Remove empty DragonFly CVS IDs.

[dragonfly.git] / sys / netproto / 802_11 / wlan / ieee80211_scan.c

/*-
 * Copyright (c) 2002-2008 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.c 195618 2009-07-11 15:02:45Z rpaulo $
 */

/*
 * IEEE 802.11 scanning support.
 */
#include "opt_wlan.h"

#include <sys/param.h>
#include <sys/systm.h> 
#include <sys/proc.h>
#include <sys/kernel.h>
 
#include <sys/condvar.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 <net/bpf.h>

struct scan_state {
        struct ieee80211_scan_state base;       /* public state */

        u_int           ss_iflags;              /* flags used internally */
#define ISCAN_MINDWELL  0x0001          /* min dwell time reached */
#define ISCAN_DISCARD   0x0002          /* discard rx'd frames */
#define ISCAN_CANCEL    0x0004          /* cancel current scan */
#define ISCAN_ABORT     0x0008          /* end the scan immediately */
        unsigned long   ss_chanmindwell;        /* min dwell on curchan */
        unsigned long   ss_scanend;             /* time scan must stop */
        u_int           ss_duration;            /* duration for next scan */
        struct task     ss_scan_task;           /* scan execution */
        struct cv       ss_scan_cv;             /* scan signal */
        struct callout  ss_scan_timer;          /* scan timer */
};
#define SCAN_PRIVATE(ss)        ((struct scan_state *) ss)

/*
 * Amount of time to go off-channel during a background
 * scan.  This value should be large enough to catch most
 * ap's but short enough that we can return on-channel
 * before our listen interval expires.
 *
 * XXX tunable
 * XXX check against configured listen interval
 */
#define IEEE80211_SCAN_OFFCHANNEL       msecs_to_ticks(150)

/*
 * Roaming-related defaults.  RSSI thresholds are as returned by the
 * driver (.5dBm).  Transmit rate thresholds are IEEE rate codes (i.e
 * .5M units) or MCS.
 */
/* rssi thresholds */
#define ROAM_RSSI_11A_DEFAULT           14      /* 11a bss */
#define ROAM_RSSI_11B_DEFAULT           14      /* 11b bss */
#define ROAM_RSSI_11BONLY_DEFAULT       14      /* 11b-only bss */
/* transmit rate thresholds */
#define ROAM_RATE_11A_DEFAULT           2*12    /* 11a bss */
#define ROAM_RATE_11B_DEFAULT           2*5     /* 11b bss */
#define ROAM_RATE_11BONLY_DEFAULT       2*1     /* 11b-only bss */
#define ROAM_RATE_HALF_DEFAULT          2*6     /* half-width 11a/g bss */
#define ROAM_RATE_QUARTER_DEFAULT       2*3     /* quarter-width 11a/g bss */
#define ROAM_MCS_11N_DEFAULT            (1 | IEEE80211_RATE_MCS) /* 11n bss */

static  void scan_curchan(struct ieee80211_scan_state *, unsigned long);
static  void scan_mindwell(struct ieee80211_scan_state *);
static  void scan_signal_callout(void *);
static  void scan_signal(struct ieee80211_scan_state *ss);
static  void scan_task(void *, int);

MALLOC_DEFINE(M_80211_SCAN, "80211scan", "802.11 scan state");

void
ieee80211_scan_attach(struct ieee80211com *ic)
{
        struct scan_state *ss;

        ss = (struct scan_state *) kmalloc(sizeof(struct scan_state),
                M_80211_SCAN, M_INTWAIT | M_ZERO);
        if (ss == NULL) {
                ic->ic_scan = NULL;
                return;
        }
        wlan_cv_init(&ss->ss_scan_cv, "scan");
        callout_init(&ss->ss_scan_timer);
        TASK_INIT(&ss->ss_scan_task, 0, scan_task, ss);
        ic->ic_scan = &ss->base;
        ss->base.ss_ic = ic;

        ic->ic_scan_curchan = scan_curchan;
        ic->ic_scan_mindwell = scan_mindwell;
}

void
ieee80211_scan_detach(struct ieee80211com *ic)
{
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if (ss != NULL) {
                SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_ABORT;
                scan_signal(ss);
                ieee80211_draintask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
                callout_stop(&SCAN_PRIVATE(ss)->ss_scan_timer);
                KASSERT((ic->ic_flags & IEEE80211_F_SCAN) == 0,
                    ("scan still running"));
                if (ss->ss_ops != NULL) {
                        ss->ss_ops->scan_detach(ss);
                        ss->ss_ops = NULL;
                }
                ic->ic_scan = NULL;
                kfree(SCAN_PRIVATE(ss), M_80211_SCAN);
        }
}

