tx.c

Go to the documentation of this file.

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <[email protected]>
 * Copyright 2007   Johannes Berg <[email protected]>
 *
 * 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.
 *
 *
 * Transmit and frame generation functions.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/etherdevice.h>
#include <linux/bitmap.h>
#include <linux/rcupdate.h>
#include <linux/export.h>
#include <net/net_namespace.h>
#include <net/ieee80211_radiotap.h>
#include <net/cfg80211.h>
#include <net/mac80211.h>
#include <asm/unaligned.h>

#include "ieee80211_i.h"
#include "driver-ops.h"
#include "led.h"
#include "mesh.h"
#include "wep.h"
#include "wpa.h"
#include "wme.h"
#include "rate.h"

/* misc utils */

static __le16 ieee80211_duration(struct ieee80211_tx_data *tx,
                 struct sk_buff *skb, int group_addr,
                 int next_frag_len)
{
    int rate, mrate, erp, dur, i;
    struct ieee80211_rate *txrate;
    struct ieee80211_local *local = tx->local;
    struct ieee80211_supported_band *sband;
    struct ieee80211_hdr *hdr;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

    /* assume HW handles this */
    if (info->control.rates[0].flags & IEEE80211_TX_RC_MCS)
        return 0;

    /* uh huh? */
    if (WARN_ON_ONCE(info->control.rates[0].idx < 0))
        return 0;

    sband = local->hw.wiphy->bands[info->band];
    txrate = &sband->bitrates[info->control.rates[0].idx];

    erp = txrate->flags & IEEE80211_RATE_ERP_G;

    /*
     * data and mgmt (except PS Poll):
     * - during CFP: 32768
     * - during contention period:
     *   if addr1 is group address: 0
     *   if more fragments = 0 and addr1 is individual address: time to
     *      transmit one ACK plus SIFS
     *   if more fragments = 1 and addr1 is individual address: time to
     *      transmit next fragment plus 2 x ACK plus 3 x SIFS
     *
     * IEEE 802.11, 9.6:
     * - control response frame (CTS or ACK) shall be transmitted using the
     *   same rate as the immediately previous frame in the frame exchange
     *   sequence, if this rate belongs to the PHY mandatory rates, or else
     *   at the highest possible rate belonging to the PHY rates in the
     *   BSSBasicRateSet
     */
    hdr = (struct ieee80211_hdr *)skb->data;
    if (ieee80211_is_ctl(hdr->frame_control)) {
        /* TODO: These control frames are not currently sent by
         * mac80211, but should they be implemented, this function
         * needs to be updated to support duration field calculation.
         *
         * RTS: time needed to transmit pending data/mgmt frame plus
         *    one CTS frame plus one ACK frame plus 3 x SIFS
         * CTS: duration of immediately previous RTS minus time
         *    required to transmit CTS and its SIFS
         * ACK: 0 if immediately previous directed data/mgmt had
         *    more=0, with more=1 duration in ACK frame is duration
         *    from previous frame minus time needed to transmit ACK
         *    and its SIFS
         * PS Poll: BIT(15) | BIT(14) | aid
         */
        return 0;
    }

    /* data/mgmt */
    if (0 /* FIX: data/mgmt during CFP */)
        return cpu_to_le16(32768);

    if (group_addr) /* Group address as the destination - no ACK */
        return 0;

    /* Individual destination address:
     * IEEE 802.11, Ch. 9.6 (after IEEE 802.11g changes)
     * CTS and ACK frames shall be transmitted using the highest rate in
     * basic rate set that is less than or equal to the rate of the
     * immediately previous frame and that is using the same modulation
     * (CCK or OFDM). If no basic rate set matches with these requirements,
     * the highest mandatory rate of the PHY that is less than or equal to
     * the rate of the previous frame is used.
     * Mandatory rates for IEEE 802.11g PHY: 1, 2, 5.5, 11, 6, 12, 24 Mbps
     */
    rate = -1;
    /* use lowest available if everything fails */
    mrate = sband->bitrates[0].bitrate;
    for (i = 0; i < sband->n_bitrates; i++) {
        struct ieee80211_rate *r = &sband->bitrates[i];

        if (r->bitrate > txrate->bitrate)
            break;

        if (tx->sdata->vif.bss_conf.basic_rates & BIT(i))
            rate = r->bitrate;

        switch (sband->band) {
        case IEEE80211_BAND_2GHZ: {
            u32 flag;
            if (tx->sdata->flags & IEEE80211_SDATA_OPERATING_GMODE)
                flag = IEEE80211_RATE_MANDATORY_G;
            else
                flag = IEEE80211_RATE_MANDATORY_B;
            if (r->flags & flag)
                mrate = r->bitrate;
            break;
        }
        case IEEE80211_BAND_5GHZ:
            if (r->flags & IEEE80211_RATE_MANDATORY_A)
                mrate = r->bitrate;
            break;
        case IEEE80211_BAND_60GHZ:
            /* TODO, for now fall through */
        case IEEE80211_NUM_BANDS:
            WARN_ON(1);
            break;
        }
    }
    if (rate == -1) {
        /* No matching basic rate found; use highest suitable mandatory
         * PHY rate */
        rate = mrate;
    }

    /* Don't calculate ACKs for QoS Frames with NoAck Policy set */
    if (ieee80211_is_data_qos(hdr->frame_control) &&
        *(ieee80211_get_qos_ctl(hdr)) & IEEE80211_QOS_CTL_ACK_POLICY_NOACK)
        dur = 0;
    else
        /* Time needed to transmit ACK
         * (10 bytes + 4-byte FCS = 112 bits) plus SIFS; rounded up
         * to closest integer */
        dur = ieee80211_frame_duration(sband->band, 10, rate, erp,
                tx->sdata->vif.bss_conf.use_short_preamble);

    if (next_frag_len) {
        /* Frame is fragmented: duration increases with time needed to
         * transmit next fragment plus ACK and 2 x SIFS. */
        dur *= 2; /* ACK + SIFS */
        /* next fragment */
        dur += ieee80211_frame_duration(sband->band, next_frag_len,
                txrate->bitrate, erp,
                tx->sdata->vif.bss_conf.use_short_preamble);
    }

    return cpu_to_le16(dur);
}

/* tx handlers */
static ieee80211_tx_result debug_noinline
ieee80211_tx_h_dynamic_ps(struct ieee80211_tx_data *tx)
{
    struct ieee80211_local *local = tx->local;
    struct ieee80211_if_managed *ifmgd;

    /* driver doesn't support power save */
    if (!(local->hw.flags & IEEE80211_HW_SUPPORTS_PS))
        return TX_CONTINUE;

    /* hardware does dynamic power save */
    if (local->hw.flags & IEEE80211_HW_SUPPORTS_DYNAMIC_PS)
        return TX_CONTINUE;

    /* dynamic power save disabled */
    if (local->hw.conf.dynamic_ps_timeout <= 0)
        return TX_CONTINUE;

    /* we are scanning, don't enable power save */
    if (local->scanning)
        return TX_CONTINUE;

    if (!local->ps_sdata)
        return TX_CONTINUE;

    /* No point if we're going to suspend */
    if (local->quiescing)
        return TX_CONTINUE;

    /* dynamic ps is supported only in managed mode */
    if (tx->sdata->vif.type != NL80211_IFTYPE_STATION)
        return TX_CONTINUE;

    ifmgd = &tx->sdata->u.mgd;

    /*
     * Don't wakeup from power save if u-apsd is enabled, voip ac has
     * u-apsd enabled and the frame is in voip class. This effectively
     * means that even if all access categories have u-apsd enabled, in
     * practise u-apsd is only used with the voip ac. This is a
     * workaround for the case when received voip class packets do not
     * have correct qos tag for some reason, due the network or the
     * peer application.
     *
     * Note: ifmgd->uapsd_queues access is racy here. If the value is
     * changed via debugfs, user needs to reassociate manually to have
     * everything in sync.
     */
    if ((ifmgd->flags & IEEE80211_STA_UAPSD_ENABLED) &&
        (ifmgd->uapsd_queues & IEEE80211_WMM_IE_STA_QOSINFO_AC_VO) &&
        skb_get_queue_mapping(tx->skb) == IEEE80211_AC_VO)
        return TX_CONTINUE;

    if (local->hw.conf.flags & IEEE80211_CONF_PS) {
        ieee80211_stop_queues_by_reason(&local->hw,
                        IEEE80211_QUEUE_STOP_REASON_PS);
        ifmgd->flags &= ~IEEE80211_STA_NULLFUNC_ACKED;
        ieee80211_queue_work(&local->hw,
                     &local->dynamic_ps_disable_work);
    }

    /* Don't restart the timer if we're not disassociated */
    if (!ifmgd->associated)
        return TX_CONTINUE;

    mod_timer(&local->dynamic_ps_timer, jiffies +
          msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_check_assoc(struct ieee80211_tx_data *tx)
{

    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    bool assoc = false;

    if (unlikely(info->flags & IEEE80211_TX_CTL_INJECTED))
        return TX_CONTINUE;

    if (unlikely(test_bit(SCAN_SW_SCANNING, &tx->local->scanning)) &&
        test_bit(SDATA_STATE_OFFCHANNEL, &tx->sdata->state) &&
        !ieee80211_is_probe_req(hdr->frame_control) &&
        !ieee80211_is_nullfunc(hdr->frame_control))
        /*
         * When software scanning only nullfunc frames (to notify
         * the sleep state to the AP) and probe requests (for the
         * active scan) are allowed, all other frames should not be
         * sent and we should not get here, but if we do
         * nonetheless, drop them to avoid sending them
         * off-channel. See the link below and
         * ieee80211_start_scan() for more.
         *
         * http://article.gmane.org/gmane.linux.kernel.wireless.general/30089
         */
        return TX_DROP;

    if (tx->sdata->vif.type == NL80211_IFTYPE_WDS)
        return TX_CONTINUE;

    if (tx->sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
        return TX_CONTINUE;

    if (tx->flags & IEEE80211_TX_PS_BUFFERED)
        return TX_CONTINUE;

    if (tx->sta)
        assoc = test_sta_flag(tx->sta, WLAN_STA_ASSOC);

    if (likely(tx->flags & IEEE80211_TX_UNICAST)) {
        if (unlikely(!assoc &&
                 ieee80211_is_data(hdr->frame_control))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
            sdata_info(tx->sdata,
                   "dropped data frame to not associated station %pM\n",
                   hdr->addr1);
#endif
            I802_DEBUG_INC(tx->local->tx_handlers_drop_not_assoc);
            return TX_DROP;
        }
    } else if (unlikely(tx->sdata->vif.type == NL80211_IFTYPE_AP &&
                ieee80211_is_data(hdr->frame_control) &&
                !atomic_read(&tx->sdata->u.ap.num_mcast_sta))) {
        /*
         * No associated STAs - no need to send multicast
         * frames.
         */
        return TX_DROP;
    }

    return TX_CONTINUE;
}

/* This function is called whenever the AP is about to exceed the maximum limit
 * of buffered frames for power saving STAs. This situation should not really
 * happen often during normal operation, so dropping the oldest buffered packet
 * from each queue should be OK to make some room for new frames. */
static void purge_old_ps_buffers(struct ieee80211_local *local)
{
    int total = 0, purged = 0;
    struct sk_buff *skb;
    struct ieee80211_sub_if_data *sdata;
    struct sta_info *sta;

