/*
 * HT handling
 *
 * Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
 * Copyright 2007, Michael Wu <flamingice@sourmilk.net>
 * Copyright 2007-2009, Intel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/ieee80211.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
#include "wme.h"

/**
 * DOC: TX aggregation
 *
 * Aggregation on the TX side requires setting the hardware flag
 * %IEEE80211_HW_AMPDU_AGGREGATION as well as, if present, the @ampdu_queues
 * hardware parameter to the number of hardware AMPDU queues. If there are no
 * hardware queues then the driver will (currently) have to do all frame
 * buffering.
 *
 * When TX aggregation is started by some subsystem (usually the rate control
 * algorithm would be appropriate) by calling the
 * ieee80211_start_tx_ba_session() function, the driver will be notified via
 * its @ampdu_action function, with the %IEEE80211_AMPDU_TX_START action.
 *
 * In response to that, the driver is later required to call the
 * ieee80211_start_tx_ba_cb() (or ieee80211_start_tx_ba_cb_irqsafe())
 * function, which will start the aggregation session.
 *
 * Similarly, when the aggregation session is stopped by
 * ieee80211_stop_tx_ba_session(), the driver's @ampdu_action function will
 * be called with the action %IEEE80211_AMPDU_TX_STOP. In this case, the
 * call must not fail, and the driver must later call ieee80211_stop_tx_ba_cb()
 * (or ieee80211_stop_tx_ba_cb_irqsafe()).
 */

static void ieee80211_send_addba_request(struct ieee80211_sub_if_data *sdata,
                                         const u8 *da, u16 tid,
                                         u8 dialog_token, u16 start_seq_num,
                                         u16 agg_size, u16 timeout)
{
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        struct ieee80211_mgmt *mgmt;
        u16 capab;

        skb = dev_alloc_skb(sizeof(*mgmt) + local->hw.extra_tx_headroom);

        if (!skb) {
                printk(KERN_ERR "%s: failed to allocate buffer "
                                "for addba request frame\n", sdata->dev->name);
                return;
        }
        skb_reserve(skb, local->hw.extra_tx_headroom);
        mgmt = (struct ieee80211_mgmt *) skb_put(skb, 24);
        memset(mgmt, 0, 24);
        memcpy(mgmt->da, da, ETH_ALEN);
        memcpy(mgmt->sa, sdata->dev->dev_addr, ETH_ALEN);
        if (sdata->vif.type == NL80211_IFTYPE_AP ||
            sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                memcpy(mgmt->bssid, sdata->dev->dev_addr, ETH_ALEN);
        else if (sdata->vif.type == NL80211_IFTYPE_STATION)
                memcpy(mgmt->bssid, sdata->u.mgd.bssid, ETH_ALEN);

        mgmt->frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
                                          IEEE80211_STYPE_ACTION);

        skb_put(skb, 1 + sizeof(mgmt->u.action.u.addba_req));

        mgmt->u.action.category = WLAN_CATEGORY_BACK;
        mgmt->u.action.u.addba_req.action_code = WLAN_ACTION_ADDBA_REQ;

        mgmt->u.action.u.addba_req.dialog_token = dialog_token;
        capab = (u16)(1 << 1);          /* bit 1 aggregation policy */
        capab |= (u16)(tid << 2);       /* bit 5:2 TID number */
        capab |= (u16)(agg_size << 6);  /* bit 15:6 max size of aggergation */

        mgmt->u.action.u.addba_req.capab = cpu_to_le16(capab);

        mgmt->u.action.u.addba_req.timeout = cpu_to_le16(timeout);
        mgmt->u.action.u.addba_req.start_seq_num =
                                        cpu_to_le16(start_seq_num << 4);

        ieee80211_tx_skb(sdata, skb, 1);
}

void ieee80211_send_bar(struct ieee80211_sub_if_data *sdata, u8 *ra, u16 tid, u16 ssn)
{
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        struct ieee80211_bar *bar;
        u16 bar_control = 0;

