mac80211/drivers: rewrite the rate control API

[safe/jmp/linux-2.6] / net / mac80211 / tx.c

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
 * Copyright 2007       Johannes Berg <johannes@sipsolutions.net>
 *
 * 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 <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 "led.h"
#include "mesh.h"
#include "wep.h"
#include "wpa.h"
#include "wme.h"
#include "rate.h"

#define IEEE80211_TX_OK         0
#define IEEE80211_TX_AGAIN      1
#define IEEE80211_TX_FRAG_AGAIN 2

/* misc utils */

static __le16 ieee80211_duration(struct ieee80211_tx_data *tx, 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(tx->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[tx->channel->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 *)tx->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_NUM_BANDS:
                        WARN_ON(1);
                        break;
                }
        }
        if (rate == -1) {
                /* No matching basic rate found; use highest suitable mandatory
                 * PHY rate */
                rate = mrate;
        }

        /* Time needed to transmit ACK
         * (10 bytes + 4-byte FCS = 112 bits) plus SIFS; rounded up
         * to closest integer */

        dur = ieee80211_frame_duration(local, 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(local, next_frag_len,
                                txrate->bitrate, erp,
                                tx->sdata->vif.bss_conf.use_short_preamble);
        }

        return cpu_to_le16(dur);
}

static int inline is_ieee80211_device(struct ieee80211_local *local,
                                      struct net_device *dev)
{
        return local == wdev_priv(dev->ieee80211_ptr);
}

/* tx handlers */

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);
        u32 sta_flags;

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

        if (unlikely(tx->local->sw_scanning) &&
            !ieee80211_is_probe_req(hdr->frame_control))
                return TX_DROP;

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

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

        sta_flags = tx->sta ? get_sta_flags(tx->sta) : 0;

        if (likely(tx->flags & IEEE80211_TX_UNICAST)) {
                if (unlikely(!(sta_flags & WLAN_STA_ASSOC) &&
                             tx->sdata->vif.type != NL80211_IFTYPE_ADHOC &&
                             ieee80211_is_data(hdr->frame_control))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                        printk(KERN_DEBUG "%s: dropped data frame to not "
                               "associated station %pM\n",
                               tx->dev->name, hdr->addr1);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
                        I802_DEBUG_INC(tx->local->tx_handlers_drop_not_assoc);
                        return TX_DROP;
                }
        } else {
                if (unlikely(ieee80211_is_data(hdr->frame_control) &&
                             tx->local->num_sta == 0 &&
                             tx->sdata->vif.type != NL80211_IFTYPE_ADHOC)) {
                        /*
                         * No associated STAs - no need to send multicast
                         * frames.
                         */
                        return TX_DROP;
                }
                return TX_CONTINUE;
        }

        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);
        }

        list_for_each_entry_rcu(sta, &local->sta_list, list) {
                skb = skb_dequeue(&sta->ps_tx_buf);
                if (skb) {
                        purged++;
                        dev_kfree_skb(skb);
                }
                total += skb_queue_len(&sta->ps_tx_buf);
        }

        rcu_read_unlock();

        local->total_ps_buffered = total;
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        printk(KERN_DEBUG "%s: PS buffers full - purged %d frames\n",
               wiphy_name(local->hw.wiphy), purged);
#endif
}

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;

        /* buffered in mac80211 */
        if (tx->local->hw.flags & IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING) {
                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) {
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                        if (net_ratelimit()) {
                                printk(KERN_DEBUG "%s: BC TX buffer full - "
                                       "dropping the oldest frame\n",
                                       tx->dev->name);
                        }
#endif
                        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;
        }

        /* buffered in hardware */
        info->flags |= IEEE80211_TX_CTL_SEND_AFTER_DTIM;

        return TX_CONTINUE;
}

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;
        u32 staflags;

        if (unlikely(!sta || ieee80211_is_probe_resp(hdr->frame_control)))
                return TX_CONTINUE;

        staflags = get_sta_flags(sta);

        if (unlikely((staflags & WLAN_STA_PS) &&
                     !(staflags & WLAN_STA_PSPOLL))) {
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                printk(KERN_DEBUG "STA %pM aid %d: PS buffer (entries "
                       "before %d)\n",
                       sta->sta.addr, sta->sta.aid,
                       skb_queue_len(&sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
                if (tx->local->total_ps_buffered >= TOTAL_MAX_TX_BUFFER)
                        purge_old_ps_buffers(tx->local);
                if (skb_queue_len(&sta->ps_tx_buf) >= STA_MAX_TX_BUFFER) {
                        struct sk_buff *old = skb_dequeue(&sta->ps_tx_buf);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                        if (net_ratelimit()) {
                                printk(KERN_DEBUG "%s: STA %pM TX "
                                       "buffer full - dropping oldest frame\n",
                                       tx->dev->name, sta->sta.addr);
                        }
#endif
                        dev_kfree_skb(old);
                } else
                        tx->local->total_ps_buffered++;

