text: /*
   * Copyright (c) 2000 Jason L. Wright (jason@thought.net)
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *      This product includes software developed by Jason L. Wright
   * 4. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   * $OpenBSD: bridgestp.c,v 1.5 2001/03/22 03:48:29 jason Exp $
   * $NetBSD: bridgestp.c,v 1.5 2003/11/28 08:56:48 keihan Exp $
   * $FreeBSD: src/sys/net/bridgestp.c,v 1.7 2005/10/11 02:58:32 thompsa Exp $
   */
  
  /*
   * Implementation of the spanning tree protocol as defined in
   * ISO/IEC Final DIS 15802-3 (IEEE P802.1D/D17), May 25, 1998.
   * (In English: IEEE 802.1D, Draft 17, 1998)
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/malloc.h>	/* for M_NOWAIT */
  #include <sys/mbuf.h>
  #include <sys/socket.h>
  #include <sys/sockio.h>
  #include <sys/kernel.h>
  #include <sys/callout.h>
  #include <sys/proc.h>
  #include <sys/lock.h>
  #include <sys/thread.h>
  #include <sys/thread2.h>
  #include <sys/msgport2.h>
  
  #include <net/if.h>
  #include <net/if_dl.h>
  #include <net/if_types.h>
  #include <net/if_llc.h>
  #include <net/if_media.h>
  
  #include <netinet/in.h>
  #include <netinet/in_systm.h>
  #include <netinet/in_var.h>
  #include <netinet/if_ether.h>
  #include <net/bridge/if_bridgevar.h>
  
  /* BPDU message types */
  #define	BSTP_MSGTYPE_CFG	0x00		/* Configuration */
  #define	BSTP_MSGTYPE_TCN	0x80		/* Topology chg notification */
  
  /* BPDU flags */
  #define	BSTP_FLAG_TC		0x01		/* Topology change */
  #define	BSTP_FLAG_TCA		0x80		/* Topology change ack */
  
  #define	BSTP_MESSAGE_AGE_INCR	(1 * 256)	/* in 256ths of a second */
  #define	BSTP_TICK_VAL		(1 * 256)	/* in 256ths of a second */
  
  /*
   * Because BPDU's do not make nicely aligned structures, two different
   * declarations are used: bstp_?bpdu (wire representation, packed) and
   * bstp_*_unit (internal, nicely aligned version).
   */
  
  /* configuration bridge protocol data unit */
  struct bstp_cbpdu {
  	uint8_t		cbu_dsap;		/* LLC: destination sap */
  	uint8_t		cbu_ssap;		/* LLC: source sap */
  	uint8_t		cbu_ctl;		/* LLC: control */
  	uint16_t	cbu_protoid;		/* protocol id */
  	uint8_t		cbu_protover;		/* protocol version */
  	uint8_t		cbu_bpdutype;		/* message type */
  	uint8_t		cbu_flags;		/* flags (below) */
  
  	/* root id */
  	uint16_t	cbu_rootpri;		/* root priority */
  	uint8_t	cbu_rootaddr[6];	/* root address */
  
  	uint32_t	cbu_rootpathcost;	/* root path cost */
  
  	/* bridge id */
  	uint16_t	cbu_bridgepri;		/* bridge priority */
  	uint8_t		cbu_bridgeaddr[6];	/* bridge address */
  
  	uint16_t	cbu_portid;		/* port id */
  	uint16_t	cbu_messageage;		/* current message age */
  	uint16_t	cbu_maxage;		/* maximum age */
  	uint16_t	cbu_hellotime;		/* hello time */
  	uint16_t	cbu_forwarddelay;	/* forwarding delay */
  } __attribute__((__packed__));
  
  /* topology change notification bridge protocol data unit */
  struct bstp_tbpdu {
  	uint8_t		tbu_dsap;		/* LLC: destination sap */
  	uint8_t		tbu_ssap;		/* LLC: source sap */
  	uint8_t		tbu_ctl;		/* LLC: control */
  	uint16_t	tbu_protoid;		/* protocol id */
  	uint8_t		tbu_protover;		/* protocol version */
  	uint8_t		tbu_bpdutype;		/* message type */
  } __attribute__((__packed__));
  
  const uint8_t bstp_etheraddr[] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  
  static void	bstp_initialize_port(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_ifupdstatus(struct bridge_softc *, struct bridge_iflist *);
  static void	bstp_enable_port(struct bridge_softc *, struct bridge_iflist *);
  static void	bstp_disable_port(struct bridge_softc *,
  		    struct bridge_iflist *);
  #ifdef notused
  static void	bstp_enable_change_detection(struct bridge_iflist *);
  static void	bstp_disable_change_detection(struct bridge_iflist *);
  #endif /* notused */
  static int	bstp_root_bridge(struct bridge_softc *sc);
  static void	bstp_transmit_config(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_transmit_tcn(struct bridge_softc *);
  static void	bstp_received_config_bpdu(struct bridge_softc *,
  		    struct bridge_iflist *, struct bstp_config_unit *);
  static void	bstp_received_tcn_bpdu(struct bridge_softc *,
  		    struct bridge_iflist *, struct bstp_tcn_unit *);
  static void	bstp_record_config_information(struct bridge_softc *,
  		    struct bridge_iflist *, struct bstp_config_unit *);
  static void	bstp_record_config_timeout_values(struct bridge_softc *,
  		    struct bstp_config_unit *);
  static void	bstp_config_bpdu_generation(struct bridge_softc *);
  static void	bstp_send_config_bpdu(struct bridge_softc *,
  		    struct bridge_iflist *, struct bstp_config_unit *);
  static void	bstp_configuration_update(struct bridge_softc *);
  static void	bstp_port_state_selection(struct bridge_softc *);
  static void	bstp_clear_peer_info(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_make_forwarding(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_make_blocking(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_make_l1blocking(struct bridge_softc *sc,
  		    struct bridge_iflist *bif);
  static void	bstp_adjust_bonded_states(struct bridge_softc *sc,
  		    struct bridge_iflist *obif);
  static void	bstp_set_port_state(struct bridge_iflist *, uint8_t);
  #ifdef notused
  static void	bstp_set_bridge_priority(struct bridge_softc *, uint64_t);
  static void	bstp_set_port_priority(struct bridge_softc *,
  		    struct bridge_iflist *, uint16_t);
  static void	bstp_set_path_cost(struct bridge_softc *,
  		    struct bridge_iflist *, uint32_t);
  #endif /* notused */
  static void	bstp_topology_change_detection(struct bridge_softc *);
  static void	bstp_topology_change_acknowledged(struct bridge_softc *);
  static void	bstp_acknowledge_topology_change(struct bridge_softc *,
  		    struct bridge_iflist *);
  
  static void	bstp_tick(void *);
  static void	bstp_timer_start(struct bridge_timer *, uint16_t);
  static void	bstp_timer_stop(struct bridge_timer *);
  static int	bstp_timer_expired(struct bridge_timer *, uint16_t);
  
  static void	bstp_hold_timer_expiry(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_message_age_timer_expiry(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_forward_delay_timer_expiry(struct bridge_softc *,
  		    struct bridge_iflist *);
  static void	bstp_topology_change_timer_expiry(struct bridge_softc *);
  static void	bstp_tcn_timer_expiry(struct bridge_softc *);
  static void	bstp_hello_timer_expiry(struct bridge_softc *);
  static int	bstp_addr_cmp(const uint8_t *, const uint8_t *);
  
