text: /*-
   * Copyright (c) 2002-2009 Sam Leffler, Errno Consulting
   * 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.
   *
   * 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.
   *
   * $FreeBSD: head/sys/net80211/ieee80211_scan_sta.c 196005 2009-07-31 19:13:16Z sam $
   */
  
  /*
   * IEEE 802.11 station scanning support.
   */
  #include "opt_wlan.h"
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/kernel.h>
  #include <sys/module.h>
  #include <sys/lock.h>
  
  #include <sys/socket.h>
  
  #include <net/if.h>
  #include <net/if_media.h>
  #include <net/ethernet.h>
  #include <net/route.h>
  
  #include <netproto/802_11/ieee80211_var.h>
  #include <netproto/802_11/ieee80211_input.h>
  #include <netproto/802_11/ieee80211_regdomain.h>
  #ifdef IEEE80211_SUPPORT_TDMA
  #include <netproto/802_11/ieee80211_tdma.h>
  #endif
  #ifdef IEEE80211_SUPPORT_MESH
  #include <netproto/802_11/ieee80211_mesh.h>
  #endif
  
  #include <net/bpf.h>
  
  /*
   * Parameters for managing cache entries:
   *
   * o a station with STA_FAILS_MAX failures is not considered
   *   when picking a candidate
   * o a station that hasn't had an update in STA_PURGE_SCANS
   *   (background) scans is discarded
   * o after STA_FAILS_AGE seconds we clear the failure count
   */
  #define	STA_FAILS_MAX	2		/* assoc failures before ignored */
  #define	STA_FAILS_AGE	(2*60)		/* time before clearing fails (secs) */
  #define	STA_PURGE_SCANS	2		/* age for purging entries (scans) */
  
  /* XXX tunable */
  #define	STA_RSSI_MIN	8		/* min acceptable rssi */
  #define	STA_RSSI_MAX	40		/* max rssi for comparison */
  
  struct sta_entry {
  	struct ieee80211_scan_entry base;
  	TAILQ_ENTRY(sta_entry) se_list;
  	LIST_ENTRY(sta_entry) se_hash;
  	uint8_t		se_fails;		/* failure to associate count */
  	uint8_t		se_seen;		/* seen during current scan */
  	uint8_t		se_notseen;		/* not seen in previous scans */
  	uint8_t		se_flags;
  #define	STA_DEMOTE11B	0x01			/* match w/ demoted 11b chan */
  	uint32_t	se_avgrssi;		/* LPF rssi state */
  	unsigned long	se_lastupdate;		/* time of last update */
  	unsigned long	se_lastfail;		/* time of last failure */
  	unsigned long	se_lastassoc;		/* time of last association */
  	u_int		se_scangen;		/* iterator scan gen# */
  	u_int		se_countrygen;		/* gen# of last cc notify */
  };
  
  #define	STA_HASHSIZE	32
  /* simple hash is enough for variation of macaddr */
  #define	STA_HASH(addr)	\
  	(((const uint8_t *)(addr))[IEEE80211_ADDR_LEN - 1] % STA_HASHSIZE)
  
  #define	MAX_IEEE_CHAN	256			/* max acceptable IEEE chan # */
  CTASSERT(MAX_IEEE_CHAN >= 256);
  
  struct sta_table {
  	struct lock	st_lock;		/* on scan table */
  	TAILQ_HEAD(, sta_entry) st_entry;	/* all entries */
  	LIST_HEAD(, sta_entry) st_hash[STA_HASHSIZE];
  	struct lock	st_scanlock;		/* on st_scaniter */
  	u_int		st_scaniter;		/* gen# for iterator */
  	u_int		st_scangen;		/* scan generation # */
  	int		st_newscan;
  	/* ap-related state */
  	int		st_maxrssi[MAX_IEEE_CHAN];
  };
  
  static void sta_flush_table(struct sta_table *);
  /*
   * match_bss returns a bitmask describing if an entry is suitable
   * for use.  If non-zero the entry was deemed not suitable and it's
   * contents explains why.  The following flags are or'd to to this
   * mask and can be used to figure out why the entry was rejected.
   */
  #define	MATCH_CHANNEL		0x00001	/* channel mismatch */
  #define	MATCH_CAPINFO		0x00002	/* capabilities mismatch, e.g. no ess */
  #define	MATCH_PRIVACY		0x00004	/* privacy mismatch */
  #define	MATCH_RATE		0x00008	/* rate set mismatch */
  #define	MATCH_SSID		0x00010	/* ssid mismatch */
  #define	MATCH_BSSID		0x00020	/* bssid mismatch */
  #define	MATCH_FAILS		0x00040	/* too many failed auth attempts */
  #define	MATCH_NOTSEEN		0x00080	/* not seen in recent scans */
  #define	MATCH_RSSI		0x00100	/* rssi deemed too low to use */
  #define	MATCH_CC		0x00200	/* country code mismatch */
  #define	MATCH_TDMA_NOIE		0x00400	/* no TDMA ie */
  #define	MATCH_TDMA_NOTMASTER	0x00800	/* not TDMA master */
  #define	MATCH_TDMA_NOSLOT	0x01000	/* all TDMA slots occupied */
  #define	MATCH_TDMA_LOCAL	0x02000	/* local address */
  #define	MATCH_TDMA_VERSION	0x04000	/* protocol version mismatch */
  #define	MATCH_MESH_NOID		0x10000	/* no MESHID ie */
  #define	MATCH_MESHID		0x20000	/* meshid mismatch */
  static int match_bss(struct ieee80211vap *,
  	const struct ieee80211_scan_state *, struct sta_entry *, int);
  static void adhoc_age(struct ieee80211_scan_state *);
  
  static __inline int
  isocmp(const uint8_t cc1[], const uint8_t cc2[])
  {
       return (cc1[0] == cc2[0] && cc1[1] == cc2[1]);
  }
  
  /* number of references from net80211 layer */
  static	int nrefs = 0;
  /*
   * Module glue.
   */
  IEEE80211_SCANNER_MODULE(sta, 1);
  
  /*
   * Attach prior to any scanning work.
   */
  static int
  sta_attach(struct ieee80211_scan_state *ss)
  {
  	struct sta_table *st;
  
  	st = (struct sta_table *) kmalloc(sizeof(struct sta_table),
  		M_80211_SCAN, M_INTWAIT | M_ZERO);
  	if (st == NULL)
  		return 0;
  	lockinit(&st->st_lock, "scantable", 0, 0);
  	lockinit(&st->st_scanlock, "scangen", 0, 0);
  	TAILQ_INIT(&st->st_entry);
  	ss->ss_priv = st;
  	nrefs++;			/* NB: we assume caller locking */
  	return 1;
  }
  
  /*
   * Cleanup any private state.
   */
  static int
  sta_detach(struct ieee80211_scan_state *ss)
  {
  	struct sta_table *st = ss->ss_priv;
  
  	if (st != NULL) {
  		sta_flush_table(st);
  		lockuninit(&st->st_lock);
  		lockuninit(&st->st_scanlock);
  		kfree(st, M_80211_SCAN);
  		KASSERT(nrefs > 0, ("imbalanced attach/detach"));
  		nrefs--;		/* NB: we assume caller locking */
  	}
  	return 1;
  }
  
  /*
   * Flush all per-scan state.
   */
  static int
  sta_flush(struct ieee80211_scan_state *ss)
  {
  	struct sta_table *st = ss->ss_priv;
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	sta_flush_table(st);
  	lockmgr(&st->st_lock, LK_RELEASE);
  	ss->ss_last = 0;
  	return 0;
  }
  
  /*
   * Flush all entries in the scan cache.
   */
  static void
  sta_flush_table(struct sta_table *st)
  {
  	struct sta_entry *se, *next;
  
  	TAILQ_FOREACH_MUTABLE(se, &st->st_entry, se_list, next) {
  		TAILQ_REMOVE(&st->st_entry, se, se_list);
  		LIST_REMOVE(se, se_hash);
  		ieee80211_ies_cleanup(&se->base.se_ies);
  		kfree(se, M_80211_SCAN);
  	}
  	memset(st->st_maxrssi, 0, sizeof(st->st_maxrssi));
  }
  