static const struct ieee80211_roamparam defroam[IEEE80211_MODE_MAX] = {
        [IEEE80211_MODE_11A]    = { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_11A_DEFAULT },
        [IEEE80211_MODE_11G]    = { .rssi = ROAM_RSSI_11B_DEFAULT,
                                    .rate = ROAM_RATE_11B_DEFAULT },
        [IEEE80211_MODE_11B]    = { .rssi = ROAM_RSSI_11BONLY_DEFAULT,
                                    .rate = ROAM_RATE_11BONLY_DEFAULT },
        [IEEE80211_MODE_TURBO_A]= { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_11A_DEFAULT },
        [IEEE80211_MODE_TURBO_G]= { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_11A_DEFAULT },
        [IEEE80211_MODE_STURBO_A]={ .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_11A_DEFAULT },
        [IEEE80211_MODE_HALF]   = { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_HALF_DEFAULT },
        [IEEE80211_MODE_QUARTER]= { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_RATE_QUARTER_DEFAULT },
        [IEEE80211_MODE_11NA]   = { .rssi = ROAM_RSSI_11A_DEFAULT,
                                    .rate = ROAM_MCS_11N_DEFAULT },
        [IEEE80211_MODE_11NG]   = { .rssi = ROAM_RSSI_11B_DEFAULT,
                                    .rate = ROAM_MCS_11N_DEFAULT },
};

void
ieee80211_scan_vattach(struct ieee80211vap *vap)
{
        vap->iv_bgscanidle = (IEEE80211_BGSCAN_IDLE_DEFAULT*1000)/hz;
        vap->iv_bgscanintvl = IEEE80211_BGSCAN_INTVAL_DEFAULT*hz;
        vap->iv_scanvalid = IEEE80211_SCAN_VALID_DEFAULT*hz;

        vap->iv_roaming = IEEE80211_ROAMING_AUTO;
        memcpy(vap->iv_roamparms, defroam, sizeof(defroam));
}

void
ieee80211_scan_vdetach(struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss;

        ss = ic->ic_scan;
        if (ss != NULL && ss->ss_vap == vap) {
                if (ic->ic_flags & IEEE80211_F_SCAN) {
                        SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_ABORT;
                        scan_signal(ss);
                }
                if (ss->ss_ops != NULL) {
                        ss->ss_ops->scan_detach(ss);
                        ss->ss_ops = NULL;
                }
                ss->ss_vap = NULL;
        }
}

/*
 * Simple-minded scanner module support.
 */
static const char *scan_modnames[IEEE80211_OPMODE_MAX] = {
        "wlan_scan_sta",        /* IEEE80211_M_IBSS */
        "wlan_scan_sta",        /* IEEE80211_M_STA */
        "wlan_scan_wds",        /* IEEE80211_M_WDS */
        "wlan_scan_sta",        /* IEEE80211_M_AHDEMO */
        "wlan_scan_ap",         /* IEEE80211_M_HOSTAP */
        "wlan_scan_monitor",    /* IEEE80211_M_MONITOR */
        "wlan_scan_sta",        /* IEEE80211_M_MBSS */
};
static const struct ieee80211_scanner *scanners[IEEE80211_OPMODE_MAX];

const struct ieee80211_scanner *
ieee80211_scanner_get(enum ieee80211_opmode mode)
{
        if (mode >= IEEE80211_OPMODE_MAX)
                return NULL;
        if (scanners[mode] == NULL)
                ieee80211_load_module(scan_modnames[mode]);
        return scanners[mode];
}

void
ieee80211_scanner_register(enum ieee80211_opmode mode,
        const struct ieee80211_scanner *scan)
{
        if (mode >= IEEE80211_OPMODE_MAX)
                return;
        scanners[mode] = scan;
}

void
ieee80211_scanner_unregister(enum ieee80211_opmode mode,
        const struct ieee80211_scanner *scan)
{
        if (mode >= IEEE80211_OPMODE_MAX)
                return;
        if (scanners[mode] == scan)
                scanners[mode] = NULL;
}

void
ieee80211_scanner_unregister_all(const struct ieee80211_scanner *scan)
{
        int m;

        for (m = 0; m < IEEE80211_OPMODE_MAX; m++)
                if (scanners[m] == scan)
                        scanners[m] = NULL;
}

/*
 * Update common scanner state to reflect the current
 * operating mode.  This is called when the state machine
 * is transitioned to RUN state w/o scanning--e.g. when
 * operating in monitor mode.  The purpose of this is to
 * ensure later callbacks find ss_ops set to properly
 * reflect current operating mode.
 */
static void
scan_update_locked(struct ieee80211vap *vap,
        const struct ieee80211_scanner *scan)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

#ifdef IEEE80211_DEBUG
        if (ss->ss_vap != vap || ss->ss_ops != scan) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: current scanner is <%s:%s>, switch to <%s:%s>\n",
                    __func__,
                    ss->ss_vap != NULL ?
                        ss->ss_vap->iv_ifp->if_xname : "none",
                    ss->ss_vap != NULL ?
                        ieee80211_opmode_name[ss->ss_vap->iv_opmode] : "none",
                    vap->iv_ifp->if_xname,
                    ieee80211_opmode_name[vap->iv_opmode]);
        }
#endif
        ss->ss_vap = vap;
        if (ss->ss_ops != scan) {
                /*
                 * Switch scanners; detach old, attach new.  Special
                 * case where a single scan module implements multiple
                 * policies by using different scan ops but a common
                 * core.  We assume if the old and new attach methods
                 * are identical then it's ok to just change ss_ops
                 * and not flush the internal state of the module.
                 */
                if (scan == NULL || ss->ss_ops == NULL ||
                    ss->ss_ops->scan_attach != scan->scan_attach) {
                        if (ss->ss_ops != NULL)
                                ss->ss_ops->scan_detach(ss);
                        if (scan != NULL && !scan->scan_attach(ss)) {
                                /* XXX attach failure */
                                /* XXX stat+msg */
                                scan = NULL;
                        }
                }
                ss->ss_ops = scan;
        }
}

