initial commit with v2.6.32.60

[linux-2.6.32.60-moxart.git] / net / mac80211 / scan.c

/*
 * Scanning implementation
 *
 * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
 * Copyright 2004, Instant802 Networks, Inc.
 * Copyright 2005, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
 * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/* TODO: figure out how to avoid that the "current BSS" expires */

#include <linux/wireless.h>
#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <net/mac80211.h>

#include "ieee80211_i.h"
#include "driver-ops.h"
#include "mesh.h"

#define IEEE80211_PROBE_DELAY (HZ / 33)
#define IEEE80211_CHANNEL_TIME (HZ / 33)
#define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)

struct ieee80211_bss *
ieee80211_rx_bss_get(struct ieee80211_local *local, u8 *bssid, int freq,
                     u8 *ssid, u8 ssid_len)
{
        return (void *)cfg80211_get_bss(local->hw.wiphy,
                                        ieee80211_get_channel(local->hw.wiphy,
                                                              freq),
                                        bssid, ssid, ssid_len,
                                        0, 0);
}

static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
{
        struct ieee80211_bss *bss = (void *)cbss;

        kfree(bss_mesh_id(bss));
        kfree(bss_mesh_cfg(bss));
}

void ieee80211_rx_bss_put(struct ieee80211_local *local,
                          struct ieee80211_bss *bss)
{
        cfg80211_put_bss((struct cfg80211_bss *)bss);
}

struct ieee80211_bss *
ieee80211_bss_info_update(struct ieee80211_local *local,
                          struct ieee80211_rx_status *rx_status,
                          struct ieee80211_mgmt *mgmt,
                          size_t len,
                          struct ieee802_11_elems *elems,
                          struct ieee80211_channel *channel,
                          bool beacon)
{
        struct ieee80211_bss *bss;
        int clen, srlen;
        s32 signal = 0;

        if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
                signal = rx_status->signal * 100;
        else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
                signal = (rx_status->signal * 100) / local->hw.max_signal;

        bss = (void *)cfg80211_inform_bss_frame(local->hw.wiphy, channel,
                                                mgmt, len, signal, GFP_ATOMIC);

        if (!bss)
                return NULL;

        bss->cbss.free_priv = ieee80211_rx_bss_free;

        /* save the ERP value so that it is available at association time */
        if (elems->erp_info && elems->erp_info_len >= 1) {
                bss->erp_value = elems->erp_info[0];
                bss->has_erp_value = 1;
        }

        if (elems->tim) {
                struct ieee80211_tim_ie *tim_ie =
                        (struct ieee80211_tim_ie *)elems->tim;
                bss->dtim_period = tim_ie->dtim_period;
        }

        /* set default value for buggy AP/no TIM element */
        if (bss->dtim_period == 0)
                bss->dtim_period = 1;

        /* replace old supported rates if we get new values */
        srlen = 0;
        if (elems->supp_rates) {
                clen = IEEE80211_MAX_SUPP_RATES;
                if (clen > elems->supp_rates_len)
                        clen = elems->supp_rates_len;
                memcpy(bss->supp_rates, elems->supp_rates, clen);
                srlen += clen;
        }
        if (elems->ext_supp_rates) {
                clen = IEEE80211_MAX_SUPP_RATES - srlen;
                if (clen > elems->ext_supp_rates_len)
                        clen = elems->ext_supp_rates_len;
                memcpy(bss->supp_rates + srlen, elems->ext_supp_rates, clen);
                srlen += clen;
        }
        if (srlen)
                bss->supp_rates_len = srlen;

        bss->wmm_used = elems->wmm_param || elems->wmm_info;

        if (!beacon)
                bss->last_probe_resp = jiffies;

        return bss;
}

ieee80211_rx_result
ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
{
        struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
        struct ieee80211_mgmt *mgmt;
        struct ieee80211_bss *bss;
        u8 *elements;
        struct ieee80211_channel *channel;
        size_t baselen;
        int freq;
        __le16 fc;
        bool presp, beacon = false;
        struct ieee802_11_elems elems;

        if (skb->len < 2)
                return RX_DROP_UNUSABLE;

        mgmt = (struct ieee80211_mgmt *) skb->data;
        fc = mgmt->frame_control;

        if (ieee80211_is_ctl(fc))
                return RX_CONTINUE;

        if (skb->len < 24)
                return RX_DROP_MONITOR;

