- 根目录:
- 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.
*/
#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <linux/pm_qos_params.h>
#include <net/sch_generic.h>
#include <linux/slab.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)
{
struct cfg80211_bss *cbss;
cbss = cfg80211_get_bss(local->hw.wiphy,
ieee80211_get_channel(local->hw.wiphy, freq),
bssid, ssid, ssid_len, 0, 0);
if (!cbss)
return NULL;
return (void *)cbss->priv;
}
static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
{
struct ieee80211_bss *bss = (void *)cbss->priv;
kfree(bss_mesh_id(bss));
kfree(bss_mesh_cfg(bss));
}
void ieee80211_rx_bss_put(struct ieee80211_local *local,
struct ieee80211_bss *bss)
{
if (!bss)
return;
cfg80211_put_bss(container_of((void *)bss, struct cfg80211_bss, priv));
}
static bool is_uapsd_supported(struct ieee802_11_elems *elems)
{
u8 qos_info;
if (elems->wmm_info && elems->wmm_info_len == 7
&& elems->wmm_info[5] == 1)
qos_info = elems->wmm_info[6];
else if (elems->wmm_param && elems->wmm_param_len == 24
&& elems->wmm_param[5] == 1)
qos_info = elems->wmm_param[6];
else
/* no valid wmm information or parameter element found */
return false;
return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
}
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 cfg80211_bss *cbss;
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;
cbss = cfg80211_inform_bss_frame(local->hw.wiphy, channel,
mgmt, len, signal, GFP_ATOMIC);
if (!cbss)
return NULL;
cbss->free_priv = ieee80211_rx_bss_free;
bss = (void *)cbss->priv;
/* 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;
}
/* If the beacon had no TIM IE, or it was invalid, use 1 */
if (beacon && !bss->dtim_period)
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;
bss->uapsd_supported = is_uapsd_supported(elems);
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->vif.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],
rx_status->band);
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);
/* If we are on-operating-channel, and this packet is for the
* current channel, pass the pkt on up the stack so that
* the rest of the stack can make use of it.
*/
if (ieee80211_cfg_on_oper_channel(sdata->local)
&& (channel == sdata->local->oper_channel))
return RX_CONTINUE;
dev_kfree_skb(skb);
return RX_QUEUED;
}
/* return false if no more work */
static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
{
struct cfg80211_scan_request *req = local->scan_req;
enum ieee80211_band band;
int i, ielen, n_chans;
do {
if (local->hw_scan_band == IEEE80211_NUM_BANDS)
return false;
band = local->hw_scan_band;
n_chans = 0;
for (i = 0; i < req->n_channels; i++) {
if (req->channels[i]->band == band) {
local->hw_scan_req->channels[n_chans] =
req->channels[i];
n_chans++;
}
}
local->hw_scan_band++;
} while (!n_chans);
local->hw_scan_req->n_channels = n_chans;
ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
req->ie, req->ie_len, band, (u32) -1,
0);
local->hw_scan_req->ie_len = ielen;
return true;
}
static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
bool was_hw_scan)
{
struct ieee80211_local *local = hw_to_local(hw);
bool on_oper_chan;
bool enable_beacons = false;
lockdep_assert_held(&local->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))
return;
if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
int rc = drv_hw_scan(local, local->scan_sdata, local->hw_scan_req);
if (rc == 0)
return;
}
kfree(local->hw_scan_req);
local->hw_scan_req = NULL;
if (local->scan_req != local->int_scan_req)
cfg80211_scan_done(local->scan_req, aborted);
local->scan_req = NULL;
local->scan_sdata = NULL;
local->scanning = 0;
local->scan_channel = NULL;
on_oper_chan = ieee80211_cfg_on_oper_channel(local);
if (was_hw_scan || !on_oper_chan)
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
else
/* Set power back to normal operating levels. */
ieee80211_hw_config(local, 0);
if (!was_hw_scan) {
bool on_oper_chan2;
ieee80211_configure_filter(local);
drv_sw_scan_complete(local);
on_oper_chan2 = ieee80211_cfg_on_oper_channel(local);
/* We should always be on-channel at this point. */
WARN_ON(!on_oper_chan2);
if (on_oper_chan2 && (on_oper_chan != on_oper_chan2))
enable_beacons = true;
ieee80211_offchannel_return(local, enable_beacons, true);
}
ieee80211_recalc_idle(local);
ieee80211_mlme_notify_scan_completed(local);
ieee80211_ibss_notify_scan_completed(local);
ieee80211_mesh_notify_scan_completed(local);
ieee80211_queue_work(&local->hw, &local->work_work);
}
void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
{
struct ieee80211_local *local = hw_to_local(hw);
trace_api_scan_completed(local, aborted);
set_bit(SCAN_COMPLETED, &local->scanning);
if (aborted)
set_bit(SCAN_ABORTED, &local->scanning);
ieee80211_queue_delayed_work(&local->hw, &local->scan_work, 0);
}
EXPORT_SYMBOL(ieee80211_scan_completed);
static int ieee80211_start_sw_scan(struct ieee80211_local *local)
{
/*
* 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);
local->leave_oper_channel_time = 0;
local->next_scan_state = SCAN_DECISION;
local->scan_channel_idx = 0;
/* We always want to use off-channel PS, even if we
* are not really leaving oper-channel. Don't
* tell the AP though, as long as we are on-channel.