  /*
   * Process a beacon or probe response frame; create an
   * entry in the scan cache or update any previous entry.
   */
  static int
  sta_add(struct ieee80211_scan_state *ss, 
  	const struct ieee80211_scanparams *sp,
  	const struct ieee80211_frame *wh,
  	int subtype, int rssi, int noise)
  {
  #define	ISPROBE(_st)	((_st) == IEEE80211_FC0_SUBTYPE_PROBE_RESP)
  #define	PICK1ST(_ss) \
  	((ss->ss_flags & (IEEE80211_SCAN_PICK1ST | IEEE80211_SCAN_GOTPICK)) == \
  	IEEE80211_SCAN_PICK1ST)
  	struct sta_table *st = ss->ss_priv;
  	const uint8_t *macaddr = wh->i_addr2;
  	struct ieee80211vap *vap = ss->ss_vap;
  	struct ieee80211com *ic = vap->iv_ic;
  	struct sta_entry *se;
  	struct ieee80211_scan_entry *ise;
  	int hash;
  
  	hash = STA_HASH(macaddr);
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	LIST_FOREACH(se, &st->st_hash[hash], se_hash)
  		if (IEEE80211_ADDR_EQ(se->base.se_macaddr, macaddr))
  			goto found;
  	se = (struct sta_entry *) kmalloc(sizeof(struct sta_entry),
  		M_80211_SCAN, M_INTWAIT | M_ZERO);
  	if (se == NULL) {
  		lockmgr(&st->st_lock, LK_RELEASE);
  		return 0;
  	}
  	se->se_scangen = st->st_scaniter-1;
  	se->se_avgrssi = IEEE80211_RSSI_DUMMY_MARKER;
  	IEEE80211_ADDR_COPY(se->base.se_macaddr, macaddr);
  	TAILQ_INSERT_TAIL(&st->st_entry, se, se_list);
  	LIST_INSERT_HEAD(&st->st_hash[hash], se, se_hash);
  found:
  	ise = &se->base;
  	/* XXX ap beaconing multiple ssid w/ same bssid */
  	if (sp->ssid[1] != 0 &&
  	    (ISPROBE(subtype) || ise->se_ssid[1] == 0))
  		memcpy(ise->se_ssid, sp->ssid, 2+sp->ssid[1]);
  	KASSERT(sp->rates[1] <= IEEE80211_RATE_MAXSIZE,
  		("rate set too large: %u", sp->rates[1]));
  	memcpy(ise->se_rates, sp->rates, 2+sp->rates[1]);
  	if (sp->xrates != NULL) {
  		/* XXX validate xrates[1] */
  		KASSERT(sp->xrates[1] <= IEEE80211_RATE_MAXSIZE,
  			("xrate set too large: %u", sp->xrates[1]));
  		memcpy(ise->se_xrates, sp->xrates, 2+sp->xrates[1]);
  	} else
  		ise->se_xrates[1] = 0;
  	IEEE80211_ADDR_COPY(ise->se_bssid, wh->i_addr3);
  	if ((sp->status & IEEE80211_BPARSE_OFFCHAN) == 0) {
  		/*
  		 * Record rssi data using extended precision LPF filter.
  		 *
  		 * NB: use only on-channel data to insure we get a good
  		 *     estimate of the signal we'll see when associated.
  		 */
  		IEEE80211_RSSI_LPF(se->se_avgrssi, rssi);
  		ise->se_rssi = IEEE80211_RSSI_GET(se->se_avgrssi);
  		ise->se_noise = noise;
  	}
  	memcpy(ise->se_tstamp.data, sp->tstamp, sizeof(ise->se_tstamp));
  	ise->se_intval = sp->bintval;
  	ise->se_capinfo = sp->capinfo;
  #ifdef IEEE80211_SUPPORT_MESH
  	if (sp->meshid != NULL && sp->meshid[1] != 0)
  		memcpy(ise->se_meshid, sp->meshid, 2+sp->meshid[1]);
  #endif
  	/*
  	 * Beware of overriding se_chan for frames seen
  	 * off-channel; this can cause us to attempt an
  	 * association on the wrong channel.
  	 */
  	if (sp->status & IEEE80211_BPARSE_OFFCHAN) {
  		struct ieee80211_channel *c;
  		/*
  		 * Off-channel, locate the home/bss channel for the sta
  		 * using the value broadcast in the DSPARMS ie.  We know
  		 * sp->chan has this value because it's used to calculate
  		 * IEEE80211_BPARSE_OFFCHAN.
  		 */
  		c = ieee80211_find_channel_byieee(ic, sp->chan,
  		    ic->ic_curchan->ic_flags);
  		if (c != NULL) {
  			ise->se_chan = c;
  		} else if (ise->se_chan == NULL) {
  			/* should not happen, pick something */
  			ise->se_chan = ic->ic_curchan;
  		}
  	} else
  		ise->se_chan = ic->ic_curchan;
  	ise->se_fhdwell = sp->fhdwell;
  	ise->se_fhindex = sp->fhindex;
  	ise->se_erp = sp->erp;
  	ise->se_timoff = sp->timoff;
  	if (sp->tim != NULL) {
  		const struct ieee80211_tim_ie *tim =
  		    (const struct ieee80211_tim_ie *) sp->tim;
  		ise->se_dtimperiod = tim->tim_period;
  	}
  	if (sp->country != NULL) {
  		const struct ieee80211_country_ie *cie =
  		    (const struct ieee80211_country_ie *) sp->country;
  		/*
  		 * If 11d is enabled and we're attempting to join a bss
  		 * that advertises it's country code then compare our
  		 * current settings to what we fetched from the country ie.
  		 * If our country code is unspecified or different then
  		 * dispatch an event to user space that identifies the
  		 * country code so our regdomain config can be changed.
  		 */
  		/* XXX only for STA mode? */
  		if ((IEEE80211_IS_CHAN_11D(ise->se_chan) ||
  		    (vap->iv_flags_ext & IEEE80211_FEXT_DOTD)) &&
  		    (ic->ic_regdomain.country == CTRY_DEFAULT ||
  		     !isocmp(cie->cc, ic->ic_regdomain.isocc))) {
  			/* only issue one notify event per scan */
  			if (se->se_countrygen != st->st_scangen) {
  				ieee80211_notify_country(vap, ise->se_bssid,
  				    cie->cc);
  				se->se_countrygen = st->st_scangen;
  			}
  		}
  		ise->se_cc[0] = cie->cc[0];
  		ise->se_cc[1] = cie->cc[1];
  	}
  	/* NB: no need to setup ie ptrs; they are not (currently) used */
  	(void) ieee80211_ies_init(&ise->se_ies, sp->ies, sp->ies_len);
  
  	/* clear failure count after STA_FAIL_AGE passes */
  	if (se->se_fails && (ticks - se->se_lastfail) > STA_FAILS_AGE*hz) {
  		se->se_fails = 0;
  		IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_SCAN, macaddr,
  		    "%s: fails %u", __func__, se->se_fails);
  	}
  
  	se->se_lastupdate = ticks;		/* update time */
  	se->se_seen = 1;
  	se->se_notseen = 0;
  
  	KASSERT(sizeof(sp->bchan) == 1, ("bchan size"));
  	if (rssi > st->st_maxrssi[sp->bchan])
  		st->st_maxrssi[sp->bchan] = rssi;
  
  	lockmgr(&st->st_lock, LK_RELEASE);
  
  	/*
  	 * If looking for a quick choice and nothing's
  	 * been found check here.
  	 */
  	if (PICK1ST(ss) && match_bss(vap, ss, se, IEEE80211_MSG_SCAN) == 0)
  		ss->ss_flags |= IEEE80211_SCAN_GOTPICK;
  
  	return 1;
  #undef PICK1ST
  #undef ISPROBE
  }
  
  /*
   * Check if a channel is excluded by user request.
   */
  static int
  isexcluded(struct ieee80211vap *vap, const struct ieee80211_channel *c)
  {
  	return (isclr(vap->iv_ic->ic_chan_active, c->ic_ieee) ||
  	    (vap->iv_des_chan != IEEE80211_CHAN_ANYC &&
  	     c->ic_freq != vap->iv_des_chan->ic_freq));
  }
  
  static struct ieee80211_channel *
  find11gchannel(struct ieee80211com *ic, int i, int freq)
  {
  	struct ieee80211_channel *c;
  	int j;
  
  	/*
  	 * The normal ordering in the channel list is b channel
  	 * immediately followed by g so optimize the search for
  	 * this.  We'll still do a full search just in case.
  	 */
  	for (j = i+1; j < ic->ic_nchans; j++) {
  		c = &ic->ic_channels[j];
  		if (c->ic_freq == freq && IEEE80211_IS_CHAN_G(c))
  			return c;
  	}
  	for (j = 0; j < i; j++) {
  		c = &ic->ic_channels[j];
  		if (c->ic_freq == freq && IEEE80211_IS_CHAN_G(c))
  			return c;
  	}
  	return NULL;
  }
  
  static const u_int chanflags[IEEE80211_MODE_MAX] = {
  	[IEEE80211_MODE_AUTO]	  = IEEE80211_CHAN_B,
  	[IEEE80211_MODE_11A]	  = IEEE80211_CHAN_A,
  	[IEEE80211_MODE_11B]	  = IEEE80211_CHAN_B,
  	[IEEE80211_MODE_11G]	  = IEEE80211_CHAN_G,
  	[IEEE80211_MODE_FH]	  = IEEE80211_CHAN_FHSS,
  	/* check base channel */
  	[IEEE80211_MODE_TURBO_A]  = IEEE80211_CHAN_A,
  	[IEEE80211_MODE_TURBO_G]  = IEEE80211_CHAN_G,
  	[IEEE80211_MODE_STURBO_A] = IEEE80211_CHAN_ST,
  	[IEEE80211_MODE_HALF]	  = IEEE80211_CHAN_HALF,
  	[IEEE80211_MODE_QUARTER]  = IEEE80211_CHAN_QUARTER,
  	/* check legacy */
  	[IEEE80211_MODE_11NA]	  = IEEE80211_CHAN_A,
  	[IEEE80211_MODE_11NG]	  = IEEE80211_CHAN_G,
  };
  
  static void
  add_channels(struct ieee80211vap *vap,
  	struct ieee80211_scan_state *ss,
  	enum ieee80211_phymode mode, const uint16_t freq[], int nfreq)
  {
  	struct ieee80211com *ic = vap->iv_ic;
  	struct ieee80211_channel *c, *cg;
  	u_int modeflags;
  	int i;
  
