/*
 * Scanning implementation
 *
 * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
 * Copyright 2004, Instant802 Networks, Inc.
 * Copyright 2005, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
 * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
 * Copyright 2013-2015  Intel Mobile Communications GmbH
 * Copyright 2016  Intel Deutschland GmbH
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/if_arp.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <net/sch_generic.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/mac80211.h>

#include "ieee80211_i.h"
#include "driver-ops.h"
#include "mesh.h"

#define IEEE80211_PROBE_DELAY (HZ / 33)
#define IEEE80211_CHANNEL_TIME (HZ / 33)
#define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 9)

void ieee80211_rx_bss_put(struct ieee80211_local *local,
                          struct ieee80211_bss *bss)
{
        if (!bss)
                return;
        cfg80211_put_bss(local->hw.wiphy,
                         container_of((void *)bss, struct cfg80211_bss, priv));
}

static bool is_uapsd_supported(struct ieee802_11_elems *elems)
{
        u8 qos_info;

        if (elems->wmm_info && elems->wmm_info_len == 7
            && elems->wmm_info[5] == 1)
                qos_info = elems->wmm_info[6];
        else if (elems->wmm_param && elems->wmm_param_len == 24
                 && elems->wmm_param[5] == 1)
                qos_info = elems->wmm_param[6];
        else
                /* no valid wmm information or parameter element found */
                return false;

        return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
}

struct ieee80211_bss *
ieee80211_bss_info_update(struct ieee80211_local *local,
                          struct ieee80211_rx_status *rx_status,
                          struct ieee80211_mgmt *mgmt, size_t len,
                          struct ieee802_11_elems *elems,
                          struct ieee80211_channel *channel)
{
        bool beacon = ieee80211_is_beacon(mgmt->frame_control);
        struct cfg80211_bss *cbss;
        struct ieee80211_bss *bss;
        int clen, srlen;
        struct cfg80211_inform_bss bss_meta = {
                .boottime_ns = rx_status->boottime_ns,
        };
        bool signal_valid;
        struct ieee80211_sub_if_data *scan_sdata;

        if (ieee80211_hw_check(&local->hw, SIGNAL_DBM))
                bss_meta.signal = rx_status->signal * 100;
        else if (ieee80211_hw_check(&local->hw, SIGNAL_UNSPEC))
                bss_meta.signal = (rx_status->signal * 100) / local->hw.max_signal;

        bss_meta.scan_width = NL80211_BSS_CHAN_WIDTH_20;
        if (rx_status->bw == RATE_INFO_BW_5)
                bss_meta.scan_width = NL80211_BSS_CHAN_WIDTH_5;
        else if (rx_status->bw == RATE_INFO_BW_10)
                bss_meta.scan_width = NL80211_BSS_CHAN_WIDTH_10;

        bss_meta.chan = channel;

        rcu_read_lock();
        scan_sdata = rcu_dereference(local->scan_sdata);
        if (scan_sdata && scan_sdata->vif.type == NL80211_IFTYPE_STATION &&
            scan_sdata->vif.bss_conf.assoc &&
            ieee80211_have_rx_timestamp(rx_status)) {
                bss_meta.parent_tsf =
                        ieee80211_calculate_rx_timestamp(local, rx_status,
                                                         len + FCS_LEN, 24);
                ether_addr_copy(bss_meta.parent_bssid,
                                scan_sdata->vif.bss_conf.bssid);
        }
        rcu_read_unlock();

        cbss = cfg80211_inform_bss_frame_data(local->hw.wiphy, &bss_meta,
                                              mgmt, len, GFP_ATOMIC);
        if (!cbss)
                return NULL;
        /* In case the signal is invalid update the status */
        signal_valid = abs(channel->center_freq - cbss->channel->center_freq)
                <= local->hw.wiphy->max_adj_channel_rssi_comp;
        if (!signal_valid)
                rx_status->flag |= RX_FLAG_NO_SIGNAL_VAL;

        bss = (void *)cbss->priv;

        if (beacon)
                bss->device_ts_beacon = rx_status->device_timestamp;
        else
                bss->device_ts_presp = rx_status->device_timestamp;

        if (elems->parse_error) {
                if (beacon)
                        bss->corrupt_data |= IEEE80211_BSS_CORRUPT_BEACON;
                else
                        bss->corrupt_data |= IEEE80211_BSS_CORRUPT_PROBE_RESP;
        } else {
                if (beacon)
                        bss->corrupt_data &= ~IEEE80211_BSS_CORRUPT_BEACON;
                else
                        bss->corrupt_data &= ~IEEE80211_BSS_CORRUPT_PROBE_RESP;
        }

        /* save the ERP value so that it is available at association time */
        if (elems->erp_info && (!elems->parse_error ||
                                !(bss->valid_data & IEEE80211_BSS_VALID_ERP))) {
                bss->erp_value = elems->erp_info[0];
                bss->has_erp_value = true;
                if (!elems->parse_error)
                        bss->valid_data |= IEEE80211_BSS_VALID_ERP;
        }

