Pileus Git - ~andy/linux/blob - 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 #include <linux/if_arp.h>
  16 #include <linux/rtnetlink.h>
  17 #include <linux/pm_qos_params.h>
  18 #include <net/sch_generic.h>
  19 #include <linux/slab.h>
  20 #include <net/mac80211.h>
  21
  22 #include "ieee80211_i.h"
  23 #include "driver-ops.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 / 8)
  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         struct cfg80211_bss *cbss;
  35
  36         cbss = cfg80211_get_bss(local->hw.wiphy,
  37                                 ieee80211_get_channel(local->hw.wiphy, freq),
  38                                 bssid, ssid, ssid_len, 0, 0);
  39         if (!cbss)
  40                 return NULL;
  41         return (void *)cbss->priv;
  42 }
  43
  44 static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
  45 {
  46         struct ieee80211_bss *bss = (void *)cbss->priv;
  47
  48         kfree(bss_mesh_id(bss));
  49         kfree(bss_mesh_cfg(bss));
  50 }
  51
  52 void ieee80211_rx_bss_put(struct ieee80211_local *local,
  53                           struct ieee80211_bss *bss)
  54 {
  55         if (!bss)
  56                 return;
  57         cfg80211_put_bss(container_of((void *)bss, struct cfg80211_bss, priv));
  58 }
  59
  60 static bool is_uapsd_supported(struct ieee802_11_elems *elems)
  61 {
  62         u8 qos_info;
  63
  64         if (elems->wmm_info && elems->wmm_info_len == 7
  65             && elems->wmm_info[5] == 1)
  66                 qos_info = elems->wmm_info[6];
  67         else if (elems->wmm_param && elems->wmm_param_len == 24
  68                  && elems->wmm_param[5] == 1)
  69                 qos_info = elems->wmm_param[6];
  70         else
  71                 /* no valid wmm information or parameter element found */
  72                 return false;
  73
  74         return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
  75 }
  76
  77 struct ieee80211_bss *
  78 ieee80211_bss_info_update(struct ieee80211_local *local,
  79                           struct ieee80211_rx_status *rx_status,
  80                           struct ieee80211_mgmt *mgmt,
  81                           size_t len,
  82                           struct ieee802_11_elems *elems,
  83                           struct ieee80211_channel *channel,
  84                           bool beacon)
  85 {
  86         struct cfg80211_bss *cbss;
  87         struct ieee80211_bss *bss;
  88         int clen, srlen;
  89         s32 signal = 0;
  90
  91         if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
  92                 signal = rx_status->signal * 100;
  93         else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
  94                 signal = (rx_status->signal * 100) / local->hw.max_signal;
  95
  96         cbss = cfg80211_inform_bss_frame(local->hw.wiphy, channel,
  97                                          mgmt, len, signal, GFP_ATOMIC);
  98
  99         if (!cbss)
 100                 return NULL;
 101
 102         cbss->free_priv = ieee80211_rx_bss_free;
 103         bss = (void *)cbss->priv;
 104
 105         /* save the ERP value so that it is available at association time */
 106         if (elems->erp_info && elems->erp_info_len >= 1) {
 107                 bss->erp_value = elems->erp_info[0];
 108                 bss->has_erp_value = 1;
 109         }
 110
 111         if (elems->tim) {
 112                 struct ieee80211_tim_ie *tim_ie =
 113                         (struct ieee80211_tim_ie *)elems->tim;
 114                 bss->dtim_period = tim_ie->dtim_period;
 115         }
 116
 117         /* If the beacon had no TIM IE, or it was invalid, use 1 */
 118         if (beacon && !bss->dtim_period)
 119                 bss->dtim_period = 1;
 120
 121         /* replace old supported rates if we get new values */
 122         srlen = 0;
 123         if (elems->supp_rates) {
 124                 clen = IEEE80211_MAX_SUPP_RATES;
 125                 if (clen > elems->supp_rates_len)
 126                         clen = elems->supp_rates_len;
 127                 memcpy(bss->supp_rates, elems->supp_rates, clen);
 128                 srlen += clen;
 129         }
 130         if (elems->ext_supp_rates) {
 131                 clen = IEEE80211_MAX_SUPP_RATES - srlen;
 132                 if (clen > elems->ext_supp_rates_len)
 133                         clen = elems->ext_supp_rates_len;
 134                 memcpy(bss->supp_rates + srlen, elems->ext_supp_rates, clen);
 135                 srlen += clen;
 136         }
 137         if (srlen)
 138                 bss->supp_rates_len = srlen;
 139
 140         bss->wmm_used = elems->wmm_param || elems->wmm_info;
 141         bss->uapsd_supported = is_uapsd_supported(elems);
 142
 143         if (!beacon)
