madwifi/net80211/ieee80211_scan_ap.c

/*-
 * Copyright (c) 2002-2005 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * 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.
 *
 * $Id$
 */
#ifndef EXPORT_SYMTAB
#define	EXPORT_SYMTAB
#endif

/*
 * IEEE 802.11 ap scanning support.
 */
#ifndef AUTOCONF_INCLUDED
#include <linux/config.h>
#endif
#include <linux/version.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/init.h>
#include <linux/delay.h>

#include "if_media.h"

#include <net80211/ieee80211_var.h>

#define	AP_PURGE_SCANS	2		/* age for purging entries (scans) */
#define RSSI_LPF_LEN	10
#define	RSSI_EP_MULTIPLIER	(1<<7)	/* pow2 to optimize out * and / */
#define RSSI_IN(x)		((x) * RSSI_EP_MULTIPLIER)
#define LPF_RSSI(x, y, len)	(((x) * ((len) - 1) + (y)) / (len))
#define RSSI_LPF(x, y) do {						\
	if ((y) >= -20)							\
		x = LPF_RSSI((x), RSSI_IN((y)), RSSI_LPF_LEN);			\
} while (0)
#define	EP_RND(x, mul) \
	((((x)%(mul)) >= ((mul)/2)) ? howmany(x, mul) : (x)/(mul))
#define	RSSI_GET(x)	EP_RND(x, RSSI_EP_MULTIPLIER)
#define	AP_HASHSIZE	32
/* simple hash is enough for variation of macaddr */
#define	AP_HASH(addr)	\
	(((const u_int8_t *)(addr))[IEEE80211_ADDR_LEN - 1] % AP_HASHSIZE)
#define	SCAN_AP_LOCK_INIT(_st, _name)					\
	spin_lock_init(&(_st)->as_lock)
#define	SCAN_AP_LOCK_DESTROY(_st)
#define	SCAN_AP_LOCK_IRQ(_st) do {					\
	unsigned long __stlockflags;					\
	spin_lock_irqsave(&(_st)->as_lock, __stlockflags);
#define	SCAN_AP_UNLOCK_IRQ(_st)						\
	spin_unlock_irqrestore(&(_st)->as_lock, __stlockflags);		\
} while (0)
#define	SCAN_AP_UNLOCK_IRQ_EARLY(_st)					\
	spin_unlock_irqrestore(&(_st)->as_lock, __stlockflags);

#define	SCAN_AP_GEN_LOCK_INIT(_st, _name)				\
	spin_lock_init(&(_st)->as_scanlock)
#define	SCAN_AP_GEN_LOCK_DESTROY(_st)
#define	SCAN_AP_GEN_LOCK(_st)		spin_lock(&(_st)->as_scanlock);
#define	SCAN_AP_GEN_UNLOCK(_st)	spin_unlock(&(_st)->as_scanlock);

struct scan_entry {
	struct ieee80211_scan_entry base;
	TAILQ_ENTRY(scan_entry) se_list;
	LIST_ENTRY(scan_entry) se_hash;
	u_int8_t	se_seen;		/* seen during current scan */
	u_int8_t	se_notseen;		/* not seen in previous scans */
	u_int32_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# */
};

struct ap_state {
	unsigned int as_vap_desired_mode;       /* Used for channel selection, vap->iv_des_mode */
	unsigned int as_required_mode;          /* Used for channel selection, filtered version of as_vap_desired_mode */
	int as_maxrssi[IEEE80211_CHAN_MAX]; 	/* Used for channel selection */

