update madwifi

[linux-2.6/zen-sources.git] / drivers / net / wireless / madwifi / net80211 / ieee80211_scan_sta.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: ieee80211_scan_sta.c 3733 2008-06-19 02:34:23Z mentor $
 */
#ifndef EXPORT_SYMTAB
#define EXPORT_SYMTAB
#endif

/*
 * IEEE 802.11 station 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>

/*
 * 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) */

#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)

struct sta_entry {
        struct ieee80211_scan_entry base;
        TAILQ_ENTRY(sta_entry) se_list;
        LIST_ENTRY(sta_entry) se_hash;
        u_int8_t        se_fails;               /* failure to associate count */
        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# */
};

#define STA_HASHSIZE    32
/* simple hash is enough for variation of macaddr */
#define STA_HASH(addr)  \
        (((const u_int8_t *)(addr))[IEEE80211_ADDR_LEN - 1] % STA_HASHSIZE)

struct sta_table {
        spinlock_t st_lock;                     /* on scan table */
        TAILQ_HEAD(, sta_entry) st_entry;       /* all entries */
        ATH_LIST_HEAD(, sta_entry) st_hash[STA_HASHSIZE];
        spinlock_t st_scanlock;                 /* on st_scangen */
        u_int st_scangen;                       /* gen# for iterator */
        int st_newscan;
        struct IEEE80211_TQ_STRUCT st_actiontq; /* tasklet for "action" */
        struct ieee80211_scan_entry st_selbss;  /* selected bss for action tasklet */
        int (*st_action)(struct ieee80211vap *, const struct ieee80211_scan_entry *);
};

#define SCAN_STA_LOCK_INIT(_st, _name)                                  \
        spin_lock_init(&(_st)->st_lock)
#define SCAN_STA_LOCK_DESTROY(_st)
#define SCAN_STA_LOCK_IRQ(_st) do {                                     \
        unsigned long __stlockflags;                                    \
        spin_lock_irqsave(&(_st)->st_lock, __stlockflags);
#define SCAN_STA_UNLOCK_IRQ(_st)                                        \
        spin_unlock_irqrestore(&(_st)->st_lock, __stlockflags);         \
} while (0)
#define SCAN_STA_UNLOCK_IRQ_EARLY(_st)                                  \
        spin_unlock_irqrestore(&(_st)->st_lock, __stlockflags);

#define SCAN_STA_GEN_LOCK_INIT(_st, _name)                              \
        spin_lock_init(&(_st)->st_scanlock)
#define SCAN_STA_GEN_LOCK_DESTROY(_st)
#define SCAN_STA_GEN_LOCK(_st)          spin_lock(&(_st)->st_scanlock);
#define SCAN_STA_GEN_UNLOCK(_st)        spin_unlock(&(_st)->st_scanlock);

static void sta_flush_table(struct sta_table *);
static int match_bss(struct ieee80211vap *, const struct ieee80211_scan_state *,
        const struct sta_entry *);
static void action_tasklet(IEEE80211_TQUEUE_ARG);

/*
 * Attach prior to any scanning work.
 */
static int
sta_attach(struct ieee80211_scan_state *ss)
{
        struct sta_table *st;

        _MOD_INC_USE(THIS_MODULE, return 0);

        MALLOC(st, struct sta_table *, sizeof(struct sta_table),
                M_80211_SCAN, M_NOWAIT | M_ZERO);
        if (st == NULL)
                return 0;
        SCAN_STA_LOCK_INIT(st, "scan_sta");
        SCAN_STA_GEN_LOCK_INIT(st, "scan_sta_gen");
        TAILQ_INIT(&st->st_entry);
        IEEE80211_INIT_TQUEUE(&st->st_actiontq, action_tasklet, ss);
        ss->ss_priv = st;
        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) {
                IEEE80211_CANCEL_TQUEUE(&st->st_actiontq);
                sta_flush_table(st);
                FREE(st, M_80211_SCAN);
        }

        _MOD_DEC_USE(THIS_MODULE);
        return 1;
}

/*
 * Flush all per-scan state.
 */
static int
sta_flush(struct ieee80211_scan_state *ss)
{
        struct sta_table *st = ss->ss_priv;