                /* Queue frame to be sent after STA sends an PS Poll frame */
                if (skb_queue_empty(&sta->ps_tx_buf))
                        sta_info_set_tim_bit(sta);

                info->control.jiffies = jiffies;
                skb_queue_tail(&sta->ps_tx_buf, tx->skb);
                return TX_QUEUED;
        }
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        else if (unlikely(test_sta_flags(sta, WLAN_STA_PS))) {
                printk(KERN_DEBUG "%s: STA %pM in PS mode, but pspoll "
                       "set -> send frame\n", tx->dev->name,
                       sta->sta.addr);
        }
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
        clear_sta_flags(sta, WLAN_STA_PSPOLL);

        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_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(tx->skb->do_not_encrypt))
                tx->key = NULL;
        else if (tx->sta && (key = rcu_dereference(tx->sta->key)))
                tx->key = key;
        else if ((key = rcu_dereference(tx->sdata->default_key)))
                tx->key = key;
        else if (tx->sdata->drop_unencrypted &&
                 (tx->skb->protocol != cpu_to_be16(ETH_P_PAE)) &&
                 !(info->flags & IEEE80211_TX_CTL_INJECTED)) {
                I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
                return TX_DROP;
        } else
                tx->key = NULL;

        if (tx->key) {
                tx->key->tx_rx_count++;
                /* TODO: add threshold stuff again */

                switch (tx->key->conf.alg) {
                case ALG_WEP:
                        if (ieee80211_is_auth(hdr->frame_control))
                                break;
                case ALG_TKIP:
                case ALG_CCMP:
                        if (!ieee80211_is_data_present(hdr->frame_control))
                                tx->key = NULL;
                        break;
                }
        }

        if (!tx->key || !(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
                tx->skb->do_not_encrypt = 1;

        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, len;
        bool inval = false, rts = false, short_preamble = false;
        struct ieee80211_tx_rate_control txrc;

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

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

        len = min_t(int, tx->skb->len + FCS_LEN,
                         tx->local->fragmentation_threshold);

        /* set up the tx rate control struct we give the RC algo */
        txrc.hw = local_to_hw(tx->local);
        txrc.sband = sband;
        txrc.bss_conf = &tx->sdata->vif.bss_conf;
        txrc.skb = tx->skb;
        txrc.reported_rate.idx = -1;
        txrc.max_rate_idx = tx->sdata->max_ratectrl_rateidx;

        /* set up RTS protection if desired */
        if (tx->local->rts_threshold < IEEE80211_MAX_RTS_THRESHOLD &&
            len > tx->local->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_flags(tx->sta, WLAN_STA_SHORT_PREAMBLE))))
                txrc.short_preamble = short_preamble = true;


        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)
                tx->sta->last_tx_rate = txrc.reported_rate;

        if (unlikely(!info->control.rates[0].count))
                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(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_misc(struct ieee80211_tx_data *tx)
{
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);

        if (tx->sta)
                info->control.sta = &tx->sta->sta;

        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))
                return TX_CONTINUE;

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

        if (ieee80211_hdrlen(hdr->frame_control) < 24)
                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;
                tx->sdata->sequence_number &= IEEE80211_SCTL_SEQ;
                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 ieee80211_tx_result debug_noinline
ieee80211_tx_h_fragment(struct ieee80211_tx_data *tx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
        size_t hdrlen, per_fragm, num_fragm, payload_len, left;
        struct sk_buff **frags, *first, *frag;
        int i;
        u16 seq;
        u8 *pos;
        int frag_threshold = tx->local->fragmentation_threshold;

        if (!(tx->flags & IEEE80211_TX_FRAGMENTED))
                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(tx->flags & IEEE80211_TX_CTL_AMPDU ||
                    skb_get_queue_mapping(tx->skb) >=
                        ieee80211_num_regular_queues(&tx->local->hw)))
                return TX_DROP;

        first = tx->skb;

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        payload_len = first->len - hdrlen;
        per_fragm = frag_threshold - hdrlen - FCS_LEN;
        num_fragm = DIV_ROUND_UP(payload_len, per_fragm);

        frags = kzalloc(num_fragm * sizeof(struct sk_buff *), GFP_ATOMIC);
        if (!frags)
                goto fail;

        hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREFRAGS);
        seq = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_SEQ;
        pos = first->data + hdrlen + per_fragm;
        left = payload_len - per_fragm;
        for (i = 0; i < num_fragm - 1; i++) {
                struct ieee80211_hdr *fhdr;
                struct ieee80211_tx_info *info;
                size_t copylen;

                if (left <= 0)
                        goto fail;

                /* reserve enough extra head and tail room for possible
                 * encryption */
                frag = frags[i] =
                        dev_alloc_skb(tx->local->tx_headroom +
                                      frag_threshold +
                                      IEEE80211_ENCRYPT_HEADROOM +
                                      IEEE80211_ENCRYPT_TAILROOM);
                if (!frag)
                        goto fail;

                /* Make sure that all fragments use the same priority so
                 * that they end up using the same TX queue */
                frag->priority = first->priority;

                skb_reserve(frag, tx->local->tx_headroom +
                                  IEEE80211_ENCRYPT_HEADROOM);