	/* These fields are just for scan caching for returning responses to
	 * wireless extensions.  i.e. show peers, APs, etc. */
	spinlock_t as_lock;			/* on scan table */
	int as_newscan;				/* trigger for updating seen/not-seen for aging */
	TAILQ_HEAD(, scan_entry) as_entry;	/* all entries */
	ATH_LIST_HEAD(, scan_entry) as_hash[AP_HASHSIZE];
	spinlock_t as_scanlock;			/* on as_scangen */
	u_int as_scangen;			/* gen# for iterator */

	struct IEEE80211_TQ_STRUCT as_actiontq;	/* tasklet for "action" */
	struct ieee80211_scan_entry as_selbss;	/* selected bss for action tasklet */
	int (*as_action)(struct ieee80211vap *, const struct ieee80211_scan_entry *);
};

static int ap_flush(struct ieee80211_scan_state *);
static void action_tasklet(IEEE80211_TQUEUE_ARG);
static struct ieee80211_channel *find11gchannel(struct ieee80211com *ic, int i, int freq);

static const u_int chanflags[] = {
	IEEE80211_CHAN_B,	/* IEEE80211_MODE_AUTO */
	IEEE80211_CHAN_A,	/* IEEE80211_MODE_11A */
	IEEE80211_CHAN_B,	/* IEEE80211_MODE_11B */
	IEEE80211_CHAN_PUREG,	/* IEEE80211_MODE_11G */
	IEEE80211_CHAN_FHSS,	/* IEEE80211_MODE_FH */
	IEEE80211_CHAN_A,	/* IEEE80211_MODE_TURBO_A */ /* for turbo mode look for AP in normal channel */
	IEEE80211_CHAN_PUREG,	/* IEEE80211_MODE_TURBO_G */
	IEEE80211_CHAN_ST,	/* IEEE80211_MODE_TURBO_STATIC_A */
};

static const u_int16_t rcl1[] =		/* 8 FCC channel: 52, 56, 60, 64, 36, 40, 44, 48 */
{ 5260, 5280, 5300, 5320, 5180, 5200, 5220, 5240 };
static const u_int16_t rcl2[] =		/* 4 MKK channels: 34, 38, 42, 46 */
{ 5170, 5190, 5210, 5230 };
static const u_int16_t rcl3[] =		/* 2.4Ghz ch: 1,6,11,7,13 */
{ 2412, 2437, 2462, 2442, 2472 };
static const u_int16_t rcl4[] =		/* 5 FCC channel: 149, 153, 161, 165 */
{ 5745, 5765, 5785, 5805, 5825 };
static const u_int16_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 u_int16_t rcl8[] =		/* 2.4Ghz ch: 2,3,4,5,8,9,10,12 */
{ 2417, 2422, 2427, 2432, 2447, 2452, 2457, 2467 };
static const u_int16_t rcl9[] =		/* 2.4Ghz ch: 14 */
{ 2484 };
static const u_int16_t rcl10[] =	/* Added Korean channels 2312-2372 */
{ 2312, 2317, 2322, 2327, 2332, 2337, 2342, 2347, 2352, 2357, 2362, 2367, 2372 };
static const u_int16_t rcl11[] =	/* Added Japan channels in 4.9/5.0 spectrum */
{ 5040, 5060, 5080, 4920, 4940, 4960, 4980 };
#ifdef ATH_TURBO_SCAN
static const u_int16_t rcl5[] =		/* 3 static turbo channels */
{ 5210, 5250, 5290 };
static const u_int16_t rcl6[] =		/* 2 static turbo channels */
{ 5760, 5800 };
static const u_int16_t rcl6x[] =		/* 4 FCC3 turbo channels */
{ 5540, 5580, 5620, 5660 };
static const u_int16_t rcl12[] =		/* 2.4Ghz Turbo channel 6 */
{ 2437 };
static const u_int16_t rcl13[] =		/* dynamic Turbo channels */
{ 5200, 5240, 5280, 5765, 5805 };
#endif /* ATH_TURBO_SCAN */

struct scanlist {
	u_int16_t	mode;
	u_int16_t	count;
	const u_int16_t	*list;
};

#define	IEEE80211_MODE_TURBO_STATIC_A	IEEE80211_MODE_MAX
#define	X(a)	.count = sizeof(a)/sizeof(a[0]), .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_TURBO_STATIC_A,	X(rcl5) },
	{ IEEE80211_MODE_TURBO_STATIC_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 }
};