        /* replace old supported rates if we get new values */
        if (!elems->parse_error ||
            !(bss->valid_data & IEEE80211_BSS_VALID_RATES)) {
                srlen = 0;
                if (elems->supp_rates) {
                        clen = IEEE80211_MAX_SUPP_RATES;
                        if (clen > elems->supp_rates_len)
                                clen = elems->supp_rates_len;
                        memcpy(bss->supp_rates, elems->supp_rates, clen);
                        srlen += clen;
                }
                if (elems->ext_supp_rates) {
                        clen = IEEE80211_MAX_SUPP_RATES - srlen;
                        if (clen > elems->ext_supp_rates_len)
                                clen = elems->ext_supp_rates_len;
                        memcpy(bss->supp_rates + srlen, elems->ext_supp_rates,
                               clen);
                        srlen += clen;
                }
                if (srlen) {
                        bss->supp_rates_len = srlen;
                        if (!elems->parse_error)
                                bss->valid_data |= IEEE80211_BSS_VALID_RATES;
                }
        }

        if (!elems->parse_error ||
            !(bss->valid_data & IEEE80211_BSS_VALID_WMM)) {
                bss->wmm_used = elems->wmm_param || elems->wmm_info;
                bss->uapsd_supported = is_uapsd_supported(elems);
                if (!elems->parse_error)
                        bss->valid_data |= IEEE80211_BSS_VALID_WMM;
        }

        if (beacon) {
                struct ieee80211_supported_band *sband =
                        local->hw.wiphy->bands[rx_status->band];
                if (!(rx_status->encoding == RX_ENC_HT) &&
                    !(rx_status->encoding == RX_ENC_VHT))
                        bss->beacon_rate =
                                &sband->bitrates[rx_status->rate_idx];
        }

        return bss;
}

void ieee80211_scan_rx(struct ieee80211_local *local, struct sk_buff *skb)
{
        struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
        struct ieee80211_sub_if_data *sdata1, *sdata2;
        struct ieee80211_mgmt *mgmt = (void *)skb->data;
        struct ieee80211_bss *bss;
        u8 *elements;
        struct ieee80211_channel *channel;
        size_t baselen;
        struct ieee802_11_elems elems;

        if (skb->len < 24 ||
            (!ieee80211_is_probe_resp(mgmt->frame_control) &&
             !ieee80211_is_beacon(mgmt->frame_control)))
                return;

        sdata1 = rcu_dereference(local->scan_sdata);
        sdata2 = rcu_dereference(local->sched_scan_sdata);

        if (likely(!sdata1 && !sdata2))
                return;

        if (ieee80211_is_probe_resp(mgmt->frame_control)) {
                struct cfg80211_scan_request *scan_req;
                struct cfg80211_sched_scan_request *sched_scan_req;

                scan_req = rcu_dereference(local->scan_req);
                sched_scan_req = rcu_dereference(local->sched_scan_req);

                /* ignore ProbeResp to foreign address unless scanning
                 * with randomised address
                 */
                if (!(sdata1 &&
                      (ether_addr_equal(mgmt->da, sdata1->vif.addr) ||
                       scan_req->flags & NL80211_SCAN_FLAG_RANDOM_ADDR)) &&
                    !(sdata2 &&
                      (ether_addr_equal(mgmt->da, sdata2->vif.addr) ||
                       sched_scan_req->flags & NL80211_SCAN_FLAG_RANDOM_ADDR)))
                        return;

                elements = mgmt->u.probe_resp.variable;
                baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
        } else {
                baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
                elements = mgmt->u.beacon.variable;
        }

        if (baselen > skb->len)
                return;

        ieee802_11_parse_elems(elements, skb->len - baselen, false, &elems);

        channel = ieee80211_get_channel(local->hw.wiphy, rx_status->freq);

        if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
                return;

        bss = ieee80211_bss_info_update(local, rx_status,
                                        mgmt, skb->len, &elems,
                                        channel);
        if (bss)
                ieee80211_rx_bss_put(local, bss);
}

static void
ieee80211_prepare_scan_chandef(struct cfg80211_chan_def *chandef,
                               enum nl80211_bss_scan_width scan_width)
{
        memset(chandef, 0, sizeof(*chandef));
        switch (scan_width) {
        case NL80211_BSS_CHAN_WIDTH_5:
                chandef->width = NL80211_CHAN_WIDTH_5;
                break;
        case NL80211_BSS_CHAN_WIDTH_10:
                chandef->width = NL80211_CHAN_WIDTH_10;
                break;
        default:
                chandef->width = NL80211_CHAN_WIDTH_20_NOHT;
                break;
        }
}

/* return false if no more work */
static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
{
        struct cfg80211_scan_request *req;
        struct cfg80211_chan_def chandef;
        u8 bands_used = 0;
        int i, ielen, n_chans;

        req = rcu_dereference_protected(local->scan_req,
                                        lockdep_is_held(&local->mtx));

        if (test_bit(SCAN_HW_CANCELLED, &local->scanning))
                return false;

        if (ieee80211_hw_check(&local->hw, SINGLE_SCAN_ON_ALL_BANDS)) {
                for (i = 0; i < req->n_channels; i++) {
                        local->hw_scan_req->req.channels[i] = req->channels[i];
                        bands_used |= BIT(req->channels[i]->band);
                }

                n_chans = req->n_channels;
        } else {
                do {
                        if (local->hw_scan_band == NUM_NL80211_BANDS)
                                return false;