 144                 bss->last_probe_resp = jiffies;
 145
 146         return bss;
 147 }
 148
 149 ieee80211_rx_result
 150 ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
 151 {
 152         struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
 153         struct ieee80211_mgmt *mgmt;
 154         struct ieee80211_bss *bss;
 155         u8 *elements;
 156         struct ieee80211_channel *channel;
 157         size_t baselen;
 158         int freq;
 159         __le16 fc;
 160         bool presp, beacon = false;
 161         struct ieee802_11_elems elems;
 162
 163         if (skb->len < 2)
 164                 return RX_DROP_UNUSABLE;
 165
 166         mgmt = (struct ieee80211_mgmt *) skb->data;
 167         fc = mgmt->frame_control;
 168
 169         if (ieee80211_is_ctl(fc))
 170                 return RX_CONTINUE;
 171
 172         if (skb->len < 24)
 173                 return RX_DROP_MONITOR;
 174
 175         presp = ieee80211_is_probe_resp(fc);
 176         if (presp) {
 177                 /* ignore ProbeResp to foreign address */
 178                 if (memcmp(mgmt->da, sdata->vif.addr, ETH_ALEN))
 179                         return RX_DROP_MONITOR;
 180
 181                 presp = true;
 182                 elements = mgmt->u.probe_resp.variable;
 183                 baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
 184         } else {
 185                 beacon = ieee80211_is_beacon(fc);
 186                 baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
 187                 elements = mgmt->u.beacon.variable;
 188         }
 189
 190         if (!presp && !beacon)
 191                 return RX_CONTINUE;
 192
 193         if (baselen > skb->len)
 194                 return RX_DROP_MONITOR;
 195
 196         ieee802_11_parse_elems(elements, skb->len - baselen, &elems);
 197
 198         if (elems.ds_params && elems.ds_params_len == 1)
 199                 freq = ieee80211_channel_to_frequency(elems.ds_params[0],
 200                                                       rx_status->band);
 201         else
 202                 freq = rx_status->freq;
 203
 204         channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);
 205
 206         if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
 207                 return RX_DROP_MONITOR;
 208
 209         bss = ieee80211_bss_info_update(sdata->local, rx_status,
 210                                         mgmt, skb->len, &elems,
 211                                         channel, beacon);
 212         if (bss)
 213                 ieee80211_rx_bss_put(sdata->local, bss);
 214
 215         /* If we are on-operating-channel, and this packet is for the
 216          * current channel, pass the pkt on up the stack so that
 217          * the rest of the stack can make use of it.
 218          */
 219         if (ieee80211_cfg_on_oper_channel(sdata->local)
 220             && (channel == sdata->local->oper_channel))
 221                 return RX_CONTINUE;
 222
 223         dev_kfree_skb(skb);
 224         return RX_QUEUED;
 225 }
 226
 227 /* return false if no more work */
 228 static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
 229 {
 230         struct cfg80211_scan_request *req = local->scan_req;
 231         enum ieee80211_band band;
 232         int i, ielen, n_chans;
 233
 234         do {
 235                 if (local->hw_scan_band == IEEE80211_NUM_BANDS)
 236                         return false;
 237
 238                 band = local->hw_scan_band;
 239                 n_chans = 0;
 240                 for (i = 0; i < req->n_channels; i++) {
 241                         if (req->channels[i]->band == band) {
 242                                 local->hw_scan_req->channels[n_chans] =
 243                                                         req->channels[i];
 244                                 n_chans++;
 245                         }
 246                 }
 247
 248                 local->hw_scan_band++;
 249         } while (!n_chans);
 250
 251         local->hw_scan_req->n_channels = n_chans;
 252
 253         ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
 254                                          req->ie, req->ie_len, band, (u32) -1,
 255                                          0);
 256         local->hw_scan_req->ie_len = ielen;
 257
 258         return true;
 259 }
 260
 261 static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
 262                                        bool was_hw_scan)
 263 {
 264         struct ieee80211_local *local = hw_to_local(hw);
 265
 266         lockdep_assert_held(&local->mtx);
 267
 268         /*
 269          * It's ok to abort a not-yet-running scan (that
 270          * we have one at all will be verified by checking
 271          * local->scan_req next), but not to complete it
 272          * successfully.
