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 void ieee80211_scan_failed(struct ieee80211_local *local)
 206 {
 207         if (WARN_ON(!local->scan_req))
 208                 return;
 209
 210         /* notify cfg80211 about the failed scan */
 211         if (local->scan_req != &local->int_scan_req)
 212                 cfg80211_scan_done(local->scan_req, true);
 213
 214         local->scan_req = NULL;
 215 }
 216
 217 /*
 218  * inform AP that we will go to sleep so that it will buffer the frames
 219  * while we scan
 220  */
 221 static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
 222 {
 223         struct ieee80211_local *local = sdata->local;
 224         bool ps = false;
 225
 226         /* FIXME: what to do when local->pspolling is true? */
 227
 228         del_timer_sync(&local->dynamic_ps_timer);
 229         cancel_work_sync(&local->dynamic_ps_enable_work);
 230
 231         if (local->hw.conf.flags & IEEE80211_CONF_PS) {
 232                 ps = true;
 233                 local->hw.conf.flags &= ~IEEE80211_CONF_PS;
 234                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 235         }
 236
 237         if (!ps || !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
 238                 /*
 239                  * If power save was enabled, no need to send a nullfunc
 240                  * frame because AP knows that we are sleeping. But if the
 241                  * hardware is creating the nullfunc frame for power save
 242                  * status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
 243                  * enabled) and power save was enabled, the firmware just
 244                  * sent a null frame with power save disabled. So we need
 245                  * to send a new nullfunc frame to inform the AP that we
 246                  * are again sleeping.
 247                  */
 248                 ieee80211_send_nullfunc(local, sdata, 1);
 249 }
 250
 251 /* inform AP that we are awake again, unless power save is enabled */
 252 static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
 253 {
 254         struct ieee80211_local *local = sdata->local;
 255
 256         if (!local->powersave)
 257                 ieee80211_send_nullfunc(local, sdata, 0);
 258         else {
 259                 /*
 260                  * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
 261                  * will send a nullfunc frame with the powersave bit set
 262                  * even though the AP already knows that we are sleeping.
 263                  * This could be avoided by sending a null frame with power
 264                  * save bit disabled before enabling the power save, but
 265                  * this doesn't gain anything.
 266                  *
 267                  * When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
 268                  * to send a nullfunc frame because AP already knows that
 269                  * we are sleeping, let's just enable power save mode in
 270                  * hardware.
 271                  */
 272                 local->hw.conf.flags |= IEEE80211_CONF_PS;
 273                 ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 274         }
 275 }
 276
 277 void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 278 {
 279         struct ieee80211_local *local = hw_to_local(hw);
 280         struct ieee80211_sub_if_data *sdata;
 281
 282         if (WARN_ON(!local->hw_scanning && !local->sw_scanning))
 283                 return;
 284
 285         if (WARN_ON(!local->scan_req))
 286                 return;
 287
 288         if (local->scan_req != &local->int_scan_req)
 289                 cfg80211_scan_done(local->scan_req, aborted);
 290         local->scan_req = NULL;
 291
 292         local->last_scan_completed = jiffies;
 293
 294         if (local->hw_scanning) {
 295                 local->hw_scanning = false;
 296                 /*
 297                  * Somebody might have requested channel change during scan
 298                  * that we won't have acted upon, try now. ieee80211_hw_config
 299                  * will set the flag based on actual changes.
 300                  */
 301                 ieee80211_hw_config(local, 0);
 302                 goto done;
 303         }
 304
 305         local->sw_scanning = false;
 306         ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 307
 308         netif_tx_lock_bh(local->mdev);
 309         netif_addr_lock(local->mdev);
 310         local->filter_flags &= ~FIF_BCN_PRBRESP_PROMISC;
 311         local->ops->configure_filter(local_to_hw(local),
 312                                      FIF_BCN_PRBRESP_PROMISC,
 313                                      &local->filter_flags,
 314                                      local->mdev->mc_count,
 315                                      local->mdev->mc_list);
 316
 317         netif_addr_unlock(local->mdev);
 318         netif_tx_unlock_bh(local->mdev);
 319
 320         if (local->ops->sw_scan_complete)
 321                 local->ops->sw_scan_complete(local_to_hw(local));
 322
 323         mutex_lock(&local->iflist_mtx);
 324         list_for_each_entry(sdata, &local->interfaces, list) {
 325                 if (!netif_running(sdata->dev))
 326                         continue;
 327
 328                 /* Tell AP we're back */
 329                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 330                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
 331                                 ieee80211_scan_ps_disable(sdata);
 332                                 netif_tx_wake_all_queues(sdata->dev);
 333                         }
 334                 } else
 335                         netif_tx_wake_all_queues(sdata->dev);
 336
 337                 /* re-enable beaconing */
 338                 if (sdata->vif.type == NL80211_IFTYPE_AP ||
 339                     sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 340                     sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 341                         ieee80211_if_config(sdata,
 342                                             IEEE80211_IFCC_BEACON_ENABLED);
 343         }
 344         mutex_unlock(&local->iflist_mtx);
 345
 346  done:
 347         ieee80211_mlme_notify_scan_completed(local);
 348         ieee80211_ibss_notify_scan_completed(local);
 349         ieee80211_mesh_notify_scan_completed(local);
 350 }
 351 EXPORT_SYMBOL(ieee80211_scan_completed);
 352
 353 void ieee80211_scan_work(struct work_struct *work)
 354 {
 355         struct ieee80211_local *local =
 356                 container_of(work, struct ieee80211_local, scan_work.work);
 357         struct ieee80211_sub_if_data *sdata = local->scan_sdata;
 358         struct ieee80211_channel *chan;
 359         int skip, i;
 360         unsigned long next_delay = 0;
 361
 362         /*
 363          * Avoid re-scheduling when the sdata is going away.