                        n_chans = 0;

                        for (i = 0; i < req->n_channels; i++) {
                                if (req->channels[i]->band !=
                                    local->hw_scan_band)
                                        continue;
                                local->hw_scan_req->req.channels[n_chans] =
                                                        req->channels[i];
                                n_chans++;
                                bands_used |= BIT(req->channels[i]->band);
                        }

                        local->hw_scan_band++;
                } while (!n_chans);
        }

        local->hw_scan_req->req.n_channels = n_chans;
        ieee80211_prepare_scan_chandef(&chandef, req->scan_width);

        ielen = ieee80211_build_preq_ies(local,
                                         (u8 *)local->hw_scan_req->req.ie,
                                         local->hw_scan_ies_bufsize,
                                         &local->hw_scan_req->ies,
                                         req->ie, req->ie_len,
                                         bands_used, req->rates, &chandef);
        local->hw_scan_req->req.ie_len = ielen;
        local->hw_scan_req->req.no_cck = req->no_cck;
        ether_addr_copy(local->hw_scan_req->req.mac_addr, req->mac_addr);
        ether_addr_copy(local->hw_scan_req->req.mac_addr_mask,
                        req->mac_addr_mask);
        ether_addr_copy(local->hw_scan_req->req.bssid, req->bssid);

        return true;
}

static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
{
        struct ieee80211_local *local = hw_to_local(hw);
        bool hw_scan = local->ops->hw_scan;
        bool was_scanning = local->scanning;
        struct cfg80211_scan_request *scan_req;
        struct ieee80211_sub_if_data *scan_sdata;
        struct ieee80211_sub_if_data *sdata;

        lockdep_assert_held(&local->mtx);

        /*
         * It's ok to abort a not-yet-running scan (that
         * we have one at all will be verified by checking
         * local->scan_req next), but not to complete it
         * successfully.
         */
        if (WARN_ON(!local->scanning && !aborted))
                aborted = true;

        if (WARN_ON(!local->scan_req))
                return;

        if (hw_scan && !aborted &&
            !ieee80211_hw_check(&local->hw, SINGLE_SCAN_ON_ALL_BANDS) &&
            ieee80211_prep_hw_scan(local)) {
                int rc;

                rc = drv_hw_scan(local,
                        rcu_dereference_protected(local->scan_sdata,
                                                  lockdep_is_held(&local->mtx)),
                        local->hw_scan_req);

                if (rc == 0)
                        return;

                /* HW scan failed and is going to be reported as aborted,
                 * so clear old scan info.
                 */
                memset(&local->scan_info, 0, sizeof(local->scan_info));
                aborted = true;
        }

        kfree(local->hw_scan_req);
        local->hw_scan_req = NULL;

        scan_req = rcu_dereference_protected(local->scan_req,
                                             lockdep_is_held(&local->mtx));

        if (scan_req != local->int_scan_req) {
                local->scan_info.aborted = aborted;
                cfg80211_scan_done(scan_req, &local->scan_info);
        }
        RCU_INIT_POINTER(local->scan_req, NULL);

        scan_sdata = rcu_dereference_protected(local->scan_sdata,
                                               lockdep_is_held(&local->mtx));
        RCU_INIT_POINTER(local->scan_sdata, NULL);

        local->scanning = 0;
        local->scan_chandef.chan = NULL;

        /* Set power back to normal operating levels. */
        ieee80211_hw_config(local, 0);

        if (!hw_scan) {
                ieee80211_configure_filter(local);
                drv_sw_scan_complete(local, scan_sdata);
                ieee80211_offchannel_return(local);
        }

        ieee80211_recalc_idle(local);

        ieee80211_mlme_notify_scan_completed(local);
        ieee80211_ibss_notify_scan_completed(local);

        /* Requeue all the work that might have been ignored while
         * the scan was in progress; if there was none this will
         * just be a no-op for the particular interface.
         */
        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
                if (ieee80211_sdata_running(sdata))
                        ieee80211_queue_work(&sdata->local->hw, &sdata->work);
        }

        if (was_scanning)
                ieee80211_start_next_roc(local);
}

void ieee80211_scan_completed(struct ieee80211_hw *hw,
                              struct cfg80211_scan_info *info)
{
        struct ieee80211_local *local = hw_to_local(hw);

        trace_api_scan_completed(local, info->aborted);

        set_bit(SCAN_COMPLETED, &local->scanning);
        if (info->aborted)
                set_bit(SCAN_ABORTED, &local->scanning);

        memcpy(&local->scan_info, info, sizeof(*info));

        ieee80211_queue_delayed_work(&local->hw, &local->scan_work, 0);
}
EXPORT_SYMBOL(ieee80211_scan_completed);

static int ieee80211_start_sw_scan(struct ieee80211_local *local,
                                   struct ieee80211_sub_if_data *sdata)
{
        /* Software scan is not supported in multi-channel cases */
        if (local->use_chanctx)
                return -EOPNOTSUPP;