 273          */
 274         if (WARN_ON(!local->scanning && !aborted))
 275                 aborted = true;
 276
 277         if (WARN_ON(!local->scan_req))
 278                 return false;
 279
 280         if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
 281                 int rc = drv_hw_scan(local, local->scan_sdata, local->hw_scan_req);
 282                 if (rc == 0)
 283                         return false;
 284         }
 285
 286         kfree(local->hw_scan_req);
 287         local->hw_scan_req = NULL;
 288
 289         if (local->scan_req != local->int_scan_req)
 290                 cfg80211_scan_done(local->scan_req, aborted);
 291         local->scan_req = NULL;
 292         local->scan_sdata = NULL;
 293
 294         local->scanning = 0;
 295         local->scan_channel = NULL;
 296
 297         return true;
 298 }
 299
 300 static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw,
 301                                               bool was_hw_scan)
 302 {
 303         struct ieee80211_local *local = hw_to_local(hw);
 304         bool on_oper_chan;
 305         bool enable_beacons = false;
 306
 307         mutex_lock(&local->mtx);
 308         on_oper_chan = ieee80211_cfg_on_oper_channel(local);
 309
 310         WARN_ON(local->scanning & (SCAN_SW_SCANNING | SCAN_HW_SCANNING));
 311
 312         if (was_hw_scan || !on_oper_chan) {
 313                 if (WARN_ON(local->scan_channel))
 314                         local->scan_channel = NULL;
 315                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 316         } else
 317                 /* Set power back to normal operating levels. */
 318                 ieee80211_hw_config(local, 0);
 319
 320         if (!was_hw_scan) {
 321                 bool on_oper_chan2;
 322                 ieee80211_configure_filter(local);
 323                 drv_sw_scan_complete(local);
 324                 on_oper_chan2 = ieee80211_cfg_on_oper_channel(local);
 325                 /* We should always be on-channel at this point. */
 326                 WARN_ON(!on_oper_chan2);
 327                 if (on_oper_chan2 && (on_oper_chan != on_oper_chan2))
 328                         enable_beacons = true;
 329
 330                 ieee80211_offchannel_return(local, enable_beacons, true);
 331         }
 332
 333         ieee80211_recalc_idle(local);
 334         mutex_unlock(&local->mtx);
 335
 336         ieee80211_mlme_notify_scan_completed(local);
 337         ieee80211_ibss_notify_scan_completed(local);
 338         ieee80211_mesh_notify_scan_completed(local);
 339         ieee80211_queue_work(&local->hw, &local->work_work);
 340 }
 341
 342 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 343 {
 344         struct ieee80211_local *local = hw_to_local(hw);
 345
 346         trace_api_scan_completed(local, aborted);
 347
 348         set_bit(SCAN_COMPLETED, &local->scanning);
 349         if (aborted)
 350                 set_bit(SCAN_ABORTED, &local->scanning);
 351         ieee80211_queue_delayed_work(&local->hw, &local->scan_work, 0);
 352 }
 353 EXPORT_SYMBOL(ieee80211_scan_completed);
 354
 355 static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 356 {
 357         /*
 358          * Hardware/driver doesn't support hw_scan, so use software
 359          * scanning instead. First send a nullfunc frame with power save
 360          * bit on so that AP will buffer the frames for us while we are not
 361          * listening, then send probe requests to each channel and wait for
 362          * the responses. After all channels are scanned, tune back to the
 363          * original channel and send a nullfunc frame with power save bit
 364          * off to trigger the AP to send us all the buffered frames.
 365          *
 366          * Note that while local->sw_scanning is true everything else but
 367          * nullfunc frames and probe requests will be dropped in
 368          * ieee80211_tx_h_check_assoc().
