net/mac80211/scan.c

   1 /*
   2  * Scanning implementation
   3  *
   4  * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
   5  * Copyright 2004, Instant802 Networks, Inc.
   6  * Copyright 2005, Devicescape Software, Inc.
   7  * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
   8  * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  */
  14
  15 /* TODO: figure out how to avoid that the "current BSS" expires */
  16
  17 #include <linux/wireless.h>
  18 #include <linux/if_arp.h>
  19 #include <linux/rtnetlink.h>
  20 #include <net/mac80211.h>
  21 #include <net/iw_handler.h>
  22
  23 #include "ieee80211_i.h"
  24 #include "mesh.h"
  25
  26 #define IEEE80211_PROBE_DELAY (HZ / 33)
  27 #define IEEE80211_CHANNEL_TIME (HZ / 33)
  28 #define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 5)
  29
  30 struct ieee80211_bss *
  31 ieee80211_rx_bss_get(struct ieee80211_local *local, u8 *bssid, int freq,
  32                      u8 *ssid, u8 ssid_len)
  33 {
  34         return (void *)cfg80211_get_bss(local->hw.wiphy,
  35                                         ieee80211_get_channel(local->hw.wiphy,
  36                                                               freq),
  37                                         bssid, ssid, ssid_len,
  38                                         0, 0);
  39 }
  40
  41 static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
  42 {
  43         struct ieee80211_bss *bss = (void *)cbss;
  44
  45         kfree(bss_mesh_id(bss));
  46         kfree(bss_mesh_cfg(bss));
  47 }
  48
  49 void ieee80211_rx_bss_put(struct ieee80211_local *local,
  50                           struct ieee80211_bss *bss)
  51 {
  52         cfg80211_put_bss((struct cfg80211_bss *)bss);
  53 }
  54
  55 struct ieee80211_bss *
  56 ieee80211_bss_info_update(struct ieee80211_local *local,
  57                           struct ieee80211_rx_status *rx_status,
  58                           struct ieee80211_mgmt *mgmt,
  59                           size_t len,
  60                           struct ieee802_11_elems *elems,
  61                           struct ieee80211_channel *channel,
  62                           bool beacon)
  63 {
  64         struct ieee80211_bss *bss;
  65         int clen;
  66         s32 signal = 0;
  67
  68         if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
  69                 signal = rx_status->signal * 100;
  70         else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
  71                 signal = (rx_status->signal * 100) / local->hw.max_signal;
  72
  73         bss = (void *)cfg80211_inform_bss_frame(local->hw.wiphy, channel,
  74                                                 mgmt, len, signal, GFP_ATOMIC);
  75
  76         if (!bss)
  77                 return NULL;
  78
  79         bss->cbss.free_priv = ieee80211_rx_bss_free;
  80
  81         /* save the ERP value so that it is available at association time */
  82         if (elems->erp_info && elems->erp_info_len >= 1) {
  83                 bss->erp_value = elems->erp_info[0];
  84                 bss->has_erp_value = 1;
  85         }
  86
  87         if (elems->tim) {
  88                 struct ieee80211_tim_ie *tim_ie =
  89                         (struct ieee80211_tim_ie *)elems->tim;
  90                 bss->dtim_period = tim_ie->dtim_period;
  91         }
  92
  93         /* set default value for buggy APs */
  94         if (!elems->tim || bss->dtim_period == 0)
  95                 bss->dtim_period = 1;
  96
  97         bss->supp_rates_len = 0;
  98         if (elems->supp_rates) {
  99                 clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
 100                 if (clen > elems->supp_rates_len)
 101                         clen = elems->supp_rates_len;
 102                 memcpy(&bss->supp_rates[bss->supp_rates_len], elems->supp_rates,
 103                        clen);
 104                 bss->supp_rates_len += clen;
 105         }
 106         if (elems->ext_supp_rates) {
 107                 clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
 108                 if (clen > elems->ext_supp_rates_len)
 109                         clen = elems->ext_supp_rates_len;
 110                 memcpy(&bss->supp_rates[bss->supp_rates_len],
 111                        elems->ext_supp_rates, clen);
 112                 bss->supp_rates_len += clen;
 113         }
 114
 115         bss->wmm_used = elems->wmm_param || elems->wmm_info;
 116
 117         if (!beacon)
 118                 bss->last_probe_resp = jiffies;
 119
 120         return bss;
 121 }
 122
 123 void ieee80211_rx_bss_remove(struct ieee80211_sub_if_data *sdata, u8 *bssid,
 124                              int freq, u8 *ssid, u8 ssid_len)
 125 {
 126         struct ieee80211_bss *bss;
 127         struct ieee80211_local *local = sdata->local;
 128
 129         bss = ieee80211_rx_bss_get(local, bssid, freq, ssid, ssid_len);
 130         if (bss) {