        /*
         * Hardware/driver doesn't support hw_scan, so use software
         * scanning instead. First send a nullfunc frame with power save
         * bit on so that AP will buffer the frames for us while we are not
         * listening, then send probe requests to each channel and wait for
         * the responses. After all channels are scanned, tune back to the
         * original channel and send a nullfunc frame with power save bit
         * off to trigger the AP to send us all the buffered frames.
         *
         * Note that while local->sw_scanning is true everything else but
         * nullfunc frames and probe requests will be dropped in
         * ieee80211_tx_h_check_assoc().
         */
        drv_sw_scan_start(local, sdata, local->scan_addr);

        local->leave_oper_channel_time = jiffies;
        local->next_scan_state = SCAN_DECISION;
        local->scan_channel_idx = 0;

        ieee80211_offchannel_stop_vifs(local);

        /* ensure nullfunc is transmitted before leaving operating channel */
        ieee80211_flush_queues(local, NULL, false);

        ieee80211_configure_filter(local);

        /* We need to set power level at maximum rate for scanning. */
        ieee80211_hw_config(local, 0);

        ieee80211_queue_delayed_work(&local->hw,
                                     &local->scan_work, 0);

        return 0;
}

static bool ieee80211_can_scan(struct ieee80211_local *local,
                               struct ieee80211_sub_if_data *sdata)
{
        if (ieee80211_is_radar_required(local))
                return false;

        if (!list_empty(&local->roc_list))
                return false;

        if (sdata->vif.type == NL80211_IFTYPE_STATION &&
            sdata->u.mgd.flags & IEEE80211_STA_CONNECTION_POLL)
                return false;

        return true;
}

void ieee80211_run_deferred_scan(struct ieee80211_local *local)
{
        lockdep_assert_held(&local->mtx);

        if (!local->scan_req || local->scanning)
                return;

        if (!ieee80211_can_scan(local,
                                rcu_dereference_protected(
                                        local->scan_sdata,
                                        lockdep_is_held(&local->mtx))))
                return;

        ieee80211_queue_delayed_work(&local->hw, &local->scan_work,
                                     round_jiffies_relative(0));
}

static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
                                            unsigned long *next_delay)
{
        int i;
        struct ieee80211_sub_if_data *sdata;
        struct cfg80211_scan_request *scan_req;
        enum nl80211_band band = local->hw.conf.chandef.chan->band;
        u32 tx_flags;

        scan_req = rcu_dereference_protected(local->scan_req,
                                             lockdep_is_held(&local->mtx));

        tx_flags = IEEE80211_TX_INTFL_OFFCHAN_TX_OK;
        if (scan_req->no_cck)
                tx_flags |= IEEE80211_TX_CTL_NO_CCK_RATE;

        sdata = rcu_dereference_protected(local->scan_sdata,
                                          lockdep_is_held(&local->mtx));

        for (i = 0; i < scan_req->n_ssids; i++)
                ieee80211_send_probe_req(
                        sdata, local->scan_addr, scan_req->bssid,
                        scan_req->ssids[i].ssid, scan_req->ssids[i].ssid_len,
                        scan_req->ie, scan_req->ie_len,
                        scan_req->rates[band], false,
                        tx_flags, local->hw.conf.chandef.chan, true);

        /*
         * After sending probe requests, wait for probe responses
         * on the channel.
         */
        *next_delay = IEEE80211_CHANNEL_TIME;
        local->next_scan_state = SCAN_DECISION;
}

static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
                                  struct cfg80211_scan_request *req)
{
        struct ieee80211_local *local = sdata->local;
        int rc;

        lockdep_assert_held(&local->mtx);

        if (local->scan_req || ieee80211_is_radar_required(local))
                return -EBUSY;

        if (!ieee80211_can_scan(local, sdata)) {
                /* wait for the work to finish/time out */
                rcu_assign_pointer(local->scan_req, req);
                rcu_assign_pointer(local->scan_sdata, sdata);
                return 0;
        }

        if (local->ops->hw_scan) {
                u8 *ies;

                local->hw_scan_ies_bufsize = local->scan_ies_len + req->ie_len;

                if (ieee80211_hw_check(&local->hw, SINGLE_SCAN_ON_ALL_BANDS)) {
                        int i, n_bands = 0;
                        u8 bands_counted = 0;

                        for (i = 0; i < req->n_channels; i++) {
                                if (bands_counted & BIT(req->channels[i]->band))
                                        continue;
                                bands_counted |= BIT(req->channels[i]->band);
                                n_bands++;
                        }

                        local->hw_scan_ies_bufsize *= n_bands;
                }

                local->hw_scan_req = kmalloc(
                                sizeof(*local->hw_scan_req) +
                                req->n_channels * sizeof(req->channels[0]) +
                                local->hw_scan_ies_bufsize, GFP_KERNEL);
                if (!local->hw_scan_req)
                        return -ENOMEM;

                local->hw_scan_req->req.ssids = req->ssids;
                local->hw_scan_req->req.n_ssids = req->n_ssids;
                ies = (u8 *)local->hw_scan_req +
                        sizeof(*local->hw_scan_req) +
                        req->n_channels * sizeof(req->channels[0]);
                local->hw_scan_req->req.ie = ies;
                local->hw_scan_req->req.flags = req->flags;
                eth_broadcast_addr(local->hw_scan_req->req.bssid);
                local->hw_scan_req->req.duration = req->duration;
                local->hw_scan_req->req.duration_mandatory =
                        req->duration_mandatory;

                local->hw_scan_band = 0;