 364          */
 365         if (!netif_running(sdata->dev))
 366                 return;
 367
 368         switch (local->scan_state) {
 369         case SCAN_SET_CHANNEL:
 370                 /* if no more bands/channels left, complete scan */
 371                 if (local->scan_channel_idx >= local->scan_req->n_channels) {
 372                         ieee80211_scan_completed(local_to_hw(local), false);
 373                         return;
 374                 }
 375                 skip = 0;
 376                 chan = local->scan_req->channels[local->scan_channel_idx];
 377
 378                 if (chan->flags & IEEE80211_CHAN_DISABLED ||
 379                     (sdata->vif.type == NL80211_IFTYPE_ADHOC &&
 380                      chan->flags & IEEE80211_CHAN_NO_IBSS))
 381                         skip = 1;
 382
 383                 if (!skip) {
 384                         local->scan_channel = chan;
 385                         if (ieee80211_hw_config(local,
 386                                                 IEEE80211_CONF_CHANGE_CHANNEL))
 387                                 skip = 1;
 388                 }
 389
 390                 /* advance state machine to next channel/band */
 391                 local->scan_channel_idx++;
 392
 393                 if (skip)
 394                         break;
 395
 396                 next_delay = IEEE80211_PROBE_DELAY +
 397                              usecs_to_jiffies(local->hw.channel_change_time);
 398                 local->scan_state = SCAN_SEND_PROBE;
 399                 break;
 400         case SCAN_SEND_PROBE:
 401                 next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
 402                 local->scan_state = SCAN_SET_CHANNEL;
 403
 404                 if (local->scan_channel->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
 405                     !local->scan_req->n_ssids)
 406                         break;
 407                 for (i = 0; i < local->scan_req->n_ssids; i++)
 408                         ieee80211_send_probe_req(
 409                                 sdata, NULL,
 410                                 local->scan_req->ssids[i].ssid,
 411                                 local->scan_req->ssids[i].ssid_len,
 412                                 local->scan_req->ie, local->scan_req->ie_len);
 413                 next_delay = IEEE80211_CHANNEL_TIME;
 414                 break;
 415         }
 416
 417         queue_delayed_work(local->hw.workqueue, &local->scan_work,
 418                            next_delay);
 419 }
 420
 421
 422 int ieee80211_start_scan(struct ieee80211_sub_if_data *scan_sdata,
 423                          struct cfg80211_scan_request *req)
 424 {
 425         struct ieee80211_local *local = scan_sdata->local;
 426         struct ieee80211_sub_if_data *sdata;
 427
 428         if (!req)
 429                 return -EINVAL;
 430
 431         if (local->scan_req && local->scan_req != req)
 432                 return -EBUSY;
 433
 434         local->scan_req = req;
 435
 436         /* MLME-SCAN.request (page 118)  page 144 (11.1.3.1)
 437          * BSSType: INFRASTRUCTURE, INDEPENDENT, ANY_BSS
 438          * BSSID: MACAddress
 439          * SSID
 440          * ScanType: ACTIVE, PASSIVE
 441          * ProbeDelay: delay (in microseconds) to be used prior to transmitting
 442          *    a Probe frame during active scanning
 443          * ChannelList
 444          * MinChannelTime (>= ProbeDelay), in TU
 445          * MaxChannelTime: (>= MinChannelTime), in TU
 446          */
 447
 448          /* MLME-SCAN.confirm
 449           * BSSDescriptionSet
 450           * ResultCode: SUCCESS, INVALID_PARAMETERS
 451          */
 452
 453         if (local->sw_scanning || local->hw_scanning) {
 454                 if (local->scan_sdata == scan_sdata)
 455                         return 0;
 456                 return -EBUSY;
 457         }
 458
 459         if (local->ops->hw_scan) {
 460                 int rc;
 461
 462                 local->hw_scanning = true;
 463                 rc = local->ops->hw_scan(local_to_hw(local), req);
 464                 if (rc) {
 465                         local->hw_scanning = false;
 466                         return rc;
 467                 }
 468                 local->scan_sdata = scan_sdata;
 469                 return 0;
 470         }
 471
 472         /*
 473          * Hardware/driver doesn't support hw_scan, so use software
 474          * scanning instead. First send a nullfunc frame with power save
 475          * bit on so that AP will buffer the frames for us while we are not
 476          * listening, then send probe requests to each channel and wait for
 477          * the responses. After all channels are scanned, tune back to the
 478          * original channel and send a nullfunc frame with power save bit
 479          * off to trigger the AP to send us all the buffered frames.
