Btrfs: don't set up allocation result twice

[linux-2.6.git] / 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 <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, 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 inline int 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_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: local->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)
            && (local->uapsd_queues & IEEE80211_WMM_IE_STA_QOSINFO_AC_VO)
            && skb_get_queue_mapping(tx->skb) == 0)
                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 &&
                             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->sdata->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);
        }

        /*
         * 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++;
                                dev_kfree_skb(skb);
                                break;
                        }
                }
        }

        rcu_read_unlock();

        local->total_ps_buffered = total;
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        wiphy_debug(local->hw.wiphy, "PS buffers full - purged %d frames\n",
                    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;

        info->flags |= IEEE80211_TX_CTL_SEND_AFTER_DTIM;

        /* 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) {
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                if (net_ratelimit())
                        printk(KERN_DEBUG "%s: BC TX buffer full - dropping the oldest frame\n",
                               tx->sdata->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;
}

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 ||
                     ieee80211_is_probe_resp(hdr->frame_control) ||
                     ieee80211_is_auth(hdr->frame_control) ||
                     ieee80211_is_assoc_resp(hdr->frame_control) ||
                     ieee80211_is_reassoc_resp(hdr->frame_control)))
                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_POLL_RESPONSE))) {
                int ac = skb_get_queue_mapping(tx->skb);

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                printk(KERN_DEBUG "STA %pM aid %d: PS buffer for AC %d\n",
                       sta->sta.addr, sta->sta.aid, ac);
#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[ac]) >= STA_MAX_TX_BUFFER) {
                        struct sk_buff *old = skb_dequeue(&sta->ps_tx_buf[ac]);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                        if (net_ratelimit())
                                printk(KERN_DEBUG "%s: STA %pM TX buffer for "
                                       "AC %d full - dropping oldest frame\n",
                                       tx->sdata->name, sta->sta.addr, ac);
#endif
                        dev_kfree_skb(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;
        }
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        else if (unlikely(test_sta_flag(sta, WLAN_STA_PS_STA))) {
                printk(KERN_DEBUG
                       "%s: STA %pM in PS mode, but polling/in SP -> send frame\n",
                       tx->sdata->name, sta->sta.addr);
        }
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

        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 = NULL;
        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 (tx->sdata->drop_unencrypted &&
                 (tx->skb->protocol != tx->sdata->control_port_protocol) &&
                 !(info->flags & IEEE80211_TX_CTL_INJECTED) &&
                 (!ieee80211_is_robust_mgmt_frame(hdr) ||
                  (ieee80211_is_action(hdr->frame_control) &&
                   tx->sta && test_sta_flag(tx->sta, WLAN_STA_MFP)))) {
                I802_DEBUG_INC(tx->local->tx_handlers_drop_unencrypted);
                return TX_DROP;
        } else
                tx->key = NULL;

        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:
                        if (ieee80211_is_auth(hdr->frame_control))
                                break;
                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) &&
                                        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[tx->channel->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 = 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.rate_idx_mask = tx->sdata->rc_rateidx_mask[tx->channel->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;
        txrc.bss = (tx->sdata->vif.type == NL80211_IFTYPE_AP ||
                    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,
                 tx->channel->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_local *local,
                              struct sk_buff *skb, int hdrlen,
                              int frag_threshold)
{
        struct sk_buff *tail = skb, *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;

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

        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;

        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->local, skb, hdrlen, frag_threshold))
                return TX_DROP;

        /* update duration/seq/flags of fragments */
        fragnum = 0;
        do {
                int next_len;
                const __le16 morefrags = cpu_to_le16(IEEE80211_FCTL_MOREFRAGS);

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

                if (skb->next) {
                        hdr->frame_control |= morefrags;
                        next_len = skb->next->len;
                        /*
                         * 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;
                } else {
                        hdr->frame_control &= ~morefrags;
                        next_len = 0;
                }
                hdr->duration_id = ieee80211_duration(tx, 0, next_len);
                hdr->seq_ctrl |= cpu_to_le16(fragnum & IEEE80211_SCTL_FRAG);
                fragnum++;
        } while ((skb = skb->next));

        return TX_CONTINUE;
}

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

        if (!tx->sta)
                return TX_CONTINUE;

        tx->sta->tx_packets++;
        do {
                tx->sta->tx_fragments++;
                tx->sta->tx_bytes += skb->len;
        } while ((skb = skb->next));

        return TX_CONTINUE;
}

static ieee80211_tx_result debug_noinline
ieee80211_tx_h_encrypt(struct ieee80211_tx_data *tx)
{
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);