                /* copy TX information */
                info = IEEE80211_SKB_CB(frag);
                memcpy(info, first->cb, sizeof(frag->cb));

                /* copy/fill in 802.11 header */
                fhdr = (struct ieee80211_hdr *) skb_put(frag, hdrlen);
                memcpy(fhdr, first->data, hdrlen);
                fhdr->seq_ctrl = cpu_to_le16(seq | ((i + 1) & IEEE80211_SCTL_FRAG));

                if (i == num_fragm - 2) {
                        /* clear MOREFRAGS bit for the last fragment */
                        fhdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREFRAGS);
                } else {
                        /*
                         * 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;
                        info->control.rates[4].idx = -1;
                        BUILD_BUG_ON(IEEE80211_TX_MAX_RATES != 5);
                        info->flags &= ~IEEE80211_TX_CTL_RATE_CTRL_PROBE;
                }

                /* copy data */
                copylen = left > per_fragm ? per_fragm : left;
                memcpy(skb_put(frag, copylen), pos, copylen);

                skb_copy_queue_mapping(frag, first);

                frag->do_not_encrypt = first->do_not_encrypt;

                pos += copylen;
                left -= copylen;
        }
        skb_trim(first, hdrlen + per_fragm);

        tx->num_extra_frag = num_fragm - 1;
        tx->extra_frag = frags;

        return TX_CONTINUE;

 fail:
        if (frags) {
                for (i = 0; i < num_fragm - 1; i++)
                        if (frags[i])
                                dev_kfree_skb(frags[i]);
                kfree(frags);
        }
        I802_DEBUG_INC(tx->local->tx_handlers_drop_fragment);
        return TX_DROP;
}

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.alg) {
        case ALG_WEP:
                return ieee80211_crypto_wep_encrypt(tx);
        case ALG_TKIP:
                return ieee80211_crypto_tkip_encrypt(tx);
        case ALG_CCMP:
                return ieee80211_crypto_ccmp_encrypt(tx);
        }

        /* not reached */
        WARN_ON(1);
        return TX_DROP;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_calculate_duration(struct ieee80211_tx_data *tx)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
        int next_len, i;
        int group_addr = is_multicast_ether_addr(hdr->addr1);

        if (!(tx->flags & IEEE80211_TX_FRAGMENTED)) {
                hdr->duration_id = ieee80211_duration(tx, group_addr, 0);
                return TX_CONTINUE;
        }

        hdr->duration_id = ieee80211_duration(tx, group_addr,
                                              tx->extra_frag[0]->len);

        for (i = 0; i < tx->num_extra_frag; i++) {
                if (i + 1 < tx->num_extra_frag)
                        next_len = tx->extra_frag[i + 1]->len;
                else
                        next_len = 0;

                hdr = (struct ieee80211_hdr *)tx->extra_frag[i]->data;
                hdr->duration_id = ieee80211_duration(tx, 0, next_len);
        }

        return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_stats(struct ieee80211_tx_data *tx)
{
        int i;

        if (!tx->sta)
                return TX_CONTINUE;

        tx->sta->tx_packets++;
        tx->sta->tx_fragments++;
        tx->sta->tx_bytes += tx->skb->len;
        if (tx->extra_frag) {
                tx->sta->tx_fragments += tx->num_extra_frag;
                for (i = 0; i < tx->num_extra_frag; i++)
                        tx->sta->tx_bytes += tx->extra_frag[i]->len;
        }

        return TX_CONTINUE;
}


/* actual transmit path */

/*
 * deal with packet injection down monitor interface
 * with Radiotap Header -- only called for monitor mode interface
 */
static ieee80211_tx_result
__ieee80211_parse_tx_radiotap(struct ieee80211_tx_data *tx,
                              struct sk_buff *skb)
{
        /*
         * this is the moment to interpret and discard the radiotap header that
         * must be at the start of the packet injected in Monitor mode
         *
         * Need to take some care with endian-ness since radiotap
         * args are little-endian
         */

        struct ieee80211_radiotap_iterator iterator;
        struct ieee80211_radiotap_header *rthdr =
                (struct ieee80211_radiotap_header *) skb->data;
        struct ieee80211_supported_band *sband;
        int ret = ieee80211_radiotap_iterator_init(&iterator, rthdr, skb->len);

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

        skb->do_not_encrypt = 1;
        tx->flags &= ~IEEE80211_TX_FRAGMENTED;

        /*
         * 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 TX_DROP;

                                skb_trim(skb, skb->len - FCS_LEN);
                        }
                        if (*iterator.this_arg & IEEE80211_RADIOTAP_F_WEP)
                                tx->skb->do_not_encrypt = 0;
                        if (*iterator.this_arg & IEEE80211_RADIOTAP_F_FRAG)
                                tx->flags |= IEEE80211_TX_FRAGMENTED;
                        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 TX_DROP;