  /*
   * When transmitting a config we tack on our path cost to
   * our aggregated path-to-root cost.
   *
   * Note that sc_designated_cost is the lowest root path cost from all
   * incoming links.  When one is talking about two bridges with multiple
   * links between them the root path cost the secondary bridge transmits
   * will be the lowest root path cost it received across those three
   * links and NOT necessarily the root path cost it received specifically
   * on that particular link.  The receiving end must still add its local
   * link cost back in for differentiation purposes.
   */
  static void
  bstp_transmit_config(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (bif->bif_hold_timer.active) {
  		bif->bif_config_pending = 1;
  		return;
  	}
  
  	bif->bif_config_bpdu.cu_message_type = BSTP_MSGTYPE_CFG;
  	bif->bif_config_bpdu.cu_rootid = sc->sc_designated_root;
  	bif->bif_config_bpdu.cu_root_path_cost = sc->sc_designated_cost +
  						 bif->bif_path_cost;
  	bif->bif_config_bpdu.cu_bridge_id = sc->sc_bridge_id;
  	bif->bif_config_bpdu.cu_port_id = bif->bif_port_id;
  
  	if (bstp_root_bridge(sc)) {
  		bif->bif_config_bpdu.cu_message_age = 0;
  	} else if (sc->sc_root_port) {
  		bif->bif_config_bpdu.cu_message_age =
  			sc->sc_root_port->bif_message_age_timer.value +
  			BSTP_MESSAGE_AGE_INCR;
  	} else {
  		bif->bif_config_bpdu.cu_message_age = BSTP_MESSAGE_AGE_INCR;
  	}
  
  	bif->bif_config_bpdu.cu_max_age = sc->sc_max_age;
  	bif->bif_config_bpdu.cu_hello_time = sc->sc_hello_time;
  	bif->bif_config_bpdu.cu_forward_delay = sc->sc_forward_delay;
  	bif->bif_config_bpdu.cu_topology_change_acknowledgment
  	    = bif->bif_topology_change_acknowledge;
  	bif->bif_config_bpdu.cu_topology_change = sc->sc_topology_change;
  
  	if (bif->bif_config_bpdu.cu_message_age < sc->sc_max_age ||
  	    (sc->sc_ifp->if_flags & IFF_LINK1)) {
  		bif->bif_topology_change_acknowledge = 0;
  		bif->bif_config_pending = 0;
  		bstp_send_config_bpdu(sc, bif, &bif->bif_config_bpdu);
  		bstp_timer_start(&bif->bif_hold_timer, 0);
  	}
  }
  
  static void
  bstp_send_config_bpdu(struct bridge_softc *sc, struct bridge_iflist *bif,
  		      struct bstp_config_unit *cu)
  {
  	struct ifnet *ifp;
  	struct mbuf *m;
  	struct ether_header *eh;
  	struct bstp_cbpdu bpdu;
  
  	ifp = bif->bif_ifp;
  
  	if ((ifp->if_flags & IFF_RUNNING) == 0)
  		return;
  
  	MGETHDR(m, M_NOWAIT, MT_DATA);
  	if (m == NULL)
  		return;
  
  	eh = mtod(m, struct ether_header *);
  
  	m->m_pkthdr.rcvif = ifp;
  	m->m_pkthdr.len = sizeof(*eh) + sizeof(bpdu);
  	m->m_len = m->m_pkthdr.len;
  
  	bpdu.cbu_ssap = bpdu.cbu_dsap = LLC_8021D_LSAP;
  	bpdu.cbu_ctl = LLC_UI;
  	bpdu.cbu_protoid = htons(0);
  	bpdu.cbu_protover = 0;
  	bpdu.cbu_bpdutype = cu->cu_message_type;
  	bpdu.cbu_flags = (cu->cu_topology_change ? BSTP_FLAG_TC : 0) |
  	    (cu->cu_topology_change_acknowledgment ? BSTP_FLAG_TCA : 0);
  
  	bpdu.cbu_rootpri = htons(cu->cu_rootid >> 48);
  	bpdu.cbu_rootaddr[0] = cu->cu_rootid >> 40;
  	bpdu.cbu_rootaddr[1] = cu->cu_rootid >> 32;
  	bpdu.cbu_rootaddr[2] = cu->cu_rootid >> 24;
  	bpdu.cbu_rootaddr[3] = cu->cu_rootid >> 16;
  	bpdu.cbu_rootaddr[4] = cu->cu_rootid >> 8;
  	bpdu.cbu_rootaddr[5] = cu->cu_rootid >> 0;
  
  	bpdu.cbu_rootpathcost = htonl(cu->cu_root_path_cost);
  
  	bpdu.cbu_bridgepri = htons(cu->cu_bridge_id >> 48);
  	bpdu.cbu_bridgeaddr[0] = cu->cu_bridge_id >> 40;
  	bpdu.cbu_bridgeaddr[1] = cu->cu_bridge_id >> 32;
  	bpdu.cbu_bridgeaddr[2] = cu->cu_bridge_id >> 24;
  	bpdu.cbu_bridgeaddr[3] = cu->cu_bridge_id >> 16;
  	bpdu.cbu_bridgeaddr[4] = cu->cu_bridge_id >> 8;
  	bpdu.cbu_bridgeaddr[5] = cu->cu_bridge_id >> 0;
  
  	bpdu.cbu_portid = htons(cu->cu_port_id);
  	bpdu.cbu_messageage = htons(cu->cu_message_age);
  	bpdu.cbu_maxage = htons(cu->cu_max_age);
  	bpdu.cbu_hellotime = htons(cu->cu_hello_time);
  	bpdu.cbu_forwarddelay = htons(cu->cu_forward_delay);
  
  	/*
  	 * Packets sent from the bridge always use the bridge MAC
  	 * as the source.
  	 */
  	memcpy(eh->ether_shost, IF_LLADDR(sc->sc_ifp), ETHER_ADDR_LEN);
  	memcpy(eh->ether_dhost, bstp_etheraddr, ETHER_ADDR_LEN);
  	eh->ether_type = htons(sizeof(bpdu));
  
  	memcpy(mtod(m, caddr_t) + sizeof(*eh), &bpdu, sizeof(bpdu));
  
  	bridge_enqueue(ifp, m);
  }
  
  static int
  bstp_root_bridge(struct bridge_softc *sc)
  {
  	return (sc->sc_designated_root == sc->sc_bridge_id);
  }
  
  /*
   * Returns TRUE if the recorded information from our peer has a shorter
   * graph distance than our current best.
   */
  int
  bstp_supersedes_port_info(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (bif->bif_peer_root < sc->sc_designated_root)
  		return (1);
  	if (bif->bif_peer_root > sc->sc_designated_root)
  		return (0);
  
  	/*
  	 * bif_peer_cost and sc_designated_cost do not include the local
  	 * bif_path_cost, otherwise we would not be able to make this
  	 * comparison.
  	 */
  	if (bif->bif_peer_cost < sc->sc_designated_cost)
  		return (1);
  	if (bif->bif_peer_cost > sc->sc_designated_cost)
  		return (0);
  
  	/*
  	 * When the peer costs match we have to check the local path
  	 * cost against the selected root port.  sc_designated_cost
  	 * in an aggregation and cannot be used.
  	 */
  	if (sc->sc_root_port &&
  	    bif->bif_path_cost < sc->sc_root_port->bif_path_cost)
  		return (1);
  	if (sc->sc_root_port &&
  	    bif->bif_path_cost > sc->sc_root_port->bif_path_cost)
  		return (0);
  