        SCAN_STA_LOCK_IRQ(st);
        sta_flush_table(st);
        SCAN_STA_UNLOCK_IRQ(st);
        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_SAFE(se, &st->st_entry, se_list, next) {
                TAILQ_REMOVE(&st->st_entry, se, se_list);
                LIST_REMOVE(se, se_hash);
                FREE(se, M_80211_SCAN);
        }
}

static void
saveie(u_int8_t **iep, const u_int8_t *ie)
{
        if (ie == NULL)
                *iep = NULL;
        else
                ieee80211_saveie(iep, ie);
}

/*
 * 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, u_int64_t rtsf)
{
#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 u_int8_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);
        SCAN_STA_LOCK_IRQ(st);
        LIST_FOREACH(se, &st->st_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 sta_entry *, sizeof(struct sta_entry),
                M_80211_SCAN, M_NOWAIT | M_ZERO);
        if (se == NULL) {
                SCAN_STA_UNLOCK_IRQ_EARLY(st);
                return 0;
        }
        se->se_scangen = st->st_scangen-1;
        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]);

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

        /* clear failure count after STA_FAIL_AGE passes */
        if (se->se_fails && 
            time_after(jiffies, 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 = jiffies;            /* update time */
        se->se_seen = 1;
        se->se_notseen = 0;

        SCAN_STA_UNLOCK_IRQ(st);

        /*
         * If looking for a quick choice and nothing's
         * been found check here.
         */
        if (PICK1ST(ss) && match_bss(vap, ss, se) == 0)
                ss->ss_flags |= IEEE80211_SCAN_GOTPICK;

        return 1;
#undef PICK1ST
#undef ISPROBE
}

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;
}
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 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;
        }
}

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

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;
}

/*
 * Start a station-mode scan by populating the channel list.
 */
static int
sta_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct sta_table *st = ss->ss_priv;
        const struct scanlist *scan;
        enum ieee80211_phymode mode;
        struct ieee80211_channel *c;
        int i;

        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 = staScanTable; 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 ieee80211_scan_add_channels
                         * upgrade an 11b channel to 11g if available.
                         */
                        if (mode == IEEE80211_MODE_11B)
                                mode = IEEE80211_MODE_AUTO;
                }
                /* XR does not operate on turbo channels */
                if ((vap->iv_flags & IEEE80211_F_XR) &&
                    (mode == IEEE80211_MODE_TURBO_A ||
                     mode == IEEE80211_MODE_TURBO_G))
                        continue;
                /*
                 * Add the list of the channels; any that are not
                 * in the master channel list will be discarded.
                 */
                add_channels(ic, ss, mode, scan->list, scan->count);
        }

        /*
         * Add the channels from the ic (from HAL) that are not present
         * in the staScanTable.
         */
        for (i = 0; i < ic->ic_nchans; i++) {
                c = &ic->ic_channels[i];
                /*
                 * scan dynamic turbo channels in normal mode.
                 */
                if (IEEE80211_IS_CHAN_DTURBO(c))
                        continue;
                mode = ieee80211_chan2mode(c);
                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)
                                continue;

                }
                if (!checktable(staScanTable, c))
                        ss->ss_chans[ss->ss_last++] = c;
        }

        ss->ss_next = 0;
        /* XXX tunables */
        /* 
         * The scanner will stay on station for ss_maxdwell ms (using a 
         * timer), collecting responses.  ss_maxdwell can adjusted downward
         * so the station gets back on channel before DTIM occurs.  If the
         * station receives probe responses before ss_mindwell has elapsed, the
         * timer continues.  If it receives probe responses after ss_mindwell
         * then the timer is cancelled and the next channel is chosen.  
         * Basically, you are going to get the mindwell if you are scanning an
         * occupied channel in the real world and the maxdwell if it's empty.
         * 
         * This seems somehow wrong to me, as you tend to want to fish where the
         * fish is bitin'.  
         * 
         * I'm bumping mindwell up to 60ms (was 20ms).  This gives us a reasonable
         * chance to find all the APs with active scans, and should pick up 
         * everything within a few passes for passive.
        */
        ss->ss_mindwell = msecs_to_jiffies(60);         /* 60ms */
        ss->ss_maxdwell = msecs_to_jiffies(200);        /* 200ms */