    /*
     * virtual interfaces are protected by RCU
     */
    rcu_read_lock();

    list_for_each_entry_rcu(sdata, &local->interfaces, list) {
        struct ieee80211_if_ap *ap;
        if (sdata->vif.type != NL80211_IFTYPE_AP)
            continue;
        ap = &sdata->u.ap;
        skb = skb_dequeue(&ap->ps_bc_buf);
        if (skb) {
            purged++;
            dev_kfree_skb(skb);
        }
        total += skb_queue_len(&ap->ps_bc_buf);
    }

    /*
     * Drop one frame from each station from the lowest-priority
     * AC that has frames at all.
     */
    list_for_each_entry_rcu(sta, &local->sta_list, list) {
        int ac;

        for (ac = IEEE80211_AC_BK; ac >= IEEE80211_AC_VO; ac--) {
            skb = skb_dequeue(&sta->ps_tx_buf[ac]);
            total += skb_queue_len(&sta->ps_tx_buf[ac]);
            if (skb) {
                purged++;
                ieee80211_free_txskb(&local->hw, skb);
                break;
            }
        }
    }

    rcu_read_unlock();

    local->total_ps_buffered = total;
    ps_dbg_hw(&local->hw, "PS buffers full - purged %d frames\n", purged);
}

static ieee80211_tx_result
ieee80211_tx_h_multicast_ps_buf(struct ieee80211_tx_data *tx)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;

    /*
     * broadcast/multicast frame
     *
     * If any of the associated stations is in power save mode,
     * the frame is buffered to be sent after DTIM beacon frame.
     * This is done either by the hardware or us.
     */

    /* powersaving STAs only in AP/VLAN mode */
    if (!tx->sdata->bss)
        return TX_CONTINUE;

    /* no buffering for ordered frames */
    if (ieee80211_has_order(hdr->frame_control))
        return TX_CONTINUE;

    /* no stations in PS mode */
    if (!atomic_read(&tx->sdata->bss->num_sta_ps))
        return TX_CONTINUE;

    info->flags |= IEEE80211_TX_CTL_SEND_AFTER_DTIM;
    if (tx->local->hw.flags & IEEE80211_HW_QUEUE_CONTROL)
        info->hw_queue = tx->sdata->vif.cab_queue;

    /* device releases frame after DTIM beacon */
    if (!(tx->local->hw.flags & IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING))
        return TX_CONTINUE;

    /* buffered in mac80211 */
    if (tx->local->total_ps_buffered >= TOTAL_MAX_TX_BUFFER)
        purge_old_ps_buffers(tx->local);

    if (skb_queue_len(&tx->sdata->bss->ps_bc_buf) >= AP_MAX_BC_BUFFER) {
        ps_dbg(tx->sdata,
               "BC TX buffer full - dropping the oldest frame\n");
        dev_kfree_skb(skb_dequeue(&tx->sdata->bss->ps_bc_buf));
    } else
        tx->local->total_ps_buffered++;

    skb_queue_tail(&tx->sdata->bss->ps_bc_buf, tx->skb);

    return TX_QUEUED;
}

static int ieee80211_use_mfp(__le16 fc, struct sta_info *sta,
                 struct sk_buff *skb)
{
    if (!ieee80211_is_mgmt(fc))
        return 0;

    if (sta == NULL || !test_sta_flag(sta, WLAN_STA_MFP))
        return 0;

    if (!ieee80211_is_robust_mgmt_frame((struct ieee80211_hdr *)
                        skb->data))
        return 0;

    return 1;
}

static ieee80211_tx_result
ieee80211_tx_h_unicast_ps_buf(struct ieee80211_tx_data *tx)
{
    struct sta_info *sta = tx->sta;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
    struct ieee80211_local *local = tx->local;

    if (unlikely(!sta))
        return TX_CONTINUE;

    if (unlikely((test_sta_flag(sta, WLAN_STA_PS_STA) ||
              test_sta_flag(sta, WLAN_STA_PS_DRIVER)) &&
             !(info->flags & IEEE80211_TX_CTL_NO_PS_BUFFER))) {
        int ac = skb_get_queue_mapping(tx->skb);

        /* only deauth, disassoc and action are bufferable MMPDUs */
        if (ieee80211_is_mgmt(hdr->frame_control) &&
            !ieee80211_is_deauth(hdr->frame_control) &&
            !ieee80211_is_disassoc(hdr->frame_control) &&
            !ieee80211_is_action(hdr->frame_control)) {
            info->flags |= IEEE80211_TX_CTL_NO_PS_BUFFER;
            return TX_CONTINUE;
        }

        ps_dbg(sta->sdata, "STA %pM aid %d: PS buffer for AC %d\n",
               sta->sta.addr, sta->sta.aid, ac);
        if (tx->local->total_ps_buffered >= TOTAL_MAX_TX_BUFFER)
            purge_old_ps_buffers(tx->local);
        if (skb_queue_len(&sta->ps_tx_buf[ac]) >= STA_MAX_TX_BUFFER) {
            struct sk_buff *old = skb_dequeue(&sta->ps_tx_buf[ac]);
            ps_dbg(tx->sdata,
                   "STA %pM TX buffer for AC %d full - dropping oldest frame\n",
                   sta->sta.addr, ac);
            ieee80211_free_txskb(&local->hw, old);
        } else
            tx->local->total_ps_buffered++;

        info->control.jiffies = jiffies;
        info->control.vif = &tx->sdata->vif;
        info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
        skb_queue_tail(&sta->ps_tx_buf[ac], tx->skb);

        if (!timer_pending(&local->sta_cleanup))
            mod_timer(&local->sta_cleanup,
                  round_jiffies(jiffies +
                        STA_INFO_CLEANUP_INTERVAL));

        /*
         * We queued up some frames, so the TIM bit might
         * need to be set, recalculate it.
         */
        sta_info_recalc_tim(sta);

        return TX_QUEUED;
    } else if (unlikely(test_sta_flag(sta, WLAN_STA_PS_STA))) {
        ps_dbg(tx->sdata,
               "STA %pM in PS mode, but polling/in SP -> send frame\n",
               sta->sta.addr);
    }

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_ps_buf(struct ieee80211_tx_data *tx)
{
    if (unlikely(tx->flags & IEEE80211_TX_PS_BUFFERED))
        return TX_CONTINUE;

    if (tx->flags & IEEE80211_TX_UNICAST)
        return ieee80211_tx_h_unicast_ps_buf(tx);
    else
        return ieee80211_tx_h_multicast_ps_buf(tx);
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_check_control_port_protocol(struct ieee80211_tx_data *tx)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);

    if (unlikely(tx->sdata->control_port_protocol == tx->skb->protocol &&
             tx->sdata->control_port_no_encrypt))
        info->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
{
    struct ieee80211_key *key;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;

    if (unlikely(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT))
        tx->key = NULL;
    else if (tx->sta && (key = rcu_dereference(tx->sta->ptk)))
        tx->key = key;
    else if (ieee80211_is_mgmt(hdr->frame_control) &&
         is_multicast_ether_addr(hdr->addr1) &&
         ieee80211_is_robust_mgmt_frame(hdr) &&
         (key = rcu_dereference(tx->sdata->default_mgmt_key)))
        tx->key = key;
    else if (is_multicast_ether_addr(hdr->addr1) &&
         (key = rcu_dereference(tx->sdata->default_multicast_key)))
        tx->key = key;
    else if (!is_multicast_ether_addr(hdr->addr1) &&
         (key = rcu_dereference(tx->sdata->default_unicast_key)))
        tx->key = key;
    else if (info->flags & IEEE80211_TX_CTL_INJECTED)
        tx->key = NULL;
    else if (!tx->sdata->drop_unencrypted)
        tx->key = NULL;
    else if (tx->skb->protocol == tx->sdata->control_port_protocol)
        tx->key = NULL;
    else if (ieee80211_is_robust_mgmt_frame(hdr) &&
         !(ieee80211_is_action(hdr->frame_control) &&
           tx->sta && test_sta_flag(tx->sta, WLAN_STA_MFP)))
        tx->key = NULL;
    else if (ieee80211_is_mgmt(hdr->frame_control) &&
         !ieee80211_is_robust_mgmt_frame(hdr))
        tx->key = NULL;
    else {
        I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
        return TX_DROP;
    }

    if (tx->key) {
        bool skip_hw = false;

        tx->key->tx_rx_count++;
        /* TODO: add threshold stuff again */

        switch (tx->key->conf.cipher) {
        case WLAN_CIPHER_SUITE_WEP40:
        case WLAN_CIPHER_SUITE_WEP104:
        case WLAN_CIPHER_SUITE_TKIP:
            if (!ieee80211_is_data_present(hdr->frame_control))
                tx->key = NULL;
            break;
        case WLAN_CIPHER_SUITE_CCMP:
            if (!ieee80211_is_data_present(hdr->frame_control) &&
                !ieee80211_use_mfp(hdr->frame_control, tx->sta,
                           tx->skb))
                tx->key = NULL;
            else
                skip_hw = (tx->key->conf.flags &
                       IEEE80211_KEY_FLAG_SW_MGMT_TX) &&
                    ieee80211_is_mgmt(hdr->frame_control);
            break;
        case WLAN_CIPHER_SUITE_AES_CMAC:
            if (!ieee80211_is_mgmt(hdr->frame_control))
                tx->key = NULL;
            break;
        }

        if (unlikely(tx->key && tx->key->flags & KEY_FLAG_TAINTED))
            return TX_DROP;

        if (!skip_hw && tx->key &&
            tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
            info->control.hw_key = &tx->key->conf;
    }

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_rate_ctrl(struct ieee80211_tx_data *tx)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    struct ieee80211_hdr *hdr = (void *)tx->skb->data;
    struct ieee80211_supported_band *sband;
    struct ieee80211_rate *rate;
    int i;
    u32 len;
    bool inval = false, rts = false, short_preamble = false;
    struct ieee80211_tx_rate_control txrc;
    bool assoc = false;

    memset(&txrc, 0, sizeof(txrc));

    sband = tx->local->hw.wiphy->bands[info->band];

    len = min_t(u32, tx->skb->len + FCS_LEN,
             tx->local->hw.wiphy->frag_threshold);

    /* set up the tx rate control struct we give the RC algo */
    txrc.hw = &tx->local->hw;
    txrc.sband = sband;
    txrc.bss_conf = &tx->sdata->vif.bss_conf;
    txrc.skb = tx->skb;
    txrc.reported_rate.idx = -1;
    txrc.rate_idx_mask = tx->sdata->rc_rateidx_mask[info->band];
    if (txrc.rate_idx_mask == (1 << sband->n_bitrates) - 1)
        txrc.max_rate_idx = -1;
    else
        txrc.max_rate_idx = fls(txrc.rate_idx_mask) - 1;
    memcpy(txrc.rate_idx_mcs_mask,
           tx->sdata->rc_rateidx_mcs_mask[info->band],
           sizeof(txrc.rate_idx_mcs_mask));
    txrc.bss = (tx->sdata->vif.type == NL80211_IFTYPE_AP ||
            tx->sdata->vif.type == NL80211_IFTYPE_MESH_POINT ||
            tx->sdata->vif.type == NL80211_IFTYPE_ADHOC);

    /* set up RTS protection if desired */
    if (len > tx->local->hw.wiphy->rts_threshold) {
        txrc.rts = rts = true;
    }

    /*
     * Use short preamble if the BSS can handle it, but not for
     * management frames unless we know the receiver can handle
     * that -- the management frame might be to a station that
     * just wants a probe response.
     */
    if (tx->sdata->vif.bss_conf.use_short_preamble &&
        (ieee80211_is_data(hdr->frame_control) ||
         (tx->sta && test_sta_flag(tx->sta, WLAN_STA_SHORT_PREAMBLE))))
        txrc.short_preamble = short_preamble = true;

    if (tx->sta)
        assoc = test_sta_flag(tx->sta, WLAN_STA_ASSOC);