                /*
                 * After allocating local->hw_scan_req, we must
                 * go through until ieee80211_prep_hw_scan(), so
                 * anything that might be changed here and leave
                 * this function early must not go after this
                 * allocation.
                 */
        }

        rcu_assign_pointer(local->scan_req, req);
        rcu_assign_pointer(local->scan_sdata, sdata);

        if (req->flags & NL80211_SCAN_FLAG_RANDOM_ADDR)
                get_random_mask_addr(local->scan_addr,
                                     req->mac_addr,
                                     req->mac_addr_mask);
        else
                memcpy(local->scan_addr, sdata->vif.addr, ETH_ALEN);

        if (local->ops->hw_scan) {
                __set_bit(SCAN_HW_SCANNING, &local->scanning);
        } else if ((req->n_channels == 1) &&
                   (req->channels[0] == local->_oper_chandef.chan)) {
                /*
                 * If we are scanning only on the operating channel
                 * then we do not need to stop normal activities
                 */
                unsigned long next_delay;

                __set_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning);

                ieee80211_recalc_idle(local);

                /* Notify driver scan is starting, keep order of operations
                 * same as normal software scan, in case that matters. */
                drv_sw_scan_start(local, sdata, local->scan_addr);

                ieee80211_configure_filter(local); /* accept probe-responses */

                /* We need to ensure power level is at max for scanning. */
                ieee80211_hw_config(local, 0);

                if ((req->channels[0]->flags & (IEEE80211_CHAN_NO_IR |
                                                IEEE80211_CHAN_RADAR)) ||
                    !req->n_ssids) {
                        next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
                } else {
                        ieee80211_scan_state_send_probe(local, &next_delay);
                        next_delay = IEEE80211_CHANNEL_TIME;
                }

                /* Now, just wait a bit and we are all done! */
                ieee80211_queue_delayed_work(&local->hw, &local->scan_work,
                                             next_delay);
                return 0;
        } else {
                /* Do normal software scan */
                __set_bit(SCAN_SW_SCANNING, &local->scanning);
        }

        ieee80211_recalc_idle(local);

        if (local->ops->hw_scan) {
                WARN_ON(!ieee80211_prep_hw_scan(local));
                rc = drv_hw_scan(local, sdata, local->hw_scan_req);
        } else {
                rc = ieee80211_start_sw_scan(local, sdata);
        }

        if (rc) {
                kfree(local->hw_scan_req);
                local->hw_scan_req = NULL;
                local->scanning = 0;

                ieee80211_recalc_idle(local);

                local->scan_req = NULL;
                RCU_INIT_POINTER(local->scan_sdata, NULL);
        }

        return rc;
}

static unsigned long
ieee80211_scan_get_channel_time(struct ieee80211_channel *chan)
{
        /*
         * TODO: channel switching also consumes quite some time,
         * add that delay as well to get a better estimation
         */
        if (chan->flags & (IEEE80211_CHAN_NO_IR | IEEE80211_CHAN_RADAR))
                return IEEE80211_PASSIVE_CHANNEL_TIME;
        return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
}

static void ieee80211_scan_state_decision(struct ieee80211_local *local,
                                          unsigned long *next_delay)
{
        bool associated = false;
        bool tx_empty = true;
        bool bad_latency;
        struct ieee80211_sub_if_data *sdata;
        struct ieee80211_channel *next_chan;
        enum mac80211_scan_state next_scan_state;
        struct cfg80211_scan_request *scan_req;

        /*
         * check if at least one STA interface is associated,
         * check if at least one STA interface has pending tx frames
         * and grab the lowest used beacon interval
         */
        mutex_lock(&local->iflist_mtx);
        list_for_each_entry(sdata, &local->interfaces, list) {
                if (!ieee80211_sdata_running(sdata))
                        continue;

                if (sdata->vif.type == NL80211_IFTYPE_STATION) {
                        if (sdata->u.mgd.associated) {
                                associated = true;

                                if (!qdisc_all_tx_empty(sdata->dev)) {
                                        tx_empty = false;
                                        break;
                                }
                        }
                }
        }
        mutex_unlock(&local->iflist_mtx);

        scan_req = rcu_dereference_protected(local->scan_req,
                                             lockdep_is_held(&local->mtx));

        next_chan = scan_req->channels[local->scan_channel_idx];

        /*
         * we're currently scanning a different channel, let's
         * see if we can scan another channel without interfering
         * with the current traffic situation.
         *
         * Keep good latency, do not stay off-channel more than 125 ms.
         */

        bad_latency = time_after(jiffies +
                                 ieee80211_scan_get_channel_time(next_chan),
                                 local->leave_oper_channel_time + HZ / 8);

        if (associated && !tx_empty) {
                if (scan_req->flags & NL80211_SCAN_FLAG_LOW_PRIORITY)
                        next_scan_state = SCAN_ABORT;
                else
                        next_scan_state = SCAN_SUSPEND;
        } else if (associated && bad_latency) {
                next_scan_state = SCAN_SUSPEND;
        } else {
                next_scan_state = SCAN_SET_CHANNEL;
        }

        local->next_scan_state = next_scan_state;