        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:
                /* handle hw-only algorithm */
                if (info->control.hw_key) {
                        ieee80211_tx_set_protected(tx);
                        return TX_CONTINUE;
                }
                break;

        }

        return TX_DROP;
}

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

        do {
                hdr = (void *) skb->data;
                if (unlikely(ieee80211_is_pspoll(hdr->frame_control)))
                        break; /* must not overwrite AID */
                next_len = skb->next ? skb->next->len : 0;
                group_addr = is_multicast_ether_addr(hdr->addr1);

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

        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;

        if (test_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state)) {
                info->flags |= IEEE80211_TX_CTL_AMPDU;
        } 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;
                } else {
                        queued = true;
                        info->control.vif = &tx->sdata->vif;
                        info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
                        __skb_queue_tail(&tid_tx->pending, skb);
                }
                spin_unlock(&tx->sta->lock);
        }

        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;
        tx->channel = local->hw.conf.channel;

        /*
         * 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->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 (unlikely(local->wifi_wme_noack_test))
                        info->flags |= IEEE80211_TX_CTL_NO_ACK;
                /*
                 * Flags are initialized to 0. Hence, no need to
                 * explicitly unset IEEE80211_TX_CTL_NO_ACK since
                 * it might already be set for injected frames.
                 */
        }

        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;
}

/*
 * Returns false if the frame couldn't be transmitted but was queued instead.
 */
static bool __ieee80211_tx(struct ieee80211_local *local, struct sk_buff **skbp,
                           struct sta_info *sta, bool txpending)
{
        struct sk_buff *skb = *skbp, *next;
        struct ieee80211_tx_info *info;
        struct ieee80211_sub_if_data *sdata;
        unsigned long flags;
        int len;
        bool fragm = false;

        while (skb) {
                int q = skb_get_queue_mapping(skb);
                __le16 fc;

                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.
                         */

                        do {
                                next = skb->next;
                                skb->next = NULL;
                                /*
                                 * NB: If txpending is true, next must already
                                 * be NULL since we must've gone through this
                                 * loop before already; therefore we can just
                                 * queue the frame to the head without worrying
                                 * about reordering of fragments.
                                 */
                                if (unlikely(txpending))
                                        __skb_queue_head(&local->pending[q],
                                                         skb);
                                else
                                        __skb_queue_tail(&local->pending[q],
                                                         skb);
                        } while ((skb = next));

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

                info = IEEE80211_SKB_CB(skb);

                if (fragm)
                        info->flags &= ~(IEEE80211_TX_CTL_CLEAR_PS_FILT |
                                         IEEE80211_TX_CTL_FIRST_FRAGMENT);

                next = skb->next;
                len = skb->len;

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

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

                switch (sdata->vif.type) {
                case NL80211_IFTYPE_MONITOR:
                        info->control.vif = NULL;
                        break;
                case NL80211_IFTYPE_AP_VLAN:
                        info->control.vif = &container_of(sdata->bss,
                                struct ieee80211_sub_if_data, u.ap)->vif;
                        break;
                default:
                        /* keep */
                        break;
                }

                if (sta && sta->uploaded)
                        info->control.sta = &sta->sta;
                else
                        info->control.sta = NULL;

                fc = ((struct ieee80211_hdr *)skb->data)->frame_control;
                drv_tx(local, skb);

                ieee80211_tpt_led_trig_tx(local, fc, len);
                *skbp = skb = next;
                ieee80211_led_tx(local, 1);
                fragm = true;
        }

        return true;
}

/*
 * 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;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(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))
                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);
                while (skb) {
                        struct sk_buff *next;

                        next = skb->next;
                        dev_kfree_skb(skb);
                        skb = next;
                }
                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;

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

        rcu_read_lock();

        /* initialises tx */
        res_prepare = ieee80211_tx_prepare(sdata, &tx, skb);

        if (unlikely(res_prepare == TX_DROP)) {
                dev_kfree_skb(skb);
                goto out;
        } else if (unlikely(res_prepare == TX_QUEUED)) {
                goto out;
        }

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

        if (!invoke_tx_handlers(&tx))
                result = __ieee80211_tx(local, &tx.skb, 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)) {
                dev_kfree_skb(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))
                        if (mesh_nexthop_lookup(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 (compare_ether_addr(payload, rfc1042_header) == 0)
                        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 (compare_ether_addr(tmp_sdata->vif.addr, hdr->addr2) == 0) {
                        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 */
}