 131                 cfg80211_unlink_bss(local->hw.wiphy, (void *)bss);
 132                 ieee80211_rx_bss_put(local, bss);
 133         }
 134 }
 135
 136 ieee80211_rx_result
 137 ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb,
 138                   struct ieee80211_rx_status *rx_status)
 139 {
 140         struct ieee80211_mgmt *mgmt;
 141         struct ieee80211_bss *bss;
 142         u8 *elements;
 143         struct ieee80211_channel *channel;
 144         size_t baselen;
 145         int freq;
 146         __le16 fc;
 147         bool presp, beacon = false;
 148         struct ieee802_11_elems elems;
 149
 150         if (skb->len < 2)
 151                 return RX_DROP_UNUSABLE;
 152
 153         mgmt = (struct ieee80211_mgmt *) skb->data;
 154         fc = mgmt->frame_control;
 155
 156         if (ieee80211_is_ctl(fc))
 157                 return RX_CONTINUE;
 158
 159         if (skb->len < 24)
 160                 return RX_DROP_MONITOR;
 161
 162         presp = ieee80211_is_probe_resp(fc);
 163         if (presp) {
 164                 /* ignore ProbeResp to foreign address */
 165                 if (memcmp(mgmt->da, sdata->dev->dev_addr, ETH_ALEN))
 166                         return RX_DROP_MONITOR;
 167
 168                 presp = true;
 169                 elements = mgmt->u.probe_resp.variable;
 170                 baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
 171         } else {
 172                 beacon = ieee80211_is_beacon(fc);
 173                 baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
 174                 elements = mgmt->u.beacon.variable;
 175         }
 176
 177         if (!presp && !beacon)
 178                 return RX_CONTINUE;
 179
 180         if (baselen > skb->len)
 181                 return RX_DROP_MONITOR;
 182
 183         ieee802_11_parse_elems(elements, skb->len - baselen, &elems);
 184
 185         if (elems.ds_params && elems.ds_params_len == 1)
 186                 freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
 187         else
 188                 freq = rx_status->freq;
 189
 190         channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);
 191
 192         if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
 193                 return RX_DROP_MONITOR;
 194
 195         bss = ieee80211_bss_info_update(sdata->local, rx_status,
 196                                         mgmt, skb->len, &elems,
 197                                         channel, beacon);
 198         if (bss)
 199                 ieee80211_rx_bss_put(sdata->local, bss);
 200
 201         dev_kfree_skb(skb);
 202         return RX_QUEUED;
 203 }
 204
 205 /*
 206  * inform AP that we will go to sleep so that it will buffer the frames
 207  * while we scan
 208  */
 209 static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
 210 {
 211         struct ieee80211_local *local = sdata->local;
 212         bool ps = false;
 213
 214         /* FIXME: what to do when local->pspolling is true? */
 215
 216         del_timer_sync(&local->dynamic_ps_timer);
 217         cancel_work_sync(&local->dynamic_ps_enable_work);
 218
 219         if (local->hw.conf.flags & IEEE80211_CONF_PS) {
 220                 ps = true;
 221                 local->hw.conf.flags &= ~IEEE80211_CONF_PS;
 222                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 223         }
 224
 225         if (!ps || !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
 226                 /*
 227                  * If power save was enabled, no need to send a nullfunc
 228                  * frame because AP knows that we are sleeping. But if the
 229                  * hardware is creating the nullfunc frame for power save
 230                  * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
 231                  * enabled) and power save was enabled, the firmware just
 232                  * sent a null frame with power save disabled. So we need
 233                  * to send a new nullfunc frame to inform the AP that we
 234                  * are again sleeping.
 235                  */
 236                 ieee80211_send_nullfunc(local, sdata, 1);
 237 }
 238
 239 /* inform AP that we are awake again, unless power save is enabled */
 240 static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
 241 {
 242         struct ieee80211_local *local = sdata->local;
 243
 244         if (!local->ps_sdata)
 245                 ieee80211_send_nullfunc(local, sdata, 0);
 246         else {
 247                 /*
 248                  * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
 249                  * will send a nullfunc frame with the powersave bit set
 250                  * even though the AP already knows that we are sleeping.
 251                  * This could be avoided by sending a null frame with power
 252                  * save bit disabled before enabling the power save, but
 253                  * this doesn't gain anything.