#undef X
/* This function must be invoked with locks acquired */
static void
add_channels(struct ieee80211com *ic,
	struct ieee80211_scan_state *ss,
	enum ieee80211_phymode mode, const u_int16_t freq[], int nfreq)
{
	struct ieee80211_channel *c, *cg;
	u_int modeflags;
	int i;

	KASSERT(mode < ARRAY_SIZE(chanflags), ("Unexpected mode %u", mode));
	modeflags = chanflags[mode];
	for (i = 0; i < nfreq; i++) {
		c = ieee80211_find_channel(ic, freq[i], modeflags);
		if (c == NULL || isclr(ic->ic_chan_active, c->ic_ieee))
			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;
		}
		if (ss->ss_last >= IEEE80211_SCAN_MAX)
			break;
		ss->ss_chans[ss->ss_last++] = c;
	}
}

/* This function must be invoked with locks acquired */
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;
}

/*
 * Attach prior to any scanning work.
 */
static int
ap_attach(struct ieee80211_scan_state *ss)
{
	struct ap_state *as;

	_MOD_INC_USE(THIS_MODULE, return 0);

	MALLOC(as, struct ap_state *, sizeof(struct ap_state),
		M_80211_SCAN, M_NOWAIT | M_ZERO);
	if (as == NULL)
		return 0;
	SCAN_AP_LOCK_INIT(as, "scan_ap");
	SCAN_AP_GEN_LOCK_INIT(as, "scan_ap_gen");
	TAILQ_INIT(&as->as_entry);
	IEEE80211_INIT_TQUEUE(&as->as_actiontq, action_tasklet, ss);
	ss->ss_priv = as;
	ap_flush(ss);
	return 1;
}

/*
 * Cleanup any private state.
 */
static int
ap_detach(struct ieee80211_scan_state *ss)
{
	struct ap_state *as = ss->ss_priv;

	if (as != NULL) {
		ap_flush(ss);
		IEEE80211_CANCEL_TQUEUE(&as->as_actiontq);
		FREE(as, M_80211_SCAN);
	}

	_MOD_DEC_USE(THIS_MODULE);
	return 1;
}

/*
 * Flush all per-scan state.
 */
static int
ap_flush(struct ieee80211_scan_state *ss)
{
	struct ap_state *as = ss->ss_priv;
	struct scan_entry *se, *next;

	SCAN_AP_LOCK_IRQ(as);
	memset(as->as_maxrssi, 0, sizeof(as->as_maxrssi));
	TAILQ_FOREACH_SAFE(se, &as->as_entry, se_list, next) {
		TAILQ_REMOVE(&as->as_entry, se, se_list);
		LIST_REMOVE(se, se_hash);
		FREE(se, M_80211_SCAN);
	}
	ss->ss_last = 0;		/* ensure no channel will be picked */
	SCAN_AP_UNLOCK_IRQ(as);
	return 0;
}

/* This function must be invoked with locks acquired */
static void
saveie(u_int8_t **iep, const u_int8_t *ie)
{
	if (ie == NULL)
		*iep = NULL;
	else
		ieee80211_saveie(iep, ie);
}

/* This function must be invoked with locks acquired */
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_ANYG(c))
			return c;
	}
	for (j = 0; j < i; j++) {
		c = &ic->ic_channels[j];
		if (c->ic_freq == freq && IEEE80211_IS_CHAN_ANYG(c))
			return c;
	}
	return NULL;
}

/*
 * Start an ap scan by populating the channel list.
 */
static int
ap_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
	struct ap_state *as 	    = ss->ss_priv;
	struct ieee80211com *ic     = NULL;
	const struct scanlist *sl   = NULL;
	struct ieee80211_channel *c = NULL;
	int i;
	unsigned int mode = 0;