 480          *
 481          * Note that while local->sw_scanning is true everything else but
 482          * nullfunc frames and probe requests will be dropped in
 483          * ieee80211_tx_h_check_assoc().
 484          */
 485         local->sw_scanning = true;
 486         if (local->ops->sw_scan_start)
 487                 local->ops->sw_scan_start(local_to_hw(local));
 488
 489         mutex_lock(&local->iflist_mtx);
 490         list_for_each_entry(sdata, &local->interfaces, list) {
 491                 if (!netif_running(sdata->dev))
 492                         continue;
 493
 494                 /* disable beaconing */
 495                 if (sdata->vif.type == NL80211_IFTYPE_AP ||
 496                     sdata->vif.type == NL80211_IFTYPE_ADHOC ||
 497                     sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
 498                         ieee80211_if_config(sdata,
 499                                             IEEE80211_IFCC_BEACON_ENABLED);
 500
 501                 if (sdata->vif.type == NL80211_IFTYPE_STATION) {
 502                         if (sdata->u.mgd.flags & IEEE80211_STA_ASSOCIATED) {
 503                                 netif_tx_stop_all_queues(sdata->dev);
 504                                 ieee80211_scan_ps_enable(sdata);
 505                         }
 506                 } else
 507                         netif_tx_stop_all_queues(sdata->dev);
 508         }
 509         mutex_unlock(&local->iflist_mtx);
 510
 511         local->scan_state = SCAN_SET_CHANNEL;
 512         local->scan_channel_idx = 0;
 513         local->scan_sdata = scan_sdata;
 514         local->scan_req = req;
 515
 516         netif_addr_lock_bh(local->mdev);
 517         local->filter_flags |= FIF_BCN_PRBRESP_PROMISC;
 518         local->ops->configure_filter(local_to_hw(local),
 519                                      FIF_BCN_PRBRESP_PROMISC,
 520                                      &local->filter_flags,
 521                                      local->mdev->mc_count,
 522                                      local->mdev->mc_list);
 523         netif_addr_unlock_bh(local->mdev);
 524
 525         /* TODO: start scan as soon as all nullfunc frames are ACKed */
 526         queue_delayed_work(local->hw.workqueue, &local->scan_work,
 527                            IEEE80211_CHANNEL_TIME);
 528
 529         return 0;
 530 }
 531
 532
 533 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
 534                            struct cfg80211_scan_request *req)
 535 {
 536         struct ieee80211_local *local = sdata->local;
 537         struct ieee80211_if_managed *ifmgd;
 538
 539         if (!req)
 540                 return -EINVAL;
 541
 542         if (local->scan_req && local->scan_req != req)
 543                 return -EBUSY;
 544
 545         local->scan_req = req;
 546
 547         if (sdata->vif.type != NL80211_IFTYPE_STATION)
 548                 return ieee80211_start_scan(sdata, req);
 549
 550         /*
 551          * STA has a state machine that might need to defer scanning
 552          * while it's trying to associate/authenticate, therefore we
 553          * queue it up to the state machine in that case.
 554          */
 555
 556         if (local->sw_scanning || local->hw_scanning) {
 557                 if (local->scan_sdata == sdata)
 558                         return 0;
 559                 return -EBUSY;
 560         }
 561
 562         ifmgd = &sdata->u.mgd;
 563         set_bit(IEEE80211_STA_REQ_SCAN, &ifmgd->request);
 564         queue_work(local->hw.workqueue, &ifmgd->work);
 565
 566         return 0;
 567 }