 254                  *
 255                  * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
 256                  * to send a nullfunc frame because AP already knows that
 257                  * we are sleeping, let's just enable power save mode in
 258                  * hardware.
 259                  */
 260                 local->hw.conf.flags |= IEEE80211_CONF_PS;
 261                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 262         }
 263 }
 264
 265 static void ieee80211_restore_scan_ies(struct ieee80211_local *local)
 266 {
 267         kfree(local->scan_req->ie);
 268         local->scan_req->ie = local->orig_ies;
 269         local->scan_req->ie_len = local->orig_ies_len;
 270 }
 271
 272 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 273 {
 274         struct ieee80211_local *local = hw_to_local(hw);
 275         struct ieee80211_sub_if_data *sdata;
 276         bool was_hw_scan;
 277
 278         mutex_lock(&local->scan_mtx);
 279
 280         if (WARN_ON(!local->hw_scanning && !local->sw_scanning)) {
 281                 mutex_unlock(&local->scan_mtx);
 282                 return;
 283         }
 284
 285         if (WARN_ON(!local->scan_req)) {
 286                 mutex_unlock(&local->scan_mtx);
 287                 return;
 288         }
 289
 290         if (local->hw_scanning)
 291                 ieee80211_restore_scan_ies(local);
 292
 293         if (local->scan_req != &local->int_scan_req)
 294                 cfg80211_scan_done(local->scan_req, aborted);
 295         local->scan_req = NULL;
 296
 297         was_hw_scan = local->hw_scanning;
 298         local->hw_scanning = false;
 299         local->sw_scanning = false;
 300
 301         /* we only have to protect scan_req and hw/sw scan */
 302         mutex_unlock(&local->scan_mtx);
 303
 304         if (was_hw_scan) {
 305                 /*
 306                  * Somebody might have requested channel change during scan
 307                  * that we won't have acted upon, try now. ieee80211_hw_config
 308                  * will set the flag based on actual changes.
 309                  */
 310                 ieee80211_hw_config(local, 0);
 311                 goto done;
 312         }
 313
 314         ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 315
 316         netif_tx_lock_bh(local->mdev);
 317         netif_addr_lock(local->mdev);
 318         local->filter_flags &= ~FIF_BCN_PRBRESP_PROMISC;
 319         local->ops->configure_filter(local_to_hw(local),
 320                                      FIF_BCN_PRBRESP_PROMISC,
 321                                      &local->filter_flags,
 322                                      local->mdev->mc_count,
 323                                      local->mdev->mc_list);
 324
 325         netif_addr_unlock(local->mdev);
 326         netif_tx_unlock_bh(local->mdev);
 327
 328         if (local->ops->sw_scan_complete)
 329                 local->ops->sw_scan_complete(local_to_hw(local));
 330
 331         mutex_lock(&local->iflist_mtx);
 332         list_for_each_entry(sdata, &local->interfaces, list) {
 333                 if (!netif_running(sdata->dev))
 334                         continue;
 335
 336                 /* Tell AP we're back */
 337                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 338                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
 339                                 ieee80211_scan_ps_disable(sdata);
 340                                 netif_tx_wake_all_queues(sdata->dev);
 341                         }
 342                 } else
 343                         netif_tx_wake_all_queues(sdata->dev);
 344
 345                 /* re-enable beaconing */
 346                 if (sdata->vif.type == NL80211_IFTYPE_AP ||
 347                     sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 348                     sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 349                         ieee80211_bss_info_change_notify(
 350                                 sdata, BSS_CHANGED_BEACON_ENABLED);
 351         }
 352         mutex_unlock(&local->iflist_mtx);
 353
 354  done:
 355         ieee80211_mlme_notify_scan_completed(local);
 356         ieee80211_ibss_notify_scan_completed(local);
 357         ieee80211_mesh_notify_scan_completed(local);
 358 }
 359 EXPORT_SYMBOL(ieee80211_scan_completed);
 360
 361 static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 362 {
 363         struct ieee80211_sub_if_data *sdata;
 364
 365         /*
 366          * Hardware/driver doesn't support hw_scan, so use software
 367          * scanning instead. First send a nullfunc frame with power save
 368          * bit on so that AP will buffer the frames for us while we are not
 369          * listening, then send probe requests to each channel and wait for
 370          * the responses. After all channels are scanned, tune back to the
 371          * original channel and send a nullfunc frame with power save bit
 372          * off to trigger the AP to send us all the buffered frames.
 373          *
 374          * Note that while local->sw_scanning is true everything else but
 375          * nullfunc frames and probe requests will be dropped in
 376          * ieee80211_tx_h_check_assoc().