static char
channel_type(const struct ieee80211_channel *c)
{
        if (IEEE80211_IS_CHAN_ST(c))
                return 'S';
        if (IEEE80211_IS_CHAN_108A(c))
                return 'T';
        if (IEEE80211_IS_CHAN_108G(c))
                return 'G';
        if (IEEE80211_IS_CHAN_HT(c))
                return 'n';
        if (IEEE80211_IS_CHAN_A(c))
                return 'a';
        if (IEEE80211_IS_CHAN_ANYG(c))
                return 'g';
        if (IEEE80211_IS_CHAN_B(c))
                return 'b';
        return 'f';
}

void
ieee80211_scan_dump_channels(const struct ieee80211_scan_state *ss)
{
        struct ieee80211com *ic = ss->ss_ic;
        const char *sep;
        int i;

        sep = "";
        for (i = ss->ss_next; i < ss->ss_last; i++) {
                const struct ieee80211_channel *c = ss->ss_chans[i];

                kprintf("%s%u%c", sep, ieee80211_chan2ieee(ic, c),
                        channel_type(c));
                sep = ", ";
        }
}

#ifdef IEEE80211_DEBUG
static void
scan_dump(struct ieee80211_scan_state *ss)
{
        struct ieee80211vap *vap = ss->ss_vap;

        if_printf(vap->iv_ifp, "scan set ");
        ieee80211_scan_dump_channels(ss);
        kprintf(" dwell min %lums max %lums\n",
            ticks_to_msecs(ss->ss_mindwell), ticks_to_msecs(ss->ss_maxdwell));
}
#endif /* IEEE80211_DEBUG */

static void
copy_ssid(struct ieee80211vap *vap, struct ieee80211_scan_state *ss,
        int nssid, const struct ieee80211_scan_ssid ssids[])
{
        if (nssid > IEEE80211_SCAN_MAX_SSID) {
                /* XXX printf */
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: too many ssid %d, ignoring all of them\n",
                    __func__, nssid);
                return;
        }
        memcpy(ss->ss_ssid, ssids, nssid * sizeof(ssids[0]));
        ss->ss_nssid = nssid;
}

/*
 * Start a scan unless one is already going.
 */
static int
start_scan_locked(const struct ieee80211_scanner *scan,
        struct ieee80211vap *vap, int flags, u_int duration,
        u_int mindwell, u_int maxdwell,
        u_int nssid, const struct ieee80211_scan_ssid ssids[])
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if (ic->ic_flags & IEEE80211_F_CSAPENDING) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: scan inhibited by pending channel change\n", __func__);
        } else if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: %s scan, duration %u mindwell %u maxdwell %u, desired mode %s, %s%s%s%s%s%s\n"
                    , __func__
                    , flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive"
                    , duration, mindwell, maxdwell
                    , ieee80211_phymode_name[vap->iv_des_mode]
                    , flags & IEEE80211_SCAN_FLUSH ? "flush" : "append"
                    , flags & IEEE80211_SCAN_NOPICK ? ", nopick" : ""
                    , flags & IEEE80211_SCAN_NOJOIN ? ", nojoin" : ""
                    , flags & IEEE80211_SCAN_NOBCAST ? ", nobcast" : ""
                    , flags & IEEE80211_SCAN_PICK1ST ? ", pick1st" : ""
                    , flags & IEEE80211_SCAN_ONCE ? ", once" : ""
                );

                scan_update_locked(vap, scan);
                if (ss->ss_ops != NULL) {
                        if ((flags & IEEE80211_SCAN_NOSSID) == 0)
                                copy_ssid(vap, ss, nssid, ssids);

                        /* NB: top 4 bits for internal use */
                        ss->ss_flags = flags & 0xfff;
                        if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
                                vap->iv_stats.is_scan_active++;
                        else
                                vap->iv_stats.is_scan_passive++;
                        if (flags & IEEE80211_SCAN_FLUSH)
                                ss->ss_ops->scan_flush(ss);

                        /* NB: flush frames rx'd before 1st channel change */
                        SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
                        SCAN_PRIVATE(ss)->ss_duration = duration;
                        ss->ss_next = 0;
                        ss->ss_mindwell = mindwell;
                        ss->ss_maxdwell = maxdwell;
                        /* NB: scan_start must be before the scan runtask */
                        ss->ss_ops->scan_start(ss, vap);
#ifdef IEEE80211_DEBUG
                        if (ieee80211_msg_scan(vap))
                                scan_dump(ss);
#endif /* IEEE80211_DEBUG */
                        ic->ic_flags |= IEEE80211_F_SCAN;
                        ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
                }
        } else {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: %s scan already in progress\n", __func__,
                    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
        }
        return (ic->ic_flags & IEEE80211_F_SCAN);
}