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

        st->st_newscan = 1;

        return 0;
}

/*
 * Restart a bg scan.
 */
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)
{
        struct sta_table *st = ss->ss_priv;

        IEEE80211_CANCEL_TQUEUE(&st->st_actiontq);
        return 0;
}

static u_int8_t
maxrate(const struct ieee80211_scan_entry *se)
{
        u_int8_t max, r;
        int i;

        max = 0;
        for (i = 0; i < se->se_rates[1]; i++) {
                r = se->se_rates[2+i] & IEEE80211_RATE_VAL;
                if (r > max)
                        max = r;
        }
        for (i = 0; i < se->se_xrates[1]; i++) {
                r = se->se_xrates[2+i] & IEEE80211_RATE_VAL;
                if (r > max)
                        max = r;
        }
        return max;
}

/*
 * 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)
{
        u_int8_t maxa, maxb;
        int weight;

        /* privacy support preferred */
        if ((a->base.se_capinfo & IEEE80211_CAPINFO_PRIVACY) &&
            (b->base.se_capinfo & IEEE80211_CAPINFO_PRIVACY) == 0)
                return 1;
        if ((a->base.se_capinfo & IEEE80211_CAPINFO_PRIVACY) == 0 &&
            (b->base.se_capinfo & IEEE80211_CAPINFO_PRIVACY))
                return -1;

        /* compare count of previous failures */
        weight = b->se_fails - a->se_fails;
        if (abs(weight) > 1)
                return weight;

        if (abs(b->base.se_rssi - a->base.se_rssi) < 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 */
                if (IEEE80211_IS_CHAN_5GHZ(a->base.se_chan) &&
                   !IEEE80211_IS_CHAN_5GHZ(b->base.se_chan))
                        return 1;
                if (!IEEE80211_IS_CHAN_5GHZ(a->base.se_chan) &&
                    IEEE80211_IS_CHAN_5GHZ(b->base.se_chan))
                        return -1;
        }
        /* all things being equal, use signal level */
        return a->base.se_rssi - b->base.se_rssi;
}

/*
 * Check rate set suitability and return the best supported rate.
 */
static int
check_rate(struct ieee80211vap *vap, const struct ieee80211_scan_entry *se)
{
#define RV(v)   ((v) & IEEE80211_RATE_VAL)
        struct ieee80211com *ic = vap->iv_ic;
        const struct ieee80211_rateset *srs;
        int i, j, nrs, r, okrate, badrate, fixedrate;
        const u_int8_t *rs;

        okrate = badrate = fixedrate = 0;

        if (IEEE80211_IS_CHAN_HALF(se->se_chan))
                srs = &ic->ic_sup_half_rates;
        else if (IEEE80211_IS_CHAN_QUARTER(se->se_chan))
                srs = &ic->ic_sup_quarter_rates;
        else
                srs = &ic->ic_sup_rates[ieee80211_chan2mode(se->se_chan)];
        nrs = se->se_rates[1];
        rs = se->se_rates + 2;
        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 == vap->iv_fixed_rate)
                        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 (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;
        }
        if (okrate == 0 || vap->iv_fixed_rate != fixedrate)
                return badrate | IEEE80211_RATE_BASIC;
        else
                return RV(okrate);
#undef RV
}

static int
match_ssid(const u_int8_t *ie,
        int nssid, const struct ieee80211_scan_ssid ssids[])
{
        int i;

        for (i = 0; i < nssid; i++) {
                if (ie[1] == ssids[i].len &&
                     memcmp(ie + 2, ssids[i].ssid, ie[1]) == 0)
                        return 1;
        }
        return 0;
}