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

        return TX_CONTINUE;
}

/*
 * initialises @tx
 */
static ieee80211_tx_result
__ieee80211_tx_prepare(struct ieee80211_tx_data *tx,
                       struct sk_buff *skb,
                       struct net_device *dev)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_hdr *hdr;
        struct ieee80211_sub_if_data *sdata;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

        int hdrlen;

        memset(tx, 0, sizeof(*tx));
        tx->skb = skb;
        tx->dev = dev; /* use original interface */
        tx->local = local;
        tx->sdata = IEEE80211_DEV_TO_SUB_IF(dev);
        tx->channel = local->hw.conf.channel;
        /*
         * Set this flag (used below to indicate "automatic fragmentation"),
         * it will be cleared/left by radiotap as desired.
         */
        tx->flags |= IEEE80211_TX_FRAGMENTED;

        /* process and remove the injection radiotap header */
        sdata = IEEE80211_DEV_TO_SUB_IF(dev);
        if (unlikely(info->flags & IEEE80211_TX_CTL_INJECTED)) {
                if (__ieee80211_parse_tx_radiotap(tx, skb) == TX_DROP)
                        return TX_DROP;

                /*
                 * __ieee80211_parse_tx_radiotap has now removed
                 * the radiotap header that was present and pre-filled
                 * 'tx' with tx control information.
                 */
        }

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

        tx->sta = sta_info_get(local, hdr->addr1);

        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;
                info->flags &= ~IEEE80211_TX_CTL_NO_ACK;
        }

        if (tx->flags & IEEE80211_TX_FRAGMENTED) {
                if ((tx->flags & IEEE80211_TX_UNICAST) &&
                    skb->len + FCS_LEN > local->fragmentation_threshold &&
                    !local->ops->set_frag_threshold &&
                    !(info->flags & IEEE80211_TX_CTL_AMPDU))
                        tx->flags |= IEEE80211_TX_FRAGMENTED;
                else
                        tx->flags &= ~IEEE80211_TX_FRAGMENTED;
        }

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

        hdrlen = ieee80211_hdrlen(hdr->frame_control);
        if (skb->len > hdrlen + sizeof(rfc1042_header) + 2) {
                u8 *pos = &skb->data[hdrlen + sizeof(rfc1042_header)];
                tx->ethertype = (pos[0] << 8) | pos[1];
        }
        info->flags |= IEEE80211_TX_CTL_FIRST_FRAGMENT;

        return TX_CONTINUE;
}

/*
 * NB: @tx is uninitialised when passed in here
 */
static int ieee80211_tx_prepare(struct ieee80211_local *local,
                                struct ieee80211_tx_data *tx,
                                struct sk_buff *skb)
{
        struct net_device *dev;

        dev = dev_get_by_index(&init_net, skb->iif);
        if (unlikely(dev && !is_ieee80211_device(local, dev))) {
                dev_put(dev);
                dev = NULL;
        }
        if (unlikely(!dev))
                return -ENODEV;
        /* initialises tx with control */
        __ieee80211_tx_prepare(tx, skb, dev);
        dev_put(dev);
        return 0;
}

static int __ieee80211_tx(struct ieee80211_local *local, struct sk_buff *skb,
                          struct ieee80211_tx_data *tx)
{
        struct ieee80211_tx_info *info;
        int ret, i;

        if (skb) {
                if (netif_subqueue_stopped(local->mdev, skb))
                        return IEEE80211_TX_AGAIN;
                info =  IEEE80211_SKB_CB(skb);

                ret = local->ops->tx(local_to_hw(local), skb);
                if (ret)
                        return IEEE80211_TX_AGAIN;
                local->mdev->trans_start = jiffies;
                ieee80211_led_tx(local, 1);
        }
        if (tx->extra_frag) {
                for (i = 0; i < tx->num_extra_frag; i++) {
                        if (!tx->extra_frag[i])
                                continue;
                        info = IEEE80211_SKB_CB(tx->extra_frag[i]);
                        info->flags &= ~(IEEE80211_TX_CTL_CLEAR_PS_FILT |
                                         IEEE80211_TX_CTL_FIRST_FRAGMENT);
                        if (netif_subqueue_stopped(local->mdev,
                                                   tx->extra_frag[i]))
                                return IEEE80211_TX_FRAG_AGAIN;

                        ret = local->ops->tx(local_to_hw(local),
                                            tx->extra_frag[i]);
                        if (ret)
                                return IEEE80211_TX_FRAG_AGAIN;
                        local->mdev->trans_start = jiffies;
                        ieee80211_led_tx(local, 1);
                        tx->extra_frag[i] = NULL;
                }
                kfree(tx->extra_frag);
                tx->extra_frag = NULL;
        }
        return IEEE80211_TX_OK;
}

/*
 * 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 sk_buff *skb = tx->skb;
        ieee80211_tx_result res = TX_DROP;
        int i;

#define CALL_TXH(txh)           \
        res = txh(tx);          \
        if (res != TX_CONTINUE) \
                goto txh_done;