        *next_delay = 0;
}

static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
                                             unsigned long *next_delay)
{
        int skip;
        struct ieee80211_channel *chan;
        enum nl80211_bss_scan_width oper_scan_width;
        struct cfg80211_scan_request *scan_req;

        scan_req = rcu_dereference_protected(local->scan_req,
                                             lockdep_is_held(&local->mtx));

        skip = 0;
        chan = scan_req->channels[local->scan_channel_idx];

        local->scan_chandef.chan = chan;
        local->scan_chandef.center_freq1 = chan->center_freq;
        local->scan_chandef.center_freq2 = 0;
        switch (scan_req->scan_width) {
        case NL80211_BSS_CHAN_WIDTH_5:
                local->scan_chandef.width = NL80211_CHAN_WIDTH_5;
                break;
        case NL80211_BSS_CHAN_WIDTH_10:
                local->scan_chandef.width = NL80211_CHAN_WIDTH_10;
                break;
        case NL80211_BSS_CHAN_WIDTH_20:
                /* If scanning on oper channel, use whatever channel-type
                 * is currently in use.
                 */
                oper_scan_width = cfg80211_chandef_to_scan_width(
                                        &local->_oper_chandef);
                if (chan == local->_oper_chandef.chan &&
                    oper_scan_width == scan_req->scan_width)
                        local->scan_chandef = local->_oper_chandef;
                else
                        local->scan_chandef.width = NL80211_CHAN_WIDTH_20_NOHT;
                break;
        }

        if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
                skip = 1;

        /* advance state machine to next channel/band */
        local->scan_channel_idx++;

        if (skip) {
                /* if we skip this channel return to the decision state */
                local->next_scan_state = SCAN_DECISION;
                return;
        }

        /*
         * Probe delay is used to update the NAV, cf. 11.1.3.2.2
         * (which unfortunately doesn't say _why_ step a) is done,
         * but it waits for the probe delay or until a frame is
         * received - and the received frame would update the NAV).
         * For now, we do not support waiting until a frame is
         * received.
         *
         * In any case, it is not necessary for a passive scan.
         */
        if ((chan->flags & (IEEE80211_CHAN_NO_IR | IEEE80211_CHAN_RADAR)) ||
            !scan_req->n_ssids) {
                *next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
                local->next_scan_state = SCAN_DECISION;
                return;
        }

        /* active scan, send probes */
        *next_delay = IEEE80211_PROBE_DELAY;
        local->next_scan_state = SCAN_SEND_PROBE;
}

static void ieee80211_scan_state_suspend(struct ieee80211_local *local,
                                         unsigned long *next_delay)
{
        /* switch back to the operating channel */
        local->scan_chandef.chan = NULL;
        ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);

        /* disable PS */
        ieee80211_offchannel_return(local);

        *next_delay = HZ / 5;
        /* afterwards, resume scan & go to next channel */
        local->next_scan_state = SCAN_RESUME;
}

static void ieee80211_scan_state_resume(struct ieee80211_local *local,
                                        unsigned long *next_delay)
{
        ieee80211_offchannel_stop_vifs(local);

        if (local->ops->flush) {
                ieee80211_flush_queues(local, NULL, false);
                *next_delay = 0;
        } else
                *next_delay = HZ / 10;

        /* remember when we left the operating channel */
        local->leave_oper_channel_time = jiffies;

        /* advance to the next channel to be scanned */
        local->next_scan_state = SCAN_SET_CHANNEL;
}

void ieee80211_scan_work(struct work_struct *work)
{
        struct ieee80211_local *local =
                container_of(work, struct ieee80211_local, scan_work.work);
        struct ieee80211_sub_if_data *sdata;
        struct cfg80211_scan_request *scan_req;
        unsigned long next_delay = 0;
        bool aborted;

        mutex_lock(&local->mtx);

        if (!ieee80211_can_run_worker(local)) {
                aborted = true;
                goto out_complete;
        }

        sdata = rcu_dereference_protected(local->scan_sdata,
                                          lockdep_is_held(&local->mtx));
        scan_req = rcu_dereference_protected(local->scan_req,
                                             lockdep_is_held(&local->mtx));

        /* When scanning on-channel, the first-callback means completed. */
        if (test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning)) {
                aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
                goto out_complete;
        }

        if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) {
                aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
                goto out_complete;
        }

        if (!sdata || !scan_req)
                goto out;

        if (!local->scanning) {
                int rc;

                RCU_INIT_POINTER(local->scan_req, NULL);
                RCU_INIT_POINTER(local->scan_sdata, NULL);

                rc = __ieee80211_start_scan(sdata, scan_req);
                if (rc) {
                        /* need to complete scan in cfg80211 */
                        rcu_assign_pointer(local->scan_req, scan_req);
                        aborted = true;
                        goto out_complete;
                } else
                        goto out;
        }