/*
 * Test a scan candidate for suitability/compatibility.
 */
static int
match_bss(struct ieee80211vap *vap,
        const struct ieee80211_scan_state *ss, const struct sta_entry *se0)
{
        struct ieee80211com *ic = vap->iv_ic;
        const struct ieee80211_scan_entry *se = &se0->base;
        u_int8_t rate;
        int fail;

        fail = 0;
        if (isclr(ic->ic_chan_active, ieee80211_chan2ieee(ic, se->se_chan)))
                fail |= 0x01;
        /*
         * 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 |= 0x01;
        if (vap->iv_opmode == IEEE80211_M_IBSS) {
                if ((se->se_capinfo & IEEE80211_CAPINFO_IBSS) == 0)
                        fail |= 0x02;
        } else {
                if ((se->se_capinfo & IEEE80211_CAPINFO_ESS) == 0)
                        fail |= 0x02;
        }
        if (vap->iv_flags & IEEE80211_F_PRIVACY) {
                if ((se->se_capinfo & IEEE80211_CAPINFO_PRIVACY) == 0)
                        fail |= 0x04;
        } else {
                /* XXX does this mean privacy is supported or required? */
                if (se->se_capinfo & IEEE80211_CAPINFO_PRIVACY)
                        fail |= 0x04;
        }
        rate = check_rate(vap, se);
        if (rate & IEEE80211_RATE_BASIC)
                fail |= 0x08;
        if (ss->ss_nssid != 0 &&
            !match_ssid(se->se_ssid, ss->ss_nssid, ss->ss_ssid))
                fail |= 0x10;
        if ((vap->iv_flags & IEEE80211_F_DESBSSID) &&
            !IEEE80211_ADDR_EQ(vap->iv_des_bssid, se->se_bssid))
                fail |= 0x20;
        if (se0->se_fails >= STA_FAILS_MAX)
                fail |= 0x40;
        if (se0->se_notseen >= STA_PURGE_SCANS)
                fail |= 0x80;
#ifdef IEEE80211_DEBUG
        if (ieee80211_msg_is_reported(vap, IEEE80211_MSG_SCAN | IEEE80211_MSG_ROAM)) {
                printk(" %03x", fail);
                printk(" %c " MAC_FMT,
                        fail & 0x40 ? '=' : fail & 0x80 ? '^' : fail ? '-' : '+',
                        MAC_ADDR(se->se_macaddr));
                printk(" " MAC_FMT "%c", MAC_ADDR(se->se_bssid),
                        fail & 0x20 ? '!' : ' ');
                printk(" %3d%c", ieee80211_chan2ieee(ic, se->se_chan),
                        fail & 0x01 ? '!' : ' ');
                printk(" %+4d", se->se_rssi);
                printk(" %2dM%c", (rate & IEEE80211_RATE_VAL) / 2,
                        fail & 0x08 ? '!' : ' ');
                printk(" %4s%c",
                        (se->se_capinfo & IEEE80211_CAPINFO_ESS) ? "ess" :
                        (se->se_capinfo & IEEE80211_CAPINFO_IBSS) ? "ibss" : "????",
                        fail & 0x02 ? '!' : ' ');
                printk(" %3s%c ",
                        (se->se_capinfo & IEEE80211_CAPINFO_PRIVACY) ? "wep" : "no",
                        fail & 0x04 ? '!' : ' ');
                ieee80211_print_essid(se->se_ssid + 2, se->se_ssid[1]);
                printk("%s\n", fail & 0x10 ? "!" : "");
        }
#endif
        return fail;
}

static void
sta_update_notseen(struct sta_table *st)
{
        struct sta_entry *se;

        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH(se, &st->st_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++;
        }
        SCAN_STA_UNLOCK_IRQ(st);
}

static void
sta_dec_fails(struct sta_table *st)
{
        struct sta_entry *se;

        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH(se, &st->st_entry, se_list)
                if (se->se_fails)
                        se->se_fails--;
        SCAN_STA_UNLOCK_IRQ(st);
}

static struct sta_entry *
select_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se, *selbs = NULL;

        IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN | IEEE80211_MSG_ROAM, " %s\n",
                "macaddr          bssid         chan  rssi  rate flag  wep  essid");
        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH(se, &st->st_entry, se_list) {
                if (match_bss(vap, ss, se) == 0) {
                        if (selbs == NULL)
                                selbs = se;
                        else if (sta_compare(se, selbs) > 0)
                                selbs = se;
                }
        }
        SCAN_STA_UNLOCK_IRQ(st);