 369          */
 370         drv_sw_scan_start(local);
 371
 372         local->leave_oper_channel_time = 0;
 373         local->next_scan_state = SCAN_DECISION;
 374         local->scan_channel_idx = 0;
 375
 376         /* We always want to use off-channel PS, even if we
 377          * are not really leaving oper-channel.  Don't
 378          * tell the AP though, as long as we are on-channel.
 379          */
 380         ieee80211_offchannel_enable_all_ps(local, false);
 381
 382         ieee80211_configure_filter(local);
 383
 384         /* We need to set power level at maximum rate for scanning. */
 385         ieee80211_hw_config(local, 0);
 386
 387         ieee80211_queue_delayed_work(&local->hw,
 388                                      &local->scan_work,
 389                                      IEEE80211_CHANNEL_TIME);
 390
 391         return 0;
 392 }
 393
 394
 395 static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 396                                   struct cfg80211_scan_request *req)
 397 {
 398         struct ieee80211_local *local = sdata->local;
 399         int rc;
 400
 401         lockdep_assert_held(&local->mtx);
 402
 403         if (local->scan_req)
 404                 return -EBUSY;
 405
 406         if (!list_empty(&local->work_list)) {
 407                 /* wait for the work to finish/time out */
 408                 local->scan_req = req;
 409                 local->scan_sdata = sdata;
 410                 return 0;
 411         }
 412
 413         if (local->ops->hw_scan) {
 414                 u8 *ies;
 415
 416                 local->hw_scan_req = kmalloc(
 417                                 sizeof(*local->hw_scan_req) +
 418                                 req->n_channels * sizeof(req->channels[0]) +
 419                                 2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
 420                                 req->ie_len, GFP_KERNEL);
 421                 if (!local->hw_scan_req)
 422                         return -ENOMEM;
 423
 424                 local->hw_scan_req->ssids = req->ssids;
 425                 local->hw_scan_req->n_ssids = req->n_ssids;
 426                 ies = (u8 *)local->hw_scan_req +
 427                         sizeof(*local->hw_scan_req) +
 428                         req->n_channels * sizeof(req->channels[0]);
 429                 local->hw_scan_req->ie = ies;
 430
 431                 local->hw_scan_band = 0;
 432
 433                 /*
 434                  * After allocating local->hw_scan_req, we must
 435                  * go through until ieee80211_prep_hw_scan(), so
 436                  * anything that might be changed here and leave
 437                  * this function early must not go after this
 438                  * allocation.
 439                  */
 440         }
 441
 442         local->scan_req = req;
 443         local->scan_sdata = sdata;
 444
 445         if (local->ops->hw_scan)
 446                 __set_bit(SCAN_HW_SCANNING, &local->scanning);
 447         else
 448                 __set_bit(SCAN_SW_SCANNING, &local->scanning);
 449
 450         ieee80211_recalc_idle(local);
 451
 452         if (local->ops->hw_scan) {
 453                 WARN_ON(!ieee80211_prep_hw_scan(local));
 454                 rc = drv_hw_scan(local, sdata, local->hw_scan_req);
 455         } else
 456                 rc = ieee80211_start_sw_scan(local);
 457
 458         if (rc) {
 459                 kfree(local->hw_scan_req);
 460                 local->hw_scan_req = NULL;
 461                 local->scanning = 0;
 462
 463                 ieee80211_recalc_idle(local);
 464
 465                 local->scan_req = NULL;
 466                 local->scan_sdata = NULL;
 467         }
 468
 469         return rc;
 470 }
 471
 472 static unsigned long
 473 ieee80211_scan_get_channel_time(struct ieee80211_channel *chan)
 474 {
 475         /*
 476          * TODO: channel switching also consumes quite some time,
 477          * add that delay as well to get a better estimation
 478          */
 479         if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN)
 480                 return IEEE80211_PASSIVE_CHANNEL_TIME;
 481         return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
 482 }
 483
 484 static void ieee80211_scan_state_decision(struct ieee80211_local *local,
 485                                           unsigned long *next_delay)
 486 {
 487         bool associated = false;
 488         bool tx_empty = true;
 489         bool bad_latency;
 490         bool listen_int_exceeded;
 491         unsigned long min_beacon_int = 0;
 492         struct ieee80211_sub_if_data *sdata;
 493         struct ieee80211_channel *next_chan;
 494
 495         /*
 496          * check if at least one STA interface is associated,
 497          * check if at least one STA interface has pending tx frames
 498          * and grab the lowest used beacon interval
 499          */
 500         mutex_lock(&local->iflist_mtx);
 501         list_for_each_entry(sdata, &local->interfaces, list) {