        presp = ieee80211_is_probe_resp(fc);
        if (presp) {
                /* ignore ProbeResp to foreign address */
                if (memcmp(mgmt->da, sdata->dev->dev_addr, ETH_ALEN))
                        return RX_DROP_MONITOR;

                presp = true;
                elements = mgmt->u.probe_resp.variable;
                baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
        } else {
                beacon = ieee80211_is_beacon(fc);
                baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
                elements = mgmt->u.beacon.variable;
        }

        if (!presp && !beacon)
                return RX_CONTINUE;

        if (baselen > skb->len)
                return RX_DROP_MONITOR;

        ieee802_11_parse_elems(elements, skb->len - baselen, &elems);

        if (elems.ds_params && elems.ds_params_len == 1)
                freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
        else
                freq = rx_status->freq;

        channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);

        if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
                return RX_DROP_MONITOR;

        bss = ieee80211_bss_info_update(sdata->local, rx_status,
                                        mgmt, skb->len, &elems,
                                        channel, beacon);
        if (bss)
                ieee80211_rx_bss_put(sdata->local, bss);

        dev_kfree_skb(skb);
        return RX_QUEUED;
}

/*
 * inform AP that we will go to sleep so that it will buffer the frames
 * while we scan
 */
static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;

        local->scan_ps_enabled = false;

        /* FIXME: what to do when local->pspolling is true? */

        del_timer_sync(&local->dynamic_ps_timer);
        cancel_work_sync(&local->dynamic_ps_enable_work);

        if (local->hw.conf.flags & IEEE80211_CONF_PS) {
                local->scan_ps_enabled = true;
                local->hw.conf.flags &= ~IEEE80211_CONF_PS;
                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
        }

        if (!(local->scan_ps_enabled) ||
            !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
                /*
                 * If power save was enabled, no need to send a nullfunc
                 * frame because AP knows that we are sleeping. But if the
                 * hardware is creating the nullfunc frame for power save
                 * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
                 * enabled) and power save was enabled, the firmware just
                 * sent a null frame with power save disabled. So we need
                 * to send a new nullfunc frame to inform the AP that we
                 * are again sleeping.
                 */
                ieee80211_send_nullfunc(local, sdata, 1);
}

/* inform AP that we are awake again, unless power save is enabled */
static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_local *local = sdata->local;

        if (!local->ps_sdata)
                ieee80211_send_nullfunc(local, sdata, 0);
        else if (local->scan_ps_enabled) {
                /*
                 * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
                 * will send a nullfunc frame with the powersave bit set
                 * even though the AP already knows that we are sleeping.
                 * This could be avoided by sending a null frame with power
                 * save bit disabled before enabling the power save, but
                 * this doesn't gain anything.
                 *
                 * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
                 * to send a nullfunc frame because AP already knows that
                 * we are sleeping, let's just enable power save mode in
                 * hardware.
                 */
                local->hw.conf.flags |= IEEE80211_CONF_PS;
                ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
        } else if (local->hw.conf.dynamic_ps_timeout > 0) {
                /*
                 * If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
                 * had been running before leaving the operating channel,
                 * restart the timer now and send a nullfunc frame to inform
                 * the AP that we are awake.
                 */
                ieee80211_send_nullfunc(local, sdata, 0);
                mod_timer(&local->dynamic_ps_timer, jiffies +
                          msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
        }
}

static void ieee80211_restore_scan_ies(struct ieee80211_local *local)
{
        kfree(local->scan_req->ie);
        local->scan_req->ie = local->orig_ies;
        local->scan_req->ie_len = local->orig_ies_len;
}

void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct ieee80211_sub_if_data *sdata;
        bool was_hw_scan;

        mutex_lock(&local->scan_mtx);

        /*
         * It's ok to abort a not-yet-running scan (that
         * we have one at all will be verified by checking
         * local->scan_req next), but not to complete it
         * successfully.
         */
        if (WARN_ON(!local->scanning && !aborted))
                aborted = true;

        if (WARN_ON(!local->scan_req)) {
                mutex_unlock(&local->scan_mtx);
                return;
        }

        if (test_bit(SCAN_HW_SCANNING, &local->scanning))
                ieee80211_restore_scan_ies(local);

        if (local->scan_req != local->int_scan_req)
                cfg80211_scan_done(local->scan_req, aborted);
        local->scan_req = NULL;
        local->scan_sdata = NULL;

        was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
        local->scanning = 0;
        local->scan_channel = NULL;