  	KASSERT(mode < NELEM(chanflags), ("Unexpected mode %u", mode));
  	modeflags = chanflags[mode];
  	for (i = 0; i < nfreq; i++) {
  		if (ss->ss_last >= IEEE80211_SCAN_MAX)
  			break;
  
  		c = ieee80211_find_channel(ic, freq[i], modeflags);
  		if (c == NULL || isexcluded(vap, c))
  			continue;
  		if (mode == IEEE80211_MODE_AUTO) {
  			/*
  			 * XXX special-case 11b/g channels so we select
  			 *     the g channel if both are present.
  			 */
  			if (IEEE80211_IS_CHAN_B(c) &&
  			    (cg = find11gchannel(ic, i, c->ic_freq)) != NULL)
  				c = cg;
  		}
  		ss->ss_chans[ss->ss_last++] = c;
  	}
  }
  
  struct scanlist {
  	uint16_t	mode;
  	uint16_t	count;
  	const uint16_t	*list;
  };
  
  static int
  checktable(const struct scanlist *scan, const struct ieee80211_channel *c)
  {
  	int i;
  
  	for (; scan->list != NULL; scan++) {
  		for (i = 0; i < scan->count; i++)
  			if (scan->list[i] == c->ic_freq) 
  				return 1;
  	}
  	return 0;
  }
  
  static int
  onscanlist(const struct ieee80211_scan_state *ss,
  	const struct ieee80211_channel *c)
  {
  	int i;
  
  	for (i = 0; i < ss->ss_last; i++)
  		if (ss->ss_chans[i] == c)
  			return 1;
  	return 0;
  }
  
  static void
  sweepchannels(struct ieee80211_scan_state *ss, struct ieee80211vap *vap,
  	const struct scanlist table[])
  {
  	struct ieee80211com *ic = vap->iv_ic;
  	struct ieee80211_channel *c;
  	int i;
  
  	for (i = 0; i < ic->ic_nchans; i++) {
  		if (ss->ss_last >= IEEE80211_SCAN_MAX)
  			break;
  
  		c = &ic->ic_channels[i];
  		/*
  		 * Ignore dynamic turbo channels; we scan them
  		 * in normal mode (i.e. not boosted).  Likewise
  		 * for HT channels, they get scanned using
  		 * legacy rates.
  		 */
  		if (IEEE80211_IS_CHAN_DTURBO(c) || IEEE80211_IS_CHAN_HT(c))
  			continue;
  
  		/*
  		 * If a desired mode was specified, scan only 
  		 * channels that satisfy that constraint.
  		 */
  		if (vap->iv_des_mode != IEEE80211_MODE_AUTO &&
  		    vap->iv_des_mode != ieee80211_chan2mode(c))
  			continue;
  
  		/*
  		 * Skip channels excluded by user request.
  		 */
  		if (isexcluded(vap, c))
  			continue;
  
  		/*
  		 * Add the channel unless it is listed in the
  		 * fixed scan order tables.  This insures we
  		 * don't sweep back in channels we filtered out
  		 * above.
  		 */
  		if (checktable(table, c))
  			continue;
  
  		/* Add channel to scanning list. */
  		ss->ss_chans[ss->ss_last++] = c;
  	}
  	/*
  	 * Explicitly add any desired channel if:
  	 * - not already on the scan list
  	 * - allowed by any desired mode constraint
  	 * - there is space in the scan list
  	 * This allows the channel to be used when the filtering
  	 * mechanisms would otherwise elide it (e.g HT, turbo).
  	 */
  	c = vap->iv_des_chan;
  	if (c != IEEE80211_CHAN_ANYC &&
  	    !onscanlist(ss, c) &&
  	    (vap->iv_des_mode == IEEE80211_MODE_AUTO ||
  	     vap->iv_des_mode == ieee80211_chan2mode(c)) &&
  	    ss->ss_last < IEEE80211_SCAN_MAX)
  		ss->ss_chans[ss->ss_last++] = c;
  }
  
  static void
  makescanlist(struct ieee80211_scan_state *ss, struct ieee80211vap *vap,
  	const struct scanlist table[])
  {
  	const struct scanlist *scan;
  	enum ieee80211_phymode mode;
  
  	ss->ss_last = 0;
  	/*
  	 * Use the table of ordered channels to construct the list
  	 * of channels for scanning.  Any channels in the ordered
  	 * list not in the master list will be discarded.
  	 */
  	for (scan = table; scan->list != NULL; scan++) {
  		mode = scan->mode;
  		if (vap->iv_des_mode != IEEE80211_MODE_AUTO) {
  			/*
  			 * If a desired mode was specified, scan only 
  			 * channels that satisfy that constraint.
  			 */
  			if (vap->iv_des_mode != mode) {
  				/*
  				 * The scan table marks 2.4Ghz channels as b
  				 * so if the desired mode is 11g, then use
  				 * the 11b channel list but upgrade the mode.
  				 */
  				if (vap->iv_des_mode != IEEE80211_MODE_11G ||
  				    mode != IEEE80211_MODE_11B)
  					continue;
  				mode = IEEE80211_MODE_11G;	/* upgrade */
  			}
  		} else {
  			/*
  			 * This lets add_channels upgrade an 11b channel
  			 * to 11g if available.
  			 */
  			if (mode == IEEE80211_MODE_11B)
  				mode = IEEE80211_MODE_AUTO;
  		}
  #ifdef IEEE80211_F_XR
  		/* XR does not operate on turbo channels */
  		if ((vap->iv_flags & IEEE80211_F_XR) &&
  		    (mode == IEEE80211_MODE_TURBO_A ||
  		     mode == IEEE80211_MODE_TURBO_G ||
  		     mode == IEEE80211_MODE_STURBO_A))
  			continue;
  #endif
  		/*
  		 * Add the list of the channels; any that are not
  		 * in the master channel list will be discarded.
  		 */
  		add_channels(vap, ss, mode, scan->list, scan->count);
  	}
  
  	/*
  	 * Add the channels from the ic that are not present
  	 * in the table.
  	 */
  	sweepchannels(ss, vap, table);
  }
  
  static const uint16_t rcl1[] =		/* 8 FCC channel: 52, 56, 60, 64, 36, 40, 44, 48 */
  { 5260, 5280, 5300, 5320, 5180, 5200, 5220, 5240 };
  static const uint16_t rcl2[] =		/* 4 MKK channels: 34, 38, 42, 46 */
  { 5170, 5190, 5210, 5230 };
  static const uint16_t rcl3[] =		/* 2.4Ghz ch: 1,6,11,7,13 */
  { 2412, 2437, 2462, 2442, 2472 };
  static const uint16_t rcl4[] =		/* 5 FCC channel: 149, 153, 161, 165 */
  { 5745, 5765, 5785, 5805, 5825 };
  static const uint16_t rcl7[] =		/* 11 ETSI channel: 100,104,108,112,116,120,124,128,132,136,140 */
  { 5500, 5520, 5540, 5560, 5580, 5600, 5620, 5640, 5660, 5680, 5700 };
  static const uint16_t rcl8[] =		/* 2.4Ghz ch: 2,3,4,5,8,9,10,12 */
  { 2417, 2422, 2427, 2432, 2447, 2452, 2457, 2467 };
  static const uint16_t rcl9[] =		/* 2.4Ghz ch: 14 */
  { 2484 };
  static const uint16_t rcl10[] =	/* Added Korean channels 2312-2372 */
  { 2312, 2317, 2322, 2327, 2332, 2337, 2342, 2347, 2352, 2357, 2362, 2367, 2372 };
  static const uint16_t rcl11[] =	/* Added Japan channels in 4.9/5.0 spectrum */
  { 5040, 5060, 5080, 4920, 4940, 4960, 4980 };
  #ifdef ATH_TURBO_SCAN
  static const uint16_t rcl5[] =		/* 3 static turbo channels */
  { 5210, 5250, 5290 };
  static const uint16_t rcl6[] =		/* 2 static turbo channels */
  { 5760, 5800 };
  static const uint16_t rcl6x[] =	/* 4 FCC3 turbo channels */
  { 5540, 5580, 5620, 5660 };
  static const uint16_t rcl12[] =	/* 2.4Ghz Turbo channel 6 */
  { 2437 };
  static const uint16_t rcl13[] =	/* dynamic Turbo channels */
  { 5200, 5240, 5280, 5765, 5805 };
  #endif /* ATH_TURBO_SCAN */
  
  #define	X(a)	.count = NELEM(a), .list = a
  
  static const struct scanlist staScanTable[] = {
  	{ IEEE80211_MODE_11B,   	X(rcl3) },
  	{ IEEE80211_MODE_11A,   	X(rcl1) },
  	{ IEEE80211_MODE_11A,   	X(rcl2) },
  	{ IEEE80211_MODE_11B,   	X(rcl8) },
  	{ IEEE80211_MODE_11B,   	X(rcl9) },
  	{ IEEE80211_MODE_11A,   	X(rcl4) },
  #ifdef ATH_TURBO_SCAN
  	{ IEEE80211_MODE_STURBO_A,	X(rcl5) },
  	{ IEEE80211_MODE_STURBO_A,	X(rcl6) },
  	{ IEEE80211_MODE_TURBO_A,	X(rcl6x) },
  	{ IEEE80211_MODE_TURBO_A,	X(rcl13) },
  #endif /* ATH_TURBO_SCAN */
  	{ IEEE80211_MODE_11A,		X(rcl7) },
  	{ IEEE80211_MODE_11B,		X(rcl10) },
  	{ IEEE80211_MODE_11A,		X(rcl11) },
  #ifdef ATH_TURBO_SCAN
  	{ IEEE80211_MODE_TURBO_G,	X(rcl12) },
  #endif /* ATH_TURBO_SCAN */
  	{ .list = NULL }
  };
  