  	/*
  	 * If the path costs are identical the bridge with the lowest
  	 * bridge_id wins.
  	 */
  	if (bif->bif_peer_bridge < sc->sc_designated_bridge)
  		return (1);
  	if (bif->bif_peer_bridge > sc->sc_designated_bridge)
  		return (0);
  
  	/*
  	 * bridge_id or bridge+port collision w/peer returns TRUE.
  	 *
  	 * This case can also occur when two bridges are connected
  	 * via multiple links whos path costs have not been set.
  	 */
  	if (bif->bif_peer_bridge != sc->sc_bridge_id)
  		return (1);
  	if (bif->bif_peer_port <= sc->sc_designated_port)
  		return (1);
  	return (0);
  }
  
  /*
   * The shorter graph distance represented by cu (most of which is also
   * already stored in our bif_peer_* fields) becomes the designated info.
   *
   * NOTE: sc_designated_cost does not include bif_path_cost, it is added
   *	 in later on a port-by-port basis as needed.
   */
  static void
  bstp_record_config_information(struct bridge_softc *sc,
  			       struct bridge_iflist *bif,
  			       struct bstp_config_unit *cu)
  {
  	sc->sc_designated_root = bif->bif_peer_root;
  	sc->sc_designated_cost = bif->bif_peer_cost;
  	sc->sc_designated_bridge = bif->bif_peer_bridge;
  	sc->sc_designated_port = bif->bif_peer_port;
  	bstp_timer_start(&bif->bif_message_age_timer, cu->cu_message_age);
  }
  
  static void
  bstp_record_config_timeout_values(struct bridge_softc *sc,
  				  struct bstp_config_unit *config)
  {
  	sc->sc_max_age = config->cu_max_age;
  	sc->sc_hello_time = config->cu_hello_time;
  	sc->sc_forward_delay = config->cu_forward_delay;
  	sc->sc_topology_change = config->cu_topology_change;
  }
  
  static void
  bstp_config_bpdu_generation(struct bridge_softc *sc)
  {
  	struct bridge_iflist *bif, *nbif;
  
  	TAILQ_FOREACH_MUTABLE(bif, &sc->sc_iflists[mycpuid], bif_next, nbif) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_state != BSTP_IFSTATE_DISABLED &&
  		    ((sc->sc_ifp->if_flags & IFF_LINK1) ||
  		     (bif->bif_flags & IFBIF_DESIGNATED))) {
  			bstp_transmit_config(sc, bif);
  		}
  
  		if (nbif != NULL && !nbif->bif_onlist) {
  			KKASSERT(bif->bif_onlist);
  			nbif = TAILQ_NEXT(bif, bif_next);
  		}
  	}
  }
  
  static void
  bstp_transmit_tcn(struct bridge_softc *sc)
  {
  	struct bstp_tbpdu bpdu;
  	struct ifnet *ifp;
  	struct ether_header *eh;
  	struct mbuf *m;
  
  	if (sc->sc_root_port == NULL)	/* all iterfaces disabled */
  		return;
  
  	ifp = sc->sc_root_port->bif_ifp;
  	if ((ifp->if_flags & IFF_RUNNING) == 0)
  		return;
  
  	MGETHDR(m, M_NOWAIT, MT_DATA);
  	if (m == NULL)
  		return;
  
  	m->m_pkthdr.rcvif = ifp;
  	m->m_pkthdr.len = sizeof(*eh) + sizeof(bpdu);
  	m->m_len = m->m_pkthdr.len;
  
  	eh = mtod(m, struct ether_header *);
  
  	/*
  	 * Packets sent from the bridge always use the bridge MAC
  	 * as the source.
  	 */
  	memcpy(eh->ether_shost, IF_LLADDR(sc->sc_ifp), ETHER_ADDR_LEN);
  	memcpy(eh->ether_dhost, bstp_etheraddr, ETHER_ADDR_LEN);
  	eh->ether_type = htons(sizeof(bpdu));
  
  	bpdu.tbu_ssap = bpdu.tbu_dsap = LLC_8021D_LSAP;
  	bpdu.tbu_ctl = LLC_UI;
  	bpdu.tbu_protoid = 0;
  	bpdu.tbu_protover = 0;
  	bpdu.tbu_bpdutype = BSTP_MSGTYPE_TCN;
  
  	memcpy(mtod(m, caddr_t) + sizeof(*eh), &bpdu, sizeof(bpdu));
  
  	bridge_enqueue(ifp, m);
  }
  
  /*
   * Recalculate sc->sc_designated* and sc->sc_root_port (if our bridge
   * is calculated to be the root bridge).  We do this by initializing
   * the designated variables to point at us and then scan our peers.
   * Any uninitialized peers will have a max-value root.
   *
   * Clear IFBIF_DESIGNATED on any ports which no longer match the criteria
   * required to be a designated port.  Only aged out ports and the root
   * port can be designated.
   *
   * If we win we do a second scan to determine which port on our bridge
   * is the best.
   */
  static void
  bstp_configuration_update(struct bridge_softc *sc)
  {
  	uint64_t	designated_root = sc->sc_bridge_id;
  	uint64_t	designated_bridge = sc->sc_bridge_id;
  	uint32_t	designated_cost = 0xFFFFFFFFU;
  	uint32_t	designated_root_cost = 0xFFFFFFFFU;
  	uint16_t	designated_port = 65535;
  	struct bridge_iflist *root_port = NULL;
  	struct bridge_iflist *bif;
  
  	/*
  	 * Resolve information from our peers.  Aged peers will have
  	 * a maxed bif_peer_root and not come under consideration.
  	 */
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_state == BSTP_IFSTATE_DISABLED ||
  		    bif->bif_state == BSTP_IFSTATE_L1BLOCKING) {
  			continue;
  		}
  
  		if (bif->bif_peer_root > designated_root)
  			continue;
  		if (bif->bif_peer_root < designated_root)
  			goto set_port;
  
  		/*
  		 * NOTE: The designated_cost temporary variable already added
  		 *	 in the path code of the related root port.
  		 */
  		if (bif->bif_peer_cost + bif->bif_path_cost > designated_cost)
  			continue;
  		if (bif->bif_peer_cost + bif->bif_path_cost < designated_cost)
  			goto set_port;
  
  		if (bif->bif_peer_bridge > designated_bridge)
  			continue;
  		if (bif->bif_peer_bridge < designated_bridge)
  			goto set_port;
  
  		if (bif->bif_peer_port > designated_port)
  			continue;
  		if (bif->bif_peer_port < designated_port)
  			goto set_port;
  
  		/*
  		 * Same root, path cost, bridge, and port.  Set the root
  		 * only if we do not already have it.
  		 */
  		if (root_port)
  			continue;
  
  		/*
  		 * New root port (from peers)
  		 *
  		 * NOTE: Temporarily add bif_path_cost into the designated
  		 *	 cost to reduce complexity in the loop, it will be
  		 *	 subtracted out when we are done.
  		 */
  set_port:
  		designated_root = bif->bif_peer_root;
  		designated_cost = bif->bif_peer_cost + bif->bif_path_cost;
  		designated_root_cost = bif->bif_peer_cost;
  		designated_bridge = bif->bif_peer_bridge;
  		designated_port = bif->bif_peer_port;
  		root_port = bif;
  	}
  