        skb = dev_alloc_skb(sizeof(*bar) + local->hw.extra_tx_headroom);
        if (!skb) {
                printk(KERN_ERR "%s: failed to allocate buffer for "
                        "bar frame\n", sdata->dev->name);
                return;
        }
        skb_reserve(skb, local->hw.extra_tx_headroom);
        bar = (struct ieee80211_bar *)skb_put(skb, sizeof(*bar));
        memset(bar, 0, sizeof(*bar));
        bar->frame_control = cpu_to_le16(IEEE80211_FTYPE_CTL |
                                         IEEE80211_STYPE_BACK_REQ);
        memcpy(bar->ra, ra, ETH_ALEN);
        memcpy(bar->ta, sdata->dev->dev_addr, ETH_ALEN);
        bar_control |= (u16)IEEE80211_BAR_CTRL_ACK_POLICY_NORMAL;
        bar_control |= (u16)IEEE80211_BAR_CTRL_CBMTID_COMPRESSED_BA;
        bar_control |= (u16)(tid << 12);
        bar->control = cpu_to_le16(bar_control);
        bar->start_seq_num = cpu_to_le16(ssn);

        ieee80211_tx_skb(sdata, skb, 0);
}

int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
                                    enum ieee80211_back_parties initiator)
{
        struct ieee80211_local *local = sta->local;
        int ret;
        u8 *state;

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "Tx BA session stop requested for %pM tid %u\n",
               sta->sta.addr, tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */

        state = &sta->ampdu_mlme.tid_state_tx[tid];

        if (*state == HT_AGG_STATE_OPERATIONAL)
                sta->ampdu_mlme.addba_req_num[tid] = 0;

        *state = HT_AGG_STATE_REQ_STOP_BA_MSK |
                (initiator << HT_AGG_STATE_INITIATOR_SHIFT);

        ret = drv_ampdu_action(local, IEEE80211_AMPDU_TX_STOP,
                               &sta->sta, tid, NULL);

        /* HW shall not deny going back to legacy */
        if (WARN_ON(ret)) {
                /*
                 * We may have pending packets get stuck in this case...
                 * Not bothering with a workaround for now.
                 */
        }

        return ret;
}

/*
 * After sending add Block Ack request we activated a timer until
 * add Block Ack response will arrive from the recipient.
 * If this timer expires sta_addba_resp_timer_expired will be executed.
 */
static void sta_addba_resp_timer_expired(unsigned long data)
{
        /* not an elegant detour, but there is no choice as the timer passes
         * only one argument, and both sta_info and TID are needed, so init
         * flow in sta_info_create gives the TID as data, while the timer_to_id
         * array gives the sta through container_of */
        u16 tid = *(u8 *)data;
        struct sta_info *sta = container_of((void *)data,
                struct sta_info, timer_to_tid[tid]);
        u8 *state;

        state = &sta->ampdu_mlme.tid_state_tx[tid];

        /* check if the TID waits for addBA response */
        spin_lock_bh(&sta->lock);
        if ((*state & (HT_ADDBA_REQUESTED_MSK | HT_ADDBA_RECEIVED_MSK)) !=
                                                HT_ADDBA_REQUESTED_MSK) {
                spin_unlock_bh(&sta->lock);
                *state = HT_AGG_STATE_IDLE;
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "timer expired on tid %d but we are not "
                                "(or no longer) expecting addBA response there",
                        tid);
#endif
                return;
        }

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "addBA response timer expired on tid %d\n", tid);
#endif