  /*
   * Start a station-mode scan by populating the channel list.
   */
  static int
  sta_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  
  	makescanlist(ss, vap, staScanTable);
  
  	if (ss->ss_mindwell == 0)
  		ss->ss_mindwell = msecs_to_ticks(20);	/* 20ms */
  	if (ss->ss_maxdwell == 0)
  		ss->ss_maxdwell = msecs_to_ticks(200);	/* 200ms */
  
  	st->st_scangen++;
  	st->st_newscan = 1;
  
  	return 0;
  }
  
  /*
   * Restart a scan, typically a bg scan but can
   * also be a fg scan that came up empty.
   */
  static int
  sta_restart(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  
  	st->st_newscan = 1;
  	return 0;
  }
  
  /*
   * Cancel an ongoing scan.
   */
  static int
  sta_cancel(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	return 0;
  }
  
  /* unalligned little endian access */     
  #define LE_READ_2(p)					\
  	((uint16_t)					\
  	 ((((const uint8_t *)(p))[0]      ) |		\
  	  (((const uint8_t *)(p))[1] <<  8)))
   
  /*
   * Demote any supplied 11g channel to 11b.  There should
   * always be an 11b channel but we check anyway...
   */
  static struct ieee80211_channel *
  demote11b(struct ieee80211vap *vap, struct ieee80211_channel *chan)
  {
  	struct ieee80211_channel *c;
  
  	if (IEEE80211_IS_CHAN_ANYG(chan) &&
  	    vap->iv_des_mode == IEEE80211_MODE_AUTO) {
  		c = ieee80211_find_channel(vap->iv_ic, chan->ic_freq,
  		    (chan->ic_flags &~ (IEEE80211_CHAN_PUREG | IEEE80211_CHAN_G)) |
  		    IEEE80211_CHAN_B);
  		if (c != NULL)
  			chan = c;
  	}
  	return chan;
  }
  
  static int
  maxrate(const struct ieee80211_scan_entry *se)
  {
  	const struct ieee80211_ie_htcap *htcap =
  	    (const struct ieee80211_ie_htcap *) se->se_ies.htcap_ie;
  	int rmax, r, i;
  	uint16_t caps;
  
  	rmax = 0;
  	if (htcap != NULL) {
  		/*
  		 * HT station; inspect supported MCS and then adjust
  		 * rate by channel width.  Could also include short GI
  		 * in this if we want to be extra accurate.
  		 */
  		/* XXX assumes MCS15 is max */
  		for (i = 15; i >= 0 && isclr(htcap->hc_mcsset, i); i--)
  			;
  		if (i >= 0) {
  			caps = LE_READ_2(&htcap->hc_cap);
  			/* XXX short/long GI */
  			if (caps & IEEE80211_HTCAP_CHWIDTH40)
  				rmax = ieee80211_htrates[i].ht40_rate_400ns;
  			else
  				rmax = ieee80211_htrates[i].ht40_rate_800ns;
  		}
  	}
  	for (i = 0; i < se->se_rates[1]; i++) {
  		r = se->se_rates[2+i] & IEEE80211_RATE_VAL;
  		if (r > rmax)
  			rmax = r;
  	}
  	for (i = 0; i < se->se_xrates[1]; i++) {
  		r = se->se_xrates[2+i] & IEEE80211_RATE_VAL;
  		if (r > rmax)
  			rmax = r;
  	}
  	return rmax;
  }
  
  /*
   * Compare the capabilities of two entries and decide which is
   * more desirable (return >0 if a is considered better).  Note
   * that we assume compatibility/usability has already been checked
   * so we don't need to (e.g. validate whether privacy is supported).
   * Used to select the best scan candidate for association in a BSS.
   */
  static int
  sta_compare(const struct sta_entry *a, const struct sta_entry *b)
  {
  #define	PREFER(_a,_b,_what) do {			\
  	if (((_a) ^ (_b)) & (_what))			\
  		return ((_a) & (_what)) ? 1 : -1;	\
  } while (0)
  #define	ABS(_a) ((_a) < 0 ? -(_a) : (_a))
  	int maxa, maxb;
  	int8_t rssia, rssib;
  	int weight;
  
  	/* privacy support */
  	PREFER(a->base.se_capinfo, b->base.se_capinfo,
  		IEEE80211_CAPINFO_PRIVACY);
  
  	/* compare count of previous failures */
  	weight = b->se_fails - a->se_fails;
  	if (ABS(weight) > 1)
  		return weight;
  
  	/*
  	 * Compare rssi.  If the two are considered equivalent
  	 * then fallback to other criteria.  We threshold the
  	 * comparisons to avoid selecting an ap purely by rssi
  	 * when both values may be good but one ap is otherwise
  	 * more desirable (e.g. an 11b-only ap with stronger
  	 * signal than an 11g ap).
  	 */
  	rssia = MIN(a->base.se_rssi, STA_RSSI_MAX);
  	rssib = MIN(b->base.se_rssi, STA_RSSI_MAX);
  	if (ABS(rssib - rssia) < 5) {
  		/* best/max rate preferred if signal level close enough XXX */
  		maxa = maxrate(&a->base);
  		maxb = maxrate(&b->base);
  		if (maxa != maxb)
  			return maxa - maxb;
  		/* XXX use freq for channel preference */
  		/* for now just prefer 5Ghz band to all other bands */
  		PREFER(IEEE80211_IS_CHAN_5GHZ(a->base.se_chan),
  		       IEEE80211_IS_CHAN_5GHZ(b->base.se_chan), 1);
  	}
  	/* all things being equal, use signal level */
  	return a->base.se_rssi - b->base.se_rssi;
  #undef PREFER
  #undef ABS
  }
  
  /*
   * Check rate set suitability and return the best supported rate.
   * XXX inspect MCS for HT
   */
  static int
  check_rate(struct ieee80211vap *vap, const struct ieee80211_channel *chan,
      const struct ieee80211_scan_entry *se)
  {
  #define	RV(v)	((v) & IEEE80211_RATE_VAL)
  	const struct ieee80211_rateset *srs;
  	int i, j, nrs, r, okrate, badrate, fixedrate, ucastrate;
  	const uint8_t *rs;
  
  	okrate = badrate = 0;
  
  	srs = ieee80211_get_suprates(vap->iv_ic, chan);
  	nrs = se->se_rates[1];
  	rs = se->se_rates+2;
  	/* XXX MCS */
  	ucastrate = vap->iv_txparms[ieee80211_chan2mode(chan)].ucastrate;
  	fixedrate = IEEE80211_FIXED_RATE_NONE;
  again:
  	for (i = 0; i < nrs; i++) {
  		r = RV(rs[i]);
  		badrate = r;
  		/*
  		 * Check any fixed rate is included. 
  		 */
  		if (r == ucastrate)
  			fixedrate = r;
  		/*
  		 * Check against our supported rates.
  		 */
  		for (j = 0; j < srs->rs_nrates; j++)
  			if (r == RV(srs->rs_rates[j])) {
  				if (r > okrate)		/* NB: track max */
  					okrate = r;
  				break;
  			}
  
  		if (j == srs->rs_nrates && (rs[i] & IEEE80211_RATE_BASIC)) {
  			/*
  			 * Don't try joining a BSS, if we don't support
  			 * one of its basic rates.
  			 */
  			okrate = 0;
  			goto back;
  		}
  	}
  	if (rs == se->se_rates+2) {
  		/* scan xrates too; sort of an algol68-style for loop */
  		nrs = se->se_xrates[1];
  		rs = se->se_xrates+2;
  		goto again;
  	}
  
  back:
  	if (okrate == 0 || ucastrate != fixedrate)
  		return badrate | IEEE80211_RATE_BASIC;
  	else
  		return RV(okrate);
  #undef RV
  }
  
  static __inline int
  match_id(const uint8_t *ie, const uint8_t *val, int len)
  {
  	return (ie[1] == len && memcmp(ie+2, val, len) == 0);
  }
  
  static int
  match_ssid(const uint8_t *ie,
  	int nssid, const struct ieee80211_scan_ssid ssids[])
  {
  	int i;
  
  	for (i = 0; i < nssid; i++) {
  		if (match_id(ie, ssids[i].ssid, ssids[i].len))
  			return 1;
  	}
  	return 0;
  }
  
  #ifdef IEEE80211_SUPPORT_TDMA
  static int
  tdma_isfull(const struct ieee80211_tdma_param *tdma)
  {
  	int slot, slotcnt;
  
  	slotcnt = tdma->tdma_slotcnt;
  	for (slot = slotcnt-1; slot >= 0; slot--)
  		if (isclr(tdma->tdma_inuse, slot))
  			return 0;
  	return 1;
  }
  #endif /* IEEE80211_SUPPORT_TDMA */
  