    /*
     * Lets not bother rate control if we're associated and cannot
     * talk to the sta. This should not happen.
     */
    if (WARN(test_bit(SCAN_SW_SCANNING, &tx->local->scanning) && assoc &&
         !rate_usable_index_exists(sband, &tx->sta->sta),
         "%s: Dropped data frame as no usable bitrate found while "
         "scanning and associated. Target station: "
         "%pM on %d GHz band\n",
         tx->sdata->name, hdr->addr1,
         info->band ? 5 : 2))
        return TX_DROP;

    /*
     * If we're associated with the sta at this point we know we can at
     * least send the frame at the lowest bit rate.
     */
    rate_control_get_rate(tx->sdata, tx->sta, &txrc);

    if (unlikely(info->control.rates[0].idx < 0))
        return TX_DROP;

    if (txrc.reported_rate.idx < 0) {
        txrc.reported_rate = info->control.rates[0];
        if (tx->sta && ieee80211_is_data(hdr->frame_control))
            tx->sta->last_tx_rate = txrc.reported_rate;
    } else if (tx->sta)
        tx->sta->last_tx_rate = txrc.reported_rate;

    if (unlikely(!info->control.rates[0].count))
        info->control.rates[0].count = 1;

    if (WARN_ON_ONCE((info->control.rates[0].count > 1) &&
             (info->flags & IEEE80211_TX_CTL_NO_ACK)))
        info->control.rates[0].count = 1;

    if (is_multicast_ether_addr(hdr->addr1)) {
        /*
         * XXX: verify the rate is in the basic rateset
         */
        return TX_CONTINUE;
    }

    /*
     * set up the RTS/CTS rate as the fastest basic rate
     * that is not faster than the data rate
     *
     * XXX: Should this check all retry rates?
     */
    if (!(info->control.rates[0].flags & IEEE80211_TX_RC_MCS)) {
        s8 baserate = 0;

        rate = &sband->bitrates[info->control.rates[0].idx];

        for (i = 0; i < sband->n_bitrates; i++) {
            /* must be a basic rate */
            if (!(tx->sdata->vif.bss_conf.basic_rates & BIT(i)))
                continue;
            /* must not be faster than the data rate */
            if (sband->bitrates[i].bitrate > rate->bitrate)
                continue;
            /* maximum */
            if (sband->bitrates[baserate].bitrate <
                 sband->bitrates[i].bitrate)
                baserate = i;
        }

        info->control.rts_cts_rate_idx = baserate;
    }

    for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
        /*
         * make sure there's no valid rate following
         * an invalid one, just in case drivers don't
         * take the API seriously to stop at -1.
         */
        if (inval) {
            info->control.rates[i].idx = -1;
            continue;
        }
        if (info->control.rates[i].idx < 0) {
            inval = true;
            continue;
        }

        /*
         * For now assume MCS is already set up correctly, this
         * needs to be fixed.
         */
        if (info->control.rates[i].flags & IEEE80211_TX_RC_MCS) {
            WARN_ON(info->control.rates[i].idx > 76);
            continue;
        }

        /* set up RTS protection if desired */
        if (rts)
            info->control.rates[i].flags |=
                IEEE80211_TX_RC_USE_RTS_CTS;

        /* RC is busted */
        if (WARN_ON_ONCE(info->control.rates[i].idx >=
                 sband->n_bitrates)) {
            info->control.rates[i].idx = -1;
            continue;
        }

        rate = &sband->bitrates[info->control.rates[i].idx];

        /* set up short preamble */
        if (short_preamble &&
            rate->flags & IEEE80211_RATE_SHORT_PREAMBLE)
            info->control.rates[i].flags |=
                IEEE80211_TX_RC_USE_SHORT_PREAMBLE;

        /* set up G protection */
        if (!rts && tx->sdata->vif.bss_conf.use_cts_prot &&
            rate->flags & IEEE80211_RATE_ERP_G)
            info->control.rates[i].flags |=
                IEEE80211_TX_RC_USE_CTS_PROTECT;
    }

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
    u16 *seq;
    u8 *qc;
    int tid;

    /*
     * Packet injection may want to control the sequence
     * number, if we have no matching interface then we
     * neither assign one ourselves nor ask the driver to.
     */
    if (unlikely(info->control.vif->type == NL80211_IFTYPE_MONITOR))
        return TX_CONTINUE;

    if (unlikely(ieee80211_is_ctl(hdr->frame_control)))
        return TX_CONTINUE;

    if (ieee80211_hdrlen(hdr->frame_control) < 24)
        return TX_CONTINUE;

    if (ieee80211_is_qos_nullfunc(hdr->frame_control))
        return TX_CONTINUE;

    /*
     * Anything but QoS data that has a sequence number field
     * (is long enough) gets a sequence number from the global
     * counter.
     */
    if (!ieee80211_is_data_qos(hdr->frame_control)) {
        /* driver should assign sequence number */
        info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
        /* for pure STA mode without beacons, we can do it */
        hdr->seq_ctrl = cpu_to_le16(tx->sdata->sequence_number);
        tx->sdata->sequence_number += 0x10;
        return TX_CONTINUE;
    }

    /*
     * This should be true for injected/management frames only, for
     * management frames we have set the IEEE80211_TX_CTL_ASSIGN_SEQ
     * above since they are not QoS-data frames.
     */
    if (!tx->sta)
        return TX_CONTINUE;

    /* include per-STA, per-TID sequence counter */

    qc = ieee80211_get_qos_ctl(hdr);
    tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
    seq = &tx->sta->tid_seq[tid];

    hdr->seq_ctrl = cpu_to_le16(*seq);

    /* Increase the sequence number. */
    *seq = (*seq + 0x10) & IEEE80211_SCTL_SEQ;

    return TX_CONTINUE;
}

static int ieee80211_fragment(struct ieee80211_tx_data *tx,
                  struct sk_buff *skb, int hdrlen,
                  int frag_threshold)
{
    struct ieee80211_local *local = tx->local;
    struct ieee80211_tx_info *info;
    struct sk_buff *tmp;
    int per_fragm = frag_threshold - hdrlen - FCS_LEN;
    int pos = hdrlen + per_fragm;
    int rem = skb->len - hdrlen - per_fragm;

    if (WARN_ON(rem < 0))
        return -EINVAL;

    /* first fragment was already added to queue by caller */

    while (rem) {
        int fraglen = per_fragm;

        if (fraglen > rem)
            fraglen = rem;
        rem -= fraglen;
        tmp = dev_alloc_skb(local->tx_headroom +
                    frag_threshold +
                    IEEE80211_ENCRYPT_HEADROOM +
                    IEEE80211_ENCRYPT_TAILROOM);
        if (!tmp)
            return -ENOMEM;

        __skb_queue_tail(&tx->skbs, tmp);

        skb_reserve(tmp, local->tx_headroom +
                 IEEE80211_ENCRYPT_HEADROOM);
        /* copy control information */
        memcpy(tmp->cb, skb->cb, sizeof(tmp->cb));

        info = IEEE80211_SKB_CB(tmp);
        info->flags &= ~(IEEE80211_TX_CTL_CLEAR_PS_FILT |
                 IEEE80211_TX_CTL_FIRST_FRAGMENT);

        if (rem)
            info->flags |= IEEE80211_TX_CTL_MORE_FRAMES;

        skb_copy_queue_mapping(tmp, skb);
        tmp->priority = skb->priority;
        tmp->dev = skb->dev;

        /* copy header and data */
        memcpy(skb_put(tmp, hdrlen), skb->data, hdrlen);
        memcpy(skb_put(tmp, fraglen), skb->data + pos, fraglen);

        pos += fraglen;
    }

    /* adjust first fragment's length */
    skb->len = hdrlen + per_fragm;
    return 0;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_fragment(struct ieee80211_tx_data *tx)
{
    struct sk_buff *skb = tx->skb;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (void *)skb->data;
    int frag_threshold = tx->local->hw.wiphy->frag_threshold;
    int hdrlen;
    int fragnum;

    /* no matter what happens, tx->skb moves to tx->skbs */
    __skb_queue_tail(&tx->skbs, skb);
    tx->skb = NULL;

    if (info->flags & IEEE80211_TX_CTL_DONTFRAG)
        return TX_CONTINUE;

    if (tx->local->ops->set_frag_threshold)
        return TX_CONTINUE;

    /*
     * Warn when submitting a fragmented A-MPDU frame and drop it.
     * This scenario is handled in ieee80211_tx_prepare but extra
     * caution taken here as fragmented ampdu may cause Tx stop.
     */
    if (WARN_ON(info->flags & IEEE80211_TX_CTL_AMPDU))
        return TX_DROP;

    hdrlen = ieee80211_hdrlen(hdr->frame_control);

    /* internal error, why isn't DONTFRAG set? */
    if (WARN_ON(skb->len + FCS_LEN <= frag_threshold))
        return TX_DROP;

    /*
     * Now fragment the frame. This will allocate all the fragments and
     * chain them (using skb as the first fragment) to skb->next.
     * During transmission, we will remove the successfully transmitted
     * fragments from this list. When the low-level driver rejects one
     * of the fragments then we will simply pretend to accept the skb
     * but store it away as pending.
     */
    if (ieee80211_fragment(tx, skb, hdrlen, frag_threshold))
        return TX_DROP;

    /* update duration/seq/flags of fragments */
    fragnum = 0;

    skb_queue_walk(&tx->skbs, skb) {
        int next_len;
        const __le16 morefrags = cpu_to_le16(IEEE80211_FCTL_MOREFRAGS);

        hdr = (void *)skb->data;
        info = IEEE80211_SKB_CB(skb);

        if (!skb_queue_is_last(&tx->skbs, skb)) {
            hdr->frame_control |= morefrags;
            /*
             * No multi-rate retries for fragmented frames, that
             * would completely throw off the NAV at other STAs.
             */
            info->control.rates[1].idx = -1;
            info->control.rates[2].idx = -1;
            info->control.rates[3].idx = -1;
            BUILD_BUG_ON(IEEE80211_TX_MAX_RATES != 4);
            info->flags &= ~IEEE80211_TX_CTL_RATE_CTRL_PROBE;
        } else {
            hdr->frame_control &= ~morefrags;
            next_len = 0;
        }
        hdr->seq_ctrl |= cpu_to_le16(fragnum & IEEE80211_SCTL_FRAG);
        fragnum++;
    }