  	/*
  	 * root_port will be NULL at the start here if all of our
  	 * peers are aged or are not as good a root as our bridge would
  	 * be.  It can also be NULL due to all related links being
  	 * disabled.
  	 *
  	 * If the root winds up being our bridge scan again against local
  	 * information.  Unconditionally update IFBIF_DESIGNATED.
  	 */
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		bif->bif_flags &= ~(IFBIF_DESIGNATED | IFBIF_ROOT);
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_state == BSTP_IFSTATE_DISABLED ||
  		    bif->bif_state == BSTP_IFSTATE_L1BLOCKING) {
  			continue;
  		}
  
  		/*
  		 * Set DESIGNATED for an aged or unknown peer.
  		 */
  		if (bif->bif_peer_bridge == 0xFFFFFFFFFFFFFFFFLLU)
  			bif->bif_flags |= IFBIF_DESIGNATED;
  		if (designated_root != sc->sc_bridge_id)
  			continue;
  
  		/*
  		 * This is only reached if our bridge is the root bridge,
  		 * select the root port (IFBIF_DESIGNATED is set at the
  		 * end).
  		 *
  		 * The peer cost will incorporate the peer bridge's best
  		 * cost to the root bridge (us), which is NOT necessarily
  		 * our path cost, plus the peer bridge's own path cost.
  		 * Because of this we must still add in our path cost for
  		 * further differentiation.  Because the peer's 'best' cost
  		 * is applied to all of its outgoing messages we should
  		 * still come to the same conclusion as the peer.
  		 */
  		if (bif->bif_peer_cost + bif->bif_path_cost > designated_cost)
  			continue;
  		if (bif->bif_peer_cost + bif->bif_path_cost < designated_cost)
  			goto set_port2;
  
  		if (bif->bif_port_id > designated_port)
  			continue;
  		if (bif->bif_port_id < designated_port)
  			goto set_port2;
  		/* degenerate case (possible peer collision w/our key */
  
  		/*
  		 * New port.  Since we are the root, the root cost is always
  		 * 0.  The peer's cu_root_path_cost does not necessarily
  		 * incorporate our peer path cost, but instead incorporates
  		 * the lowest path cost to root for the target bridge
  		 * when multiple links are present between the two bridges.
  		 * Thus for selection purposes we must still add in our
  		 * local path cost.
  		 */
  set_port2:
  		designated_cost = bif->bif_peer_cost + bif->bif_path_cost;
  		designated_root_cost = 0;
  		designated_bridge = sc->sc_bridge_id;
  		designated_port = bif->bif_port_id;
  		root_port = bif;
  	}
  
  	/*
  	 * Update aggregate information.  The selected root port always
  	 * becomes a designated port (along with aged ports).  This can
  	 * either be the port whos peer is closest to the root or it
  	 * can be one of our ports if our bridge is the root.
  	 *
  	 * The root cost we record in sc_designated_root does not include
  	 * bif_path_cost of the root port, since we may transmit this
  	 * out of any port we will add the cost back in later on on
  	 * a per-port basis.
  	 *
  	 * root_port can be NULL here (if all links are disabled)
  	 */
  	if (root_port) {
  		sc->sc_designated_root = designated_root;
  		sc->sc_designated_cost = designated_root_cost;
  		sc->sc_designated_bridge = designated_bridge;
  		sc->sc_designated_port = designated_port;
  		root_port->bif_flags |= IFBIF_DESIGNATED | IFBIF_ROOT;
  	} else {
  		sc->sc_designated_root = designated_root;
  		sc->sc_designated_cost = designated_cost;
  		sc->sc_designated_bridge = designated_bridge;
  		sc->sc_designated_port = designated_port;
  	}
  	sc->sc_root_port = root_port;
  }
  
  /*
   * Calculate the desired state for each interface link on our bridge.
   *
   * The best port will match against sc->sc_root_port (whether we are root
   * or whether that port is the closest to the root).  We push this port
   * towards a FORWARDING state.
   *
   * Next come designated ports, either aged ports or ports with no peer info
   * (yet), or the peer who is closest to the root. We push this port towards
   * a FORWARDING state as well.
   *
   * Any remaining ports are pushed towards a BLOCKING state.  Both sides of
   * the port (us and our peer) should wind up placing the two ends in this
   * state or bad things happen.
   */
  static void
  bstp_port_state_selection(struct bridge_softc *sc)
  {
  	struct bridge_iflist *bif, *nbif;
  
  	TAILQ_FOREACH_MUTABLE(bif, &sc->sc_iflists[mycpuid], bif_next, nbif) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (sc->sc_root_port &&
  		    bif->bif_info == sc->sc_root_port->bif_info) {
  			bif->bif_config_pending = 0;
  			bif->bif_topology_change_acknowledge = 0;
  			bstp_make_forwarding(sc, bif);
  		} else if (bif->bif_flags & IFBIF_DESIGNATED) {
  			bstp_timer_stop(&bif->bif_message_age_timer);
  			bstp_make_forwarding(sc, bif);
  		} else {
  			bif->bif_config_pending = 0;
  			bif->bif_topology_change_acknowledge = 0;
  			bstp_make_blocking(sc, bif);
  		}
  
  		if (nbif != NULL && !nbif->bif_onlist) {
  			KKASSERT(bif->bif_onlist);
  			nbif = TAILQ_NEXT(bif, bif_next);
  		}
  	}
  }
  
  /*
   * Clear peer info, effectively makes the port looked aged out.
   * It becomes a designated go-to port.
   */
  static void
  bstp_clear_peer_info(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	bif->bif_peer_root = 0xFFFFFFFFFFFFFFFFLLU;
  	bif->bif_peer_cost = 0xFFFFFFFFU;
  	bif->bif_peer_bridge = 0xFFFFFFFFFFFFFFFFLLU;
  	bif->bif_peer_port = 0xFFFFU;
  
  	if (bif->bif_state != BSTP_IFSTATE_DISABLED &&
  	    bif->bif_state != BSTP_IFSTATE_L1BLOCKING) {
  		bif->bif_flags |= IFBIF_DESIGNATED;
  	}
  }
  
  static void
  bstp_make_forwarding(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (bif->bif_state == BSTP_IFSTATE_BLOCKING ||
  	    bif->bif_state == BSTP_IFSTATE_BONDED) {
  		bstp_set_port_state(bif, BSTP_IFSTATE_LISTENING);
  		bstp_timer_start(&bif->bif_forward_delay_timer, 0);
  	}
  }
  
  static void
  bstp_make_blocking(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (bif->bif_state != BSTP_IFSTATE_DISABLED &&
  	    bif->bif_state != BSTP_IFSTATE_BLOCKING &&
  	    bif->bif_state != BSTP_IFSTATE_BONDED &&
  	    bif->bif_state != BSTP_IFSTATE_L1BLOCKING) {
  		if ((bif->bif_state == BSTP_IFSTATE_FORWARDING) ||
  		    (bif->bif_state == BSTP_IFSTATE_LEARNING)) {
  			if (bif->bif_change_detection_enabled) {
  				bstp_topology_change_detection(sc);
  			}
  		}
  		bstp_set_port_state(bif, BSTP_IFSTATE_BLOCKING);
  		bridge_rtdelete(sc, bif->bif_ifp, IFBF_FLUSHDYN);
  		bstp_timer_stop(&bif->bif_forward_delay_timer);
  		if (sc->sc_ifp->if_flags & IFF_LINK2)
  			bstp_adjust_bonded_states(sc, bif);
  	}
  }
  
  static void
  bstp_make_l1blocking(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	int was_forwarding = (bif->bif_state == BSTP_IFSTATE_FORWARDING);
  
  	switch(bif->bif_state) {
  	case BSTP_IFSTATE_LISTENING:
  	case BSTP_IFSTATE_LEARNING:
  	case BSTP_IFSTATE_FORWARDING:
  	case BSTP_IFSTATE_BLOCKING:
  	case BSTP_IFSTATE_BONDED:
  		bstp_set_port_state(bif, BSTP_IFSTATE_L1BLOCKING);
  		bridge_rtdelete(sc, bif->bif_ifp, IFBF_FLUSHDYN);
  		bstp_timer_stop(&bif->bif_forward_delay_timer);
  		bstp_timer_stop(&bif->bif_link1_timer);
  		if (bif->bif_flags & IFBIF_DESIGNATED) {
  			bif->bif_flags &= ~IFBIF_DESIGNATED;
  			bstp_configuration_update(sc);
  			bstp_port_state_selection(sc);
  		}
  		if (was_forwarding && (sc->sc_ifp->if_flags & IFF_LINK2))
  			bstp_adjust_bonded_states(sc, bif);
  		break;
  	default:
  		break;
  	}
  }
  