  /*
   * Test a scan candidate for suitability/compatibility.
   */
  static int
  match_bss(struct ieee80211vap *vap,
  	const struct ieee80211_scan_state *ss, struct sta_entry *se0,
  	int debug)
  {
  	struct ieee80211com *ic = vap->iv_ic;
  	struct ieee80211_scan_entry *se = &se0->base;
          uint8_t rate;
          int fail;
  
  	fail = 0;
  	if (isclr(ic->ic_chan_active, ieee80211_chan2ieee(ic, se->se_chan)))
  		fail |= MATCH_CHANNEL;
  	/*
  	 * NB: normally the desired mode is used to construct
  	 * the channel list, but it's possible for the scan
  	 * cache to include entries for stations outside this
  	 * list so we check the desired mode here to weed them
  	 * out.
  	 */
  	if (vap->iv_des_mode != IEEE80211_MODE_AUTO &&
  	    (se->se_chan->ic_flags & IEEE80211_CHAN_ALLTURBO) !=
  	    chanflags[vap->iv_des_mode])
  		fail |= MATCH_CHANNEL;
  	if (vap->iv_opmode == IEEE80211_M_IBSS) {
  		if ((se->se_capinfo & IEEE80211_CAPINFO_IBSS) == 0)
  			fail |= MATCH_CAPINFO;
  #ifdef IEEE80211_SUPPORT_TDMA
  	} else if (vap->iv_opmode == IEEE80211_M_AHDEMO) {
  		/*
  		 * Adhoc demo network setup shouldn't really be scanning
  		 * but just in case skip stations operating in IBSS or
  		 * BSS mode.
  		 */
  		if (se->se_capinfo & (IEEE80211_CAPINFO_IBSS|IEEE80211_CAPINFO_ESS))
  			fail |= MATCH_CAPINFO;
  		/*
  		 * TDMA operation cannot coexist with a normal 802.11 network;
  		 * skip if IBSS or ESS capabilities are marked and require
  		 * the beacon have a TDMA ie present.
  		 */
  		if (vap->iv_caps & IEEE80211_C_TDMA) {
  			const struct ieee80211_tdma_param *tdma =
  			    (const struct ieee80211_tdma_param *)se->se_ies.tdma_ie;
  			const struct ieee80211_tdma_state *ts = vap->iv_tdma;
  
  			if (tdma == NULL)
  				fail |= MATCH_TDMA_NOIE;
  			else if (tdma->tdma_version != ts->tdma_version)
  				fail |= MATCH_TDMA_VERSION;
  			else if (tdma->tdma_slot != 0)
  				fail |= MATCH_TDMA_NOTMASTER;
  			else if (tdma_isfull(tdma))
  				fail |= MATCH_TDMA_NOSLOT;
  #if 0
  			else if (ieee80211_local_address(se->se_macaddr))
  				fail |= MATCH_TDMA_LOCAL;
  #endif
  		}
  #endif /* IEEE80211_SUPPORT_TDMA */
  #ifdef IEEE80211_SUPPORT_MESH
  	} else if (vap->iv_opmode == IEEE80211_M_MBSS) {
  		const struct ieee80211_mesh_state *ms = vap->iv_mesh;
  		/*
  		 * Mesh nodes have IBSS & ESS bits in capinfo turned off
  		 * and two special ie's that must be present.
  		 */
  		if (se->se_capinfo & (IEEE80211_CAPINFO_IBSS|IEEE80211_CAPINFO_ESS))
  			fail |= MATCH_CAPINFO;
  		else if (&se->se_meshid == NULL)
  			fail |= MATCH_MESH_NOID;
  		else if (ms->ms_idlen != 0 &&
  		    match_id(se->se_meshid, ms->ms_id, ms->ms_idlen))
  			fail |= MATCH_MESHID;
  #endif
  	} else {
  		if ((se->se_capinfo & IEEE80211_CAPINFO_ESS) == 0)
  			fail |= MATCH_CAPINFO;
  		/*
  		 * If 11d is enabled and we're attempting to join a bss
  		 * that advertises it's country code then compare our
  		 * current settings to what we fetched from the country ie.
  		 * If our country code is unspecified or different then do
  		 * not attempt to join the bss.  We should have already
  		 * dispatched an event to user space that identifies the
  		 * new country code so our regdomain config should match.
  		 */
  		if ((IEEE80211_IS_CHAN_11D(se->se_chan) ||
  		    (vap->iv_flags_ext & IEEE80211_FEXT_DOTD)) &&
  		    se->se_cc[0] != 0 &&
  		    (ic->ic_regdomain.country == CTRY_DEFAULT ||
  		     !isocmp(se->se_cc, ic->ic_regdomain.isocc)))
  			fail |= MATCH_CC;
  	}
  	if (vap->iv_flags & IEEE80211_F_PRIVACY) {
  		if ((se->se_capinfo & IEEE80211_CAPINFO_PRIVACY) == 0)
  			fail |= MATCH_PRIVACY;
  	} else {
  		/* XXX does this mean privacy is supported or required? */
  		if (se->se_capinfo & IEEE80211_CAPINFO_PRIVACY)
  			fail |= MATCH_PRIVACY;
  	}
  	se0->se_flags &= ~STA_DEMOTE11B;
  	rate = check_rate(vap, se->se_chan, se);
  	if (rate & IEEE80211_RATE_BASIC) {
  		fail |= MATCH_RATE;
  		/*
  		 * An 11b-only ap will give a rate mismatch if there is an
  		 * OFDM fixed tx rate for 11g.  Try downgrading the channel
  		 * in the scan list to 11b and retry the rate check.
  		 */
  		if (IEEE80211_IS_CHAN_ANYG(se->se_chan)) {
  			rate = check_rate(vap, demote11b(vap, se->se_chan), se);
  			if ((rate & IEEE80211_RATE_BASIC) == 0) {
  				fail &= ~MATCH_RATE;
  				se0->se_flags |= STA_DEMOTE11B;
  			}
  		}
  	} else if (rate < 2*24) {
  		/*
  		 * This is an 11b-only ap.  Check the desired mode in
  		 * case that needs to be honored (mode 11g filters out
  		 * 11b-only ap's).  Otherwise force any 11g channel used
  		 * in scanning to be demoted.
  		 *
  		 * NB: we cheat a bit here by looking at the max rate;
  		 *     we could/should check the rates.
  		 */
  		if (!(vap->iv_des_mode == IEEE80211_MODE_AUTO ||
  		      vap->iv_des_mode == IEEE80211_MODE_11B))
  			fail |= MATCH_RATE;
  		else
  			se0->se_flags |= STA_DEMOTE11B;
  	}
  	if (ss->ss_nssid != 0 &&
  	    !match_ssid(se->se_ssid, ss->ss_nssid, ss->ss_ssid))
  		fail |= MATCH_SSID;
  	if ((vap->iv_flags & IEEE80211_F_DESBSSID) &&
  	    !IEEE80211_ADDR_EQ(vap->iv_des_bssid, se->se_bssid))
  		fail |= MATCH_BSSID;
  	if (se0->se_fails >= STA_FAILS_MAX)
  		fail |= MATCH_FAILS;
  	if (se0->se_notseen >= STA_PURGE_SCANS)
  		fail |= MATCH_NOTSEEN;
  	if (se->se_rssi < STA_RSSI_MIN)
  		fail |= MATCH_RSSI;
  #ifdef IEEE80211_DEBUG
  	if (ieee80211_msg(vap, debug)) {
  		kprintf(" %c %6D",
  		    fail & MATCH_FAILS ? '=' :
  		    fail & MATCH_NOTSEEN ? '^' :
  		    fail & MATCH_CC ? '$' :
  #ifdef IEEE80211_SUPPORT_TDMA
  		    fail & MATCH_TDMA_NOIE ? '&' :
  		    fail & MATCH_TDMA_VERSION ? 'v' :
  		    fail & MATCH_TDMA_NOTMASTER ? 's' :
  		    fail & MATCH_TDMA_NOSLOT ? 'f' :
  		    fail & MATCH_TDMA_LOCAL ? 'l' :
  #endif
  		    fail & MATCH_MESH_NOID ? 'm' :
  		    fail ? '-' : '+', se->se_macaddr, ":");
  		kprintf(" %6D%c", se->se_bssid, ":",
  		    fail & MATCH_BSSID ? '!' : ' ');
  		kprintf(" %3d%c", ieee80211_chan2ieee(ic, se->se_chan),
  			fail & MATCH_CHANNEL ? '!' : ' ');
  		kprintf(" %+4d%c", se->se_rssi, fail & MATCH_RSSI ? '!' : ' ');
  		kprintf(" %2dM%c", (rate & IEEE80211_RATE_VAL) / 2,
  		    fail & MATCH_RATE ? '!' : ' ');
  		kprintf(" %4s%c",
  		    (se->se_capinfo & IEEE80211_CAPINFO_ESS) ? "ess" :
  		    (se->se_capinfo & IEEE80211_CAPINFO_IBSS) ? "ibss" : "",
  		    fail & MATCH_CAPINFO ? '!' : ' ');
  		kprintf(" %3s%c ",
  		    (se->se_capinfo & IEEE80211_CAPINFO_PRIVACY) ?
  		    "wep" : "no",
  		    fail & MATCH_PRIVACY ? '!' : ' ');
  		ieee80211_print_essid(se->se_ssid+2, se->se_ssid[1]);
  		kprintf("%s\n", fail & (MATCH_SSID | MATCH_MESHID) ? "!" : "");
  	}
  #endif
  	return fail;
  }
  
  static void
  sta_update_notseen(struct sta_table *st)
  {
  	struct sta_entry *se;
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	TAILQ_FOREACH(se, &st->st_entry, se_list) {
  		/*
  		 * If seen the reset and don't bump the count;
  		 * otherwise bump the ``not seen'' count.  Note
  		 * that this insures that stations for which we
  		 * see frames while not scanning but not during
  		 * this scan will not be penalized.
  		 */
  		if (se->se_seen)
  			se->se_seen = 0;
  		else
  			se->se_notseen++;
  	}
  	lockmgr(&st->st_lock, LK_RELEASE);
  }
  
  static void
  sta_dec_fails(struct sta_table *st)
  {
  	struct sta_entry *se;
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	TAILQ_FOREACH(se, &st->st_entry, se_list)
  		if (se->se_fails)
  			se->se_fails--;
  	lockmgr(&st->st_lock, LK_RELEASE);
  }
  
  static struct sta_entry *
  select_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap, int debug)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se, *selbs = NULL;
  