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_stats(struct ieee80211_tx_data *tx)
{
    struct sk_buff *skb;

    if (!tx->sta)
        return TX_CONTINUE;

    tx->sta->tx_packets++;
    skb_queue_walk(&tx->skbs, skb) {
        tx->sta->tx_fragments++;
        tx->sta->tx_bytes += skb->len;
    }

    return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_encrypt(struct ieee80211_tx_data *tx)
{
    if (!tx->key)
        return TX_CONTINUE;

    switch (tx->key->conf.cipher) {
    case WLAN_CIPHER_SUITE_WEP40:
    case WLAN_CIPHER_SUITE_WEP104:
        return ieee80211_crypto_wep_encrypt(tx);
    case WLAN_CIPHER_SUITE_TKIP:
        return ieee80211_crypto_tkip_encrypt(tx);
    case WLAN_CIPHER_SUITE_CCMP:
        return ieee80211_crypto_ccmp_encrypt(tx);
    case WLAN_CIPHER_SUITE_AES_CMAC:
        return ieee80211_crypto_aes_cmac_encrypt(tx);
    default:
        return ieee80211_crypto_hw_encrypt(tx);
    }

    return TX_DROP;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_calculate_duration(struct ieee80211_tx_data *tx)
{
    struct sk_buff *skb;
    struct ieee80211_hdr *hdr;
    int next_len;
    bool group_addr;

    skb_queue_walk(&tx->skbs, skb) {
        hdr = (void *) skb->data;
        if (unlikely(ieee80211_is_pspoll(hdr->frame_control)))
            break; /* must not overwrite AID */
        if (!skb_queue_is_last(&tx->skbs, skb)) {
            struct sk_buff *next = skb_queue_next(&tx->skbs, skb);
            next_len = next->len;
        } else
            next_len = 0;
        group_addr = is_multicast_ether_addr(hdr->addr1);

        hdr->duration_id =
            ieee80211_duration(tx, skb, group_addr, next_len);
    }

    return TX_CONTINUE;
}

/* actual transmit path */

static bool ieee80211_tx_prep_agg(struct ieee80211_tx_data *tx,
                  struct sk_buff *skb,
                  struct ieee80211_tx_info *info,
                  struct tid_ampdu_tx *tid_tx,
                  int tid)
{
    bool queued = false;
    bool reset_agg_timer = false;
    struct sk_buff *purge_skb = NULL;

    if (test_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state)) {
        info->flags |= IEEE80211_TX_CTL_AMPDU;
        reset_agg_timer = true;
    } else if (test_bit(HT_AGG_STATE_WANT_START, &tid_tx->state)) {
        /*
         * nothing -- this aggregation session is being started
         * but that might still fail with the driver
         */
    } else {
        spin_lock(&tx->sta->lock);
        /*
         * Need to re-check now, because we may get here
         *
         *  1) in the window during which the setup is actually
         *     already done, but not marked yet because not all
         *     packets are spliced over to the driver pending
         *     queue yet -- if this happened we acquire the lock
         *     either before or after the splice happens, but
         *     need to recheck which of these cases happened.
         *
         *  2) during session teardown, if the OPERATIONAL bit
         *     was cleared due to the teardown but the pointer
         *     hasn't been assigned NULL yet (or we loaded it
         *     before it was assigned) -- in this case it may
         *     now be NULL which means we should just let the
         *     packet pass through because splicing the frames
         *     back is already done.
         */
        tid_tx = rcu_dereference_protected_tid_tx(tx->sta, tid);

        if (!tid_tx) {
            /* do nothing, let packet pass through */
        } else if (test_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state)) {
            info->flags |= IEEE80211_TX_CTL_AMPDU;
            reset_agg_timer = true;
        } else {
            queued = true;
            info->control.vif = &tx->sdata->vif;
            info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
            __skb_queue_tail(&tid_tx->pending, skb);
            if (skb_queue_len(&tid_tx->pending) > STA_MAX_TX_BUFFER)
                purge_skb = __skb_dequeue(&tid_tx->pending);
        }
        spin_unlock(&tx->sta->lock);

        if (purge_skb)
            ieee80211_free_txskb(&tx->local->hw, purge_skb);
    }

    /* reset session timer */
    if (reset_agg_timer && tid_tx->timeout)
        tid_tx->last_tx = jiffies;

    return queued;
}

/*
 * initialises @tx
 */
static ieee80211_tx_result
ieee80211_tx_prepare(struct ieee80211_sub_if_data *sdata,
             struct ieee80211_tx_data *tx,
             struct sk_buff *skb)
{
    struct ieee80211_local *local = sdata->local;
    struct ieee80211_hdr *hdr;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    int tid;
    u8 *qc;

    memset(tx, 0, sizeof(*tx));
    tx->skb = skb;
    tx->local = local;
    tx->sdata = sdata;
    __skb_queue_head_init(&tx->skbs);

    /*
     * If this flag is set to true anywhere, and we get here,
     * we are doing the needed processing, so remove the flag
     * now.
     */
    info->flags &= ~IEEE80211_TX_INTFL_NEED_TXPROCESSING;

    hdr = (struct ieee80211_hdr *) skb->data;

    if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
        tx->sta = rcu_dereference(sdata->u.vlan.sta);
        if (!tx->sta && sdata->dev->ieee80211_ptr->use_4addr)
            return TX_DROP;
    } else if (info->flags & IEEE80211_TX_CTL_INJECTED ||
           tx->sdata->control_port_protocol == tx->skb->protocol) {
        tx->sta = sta_info_get_bss(sdata, hdr->addr1);
    }
    if (!tx->sta)
        tx->sta = sta_info_get(sdata, hdr->addr1);

    if (tx->sta && ieee80211_is_data_qos(hdr->frame_control) &&
        !ieee80211_is_qos_nullfunc(hdr->frame_control) &&
        (local->hw.flags & IEEE80211_HW_AMPDU_AGGREGATION) &&
        !(local->hw.flags & IEEE80211_HW_TX_AMPDU_SETUP_IN_HW)) {
        struct tid_ampdu_tx *tid_tx;

        qc = ieee80211_get_qos_ctl(hdr);
        tid = *qc & IEEE80211_QOS_CTL_TID_MASK;

        tid_tx = rcu_dereference(tx->sta->ampdu_mlme.tid_tx[tid]);
        if (tid_tx) {
            bool queued;

            queued = ieee80211_tx_prep_agg(tx, skb, info,
                               tid_tx, tid);

            if (unlikely(queued))
                return TX_QUEUED;
        }
    }

    if (is_multicast_ether_addr(hdr->addr1)) {
        tx->flags &= ~IEEE80211_TX_UNICAST;
        info->flags |= IEEE80211_TX_CTL_NO_ACK;
    } else
        tx->flags |= IEEE80211_TX_UNICAST;

    if (!(info->flags & IEEE80211_TX_CTL_DONTFRAG)) {
        if (!(tx->flags & IEEE80211_TX_UNICAST) ||
            skb->len + FCS_LEN <= local->hw.wiphy->frag_threshold ||
            info->flags & IEEE80211_TX_CTL_AMPDU)
            info->flags |= IEEE80211_TX_CTL_DONTFRAG;
    }

    if (!tx->sta)
        info->flags |= IEEE80211_TX_CTL_CLEAR_PS_FILT;
    else if (test_and_clear_sta_flag(tx->sta, WLAN_STA_CLEAR_PS_FILT))
        info->flags |= IEEE80211_TX_CTL_CLEAR_PS_FILT;

    info->flags |= IEEE80211_TX_CTL_FIRST_FRAGMENT;

    return TX_CONTINUE;
}

static bool ieee80211_tx_frags(struct ieee80211_local *local,
                   struct ieee80211_vif *vif,
                   struct ieee80211_sta *sta,
                   struct sk_buff_head *skbs,
                   bool txpending)
{
    struct ieee80211_tx_control control;
    struct sk_buff *skb, *tmp;
    unsigned long flags;

    skb_queue_walk_safe(skbs, skb, tmp) {
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        int q = info->hw_queue;

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        if (WARN_ON_ONCE(q >= local->hw.queues)) {
            __skb_unlink(skb, skbs);
            ieee80211_free_txskb(&local->hw, skb);
            continue;
        }
#endif

        spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
        if (local->queue_stop_reasons[q] ||
            (!txpending && !skb_queue_empty(&local->pending[q]))) {
            /*
             * Since queue is stopped, queue up frames for later
             * transmission from the tx-pending tasklet when the
             * queue is woken again.
             */
            if (txpending)
                skb_queue_splice_init(skbs, &local->pending[q]);
            else
                skb_queue_splice_tail_init(skbs,
                               &local->pending[q]);

            spin_unlock_irqrestore(&local->queue_stop_reason_lock,
                           flags);
            return false;
        }
        spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);

        info->control.vif = vif;
        control.sta = sta;

        __skb_unlink(skb, skbs);
        drv_tx(local, &control, skb);
    }

    return true;
}

/*
 * Returns false if the frame couldn't be transmitted but was queued instead.
 */
static bool __ieee80211_tx(struct ieee80211_local *local,
               struct sk_buff_head *skbs, int led_len,
               struct sta_info *sta, bool txpending)
{
    struct ieee80211_tx_info *info;
    struct ieee80211_sub_if_data *sdata;
    struct ieee80211_vif *vif;
    struct ieee80211_sta *pubsta;
    struct sk_buff *skb;
    bool result = true;
    __le16 fc;

    if (WARN_ON(skb_queue_empty(skbs)))
        return true;

    skb = skb_peek(skbs);
    fc = ((struct ieee80211_hdr *)skb->data)->frame_control;
    info = IEEE80211_SKB_CB(skb);
    sdata = vif_to_sdata(info->control.vif);
    if (sta && !sta->uploaded)
        sta = NULL;

    if (sta)
        pubsta = &sta->sta;
    else
        pubsta = NULL;

    switch (sdata->vif.type) {
    case NL80211_IFTYPE_MONITOR:
        sdata = rcu_dereference(local->monitor_sdata);
        if (sdata) {
            vif = &sdata->vif;
            info->hw_queue =
                vif->hw_queue[skb_get_queue_mapping(skb)];
        } else if (local->hw.flags & IEEE80211_HW_QUEUE_CONTROL) {
            dev_kfree_skb(skb);
            return true;
        } else
            vif = NULL;
        break;
    case NL80211_IFTYPE_AP_VLAN:
        sdata = container_of(sdata->bss,
                     struct ieee80211_sub_if_data, u.ap);
        /* fall through */
    default:
        vif = &sdata->vif;
        break;
    }

    result = ieee80211_tx_frags(local, vif, pubsta, skbs,
                    txpending);

    ieee80211_tpt_led_trig_tx(local, fc, led_len);
    ieee80211_led_tx(local, 1);

    WARN_ON_ONCE(!skb_queue_empty(skbs));

    return result;
}

/*
 * Invoke TX handlers, return 0 on success and non-zero if the
 * frame was dropped or queued.
 */
static int invoke_tx_handlers(struct ieee80211_tx_data *tx)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
    ieee80211_tx_result res = TX_DROP;

#define CALL_TXH(txh) \
    do {                \
        res = txh(tx);      \
        if (res != TX_CONTINUE) \
            goto txh_done;  \
    } while (0)

    CALL_TXH(ieee80211_tx_h_dynamic_ps);
    CALL_TXH(ieee80211_tx_h_check_assoc);
    CALL_TXH(ieee80211_tx_h_ps_buf);
    CALL_TXH(ieee80211_tx_h_check_control_port_protocol);
    CALL_TXH(ieee80211_tx_h_select_key);
    if (!(tx->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL))
        CALL_TXH(ieee80211_tx_h_rate_ctrl);

    if (unlikely(info->flags & IEEE80211_TX_INTFL_RETRANSMISSION)) {
        __skb_queue_tail(&tx->skbs, tx->skb);
        tx->skb = NULL;
        goto txh_done;
    }

    CALL_TXH(ieee80211_tx_h_michael_mic_add);
    CALL_TXH(ieee80211_tx_h_sequence);
    CALL_TXH(ieee80211_tx_h_fragment);
    /* handlers after fragment must be aware of tx info fragmentation! */
    CALL_TXH(ieee80211_tx_h_stats);
    CALL_TXH(ieee80211_tx_h_encrypt);
    if (!(tx->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL))
        CALL_TXH(ieee80211_tx_h_calculate_duration);
#undef CALL_TXH

 txh_done:
    if (unlikely(res == TX_DROP)) {
        I802_DEBUG_INC(tx->local->tx_handlers_drop);
        if (tx->skb)
            ieee80211_free_txskb(&tx->local->hw, tx->skb);
        else
            ieee80211_purge_tx_queue(&tx->local->hw, &tx->skbs);
        return -1;
    } else if (unlikely(res == TX_QUEUED)) {
        I802_DEBUG_INC(tx->local->tx_handlers_queued);
        return -1;
    }

    return 0;
}

/*
 * Returns false if the frame couldn't be transmitted but was queued instead.
 */
static bool ieee80211_tx(struct ieee80211_sub_if_data *sdata,
             struct sk_buff *skb, bool txpending)
{
    struct ieee80211_local *local = sdata->local;
    struct ieee80211_tx_data tx;
    ieee80211_tx_result res_prepare;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    bool result = true;
    int led_len;

    if (unlikely(skb->len < 10)) {
        dev_kfree_skb(skb);
        return true;
    }

    rcu_read_lock();