  /*
   * Member (bif) changes to or from a FORWARDING state.  All members in the
   * same bonding group which are in a BLOCKING or BONDED state must be set
   * to either BLOCKING or BONDED based on whether any members in the bonding
   * group remain in the FORWARDING state.
   *
   * Going between the BLOCKING and BONDED states does not require a
   * configuration update.
   */
  static void
  bstp_adjust_bonded_states(struct bridge_softc *sc, struct bridge_iflist *obif)
  {
  	struct bridge_iflist *bif;
  	int state = BSTP_IFSTATE_BLOCKING;
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_state != BSTP_IFSTATE_FORWARDING)
  			continue;
  		if (memcmp(IF_LLADDR(bif->bif_ifp), IF_LLADDR(obif->bif_ifp),
  			   ETHER_ADDR_LEN) != 0) {
  			continue;
  		}
  		state = BSTP_IFSTATE_BONDED;
  		break;
  	}
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_state != BSTP_IFSTATE_BLOCKING &&
  		    bif->bif_state != BSTP_IFSTATE_BONDED) {
  			continue;
  		}
  		if (memcmp(IF_LLADDR(bif->bif_ifp), IF_LLADDR(obif->bif_ifp),
  			   ETHER_ADDR_LEN) != 0) {
  			continue;
  		}
  		if (bif->bif_bond_weight == 0)
  			bif->bif_state = BSTP_IFSTATE_BLOCKING;
  		else
  			bif->bif_state = state;
  	}
  }
  
  static void
  bstp_set_port_state(struct bridge_iflist *bif, uint8_t state)
  {
  	bif->bif_state = state;
  }
  
  static void
  bstp_topology_change_detection(struct bridge_softc *sc)
  {
  	if (bstp_root_bridge(sc)) {
  		sc->sc_topology_change = 1;
  		bstp_timer_start(&sc->sc_topology_change_timer, 0);
  	} else if (!sc->sc_topology_change_detected) {
  		bstp_transmit_tcn(sc);
  		bstp_timer_start(&sc->sc_tcn_timer, 0);
  	}
  	sc->sc_topology_change_detected = 1;
  }
  
  static void
  bstp_topology_change_acknowledged(struct bridge_softc *sc)
  {
  	sc->sc_topology_change_detected = 0;
  	bstp_timer_stop(&sc->sc_tcn_timer);
  }
  
  static void
  bstp_acknowledge_topology_change(struct bridge_softc *sc,
  				 struct bridge_iflist *bif)
  {
  	bif->bif_topology_change_acknowledge = 1;
  	bstp_transmit_config(sc, bif);
  }
  
  void
  bstp_input(struct bridge_softc *sc, struct bridge_iflist *bif, struct mbuf *m)
  {
  	struct ether_header *eh;
  	struct bstp_tbpdu tpdu;
  	struct bstp_cbpdu cpdu;
  	struct bstp_config_unit cu;
  	struct bstp_tcn_unit tu;
  	uint16_t len;
  
  	if ((bif->bif_flags & IFBIF_STP) == 0)
  		goto out;
  
  	/*
  	 * The L1BLOCKING (ping pong failover) test needs to reset the
  	 * timer if LINK1 is active.
  	 */
  	if (bif->bif_state == BSTP_IFSTATE_L1BLOCKING) {
  		bstp_set_port_state(bif, BSTP_IFSTATE_BLOCKING);
  		if (sc->sc_ifp->if_flags & IFF_LINK1)
  			bstp_timer_start(&bif->bif_link1_timer, 0);
  		bstp_make_forwarding(sc, bif);
  	} else if (sc->sc_ifp->if_flags & IFF_LINK1) {
  		bstp_timer_start(&bif->bif_link1_timer, 0);
  	}
  
  	eh = mtod(m, struct ether_header *);
  
  	len = ntohs(eh->ether_type);
  	if (len < sizeof(tpdu))
  		goto out;
  
  	m_adj(m, ETHER_HDR_LEN);
  
  	if (m->m_pkthdr.len > len)
  		m_adj(m, len - m->m_pkthdr.len);
  	if (m->m_len < sizeof(tpdu) &&
  	    (m = m_pullup(m, sizeof(tpdu))) == NULL)
  		goto out;
  
  	memcpy(&tpdu, mtod(m, caddr_t), sizeof(tpdu));
  
  	if (tpdu.tbu_dsap != LLC_8021D_LSAP ||
  	    tpdu.tbu_ssap != LLC_8021D_LSAP ||
  	    tpdu.tbu_ctl != LLC_UI)
  		goto out;
  	if (tpdu.tbu_protoid != 0 || tpdu.tbu_protover != 0)
  		goto out;
  
  	switch (tpdu.tbu_bpdutype) {
  	case BSTP_MSGTYPE_TCN:
  		tu.tu_message_type = tpdu.tbu_bpdutype;
  		bstp_received_tcn_bpdu(sc, bif, &tu);
  		break;
  	case BSTP_MSGTYPE_CFG:
  		if (m->m_len < sizeof(cpdu) &&
  		    (m = m_pullup(m, sizeof(cpdu))) == NULL)
  			goto out;
  		memcpy(&cpdu, mtod(m, caddr_t), sizeof(cpdu));
  
  		cu.cu_rootid =
  		    (((uint64_t)ntohs(cpdu.cbu_rootpri)) << 48) |
  		    (((uint64_t)cpdu.cbu_rootaddr[0]) << 40) |
  		    (((uint64_t)cpdu.cbu_rootaddr[1]) << 32) |
  		    (((uint64_t)cpdu.cbu_rootaddr[2]) << 24) |
  		    (((uint64_t)cpdu.cbu_rootaddr[3]) << 16) |
  		    (((uint64_t)cpdu.cbu_rootaddr[4]) << 8) |
  		    (((uint64_t)cpdu.cbu_rootaddr[5]) << 0);
  
  		cu.cu_bridge_id =
  		    (((uint64_t)ntohs(cpdu.cbu_bridgepri)) << 48) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[0]) << 40) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[1]) << 32) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[2]) << 24) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[3]) << 16) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[4]) << 8) |
  		    (((uint64_t)cpdu.cbu_bridgeaddr[5]) << 0);
  