        /*
         * as long as no delay is required advance immediately
         * without scheduling a new work
         */
        do {
                if (!ieee80211_sdata_running(sdata)) {
                        aborted = true;
                        goto out_complete;
                }

                switch (local->next_scan_state) {
                case SCAN_DECISION:
                        /* if no more bands/channels left, complete scan */
                        if (local->scan_channel_idx >= scan_req->n_channels) {
                                aborted = false;
                                goto out_complete;
                        }
                        ieee80211_scan_state_decision(local, &next_delay);
                        break;
                case SCAN_SET_CHANNEL:
                        ieee80211_scan_state_set_channel(local, &next_delay);
                        break;
                case SCAN_SEND_PROBE:
                        ieee80211_scan_state_send_probe(local, &next_delay);
                        break;
                case SCAN_SUSPEND:
                        ieee80211_scan_state_suspend(local, &next_delay);
                        break;
                case SCAN_RESUME:
                        ieee80211_scan_state_resume(local, &next_delay);
                        break;
                case SCAN_ABORT:
                        aborted = true;
                        goto out_complete;
                }
        } while (next_delay == 0);

        ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
        goto out;

out_complete:
        __ieee80211_scan_completed(&local->hw, aborted);
out:
        mutex_unlock(&local->mtx);
}

int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
                           struct cfg80211_scan_request *req)
{
        int res;

        mutex_lock(&sdata->local->mtx);
        res = __ieee80211_start_scan(sdata, req);
        mutex_unlock(&sdata->local->mtx);

        return res;
}

int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
                                const u8 *ssid, u8 ssid_len,
                                struct ieee80211_channel **channels,
                                unsigned int n_channels,
                                enum nl80211_bss_scan_width scan_width)
{
        struct ieee80211_local *local = sdata->local;
        int ret = -EBUSY, i, n_ch = 0;
        enum nl80211_band band;

        mutex_lock(&local->mtx);

        /* busy scanning */
        if (local->scan_req)
                goto unlock;

        /* fill internal scan request */
        if (!channels) {
                int max_n;

                for (band = 0; band < NUM_NL80211_BANDS; band++) {
                        if (!local->hw.wiphy->bands[band])

                                continue;

                        max_n = local->hw.wiphy->bands[band]->n_channels;
                        for (i = 0; i < max_n; i++) {
                                struct ieee80211_channel *tmp_ch =
                                    &local->hw.wiphy->bands[band]->channels[i];

                                if (tmp_ch->flags & (IEEE80211_CHAN_NO_IR |
                                                     IEEE80211_CHAN_DISABLED))
                                        continue;

                                local->int_scan_req->channels[n_ch] = tmp_ch;
                                n_ch++;
                        }
                }

                if (WARN_ON_ONCE(n_ch == 0))
                        goto unlock;

                local->int_scan_req->n_channels = n_ch;
        } else {
                for (i = 0; i < n_channels; i++) {
                        if (channels[i]->flags & (IEEE80211_CHAN_NO_IR |
                                                  IEEE80211_CHAN_DISABLED))
                                continue;

                        local->int_scan_req->channels[n_ch] = channels[i];
                        n_ch++;
                }

                if (WARN_ON_ONCE(n_ch == 0))
                        goto unlock;

                local->int_scan_req->n_channels = n_ch;
        }

        local->int_scan_req->ssids = &local->scan_ssid;
        local->int_scan_req->n_ssids = 1;
        local->int_scan_req->scan_width = scan_width;
        memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
        local->int_scan_req->ssids[0].ssid_len = ssid_len;

        ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
 unlock:
        mutex_unlock(&local->mtx);
        return ret;
}

/*
 * Only call this function when a scan can't be queued -- under RTNL.
 */
void ieee80211_scan_cancel(struct ieee80211_local *local)
{
        /*
         * We are canceling software scan, or deferred scan that was not
         * yet really started (see __ieee80211_start_scan ).
         *
         * Regarding hardware scan:
         * - we can not call  __ieee80211_scan_completed() as when
         *   SCAN_HW_SCANNING bit is set this function change
         *   local->hw_scan_req to operate on 5G band, what race with
         *   driver which can use local->hw_scan_req
         *
         * - we can not cancel scan_work since driver can schedule it
         *   by ieee80211_scan_completed(..., true) to finish scan
         *
         * Hence we only call the cancel_hw_scan() callback, but the low-level
         * driver is still responsible for calling ieee80211_scan_completed()
         * after the scan was completed/aborted.
         */

        mutex_lock(&local->mtx);
        if (!local->scan_req)
                goto out;

        /*
         * We have a scan running and the driver already reported completion,
         * but the worker hasn't run yet or is stuck on the mutex - mark it as
         * cancelled.
         */
        if (test_bit(SCAN_HW_SCANNING, &local->scanning) &&
            test_bit(SCAN_COMPLETED, &local->scanning)) {
                set_bit(SCAN_HW_CANCELLED, &local->scanning);
                goto out;
        }

        if (test_bit(SCAN_HW_SCANNING, &local->scanning)) {
                /*
                 * Make sure that __ieee80211_scan_completed doesn't trigger a
                 * scan on another band.
                 */
                set_bit(SCAN_HW_CANCELLED, &local->scanning);
                if (local->ops->cancel_hw_scan)
                        drv_cancel_hw_scan(local,
                                rcu_dereference_protected(local->scan_sdata,
                                                lockdep_is_held(&local->mtx)));
                goto out;
        }