        ___ieee80211_stop_tx_ba_session(sta, tid, WLAN_BACK_INITIATOR);
        spin_unlock_bh(&sta->lock);
}

static inline int ieee80211_ac_from_tid(int tid)
{
        return ieee802_1d_to_ac[tid & 7];
}

int ieee80211_start_tx_ba_session(struct ieee80211_hw *hw, u8 *ra, u16 tid)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sta_info *sta;
        struct ieee80211_sub_if_data *sdata;
        u8 *state;
        int ret = 0;
        u16 start_seq_num;

        if (WARN_ON(!local->ops->ampdu_action))
                return -EINVAL;

        if ((tid >= STA_TID_NUM) || !(hw->flags & IEEE80211_HW_AMPDU_AGGREGATION))
                return -EINVAL;

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "Open BA session requested for %pM tid %u\n",
               ra, tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */

        rcu_read_lock();

        sta = sta_info_get(local, ra);
        if (!sta) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Could not find the station\n");
#endif
                ret = -ENOENT;
                goto unlock;
        }

        /*
         * The aggregation code is not prepared to handle
         * anything but STA/AP due to the BSSID handling.
         * IBSS could work in the code but isn't supported
         * by drivers or the standard.
         */
        if (sta->sdata->vif.type != NL80211_IFTYPE_STATION &&
            sta->sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
            sta->sdata->vif.type != NL80211_IFTYPE_AP) {
                ret = -EINVAL;
                goto unlock;
        }

        if (test_sta_flags(sta, WLAN_STA_SUSPEND)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Suspend in progress. "
                       "Denying BA session request\n");
#endif
                ret = -EINVAL;
                goto unlock;
        }

        spin_lock_bh(&sta->lock);
        spin_lock(&local->ampdu_lock);

        sdata = sta->sdata;

        /* we have tried too many times, receiver does not want A-MPDU */
        if (sta->ampdu_mlme.addba_req_num[tid] > HT_AGG_MAX_RETRIES) {
                ret = -EBUSY;
                goto err_unlock_sta;
        }

        state = &sta->ampdu_mlme.tid_state_tx[tid];
        /* check if the TID is not in aggregation flow already */
        if (*state != HT_AGG_STATE_IDLE) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "BA request denied - session is not "
                                 "idle on tid %u\n", tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */
                ret = -EAGAIN;
                goto err_unlock_sta;
        }

        /*
         * While we're asking the driver about the aggregation,
         * stop the AC queue so that we don't have to worry
         * about frames that came in while we were doing that,
         * which would require us to put them to the AC pending
         * afterwards which just makes the code more complex.
         */
        ieee80211_stop_queue_by_reason(
                &local->hw, ieee80211_ac_from_tid(tid),
                IEEE80211_QUEUE_STOP_REASON_AGGREGATION);

        /* prepare A-MPDU MLME for Tx aggregation */
        sta->ampdu_mlme.tid_tx[tid] =
                        kmalloc(sizeof(struct tid_ampdu_tx), GFP_ATOMIC);
        if (!sta->ampdu_mlme.tid_tx[tid]) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                if (net_ratelimit())
                        printk(KERN_ERR "allocate tx mlme to tid %d failed\n",
                                        tid);
#endif
                ret = -ENOMEM;
                goto err_wake_queue;
        }

        skb_queue_head_init(&sta->ampdu_mlme.tid_tx[tid]->pending);

        /* Tx timer */
        sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.function =
                        sta_addba_resp_timer_expired;
        sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.data =
                        (unsigned long)&sta->timer_to_tid[tid];
        init_timer(&sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer);

        /* Ok, the Addba frame hasn't been sent yet, but if the driver calls the
         * call back right away, it must see that the flow has begun */
        *state |= HT_ADDBA_REQUESTED_MSK;

        start_seq_num = sta->tid_seq[tid];

        ret = drv_ampdu_action(local, IEEE80211_AMPDU_TX_START,
                               &sta->sta, tid, &start_seq_num);

        if (ret) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "BA request denied - HW unavailable for"
                                        " tid %d\n", tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */
                *state = HT_AGG_STATE_IDLE;
                goto err_free;
        }