  		cu.cu_root_path_cost = ntohl(cpdu.cbu_rootpathcost);
  		cu.cu_message_age = ntohs(cpdu.cbu_messageage);
  		cu.cu_max_age = ntohs(cpdu.cbu_maxage);
  		cu.cu_hello_time = ntohs(cpdu.cbu_hellotime);
  		cu.cu_forward_delay = ntohs(cpdu.cbu_forwarddelay);
  		cu.cu_port_id = ntohs(cpdu.cbu_portid);
  		cu.cu_message_type = cpdu.cbu_bpdutype;
  		cu.cu_topology_change_acknowledgment =
  		    (cpdu.cbu_flags & BSTP_FLAG_TCA) ? 1 : 0;
  		cu.cu_topology_change =
  		    (cpdu.cbu_flags & BSTP_FLAG_TC) ? 1 : 0;
  		bstp_received_config_bpdu(sc, bif, &cu);
  		break;
  	default:
  		goto out;
  	}
  out:
  	if (m)
  		m_freem(m);
  }
  
  static void
  bstp_received_config_bpdu(struct bridge_softc *sc, struct bridge_iflist *bif,
  			  struct bstp_config_unit *cu)
  {
  	int iamroot;
  
  	iamroot = bstp_root_bridge(sc);
  
  	if (bif->bif_state != BSTP_IFSTATE_DISABLED) {
  		/*
  		 * Record information from peer.  The peer_cost field
  		 * does not include the local bif->bif_path_cost, it will
  		 * be added in as needed (since it can be modified manually
  		 * this way we don't have to worry about fixups).
  		 */
  		bif->bif_peer_root = cu->cu_rootid;
  		bif->bif_peer_cost = cu->cu_root_path_cost;
  		bif->bif_peer_bridge = cu->cu_bridge_id;
  		bif->bif_peer_port = cu->cu_port_id;
  
  		if (bstp_supersedes_port_info(sc, bif)) {
  			bstp_record_config_information(sc, bif, cu);
  			bstp_configuration_update(sc);
  			bstp_port_state_selection(sc);
  
  			/*
  			 * If our bridge loses its root status (?)
  			 *
  			 * Hello's (unsolicited CFG packets) are generated
  			 * every hello period of LINK1 is set, otherwise
  			 * we are no longer the root bridge and must stop
  			 * generating unsolicited CFG packets.
  			 */
  			if (iamroot && bstp_root_bridge(sc) == 0) {
  				if ((sc->sc_ifp->if_flags & IFF_LINK1) == 0)
  					bstp_timer_stop(&sc->sc_hello_timer);
  
  				if (sc->sc_topology_change_detected) {
  					bstp_timer_stop(
  					    &sc->sc_topology_change_timer);
  					bstp_transmit_tcn(sc);
  					bstp_timer_start(&sc->sc_tcn_timer, 0);
  				}
  			}
  
  			if (sc->sc_root_port &&
  			    bif->bif_info == sc->sc_root_port->bif_info) {
  				bstp_record_config_timeout_values(sc, cu);
  				bstp_config_bpdu_generation(sc);
  
  				if (cu->cu_topology_change_acknowledgment)
  					bstp_topology_change_acknowledged(sc);
  			}
  		} else if (bif->bif_flags & IFBIF_DESIGNATED) {
  			/*
  			 * Update designated ports (aged out peers or
  			 * the port closest to the root) at a faster pace.
  			 *
  			 * Clear our designated flag if we aren't marked
  			 * as the root port.
  			 */
  			bstp_transmit_config(sc, bif);
  			if ((bif->bif_flags & IFBIF_ROOT) == 0) {
  				bif->bif_flags &= ~IFBIF_DESIGNATED;
  				bstp_configuration_update(sc);
  				bstp_port_state_selection(sc);
  			}
  		}
  	}
  }
  
  static void
  bstp_received_tcn_bpdu(struct bridge_softc *sc, struct bridge_iflist *bif,
  		       struct bstp_tcn_unit *tcn)
  {
  	if (bif->bif_state != BSTP_IFSTATE_DISABLED &&
  	    (bif->bif_flags & IFBIF_DESIGNATED)) {
  		bstp_topology_change_detection(sc);
  		bstp_acknowledge_topology_change(sc, bif);
  	}
  }
  
  /*
   * link1 forces continuous hello's (the bridge interface must be cycled
   * to start them up), so keep the timer hot if that is the case, otherwise
   * only send HELLO's if we are the root.
   */
  static void
  bstp_hello_timer_expiry(struct bridge_softc *sc)
  {
  	bstp_config_bpdu_generation(sc);
  
  	if ((sc->sc_ifp->if_flags & IFF_LINK1) || bstp_root_bridge(sc))
  		bstp_timer_start(&sc->sc_hello_timer, 0);
  }
  
  static void
  bstp_message_age_timer_expiry(struct bridge_softc *sc,
  			      struct bridge_iflist *bif)
  {
  	int iamroot;
  
  	iamroot = bstp_root_bridge(sc);
  	bstp_clear_peer_info(sc, bif);
  	bstp_configuration_update(sc);
  	bstp_port_state_selection(sc);
  
  	/*
  	 * If we've become the root and were not the root before
  	 * we have some cleanup to do.  This also occurs if we
  	 * wind up being completely isolated.
  	 */
  	if (iamroot == 0 && bstp_root_bridge(sc)) {
  		sc->sc_max_age = sc->sc_bridge_max_age;
  		sc->sc_hello_time = sc->sc_bridge_hello_time;
  		sc->sc_forward_delay = sc->sc_bridge_forward_delay;
  
  		bstp_topology_change_detection(sc);
  		bstp_timer_stop(&sc->sc_tcn_timer);
  		bstp_config_bpdu_generation(sc);
  		bstp_timer_start(&sc->sc_hello_timer, 0);
  	}
  }
  
  static void
  bstp_forward_delay_timer_expiry(struct bridge_softc *sc,
  				struct bridge_iflist *bif)
  {
  	if (bif->bif_state == BSTP_IFSTATE_LISTENING) {
  		bstp_set_port_state(bif, BSTP_IFSTATE_LEARNING);
  		bstp_timer_start(&bif->bif_forward_delay_timer, 0);
  	} else if (bif->bif_state == BSTP_IFSTATE_LEARNING) {
  		bstp_set_port_state(bif, BSTP_IFSTATE_FORWARDING);
  		if (sc->sc_designated_bridge == sc->sc_bridge_id &&
  		    bif->bif_change_detection_enabled) {
  			bstp_topology_change_detection(sc);
  		}
  		bstp_configuration_update(sc);
  		bstp_port_state_selection(sc);
  		if (sc->sc_ifp->if_flags & IFF_LINK2)
  			bstp_adjust_bonded_states(sc, bif);
  	}
  }
  
  static void
  bstp_tcn_timer_expiry(struct bridge_softc *sc)
  {
  	bstp_transmit_tcn(sc);
  	bstp_timer_start(&sc->sc_tcn_timer, 0);
  }
  
  static void
  bstp_topology_change_timer_expiry(struct bridge_softc *sc)
  {
  	sc->sc_topology_change_detected = 0;
  	sc->sc_topology_change = 0;
  }
  
  static void
  bstp_hold_timer_expiry(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (bif->bif_config_pending)
  		bstp_transmit_config(sc, bif);
  }
  