        /*
         * If the work is currently running, it must be blocked on
         * the mutex, but we'll set scan_sdata = NULL and it'll
         * simply exit once it acquires the mutex.
         */
        cancel_delayed_work(&local->scan_work);
        /* and clean up */
        memset(&local->scan_info, 0, sizeof(local->scan_info));
        __ieee80211_scan_completed(&local->hw, true);
out:
        mutex_unlock(&local->mtx);
}

int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
                                        struct cfg80211_sched_scan_request *req)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_scan_ies sched_scan_ies = {};
        struct cfg80211_chan_def chandef;
        int ret, i, iebufsz, num_bands = 0;
        u32 rate_masks[NUM_NL80211_BANDS] = {};
        u8 bands_used = 0;
        u8 *ie;

        iebufsz = local->scan_ies_len + req->ie_len;

        lockdep_assert_held(&local->mtx);

        if (!local->ops->sched_scan_start)
                return -ENOTSUPP;

        for (i = 0; i < NUM_NL80211_BANDS; i++) {
                if (local->hw.wiphy->bands[i]) {
                        bands_used |= BIT(i);
                        rate_masks[i] = (u32) -1;
                        num_bands++;
                }
        }

        ie = kzalloc(num_bands * iebufsz, GFP_KERNEL);
        if (!ie) {
                ret = -ENOMEM;
                goto out;
        }

        ieee80211_prepare_scan_chandef(&chandef, req->scan_width);

        ieee80211_build_preq_ies(local, ie, num_bands * iebufsz,
                                 &sched_scan_ies, req->ie,
                                 req->ie_len, bands_used, rate_masks, &chandef);

        ret = drv_sched_scan_start(local, sdata, req, &sched_scan_ies);
        if (ret == 0) {
                rcu_assign_pointer(local->sched_scan_sdata, sdata);
                rcu_assign_pointer(local->sched_scan_req, req);
        }

        kfree(ie);

out:
        if (ret) {
                /* Clean in case of failure after HW restart or upon resume. */
                RCU_INIT_POINTER(local->sched_scan_sdata, NULL);
                RCU_INIT_POINTER(local->sched_scan_req, NULL);
        }

        return ret;
}

int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
                                       struct cfg80211_sched_scan_request *req)
{
        struct ieee80211_local *local = sdata->local;
        int ret;

        mutex_lock(&local->mtx);

        if (rcu_access_pointer(local->sched_scan_sdata)) {
                mutex_unlock(&local->mtx);
                return -EBUSY;
        }

        ret = __ieee80211_request_sched_scan_start(sdata, req);

        mutex_unlock(&local->mtx);
        return ret;
}

int ieee80211_request_sched_scan_stop(struct ieee80211_local *local)
{
        struct ieee80211_sub_if_data *sched_scan_sdata;
        int ret = -ENOENT;

        mutex_lock(&local->mtx);

        if (!local->ops->sched_scan_stop) {
                ret = -ENOTSUPP;
                goto out;
        }

        /* We don't want to restart sched scan anymore. */
        RCU_INIT_POINTER(local->sched_scan_req, NULL);

        sched_scan_sdata = rcu_dereference_protected(local->sched_scan_sdata,
                                                lockdep_is_held(&local->mtx));
        if (sched_scan_sdata) {
                ret = drv_sched_scan_stop(local, sched_scan_sdata);
                if (!ret)
                        RCU_INIT_POINTER(local->sched_scan_sdata, NULL);
        }
out:
        mutex_unlock(&local->mtx);

        return ret;
}

void ieee80211_sched_scan_results(struct ieee80211_hw *hw)
{
        struct ieee80211_local *local = hw_to_local(hw);

        trace_api_sched_scan_results(local);

        cfg80211_sched_scan_results(hw->wiphy, 0);
}
EXPORT_SYMBOL(ieee80211_sched_scan_results);

void ieee80211_sched_scan_end(struct ieee80211_local *local)
{
        mutex_lock(&local->mtx);

        if (!rcu_access_pointer(local->sched_scan_sdata)) {
                mutex_unlock(&local->mtx);
                return;
        }

        RCU_INIT_POINTER(local->sched_scan_sdata, NULL);

        /* If sched scan was aborted by the driver. */
        RCU_INIT_POINTER(local->sched_scan_req, NULL);

        mutex_unlock(&local->mtx);

        cfg80211_sched_scan_stopped(local->hw.wiphy, 0);
}

void ieee80211_sched_scan_stopped_work(struct work_struct *work)
{
        struct ieee80211_local *local =
                container_of(work, struct ieee80211_local,
                             sched_scan_stopped_work);

        ieee80211_sched_scan_end(local);
}

void ieee80211_sched_scan_stopped(struct ieee80211_hw *hw)
{
        struct ieee80211_local *local = hw_to_local(hw);

        trace_api_sched_scan_stopped(local);

        /*
         * this shouldn't really happen, so for simplicity
         * simply ignore it, and let mac80211 reconfigure
         * the sched scan later on.
         */
        if (local->in_reconfig)
                return;

        schedule_work(&local->sched_scan_stopped_work);
}
EXPORT_SYMBOL(ieee80211_sched_scan_stopped);