linux/net/mac80211/scan.c
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   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
  30struct ieee80211_bss *
  31ieee80211_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
  41static 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
  49void ieee80211_rx_bss_put(struct ieee80211_local *local,
  50                          struct ieee80211_bss *bss)
  51{
  52        cfg80211_put_bss((struct cfg80211_bss *)bss);
  53}
  54
  55struct ieee80211_bss *
  56ieee80211_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
 123void 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
 136ieee80211_rx_result
 137ieee80211_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
 205void 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 */
 221static 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 */
 252static 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
 277void 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}
 351EXPORT_SYMBOL(ieee80211_scan_completed);
 352
 353void 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
 422int 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
 533int 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}
 568