  	IEEE80211_DPRINTF(vap, debug, " %s\n",
  	    "macaddr          bssid         chan  rssi  rate flag  wep  essid");
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	TAILQ_FOREACH(se, &st->st_entry, se_list) {
  		ieee80211_ies_expand(&se->base.se_ies);
  		if (match_bss(vap, ss, se, debug) == 0) {
  			if (selbs == NULL)
  				selbs = se;
  			else if (sta_compare(se, selbs) > 0)
  				selbs = se;
  		}
  	}
  	lockmgr(&st->st_lock, LK_RELEASE);
  
  	return selbs;
  }
  
  /*
   * Pick an ap or ibss network to join or find a channel
   * to use to start an ibss network.
   */
  static int
  sta_pick_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *selbs;
  	struct ieee80211_channel *chan;
  
  	KASSERT(vap->iv_opmode == IEEE80211_M_STA,
  		("wrong mode %u", vap->iv_opmode));
  
  	if (st->st_newscan) {
  		sta_update_notseen(st);
  		st->st_newscan = 0;
  	}
  	if (ss->ss_flags & IEEE80211_SCAN_NOPICK) {
  		/*
  		 * Manual/background scan, don't select+join the
  		 * bss, just return.  The scanning framework will
  		 * handle notification that this has completed.
  		 */
  		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
  		return 1;
  	}
  	/*
  	 * Automatic sequencing; look for a candidate and
  	 * if found join the network.
  	 */
  	/* NB: unlocked read should be ok */
  	if (TAILQ_FIRST(&st->st_entry) == NULL) {
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
  			"%s: no scan candidate\n", __func__);
  		if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  			return 0;
  notfound:
  		/*
  		 * If nothing suitable was found decrement
  		 * the failure counts so entries will be
  		 * reconsidered the next time around.  We
  		 * really want to do this only for sta's
  		 * where we've previously had some success.
  		 */
  		sta_dec_fails(st);
  		st->st_newscan = 1;
  		return 0;			/* restart scan */
  	}
  	selbs = select_bss(ss, vap, IEEE80211_MSG_SCAN);
  	if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  		return (selbs != NULL);
  	if (selbs == NULL)
  		goto notfound;
  	chan = selbs->base.se_chan;
  	if (selbs->se_flags & STA_DEMOTE11B)
  		chan = demote11b(vap, chan);
  	if (!ieee80211_sta_join(vap, chan, &selbs->base))
  		goto notfound;
  	return 1;				/* terminate scan */
  }
  
  /*
   * Lookup an entry in the scan cache.  We assume we're
   * called from the bottom half or such that we don't need
   * to block the bottom half so that it's safe to return
   * a reference to an entry w/o holding the lock on the table.
   */
  static struct sta_entry *
  sta_lookup(struct sta_table *st, const uint8_t macaddr[IEEE80211_ADDR_LEN])
  {
  	struct sta_entry *se;
  	int hash = STA_HASH(macaddr);
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	LIST_FOREACH(se, &st->st_hash[hash], se_hash)
  		if (IEEE80211_ADDR_EQ(se->base.se_macaddr, macaddr))
  			break;
  	lockmgr(&st->st_lock, LK_RELEASE);
  
  	return se;		/* NB: unlocked */
  }
  
  static void
  sta_roam_check(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct ieee80211com *ic = vap->iv_ic;
  	struct ieee80211_node *ni = vap->iv_bss;
  	struct sta_table *st = ss->ss_priv;
  	enum ieee80211_phymode mode;
  	struct sta_entry *se, *selbs;
  	uint8_t roamRate, curRate, ucastRate;
  	int8_t roamRssi, curRssi;
  
  	se = sta_lookup(st, ni->ni_macaddr);
  	if (se == NULL) {
  		/* XXX something is wrong */
  		return;
  	}
  
  	mode = ieee80211_chan2mode(ic->ic_bsschan);
  	roamRate = vap->iv_roamparms[mode].rate;
  	roamRssi = vap->iv_roamparms[mode].rssi;
  	ucastRate = vap->iv_txparms[mode].ucastrate;
  	/* NB: the most up to date rssi is in the node, not the scan cache */
  	curRssi = ic->ic_node_getrssi(ni);
  	if (ucastRate == IEEE80211_FIXED_RATE_NONE) {
  		curRate = ni->ni_txrate;
  		roamRate &= IEEE80211_RATE_VAL;
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_ROAM,
  		    "%s: currssi %d currate %u roamrssi %d roamrate %u\n",
  		    __func__, curRssi, curRate, roamRssi, roamRate);
  	} else {
  		curRate = roamRate;	/* NB: insure compare below fails */
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_ROAM,
  		    "%s: currssi %d roamrssi %d\n", __func__, curRssi, roamRssi);
  	}
  	/*
  	 * Check if a new ap should be used and switch.
  	 * XXX deauth current ap
  	 */
  	if (curRate < roamRate || curRssi < roamRssi) {
  		if (time_after(ticks, ic->ic_lastscan + vap->iv_scanvalid)) {
  			/*
  			 * Scan cache contents are too old; force a scan now
  			 * if possible so we have current state to make a
  			 * decision with.  We don't kick off a bg scan if
  			 * we're using dynamic turbo and boosted or if the
  			 * channel is busy.
  			 * XXX force immediate switch on scan complete
  			 */
  			if (!IEEE80211_IS_CHAN_DTURBO(ic->ic_curchan) &&
  			    time_after(ticks, ic->ic_lastdata + vap->iv_bgscanidle))
  				ieee80211_bg_scan(vap, 0);
  			return;
  		}
  		se->base.se_rssi = curRssi;
  		selbs = select_bss(ss, vap, IEEE80211_MSG_ROAM);
  		if (selbs != NULL && selbs != se) {
  			struct ieee80211_channel *chan;
  
  			IEEE80211_DPRINTF(vap,
  			    IEEE80211_MSG_ROAM | IEEE80211_MSG_DEBUG,
  			    "%s: ROAM: curRate %u, roamRate %u, "
  			    "curRssi %d, roamRssi %d\n", __func__,
  			    curRate, roamRate, curRssi, roamRssi);
  
  			chan = selbs->base.se_chan;
  			if (selbs->se_flags & STA_DEMOTE11B)
  				chan = demote11b(vap, chan);
  			(void) ieee80211_sta_join(vap, chan, &selbs->base);
  		}
  	}
  }
  
  /*
   * Age entries in the scan cache.
   * XXX also do roaming since it's convenient
   */
  static void
  sta_age(struct ieee80211_scan_state *ss)
  {
  	struct ieee80211vap *vap = ss->ss_vap;
  
  	adhoc_age(ss);
  	/*
  	 * If rate control is enabled check periodically to see if
  	 * we should roam from our current connection to one that
  	 * might be better.  This only applies when we're operating
  	 * in sta mode and automatic roaming is set.
  	 * XXX defer if busy
  	 * XXX repeater station
  	 * XXX do when !bgscan?
  	 */
  	KASSERT(vap->iv_opmode == IEEE80211_M_STA,
  		("wrong mode %u", vap->iv_opmode));
  	if (vap->iv_roaming == IEEE80211_ROAMING_AUTO &&
  	    (vap->iv_ic->ic_flags & IEEE80211_F_BGSCAN) &&
  	    vap->iv_state >= IEEE80211_S_RUN)
  		/* XXX vap is implicit */
  		sta_roam_check(ss, vap);
  }
  