 502                 if (!ieee80211_sdata_running(sdata))
 503                         continue;
 504
 505                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 506                         if (sdata->u.mgd.associated) {
 507                                 associated = true;
 508
 509                                 if (sdata->vif.bss_conf.beacon_int <
 510                                     min_beacon_int || min_beacon_int == 0)
 511                                         min_beacon_int =
 512                                                 sdata->vif.bss_conf.beacon_int;
 513
 514                                 if (!qdisc_all_tx_empty(sdata->dev)) {
 515                                         tx_empty = false;
 516                                         break;
 517                                 }
 518                         }
 519                 }
 520         }
 521         mutex_unlock(&local->iflist_mtx);
 522
 523         next_chan = local->scan_req->channels[local->scan_channel_idx];
 524
 525         if (ieee80211_cfg_on_oper_channel(local)) {
 526                 /* We're currently on operating channel. */
 527                 if (next_chan == local->oper_channel)
 528                         /* We don't need to move off of operating channel. */
 529                         local->next_scan_state = SCAN_SET_CHANNEL;
 530                 else
 531                         /*
 532                          * We do need to leave operating channel, as next
 533                          * scan is somewhere else.
 534                          */
 535                         local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
 536         } else {
 537                 /*
 538                  * we're currently scanning a different channel, let's
 539                  * see if we can scan another channel without interfering
 540                  * with the current traffic situation.
 541                  *
 542                  * Since we don't know if the AP has pending frames for us
 543                  * we can only check for our tx queues and use the current
 544                  * pm_qos requirements for rx. Hence, if no tx traffic occurs
 545                  * at all we will scan as many channels in a row as the pm_qos
 546                  * latency allows us to. Additionally we also check for the
 547                  * currently negotiated listen interval to prevent losing
 548                  * frames unnecessarily.
 549                  *
 550                  * Otherwise switch back to the operating channel.
 551                  */
 552
 553                 bad_latency = time_after(jiffies +
 554                                 ieee80211_scan_get_channel_time(next_chan),
 555                                 local->leave_oper_channel_time +
 556                                 usecs_to_jiffies(pm_qos_request(PM_QOS_NETWORK_LATENCY)));
 557
 558                 listen_int_exceeded = time_after(jiffies +
 559                                 ieee80211_scan_get_channel_time(next_chan),
 560                                 local->leave_oper_channel_time +
 561                                 usecs_to_jiffies(min_beacon_int * 1024) *
 562                                 local->hw.conf.listen_interval);
 563
 564                 if (associated && ( !tx_empty || bad_latency ||
 565                     listen_int_exceeded))
 566                         local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
 567                 else
 568                         local->next_scan_state = SCAN_SET_CHANNEL;
 569         }
 570
 571         *next_delay = 0;
 572 }
 573
 574 static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
 575                                                     unsigned long *next_delay)
 576 {
 577         /* PS will already be in off-channel mode,
 578          * we do that once at the beginning of scanning.
 579          */
 580         ieee80211_offchannel_stop_vifs(local, false);
 581
 582         /*
 583          * What if the nullfunc frames didn't arrive?
 584          */
 585         drv_flush(local, false);
 586         if (local->ops->flush)
 587                 *next_delay = 0;
 588         else
 589                 *next_delay = HZ / 10;
 590
 591         /* remember when we left the operating channel */
 592         local->leave_oper_channel_time = jiffies;
 593
 594         /* advance to the next channel to be scanned */
 595         local->next_scan_state = SCAN_SET_CHANNEL;
 596 }
 597
 598 static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
 599                                                     unsigned long *next_delay)
 600 {
 601         /* switch back to the operating channel */
 602         local->scan_channel = NULL;
 603         if (!ieee80211_cfg_on_oper_channel(local))
 604                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 605
 606         /*
 607          * Re-enable vifs and beaconing.  Leave PS
 608          * in off-channel state..will put that back
 609          * on-channel at the end of scanning.