/*
 * Start a scan unless one is already going.
 */
int
ieee80211_start_scan(struct ieee80211vap *vap, int flags,
        u_int duration, u_int mindwell, u_int maxdwell,
        u_int nssid, const struct ieee80211_scan_ssid ssids[])
{
        struct ieee80211com *ic = vap->iv_ic;
        const struct ieee80211_scanner *scan;
        int result;

        ic = vap->iv_ic;
        scan = ieee80211_scanner_get(vap->iv_opmode);
        if (scan == NULL) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: no scanner support for %s mode\n",
                    __func__, ieee80211_opmode_name[vap->iv_opmode]);
                /* XXX stat */
                return 0;
        }

        result = start_scan_locked(scan, vap, flags, duration,
            mindwell, maxdwell, nssid, ssids);

        return result;
}

/*
 * Check the scan cache for an ap/channel to use; if that
 * fails then kick off a new scan.
 */
int
ieee80211_check_scan(struct ieee80211vap *vap, int flags,
        u_int duration, u_int mindwell, u_int maxdwell,
        u_int nssid, const struct ieee80211_scan_ssid ssids[])
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;
        const struct ieee80211_scanner *scan;
        int result;

        scan = ieee80211_scanner_get(vap->iv_opmode);
        if (scan == NULL) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: no scanner support for %d mode\n",
                    __func__, vap->iv_opmode);
                /* XXX stat */
                return 0;
        }

        /*
         * Check if there's a list of scan candidates already.
         * XXX want more than the ap we're currently associated with
         */

        IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
            "%s: %s scan, %s%s%s%s%s\n"
            , __func__
            , flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive"
            , flags & IEEE80211_SCAN_FLUSH ? "flush" : "append"
            , flags & IEEE80211_SCAN_NOPICK ? ", nopick" : ""
            , flags & IEEE80211_SCAN_NOJOIN ? ", nojoin" : ""
            , flags & IEEE80211_SCAN_PICK1ST ? ", pick1st" : ""
            , flags & IEEE80211_SCAN_ONCE ? ", once" : ""
        );

        if (ss->ss_ops != scan) {
                /* XXX re-use cache contents? e.g. adhoc<->sta */
                flags |= IEEE80211_SCAN_FLUSH;
        }
        scan_update_locked(vap, scan);
        if (ss->ss_ops != NULL) {
                /* XXX verify ss_ops matches vap->iv_opmode */
                if ((flags & IEEE80211_SCAN_NOSSID) == 0) {
                        /*
                         * Update the ssid list and mark flags so if
                         * we call start_scan it doesn't duplicate work.
                         */
                        copy_ssid(vap, ss, nssid, ssids);
                        flags |= IEEE80211_SCAN_NOSSID;
                }
                if ((ic->ic_flags & IEEE80211_F_SCAN) == 0 &&
                    (flags & IEEE80211_SCAN_FLUSH) == 0 &&
                    time_before(ticks, ic->ic_lastscan + vap->iv_scanvalid)) {
                        /*
                         * We're not currently scanning and the cache is
                         * deemed hot enough to consult.  Lock out others
                         * by marking IEEE80211_F_SCAN while we decide if
                         * something is already in the scan cache we can
                         * use.  Also discard any frames that might come
                         * in while temporarily marked as scanning.
                         */
                        SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
                        ic->ic_flags |= IEEE80211_F_SCAN;

                        /* NB: need to use supplied flags in check */
                        ss->ss_flags = flags & 0xff;
                        result = ss->ss_ops->scan_end(ss, vap);

                        ic->ic_flags &= ~IEEE80211_F_SCAN;
                        SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_DISCARD;
                        if (result) {
                                ieee80211_notify_scan_done(vap);
                                return 1;
                        }
                }
        }
        result = start_scan_locked(scan, vap, flags, duration,
            mindwell, maxdwell, nssid, ssids);

        return result;
}

/*
 * Check the scan cache for an ap/channel to use; if that fails
 * then kick off a scan using the current settings.
 */
int
ieee80211_check_scan_current(struct ieee80211vap *vap)
{
        return ieee80211_check_scan(vap,
            IEEE80211_SCAN_ACTIVE,
            IEEE80211_SCAN_FOREVER, 0, 0,
            vap->iv_des_nssid, vap->iv_des_ssid);
}

/*
 * Restart a previous scan.  If the previous scan completed
 * then we start again using the existing channel list.
 */
int
ieee80211_bg_scan(struct ieee80211vap *vap, int flags)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;
        const struct ieee80211_scanner *scan;

        scan = ieee80211_scanner_get(vap->iv_opmode);
        if (scan == NULL) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: no scanner support for %d mode\n",
                    __func__, vap->iv_opmode);
                /* XXX stat */
                return 0;
        }

        if ((ic->ic_flags & IEEE80211_F_SCAN) == 0) {
                u_int duration;
                /*
                 * Go off-channel for a fixed interval that is large
                 * enough to catch most ap's but short enough that
                 * we can return on-channel before our listen interval
                 * expires.
                 */
                duration = IEEE80211_SCAN_OFFCHANNEL;