        /* Driver vetoed or OKed, but we can take packets again now */
        ieee80211_wake_queue_by_reason(
                &local->hw, ieee80211_ac_from_tid(tid),
                IEEE80211_QUEUE_STOP_REASON_AGGREGATION);

        spin_unlock(&local->ampdu_lock);
        spin_unlock_bh(&sta->lock);

        /* send an addBA request */
        sta->ampdu_mlme.dialog_token_allocator++;
        sta->ampdu_mlme.tid_tx[tid]->dialog_token =
                        sta->ampdu_mlme.dialog_token_allocator;
        sta->ampdu_mlme.tid_tx[tid]->ssn = start_seq_num;

        ieee80211_send_addba_request(sta->sdata, ra, tid,
                         sta->ampdu_mlme.tid_tx[tid]->dialog_token,
                         sta->ampdu_mlme.tid_tx[tid]->ssn,
                         0x40, 5000);
        sta->ampdu_mlme.addba_req_num[tid]++;
        /* activate the timer for the recipient's addBA response */
        sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer.expires =
                                jiffies + ADDBA_RESP_INTERVAL;
        add_timer(&sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer);
#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "activated addBA response timer on tid %d\n", tid);
#endif
        goto unlock;

 err_free:
        kfree(sta->ampdu_mlme.tid_tx[tid]);
        sta->ampdu_mlme.tid_tx[tid] = NULL;
 err_wake_queue:
        ieee80211_wake_queue_by_reason(
                &local->hw, ieee80211_ac_from_tid(tid),
                IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
 err_unlock_sta:
        spin_unlock(&local->ampdu_lock);
        spin_unlock_bh(&sta->lock);
 unlock:
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL(ieee80211_start_tx_ba_session);

/*
 * splice packets from the STA's pending to the local pending,
 * requires a call to ieee80211_agg_splice_finish and holding
 * local->ampdu_lock across both calls.
 */
static void ieee80211_agg_splice_packets(struct ieee80211_local *local,
                                         struct sta_info *sta, u16 tid)
{
        unsigned long flags;
        u16 queue = ieee80211_ac_from_tid(tid);

        ieee80211_stop_queue_by_reason(
                &local->hw, queue,
                IEEE80211_QUEUE_STOP_REASON_AGGREGATION);

        if (!(sta->ampdu_mlme.tid_state_tx[tid] & HT_ADDBA_REQUESTED_MSK))
                return;

        if (WARN(!sta->ampdu_mlme.tid_tx[tid],
                 "TID %d gone but expected when splicing aggregates from"
                 "the pending queue\n", tid))
                return;

        if (!skb_queue_empty(&sta->ampdu_mlme.tid_tx[tid]->pending)) {
                spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
                /* copy over remaining packets */
                skb_queue_splice_tail_init(
                        &sta->ampdu_mlme.tid_tx[tid]->pending,
                        &local->pending[queue]);
                spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
        }
}

static void ieee80211_agg_splice_finish(struct ieee80211_local *local,
                                        struct sta_info *sta, u16 tid)
{
        u16 queue = ieee80211_ac_from_tid(tid);

        ieee80211_wake_queue_by_reason(
                &local->hw, queue,
                IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
}

/* caller must hold sta->lock */
static void ieee80211_agg_tx_operational(struct ieee80211_local *local,
                                         struct sta_info *sta, u16 tid)
{
#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "Aggregation is on for tid %d \n", tid);
#endif

        spin_lock(&local->ampdu_lock);
        ieee80211_agg_splice_packets(local, sta, tid);
        /*
         * NB: we rely on sta->lock being taken in the TX
         * processing here when adding to the pending queue,
         * otherwise we could only change the state of the
         * session to OPERATIONAL _here_.
         */
        ieee80211_agg_splice_finish(local, sta, tid);
        spin_unlock(&local->ampdu_lock);

        drv_ampdu_action(local, IEEE80211_AMPDU_TX_OPERATIONAL,
                         &sta->sta, tid, NULL);
}