        CALL_TXH(ieee80211_tx_h_check_assoc)
        CALL_TXH(ieee80211_tx_h_ps_buf)
        CALL_TXH(ieee80211_tx_h_select_key)
        CALL_TXH(ieee80211_tx_h_michael_mic_add)
        CALL_TXH(ieee80211_tx_h_rate_ctrl)
        CALL_TXH(ieee80211_tx_h_misc)
        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_encrypt)
        CALL_TXH(ieee80211_tx_h_calculate_duration)
        CALL_TXH(ieee80211_tx_h_stats)
#undef CALL_TXH

 txh_done:
        if (unlikely(res == TX_DROP)) {
                I802_DEBUG_INC(tx->local->tx_handlers_drop);
                dev_kfree_skb(skb);
                for (i = 0; i < tx->num_extra_frag; i++)
                        if (tx->extra_frag[i])
                                dev_kfree_skb(tx->extra_frag[i]);
                kfree(tx->extra_frag);
                return -1;
        } else if (unlikely(res == TX_QUEUED)) {
                I802_DEBUG_INC(tx->local->tx_handlers_queued);
                return -1;
        }

        return 0;
}

static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct sta_info *sta;
        struct ieee80211_tx_data tx;
        ieee80211_tx_result res_prepare;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        int ret, i;
        u16 queue;

        queue = skb_get_queue_mapping(skb);

        WARN_ON(test_bit(queue, local->queues_pending));

        if (unlikely(skb->len < 10)) {
                dev_kfree_skb(skb);
                return 0;
        }

        rcu_read_lock();

        /* initialises tx */
        res_prepare = __ieee80211_tx_prepare(&tx, skb, dev);

        if (res_prepare == TX_DROP) {
                dev_kfree_skb(skb);
                rcu_read_unlock();
                return 0;
        }

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

        if (invoke_tx_handlers(&tx))
                goto out;

retry:
        ret = __ieee80211_tx(local, skb, &tx);
        if (ret) {
                struct ieee80211_tx_stored_packet *store;

                /*
                 * Since there are no fragmented frames on A-MPDU
                 * queues, there's no reason for a driver to reject
                 * a frame there, warn and drop it.
                 */
                if (WARN_ON(queue >= ieee80211_num_regular_queues(&local->hw)))
                        goto drop;

                store = &local->pending_packet[queue];

                if (ret == IEEE80211_TX_FRAG_AGAIN)
                        skb = NULL;

                set_bit(queue, local->queues_pending);
                smp_mb();
                /*
                 * When the driver gets out of buffers during sending of
                 * fragments and calls ieee80211_stop_queue, the netif
                 * subqueue is stopped. There is, however, a small window
                 * in which the PENDING bit is not yet set. If a buffer
                 * gets available in that window (i.e. driver calls
                 * ieee80211_wake_queue), we would end up with ieee80211_tx
                 * called with the PENDING bit still set. Prevent this by
                 * continuing transmitting here when that situation is
                 * possible to have happened.
                 */
                if (!__netif_subqueue_stopped(local->mdev, queue)) {
                        clear_bit(queue, local->queues_pending);
                        goto retry;
                }
                store->skb = skb;
                store->extra_frag = tx.extra_frag;
                store->num_extra_frag = tx.num_extra_frag;
        }
 out:
        rcu_read_unlock();
        return 0;

 drop:
        if (skb)
                dev_kfree_skb(skb);
        for (i = 0; i < tx.num_extra_frag; i++)
                if (tx.extra_frag[i])
                        dev_kfree_skb(tx.extra_frag[i]);
        kfree(tx.extra_frag);
        rcu_read_unlock();
        return 0;
}

/* device xmit handlers */

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

        /*
         * This could be optimised, devices that do full hardware
         * crypto (including TKIP MMIC) need no tailroom... But we
         * have no drivers for such devices currently.
         */
        if (may_encrypt) {
                tail_need = IEEE80211_ENCRYPT_TAILROOM;
                tail_need -= skb_tailroom(skb);
                tail_need = max_t(int, tail_need, 0);
        }

        if (head_need || tail_need) {
                /* Sorry. Can't account for this any more */
                skb_orphan(skb);
        }

        if (skb_header_cloned(skb))
                I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
        else
                I802_DEBUG_INC(local->tx_expand_skb_head);

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

        /* update truesize too */
        skb->truesize += head_need + tail_need;

        return 0;
}

int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ieee80211_master_priv *mpriv = netdev_priv(dev);
        struct ieee80211_local *local = mpriv->local;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct net_device *odev = NULL;
        struct ieee80211_sub_if_data *osdata;
        int headroom;
        bool may_encrypt;
        enum {
                NOT_MONITOR,
                FOUND_SDATA,
                UNKNOWN_ADDRESS,
        } monitor_iface = NOT_MONITOR;
        int ret;

        if (skb->iif)
                odev = dev_get_by_index(&init_net, skb->iif);
        if (unlikely(odev && !is_ieee80211_device(local, odev))) {
                dev_put(odev);
                odev = NULL;
        }
        if (unlikely(!odev)) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                printk(KERN_DEBUG "%s: Discarded packet with nonexistent "
                       "originating device\n", dev->name);
#endif
                dev_kfree_skb(skb);
                return 0;
        }