    /* initialises tx */
    led_len = skb->len;
    res_prepare = ieee80211_tx_prepare(sdata, &tx, skb);

    if (unlikely(res_prepare == TX_DROP)) {
        ieee80211_free_txskb(&local->hw, skb);
        goto out;
    } else if (unlikely(res_prepare == TX_QUEUED)) {
        goto out;
    }

    info->band = local->hw.conf.channel->band;

    /* set up hw_queue value early */
    if (!(info->flags & IEEE80211_TX_CTL_TX_OFFCHAN) ||
        !(local->hw.flags & IEEE80211_HW_QUEUE_CONTROL))
        info->hw_queue =
            sdata->vif.hw_queue[skb_get_queue_mapping(skb)];

    if (!invoke_tx_handlers(&tx))
        result = __ieee80211_tx(local, &tx.skbs, led_len,
                    tx.sta, txpending);
 out:
    rcu_read_unlock();
    return result;
}

/* device xmit handlers */

static int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
                struct sk_buff *skb,
                int head_need, bool may_encrypt)
{
    struct ieee80211_local *local = sdata->local;
    int tail_need = 0;

    if (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt) {
        tail_need = IEEE80211_ENCRYPT_TAILROOM;
        tail_need -= skb_tailroom(skb);
        tail_need = max_t(int, tail_need, 0);
    }

    if (skb_cloned(skb))
        I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
    else if (head_need || tail_need)
        I802_DEBUG_INC(local->tx_expand_skb_head);
    else
        return 0;

    if (pskb_expand_head(skb, head_need, tail_need, GFP_ATOMIC)) {
        wiphy_debug(local->hw.wiphy,
                "failed to reallocate TX buffer\n");
        return -ENOMEM;
    }

    return 0;
}

void ieee80211_xmit(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
{
    struct ieee80211_local *local = sdata->local;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
    int headroom;
    bool may_encrypt;

    rcu_read_lock();

    may_encrypt = !(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT);

    headroom = local->tx_headroom;
    if (may_encrypt)
        headroom += IEEE80211_ENCRYPT_HEADROOM;
    headroom -= skb_headroom(skb);
    headroom = max_t(int, 0, headroom);

    if (ieee80211_skb_resize(sdata, skb, headroom, may_encrypt)) {
        ieee80211_free_txskb(&local->hw, skb);
        rcu_read_unlock();
        return;
    }

    hdr = (struct ieee80211_hdr *) skb->data;
    info->control.vif = &sdata->vif;

    if (ieee80211_vif_is_mesh(&sdata->vif) &&
        ieee80211_is_data(hdr->frame_control) &&
        !is_multicast_ether_addr(hdr->addr1) &&
        mesh_nexthop_resolve(skb, sdata)) {
        /* skb queued: don't free */
        rcu_read_unlock();
        return;
    }

    ieee80211_set_qos_hdr(sdata, skb);
    ieee80211_tx(sdata, skb, false);
    rcu_read_unlock();
}

static bool ieee80211_parse_tx_radiotap(struct sk_buff *skb)
{
    struct ieee80211_radiotap_iterator iterator;
    struct ieee80211_radiotap_header *rthdr =
        (struct ieee80211_radiotap_header *) skb->data;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len,
                           NULL);
    u16 txflags;

    info->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT |
               IEEE80211_TX_CTL_DONTFRAG;

    /*
     * for every radiotap entry that is present
     * (ieee80211_radiotap_iterator_next returns -ENOENT when no more
     * entries present, or -EINVAL on error)
     */

    while (!ret) {
        ret = ieee80211_radiotap_iterator_next(&iterator);

        if (ret)
            continue;

        /* see if this argument is something we can use */
        switch (iterator.this_arg_index) {
        /*
         * You must take care when dereferencing iterator.this_arg
         * for multibyte types... the pointer is not aligned.  Use
         * get_unaligned((type *)iterator.this_arg) to dereference
         * iterator.this_arg for type "type" safely on all arches.
        */
        case IEEE80211_RADIOTAP_FLAGS:
            if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FCS) {
                /*
                 * this indicates that the skb we have been
                 * handed has the 32-bit FCS CRC at the end...
                 * we should react to that by snipping it off
                 * because it will be recomputed and added
                 * on transmission
                 */
                if (skb->len < (iterator._max_length + FCS_LEN))
                    return false;

                skb_trim(skb, skb->len - FCS_LEN);
            }
            if (*iterator.this_arg & IEEE80211_RADIOTAP_F_WEP)
                info->flags &= ~IEEE80211_TX_INTFL_DONT_ENCRYPT;
            if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FRAG)
                info->flags &= ~IEEE80211_TX_CTL_DONTFRAG;
            break;

        case IEEE80211_RADIOTAP_TX_FLAGS:
            txflags = get_unaligned_le16(iterator.this_arg);
            if (txflags & IEEE80211_RADIOTAP_F_TX_NOACK)
                info->flags |= IEEE80211_TX_CTL_NO_ACK;
            break;

        /*
         * Please update the file
         * Documentation/networking/mac80211-injection.txt
         * when parsing new fields here.
         */

        default:
            break;
        }
    }

    if (ret != -ENOENT) /* ie, if we didn't simply run out of fields */
        return false;

    /*
     * remove the radiotap header
     * iterator->_max_length was sanity-checked against
     * skb->len by iterator init
     */
    skb_pull(skb, iterator._max_length);

    return true;
}

netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb,
                     struct net_device *dev)
{
    struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
    struct ieee80211_channel *chan = local->hw.conf.channel;
    struct ieee80211_radiotap_header *prthdr =
        (struct ieee80211_radiotap_header *)skb->data;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr;
    struct ieee80211_sub_if_data *tmp_sdata, *sdata;
    u16 len_rthdr;
    int hdrlen;

    /*
     * Frame injection is not allowed if beaconing is not allowed
     * or if we need radar detection. Beaconing is usually not allowed when
     * the mode or operation (Adhoc, AP, Mesh) does not support DFS.
     * Passive scan is also used in world regulatory domains where
     * your country is not known and as such it should be treated as
     * NO TX unless the channel is explicitly allowed in which case
     * your current regulatory domain would not have the passive scan
     * flag.
     *
     * Since AP mode uses monitor interfaces to inject/TX management
     * frames we can make AP mode the exception to this rule once it
     * supports radar detection as its implementation can deal with
     * radar detection by itself. We can do that later by adding a
     * monitor flag interfaces used for AP support.
     */
    if ((chan->flags & (IEEE80211_CHAN_NO_IBSS | IEEE80211_CHAN_RADAR |
         IEEE80211_CHAN_PASSIVE_SCAN)))
        goto fail;

    /* check for not even having the fixed radiotap header part */
    if (unlikely(skb->len < sizeof(struct ieee80211_radiotap_header)))
        goto fail; /* too short to be possibly valid */

    /* is it a header version we can trust to find length from? */
    if (unlikely(prthdr->it_version))
        goto fail; /* only version 0 is supported */

    /* then there must be a radiotap header with a length we can use */
    len_rthdr = ieee80211_get_radiotap_len(skb->data);

    /* does the skb contain enough to deliver on the alleged length? */
    if (unlikely(skb->len < len_rthdr))
        goto fail; /* skb too short for claimed rt header extent */

    /*
     * fix up the pointers accounting for the radiotap
     * header still being in there.  We are being given
     * a precooked IEEE80211 header so no need for
     * normal processing
     */
    skb_set_mac_header(skb, len_rthdr);
    /*
     * these are just fixed to the end of the rt area since we
     * don't have any better information and at this point, nobody cares
     */
    skb_set_network_header(skb, len_rthdr);
    skb_set_transport_header(skb, len_rthdr);

    if (skb->len < len_rthdr + 2)
        goto fail;

    hdr = (struct ieee80211_hdr *)(skb->data + len_rthdr);
    hdrlen = ieee80211_hdrlen(hdr->frame_control);

    if (skb->len < len_rthdr + hdrlen)
        goto fail;

    /*
     * Initialize skb->protocol if the injected frame is a data frame
     * carrying a rfc1042 header
     */
    if (ieee80211_is_data(hdr->frame_control) &&
        skb->len >= len_rthdr + hdrlen + sizeof(rfc1042_header) + 2) {
        u8 *payload = (u8 *)hdr + hdrlen;

        if (ether_addr_equal(payload, rfc1042_header))
            skb->protocol = cpu_to_be16((payload[6] << 8) |
                            payload[7]);
    }

    memset(info, 0, sizeof(*info));

    info->flags = IEEE80211_TX_CTL_REQ_TX_STATUS |
              IEEE80211_TX_CTL_INJECTED;

    /* process and remove the injection radiotap header */
    if (!ieee80211_parse_tx_radiotap(skb))
        goto fail;

    rcu_read_lock();

    /*
     * We process outgoing injected frames that have a local address
     * we handle as though they are non-injected frames.
     * This code here isn't entirely correct, the local MAC address
     * isn't always enough to find the interface to use; for proper
     * VLAN/WDS support we will need a different mechanism (which
     * likely isn't going to be monitor interfaces).
     */
    sdata = IEEE80211_DEV_TO_SUB_IF(dev);

    list_for_each_entry_rcu(tmp_sdata, &local->interfaces, list) {
        if (!ieee80211_sdata_running(tmp_sdata))
            continue;
        if (tmp_sdata->vif.type == NL80211_IFTYPE_MONITOR ||
            tmp_sdata->vif.type == NL80211_IFTYPE_AP_VLAN ||
            tmp_sdata->vif.type == NL80211_IFTYPE_WDS)
            continue;
        if (ether_addr_equal(tmp_sdata->vif.addr, hdr->addr2)) {
            sdata = tmp_sdata;
            break;
        }
    }

    ieee80211_xmit(sdata, skb);
    rcu_read_unlock();

    return NETDEV_TX_OK;

fail:
    dev_kfree_skb(skb);
    return NETDEV_TX_OK; /* meaning, we dealt with the skb */
}

netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
                    struct net_device *dev)
{
    struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
    struct ieee80211_local *local = sdata->local;
    struct ieee80211_tx_info *info;
    int head_need;
    u16 ethertype, hdrlen,  meshhdrlen = 0;
    __le16 fc;
    struct ieee80211_hdr hdr;
    struct ieee80211s_hdr mesh_hdr __maybe_unused;
    struct mesh_path __maybe_unused *mppath = NULL, *mpath = NULL;
    const u8 *encaps_data;
    int encaps_len, skip_header_bytes;
    int nh_pos, h_pos;
    struct sta_info *sta = NULL;
    bool wme_sta = false, authorized = false, tdls_auth = false;
    bool tdls_direct = false;
    bool multicast;
    u32 info_flags = 0;
    u16 info_id = 0;

    if (unlikely(skb->len < ETH_HLEN))
        goto fail;