  /*
   * If no traffic received directly on this port for the specified
   * period with link1 set we go into a special blocking mode to
   * fail-over traffic to another port.
   */
  static void
  bstp_link1_timer_expiry(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	if (sc->sc_ifp->if_flags & IFF_LINK1)
  		bstp_make_l1blocking(sc, bif);
  }
  
  static int
  bstp_addr_cmp(const uint8_t *a, const uint8_t *b)
  {
  	int i, d;
  
  	for (i = 0, d = 0; i < ETHER_ADDR_LEN && d == 0; i++) {
  		d = ((int)a[i]) - ((int)b[i]);
  	}
  
  	return (d);
  }
  
  void
  bstp_initialization(struct bridge_softc *sc)
  {
  	struct bridge_iflist *bif, *mif, *nbif;
  	u_char *e_addr;
  
  	KKASSERT(&curthread->td_msgport == BRIDGE_CFGPORT);
  
  	/*
  	 * Figure out our bridge ID, use the lowest-valued MAC.
  	 * Include the bridge's own random MAC in the calculation.
  	 */
  	mif = NULL;
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bif->bif_ifp->if_type != IFT_ETHER)
  			continue;
  		if (mif == NULL) {
  			mif = bif;
  			continue;
  		}
  
  		bif->bif_port_id = (bif->bif_priority << 8) |
  				   (bif->bif_ifp->if_index & 0xff);
  		if (bstp_addr_cmp(IF_LLADDR(bif->bif_ifp),
  				  IF_LLADDR(mif->bif_ifp)) < 0) {
  			mif = bif;
  			continue;
  		}
  	}
  	if (mif == NULL) {
  		bstp_stop(sc);
  		return;
  	}
  
  	if (bstp_addr_cmp(IF_LLADDR(sc->sc_ifp), IF_LLADDR(mif->bif_ifp)) < 0)
  		e_addr = IF_LLADDR(sc->sc_ifp);
  	else
  		e_addr = IF_LLADDR(mif->bif_ifp);
  
  	sc->sc_bridge_id =
  	    (((uint64_t)sc->sc_bridge_priority) << 48) |
  	    (((uint64_t)e_addr[0]) << 40) |
  	    (((uint64_t)e_addr[1]) << 32) |
  	    (((uint64_t)e_addr[2]) << 24) |
  	    (((uint64_t)e_addr[3]) << 16) |
  	    (((uint64_t)e_addr[4]) << 8) |
  	    (((uint64_t)e_addr[5]));
  
  	/*
  	 * Remainder of setup.
  	 */
  
  	sc->sc_designated_root = sc->sc_bridge_id;
  	sc->sc_designated_cost = 0;
  	sc->sc_root_port = NULL;
  
  	sc->sc_max_age = sc->sc_bridge_max_age;
  	sc->sc_hello_time = sc->sc_bridge_hello_time;
  	sc->sc_forward_delay = sc->sc_bridge_forward_delay;
  	sc->sc_topology_change_detected = 0;
  	sc->sc_topology_change = 0;
  	bstp_timer_stop(&sc->sc_tcn_timer);
  	bstp_timer_stop(&sc->sc_topology_change_timer);
  
  	if (callout_pending(&sc->sc_bstpcallout) == 0)
  		callout_reset(&sc->sc_bstpcallout, hz,
  		    bstp_tick, sc);
  
  	TAILQ_FOREACH_MUTABLE(bif, &sc->sc_iflists[mycpuid], bif_next, nbif) {
  		if (sc->sc_ifp->if_flags & IFF_LINK1)
  			bstp_timer_start(&bif->bif_link1_timer, 0);
  		if (bif->bif_flags & IFBIF_STP)
  			bstp_ifupdstatus(sc, bif);
  		else
  			bstp_disable_port(sc, bif);
  
  		if (nbif != NULL && !nbif->bif_onlist) {
  			KKASSERT(bif->bif_onlist);
  			nbif = TAILQ_NEXT(bif, bif_next);
  		}
  	}
  
  	bstp_port_state_selection(sc);
  	bstp_config_bpdu_generation(sc);
  	bstp_timer_start(&sc->sc_hello_timer, 0);
  }
  
  void
  bstp_stop(struct bridge_softc *sc)
  {
  	struct bridge_iflist *bif;
  
  	KKASSERT(&curthread->td_msgport == BRIDGE_CFGPORT);
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		bstp_set_port_state(bif, BSTP_IFSTATE_DISABLED);
  		bstp_timer_stop(&bif->bif_hold_timer);
  		bstp_timer_stop(&bif->bif_message_age_timer);
  		bstp_timer_stop(&bif->bif_forward_delay_timer);
  		bstp_timer_stop(&bif->bif_link1_timer);
  	}
  
  	callout_stop(&sc->sc_bstpcallout);
  
  	bstp_timer_stop(&sc->sc_topology_change_timer);
  	bstp_timer_stop(&sc->sc_tcn_timer);
  	bstp_timer_stop(&sc->sc_hello_timer);
  
  	crit_enter();
  	lwkt_dropmsg(&sc->sc_bstptimemsg.lmsg);
  	crit_exit();
  }
  
  /*
   * [re]initialize a port.  The port is initialized to a L1BLOCKING state
   * or a BLOCKING state.  When link ping/pong is enabled (LINK1) we start
   * out in the L1BLOCKING state to prevent flapping from blowing up the
   * state of the other ports.
   *
   * Either way the first config packet received will knock the port into
   * the LISTENING state.
   */
  static void
  bstp_initialize_port(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	int needs_adjust = (bif->bif_state == BSTP_IFSTATE_FORWARDING ||
  			    bif->bif_state == BSTP_IFSTATE_BLOCKING ||
  			    bif->bif_state == BSTP_IFSTATE_BONDED);
  
  	if (sc->sc_ifp->if_flags & IFF_LINK1)
  		bstp_set_port_state(bif, BSTP_IFSTATE_L1BLOCKING);
  	else
  		bstp_set_port_state(bif, BSTP_IFSTATE_BLOCKING);
  	bstp_clear_peer_info(sc, bif);
  	bif->bif_topology_change_acknowledge = 0;
  	bif->bif_config_pending = 0;
  	bif->bif_change_detection_enabled = 1;
  	bstp_timer_stop(&bif->bif_message_age_timer);
  	bstp_timer_stop(&bif->bif_forward_delay_timer);
  	bstp_timer_stop(&bif->bif_hold_timer);
  	bstp_timer_stop(&bif->bif_link1_timer);
  	if (needs_adjust && (sc->sc_ifp->if_flags & IFF_LINK2))
  		bstp_adjust_bonded_states(sc, bif);
  }
  
  /*
   * When enabling a port that was previously disabled no configuration
   * update occurs, otherwise down/up or running/not-running flapping
   * (e.g. by openvpn on a TAP interface) will blow up the other ports.
   */
  static void
  bstp_enable_port(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	int was_disabled = (bif->bif_state == BSTP_IFSTATE_DISABLED ||
  			    bif->bif_state == BSTP_IFSTATE_L1BLOCKING);
  
  	bstp_initialize_port(sc, bif);
  	if (sc->sc_ifp->if_flags & IFF_LINK1)
  		bstp_timer_start(&bif->bif_link1_timer, 0);
  	if (was_disabled == 0) {
  		bstp_configuration_update(sc);
  		bstp_port_state_selection(sc);
  	}
  	bstp_adjust_bonded_states(sc, bif);
  }
  