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

        info->flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;

        osdata = IEEE80211_DEV_TO_SUB_IF(odev);

        if (ieee80211_vif_is_mesh(&osdata->vif) &&
            ieee80211_is_data(hdr->frame_control)) {
                if (is_multicast_ether_addr(hdr->addr3))
                        memcpy(hdr->addr1, hdr->addr3, ETH_ALEN);
                else
                        if (mesh_nexthop_lookup(skb, osdata))
                                return  0;
                if (memcmp(odev->dev_addr, hdr->addr4, ETH_ALEN) != 0)
                        IEEE80211_IFSTA_MESH_CTR_INC(&osdata->u.mesh,
                                                            fwded_frames);
        } else if (unlikely(osdata->vif.type == NL80211_IFTYPE_MONITOR)) {
                struct ieee80211_sub_if_data *sdata;
                int hdrlen;
                u16 len_rthdr;

                info->flags |= IEEE80211_TX_CTL_INJECTED;
                monitor_iface = UNKNOWN_ADDRESS;

                len_rthdr = ieee80211_get_radiotap_len(skb->data);
                hdr = (struct ieee80211_hdr *)skb->data + len_rthdr;
                hdrlen = ieee80211_hdrlen(hdr->frame_control);

                /* check the header is complete in the frame */
                if (likely(skb->len >= len_rthdr + hdrlen)) {
                        /*
                         * We process outgoing injected frames that have a
                         * local address we handle as though they are our
                         * own frames.
                         * This code here isn't entirely correct, the local
                         * MAC address is not necessarily enough to find
                         * the interface to use; for that proper VLAN/WDS
                         * support we will need a different mechanism.
                         */

                        rcu_read_lock();
                        list_for_each_entry_rcu(sdata, &local->interfaces,
                                                list) {
                                if (!netif_running(sdata->dev))
                                        continue;
                                if (compare_ether_addr(sdata->dev->dev_addr,
                                                       hdr->addr2)) {
                                        dev_hold(sdata->dev);
                                        dev_put(odev);
                                        osdata = sdata;
                                        odev = osdata->dev;
                                        skb->iif = sdata->dev->ifindex;
                                        monitor_iface = FOUND_SDATA;
                                        break;
                                }
                        }
                        rcu_read_unlock();
                }
        }

        may_encrypt = !skb->do_not_encrypt;

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

        if (ieee80211_skb_resize(osdata->local, skb, headroom, may_encrypt)) {
                dev_kfree_skb(skb);
                dev_put(odev);
                return 0;
        }

        if (osdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                osdata = container_of(osdata->bss,
                                      struct ieee80211_sub_if_data,
                                      u.ap);
        if (likely(monitor_iface != UNKNOWN_ADDRESS))
                info->control.vif = &osdata->vif;
        ret = ieee80211_tx(odev, skb);
        dev_put(odev);

        return ret;
}

int ieee80211_monitor_start_xmit(struct sk_buff *skb,
                                 struct net_device *dev)
{
        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
        struct ieee80211_radiotap_header *prthdr =
                (struct ieee80211_radiotap_header *)skb->data;
        u16 len_rthdr;

        /* 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 */

        skb->dev = local->mdev;

        /* needed because we set skb device to master */
        skb->iif = dev->ifindex;

        /* sometimes we do encrypt injected frames, will be fixed
         * up in radiotap parser if not wanted */
        skb->do_not_encrypt = 0;

        /*
         * 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);

        /* pass the radiotap header up to the next stage intact */
        dev_queue_xmit(skb);
        return NETDEV_TX_OK;

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

/**
 * ieee80211_subif_start_xmit - netif start_xmit function for Ethernet-type
 * subinterfaces (wlan#, WDS, and VLAN interfaces)
 * @skb: packet to be sent
 * @dev: incoming interface
 *
 * Returns: 0 on success (and frees skb in this case) or 1 on failure (skb will
 * not be freed, and caller is responsible for either retrying later or freeing
 * skb).
 *
 * This function takes in an Ethernet header and encapsulates it with suitable
 * IEEE 802.11 header based on which interface the packet is coming in. The
 * encapsulated packet will then be passed to master interface, wlan#.11, for
 * transmission (through low-level driver).
 */
int 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;
        int ret = 1, head_need;
        u16 ethertype, hdrlen,  meshhdrlen = 0;
        __le16 fc;
        struct ieee80211_hdr hdr;
        struct ieee80211s_hdr mesh_hdr;
        const u8 *encaps_data;
        int encaps_len, skip_header_bytes;
        int nh_pos, h_pos;
        struct sta_info *sta;
        u32 sta_flags = 0;

        if (unlikely(skb->len < ETH_HLEN)) {
                ret = 0;
                goto fail;
        }