    /* convert Ethernet header to proper 802.11 header (based on
     * operation mode) */
    ethertype = (skb->data[12] << 8) | skb->data[13];
    fc = cpu_to_le16(IEEE80211_FTYPE_DATA | IEEE80211_STYPE_DATA);

    switch (sdata->vif.type) {
    case NL80211_IFTYPE_AP_VLAN:
        rcu_read_lock();
        sta = rcu_dereference(sdata->u.vlan.sta);
        if (sta) {
            fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
            /* RA TA DA SA */
            memcpy(hdr.addr1, sta->sta.addr, ETH_ALEN);
            memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
            memcpy(hdr.addr3, skb->data, ETH_ALEN);
            memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
            hdrlen = 30;
            authorized = test_sta_flag(sta, WLAN_STA_AUTHORIZED);
            wme_sta = test_sta_flag(sta, WLAN_STA_WME);
        }
        rcu_read_unlock();
        if (sta)
            break;
        /* fall through */
    case NL80211_IFTYPE_AP:
        fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS);
        /* DA BSSID SA */
        memcpy(hdr.addr1, skb->data, ETH_ALEN);
        memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
        memcpy(hdr.addr3, skb->data + ETH_ALEN, ETH_ALEN);
        hdrlen = 24;
        break;
    case NL80211_IFTYPE_WDS:
        fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
        /* RA TA DA SA */
        memcpy(hdr.addr1, sdata->u.wds.remote_addr, ETH_ALEN);
        memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
        memcpy(hdr.addr3, skb->data, ETH_ALEN);
        memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
        hdrlen = 30;
        break;
#ifdef CONFIG_MAC80211_MESH
    case NL80211_IFTYPE_MESH_POINT:
        if (!sdata->u.mesh.mshcfg.dot11MeshTTL) {
            /* Do not send frames with mesh_ttl == 0 */
            sdata->u.mesh.mshstats.dropped_frames_ttl++;
            goto fail;
        }
        rcu_read_lock();
        if (!is_multicast_ether_addr(skb->data)) {
            mpath = mesh_path_lookup(skb->data, sdata);
            if (!mpath)
                mppath = mpp_path_lookup(skb->data, sdata);
        }

        /*
         * Use address extension if it is a packet from
         * another interface or if we know the destination
         * is being proxied by a portal (i.e. portal address
         * differs from proxied address)
         */
        if (ether_addr_equal(sdata->vif.addr, skb->data + ETH_ALEN) &&
            !(mppath && !ether_addr_equal(mppath->mpp, skb->data))) {
            hdrlen = ieee80211_fill_mesh_addresses(&hdr, &fc,
                    skb->data, skb->data + ETH_ALEN);
            rcu_read_unlock();
            meshhdrlen = ieee80211_new_mesh_header(&mesh_hdr,
                    sdata, NULL, NULL);
        } else {
            /* DS -> MBSS (802.11-2012 13.11.3.3).
             * For unicast with unknown forwarding information,
             * destination might be in the MBSS or if that fails
             * forwarded to another mesh gate. In either case
             * resolution will be handled in ieee80211_xmit(), so
             * leave the original DA. This also works for mcast */
            const u8 *mesh_da = skb->data;

            if (mppath)
                mesh_da = mppath->mpp;
            else if (mpath)
                mesh_da = mpath->dst;
            rcu_read_unlock();

            hdrlen = ieee80211_fill_mesh_addresses(&hdr, &fc,
                    mesh_da, sdata->vif.addr);
            if (is_multicast_ether_addr(mesh_da))
                /* DA TA mSA AE:SA */
                meshhdrlen =
                    ieee80211_new_mesh_header(&mesh_hdr,
                            sdata,
                            skb->data + ETH_ALEN,
                            NULL);
            else
                /* RA TA mDA mSA AE:DA SA */
                meshhdrlen =
                    ieee80211_new_mesh_header(&mesh_hdr,
                            sdata,
                            skb->data,
                            skb->data + ETH_ALEN);

        }
        break;
#endif
    case NL80211_IFTYPE_STATION:
        if (sdata->wdev.wiphy->flags & WIPHY_FLAG_SUPPORTS_TDLS) {
            bool tdls_peer = false;

            rcu_read_lock();
            sta = sta_info_get(sdata, skb->data);
            if (sta) {
                authorized = test_sta_flag(sta,
                            WLAN_STA_AUTHORIZED);
                wme_sta = test_sta_flag(sta, WLAN_STA_WME);
                tdls_peer = test_sta_flag(sta,
                             WLAN_STA_TDLS_PEER);
                tdls_auth = test_sta_flag(sta,
                        WLAN_STA_TDLS_PEER_AUTH);
            }
            rcu_read_unlock();

            /*
             * If the TDLS link is enabled, send everything
             * directly. Otherwise, allow TDLS setup frames
             * to be transmitted indirectly.
             */
            tdls_direct = tdls_peer && (tdls_auth ||
                 !(ethertype == ETH_P_TDLS && skb->len > 14 &&
                   skb->data[14] == WLAN_TDLS_SNAP_RFTYPE));
        }

        if (tdls_direct) {
            /* link during setup - throw out frames to peer */
            if (!tdls_auth)
                goto fail;

            /* DA SA BSSID */
            memcpy(hdr.addr1, skb->data, ETH_ALEN);
            memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
            memcpy(hdr.addr3, sdata->u.mgd.bssid, ETH_ALEN);
            hdrlen = 24;
        }  else if (sdata->u.mgd.use_4addr &&
                cpu_to_be16(ethertype) != sdata->control_port_protocol) {
            fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS |
                      IEEE80211_FCTL_TODS);
            /* RA TA DA SA */
            memcpy(hdr.addr1, sdata->u.mgd.bssid, ETH_ALEN);
            memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
            memcpy(hdr.addr3, skb->data, ETH_ALEN);
            memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
            hdrlen = 30;
        } else {
            fc |= cpu_to_le16(IEEE80211_FCTL_TODS);
            /* BSSID SA DA */
            memcpy(hdr.addr1, sdata->u.mgd.bssid, ETH_ALEN);
            memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
            memcpy(hdr.addr3, skb->data, ETH_ALEN);
            hdrlen = 24;
        }
        break;
    case NL80211_IFTYPE_ADHOC:
        /* DA SA BSSID */
        memcpy(hdr.addr1, skb->data, ETH_ALEN);
        memcpy(hdr.addr2, skb->data + ETH_ALEN, ETH_ALEN);
        memcpy(hdr.addr3, sdata->u.ibss.bssid, ETH_ALEN);
        hdrlen = 24;
        break;
    default:
        goto fail;
    }

    /*
     * There's no need to try to look up the destination
     * if it is a multicast address (which can only happen
     * in AP mode)
     */
    multicast = is_multicast_ether_addr(hdr.addr1);
    if (!multicast) {
        rcu_read_lock();
        sta = sta_info_get(sdata, hdr.addr1);
        if (sta) {
            authorized = test_sta_flag(sta, WLAN_STA_AUTHORIZED);
            wme_sta = test_sta_flag(sta, WLAN_STA_WME);
        }
        rcu_read_unlock();
    }

    /* For mesh, the use of the QoS header is mandatory */
    if (ieee80211_vif_is_mesh(&sdata->vif))
        wme_sta = true;

    /* receiver and we are QoS enabled, use a QoS type frame */
    if (wme_sta && local->hw.queues >= IEEE80211_NUM_ACS) {
        fc |= cpu_to_le16(IEEE80211_STYPE_QOS_DATA);
        hdrlen += 2;
    }

    /*
     * Drop unicast frames to unauthorised stations unless they are
     * EAPOL frames from the local station.
     */
    if (unlikely(!ieee80211_vif_is_mesh(&sdata->vif) &&
             !is_multicast_ether_addr(hdr.addr1) && !authorized &&
             (cpu_to_be16(ethertype) != sdata->control_port_protocol ||
              !ether_addr_equal(sdata->vif.addr, skb->data + ETH_ALEN)))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        net_info_ratelimited("%s: dropped frame to %pM (unauthorized port)\n",
                    dev->name, hdr.addr1);
#endif

        I802_DEBUG_INC(local->tx_handlers_drop_unauth_port);

        goto fail;
    }

    if (unlikely(!multicast && skb->sk &&
             skb_shinfo(skb)->tx_flags & SKBTX_WIFI_STATUS)) {
        struct sk_buff *orig_skb = skb;

        skb = skb_clone(skb, GFP_ATOMIC);
        if (skb) {
            unsigned long flags;
            int id, r;

            spin_lock_irqsave(&local->ack_status_lock, flags);
            r = idr_get_new_above(&local->ack_status_frames,
                          orig_skb, 1, &id);
            if (r == -EAGAIN) {
                idr_pre_get(&local->ack_status_frames,
                        GFP_ATOMIC);
                r = idr_get_new_above(&local->ack_status_frames,
                              orig_skb, 1, &id);
            }
            if (WARN_ON(!id) || id > 0xffff) {
                idr_remove(&local->ack_status_frames, id);
                r = -ERANGE;
            }
            spin_unlock_irqrestore(&local->ack_status_lock, flags);

            if (!r) {
                info_id = id;
                info_flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;
            } else if (skb_shared(skb)) {
                kfree_skb(orig_skb);
            } else {
                kfree_skb(skb);
                skb = orig_skb;
            }
        } else {
            /* couldn't clone -- lose tx status ... */
            skb = orig_skb;
        }
    }

    /*
     * If the skb is shared we need to obtain our own copy.
     */
    if (skb_shared(skb)) {
        struct sk_buff *tmp_skb = skb;

        /* can't happen -- skb is a clone if info_id != 0 */
        WARN_ON(info_id);

        skb = skb_clone(skb, GFP_ATOMIC);
        kfree_skb(tmp_skb);

        if (!skb)
            goto fail;
    }

    hdr.frame_control = fc;
    hdr.duration_id = 0;
    hdr.seq_ctrl = 0;

    skip_header_bytes = ETH_HLEN;
    if (ethertype == ETH_P_AARP || ethertype == ETH_P_IPX) {
        encaps_data = bridge_tunnel_header;
        encaps_len = sizeof(bridge_tunnel_header);
        skip_header_bytes -= 2;
    } else if (ethertype >= 0x600) {
        encaps_data = rfc1042_header;
        encaps_len = sizeof(rfc1042_header);
        skip_header_bytes -= 2;
    } else {
        encaps_data = NULL;
        encaps_len = 0;
    }

    nh_pos = skb_network_header(skb) - skb->data;
    h_pos = skb_transport_header(skb) - skb->data;

    skb_pull(skb, skip_header_bytes);
    nh_pos -= skip_header_bytes;
    h_pos -= skip_header_bytes;

    head_need = hdrlen + encaps_len + meshhdrlen - skb_headroom(skb);

    /*
     * So we need to modify the skb header and hence need a copy of
     * that. The head_need variable above doesn't, so far, include
     * the needed header space that we don't need right away. If we
     * can, then we don't reallocate right now but only after the
     * frame arrives at the master device (if it does...)
     *
     * If we cannot, however, then we will reallocate to include all
     * the ever needed space. Also, if we need to reallocate it anyway,
     * make it big enough for everything we may ever need.
     */

    if (head_need > 0 || skb_cloned(skb)) {
        head_need += IEEE80211_ENCRYPT_HEADROOM;
        head_need += local->tx_headroom;
        head_need = max_t(int, 0, head_need);
        if (ieee80211_skb_resize(sdata, skb, head_need, true)) {
            ieee80211_free_txskb(&local->hw, skb);
            return NETDEV_TX_OK;
        }
    }

    if (encaps_data) {
        memcpy(skb_push(skb, encaps_len), encaps_data, encaps_len);
        nh_pos += encaps_len;
        h_pos += encaps_len;
    }