 610          */
 611         ieee80211_offchannel_return(local, true, false);
 612
 613         *next_delay = HZ / 5;
 614         local->next_scan_state = SCAN_DECISION;
 615 }
 616
 617 static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
 618                                              unsigned long *next_delay)
 619 {
 620         int skip;
 621         struct ieee80211_channel *chan;
 622
 623         skip = 0;
 624         chan = local->scan_req->channels[local->scan_channel_idx];
 625
 626         local->scan_channel = chan;
 627
 628         /* Only call hw-config if we really need to change channels. */
 629         if (chan != local->hw.conf.channel)
 630                 if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
 631                         skip = 1;
 632
 633         /* advance state machine to next channel/band */
 634         local->scan_channel_idx++;
 635
 636         if (skip) {
 637                 /* if we skip this channel return to the decision state */
 638                 local->next_scan_state = SCAN_DECISION;
 639                 return;
 640         }
 641
 642         /*
 643          * Probe delay is used to update the NAV, cf. 11.1.3.2.2
 644          * (which unfortunately doesn't say _why_ step a) is done,
 645          * but it waits for the probe delay or until a frame is
 646          * received - and the received frame would update the NAV).
 647          * For now, we do not support waiting until a frame is
 648          * received.
 649          *
 650          * In any case, it is not necessary for a passive scan.
 651          */
 652         if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
 653             !local->scan_req->n_ssids) {
 654                 *next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 655                 local->next_scan_state = SCAN_DECISION;
 656                 return;
 657         }
 658
 659         /* active scan, send probes */
 660         *next_delay = IEEE80211_PROBE_DELAY;
 661         local->next_scan_state = SCAN_SEND_PROBE;
 662 }
 663
 664 static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
 665                                             unsigned long *next_delay)
 666 {
 667         int i;
 668         struct ieee80211_sub_if_data *sdata = local->scan_sdata;
 669
 670         for (i = 0; i < local->scan_req->n_ssids; i++)
 671                 ieee80211_send_probe_req(
 672                         sdata, NULL,
 673                         local->scan_req->ssids[i].ssid,
 674                         local->scan_req->ssids[i].ssid_len,
 675                         local->scan_req->ie, local->scan_req->ie_len);
 676
 677         /*
 678          * After sending probe requests, wait for probe responses
 679          * on the channel.
 680          */
 681         *next_delay = IEEE80211_CHANNEL_TIME;
 682         local->next_scan_state = SCAN_DECISION;
 683 }
 684
 685 void ieee80211_scan_work(struct work_struct *work)
 686 {
 687         struct ieee80211_local *local =
 688                 container_of(work, struct ieee80211_local, scan_work.work);
 689         struct ieee80211_sub_if_data *sdata = local->scan_sdata;
 690         unsigned long next_delay = 0;
 691         bool aborted, hw_scan, finish;
 692
 693         mutex_lock(&local->mtx);
 694
 695         if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) {
 696                 aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
 697                 goto out_complete;
 698         }
 699
 700         if (!sdata || !local->scan_req)
 701                 goto out;
 702
 703         if (local->scan_req && !local->scanning) {
 704                 struct cfg80211_scan_request *req = local->scan_req;
 705                 int rc;
 706
 707                 local->scan_req = NULL;
 708                 local->scan_sdata = NULL;
 709
 710                 rc = __ieee80211_start_scan(sdata, req);
 711                 if (rc) {
 712                         /* need to complete scan in cfg80211 */
 713                         local->scan_req = req;
 714                         aborted = true;
 715                         goto out_complete;
 716                 } else
 717                         goto out;
 718         }
 719
 720         /*
 721          * Avoid re-scheduling when the sdata is going away.