	SCAN_AP_LOCK_IRQ(as);
	ic = vap->iv_ic;
	/* Determine mode flags to match, or leave zero for auto mode */
	as->as_vap_desired_mode = vap->iv_des_mode;
	as->as_required_mode    = 0;
	if (as->as_vap_desired_mode != IEEE80211_MODE_AUTO) {
		as->as_required_mode = chanflags[as->as_vap_desired_mode];
		if (vap->iv_ath_cap & IEEE80211_ATHC_TURBOP && 
		    as->as_required_mode != IEEE80211_CHAN_ST) {
			/* Fixup for dynamic turbo flags */
			if (as->as_vap_desired_mode == IEEE80211_MODE_11G)
				as->as_required_mode = IEEE80211_CHAN_108G;
			else
				as->as_required_mode = IEEE80211_CHAN_108A;
		}
	}

	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 (sl = staScanTable; sl->list != NULL; sl++) {
		mode = sl->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 (as->as_vap_desired_mode &&
		    as->as_vap_desired_mode != mode && 
		    as->as_vap_desired_mode == IEEE80211_MODE_11G && 
		    mode == IEEE80211_MODE_11B)
			mode = IEEE80211_MODE_11G;
		/* If we are in "AUTO" mode, upgrade the mode to auto. 
		 * This lets add_channels upgrade an 11b channel to 
		 * 11g if available. */
		if (!as->as_vap_desired_mode && mode == IEEE80211_MODE_11B)
			mode = IEEE80211_MODE_AUTO;
		/* Add the list of the channels; any that are not
		 * in the master channel list will be discarded. */
		add_channels(ic, ss, mode, sl->list, sl->count);
	}

	/*
	 * Add the channels from the ic (from HAL) that are not present
	 * in the staScanTable, assuming they pass the sanity checks...
	 */
	for (i = 0; i < ic->ic_nchans; i++) {
		c = &ic->ic_channels[i];
		/* XR is not supported on turbo channels */
		if (IEEE80211_IS_CHAN_TURBO(c) && vap->iv_flags & IEEE80211_F_XR)
			continue;

		/* Dynamic channels are scanned in base mode */
		if (!as->as_required_mode && !IEEE80211_IS_CHAN_ST(c))
			continue;

		/* Use any 11g channel instead of 11b one. */
		if (vap->iv_des_mode == IEEE80211_MODE_AUTO && 
		    IEEE80211_IS_CHAN_B(c) &&
		    find11gchannel(ic, i, c->ic_freq))
			continue;

		/* Do not add channels already put into the scan list by the
		 * scan table - these have already been filtered by mode
		 * and for whether they are in the active channel list. */
		if (checktable(staScanTable, c))
			continue;

		/* Make sure the channel is active */
		if (c == NULL || isclr(ic->ic_chan_active, c->ic_ieee))
			continue;

		/* Don't overrun */
		if (ss->ss_last >= IEEE80211_SCAN_MAX)
			break;

		ss->ss_chans[ss->ss_last++] = c;
	}
	ss->ss_next = 0;
	/* XXX tunables */
	ss->ss_mindwell = msecs_to_jiffies(200);	/* 200ms */
	ss->ss_maxdwell = msecs_to_jiffies(300);	/* 300ms */

#ifdef IEEE80211_DEBUG
	if (ieee80211_msg_scan(vap)) {
		printf("%s: scan set ", vap->iv_dev->name);
		ieee80211_scan_dump_channels(ss);
		printf(" dwell min %ld max %ld\n",
			ss->ss_mindwell, ss->ss_maxdwell);
	}
#endif /* IEEE80211_DEBUG */

	as->as_newscan = 1;
	SCAN_AP_UNLOCK_IRQ(as);
	return 0;
}

/*
 * Restart a bg scan.
 */
static int
ap_restart(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
	struct ap_state *as = ss->ss_priv;
	as->as_newscan = 1;
	return 0;
}

/*
 * Cancel an ongoing scan.
 */
static int
ap_cancel(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
	struct ap_state *as = ss->ss_priv;
	IEEE80211_CANCEL_TQUEUE(&as->as_actiontq);
	return 0;
}