#ifdef CONFIG_MAC80211_MESH
    if (meshhdrlen > 0) {
        memcpy(skb_push(skb, meshhdrlen), &mesh_hdr, meshhdrlen);
        nh_pos += meshhdrlen;
        h_pos += meshhdrlen;
    }
#endif

    if (ieee80211_is_data_qos(fc)) {
        __le16 *qos_control;

        qos_control = (__le16*) skb_push(skb, 2);
        memcpy(skb_push(skb, hdrlen - 2), &hdr, hdrlen - 2);
        /*
         * Maybe we could actually set some fields here, for now just
         * initialise to zero to indicate no special operation.
         */
        *qos_control = 0;
    } else
        memcpy(skb_push(skb, hdrlen), &hdr, hdrlen);

    nh_pos += hdrlen;
    h_pos += hdrlen;

    dev->stats.tx_packets++;
    dev->stats.tx_bytes += skb->len;

    /* Update skb pointers to various headers since this modified frame
     * is going to go through Linux networking code that may potentially
     * need things like pointer to IP header. */
    skb_set_mac_header(skb, 0);
    skb_set_network_header(skb, nh_pos);
    skb_set_transport_header(skb, h_pos);

    info = IEEE80211_SKB_CB(skb);
    memset(info, 0, sizeof(*info));

    dev->trans_start = jiffies;

    info->flags = info_flags;
    info->ack_frame_id = info_id;

    ieee80211_xmit(sdata, skb);

    return NETDEV_TX_OK;

 fail:
    dev_kfree_skb(skb);
    return NETDEV_TX_OK;
}


/*
 * ieee80211_clear_tx_pending may not be called in a context where
 * it is possible that it packets could come in again.
 */
void ieee80211_clear_tx_pending(struct ieee80211_local *local)
{
    struct sk_buff *skb;
    int i;

    for (i = 0; i < local->hw.queues; i++) {
        while ((skb = skb_dequeue(&local->pending[i])) != NULL)
            ieee80211_free_txskb(&local->hw, skb);
    }
}

/*
 * Returns false if the frame couldn't be transmitted but was queued instead,
 * which in this case means re-queued -- take as an indication to stop sending
 * more pending frames.
 */
static bool ieee80211_tx_pending_skb(struct ieee80211_local *local,
                     struct sk_buff *skb)
{
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    struct ieee80211_sub_if_data *sdata;
    struct sta_info *sta;
    struct ieee80211_hdr *hdr;
    bool result;

    sdata = vif_to_sdata(info->control.vif);

    if (info->flags & IEEE80211_TX_INTFL_NEED_TXPROCESSING) {
        result = ieee80211_tx(sdata, skb, true);
    } else {
        struct sk_buff_head skbs;

        __skb_queue_head_init(&skbs);
        __skb_queue_tail(&skbs, skb);

        hdr = (struct ieee80211_hdr *)skb->data;
        sta = sta_info_get(sdata, hdr->addr1);

        result = __ieee80211_tx(local, &skbs, skb->len, sta, true);
    }

    return result;
}

/*
 * Transmit all pending packets. Called from tasklet.
 */
void ieee80211_tx_pending(unsigned long data)
{
    struct ieee80211_local *local = (struct ieee80211_local *)data;
    unsigned long flags;
    int i;
    bool txok;

    rcu_read_lock();

    spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
    for (i = 0; i < local->hw.queues; i++) {
        /*
         * If queue is stopped by something other than due to pending
         * frames, or we have no pending frames, proceed to next queue.
         */
        if (local->queue_stop_reasons[i] ||
            skb_queue_empty(&local->pending[i]))
            continue;

        while (!skb_queue_empty(&local->pending[i])) {
            struct sk_buff *skb = __skb_dequeue(&local->pending[i]);
            struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

            if (WARN_ON(!info->control.vif)) {
                ieee80211_free_txskb(&local->hw, skb);
                continue;
            }

            spin_unlock_irqrestore(&local->queue_stop_reason_lock,
                        flags);

            txok = ieee80211_tx_pending_skb(local, skb);
            spin_lock_irqsave(&local->queue_stop_reason_lock,
                      flags);
            if (!txok)
                break;
        }

        if (skb_queue_empty(&local->pending[i]))
            ieee80211_propagate_queue_wake(local, i);
    }
    spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);

    rcu_read_unlock();
}

/* functions for drivers to get certain frames */

static void ieee80211_beacon_add_tim(struct ieee80211_sub_if_data *sdata,
                     struct ieee80211_if_ap *bss,
                     struct sk_buff *skb,
                     struct beacon_data *beacon)
{
    u8 *pos, *tim;
    int aid0 = 0;
    int i, have_bits = 0, n1, n2;

    /* Generate bitmap for TIM only if there are any STAs in power save
     * mode. */
    if (atomic_read(&bss->num_sta_ps) > 0)
        /* in the hope that this is faster than
         * checking byte-for-byte */
        have_bits = !bitmap_empty((unsigned long*)bss->tim,
                      IEEE80211_MAX_AID+1);

    if (bss->dtim_count == 0)
        bss->dtim_count = sdata->vif.bss_conf.dtim_period - 1;
    else
        bss->dtim_count--;

    tim = pos = (u8 *) skb_put(skb, 6);
    *pos++ = WLAN_EID_TIM;
    *pos++ = 4;
    *pos++ = bss->dtim_count;
    *pos++ = sdata->vif.bss_conf.dtim_period;

    if (bss->dtim_count == 0 && !skb_queue_empty(&bss->ps_bc_buf))
        aid0 = 1;

    bss->dtim_bc_mc = aid0 == 1;

    if (have_bits) {
        /* Find largest even number N1 so that bits numbered 1 through
         * (N1 x 8) - 1 in the bitmap are 0 and number N2 so that bits
         * (N2 + 1) x 8 through 2007 are 0. */
        n1 = 0;
        for (i = 0; i < IEEE80211_MAX_TIM_LEN; i++) {
            if (bss->tim[i]) {
                n1 = i & 0xfe;
                break;
            }
        }
        n2 = n1;
        for (i = IEEE80211_MAX_TIM_LEN - 1; i >= n1; i--) {
            if (bss->tim[i]) {
                n2 = i;
                break;
            }
        }

        /* Bitmap control */
        *pos++ = n1 | aid0;
        /* Part Virt Bitmap */
        skb_put(skb, n2 - n1);
        memcpy(pos, bss->tim + n1, n2 - n1 + 1);

        tim[1] = n2 - n1 + 4;
    } else {
        *pos++ = aid0; /* Bitmap control */
        *pos++ = 0; /* Part Virt Bitmap */
    }
}

struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
                     struct ieee80211_vif *vif,
                     u16 *tim_offset, u16 *tim_length)
{
    struct ieee80211_local *local = hw_to_local(hw);
    struct sk_buff *skb = NULL;
    struct ieee80211_tx_info *info;
    struct ieee80211_sub_if_data *sdata = NULL;
    struct ieee80211_if_ap *ap = NULL;
    struct beacon_data *beacon;
    enum ieee80211_band band = local->oper_channel->band;
    struct ieee80211_tx_rate_control txrc;

    rcu_read_lock();

    sdata = vif_to_sdata(vif);

    if (!ieee80211_sdata_running(sdata))
        goto out;

    if (tim_offset)
        *tim_offset = 0;
    if (tim_length)
        *tim_length = 0;

    if (sdata->vif.type == NL80211_IFTYPE_AP) {
        ap = &sdata->u.ap;
        beacon = rcu_dereference(ap->beacon);
        if (beacon) {
            /*
             * headroom, head length,
             * tail length and maximum TIM length
             */
            skb = dev_alloc_skb(local->tx_headroom +
                        beacon->head_len +
                        beacon->tail_len + 256);
            if (!skb)
                goto out;

            skb_reserve(skb, local->tx_headroom);
            memcpy(skb_put(skb, beacon->head_len), beacon->head,
                   beacon->head_len);

            /*
             * Not very nice, but we want to allow the driver to call
             * ieee80211_beacon_get() as a response to the set_tim()
             * callback. That, however, is already invoked under the
             * sta_lock to guarantee consistent and race-free update
             * of the tim bitmap in mac80211 and the driver.
             */
            if (local->tim_in_locked_section) {
                ieee80211_beacon_add_tim(sdata, ap, skb,
                             beacon);
            } else {
                unsigned long flags;

                spin_lock_irqsave(&local->tim_lock, flags);
                ieee80211_beacon_add_tim(sdata, ap, skb,
                             beacon);
                spin_unlock_irqrestore(&local->tim_lock, flags);
            }

            if (tim_offset)
                *tim_offset = beacon->head_len;
            if (tim_length)
                *tim_length = skb->len - beacon->head_len;

            if (beacon->tail)
                memcpy(skb_put(skb, beacon->tail_len),
                       beacon->tail, beacon->tail_len);
        } else
            goto out;
    } else if (sdata->vif.type == NL80211_IFTYPE_ADHOC) {
        struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
        struct ieee80211_hdr *hdr;
        struct sk_buff *presp = rcu_dereference(ifibss->presp);

        if (!presp)
            goto out;

        skb = skb_copy(presp, GFP_ATOMIC);
        if (!skb)
            goto out;

        hdr = (struct ieee80211_hdr *) skb->data;
        hdr->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                         IEEE80211_STYPE_BEACON);
    } else if (ieee80211_vif_is_mesh(&sdata->vif)) {
        struct ieee80211_mgmt *mgmt;
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        u8 *pos;
        int hdr_len = offsetof(struct ieee80211_mgmt, u.beacon) +
                  sizeof(mgmt->u.beacon);

#ifdef CONFIG_MAC80211_MESH
        if (!sdata->u.mesh.mesh_id_len)
            goto out;
#endif

        if (ifmsh->sync_ops)
            ifmsh->sync_ops->adjust_tbtt(
                        sdata);

        skb = dev_alloc_skb(local->tx_headroom +
                    hdr_len +
                    2 + /* NULL SSID */
                    2 + 8 + /* supported rates */
                    2 + 3 + /* DS params */
                    2 + (IEEE80211_MAX_SUPP_RATES - 8) +
                    2 + sizeof(struct ieee80211_ht_cap) +
                    2 + sizeof(struct ieee80211_ht_operation) +
                    2 + sdata->u.mesh.mesh_id_len +
                    2 + sizeof(struct ieee80211_meshconf_ie) +
                    sdata->u.mesh.ie_len);
        if (!skb)
            goto out;

        skb_reserve(skb, local->hw.extra_tx_headroom);
        mgmt = (struct ieee80211_mgmt *) skb_put(skb, hdr_len);
        memset(mgmt, 0, hdr_len);
        mgmt->frame_control =
            cpu_to_le16(IEEE80211_FTYPE_MGMT | IEEE80211_STYPE_BEACON);
        eth_broadcast_addr(mgmt->da);
        memcpy(mgmt->sa, sdata->vif.addr, ETH_ALEN);
        memcpy(mgmt->bssid, sdata->vif.addr, ETH_ALEN);
        mgmt->u.beacon.beacon_int =
            cpu_to_le16(sdata->vif.bss_conf.beacon_int);
        mgmt->u.beacon.capab_info |= cpu_to_le16(
            sdata->u.mesh.security ? WLAN_CAPABILITY_PRIVACY : 0);

        pos = skb_put(skb, 2);
        *pos++ = WLAN_EID_SSID;
        *pos++ = 0x0;