  /*
   * Iterate over the entries in the scan cache, invoking
   * the callback function on each one.
   */
  static void
  sta_iterate(struct ieee80211_scan_state *ss, 
  	ieee80211_scan_iter_func *f, void *arg)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se;
  	u_int gen;
  
  	lockmgr(&st->st_scanlock, LK_EXCLUSIVE);
  	gen = st->st_scaniter++;
  restart:
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	TAILQ_FOREACH(se, &st->st_entry, se_list) {
  		if (se->se_scangen != gen) {
  			se->se_scangen = gen;
  			/* update public state */
  			se->base.se_age = ticks - se->se_lastupdate;
  			lockmgr(&st->st_lock, LK_RELEASE);
  			(*f)(arg, &se->base);
  			goto restart;
  		}
  	}
  	lockmgr(&st->st_lock, LK_RELEASE);
  
  	lockmgr(&st->st_scanlock, LK_RELEASE);
  }
  
  static void
  sta_assoc_fail(struct ieee80211_scan_state *ss,
  	const uint8_t macaddr[IEEE80211_ADDR_LEN], int reason)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se;
  
  	se = sta_lookup(st, macaddr);
  	if (se != NULL) {
  		se->se_fails++;
  		se->se_lastfail = ticks;
  		IEEE80211_NOTE_MAC(ss->ss_vap, IEEE80211_MSG_SCAN,
  		    macaddr, "%s: reason %u fails %u",
  		    __func__, reason, se->se_fails);
  	}
  }
  
  static void
  sta_assoc_success(struct ieee80211_scan_state *ss,
  	const uint8_t macaddr[IEEE80211_ADDR_LEN])
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se;
  
  	se = sta_lookup(st, macaddr);
  	if (se != NULL) {
  #if 0
  		se->se_fails = 0;
  		IEEE80211_NOTE_MAC(ss->ss_vap, IEEE80211_MSG_SCAN,
  		    macaddr, "%s: fails %u",
  		    __func__, se->se_fails);
  #endif
  		se->se_lastassoc = ticks;
  	}
  }
  
  static const struct ieee80211_scanner sta_default = {
  	.scan_name		= "default",
  	.scan_attach		= sta_attach,
  	.scan_detach		= sta_detach,
  	.scan_start		= sta_start,
  	.scan_restart		= sta_restart,
  	.scan_cancel		= sta_cancel,
  	.scan_end		= sta_pick_bss,
  	.scan_flush		= sta_flush,
  	.scan_add		= sta_add,
  	.scan_age		= sta_age,
  	.scan_iterate		= sta_iterate,
  	.scan_assoc_fail	= sta_assoc_fail,
  	.scan_assoc_success	= sta_assoc_success,
  };
  IEEE80211_SCANNER_ALG(sta, IEEE80211_M_STA, sta_default);
  
  /*
   * Adhoc mode-specific support.
   */
  
  static const uint16_t adhocWorld[] =		/* 36, 40, 44, 48 */
  { 5180, 5200, 5220, 5240 };
  static const uint16_t adhocFcc3[] =		/* 36, 40, 44, 48 145, 149, 153, 157, 161, 165 */
  { 5180, 5200, 5220, 5240, 5725, 5745, 5765, 5785, 5805, 5825 };
  static const uint16_t adhocMkk[] =		/* 34, 38, 42, 46 */
  { 5170, 5190, 5210, 5230 };
  static const uint16_t adhoc11b[] =		/* 10, 11 */
  { 2457, 2462 };
  
  static const struct scanlist adhocScanTable[] = {
  	{ IEEE80211_MODE_11B,   	X(adhoc11b) },
  	{ IEEE80211_MODE_11A,   	X(adhocWorld) },
  	{ IEEE80211_MODE_11A,   	X(adhocFcc3) },
  	{ IEEE80211_MODE_11B,   	X(adhocMkk) },
  	{ .list = NULL }
  };
  #undef X
  
  /*
   * Start an adhoc-mode scan by populating the channel list.
   */
  static int
  adhoc_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  	
  	makescanlist(ss, vap, adhocScanTable);
  
  	if (ss->ss_mindwell == 0)
  		ss->ss_mindwell = msecs_to_ticks(200);	/* 200ms */
  	if (ss->ss_maxdwell == 0)
  		ss->ss_maxdwell = msecs_to_ticks(200);	/* 200ms */
  
  	st->st_scangen++;
  	st->st_newscan = 1;
  
  	return 0;
  }
  
  /*
   * Select a channel to start an adhoc network on.
   * The channel list was populated with appropriate
   * channels so select one that looks least occupied.
   */
  static struct ieee80211_channel *
  adhoc_pick_channel(struct ieee80211_scan_state *ss, int flags)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se;
  	struct ieee80211_channel *c, *bestchan;
  	int i, bestrssi, maxrssi;
  
  	bestchan = NULL;
  	bestrssi = -1;
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	for (i = 0; i < ss->ss_last; i++) {
  		c = ss->ss_chans[i];
  		/* never consider a channel with radar */
  		if (IEEE80211_IS_CHAN_RADAR(c))
  			continue;
  		/* skip channels disallowed by regulatory settings */
  		if (IEEE80211_IS_CHAN_NOADHOC(c))
  			continue;
  		/* check channel attributes for band compatibility */
  		if (flags != 0 && (c->ic_flags & flags) != flags)
  			continue;
  		maxrssi = 0;
  		TAILQ_FOREACH(se, &st->st_entry, se_list) {
  			if (se->base.se_chan != c)
  				continue;
  			if (se->base.se_rssi > maxrssi)
  				maxrssi = se->base.se_rssi;
  		}
  		if (bestchan == NULL || maxrssi < bestrssi)
  			bestchan = c;
  	}
  	lockmgr(&st->st_lock, LK_RELEASE);
  
  	return bestchan;
  }
  
  /*
   * Pick an ibss network to join or find a channel
   * to use to start an ibss network.
   */
  static int
  adhoc_pick_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *selbs;
  	struct ieee80211_channel *chan;
  
  	KASSERT(vap->iv_opmode == IEEE80211_M_IBSS ||
  		vap->iv_opmode == IEEE80211_M_AHDEMO ||
  		vap->iv_opmode == IEEE80211_M_MBSS,
  		("wrong opmode %u", vap->iv_opmode));
  
  	if (st->st_newscan) {
  		sta_update_notseen(st);
  		st->st_newscan = 0;
  	}
  	if (ss->ss_flags & IEEE80211_SCAN_NOPICK) {
  		/*
  		 * Manual/background scan, don't select+join the
  		 * bss, just return.  The scanning framework will
  		 * handle notification that this has completed.
  		 */
  		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
  		return 1;
  	}
  	/*
  	 * Automatic sequencing; look for a candidate and
  	 * if found join the network.
  	 */
  	/* NB: unlocked read should be ok */
  	if (TAILQ_FIRST(&st->st_entry) == NULL) {
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
  			"%s: no scan candidate\n", __func__);
  		if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  			return 0;
  notfound:
  		/* NB: never auto-start a tdma network for slot !0 */
  #ifdef IEEE80211_SUPPORT_TDMA
  		if (vap->iv_des_nssid &&
  		    ((vap->iv_caps & IEEE80211_C_TDMA) == 0 ||
  		     ieee80211_tdma_getslot(vap) == 0)) {
  #else
  		if (vap->iv_des_nssid) {
  #endif
  			/*
  			 * No existing adhoc network to join and we have
  			 * an ssid; start one up.  If no channel was
  			 * specified, try to select a channel.
  			 */
  			if (vap->iv_des_chan == IEEE80211_CHAN_ANYC ||
  			    IEEE80211_IS_CHAN_RADAR(vap->iv_des_chan)) {
  				struct ieee80211com *ic = vap->iv_ic;
  
  				chan = adhoc_pick_channel(ss, 0);
  				if (chan != NULL)
  					chan = ieee80211_ht_adjust_channel(ic,
  					    chan, vap->iv_flags_ht);
  			} else
  				chan = vap->iv_des_chan;
  			if (chan != NULL) {
  				ieee80211_create_ibss(vap, chan);
  				return 1;
  			}
  		}
  		/*
  		 * If nothing suitable was found decrement
  		 * the failure counts so entries will be
  		 * reconsidered the next time around.  We
  		 * really want to do this only for sta's
  		 * where we've previously had some success.
  		 */
  		sta_dec_fails(st);
  		st->st_newscan = 1;
  		return 0;			/* restart scan */
  	}
  	selbs = select_bss(ss, vap, IEEE80211_MSG_SCAN);
  	if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  		return (selbs != NULL);
  	if (selbs == NULL)
  		goto notfound;
  	chan = selbs->base.se_chan;
  	if (selbs->se_flags & STA_DEMOTE11B)
  		chan = demote11b(vap, chan);
  	if (!ieee80211_sta_join(vap, chan, &selbs->base))
  		goto notfound;
  	return 1;				/* terminate scan */
  }
  
  /*
   * Age entries in the scan cache.
   */
  static void
  adhoc_age(struct ieee80211_scan_state *ss)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct sta_entry *se, *next;
  
  	lockmgr(&st->st_lock, LK_EXCLUSIVE);
  	TAILQ_FOREACH_MUTABLE(se, &st->st_entry, se_list, next) {
  		if (se->se_notseen > STA_PURGE_SCANS) {
  			TAILQ_REMOVE(&st->st_entry, se, se_list);
  			LIST_REMOVE(se, se_hash);
  			ieee80211_ies_cleanup(&se->base.se_ies);
  			kfree(se, M_80211_SCAN);
  		}
  	}
  	lockmgr(&st->st_lock, LK_RELEASE);
  }
  
  static const struct ieee80211_scanner adhoc_default = {
  	.scan_name		= "default",
  	.scan_attach		= sta_attach,
  	.scan_detach		= sta_detach,
  	.scan_start		= adhoc_start,
  	.scan_restart		= sta_restart,
  	.scan_cancel		= sta_cancel,
  	.scan_end		= adhoc_pick_bss,
  	.scan_flush		= sta_flush,
  	.scan_pickchan		= adhoc_pick_channel,
  	.scan_add		= sta_add,
  	.scan_age		= adhoc_age,
  	.scan_iterate		= sta_iterate,
  	.scan_assoc_fail	= sta_assoc_fail,
  	.scan_assoc_success	= sta_assoc_success,
  };
  IEEE80211_SCANNER_ALG(ibss, IEEE80211_M_IBSS, adhoc_default);
  IEEE80211_SCANNER_ALG(ahdemo, IEEE80211_M_AHDEMO, adhoc_default);
  
  static void
  ap_force_promisc(struct ieee80211com *ic)
  {
  	struct ifnet *ifp = ic->ic_ifp;
  