 722          */
 723         if (!ieee80211_sdata_running(sdata)) {
 724                 aborted = true;
 725                 goto out_complete;
 726         }
 727
 728         /*
 729          * as long as no delay is required advance immediately
 730          * without scheduling a new work
 731          */
 732         do {
 733                 switch (local->next_scan_state) {
 734                 case SCAN_DECISION:
 735                         /* if no more bands/channels left, complete scan */
 736                         if (local->scan_channel_idx >= local->scan_req->n_channels) {
 737                                 aborted = false;
 738                                 goto out_complete;
 739                         }
 740                         ieee80211_scan_state_decision(local, &next_delay);
 741                         break;
 742                 case SCAN_SET_CHANNEL:
 743                         ieee80211_scan_state_set_channel(local, &next_delay);
 744                         break;
 745                 case SCAN_SEND_PROBE:
 746                         ieee80211_scan_state_send_probe(local, &next_delay);
 747                         break;
 748                 case SCAN_LEAVE_OPER_CHANNEL:
 749                         ieee80211_scan_state_leave_oper_channel(local, &next_delay);
 750                         break;
 751                 case SCAN_ENTER_OPER_CHANNEL:
 752                         ieee80211_scan_state_enter_oper_channel(local, &next_delay);
 753                         break;
 754                 }
 755         } while (next_delay == 0);
 756
 757         ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
 758         mutex_unlock(&local->mtx);
 759         return;
 760
 761 out_complete:
 762         hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
 763         finish = __ieee80211_scan_completed(&local->hw, aborted, hw_scan);
 764         mutex_unlock(&local->mtx);
 765         if (finish)
 766                 __ieee80211_scan_completed_finish(&local->hw, hw_scan);
 767         return;
 768
 769 out:
 770         mutex_unlock(&local->mtx);
 771 }
 772
 773 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 774                            struct cfg80211_scan_request *req)
 775 {
 776         int res;
 777
 778         mutex_lock(&sdata->local->mtx);
 779         res = __ieee80211_start_scan(sdata, req);
 780         mutex_unlock(&sdata->local->mtx);
 781
 782         return res;
 783 }
 784
 785 int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
 786                                     const u8 *ssid, u8 ssid_len,
 787                                     struct ieee80211_channel *chan)
 788 {
 789         struct ieee80211_local *local = sdata->local;
 790         int ret = -EBUSY;
 791         enum ieee80211_band band;
 792
 793         mutex_lock(&local->mtx);
 794
 795         /* busy scanning */
 796         if (local->scan_req)
 797                 goto unlock;
 798
 799         /* fill internal scan request */
 800         if (!chan) {
 801                 int i, nchan = 0;
 802
 803                 for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
 804                         if (!local->hw.wiphy->bands[band])
 805                                 continue;
 806                         for (i = 0;
 807                              i < local->hw.wiphy->bands[band]->n_channels;
 808                              i++) {
 809                                 local->int_scan_req->channels[nchan] =
 810                                     &local->hw.wiphy->bands[band]->channels[i];
 811                                 nchan++;
 812                         }
 813                 }
 814
 815                 local->int_scan_req->n_channels = nchan;
 816         } else {
 817                 local->int_scan_req->channels[0] = chan;
 818                 local->int_scan_req->n_channels = 1;
 819         }
 820
 821         local->int_scan_req->ssids = &local->scan_ssid;
 822         local->int_scan_req->n_ssids = 1;
 823         memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
 824         local->int_scan_req->ssids[0].ssid_len = ssid_len;
 825
 826         ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
 827  unlock:
 828         mutex_unlock(&local->mtx);
 829         return ret;
 830 }
 831
 832 /*
 833  * Only call this function when a scan can't be queued -- under RTNL.
 834  */
 835 void ieee80211_scan_cancel(struct ieee80211_local *local)
 836 {
 837         bool abortscan;
 838         bool finish = false;
 839
 840         /*
 841          * We are only canceling software scan, or deferred scan that was not
 842          * yet really started (see __ieee80211_start_scan ).
 843          *
 844          * Regarding hardware scan:
 845          * - we can not call  __ieee80211_scan_completed() as when
 846          *   SCAN_HW_SCANNING bit is set this function change
 847          *   local->hw_scan_req to operate on 5G band, what race with
 848          *   driver which can use local->hw_scan_req
 849          *
 850          * - we can not cancel scan_work since driver can schedule it
 851          *   by ieee80211_scan_completed(..., true) to finish scan
 852          *
 853          * Hence low lever driver is responsible for canceling HW scan.
 854          */
 855
 856         mutex_lock(&local->mtx);
 857         abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning);
 858         if (abortscan)
 859                 finish = __ieee80211_scan_completed(&local->hw, true, false);
 860         mutex_unlock(&local->mtx);
 861
 862         if (abortscan) {
 863                 /* The scan is canceled, but stop work from being pending */
 864                 cancel_delayed_work_sync(&local->scan_work);
 865         }
 866         if (finish)
 867                 __ieee80211_scan_completed_finish(&local->hw, false);
 868 }