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

        /* 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:
        case NL80211_IFTYPE_AP_VLAN:
                fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS);
                /* DA BSSID SA */
                memcpy(hdr.addr1, skb->data, ETH_ALEN);
                memcpy(hdr.addr2, dev->dev_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, dev->dev_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:
                fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
                if (!sdata->u.mesh.mshcfg.dot11MeshTTL) {
                        /* Do not send frames with mesh_ttl == 0 */
                        sdata->u.mesh.mshstats.dropped_frames_ttl++;
                        ret = 0;
                        goto fail;
                }
                memset(&mesh_hdr, 0, sizeof(mesh_hdr));

                if (compare_ether_addr(dev->dev_addr,
                                          skb->data + ETH_ALEN) == 0) {
                        /* RA TA DA SA */
                        memset(hdr.addr1, 0, ETH_ALEN);
                        memcpy(hdr.addr2, dev->dev_addr, ETH_ALEN);
                        memcpy(hdr.addr3, skb->data, ETH_ALEN);
                        memcpy(hdr.addr4, skb->data + ETH_ALEN, ETH_ALEN);
                        meshhdrlen = ieee80211_new_mesh_header(&mesh_hdr, sdata);
                } else {
                        /* packet from other interface */
                        struct mesh_path *mppath;

                        memset(hdr.addr1, 0, ETH_ALEN);
                        memcpy(hdr.addr2, dev->dev_addr, ETH_ALEN);
                        memcpy(hdr.addr4, dev->dev_addr, ETH_ALEN);

                        if (is_multicast_ether_addr(skb->data))
                                memcpy(hdr.addr3, skb->data, ETH_ALEN);
                        else {
                                rcu_read_lock();
                                mppath = mpp_path_lookup(skb->data, sdata);
                                if (mppath)
                                        memcpy(hdr.addr3, mppath->mpp, ETH_ALEN);
                                else
                                        memset(hdr.addr3, 0xff, ETH_ALEN);
                                rcu_read_unlock();
                        }

                        mesh_hdr.flags |= MESH_FLAGS_AE_A5_A6;
                        mesh_hdr.ttl = sdata->u.mesh.mshcfg.dot11MeshTTL;
                        put_unaligned(cpu_to_le32(sdata->u.mesh.mesh_seqnum), &mesh_hdr.seqnum);
                        memcpy(mesh_hdr.eaddr1, skb->data, ETH_ALEN);
                        memcpy(mesh_hdr.eaddr2, skb->data + ETH_ALEN, ETH_ALEN);
                        sdata->u.mesh.mesh_seqnum++;
                        meshhdrlen = 18;
                }
                hdrlen = 30;
                break;
#endif
        case NL80211_IFTYPE_STATION:
                fc |= cpu_to_le16(IEEE80211_FCTL_TODS);
                /* BSSID SA DA */
                memcpy(hdr.addr1, sdata->u.sta.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.sta.bssid, ETH_ALEN);
                hdrlen = 24;
                break;
        default:
                ret = 0;
                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)
         */
        if (!is_multicast_ether_addr(hdr.addr1)) {
                rcu_read_lock();
                sta = sta_info_get(local, hdr.addr1);
                if (sta)
                        sta_flags = get_sta_flags(sta);
                rcu_read_unlock();
        }

        /* receiver and we are QoS enabled, use a QoS type frame */
        if (sta_flags & WLAN_STA_WME &&
            ieee80211_num_regular_queues(&local->hw) >= 4) {
                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 (!ieee80211_vif_is_mesh(&sdata->vif) &&
                unlikely(!is_multicast_ether_addr(hdr.addr1) &&
                      !(sta_flags & WLAN_STA_AUTHORIZED) &&
                      !(ethertype == ETH_P_PAE &&
                       compare_ether_addr(dev->dev_addr,
                                          skb->data + ETH_ALEN) == 0))) {
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                if (net_ratelimit())
                        printk(KERN_DEBUG "%s: dropped frame to %pM"
                               " (unauthorized port)\n", dev->name,
                               hdr.addr1);
#endif

                I802_DEBUG_INC(local->tx_handlers_drop_unauth_port);

                ret = 0;
                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;
        }

        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(local, skb, head_need, true))
                        goto fail;
        }

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

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

        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;

        skb->iif = dev->ifindex;

        skb->dev = local->mdev;
        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);

        dev->trans_start = jiffies;
        dev_queue_xmit(skb);

        return 0;

 fail:
        if (!ret)
                dev_kfree_skb(skb);

        return ret;
}


/*
 * 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)
{
        int i, j;
        struct ieee80211_tx_stored_packet *store;

        for (i = 0; i < ieee80211_num_regular_queues(&local->hw); i++) {
                if (!test_bit(i, local->queues_pending))
                        continue;
                store = &local->pending_packet[i];
                kfree_skb(store->skb);
                for (j = 0; j < store->num_extra_frag; j++)
                        kfree_skb(store->extra_frag[j]);
                kfree(store->extra_frag);
                clear_bit(i, local->queues_pending);
        }
}