  	/* set interface into promiscuous mode */
  	ifp->if_flags |= IFF_PROMISC;
  	ieee80211_runtask(ic, &ic->ic_promisc_task);
  }
  
  static void
  ap_reset_promisc(struct ieee80211com *ic)
  {
  	ieee80211_syncifflag_locked(ic, IFF_PROMISC);
  }
  
  static int
  ap_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  
  	makescanlist(ss, vap, staScanTable);
  
  	if (ss->ss_mindwell == 0)
  		ss->ss_mindwell = msecs_to_ticks(200);	/* 200ms */
  	if (ss->ss_maxdwell == 0)
  		ss->ss_maxdwell = msecs_to_ticks(200);	/* 200ms */
  
  	st->st_scangen++;
  	st->st_newscan = 1;
  
  	ap_force_promisc(vap->iv_ic);
  	return 0;
  }
  
  /*
   * Cancel an ongoing scan.
   */
  static int
  ap_cancel(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	ap_reset_promisc(vap->iv_ic);
  	return 0;
  }
  
  /*
   * Pick a quiet channel to use for ap operation.
   */
  static struct ieee80211_channel *
  ap_pick_channel(struct ieee80211_scan_state *ss, int flags)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct ieee80211_channel *bestchan = NULL;
  	int i;
  
  	/* XXX select channel more intelligently, e.g. channel spread, power */
  	/* NB: use scan list order to preserve channel preference */
  	for (i = 0; i < ss->ss_last; i++) {
  		struct ieee80211_channel *chan = ss->ss_chans[i];
  		/*
  		 * If the channel is unoccupied the max rssi
  		 * should be zero; just take it.  Otherwise
  		 * track the channel with the lowest rssi and
  		 * use that when all channels appear occupied.
  		 */
  		if (IEEE80211_IS_CHAN_RADAR(chan))
  			continue;
  		if (IEEE80211_IS_CHAN_NOHOSTAP(chan))
  			continue;
  		/* check channel attributes for band compatibility */
  		if (flags != 0 && (chan->ic_flags & flags) != flags)
  			continue;
  		KASSERT(sizeof(chan->ic_ieee) == 1, ("ic_chan size"));
  		/* XXX channel have interference */
  		if (st->st_maxrssi[chan->ic_ieee] == 0) {
  			/* XXX use other considerations */
  			return chan;
  		}
  		if (bestchan == NULL ||
  		    st->st_maxrssi[chan->ic_ieee] < st->st_maxrssi[bestchan->ic_ieee])
  			bestchan = chan;
  	}
  	return bestchan;
  }
  
  /*
   * Pick a quiet channel to use for ap operation.
   */
  static int
  ap_end(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct ieee80211com *ic = vap->iv_ic;
  	struct ieee80211_channel *bestchan;
  
  	KASSERT(vap->iv_opmode == IEEE80211_M_HOSTAP,
  		("wrong opmode %u", vap->iv_opmode));
  	bestchan = ap_pick_channel(ss, 0);
  	if (bestchan == NULL) {
  		/* no suitable channel, should not happen */
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
  		    "%s: no suitable channel! (should not happen)\n", __func__);
  		/* XXX print something? */
  		return 0;			/* restart scan */
  	}
  	/*
  	 * If this is a dynamic turbo channel, start with the unboosted one.
  	 */
  	if (IEEE80211_IS_CHAN_TURBO(bestchan)) {
  		bestchan = ieee80211_find_channel(ic, bestchan->ic_freq,
  			bestchan->ic_flags & ~IEEE80211_CHAN_TURBO);
  		if (bestchan == NULL) {
  			/* should never happen ?? */
  			return 0;
  		}
  	}
  	ap_reset_promisc(ic);
  	if (ss->ss_flags & (IEEE80211_SCAN_NOPICK | IEEE80211_SCAN_NOJOIN)) {
  		/*
  		 * Manual/background scan, don't select+join the
  		 * bss, just return.  The scanning framework will
  		 * handle notification that this has completed.
  		 */
  		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
  		return 1;
  	}
  	ieee80211_create_ibss(vap,
  	    ieee80211_ht_adjust_channel(ic, bestchan, vap->iv_flags_ht));
  	return 1;
  }
  
  static const struct ieee80211_scanner ap_default = {
  	.scan_name		= "default",
  	.scan_attach		= sta_attach,
  	.scan_detach		= sta_detach,
  	.scan_start		= ap_start,
  	.scan_restart		= sta_restart,
  	.scan_cancel		= ap_cancel,
  	.scan_end		= ap_end,
  	.scan_flush		= sta_flush,
  	.scan_pickchan		= ap_pick_channel,
  	.scan_add		= sta_add,
  	.scan_age		= adhoc_age,
  	.scan_iterate		= sta_iterate,
  	.scan_assoc_success	= sta_assoc_success,
  	.scan_assoc_fail	= sta_assoc_fail,
  };
  IEEE80211_SCANNER_ALG(ap, IEEE80211_M_HOSTAP, ap_default);
  
  #ifdef IEEE80211_SUPPORT_MESH
  /*
   * Pick an mbss network to join or find a channel
   * to use to start an mbss network.
   */
  static int
  mesh_pick_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
  {
  	struct sta_table *st = ss->ss_priv;
  	struct ieee80211_mesh_state *ms = vap->iv_mesh;
  	struct sta_entry *selbs;
  	struct ieee80211_channel *chan;
  
  	KASSERT(vap->iv_opmode == IEEE80211_M_MBSS,
  		("wrong opmode %u", vap->iv_opmode));
  
  	if (st->st_newscan) {
  		sta_update_notseen(st);
  		st->st_newscan = 0;
  	}
  	if (ss->ss_flags & IEEE80211_SCAN_NOPICK) {
  		/*
  		 * Manual/background scan, don't select+join the
  		 * bss, just return.  The scanning framework will
  		 * handle notification that this has completed.
  		 */
  		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
  		return 1;
  	}
  	/*
  	 * Automatic sequencing; look for a candidate and
  	 * if found join the network.
  	 */
  	/* NB: unlocked read should be ok */
  	if (TAILQ_FIRST(&st->st_entry) == NULL) {
  		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
  			"%s: no scan candidate\n", __func__);
  		if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  			return 0;
  notfound:
  		if (ms->ms_idlen != 0) {
  			/*
  			 * No existing mbss network to join and we have
  			 * a meshid; start one up.  If no channel was
  			 * specified, try to select a channel.
  			 */
  			if (vap->iv_des_chan == IEEE80211_CHAN_ANYC ||
  			    IEEE80211_IS_CHAN_RADAR(vap->iv_des_chan)) {
  				struct ieee80211com *ic = vap->iv_ic;
  
  				chan = adhoc_pick_channel(ss, 0);
  				if (chan != NULL)
  					chan = ieee80211_ht_adjust_channel(ic,
  					    chan, vap->iv_flags_ht);
  			} else
  				chan = vap->iv_des_chan;
  			if (chan != NULL) {
  				ieee80211_create_ibss(vap, chan);
  				return 1;
  			}
  		}
  		/*
  		 * If nothing suitable was found decrement
  		 * the failure counts so entries will be
  		 * reconsidered the next time around.  We
  		 * really want to do this only for sta's
  		 * where we've previously had some success.
  		 */
  		sta_dec_fails(st);
  		st->st_newscan = 1;
  		return 0;			/* restart scan */
  	}
  	selbs = select_bss(ss, vap, IEEE80211_MSG_SCAN);
  	if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
  		return (selbs != NULL);
  	if (selbs == NULL)
  		goto notfound;
  	chan = selbs->base.se_chan;
  	if (selbs->se_flags & STA_DEMOTE11B)
  		chan = demote11b(vap, chan);
  	if (!ieee80211_sta_join(vap, chan, &selbs->base))
  		goto notfound;
  	return 1;				/* terminate scan */
  }
  
  static const struct ieee80211_scanner mesh_default = {
  	.scan_name		= "default",
  	.scan_attach		= sta_attach,
  	.scan_detach		= sta_detach,
  	.scan_start		= adhoc_start,
  	.scan_restart		= sta_restart,
  	.scan_cancel		= sta_cancel,
  	.scan_end		= mesh_pick_bss,
  	.scan_flush		= sta_flush,
  	.scan_pickchan		= adhoc_pick_channel,
  	.scan_add		= sta_add,
  	.scan_age		= adhoc_age,
  	.scan_iterate		= sta_iterate,
  	.scan_assoc_fail	= sta_assoc_fail,
  	.scan_assoc_success	= sta_assoc_success,
  };
  IEEE80211_SCANNER_ALG(mesh, IEEE80211_M_MBSS, mesh_default);
  #endif /* IEEE80211_SUPPORT_MESH */
  