        if (ieee80211_add_srates_ie(sdata, skb, true, band) ||
            mesh_add_ds_params_ie(skb, sdata) ||
            ieee80211_add_ext_srates_ie(sdata, skb, true, band) ||
            mesh_add_rsn_ie(skb, sdata) ||
            mesh_add_ht_cap_ie(skb, sdata) ||
            mesh_add_ht_oper_ie(skb, sdata) ||
            mesh_add_meshid_ie(skb, sdata) ||
            mesh_add_meshconf_ie(skb, sdata) ||
            mesh_add_vendor_ies(skb, sdata)) {
            pr_err("o11s: couldn't add ies!\n");
            goto out;
        }
    } else {
        WARN_ON(1);
        goto out;
    }

    info = IEEE80211_SKB_CB(skb);

    info->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
    info->flags |= IEEE80211_TX_CTL_NO_ACK;
    info->band = band;

    memset(&txrc, 0, sizeof(txrc));
    txrc.hw = hw;
    txrc.sband = local->hw.wiphy->bands[band];
    txrc.bss_conf = &sdata->vif.bss_conf;
    txrc.skb = skb;
    txrc.reported_rate.idx = -1;
    txrc.rate_idx_mask = sdata->rc_rateidx_mask[band];
    if (txrc.rate_idx_mask == (1 << txrc.sband->n_bitrates) - 1)
        txrc.max_rate_idx = -1;
    else
        txrc.max_rate_idx = fls(txrc.rate_idx_mask) - 1;
    memcpy(txrc.rate_idx_mcs_mask, sdata->rc_rateidx_mcs_mask[band],
           sizeof(txrc.rate_idx_mcs_mask));
    txrc.bss = true;
    rate_control_get_rate(sdata, NULL, &txrc);

    info->control.vif = vif;

    info->flags |= IEEE80211_TX_CTL_CLEAR_PS_FILT |
            IEEE80211_TX_CTL_ASSIGN_SEQ |
            IEEE80211_TX_CTL_FIRST_FRAGMENT;
 out:
    rcu_read_unlock();
    return skb;
}
EXPORT_SYMBOL(ieee80211_beacon_get_tim);

struct sk_buff *ieee80211_proberesp_get(struct ieee80211_hw *hw,
                    struct ieee80211_vif *vif)
{
    struct ieee80211_if_ap *ap = NULL;
    struct sk_buff *skb = NULL;
    struct probe_resp *presp = NULL;
    struct ieee80211_hdr *hdr;
    struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);

    if (sdata->vif.type != NL80211_IFTYPE_AP)
        return NULL;

    rcu_read_lock();

    ap = &sdata->u.ap;
    presp = rcu_dereference(ap->probe_resp);
    if (!presp)
        goto out;

    skb = dev_alloc_skb(presp->len);
    if (!skb)
        goto out;

    memcpy(skb_put(skb, presp->len), presp->data, presp->len);

    hdr = (struct ieee80211_hdr *) skb->data;
    memset(hdr->addr1, 0, sizeof(hdr->addr1));

out:
    rcu_read_unlock();
    return skb;
}
EXPORT_SYMBOL(ieee80211_proberesp_get);

struct sk_buff *ieee80211_pspoll_get(struct ieee80211_hw *hw,
                     struct ieee80211_vif *vif)
{
    struct ieee80211_sub_if_data *sdata;
    struct ieee80211_if_managed *ifmgd;
    struct ieee80211_pspoll *pspoll;
    struct ieee80211_local *local;
    struct sk_buff *skb;

    if (WARN_ON(vif->type != NL80211_IFTYPE_STATION))
        return NULL;

    sdata = vif_to_sdata(vif);
    ifmgd = &sdata->u.mgd;
    local = sdata->local;

    skb = dev_alloc_skb(local->hw.extra_tx_headroom + sizeof(*pspoll));
    if (!skb)
        return NULL;

    skb_reserve(skb, local->hw.extra_tx_headroom);

    pspoll = (struct ieee80211_pspoll *) skb_put(skb, sizeof(*pspoll));
    memset(pspoll, 0, sizeof(*pspoll));
    pspoll->frame_control = cpu_to_le16(IEEE80211_FTYPE_CTL |
                        IEEE80211_STYPE_PSPOLL);
    pspoll->aid = cpu_to_le16(ifmgd->aid);

    /* aid in PS-Poll has its two MSBs each set to 1 */
    pspoll->aid |= cpu_to_le16(1 << 15 | 1 << 14);

    memcpy(pspoll->bssid, ifmgd->bssid, ETH_ALEN);
    memcpy(pspoll->ta, vif->addr, ETH_ALEN);

    return skb;
}
EXPORT_SYMBOL(ieee80211_pspoll_get);

struct sk_buff *ieee80211_nullfunc_get(struct ieee80211_hw *hw,
                       struct ieee80211_vif *vif)
{
    struct ieee80211_hdr_3addr *nullfunc;
    struct ieee80211_sub_if_data *sdata;
    struct ieee80211_if_managed *ifmgd;
    struct ieee80211_local *local;
    struct sk_buff *skb;

    if (WARN_ON(vif->type != NL80211_IFTYPE_STATION))
        return NULL;

    sdata = vif_to_sdata(vif);
    ifmgd = &sdata->u.mgd;
    local = sdata->local;

    skb = dev_alloc_skb(local->hw.extra_tx_headroom + sizeof(*nullfunc));
    if (!skb)
        return NULL;

    skb_reserve(skb, local->hw.extra_tx_headroom);

    nullfunc = (struct ieee80211_hdr_3addr *) skb_put(skb,
                              sizeof(*nullfunc));
    memset(nullfunc, 0, sizeof(*nullfunc));
    nullfunc->frame_control = cpu_to_le16(IEEE80211_FTYPE_DATA |
                          IEEE80211_STYPE_NULLFUNC |
                          IEEE80211_FCTL_TODS);
    memcpy(nullfunc->addr1, ifmgd->bssid, ETH_ALEN);
    memcpy(nullfunc->addr2, vif->addr, ETH_ALEN);
    memcpy(nullfunc->addr3, ifmgd->bssid, ETH_ALEN);

    return skb;
}
EXPORT_SYMBOL(ieee80211_nullfunc_get);

struct sk_buff *ieee80211_probereq_get(struct ieee80211_hw *hw,
                       struct ieee80211_vif *vif,
                       const u8 *ssid, size_t ssid_len,
                       const u8 *ie, size_t ie_len)
{
    struct ieee80211_sub_if_data *sdata;
    struct ieee80211_local *local;
    struct ieee80211_hdr_3addr *hdr;
    struct sk_buff *skb;
    size_t ie_ssid_len;
    u8 *pos;

    sdata = vif_to_sdata(vif);
    local = sdata->local;
    ie_ssid_len = 2 + ssid_len;

    skb = dev_alloc_skb(local->hw.extra_tx_headroom + sizeof(*hdr) +
                ie_ssid_len + ie_len);
    if (!skb)
        return NULL;

    skb_reserve(skb, local->hw.extra_tx_headroom);

    hdr = (struct ieee80211_hdr_3addr *) skb_put(skb, sizeof(*hdr));
    memset(hdr, 0, sizeof(*hdr));
    hdr->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                     IEEE80211_STYPE_PROBE_REQ);
    eth_broadcast_addr(hdr->addr1);
    memcpy(hdr->addr2, vif->addr, ETH_ALEN);
    eth_broadcast_addr(hdr->addr3);

    pos = skb_put(skb, ie_ssid_len);
    *pos++ = WLAN_EID_SSID;
    *pos++ = ssid_len;
    if (ssid_len)
        memcpy(pos, ssid, ssid_len);
    pos += ssid_len;

    if (ie) {
        pos = skb_put(skb, ie_len);
        memcpy(pos, ie, ie_len);
    }

    return skb;
}
EXPORT_SYMBOL(ieee80211_probereq_get);

void ieee80211_rts_get(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
               const void *frame, size_t frame_len,
               const struct ieee80211_tx_info *frame_txctl,
               struct ieee80211_rts *rts)
{
    const struct ieee80211_hdr *hdr = frame;

    rts->frame_control =
        cpu_to_le16(IEEE80211_FTYPE_CTL | IEEE80211_STYPE_RTS);
    rts->duration = ieee80211_rts_duration(hw, vif, frame_len,
                           frame_txctl);
    memcpy(rts->ra, hdr->addr1, sizeof(rts->ra));
    memcpy(rts->ta, hdr->addr2, sizeof(rts->ta));
}
EXPORT_SYMBOL(ieee80211_rts_get);

void ieee80211_ctstoself_get(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
                 const void *frame, size_t frame_len,
                 const struct ieee80211_tx_info *frame_txctl,
                 struct ieee80211_cts *cts)
{
    const struct ieee80211_hdr *hdr = frame;

    cts->frame_control =
        cpu_to_le16(IEEE80211_FTYPE_CTL | IEEE80211_STYPE_CTS);
    cts->duration = ieee80211_ctstoself_duration(hw, vif,
                             frame_len, frame_txctl);
    memcpy(cts->ra, hdr->addr1, sizeof(cts->ra));
}
EXPORT_SYMBOL(ieee80211_ctstoself_get);

struct sk_buff *
ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
              struct ieee80211_vif *vif)
{
    struct ieee80211_local *local = hw_to_local(hw);
    struct sk_buff *skb = NULL;
    struct ieee80211_tx_data tx;
    struct ieee80211_sub_if_data *sdata;
    struct ieee80211_if_ap *bss = NULL;
    struct beacon_data *beacon;
    struct ieee80211_tx_info *info;

    sdata = vif_to_sdata(vif);
    bss = &sdata->u.ap;

    rcu_read_lock();
    beacon = rcu_dereference(bss->beacon);

    if (sdata->vif.type != NL80211_IFTYPE_AP || !beacon || !beacon->head)
        goto out;

    if (bss->dtim_count != 0 || !bss->dtim_bc_mc)
        goto out; /* send buffered bc/mc only after DTIM beacon */

    while (1) {
        skb = skb_dequeue(&bss->ps_bc_buf);
        if (!skb)
            goto out;
        local->total_ps_buffered--;

        if (!skb_queue_empty(&bss->ps_bc_buf) && skb->len >= 2) {
            struct ieee80211_hdr *hdr =
                (struct ieee80211_hdr *) skb->data;
            /* more buffered multicast/broadcast frames ==> set
             * MoreData flag in IEEE 802.11 header to inform PS
             * STAs */
            hdr->frame_control |=
                cpu_to_le16(IEEE80211_FCTL_MOREDATA);
        }

        if (!ieee80211_tx_prepare(sdata, &tx, skb))
            break;
        dev_kfree_skb_any(skb);
    }

    info = IEEE80211_SKB_CB(skb);

    tx.flags |= IEEE80211_TX_PS_BUFFERED;
    info->band = local->oper_channel->band;

    if (invoke_tx_handlers(&tx))
        skb = NULL;
 out:
    rcu_read_unlock();

    return skb;
}
EXPORT_SYMBOL(ieee80211_get_buffered_bc);

void ieee80211_tx_skb_tid(struct ieee80211_sub_if_data *sdata,
              struct sk_buff *skb, int tid)
{
    int ac = ieee802_1d_to_ac[tid & 7];

    skb_set_mac_header(skb, 0);
    skb_set_network_header(skb, 0);
    skb_set_transport_header(skb, 0);

    skb_set_queue_mapping(skb, ac);
    skb->priority = tid;

    /*
     * The other path calling ieee80211_xmit is from the tasklet,
     * and while we can handle concurrent transmissions locking
     * requirements are that we do not come into tx with bhs on.
     */
    local_bh_disable();
    ieee80211_xmit(sdata, skb);
    local_bh_enable();
}