/*
 * Transmit all pending packets. Called from tasklet, locks master device
 * TX lock so that no new packets can come in.
 */
void ieee80211_tx_pending(unsigned long data)
{
        struct ieee80211_local *local = (struct ieee80211_local *)data;
        struct net_device *dev = local->mdev;
        struct ieee80211_tx_stored_packet *store;
        struct ieee80211_tx_data tx;
        int i, ret;

        netif_tx_lock_bh(dev);
        for (i = 0; i < ieee80211_num_regular_queues(&local->hw); i++) {
                /* Check that this queue is ok */
                if (__netif_subqueue_stopped(local->mdev, i) &&
                    !test_bit(i, local->queues_pending_run))
                        continue;

                if (!test_bit(i, local->queues_pending)) {
                        clear_bit(i, local->queues_pending_run);
                        ieee80211_wake_queue(&local->hw, i);
                        continue;
                }

                clear_bit(i, local->queues_pending_run);
                netif_start_subqueue(local->mdev, i);

                store = &local->pending_packet[i];
                tx.extra_frag = store->extra_frag;
                tx.num_extra_frag = store->num_extra_frag;
                tx.flags = 0;
                ret = __ieee80211_tx(local, store->skb, &tx);
                if (ret) {
                        if (ret == IEEE80211_TX_FRAG_AGAIN)
                                store->skb = NULL;
                } else {
                        clear_bit(i, local->queues_pending);
                        ieee80211_wake_queue(&local->hw, i);
                }
        }
        netif_tx_unlock_bh(dev);
}

/* functions for drivers to get certain frames */

static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
                                     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 = beacon->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++ = beacon->dtim_period;

        if (bss->dtim_count == 0 && !skb_queue_empty(&bss->ps_bc_buf))
                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 */
                memcpy(pos, bss->tim + n1, n2 - n1 + 1);

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

struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
                                     struct ieee80211_vif *vif)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sk_buff *skb = NULL;
        struct ieee80211_tx_info *info;
        struct net_device *bdev;
        struct ieee80211_sub_if_data *sdata = NULL;
        struct ieee80211_if_ap *ap = NULL;
        struct ieee80211_if_sta *ifsta = NULL;
        struct beacon_data *beacon;
        struct ieee80211_supported_band *sband;
        enum ieee80211_band band = local->hw.conf.channel->band;

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

        rcu_read_lock();

        sdata = vif_to_sdata(vif);
        bdev = sdata->dev;

        if (sdata->vif.type == NL80211_IFTYPE_AP) {
                ap = &sdata->u.ap;
                beacon = rcu_dereference(ap->beacon);
                if (ap && 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(local, ap, skb, beacon);
                        } else {
                                unsigned long flags;

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

                        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_hdr *hdr;
                ifsta = &sdata->u.sta;

                if (!ifsta->probe_resp)
                        goto out;

                skb = skb_copy(ifsta->probe_resp, 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;
                u8 *pos;

                /* headroom, head length, tail length and maximum TIM length */
                skb = dev_alloc_skb(local->tx_headroom + 400);
                if (!skb)
                        goto out;

                skb_reserve(skb, local->hw.extra_tx_headroom);
                mgmt = (struct ieee80211_mgmt *)
                        skb_put(skb, 24 + sizeof(mgmt->u.beacon));
                memset(mgmt, 0, 24 + sizeof(mgmt->u.beacon));
                mgmt->frame_control =
                    cpu_to_le16(IEEE80211_FTYPE_MGMT | IEEE80211_STYPE_BEACON);
                memset(mgmt->da, 0xff, ETH_ALEN);
                memcpy(mgmt->sa, sdata->dev->dev_addr, ETH_ALEN);
                /* BSSID is left zeroed, wildcard value */
                mgmt->u.beacon.beacon_int =
                        cpu_to_le16(local->hw.conf.beacon_int);
                mgmt->u.beacon.capab_info = 0x0; /* 0x0 for MPs */

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

                mesh_mgmt_ies_add(skb, sdata);
        } else {
                WARN_ON(1);
                goto out;
        }

        info = IEEE80211_SKB_CB(skb);

        skb->do_not_encrypt = 1;

        info->band = band;
        /*
         * XXX: For now, always use the lowest rate
         */
        info->control.rates[0].idx = 0;
        info->control.rates[0].count = 1;
        info->control.rates[1].idx = -1;
        info->control.rates[2].idx = -1;
        info->control.rates[3].idx = -1;
        info->control.rates[4].idx = -1;
        BUILD_BUG_ON(IEEE80211_TX_MAX_RATES != 5);

        info->control.vif = vif;

        info->flags |= IEEE80211_TX_CTL_NO_ACK;
        info->flags |= IEEE80211_TX_CTL_CLEAR_PS_FILT;
        info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
 out:
        rcu_read_unlock();
        return skb;
}
EXPORT_SYMBOL(ieee80211_beacon_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 sta_info *sta;
        struct ieee80211_tx_data tx;
        struct net_device *bdev;
        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);
        bdev = sdata->dev;
        bss = &sdata->u.ap;

        if (!bss)
                return NULL;

        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)
                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(local, &tx, skb))
                        break;
                dev_kfree_skb_any(skb);
        }

        info = IEEE80211_SKB_CB(skb);

        sta = tx.sta;
        tx.flags |= IEEE80211_TX_PS_BUFFERED;
        tx.channel = local->hw.conf.channel;
        info->band = tx.channel->band;

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

        return skb;
}
EXPORT_SYMBOL(ieee80211_get_buffered_bc);