void ieee80211_start_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u16 tid)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sta_info *sta;
        u8 *state;

        if (tid >= STA_TID_NUM) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Bad TID value: tid = %d (>= %d)\n",
                                tid, STA_TID_NUM);
#endif
                return;
        }

        rcu_read_lock();
        sta = sta_info_get(local, ra);
        if (!sta) {
                rcu_read_unlock();
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Could not find station: %pM\n", ra);
#endif
                return;
        }

        state = &sta->ampdu_mlme.tid_state_tx[tid];
        spin_lock_bh(&sta->lock);

        if (WARN_ON(!(*state & HT_ADDBA_REQUESTED_MSK))) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "addBA was not requested yet, state is %d\n",
                                *state);
#endif
                spin_unlock_bh(&sta->lock);
                rcu_read_unlock();
                return;
        }

        if (WARN_ON(*state & HT_ADDBA_DRV_READY_MSK))
                goto out;

        *state |= HT_ADDBA_DRV_READY_MSK;

        if (*state == HT_AGG_STATE_OPERATIONAL)
                ieee80211_agg_tx_operational(local, sta, tid);

 out:
        spin_unlock_bh(&sta->lock);
        rcu_read_unlock();
}
EXPORT_SYMBOL(ieee80211_start_tx_ba_cb);

void ieee80211_start_tx_ba_cb_irqsafe(struct ieee80211_hw *hw,
                                      const u8 *ra, u16 tid)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct ieee80211_ra_tid *ra_tid;
        struct sk_buff *skb = dev_alloc_skb(0);

        if (unlikely(!skb)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                if (net_ratelimit())
                        printk(KERN_WARNING "%s: Not enough memory, "
                               "dropping start BA session", skb->dev->name);
#endif
                return;
        }
        ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
        memcpy(&ra_tid->ra, ra, ETH_ALEN);
        ra_tid->tid = tid;

        skb->pkt_type = IEEE80211_ADDBA_MSG;
        skb_queue_tail(&local->skb_queue, skb);
        tasklet_schedule(&local->tasklet);
}
EXPORT_SYMBOL(ieee80211_start_tx_ba_cb_irqsafe);

int __ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
                                   enum ieee80211_back_parties initiator)
{
        u8 *state;
        int ret;

        /* check if the TID is in aggregation */
        state = &sta->ampdu_mlme.tid_state_tx[tid];
        spin_lock_bh(&sta->lock);

        if (*state != HT_AGG_STATE_OPERATIONAL) {
                ret = -ENOENT;
                goto unlock;
        }

        ret = ___ieee80211_stop_tx_ba_session(sta, tid, initiator);

 unlock:
        spin_unlock_bh(&sta->lock);
        return ret;
}

int ieee80211_stop_tx_ba_session(struct ieee80211_hw *hw,
                                 u8 *ra, u16 tid,
                                 enum ieee80211_back_parties initiator)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sta_info *sta;
        int ret = 0;

        if (!local->ops->ampdu_action)
                return -EINVAL;

        if (tid >= STA_TID_NUM)
                return -EINVAL;

        rcu_read_lock();
        sta = sta_info_get(local, ra);
        if (!sta) {
                rcu_read_unlock();
                return -ENOENT;
        }

        ret = __ieee80211_stop_tx_ba_session(sta, tid, initiator);
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL(ieee80211_stop_tx_ba_session);

void ieee80211_stop_tx_ba_cb(struct ieee80211_hw *hw, u8 *ra, u8 tid)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct sta_info *sta;
        u8 *state;

        if (tid >= STA_TID_NUM) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Bad TID value: tid = %d (>= %d)\n",
                                tid, STA_TID_NUM);
#endif
                return;
        }