/*
 * Record max rssi on channel.
 */
static int
ap_add(struct ieee80211_scan_state *ss, const struct ieee80211_scanparams *sp,
	const struct ieee80211_frame *wh, int subtype, int rssi, u_int64_t rtsf)
{
	struct ap_state *as              = ss->ss_priv;
	const u_int8_t *macaddr          = wh->i_addr2;
	struct ieee80211vap *vap         = NULL;
	struct ieee80211com *ic          = NULL;
	struct scan_entry *se            = NULL;
	struct ieee80211_scan_entry *ise = NULL;
	int hash;
	int chan = 0;

	/* This section provides scan results to wireless extensions */
	SCAN_AP_LOCK_IRQ(as);
	/* This is the only information used for channel selection by AP */
	if (rssi > as->as_maxrssi[chan])
		as->as_maxrssi[chan] = rssi;
	vap = ss->ss_vap;
	ic = vap->iv_ic;
	hash = AP_HASH(macaddr);
	chan = ieee80211_chan2ieee(ic, ic->ic_curchan);
	LIST_FOREACH(se, &as->as_hash[hash], se_hash)
		if (IEEE80211_ADDR_EQ(se->base.se_macaddr, macaddr) &&
		    sp->ssid[1] == se->base.se_ssid[1] &&
		    !memcmp(se->base.se_ssid+2, sp->ssid+2, se->base.se_ssid[1]))
			goto found;

	MALLOC(se, struct scan_entry *, sizeof(struct scan_entry),
		M_80211_SCAN, M_NOWAIT | M_ZERO);
	if (se == NULL) {
		SCAN_AP_UNLOCK_IRQ_EARLY(as);
		return 0;
	}
	se->se_scangen = as->as_scangen-1;
	IEEE80211_ADDR_COPY(se->base.se_macaddr, macaddr);
	TAILQ_INSERT_TAIL(&as->as_entry, se, se_list);
	LIST_INSERT_HEAD(&as->as_hash[hash], se, se_hash);

found:
	ise = &se->base;

	/* XXX: AP beaconing multiple SSID w/ same BSSID */
	if ((sp->ssid[1] != 0) &&
	    ((subtype == IEEE80211_FC0_SUBTYPE_PROBE_RESP) || 
	     (ise->se_ssid[1] == 0)))
		memcpy(ise->se_ssid, sp->ssid, 2 + sp->ssid[1]);

	memcpy(ise->se_rates, sp->rates, 
		IEEE80211_SANITISE_RATESIZE(2 + sp->rates[1]));
	if (sp->xrates != NULL) {
		memcpy(ise->se_xrates, sp->xrates, 
				IEEE80211_SANITISE_RATESIZE(2 + sp->xrates[1]));
	} else
		ise->se_xrates[1] = 0;

	IEEE80211_ADDR_COPY(ise->se_bssid, wh->i_addr3);

	/* Record RSSI data using extended precision LPF filter.*/
	if (se->se_lastupdate == 0)			/* First sample */
		se->se_avgrssi = RSSI_IN(rssi);
	else					/* Avg. w/ previous samples */
		RSSI_LPF(se->se_avgrssi, rssi);
	se->base.se_rssi = RSSI_GET(se->se_avgrssi);
	ise->se_rtsf = rtsf;
	memcpy(ise->se_tstamp.data, sp->tstamp, sizeof(ise->se_tstamp));
	ise->se_intval = sp->bintval;
	ise->se_capinfo = sp->capinfo;
	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;
	}
	saveie(&ise->se_wme_ie, sp->wme);
	saveie(&ise->se_wpa_ie, sp->wpa);
	saveie(&ise->se_rsn_ie, sp->rsn);
	saveie(&ise->se_ath_ie, sp->ath);

	se->se_lastupdate = jiffies;		/* update time */
	se->se_seen = 1;
	se->se_notseen = 0;