                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: %s scan, ticks %u duration %u\n", __func__,
                    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive",
                    ticks, duration);

                scan_update_locked(vap, scan);
                if (ss->ss_ops != NULL) {
                        ss->ss_vap = vap;
                        /*
                         * A background scan does not select a new sta; it
                         * just refreshes the scan cache.  Also, indicate
                         * the scan logic should follow the beacon schedule:
                         * we go off-channel and scan for a while, then
                         * return to the bss channel to receive a beacon,
                         * then go off-channel again.  All during this time
                         * we notify the ap we're in power save mode.  When
                         * the scan is complete we leave power save mode.
                         * If any beacon indicates there are frames pending
                         * for us then we drop out of power save mode
                         * (and background scan) automatically by way of the
                         * usual sta power save logic.
                         */
                        ss->ss_flags |= IEEE80211_SCAN_NOPICK
                                     |  IEEE80211_SCAN_BGSCAN
                                     |  flags
                                     ;
                        /* if previous scan completed, restart */
                        if (ss->ss_next >= ss->ss_last) {
                                if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
                                        vap->iv_stats.is_scan_active++;
                                else
                                        vap->iv_stats.is_scan_passive++;
                                /*
                                 * NB: beware of the scan cache being flushed;
                                 *     if the channel list is empty use the
                                 *     scan_start method to populate it.
                                 */
                                ss->ss_next = 0;
                                if (ss->ss_last != 0)
                                        ss->ss_ops->scan_restart(ss, vap);
                                else {
                                        ss->ss_ops->scan_start(ss, vap);
#ifdef IEEE80211_DEBUG
                                        if (ieee80211_msg_scan(vap))
                                                scan_dump(ss);
#endif /* IEEE80211_DEBUG */
                                }
                        }
                        /* NB: flush frames rx'd before 1st channel change */
                        SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_DISCARD;
                        SCAN_PRIVATE(ss)->ss_duration = duration;
                        ss->ss_maxdwell = duration;
                        ic->ic_flags |= IEEE80211_F_SCAN;
                        ic->ic_flags_ext |= IEEE80211_FEXT_BGSCAN;
                        ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
                } else {
                        /* XXX msg+stat */
                }
        } else {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: %s scan already in progress\n", __func__,
                    ss->ss_flags & IEEE80211_SCAN_ACTIVE ? "active" : "passive");
        }

        /* NB: racey, does it matter? */
        return (ic->ic_flags & IEEE80211_F_SCAN);
}

/*
 * Cancel any scan currently going on for the specified vap.
 */
void
ieee80211_cancel_scan(struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if ((ic->ic_flags & IEEE80211_F_SCAN) &&
            ss->ss_vap == vap &&
            (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: cancel %s scan\n", __func__,
                    ss->ss_flags & IEEE80211_SCAN_ACTIVE ?
                        "active" : "passive");

                /* clear bg scan NOPICK and mark cancel request */
                ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
                SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
                /* wake up the scan task */
                scan_signal(ss);
        }
}

/*
 * Cancel any scan currently going on.
 */
void
ieee80211_cancel_anyscan(struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if ((ic->ic_flags & IEEE80211_F_SCAN) &&
            (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: cancel %s scan\n", __func__,
                    ss->ss_flags & IEEE80211_SCAN_ACTIVE ?
                        "active" : "passive");

                /* clear bg scan NOPICK and mark cancel request */
                ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
                SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_CANCEL;
                /* wake up the scan task */
                scan_signal(ss);
        }
}

/*
 * Public access to scan_next for drivers that manage
 * scanning themselves (e.g. for firmware-based devices).
 */
void
ieee80211_scan_next(struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

        /* wake up the scan task */
        scan_signal(ss);
}

/*
 * Public access to scan_next for drivers that are not able to scan single
 * channels (e.g. for firmware-based devices).
 */
void
ieee80211_scan_done(struct ieee80211vap *vap)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss;

        ss = ic->ic_scan;
        ss->ss_next = ss->ss_last; /* all channels are complete */
        scan_signal(ss);
}

/*
 * Probe the curent channel, if allowed, while scanning.
 * If the channel is not marked passive-only then send
 * a probe request immediately.  Otherwise mark state and
 * listen for beacons on the channel; if we receive something
 * then we'll transmit a probe request.
 */
void
ieee80211_probe_curchan(struct ieee80211vap *vap, int force)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;
        struct ifnet *ifp = vap->iv_ifp;
        int i;

        if ((ic->ic_curchan->ic_flags & IEEE80211_CHAN_PASSIVE) && !force) {
                ic->ic_flags_ext |= IEEE80211_FEXT_PROBECHAN;
                return;
        }
        /*
         * Send directed probe requests followed by any
         * broadcast probe request.
         * XXX remove dependence on ic/vap->iv_bss
         */
        for (i = 0; i < ss->ss_nssid; i++)
                ieee80211_send_probereq(vap->iv_bss,
                        vap->iv_myaddr, ifp->if_broadcastaddr,
                        ifp->if_broadcastaddr,
                        ss->ss_ssid[i].ssid, ss->ss_ssid[i].len);
        if ((ss->ss_flags & IEEE80211_SCAN_NOBCAST) == 0)
                ieee80211_send_probereq(vap->iv_bss,
                        vap->iv_myaddr, ifp->if_broadcastaddr,
                        ifp->if_broadcastaddr,
                        "", 0);
}