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "Stopping Tx BA session for %pM tid %d\n",
               ra, tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */

        rcu_read_lock();
        sta = sta_info_get(local, ra);
        if (!sta) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Could not find station: %pM\n", ra);
#endif
                rcu_read_unlock();
                return;
        }
        state = &sta->ampdu_mlme.tid_state_tx[tid];

        /* NOTE: no need to use sta->lock in this state check, as
         * ieee80211_stop_tx_ba_session will let only one stop call to
         * pass through per sta/tid
         */
        if ((*state & HT_AGG_STATE_REQ_STOP_BA_MSK) == 0) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "unexpected callback to A-MPDU stop\n");
#endif
                rcu_read_unlock();
                return;
        }

        if (*state & HT_AGG_STATE_INITIATOR_MSK)
                ieee80211_send_delba(sta->sdata, ra, tid,
                        WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);

        spin_lock_bh(&sta->lock);
        spin_lock(&local->ampdu_lock);

        ieee80211_agg_splice_packets(local, sta, tid);

        *state = HT_AGG_STATE_IDLE;
        /* from now on packets are no longer put onto sta->pending */
        kfree(sta->ampdu_mlme.tid_tx[tid]);
        sta->ampdu_mlme.tid_tx[tid] = NULL;

        ieee80211_agg_splice_finish(local, sta, tid);

        spin_unlock(&local->ampdu_lock);
        spin_unlock_bh(&sta->lock);

        rcu_read_unlock();
}
EXPORT_SYMBOL(ieee80211_stop_tx_ba_cb);

void ieee80211_stop_tx_ba_cb_irqsafe(struct ieee80211_hw *hw,
                                     const u8 *ra, u16 tid)
{
        struct ieee80211_local *local = hw_to_local(hw);
        struct ieee80211_ra_tid *ra_tid;
        struct sk_buff *skb = dev_alloc_skb(0);

        if (unlikely(!skb)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                if (net_ratelimit())
                        printk(KERN_WARNING "%s: Not enough memory, "
                               "dropping stop BA session", skb->dev->name);
#endif
                return;
        }
        ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
        memcpy(&ra_tid->ra, ra, ETH_ALEN);
        ra_tid->tid = tid;

        skb->pkt_type = IEEE80211_DELBA_MSG;
        skb_queue_tail(&local->skb_queue, skb);
        tasklet_schedule(&local->tasklet);
}
EXPORT_SYMBOL(ieee80211_stop_tx_ba_cb_irqsafe);


void ieee80211_process_addba_resp(struct ieee80211_local *local,
                                  struct sta_info *sta,
                                  struct ieee80211_mgmt *mgmt,
                                  size_t len)
{
        u16 capab, tid;
        u8 *state;

        capab = le16_to_cpu(mgmt->u.action.u.addba_resp.capab);
        tid = (capab & IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;

        state = &sta->ampdu_mlme.tid_state_tx[tid];

        spin_lock_bh(&sta->lock);

        if (!(*state & HT_ADDBA_REQUESTED_MSK))
                goto out;

        if (mgmt->u.action.u.addba_resp.dialog_token !=
                sta->ampdu_mlme.tid_tx[tid]->dialog_token) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "wrong addBA response token, tid %d\n", tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */
                goto out;
        }

        del_timer(&sta->ampdu_mlme.tid_tx[tid]->addba_resp_timer);

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "switched off addBA timer for tid %d \n", tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */

        if (le16_to_cpu(mgmt->u.action.u.addba_resp.status)
                        == WLAN_STATUS_SUCCESS) {
                u8 curstate = *state;

                *state |= HT_ADDBA_RECEIVED_MSK;

                if (*state != curstate && *state == HT_AGG_STATE_OPERATIONAL)
                        ieee80211_agg_tx_operational(local, sta, tid);

                sta->ampdu_mlme.addba_req_num[tid] = 0;
        } else {
                ___ieee80211_stop_tx_ba_session(sta, tid, WLAN_BACK_INITIATOR);
        }

 out:
        spin_unlock_bh(&sta->lock);
}