/**
 * 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).
 */
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 ret = NETDEV_TX_BUSY, 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;
        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;
        struct sk_buff *tmp_skb;
        bool tdls_direct = false;

        if (unlikely(skb->len < ETH_HLEN)) {
                ret = NETDEV_TX_OK;
                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++;
                        ret = NETDEV_TX_OK;
                        goto fail;
                }
                rcu_read_lock();
                if (!is_multicast_ether_addr(skb->data))
                        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 (compare_ether_addr(sdata->vif.addr,
                                       skb->data + ETH_ALEN) == 0 &&
                    !(mppath && compare_ether_addr(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 {
                        int is_mesh_mcast = 1;
                        const u8 *mesh_da;

                        if (is_multicast_ether_addr(skb->data))
                                /* DA TA mSA AE:SA */
                                mesh_da = skb->data;
                        else {
                                static const u8 bcast[ETH_ALEN] =
                                        { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
                                if (mppath) {
                                        /* RA TA mDA mSA AE:DA SA */
                                        mesh_da = mppath->mpp;
                                        is_mesh_mcast = 0;
                                } else {
                                        /* DA TA mSA AE:SA */
                                        mesh_da = bcast;
                                }
                        }
                        hdrlen = ieee80211_fill_mesh_addresses(&hdr, &fc,
                                        mesh_da, sdata->vif.addr);
                        rcu_read_unlock();
                        if (is_mesh_mcast)
                                meshhdrlen =
                                        ieee80211_new_mesh_header(&mesh_hdr,
                                                        sdata,
                                                        skb->data + ETH_ALEN,
                                                        NULL);
                        else
                                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) {
                                ret = NETDEV_TX_OK;
                                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:
                ret = NETDEV_TX_OK;
                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(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 >= 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 (unlikely(!ieee80211_vif_is_mesh(&sdata->vif) &&
                     !is_multicast_ether_addr(hdr.addr1) && !authorized &&
                     (cpu_to_be16(ethertype) != sdata->control_port_protocol ||
                      compare_ether_addr(sdata->vif.addr, skb->data + ETH_ALEN)))) {
#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 = NETDEV_TX_OK;
                goto fail;
        }

        /*
         * If the skb is shared we need to obtain our own copy.
         */
        if (skb_shared(skb)) {
                tmp_skb = skb;
                skb = skb_clone(skb, GFP_ATOMIC);
                kfree_skb(tmp_skb);

                if (!skb) {
                        ret = NETDEV_TX_OK;
                        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))
                        goto fail;
        }

        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;
        ieee80211_xmit(sdata, skb);

        return NETDEV_TX_OK;

 fail:
        if (ret == NETDEV_TX_OK)
                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;

        for (i = 0; i < local->hw.queues; i++)
                skb_queue_purge(&local->pending[i]);
}

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

                result = __ieee80211_tx(local, &skb, 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;
        struct ieee80211_sub_if_data *sdata;
        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)) {
                                kfree_skb(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]))
                        list_for_each_entry_rcu(sdata, &local->interfaces, list)
                                netif_wake_subqueue(sdata->dev, 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_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;

        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 */
                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_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;
        struct ieee80211_supported_band *sband;
        enum ieee80211_band band = local->hw.conf.channel->band;
        struct ieee80211_tx_rate_control txrc;

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

        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(ap, skb, beacon);
                        } else {
                                unsigned long flags;

                                spin_lock_irqsave(&local->sta_lock, flags);
                                ieee80211_beacon_add_tim(ap, skb, beacon);
                                spin_unlock_irqrestore(&local->sta_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;
                u8 *pos;

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

                /* headroom, head length, tail length and maximum TIM length */
                skb = dev_alloc_skb(local->tx_headroom + 400 +
                                sdata->u.mesh.ie_len);
                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->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->vif, skb) ||
                    mesh_add_ds_params_ie(skb, sdata) ||
                    ieee80211_add_ext_srates_ie(&sdata->vif, skb) ||
                    mesh_add_rsn_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 = sband;
        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 << sband->n_bitrates) - 1)
                txrc.max_rate_idx = -1;
        else
                txrc.max_rate_idx = fls(txrc.rate_idx_mask) - 1;
        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_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);
        memset(hdr->addr1, 0xff, ETH_ALEN);
        memcpy(hdr->addr2, vif->addr, ETH_ALEN);
        memset(hdr->addr3, 0xff, ETH_ALEN);

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

void ieee80211_tx_skb(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
{
        skb_set_mac_header(skb, 0);
        skb_set_network_header(skb, 0);
        skb_set_transport_header(skb, 0);

        /* Send all internal mgmt frames on VO. Accordingly set TID to 7. */
        skb_set_queue_mapping(skb, IEEE80211_AC_VO);
        skb->priority = 7;

        /*
         * 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();
}