/*
 * Scan curchan.  If this is an active scan and the channel
 * is not marked passive then send probe request frame(s).
 * Arrange for the channel change after maxdwell ticks.
 */
static void
scan_curchan(struct ieee80211_scan_state *ss, unsigned long maxdwell)
{
        struct ieee80211vap *vap  = ss->ss_vap;

        if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
                ieee80211_probe_curchan(vap, 0);
        callout_reset(&SCAN_PRIVATE(ss)->ss_scan_timer,
                      maxdwell, scan_signal_callout, ss);
}

static void
scan_signal_callout(void *arg)
{
        struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;

        wlan_serialize_enter();
        scan_signal(ss);
        wlan_serialize_exit();
}

static void
scan_signal(struct ieee80211_scan_state *ss)
{
        wlan_cv_signal(&SCAN_PRIVATE(ss)->ss_scan_cv, 0);
}

/*
 * Handle mindwell requirements completed; initiate a channel
 * change to the next channel asap.
 */
static void
scan_mindwell(struct ieee80211_scan_state *ss)
{
        struct ieee80211com *ic = ss->ss_ic;

        ic = ss->ss_ic;
        scan_signal(ss);
}

static void
scan_task(void *arg, int pending)
{
#define ISCAN_REP       (ISCAN_MINDWELL | ISCAN_DISCARD)
        struct ieee80211_scan_state *ss = (struct ieee80211_scan_state *) arg;
        struct ieee80211vap *vap;
        struct ieee80211com *ic;
        struct ieee80211_channel *chan;
        unsigned long maxdwell, scanend;
        int scandone = 0;

        wlan_serialize_enter();
        vap = ss->ss_vap;
        ic = ss->ss_ic;

        if (vap == NULL || (ic->ic_flags & IEEE80211_F_SCAN) == 0 ||
            (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)) {
                /* Cancelled before we started */
                goto done;
        }

        if (ss->ss_next == ss->ss_last) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                        "%s: no channels to scan\n", __func__);
                goto done;
        }

        if (vap->iv_opmode == IEEE80211_M_STA &&
            vap->iv_state == IEEE80211_S_RUN) {
                if ((vap->iv_bss->ni_flags & IEEE80211_NODE_PWR_MGT) == 0) {
                        /* Enable station power save mode */
                        ieee80211_sta_pwrsave(vap, 1);
                        /*
                         * Use an 1ms delay so the null data frame has a chance
                         * to go out.  Minimum one tick.
                         * XXX Should use M_TXCB mechanism to eliminate this.
                         */
                        wlan_cv_timedwait(&SCAN_PRIVATE(ss)->ss_scan_cv,
                                          hz / 1000 + 1);
                        if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)
                                goto done;
                }
        }

        scanend = ticks + SCAN_PRIVATE(ss)->ss_duration;
        ic->ic_scan_start(ic);          /* notify driver */

        for (;;) {
                scandone = (ss->ss_next >= ss->ss_last) ||
                    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0;
                if (scandone || (ss->ss_flags & IEEE80211_SCAN_GOTPICK) ||
                    (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT) ||
                     time_after(ticks + ss->ss_mindwell, scanend))
                        break;

                chan = ss->ss_chans[ss->ss_next++];

                /*
                 * Watch for truncation due to the scan end time.
                 */
                if (time_after(ticks + ss->ss_maxdwell, scanend))
                        maxdwell = scanend - ticks;
                else
                        maxdwell = ss->ss_maxdwell;

                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: chan %3d%c -> %3d%c [%s, dwell min %lums max %lums]\n",
                    __func__,
                    ieee80211_chan2ieee(ic, ic->ic_curchan),
                        channel_type(ic->ic_curchan),
                    ieee80211_chan2ieee(ic, chan), channel_type(chan),
                    (ss->ss_flags & IEEE80211_SCAN_ACTIVE) &&
                        (chan->ic_flags & IEEE80211_CHAN_PASSIVE) == 0 ?
                        "active" : "passive",
                    ticks_to_msecs(ss->ss_mindwell), ticks_to_msecs(maxdwell));

                /*
                 * Potentially change channel and phy mode.
                 */
                ic->ic_curchan = chan;
                ic->ic_rt = ieee80211_get_ratetable(chan);
                /*
                 * Perform the channel change and scan unlocked so the driver
                 * may sleep. Once set_channel returns the hardware has
                 * completed the channel change.
                 */
                ic->ic_set_channel(ic);
                ieee80211_radiotap_chan_change(ic);

                /*
                 * Scan curchan.  Drivers for "intelligent hardware"
                 * override ic_scan_curchan to tell the device to do
                 * the work.  Otherwise we manage the work outselves;
                 * sending a probe request (as needed), and arming the
                 * timeout to switch channels after maxdwell ticks.
                 *
                 * scan_curchan should only pause for the time required to
                 * prepare/initiate the hardware for the scan (if at all), the
                 * below condvar is used to sleep for the channels dwell time
                 * and allows it to be signalled for abort.
                 */
                ic->ic_scan_curchan(ss, maxdwell);

                SCAN_PRIVATE(ss)->ss_chanmindwell = ticks + ss->ss_mindwell;
                /* clear mindwell lock and initial channel change flush */
                SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;

                if ((SCAN_PRIVATE(ss)->ss_iflags & (ISCAN_CANCEL|ISCAN_ABORT)))
                        continue;