 377          */
 378         if (local->ops->sw_scan_start)
 379                 local->ops->sw_scan_start(local_to_hw(local));
 380
 381         mutex_lock(&local->iflist_mtx);
 382         list_for_each_entry(sdata, &local->interfaces, list) {
 383                 if (!netif_running(sdata->dev))
 384                         continue;
 385
 386                 /* disable beaconing */
 387                 if (sdata->vif.type == NL80211_IFTYPE_AP ||
 388                     sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 389                     sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 390                         ieee80211_bss_info_change_notify(
 391                                 sdata, BSS_CHANGED_BEACON_ENABLED);
 392
 393                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 394                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
 395                                 netif_tx_stop_all_queues(sdata->dev);
 396                                 ieee80211_scan_ps_enable(sdata);
 397                         }
 398                 } else
 399                         netif_tx_stop_all_queues(sdata->dev);
 400         }
 401         mutex_unlock(&local->iflist_mtx);
 402
 403         local->scan_state = SCAN_SET_CHANNEL;
 404         local->scan_channel_idx = 0;
 405
 406         netif_addr_lock_bh(local->mdev);
 407         local->filter_flags |= FIF_BCN_PRBRESP_PROMISC;
 408         local->ops->configure_filter(local_to_hw(local),
 409                                      FIF_BCN_PRBRESP_PROMISC,
 410                                      &local->filter_flags,
 411                                      local->mdev->mc_count,
 412                                      local->mdev->mc_list);
 413         netif_addr_unlock_bh(local->mdev);
 414
 415         /* TODO: start scan as soon as all nullfunc frames are ACKed */
 416         queue_delayed_work(local->hw.workqueue, &local->scan_work,
 417                            IEEE80211_CHANNEL_TIME);
 418
 419         return 0;
 420 }
 421
 422
 423 static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 424                                   struct cfg80211_scan_request *req)
 425 {
 426         struct ieee80211_local *local = sdata->local;
 427         struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 428         int rc;
 429
 430         if (local->scan_req)
 431                 return -EBUSY;
 432
 433         if (local->ops->hw_scan) {
 434                 u8 *ies;
 435                 int ielen;
 436
 437                 ies = kmalloc(2 + IEEE80211_MAX_SSID_LEN +
 438                               local->scan_ies_len + req->ie_len, GFP_KERNEL);
 439                 if (!ies)
 440                         return -ENOMEM;
 441
 442                 ielen = ieee80211_build_preq_ies(local, ies,
 443                                                  req->ie, req->ie_len);
 444                 local->orig_ies = req->ie;
 445                 local->orig_ies_len = req->ie_len;
 446                 req->ie = ies;
 447                 req->ie_len = ielen;
 448         }
 449
 450         local->scan_req = req;
 451         local->scan_sdata = sdata;
 452
 453         if (req != &local->int_scan_req &&
 454             sdata->vif.type == NL80211_IFTYPE_STATION &&
 455             (ifmgd->state == IEEE80211_STA_MLME_DIRECT_PROBE ||
 456              ifmgd->state == IEEE80211_STA_MLME_AUTHENTICATE ||
 457              ifmgd->state == IEEE80211_STA_MLME_ASSOCIATE)) {
 458                 /* actually wait for the assoc to finish/time out */
 459                 set_bit(IEEE80211_STA_REQ_SCAN, &ifmgd->request);
 460                 return 0;
 461         }
 462
 463         if (local->ops->hw_scan)
 464                 local->hw_scanning = true;
 465         else
 466                 local->sw_scanning = true;
 467         /*
 468          * Kicking off the scan need not be protected,
 469          * only the scan variable stuff, since now
 470          * local->scan_req is assigned and other callers
 471          * will abort their scan attempts.
 472          *
 473          * This avoids getting a scan_mtx -> iflist_mtx
 474          * dependency, so that the scan completed calls
 475          * have more locking freedom.