        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,
        int (*action)(struct ieee80211vap *, const struct ieee80211_scan_entry *),
        u_int32_t flags)
{
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *selbss;

        IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN, "%s Checking scan results\n",
                __func__);

        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__);
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 STAs
                 * where we've previously had some success.
                 */
                sta_dec_fails(st);
                st->st_newscan = 1;
                return 0;                       /* restart scan */
        }
        st->st_action = ss->ss_ops->scan_default;
        if (action)
                st->st_action = action;
        if ((selbss = select_bss(ss, vap)) == NULL) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                        "%s: select_bss failed\n", __func__);
                goto notfound;
        }
        st->st_selbss = selbss->base;

        /* 
         * Must defer action to avoid possible recursive call through 80211
         * state machine, which would result in recursive locking.
         */
        IEEE80211_SCHEDULE_TQUEUE(&st->st_actiontq);

        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 u_int8_t macaddr[IEEE80211_ADDR_LEN],
                struct ieee80211_scan_ssid *essid)
{
        struct sta_entry *se;
        int hash = STA_HASH(macaddr);

        SCAN_STA_LOCK_IRQ(st);
        LIST_FOREACH(se, &st->st_hash[hash], se_hash)
                if (IEEE80211_ADDR_EQ(se->base.se_macaddr, macaddr) &&
                    (essid->len == se->base.se_ssid[1] &&
                     !memcmp(se->base.se_ssid+2, essid->ssid,
                             se->base.se_ssid[1])))
                        break;
        SCAN_STA_UNLOCK_IRQ(st);

        return se;              /* NB: unlocked */
}

static void
sta_roam_check(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
        struct ieee80211_node *ni = vap->iv_bss;
        struct ieee80211com *ic = vap->iv_ic;
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se, *selbs;
        u_int8_t roamRate, curRate;
        int8_t roamRssi, curRssi;

        se = sta_lookup(st, ni->ni_macaddr, ss->ss_ssid);
        if (se == NULL) {
                /* XXX something is wrong */
                return;
        }

        if (IEEE80211_IS_CHAN_ANYG(ic->ic_bsschan)) {
                roamRate = vap->iv_roam.rate11g;
                roamRssi = vap->iv_roam.rssi11g;
        } else if (IEEE80211_IS_CHAN_B(ic->ic_bsschan)) {
                roamRate = vap->iv_roam.rate11bOnly;
                roamRssi = vap->iv_roam.rssi11bOnly;
        } else {
                roamRate = vap->iv_roam.rate11a;
                roamRssi = vap->iv_roam.rssi11a;
        }
        /* NB: the most up to date rssi is in the node, not the scan cache */
        curRssi = ic->ic_node_getrssi(ni);
        if (vap->iv_fixed_rate == IEEE80211_FIXED_RATE_NONE) {
                curRate = ni->ni_rates.rs_rates[ni->ni_txrate] & 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: ensure compare below fails */
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_ROAM,
                        "%s: currssi %d roamrssi %d\n",
                        __func__, curRssi, roamRssi);
        }
        if ((vap->iv_flags & IEEE80211_F_BGSCAN) &&
            time_after(jiffies, ic->ic_lastscan + vap->iv_scanvalid)) {
                /*
                 * Scan cache contents is too old; check about updating it.
                 */
                if (curRate < roamRate || curRssi < roamRssi) {
                        /*
                         * Thresholds exceeded, force a scan now so we
                         * have current state to make a decision with.
                         */
                        ieee80211_bg_scan(vap);
                } else if (time_after(jiffies,
                        ic->ic_lastdata + vap->iv_bgscanidle)) {
                        /*
                         * We're not in need of a new ap, but idle;
                         * kick off a bg scan to replenish the cache.
                         */
                        ieee80211_bg_scan(vap);
                }
        } else {
                /*
                 * Scan cache contents are warm enough to use;
                 * check if a new ap should be used and switch.
                 * XXX deauth current ap
                 */
                if (curRate < roamRate || curRssi < roamRssi) {
                        se->base.se_rssi = curRssi;
                        selbs = select_bss(ss, vap);
                        if (selbs != NULL && selbs != se)
                                ieee80211_sta_join(vap, &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;
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se, *next;