                /* Wait to be signalled to scan the next channel */
                wlan_cv_wait(&SCAN_PRIVATE(ss)->ss_scan_cv);
        }
        if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_ABORT)
                goto done;

        ic->ic_scan_end(ic);            /* notify driver */

        /*
         * Record scan complete time.  Note that we also do
         * this when canceled so any background scan will
         * not be restarted for a while.
         */
        if (scandone)
                ic->ic_lastscan = ticks;
        /* return to the bss channel */
        if (ic->ic_bsschan != IEEE80211_CHAN_ANYC &&
            ic->ic_curchan != ic->ic_bsschan) {
                ieee80211_setupcurchan(ic, ic->ic_bsschan);
                ic->ic_set_channel(ic);
                ieee80211_radiotap_chan_change(ic);
        }
        /* clear internal flags and any indication of a pick */
        SCAN_PRIVATE(ss)->ss_iflags &= ~ISCAN_REP;
        ss->ss_flags &= ~IEEE80211_SCAN_GOTPICK;

        /*
         * If not canceled and scan completed, do post-processing.
         * If the callback function returns 0, then it wants to
         * continue/restart scanning.  Unfortunately we needed to
         * notify the driver to end the scan above to avoid having
         * rx frames alter the scan candidate list.
         */
        if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) == 0 &&
            !ss->ss_ops->scan_end(ss, vap) &&
            (ss->ss_flags & IEEE80211_SCAN_ONCE) == 0 &&
            time_before(ticks + ss->ss_mindwell, scanend)) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                    "%s: done, restart "
                    "[ticks %u, dwell min %lu scanend %lu]\n",
                    __func__,
                    ticks, ss->ss_mindwell, scanend);
                ss->ss_next = 0;        /* reset to begining */
                if (ss->ss_flags & IEEE80211_SCAN_ACTIVE)
                        vap->iv_stats.is_scan_active++;
                else
                        vap->iv_stats.is_scan_passive++;

                ss->ss_ops->scan_restart(ss, vap);      /* XXX? */
                ieee80211_runtask(ic, &SCAN_PRIVATE(ss)->ss_scan_task);
                goto done2;
        }

        /* past here, scandone is ``true'' if not in bg mode */
        if ((ss->ss_flags & IEEE80211_SCAN_BGSCAN) == 0)
                scandone = 1;

        IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
            "%s: %s, [ticks %u, dwell min %lu scanend %lu]\n",
            __func__, scandone ? "done" : "stopped",
            ticks, ss->ss_mindwell, scanend);

        /*
         * Clear the SCAN bit first in case frames are
         * pending on the station power save queue.  If
         * we defer this then the dispatch of the frames
         * may generate a request to cancel scanning.
         */
done:
        ic->ic_flags &= ~IEEE80211_F_SCAN;
        /*
         * Drop out of power save mode when a scan has
         * completed.  If this scan was prematurely terminated
         * because it is a background scan then don't notify
         * the ap; we'll either return to scanning after we
         * receive the beacon frame or we'll drop out of power
         * save mode because the beacon indicates we have frames
         * waiting for us.
         */
        if (scandone) {
                ieee80211_sta_pwrsave(vap, 0);
                if (ss->ss_next >= ss->ss_last) {
                        ieee80211_notify_scan_done(vap);
                        ic->ic_flags_ext &= ~IEEE80211_FEXT_BGSCAN;
                }
        }
        SCAN_PRIVATE(ss)->ss_iflags &= ~(ISCAN_CANCEL|ISCAN_ABORT);
        ss->ss_flags &= ~(IEEE80211_SCAN_ONCE | IEEE80211_SCAN_PICK1ST);
done2:
        wlan_serialize_exit();
#undef ISCAN_REP
}

#ifdef IEEE80211_DEBUG
static void
dump_country(const uint8_t *ie)
{
        const struct ieee80211_country_ie *cie =
           (const struct ieee80211_country_ie *) ie;
        int i, nbands, schan, nchan;

        if (cie->len < 3) {
                kprintf(" <bogus country ie, len %d>", cie->len);
                return;
        }
        kprintf(" country [%c%c%c", cie->cc[0], cie->cc[1], cie->cc[2]);
        nbands = (cie->len - 3) / sizeof(cie->band[0]);
        for (i = 0; i < nbands; i++) {
                schan = cie->band[i].schan;
                nchan = cie->band[i].nchan;
                if (nchan != 1)
                        kprintf(" %u-%u,%u", schan, schan + nchan-1,
                            cie->band[i].maxtxpwr);
                else
                        kprintf(" %u,%u", schan, cie->band[i].maxtxpwr);
        }
        kprintf("]");
}

static void
dump_probe_beacon(uint8_t subtype, int isnew,
        const uint8_t mac[IEEE80211_ADDR_LEN],
        const struct ieee80211_scanparams *sp, int rssi)
{

        kprintf("[%6D] %s%s on chan %u (bss chan %u) ",
            mac, ":", isnew ? "new " : "",
            ieee80211_mgt_subtype_name[subtype >> IEEE80211_FC0_SUBTYPE_SHIFT],
            sp->chan, sp->bchan);
        ieee80211_print_essid(sp->ssid + 2, sp->ssid[1]);
        kprintf(" rssi %d\n", rssi);

        if (isnew) {
                kprintf("[%6D] caps 0x%x bintval %u erp 0x%x", 
                        mac, ":", sp->capinfo, sp->bintval, sp->erp);
                if (sp->country != NULL)
                        dump_country(sp->country);
                kprintf("\n");
        }
}
#endif /* IEEE80211_DEBUG */