  /*
   * When disabling a port that was previously in a non-forwarding or bonded
   * state no configuration update occurs, otherwise down/up or
   * running/not-running flapping (e.g. by openvpn on a TAP interface) will
   * blow up the other ports.
   */
  static void
  bstp_disable_port(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	int was_forwarding = (bif->bif_state == BSTP_IFSTATE_FORWARDING);
  	int was_bonded = (bif->bif_state == BSTP_IFSTATE_BONDED);
  	int iamroot;
  
  	iamroot = bstp_root_bridge(sc);
  
  	bstp_clear_peer_info(sc, bif);
  	bstp_set_port_state(bif, BSTP_IFSTATE_DISABLED);
  	bif->bif_topology_change_acknowledge = 0;
  	bif->bif_config_pending = 0;
  	bstp_timer_stop(&bif->bif_message_age_timer);
  	bstp_timer_stop(&bif->bif_forward_delay_timer);
  	bstp_timer_stop(&bif->bif_link1_timer);
  	if (was_forwarding || was_bonded) {
  		bstp_configuration_update(sc);
  		bstp_port_state_selection(sc);
  	}
  	bridge_rtdelete(sc, bif->bif_ifp, IFBF_FLUSHDYN);
  	if (was_forwarding && (sc->sc_ifp->if_flags & IFF_LINK2))
  		bstp_adjust_bonded_states(sc, bif);
  
  	if (iamroot == 0 && bstp_root_bridge(sc)) {
  		sc->sc_max_age = sc->sc_bridge_max_age;
  		sc->sc_hello_time = sc->sc_bridge_hello_time;
  		sc->sc_forward_delay = sc->sc_bridge_forward_delay;
  
  		bstp_topology_change_detection(sc);
  		bstp_timer_stop(&sc->sc_tcn_timer);
  		bstp_config_bpdu_generation(sc);
  		bstp_timer_start(&sc->sc_hello_timer, 0);
  	}
  }
  
  void
  bstp_linkstate(struct ifnet *ifp, int state)
  {
  	struct bridge_softc *sc;
  	struct bridge_iflist *bif;
  
  	sc = ifp->if_bridge;
  	ifnet_serialize_all(sc->sc_ifp);
  
  	/*
  	 * bstp_ifupdstatus() may block, but it is the last
  	 * operation of the member iface iteration, so we
  	 * don't need to use LIST_FOREACH_MUTABLE()+bif_onlist
  	 * check here.
  	 */
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  
  		if (bif->bif_ifp == ifp) {
  			bstp_ifupdstatus(sc, bif);
  			break;
  		}
  	}
  	ifnet_deserialize_all(sc->sc_ifp);
  }
  
  static void
  bstp_ifupdstatus(struct bridge_softc *sc, struct bridge_iflist *bif)
  {
  	struct ifnet *ifp = bif->bif_ifp;
  	struct ifmediareq ifmr;
  	int error = 0;
  
  	bzero((char *)&ifmr, sizeof(ifmr));
  	ifnet_serialize_all(ifp);
  	error = (*ifp->if_ioctl)(ifp, SIOCGIFMEDIA, (caddr_t)&ifmr, NULL);
  	ifnet_deserialize_all(ifp);
  
  	if ((error == 0) && (ifp->if_flags & IFF_UP)) {
  	 	if (ifmr.ifm_status & IFM_ACTIVE) {
  			if (bif->bif_state == BSTP_IFSTATE_DISABLED)
  				bstp_enable_port(sc, bif);
  
  		} else {
  			if (bif->bif_state != BSTP_IFSTATE_DISABLED)
  				bstp_disable_port(sc, bif);
  		}
  		return;
  	}
  
  	if (bif->bif_state != BSTP_IFSTATE_DISABLED)
  		bstp_disable_port(sc, bif);
  }
  
  static void
  bstp_tick(void *arg)
  {
  	struct bridge_softc *sc = arg;
  	struct lwkt_msg *lmsg;
  
  	KKASSERT(mycpuid == BRIDGE_CFGCPU);
  
  	crit_enter();
  
  	if (callout_pending(&sc->sc_bstpcallout) ||
  	    !callout_active(&sc->sc_bstpcallout)) {
  		crit_exit();
  		return;
  	}
  	callout_deactivate(&sc->sc_bstpcallout);
  
  	lmsg = &sc->sc_bstptimemsg.lmsg;
  	KKASSERT(lmsg->ms_flags & MSGF_DONE);
  	lwkt_sendmsg_oncpu(BRIDGE_CFGPORT, lmsg);
  
  	crit_exit();
  }
  
  void
  bstp_tick_handler(netmsg_t msg)
  {
  	struct bridge_softc *sc = msg->lmsg.u.ms_resultp;
  	struct bridge_iflist *bif;
  
  	KKASSERT(&curthread->td_msgport == BRIDGE_CFGPORT);
  	crit_enter();
  	/* Reply ASAP */
  	lwkt_replymsg(&msg->lmsg, 0);
  	crit_exit();
  
  	ifnet_serialize_all(sc->sc_ifp);
  
  	/*
  	 * NOTE:
  	 * We don't need to worry that member iface is ripped
  	 * from the per-cpu list during the blocking operation
  	 * in the loop body, since deletion is serialized by
  	 * BRIDGE_CFGPORT
  	 */
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		/*
  		 * XXX This can cause a lag in "link does away"
  		 * XXX and "spanning tree gets updated".  We need
  		 * XXX come sort of callback from the link state
  		 * XXX update code to kick spanning tree.
  		 * XXX --thorpej@NetBSD.org
  		 */
  		bstp_ifupdstatus(sc, bif);
  	}
  
  	if (bstp_timer_expired(&sc->sc_hello_timer, sc->sc_hello_time))
  		bstp_hello_timer_expiry(sc);
  
  	if (bstp_timer_expired(&sc->sc_tcn_timer, sc->sc_bridge_hello_time))
  		bstp_tcn_timer_expiry(sc);
  
  	if (bstp_timer_expired(&sc->sc_topology_change_timer,
  	    sc->sc_topology_change_time))
  		bstp_topology_change_timer_expiry(sc);
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bstp_timer_expired(&bif->bif_message_age_timer,
  		    sc->sc_max_age))
  			bstp_message_age_timer_expiry(sc, bif);
  	}
  
  	TAILQ_FOREACH(bif, &sc->sc_iflists[mycpuid], bif_next) {
  		if ((bif->bif_flags & IFBIF_STP) == 0)
  			continue;
  		if (bstp_timer_expired(&bif->bif_forward_delay_timer,
  		    sc->sc_forward_delay))
  			bstp_forward_delay_timer_expiry(sc, bif);
  
  		if (bstp_timer_expired(&bif->bif_hold_timer,
  		    sc->sc_hold_time))
  			bstp_hold_timer_expiry(sc, bif);
  
  		if (bstp_timer_expired(&bif->bif_link1_timer,
  		    sc->sc_hello_time * 10))
  			bstp_link1_timer_expiry(sc, bif);
  	}
  
  	if (sc->sc_ifp->if_flags & IFF_RUNNING)
  		callout_reset(&sc->sc_bstpcallout, hz, bstp_tick, sc);
  
  	ifnet_deserialize_all(sc->sc_ifp);
  }
  
  static void
  bstp_timer_start(struct bridge_timer *t, uint16_t v)
  {
  	t->value = v;
  	t->active = 1;
  }
  
  static void
  bstp_timer_stop(struct bridge_timer *t)
  {
  	t->value = 0;
  	t->active = 0;
  }
  
  static int
  bstp_timer_expired(struct bridge_timer *t, uint16_t v)
  {
  	if (t->active == 0)
  		return (0);
  	t->value += BSTP_TICK_VAL;
  	if (t->value >= v) {
  		bstp_timer_stop(t);
  		return (1);
  	}
  	return (0);
  
  }
  