge *br, unsigned long val)
  {
  	ASSERT_RTNL();
  
  	if (val) {
  		if (br->stp_enabled == BR_NO_STP)
  			br_stp_start(br);
  	} else {
  		if (br->stp_enabled != BR_NO_STP)
  			br_stp_stop(br);
  	}
  }
  
  /* called under bridge lock */
  void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr)
  {
  	/* should be aligned on 2 bytes for ether_addr_equal() */
  	unsigned short oldaddr_aligned[ETH_ALEN >> 1];
  	unsigned char *oldaddr = (unsigned char *)oldaddr_aligned;
  	struct net_bridge_port *p;
  	int wasroot;
  
  	wasroot = br_is_root_bridge(br);
  
  	br_fdb_change_mac_address(br, addr);
  
  	memcpy(oldaddr, br->bridge_id.addr, ETH_ALEN);
  	memcpy(br->bridge_id.addr, addr, ETH_ALEN);
  	memcpy(br->dev->dev_addr, addr, ETH_ALEN);
  
  	list_for_each_entry(p, &br->port_list, list) {
  		if (ether_addr_equal(p->designated_bridge.addr, oldaddr))
  			memcpy(p->designated_bridge.addr, addr, ETH_ALEN);
  
  		if (ether_addr_equal(p->designated_root.addr, oldaddr))
  			memcpy(p->designated_root.addr, addr, ETH_ALEN);
  	}
  
  	br_configuration_update(br);
  	br_port_state_selection(br);
  	if (br_is_root_bridge(br) && !wasroot)
  		br_become_root_bridge(br);
  }
  
  /* should be aligned on 2 bytes for ether_addr_equal() */
  static const unsigned short br_mac_zero_aligned[ETH_ALEN >> 1];
  
  /* called under bridge lock */
  bool br_stp_recalculate_bridge_id(struct net_bridge *br)
  {
  	const unsigned char *br_mac_zero =
  			(const unsigned char *)br_mac_zero_aligned;
  	const unsigned char *addr = br_mac_zero;
  	struct net_bridge_port *p;
  
  	/* user has chosen a value so keep it */
  	if (br->dev->addr_assign_type == NET_ADDR_SET)
  		return false;
  
  	list_for_each_entry(p, &br->port_list, list) {
  		if (addr == br_mac_zero ||
  		    memcmp(p->dev->dev_addr, addr, ETH_ALEN) < 0)
  			addr = p->dev->dev_addr;
  
  	}
  
  	if (ether_addr_equal(br->bridge_id.addr, addr))
  		return false;	/* no change */
  
  	br_stp_change_bridge_id(br, addr);
  	return true;
  }
  
  /* Acquires and releases bridge lock */
  void br_stp_set_bridge_priority(struct net_bridge *br, u16 newprio)
  {
  	struct net_bridge_port *p;
  	int wasroot;
  
  	spin_lock_bh(&br->lock);
  	wasroot = br_is_root_bridge(br);
  
  	list_for_each_entry(p, &br->port_list, list) {
  		if (p->state != BR_STATE_DISABLED &&
  		    br_is_designated_port(p)) {
  			p->designated_bridge.prio[0] = (newprio >> 8) & 0xFF;
  			p->designated_bridge.prio[1] = newprio & 0xFF;
  		}
  
  	}
  
  	br->bridge_id.prio[0] = (newprio >> 8) & 0xFF;
  	br->bridge_id.prio[1] = newprio & 0xFF;
  	br_configuration_update(br);
  	br_port_state_selection(br);
  	if (br_is_root_bridge(br) && !wasroot)
  		br_become_root_bridge(br);
  	spin_unlock_bh(&br->lock);
  }
  
  /* called under bridge lock */
  int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio)
  {
  	port_id new_port_id;
  
  	if (newprio > BR_MAX_PORT_PRIORITY)
  		return -ERANGE;
  
  	new_port_id = br_make_port_id(newprio, p->port_no);
  	if (br_is_designated_port(p))
  		p->designated_port = new_port_id;
  
  	p->port_id = new_port_id;
  	p->priority = newprio;
  	if (!memcmp(&p->br->bridge_id, &p->designated_bridge, 8) &&
  	    p->port_id < p->designated_port) {
  		br_become_designated_port(p);
  		br_port_state_selection(p->br);
  	}
  
  	return 0;
  }
  
  /* called under bridge lock */
  int br_stp_set_path_cost(struct net_bridge_port *p, unsigned long path_cost)
  {
  	if (path_cost < BR_MIN_PATH_COST ||
  	    path_cost > BR_MAX_PATH_COST)
  		return -ERANGE;
  
  	p->flags |= BR_ADMIN_COST;
  	p->path_cost = path_cost;
  	br_configuration_update(p->br);
  	br_port_state_selection(p->br);
  	return 0;
  }
  
  ssize_t br_show_bridge_id(char *buf, const struct bridge_id *id)
  {
  	return sprintf(buf, "%.2x%.2x.%.2x%.2x%.2x%.2x%.2x%.2x\n",
  	       id->prio[0], id->prio[1],
  	       id->addr[0], id->addr[1], id->addr[2],
  	       id->addr[3], id->addr[4], id->addr[5]);
  }
  