 476          */
 477         mutex_unlock(&local->scan_mtx);
 478
 479         if (local->ops->hw_scan)
 480                 rc = local->ops->hw_scan(local_to_hw(local),
 481                                          local->scan_req);
 482         else
 483                 rc = ieee80211_start_sw_scan(local);
 484
 485         mutex_lock(&local->scan_mtx);
 486
 487         if (rc) {
 488                 if (local->ops->hw_scan) {
 489                         local->hw_scanning = false;
 490                         ieee80211_restore_scan_ies(local);
 491                 } else
 492                         local->sw_scanning = false;
 493
 494                 local->scan_req = NULL;
 495                 local->scan_sdata = NULL;
 496         }
 497
 498         return rc;
 499 }
 500
 501 void ieee80211_scan_work(struct work_struct *work)
 502 {
 503         struct ieee80211_local *local =
 504                 container_of(work, struct ieee80211_local, scan_work.work);
 505         struct ieee80211_sub_if_data *sdata = local->scan_sdata;
 506         struct ieee80211_channel *chan;
 507         int skip, i;
 508         unsigned long next_delay = 0;
 509
 510         mutex_lock(&local->scan_mtx);
 511         if (!sdata || !local->scan_req) {
 512                 mutex_unlock(&local->scan_mtx);
 513                 return;
 514         }
 515
 516         if (local->scan_req && !(local->sw_scanning || local->hw_scanning)) {
 517                 struct cfg80211_scan_request *req = local->scan_req;
 518                 int rc;
 519
 520                 local->scan_req = NULL;
 521
 522                 rc = __ieee80211_start_scan(sdata, req);
 523                 mutex_unlock(&local->scan_mtx);
 524
 525                 if (rc)
 526                         ieee80211_scan_completed(&local->hw, true);
 527                 return;
 528         }
 529
 530         mutex_unlock(&local->scan_mtx);
 531
 532         /*
 533          * Avoid re-scheduling when the sdata is going away.
 534          */
 535         if (!netif_running(sdata->dev)) {
 536                 ieee80211_scan_completed(&local->hw, true);
 537                 return;
 538         }
 539
 540         switch (local->scan_state) {
 541         case SCAN_SET_CHANNEL:
 542                 /* if no more bands/channels left, complete scan */
 543                 if (local->scan_channel_idx >= local->scan_req->n_channels) {
 544                         ieee80211_scan_completed(&local->hw, false);
 545                         return;
 546                 }
 547                 skip = 0;
 548                 chan = local->scan_req->channels[local->scan_channel_idx];
 549
 550                 if (chan->flags & IEEE80211_CHAN_DISABLED ||
 551                     (sdata->vif.type == NL80211_IFTYPE_ADHOC &&
 552                      chan->flags & IEEE80211_CHAN_NO_IBSS))
 553                         skip = 1;
 554
 555                 if (!skip) {
 556                         local->scan_channel = chan;
 557                         if (ieee80211_hw_config(local,
 558                                                 IEEE80211_CONF_CHANGE_CHANNEL))
 559                                 skip = 1;
 560                 }
 561
 562                 /* advance state machine to next channel/band */
 563                 local->scan_channel_idx++;
 564
 565                 if (skip)
 566                         break;
 567
 568                 next_delay = IEEE80211_PROBE_DELAY +
 569                              usecs_to_jiffies(local->hw.channel_change_time);
 570                 local->scan_state = SCAN_SEND_PROBE;
 571                 break;
 572         case SCAN_SEND_PROBE:
 573                 next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 574                 local->scan_state = SCAN_SET_CHANNEL;
 575
 576                 if (local->scan_channel->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
 577                     !local->scan_req->n_ssids)
 578                         break;
 579                 for (i = 0; i < local->scan_req->n_ssids; i++)
 580                         ieee80211_send_probe_req(
 581                                 sdata, NULL,
 582                                 local->scan_req->ssids[i].ssid,
 583                                 local->scan_req->ssids[i].ssid_len,
 584                                 local->scan_req->ie, local->scan_req->ie_len);
 585                 next_delay = IEEE80211_CHANNEL_TIME;
 586                 break;
 587         }
 588
 589         queue_delayed_work(local->hw.workqueue, &local->scan_work,
 590                            next_delay);
 591 }
 592
 593 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 594                            struct cfg80211_scan_request *req)
 595 {
 596         int res;
 597
 598         mutex_lock(&sdata->local->scan_mtx);
 599         res = __ieee80211_start_scan(sdata, req);
 600         mutex_unlock(&sdata->local->scan_mtx);
 601
 602         return res;
 603 }
 604
 605 int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
 606                                     const u8 *ssid, u8 ssid_len)
 607 {
 608         struct ieee80211_local *local = sdata->local;
 609         int ret = -EBUSY;
 610
 611         mutex_lock(&local->scan_mtx);
 612
 613         /* busy scanning */
 614         if (local->scan_req)
 615                 goto unlock;
 616
 617         memcpy(local->int_scan_req.ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
 618         local->int_scan_req.ssids[0].ssid_len = ssid_len;
 619
 620         ret = __ieee80211_start_scan(sdata, &sdata->local->int_scan_req);
 621  unlock:
 622         mutex_unlock(&local->scan_mtx);
 623         return ret;
 624 }