        /* we only have to protect scan_req and hw/sw scan */
        mutex_unlock(&local->scan_mtx);

        ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
        if (was_hw_scan)
                goto done;

        ieee80211_configure_filter(local);

        drv_sw_scan_complete(local);

        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!netif_running(sdata->dev))
                        continue;

                /* Tell AP we're back */
                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        if (sdata->u.mgd.associated) {
                                ieee80211_scan_ps_disable(sdata);
                                netif_tx_wake_all_queues(sdata->dev);
                        }
                } else
                        netif_tx_wake_all_queues(sdata->dev);

                /* re-enable beaconing */
                if (sdata->vif.type == NL80211_IFTYPE_AP ||
                    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
                    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
                        ieee80211_bss_info_change_notify(
                                sdata, BSS_CHANGED_BEACON_ENABLED);
        }
        mutex_unlock(&local->iflist_mtx);

 done:
        ieee80211_recalc_idle(local);
        ieee80211_mlme_notify_scan_completed(local);
        ieee80211_ibss_notify_scan_completed(local);
        ieee80211_mesh_notify_scan_completed(local);
}
EXPORT_SYMBOL(ieee80211_scan_completed);

static int ieee80211_start_sw_scan(struct ieee80211_local *local)
{
        struct ieee80211_sub_if_data *sdata;

        /*
         * Hardware/driver doesn't support hw_scan, so use software
         * scanning instead. First send a nullfunc frame with power save
         * bit on so that AP will buffer the frames for us while we are not
         * listening, then send probe requests to each channel and wait for
         * the responses. After all channels are scanned, tune back to the
         * original channel and send a nullfunc frame with power save bit
         * off to trigger the AP to send us all the buffered frames.
         *
         * Note that while local->sw_scanning is true everything else but
         * nullfunc frames and probe requests will be dropped in
         * ieee80211_tx_h_check_assoc().
         */
        drv_sw_scan_start(local);

        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!netif_running(sdata->dev))
                        continue;

                /* disable beaconing */
                if (sdata->vif.type == NL80211_IFTYPE_AP ||
                    sdata->vif.type == NL80211_IFTYPE_ADHOC ||
                    sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
                        ieee80211_bss_info_change_notify(
                                sdata, BSS_CHANGED_BEACON_ENABLED);

                /*
                 * only handle non-STA interfaces here, STA interfaces
                 * are handled in the scan state machine
                 */
                if (sdata->vif.type != NL80211_IFTYPE_STATION)
                        netif_tx_stop_all_queues(sdata->dev);
        }
        mutex_unlock(&local->iflist_mtx);

        local->next_scan_state = SCAN_DECISION;
        local->scan_channel_idx = 0;

        ieee80211_configure_filter(local);

        /* TODO: start scan as soon as all nullfunc frames are ACKed */
        ieee80211_queue_delayed_work(&local->hw,
                                     &local->scan_work,
                                     IEEE80211_CHANNEL_TIME);

        return 0;
}


static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
                                  struct cfg80211_scan_request *req)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
        int rc;

        if (local->scan_req)
                return -EBUSY;

        if (req != local->int_scan_req &&
            sdata->vif.type == NL80211_IFTYPE_STATION &&
            !list_empty(&ifmgd->work_list)) {
                /* actually wait for the work it's doing to finish/time out */
                set_bit(IEEE80211_STA_REQ_SCAN, &ifmgd->request);
                local->scan_req = req;
                local->scan_sdata = sdata;
                return 0;
        }

        if (local->ops->hw_scan) {
                u8 *ies;
                int ielen;

                ies = kmalloc(2 + IEEE80211_MAX_SSID_LEN +
                              local->scan_ies_len + req->ie_len, GFP_KERNEL);
                if (!ies)
                        return -ENOMEM;

                ielen = ieee80211_build_preq_ies(local, ies,
                                                 req->ie, req->ie_len);
                local->orig_ies = req->ie;
                local->orig_ies_len = req->ie_len;
                req->ie = ies;
                req->ie_len = ielen;
        }

        local->scan_req = req;
        local->scan_sdata = sdata;

        if (local->ops->hw_scan)
                __set_bit(SCAN_HW_SCANNING, &local->scanning);
        else
                __set_bit(SCAN_SW_SCANNING, &local->scanning);
        /*
         * Kicking off the scan need not be protected,
         * only the scan variable stuff, since now
         * local->scan_req is assigned and other callers
         * will abort their scan attempts.
         *
         * This avoids getting a scan_mtx -> iflist_mtx
         * dependency, so that the scan completed calls
         * have more locking freedom.
         */