*/
ieee80211_offchannel_enable_all_ps(local, false);
ieee80211_configure_filter(local);
/* We need to set power level at maximum rate for scanning. */
ieee80211_hw_config(local, 0);
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;
int rc;
lockdep_assert_held(&local->mtx);
if (local->scan_req)
return -EBUSY;
if (!list_empty(&local->work_list)) {
/* wait for the work to finish/time out */
local->scan_req = req;
local->scan_sdata = sdata;
return 0;
}
if (local->ops->hw_scan) {
u8 *ies;
local->hw_scan_req = kmalloc(
sizeof(*local->hw_scan_req) +
req->n_channels * sizeof(req->channels[0]) +
2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
req->ie_len, GFP_KERNEL);
if (!local->hw_scan_req)
return -ENOMEM;
local->hw_scan_req->ssids = req->ssids;
local->hw_scan_req->n_ssids = req->n_ssids;
ies = (u8 *)local->hw_scan_req +
sizeof(*local->hw_scan_req) +
req->n_channels * sizeof(req->channels[0]);
local->hw_scan_req->ie = ies;
local->hw_scan_band = 0;
/*
* After allocating local->hw_scan_req, we must
* go through until ieee80211_prep_hw_scan(), so
* anything that might be changed here and leave
* this function early must not go after this
* allocation.
*/
}
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);
ieee80211_recalc_idle(local);
if (local->ops->hw_scan) {
WARN_ON(!ieee80211_prep_hw_scan(local));
rc = drv_hw_scan(local, sdata, local->hw_scan_req);
} else
rc = ieee80211_start_sw_scan(local);
if (rc) {
kfree(local->hw_scan_req);
local->hw_scan_req = NULL;
local->scanning = 0;
ieee80211_recalc_idle(local);
local->scan_req = NULL;
local->scan_sdata = NULL;
}
return rc;
}
static unsigned long
ieee80211_scan_get_channel_time(struct ieee80211_channel *chan)
{
/*
* TODO: channel switching also consumes quite some time,
* add that delay as well to get a better estimation
*/
if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN)
return IEEE80211_PASSIVE_CHANNEL_TIME;
return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
}
static void ieee80211_scan_state_decision(struct ieee80211_local *local,
unsigned long *next_delay)
{
bool associated = false;
bool tx_empty = true;
bool bad_latency;
bool listen_int_exceeded;
unsigned long min_beacon_int = 0;
struct ieee80211_sub_if_data *sdata;
struct ieee80211_channel *next_chan;
/*
* check if at least one STA interface is associated,
* check if at least one STA interface has pending tx frames
* and grab the lowest used beacon interval
*/
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
if (!ieee80211_sdata_running(sdata))
continue;
if (sdata->vif.type == NL80211_IFTYPE_STATION) {
if (sdata->u.mgd.associated) {
associated = true;
if (sdata->vif.bss_conf.beacon_int <
min_beacon_int || min_beacon_int == 0)
min_beacon_int =
sdata->vif.bss_conf.beacon_int;
if (!qdisc_all_tx_empty(sdata->dev)) {
tx_empty = false;
break;
}
}
}
}
mutex_unlock(&local->iflist_mtx);
next_chan = local->scan_req->channels[local->scan_channel_idx];
if (ieee80211_cfg_on_oper_channel(local)) {
/* We're currently on operating channel. */
if (next_chan == local->oper_channel)
/* We don't need to move off of operating channel. */
local->next_scan_state = SCAN_SET_CHANNEL;
else
/*
* We do need to leave operating channel, as next
* scan is somewhere else.
*/
local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
} else {
/*
* we're currently scanning a different channel, let's
* see if we can scan another channel without interfering
* with the current traffic situation.
*
* Since we don't know if the AP has pending frames for us
* we can only check for our tx queues and use the current
* pm_qos requirements for rx. Hence, if no tx traffic occurs
* at all we will scan as many channels in a row as the pm_qos
* latency allows us to. Additionally we also check for the
* currently negotiated listen interval to prevent losing
* frames unnecessarily.
*
* Otherwise switch back to the operating channel.