        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH_SAFE(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);
                        FREE(se, M_80211_SCAN);
                }
        }
        SCAN_STA_UNLOCK_IRQ(st);
        /*
         * 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
         */
        KASSERT(vap->iv_opmode == IEEE80211_M_STA,
                ("wrong mode %u", vap->iv_opmode));
        if (vap->iv_opmode == IEEE80211_M_STA &&
            vap->iv_ic->ic_roaming == IEEE80211_ROAMING_AUTO &&
            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 int
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;
        int res = 0;

        SCAN_STA_GEN_LOCK(st);
        gen = st->st_scangen++;
restart:
        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH(se, &st->st_entry, se_list) {
                if (se->se_scangen != gen) {
                        se->se_scangen = gen;
                        /* update public state */
                        se->base.se_age = jiffies - se->se_lastupdate;
                        SCAN_STA_UNLOCK_IRQ_EARLY(st);

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

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

                        goto restart;
                }
        }

        SCAN_STA_UNLOCK_IRQ(st);

 done:
        SCAN_STA_GEN_UNLOCK(st);

        return res;
}

static void
sta_assoc_fail(struct ieee80211_scan_state *ss,
        const u_int8_t macaddr[IEEE80211_ADDR_LEN], int reason)
{
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se;

        if (ss->ss_vap->iv_ic->ic_roaming == IEEE80211_ROAMING_MANUAL)
                return;

        se = sta_lookup(st, macaddr, ss->ss_ssid);
        if (se != NULL) {
                se->se_fails++;
                se->se_lastfail = jiffies;
                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 u_int8_t macaddr[IEEE80211_ADDR_LEN])
{
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se;

        se = sta_lookup(st, macaddr, ss->ss_ssid);
        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 = jiffies;
        }
}

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,
        .scan_default           = ieee80211_sta_join,
};

/*
 * Start an adhoc-mode scan by populating the channel list.
 */
static int
adhoc_start(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct sta_table *st = ss->ss_priv;
        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 = staScanTable; 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 ieee80211_scan_add_channels
                         * upgrade an 11b channel to 11g if available.
                         */
                        if (mode == IEEE80211_MODE_11B)
                                mode = IEEE80211_MODE_AUTO;
                }
                /* XR does not operate on turbo channels */
                if ((vap->iv_flags & IEEE80211_F_XR) &&
                    (mode == IEEE80211_MODE_TURBO_A ||
                     mode == IEEE80211_MODE_TURBO_G))
                        continue;
                /*
                 * Add the list of the channels; any that are not
                 * in the master channel list will be discarded.
                 */
                add_channels(ic, ss, mode, scan->list, scan->count);
        }
        ss->ss_next = 0;
        /* XXX tunables */
        ss->ss_mindwell = msecs_to_jiffies(200);        /* 200ms */
        ss->ss_maxdwell = msecs_to_jiffies(200);        /* 200ms */

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

        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.
 * XXX need regulatory domain constraints
 */
static struct ieee80211_channel *
adhoc_pick_channel(struct ieee80211_scan_state *ss)
{
        struct sta_table *st = ss->ss_priv;
        struct sta_entry *se;
        struct ieee80211_channel *c, *bestchan;
        int i, bestrssi, maxrssi;

        bestchan = NULL;
        bestrssi = -1;

        SCAN_STA_LOCK_IRQ(st);
        for (i = 0; i < ss->ss_last; i++) {
                c = ss->ss_chans[i];
                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;
        }
        SCAN_STA_UNLOCK_IRQ(st);

        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,
        int (*action)(struct ieee80211vap *, const struct ieee80211_scan_entry *),
        u_int32_t flags)
{
        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,
                ("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;
        }

        st->st_action = ss->ss_ops->scan_default;
        if (action)
                st->st_action = action;

        /*
         * 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 ||
                (selbs = select_bss(ss, vap)) == NULL) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                        "%s: no scan candidate\n", __func__);
                if (vap->iv_des_nssid) {
                        /*
                         * 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)
                                chan = adhoc_pick_channel(ss);
                        else
                                chan = vap->iv_des_chan;
                        if (chan != NULL) {
                                struct ieee80211_scan_entry se;