        ieee80211_recalc_idle(local);
        mutex_unlock(&local->scan_mtx);

        if (local->ops->hw_scan)
                rc = drv_hw_scan(local, local->scan_req);
        else
                rc = ieee80211_start_sw_scan(local);

        mutex_lock(&local->scan_mtx);

        if (rc) {
                if (local->ops->hw_scan)
                        ieee80211_restore_scan_ies(local);
                local->scanning = 0;

                ieee80211_recalc_idle(local);

                local->scan_req = NULL;
                local->scan_sdata = NULL;
        }

        return rc;
}

static int ieee80211_scan_state_decision(struct ieee80211_local *local,
                                         unsigned long *next_delay)
{
        bool associated = false;
        struct ieee80211_sub_if_data *sdata;

        /* if no more bands/channels left, complete scan and advance to the idle state */
        if (local->scan_channel_idx >= local->scan_req->n_channels) {
                ieee80211_scan_completed(&local->hw, false);
                return 1;
        }

        /* check if at least one STA interface is associated */
        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!netif_running(sdata->dev))
                        continue;

                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        if (sdata->u.mgd.associated) {
                                associated = true;
                                break;
                        }
                }
        }
        mutex_unlock(&local->iflist_mtx);

        if (local->scan_channel) {
                /*
                 * we're currently scanning a different channel, let's
                 * switch back to the operating channel now if at least
                 * one interface is associated. Otherwise just scan the
                 * next channel
                 */
                if (associated)
                        local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
                else
                        local->next_scan_state = SCAN_SET_CHANNEL;
        } else {
                /*
                 * we're on the operating channel currently, let's
                 * leave that channel now to scan another one
                 */
                local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
        }

        *next_delay = 0;
        return 0;
}

static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
                                                    unsigned long *next_delay)
{
        struct ieee80211_sub_if_data *sdata;

        /*
         * notify the AP about us leaving the channel and stop all STA interfaces
         */
        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!netif_running(sdata->dev))
                        continue;

                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        netif_tx_stop_all_queues(sdata->dev);
                        if (sdata->u.mgd.associated)
                                ieee80211_scan_ps_enable(sdata);
                }
        }
        mutex_unlock(&local->iflist_mtx);

        __set_bit(SCAN_OFF_CHANNEL, &local->scanning);

        /* advance to the next channel to be scanned */
        *next_delay = HZ / 10;
        local->next_scan_state = SCAN_SET_CHANNEL;
}

static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
                                                    unsigned long *next_delay)
{
        struct ieee80211_sub_if_data *sdata = local->scan_sdata;

        /* switch back to the operating channel */
        local->scan_channel = NULL;
        ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);

        /*
         * notify the AP about us being back and restart all STA interfaces
         */
        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!netif_running(sdata->dev))
                        continue;

                /* Tell AP we're back */
                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        if (sdata->u.mgd.associated)
                                ieee80211_scan_ps_disable(sdata);
                        netif_tx_wake_all_queues(sdata->dev);
                }
        }
        mutex_unlock(&local->iflist_mtx);

        __clear_bit(SCAN_OFF_CHANNEL, &local->scanning);

        *next_delay = HZ / 5;
        local->next_scan_state = SCAN_DECISION;
}

static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
                                             unsigned long *next_delay)
{
        int skip;
        struct ieee80211_channel *chan;
        struct ieee80211_sub_if_data *sdata = local->scan_sdata;

        skip = 0;
        chan = local->scan_req->channels[local->scan_channel_idx];

        if (chan->flags & IEEE80211_CHAN_DISABLED ||
            (sdata->vif.type == NL80211_IFTYPE_ADHOC &&
             chan->flags & IEEE80211_CHAN_NO_IBSS))
                skip = 1;

        if (!skip) {
                local->scan_channel = chan;
                if (ieee80211_hw_config(local,
                                        IEEE80211_CONF_CHANGE_CHANNEL))
                        skip = 1;
        }

        /* advance state machine to next channel/band */
        local->scan_channel_idx++;

        if (skip) {
                /* if we skip this channel return to the decision state */
                local->next_scan_state = SCAN_DECISION;
                return;
        }