*/
bad_latency = time_after(jiffies +
ieee80211_scan_get_channel_time(next_chan),
local->leave_oper_channel_time +
usecs_to_jiffies(pm_qos_request(PM_QOS_NETWORK_LATENCY)));
listen_int_exceeded = time_after(jiffies +
ieee80211_scan_get_channel_time(next_chan),
local->leave_oper_channel_time +
usecs_to_jiffies(min_beacon_int * 1024) *
local->hw.conf.listen_interval);
if (associated && ( !tx_empty || bad_latency ||
listen_int_exceeded))
local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
else
local->next_scan_state = SCAN_SET_CHANNEL;
}
*next_delay = 0;
}
static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
unsigned long *next_delay)
{
/* PS will already be in off-channel mode,
* we do that once at the beginning of scanning.
*/
ieee80211_offchannel_stop_vifs(local, false);
/*
* What if the nullfunc frames didn't arrive?
*/
drv_flush(local, false);
if (local->ops->flush)
*next_delay = 0;
else
*next_delay = HZ / 10;
/* remember when we left the operating channel */
local->leave_oper_channel_time = jiffies;
/* advance to the next channel to be scanned */
local->next_scan_state = SCAN_SET_CHANNEL;
}
static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
unsigned long *next_delay)
{
/* switch back to the operating channel */
local->scan_channel = NULL;
if (!ieee80211_cfg_on_oper_channel(local))
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
/*
* Re-enable vifs and beaconing. Leave PS
* in off-channel state..will put that back
* on-channel at the end of scanning.
*/
ieee80211_offchannel_return(local, true, false);
*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;
skip = 0;
chan = local->scan_req->channels[local->scan_channel_idx];
local->scan_channel = chan;
/* Only call hw-config if we really need to change channels. */
if (chan != local->hw.conf.channel)
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;
unsigned long next_delay = 0;
bool aborted, hw_scan;
mutex_lock(&local->mtx);
sdata = local->scan_sdata;
if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) {
aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
goto out_complete;
}
if (!sdata || !local->scan_req)
goto out;
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);
if (rc) {
/* need to complete scan in cfg80211 */
local->scan_req = req;
aborted = true;
goto out_complete;
} else
goto out;
}
/*
* Avoid re-scheduling when the sdata is going away.
*/
if (!ieee80211_sdata_running(sdata)) {
aborted = true;
goto out_complete;
}
/*
* as long as no delay is required advance immediately
* without scheduling a new work
*/
do {
switch (local->next_scan_state) {
case SCAN_DECISION:
/* if no more bands/channels left, complete scan */
if (local->scan_channel_idx >= local->scan_req->n_channels) {
aborted = false;
goto out_complete;
}
ieee80211_scan_state_decision(local, &next_delay);
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);
goto out;
out_complete:
hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
__ieee80211_scan_completed(&local->hw, aborted, hw_scan);
out:
mutex_unlock(&local->mtx);
}
int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
struct cfg80211_scan_request *req)
{
int res;
mutex_lock(&sdata->local->mtx);
res = __ieee80211_start_scan(sdata, req);
mutex_unlock(&sdata->local->mtx);
return res;
}
int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
const u8 *ssid, u8 ssid_len,
struct ieee80211_channel *chan)
{
struct ieee80211_local *local = sdata->local;
int ret = -EBUSY;
enum ieee80211_band band;
mutex_lock(&local->mtx);
/* busy scanning */
if (local->scan_req)
goto unlock;
/* fill internal scan request */
if (!chan) {
int i, nchan = 0;
for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
if (!local->hw.wiphy->bands[band])
continue;
for (i = 0;
i < local->hw.wiphy->bands[band]->n_channels;
i++) {
local->int_scan_req->channels[nchan] =
&local->hw.wiphy->bands[band]->channels[i];
nchan++;
}
}
local->int_scan_req->n_channels = nchan;
} else {
local->int_scan_req->channels[0] = chan;
local->int_scan_req->n_channels = 1;
}
local->int_scan_req->ssids = &local->scan_ssid;
local->int_scan_req->n_ssids = 1;
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->mtx);
return ret;
}
/*
* Only call this function when a scan can't be queued -- under RTNL.
*/
void ieee80211_scan_cancel(struct ieee80211_local *local)
{
bool abortscan;
/*
* We are only canceling software scan, or deferred scan that was not
* yet really started (see __ieee80211_start_scan ).
*
* Regarding hardware scan:
* - we can not call __ieee80211_scan_completed() as when
* SCAN_HW_SCANNING bit is set this function change
* local->hw_scan_req to operate on 5G band, what race with
* driver which can use local->hw_scan_req
*
* - we can not cancel scan_work since driver can schedule it
* by ieee80211_scan_completed(..., true) to finish scan
*
* Hence low lever driver is responsible for canceling HW scan.
*/
mutex_lock(&local->mtx);
abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning);
if (abortscan) {
/*
* The scan is canceled, but stop work from being pending.
*
* If the work is currently running, it must be blocked on
* the mutex, but we'll set scan_sdata = NULL and it'll
* simply exit once it acquires the mutex.
*/
cancel_delayed_work(&local->scan_work);
/* and clean up */
__ieee80211_scan_completed(&local->hw, true, false);
}
mutex_unlock(&local->mtx);
}