	SCAN_AP_UNLOCK_IRQ(as);

	return 1;
}

/*
 * Pick a quiet channel to use for ap operation.
 */
static int
ap_end(struct ieee80211_scan_state *ss, struct ieee80211vap *vap,
		int (*action)(struct ieee80211vap *, 
			const struct ieee80211_scan_entry *), 
			u_int32_t flags)
{
	struct ap_state *as = ss->ss_priv;
	struct ieee80211com *ic = NULL;
	int res = 1;
	int i, chan, bestchan, bestchanix;

	SCAN_AP_LOCK_IRQ(as);

	KASSERT(vap->iv_opmode == IEEE80211_M_HOSTAP,
		("wrong opmode %u", vap->iv_opmode));

	ic = vap->iv_ic;
	/* XXX select channel more intelligently, e.g. channel spread, power */
	bestchan = -1;
	bestchanix = 0;		/* NB: silence compiler */
	/* NB: use scan list order to preserve channel preference */
	for (i = 0; i < ss->ss_last; 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.
		 */
		/*
		 * Check for channel interference, and if found,
		 * skip the channel.  We assume that all channels
		 * will be checked so atleast one can be found
		 * suitable and will change.  IF this changes,
		 * then we must know when we "have to" change
		 * channels for radar and move off.
		 */

		if (ss->ss_chans[i]->ic_flags & IEEE80211_CHAN_RADAR)
			continue;
		if (flags & IEEE80211_SCAN_KEEPMODE) {
			if (ic->ic_curchan != NULL) {
				if ((ss->ss_chans[i]->ic_flags & IEEE80211_CHAN_ALLTURBO) != (ic->ic_curchan->ic_flags & IEEE80211_CHAN_ALLTURBO))
					continue;
			}
		}

		chan = ieee80211_chan2ieee(ic, ss->ss_chans[i]);

		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: channel %u rssi %d bestchan %d bestchan rssi %d\n",
			__func__, chan, as->as_maxrssi[chan],
			bestchan, bestchan != -1 ? as->as_maxrssi[bestchan] : 0);

		if (as->as_maxrssi[chan] == 0) {
			bestchan = chan;
			bestchanix = i;
			/* XXX use other considerations */
			break;
		}
		if (bestchan == -1 ||
		    as->as_maxrssi[chan] < as->as_maxrssi[bestchan])
			bestchan = chan;
	}
	if (bestchan == -1) {
		if (ss->ss_last > 0) {
			/* no suitable channel, should not happen */
			IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
				"%s: no suitable channel! (should not happen)\n", __func__);
			/* XXX print something? */
		}
		res = 0; /* restart scan */
	} else {
		struct ieee80211_channel *c;
		struct ieee80211_scan_entry se;
		/* XXX: notify all VAPs? */
		/* if this is a dynamic turbo frequency , start with normal mode first */

		c = ss->ss_chans[bestchanix];
		if (IEEE80211_IS_CHAN_TURBO(c) && !IEEE80211_IS_CHAN_STURBO(c)) {
			if ((c = ieee80211_find_channel(ic, c->ic_freq,
				c->ic_flags & ~IEEE80211_CHAN_TURBO)) == NULL) {
				/* should never happen ?? */
				SCAN_AP_UNLOCK_IRQ_EARLY(as);
				return 0;
			}
		}
		memset(&se, 0, sizeof(se));
		se.se_chan = c;

		as->as_action = ss->ss_ops->scan_default;
		if (action)
			as->as_action = action;
		as->as_selbss = se;

		/* 
		 * Must defer action to avoid possible recursive call through 80211
		 * state machine, which would result in recursive locking.
		 */
		IEEE80211_SCHEDULE_TQUEUE(&as->as_actiontq);
		res = 1;
	}
	SCAN_AP_UNLOCK_IRQ(as);
	return res;
}

static void
ap_age(struct ieee80211_scan_state *ss)
{
	struct ap_state *as = ss->ss_priv;
	struct scan_entry *se, *next;