/*
 * Process a beacon or probe response frame.
 */
void
ieee80211_add_scan(struct ieee80211vap *vap,
        const struct ieee80211_scanparams *sp,
        const struct ieee80211_frame *wh,
        int subtype, int rssi, int noise)
{
        struct ieee80211com *ic = vap->iv_ic;
        struct ieee80211_scan_state *ss = ic->ic_scan;

        /* XXX locking */
        /*
         * Frames received during startup are discarded to avoid
         * using scan state setup on the initial entry to the timer
         * callback.  This can occur because the device may enable
         * rx prior to our doing the initial channel change in the
         * timer routine.
         */
        if (SCAN_PRIVATE(ss)->ss_iflags & ISCAN_DISCARD)
                return;
#ifdef IEEE80211_DEBUG
        if (ieee80211_msg_scan(vap) && (ic->ic_flags & IEEE80211_F_SCAN))
                dump_probe_beacon(subtype, 1, wh->i_addr2, sp, rssi);
#endif
        if (ss->ss_ops != NULL &&
            ss->ss_ops->scan_add(ss, sp, wh, subtype, rssi, noise)) {
                /*
                 * If we've reached the min dwell time terminate
                 * the timer so we'll switch to the next channel.
                 */
                if ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_MINDWELL) == 0 &&
                    time_after_eq(ticks, SCAN_PRIVATE(ss)->ss_chanmindwell)) {
                        IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
                            "%s: chan %3d%c min dwell met (%u > %lu)\n",
                            __func__,
                            ieee80211_chan2ieee(ic, ic->ic_curchan),
                                channel_type(ic->ic_curchan),
                            ticks, SCAN_PRIVATE(ss)->ss_chanmindwell);
                        SCAN_PRIVATE(ss)->ss_iflags |= ISCAN_MINDWELL;
                        /*
                         * NB: trigger at next clock tick or wait for the
                         * hardware.
                         */
                        ic->ic_scan_mindwell(ss);
                }
        }
}

/*
 * Timeout/age scan cache entries; called from sta timeout
 * timer (XXX should be self-contained).
 */
void
ieee80211_scan_timeout(struct ieee80211com *ic)
{
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if (ss->ss_ops != NULL)
                ss->ss_ops->scan_age(ss);
}

/*
 * Mark a scan cache entry after a successful associate.
 */
void
ieee80211_scan_assoc_success(struct ieee80211vap *vap, const uint8_t mac[])
{
        struct ieee80211_scan_state *ss = vap->iv_ic->ic_scan;

        if (ss->ss_ops != NULL) {
                IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_SCAN,
                        mac, "%s",  __func__);
                ss->ss_ops->scan_assoc_success(ss, mac);
        }
}

/*
 * Demerit a scan cache entry after failing to associate.
 */
void
ieee80211_scan_assoc_fail(struct ieee80211vap *vap,
        const uint8_t mac[], int reason)
{
        struct ieee80211_scan_state *ss = vap->iv_ic->ic_scan;

        if (ss->ss_ops != NULL) {
                IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_SCAN, mac,
                        "%s: reason %u", __func__, reason);
                ss->ss_ops->scan_assoc_fail(ss, mac, reason);
        }
}

/*
 * Iterate over the contents of the scan cache.
 */
void
ieee80211_scan_iterate(struct ieee80211vap *vap,
        ieee80211_scan_iter_func *f, void *arg)
{
        struct ieee80211_scan_state *ss = vap->iv_ic->ic_scan;

        if (ss->ss_ops != NULL)
                ss->ss_ops->scan_iterate(ss, f, arg);
}

/*
 * Flush the contents of the scan cache.
 */
void
ieee80211_scan_flush(struct ieee80211vap *vap)
{
        struct ieee80211_scan_state *ss = vap->iv_ic->ic_scan;

        if (ss->ss_ops != NULL && ss->ss_vap == vap) {
                IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN, "%s\n",  __func__);
                ss->ss_ops->scan_flush(ss);
        }
}

/*
 * Check the scan cache for an ap/channel to use; if that
 * fails then kick off a new scan.
 */
struct ieee80211_channel *
ieee80211_scan_pickchannel(struct ieee80211com *ic, int flags)
{
        struct ieee80211_scan_state *ss = ic->ic_scan;

        if (ss == NULL || ss->ss_ops == NULL || ss->ss_vap == NULL) {
                /* XXX printf? */
                return NULL;
        }
        if (ss->ss_ops->scan_pickchan == NULL) {
                IEEE80211_DPRINTF(ss->ss_vap, IEEE80211_MSG_SCAN,
                    "%s: scan module does not support picking a channel, "
                    "opmode %d\n", __func__, ss->ss_vap->iv_opmode);
                return NULL;
        }
        return ss->ss_ops->scan_pickchan(ss, flags);
}