        /*
         * Probe delay is used to update the NAV, cf. 11.1.3.2.2
         * (which unfortunately doesn't say _why_ step a) is done,
         * but it waits for the probe delay or until a frame is
         * received - and the received frame would update the NAV).
         * For now, we do not support waiting until a frame is
         * received.
         *
         * In any case, it is not necessary for a passive scan.
         */
        if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
            !local->scan_req->n_ssids) {
                *next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
                local->next_scan_state = SCAN_DECISION;
                return;
        }

        /* active scan, send probes */
        *next_delay = IEEE80211_PROBE_DELAY;
        local->next_scan_state = SCAN_SEND_PROBE;
}

static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
                                            unsigned long *next_delay)
{
        int i;
        struct ieee80211_sub_if_data *sdata = local->scan_sdata;

        for (i = 0; i < local->scan_req->n_ssids; i++)
                ieee80211_send_probe_req(
                        sdata, NULL,
                        local->scan_req->ssids[i].ssid,
                        local->scan_req->ssids[i].ssid_len,
                        local->scan_req->ie, local->scan_req->ie_len);

        /*
         * After sending probe requests, wait for probe responses
         * on the channel.
         */
        *next_delay = IEEE80211_CHANNEL_TIME;
        local->next_scan_state = SCAN_DECISION;
}

void ieee80211_scan_work(struct work_struct *work)
{
        struct ieee80211_local *local =
                container_of(work, struct ieee80211_local, scan_work.work);
        struct ieee80211_sub_if_data *sdata = local->scan_sdata;
        unsigned long next_delay = 0;

        mutex_lock(&local->scan_mtx);
        if (!sdata || !local->scan_req) {
                mutex_unlock(&local->scan_mtx);
                return;
        }

        if (local->scan_req && !local->scanning) {
                struct cfg80211_scan_request *req = local->scan_req;
                int rc;

                local->scan_req = NULL;
                local->scan_sdata = NULL;

                rc = __ieee80211_start_scan(sdata, req);
                mutex_unlock(&local->scan_mtx);

                if (rc)
                        ieee80211_scan_completed(&local->hw, true);
                return;
        }

        mutex_unlock(&local->scan_mtx);

        /*
         * Avoid re-scheduling when the sdata is going away.
         */
        if (!netif_running(sdata->dev)) {
                ieee80211_scan_completed(&local->hw, true);
                return;
        }

        /*
         * as long as no delay is required advance immediately
         * without scheduling a new work
         */
        do {
                switch (local->next_scan_state) {
                case SCAN_DECISION:
                        if (ieee80211_scan_state_decision(local, &next_delay))
                                return;
                        break;
                case SCAN_SET_CHANNEL:
                        ieee80211_scan_state_set_channel(local, &next_delay);
                        break;
                case SCAN_SEND_PROBE:
                        ieee80211_scan_state_send_probe(local, &next_delay);
                        break;
                case SCAN_LEAVE_OPER_CHANNEL:
                        ieee80211_scan_state_leave_oper_channel(local, &next_delay);
                        break;
                case SCAN_ENTER_OPER_CHANNEL:
                        ieee80211_scan_state_enter_oper_channel(local, &next_delay);
                        break;
                }
        } while (next_delay == 0);

        ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
}

int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
                           struct cfg80211_scan_request *req)
{
        int res;

        mutex_lock(&sdata->local->scan_mtx);
        res = __ieee80211_start_scan(sdata, req);
        mutex_unlock(&sdata->local->scan_mtx);

        return res;
}

int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
                                    const u8 *ssid, u8 ssid_len)
{
        struct ieee80211_local *local = sdata->local;
        int ret = -EBUSY;

        mutex_lock(&local->scan_mtx);

        /* busy scanning */
        if (local->scan_req)
                goto unlock;

        memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
        local->int_scan_req->ssids[0].ssid_len = ssid_len;

        ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
 unlock:
        mutex_unlock(&local->scan_mtx);
        return ret;
}

void ieee80211_scan_cancel(struct ieee80211_local *local)
{
        bool abortscan;

        cancel_delayed_work_sync(&local->scan_work);

        /*
         * Only call this function when a scan can't be
         * queued -- mostly at suspend under RTNL.
         */
        mutex_lock(&local->scan_mtx);
        abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) ||
                    (!local->scanning && local->scan_req);
        mutex_unlock(&local->scan_mtx);

        if (abortscan)
                ieee80211_scan_completed(&local->hw, true);
}