	SCAN_AP_LOCK_IRQ(as);
	TAILQ_FOREACH_SAFE(se, &as->as_entry, se_list, next) {
		if (se->se_notseen > AP_PURGE_SCANS) {
			TAILQ_REMOVE(&as->as_entry, se, se_list);
			LIST_REMOVE(se, se_hash);
			FREE(se, M_80211_SCAN);
		}
	}
	SCAN_AP_UNLOCK_IRQ(as);
}

static int
ap_iterate(struct ieee80211_scan_state *ss,
	ieee80211_scan_iter_func *f, void *arg)
{
	struct ap_state *as = ss->ss_priv;
	struct scan_entry *se;
	u_int gen;
	int res = 0;

	SCAN_AP_GEN_LOCK(as);
	gen = as->as_scangen++;
restart:
	SCAN_AP_LOCK_IRQ(as);
	TAILQ_FOREACH(se, &as->as_entry, se_list) {
		if (se->se_scangen != gen) {
			se->se_scangen = gen;
			/* update public state */
			se->base.se_age = jiffies - se->se_lastupdate;
			SCAN_AP_UNLOCK_IRQ_EARLY(as);

			res = (*f)(arg, &se->base);

			/* We probably ran out of buffer space. */
			if (res != 0)
				goto done;

			goto restart;
		}
	}

	SCAN_AP_UNLOCK_IRQ(as);

done:
	SCAN_AP_GEN_UNLOCK(as);

	return res;
}

static void
ap_assoc_success(struct ieee80211_scan_state *ss,
	const u_int8_t macaddr[IEEE80211_ADDR_LEN])
{
	/* should not be called */
}

static void
ap_assoc_fail(struct ieee80211_scan_state *ss,
	const u_int8_t macaddr[IEEE80211_ADDR_LEN], int reason)
{
	/* should not be called */
}

/*
 * Default action to execute when a scan entry is found for ap
 * mode.  Return 1 on success, 0 on failure
 */
static int
ap_default_action(struct ieee80211vap *vap,
	const struct ieee80211_scan_entry *se)
{
	ieee80211_create_ibss(vap, se->se_chan);

	return 1;
}

static void
action_tasklet(IEEE80211_TQUEUE_ARG data)
{
	struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *)data;
	struct ap_state *as = (struct ap_state *)ss->ss_priv;
	struct ieee80211vap *vap = ss->ss_vap;
	SCAN_AP_LOCK_IRQ(as);
	if (as->as_newscan) {
		struct scan_entry *se;
		TAILQ_FOREACH(se, &as->as_entry, se_list) {
			/*
			 * If seen then reset and don't bump the count;
			 * otherwise bump the ``not seen'' count.  Note
			 * that this ensures 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++;
		}
		as->as_newscan = 0;
	}
	SCAN_AP_UNLOCK_IRQ(as);

	(*ss->ss_ops->scan_default)(vap, &as->as_selbss);
}

/*
 * Module glue.
 */
MODULE_AUTHOR("Errno Consulting, Sam Leffler");
MODULE_DESCRIPTION("802.11 wireless support: default ap scanner");
#ifdef MODULE_LICENSE
MODULE_LICENSE("Dual BSD/GPL");
#endif

static const struct ieee80211_scanner ap_default = {
	.scan_name		= "default",
	.scan_attach		= ap_attach,
	.scan_detach		= ap_detach,
	.scan_start		= ap_start,
	.scan_restart		= ap_restart,
	.scan_cancel		= ap_cancel,
	.scan_end		= ap_end,
	.scan_flush		= ap_flush,
	.scan_add		= ap_add,
	.scan_age		= ap_age,
	.scan_iterate		= ap_iterate,
	.scan_assoc_success	= ap_assoc_success,
	.scan_assoc_fail	= ap_assoc_fail,
	.scan_default		= ap_default_action,
};


static int __init
init_scanner_ap(void)
{
	ieee80211_scanner_register(IEEE80211_M_HOSTAP, &ap_default);
	return 0;
}
module_init(init_scanner_ap);

static void __exit
exit_scanner_ap(void)
{
	ieee80211_scanner_unregister_all(&ap_default);
}
module_exit(exit_scanner_ap);