                                memset(&se, 0, sizeof(se));
                                se.se_chan = chan;
                                st->st_selbss = se;
                                /* defer action */
                                IEEE80211_SCHEDULE_TQUEUE(&st->st_actiontq);
                                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 STAs
                 * where we've previously had some success.
                 */
                sta_dec_fails(st);
                st->st_newscan = 1;
                return 0;                       /* restart scan */
        }

        /* 
         * Must defer action to avoid possible recursive call through 80211
         * state machine, which would result in recursive locking.
         */
        st->st_selbss = selbs->base;
        IEEE80211_SCHEDULE_TQUEUE(&st->st_actiontq);

        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;

        SCAN_STA_LOCK_IRQ(st);
        TAILQ_FOREACH_SAFE(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);
                        FREE(se, M_80211_SCAN);
                }
        }
        SCAN_STA_UNLOCK_IRQ(st);
}

/*
 * Default action to execute when a scan entry is found for adhoc
 * mode.  Return 1 on success, 0 on failure
 */
static int
adhoc_default_action(struct ieee80211vap *vap,
        const struct ieee80211_scan_entry *se)
{
        u_int8_t zeroMacAddr[IEEE80211_ADDR_LEN];

        memset(&zeroMacAddr, 0, IEEE80211_ADDR_LEN);
        if (IEEE80211_ADDR_EQ(se->se_bssid, &zeroMacAddr[0])) {
                ieee80211_create_ibss(vap, se->se_chan);
                return 1;
        } else
                return ieee80211_sta_join(vap, se);
}

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_add               = sta_add,
        .scan_age               = adhoc_age,
        .scan_iterate           = sta_iterate,
        .scan_assoc_fail        = sta_assoc_fail,
        .scan_assoc_success     = sta_assoc_success,
        .scan_default           = adhoc_default_action,
};

static void
action_tasklet(IEEE80211_TQUEUE_ARG data)
{
        struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *)data;
        struct sta_table *st = (struct sta_table *)ss->ss_priv;
        struct ieee80211vap *vap = ss->ss_vap;
        struct ieee80211_channel *chan;

        if ((*ss->ss_ops->scan_default)(vap, &st->st_selbss))
                return;

        switch (vap->iv_opmode) {
        case IEEE80211_M_STA:
                sta_dec_fails(st);
                st->st_newscan = 1;
                break;
        default:
                /* ADHOC */
                if (vap->iv_des_nssid) {
                        /*
                         * 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)
                                chan = adhoc_pick_channel(ss);
                        else
                                chan = vap->iv_des_chan;
                        if (chan != NULL) {
                                struct ieee80211_scan_entry se;

                                memset(&se, 0, sizeof(se));
                                se.se_chan = chan;
                                if ((*ss->ss_ops->scan_default)(vap, &se))
                                        return;
                        }
                }
                /*
                 * 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 STAs
                 * where we've previously had some success.
                 */
                sta_dec_fails(st);
                st->st_newscan = 1;
                break;
        }

        /* 
         * restart scan 
         */

        /* no ap, clear the flag for a new scan */
        vap->iv_ic->ic_flags &= ~IEEE80211_F_SCAN;
        if ((ss->ss_flags & IEEE80211_SCAN_USECACHE) == 0)
                ieee80211_start_scan(vap, ss->ss_flags, ss->ss_duration, ss->ss_nssid, ss->ss_ssid);
}

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

static int __init
init_scanner_sta(void)
{
        ieee80211_scanner_register(IEEE80211_M_STA, &sta_default);
        ieee80211_scanner_register(IEEE80211_M_IBSS, &adhoc_default);
        ieee80211_scanner_register(IEEE80211_M_AHDEMO, &adhoc_default);
        return 0;
}
module_init(init_scanner_sta);

static void __exit
exit_scanner_sta(void)
{
        ieee80211_scanner_unregister_all(&sta_default);
        ieee80211_scanner_unregister_all(&adhoc_default);
}
module_exit(exit_scanner_sta);