agg-tx.c

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/*
 * 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 2007-2010, 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 <linux/slab.h>
#include <linux/export.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
#include "wme.h"

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)
                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->vif.addr, ETH_ALEN);
        if (sdata->vif.type == NL80211_IFTYPE_AP ||
            sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                memcpy(mgmt->bssid, sdata->vif.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);
}

void ieee80211_send_bar(struct ieee80211_vif *vif, u8 *ra, u16 tid, u16 ssn)
{
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
        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)
                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->vif.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 << IEEE80211_BAR_CTRL_TID_INFO_SHIFT);
        bar->control = cpu_to_le16(bar_control);
        bar->start_seq_num = cpu_to_le16(ssn);

        IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_INTFL_DONT_ENCRYPT;
        ieee80211_tx_skb(sdata, skb);
}
EXPORT_SYMBOL(ieee80211_send_bar);

void ieee80211_assign_tid_tx(struct sta_info *sta, int tid,
                             struct tid_ampdu_tx *tid_tx)
{
        lockdep_assert_held(&sta->ampdu_mlme.mtx);
        lockdep_assert_held(&sta->lock);
        rcu_assign_pointer(sta->ampdu_mlme.tid_tx[tid], tid_tx);
}

int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
                                    enum ieee80211_back_parties initiator,
                                    bool tx)
{
        struct ieee80211_local *local = sta->local;
        struct tid_ampdu_tx *tid_tx;
        int ret;

        lockdep_assert_held(&sta->ampdu_mlme.mtx);

        spin_lock_bh(&sta->lock);

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
        if (!tid_tx) {
                spin_unlock_bh(&sta->lock);
                return -ENOENT;
        }

        /* if we're already stopping ignore any new requests to stop */
        if (test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
                spin_unlock_bh(&sta->lock);
                return -EALREADY;
        }

        if (test_bit(HT_AGG_STATE_WANT_START, &tid_tx->state)) {
                /* not even started yet! */
                ieee80211_assign_tid_tx(sta, tid, NULL);
                spin_unlock_bh(&sta->lock);
                kfree_rcu(tid_tx, rcu_head);
                return 0;
        }

        set_bit(HT_AGG_STATE_STOPPING, &tid_tx->state);

        spin_unlock_bh(&sta->lock);

#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 */

        del_timer_sync(&tid_tx->addba_resp_timer);

        /*
         * After this packets are no longer handed right through
         * to the driver but are put onto tid_tx->pending instead,
         * with locking to ensure proper access.
         */
        clear_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state);

        /*
         * There might be a few packets being processed right now (on
         * another CPU) that have already gotten past the aggregation
         * check when it was still OPERATIONAL and consequently have
         * IEEE80211_TX_CTL_AMPDU set. In that case, this code might
         * call into the driver at the same time or even before the
         * TX paths calls into it, which could confuse the driver.
         *
         * Wait for all currently running TX paths to finish before
         * telling the driver. New packets will not go through since
         * the aggregation session is no longer OPERATIONAL.
         */
        synchronize_net();

        tid_tx->stop_initiator = initiator;
        tid_tx->tx_stop = tx;

        ret = drv_ampdu_action(local, sta->sdata,
                               IEEE80211_AMPDU_TX_STOP,
                               &sta->sta, tid, NULL, 0);

        /* 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]);
        struct tid_ampdu_tx *tid_tx;

        /* check if the TID waits for addBA response */
        rcu_read_lock();
        tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[tid]);
        if (!tid_tx ||
            test_bit(HT_AGG_STATE_RESPONSE_RECEIVED, &tid_tx->state)) {
                rcu_read_unlock();
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "timer expired on tid %d but we are not "
                                "(or no longer) expecting addBA response there\n",
                        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->sta, tid);
        rcu_read_unlock();
}

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

/*
 * When multiple aggregation sessions on multiple stations
 * are being created/destroyed simultaneously, we need to
 * refcount the global queue stop caused by that in order
 * to not get into a situation where one of the aggregation
 * setup or teardown re-enables queues before the other is
 * ready to handle that.
 *
 * These two functions take care of this issue by keeping
 * a global "agg_queue_stop" refcount.
 */
static void __acquires(agg_queue)
ieee80211_stop_queue_agg(struct ieee80211_local *local, int tid)
{
        int queue = ieee80211_ac_from_tid(tid);

        if (atomic_inc_return(&local->agg_queue_stop[queue]) == 1)
                ieee80211_stop_queue_by_reason(
                        &local->hw, queue,
                        IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
        __acquire(agg_queue);
}

static void __releases(agg_queue)
ieee80211_wake_queue_agg(struct ieee80211_local *local, int tid)
{
        int queue = ieee80211_ac_from_tid(tid);

        if (atomic_dec_return(&local->agg_queue_stop[queue]) == 0)
                ieee80211_wake_queue_by_reason(
                        &local->hw, queue,
                        IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
        __release(agg_queue);
}

/*
 * splice packets from the STA's pending to the local pending,
 * requires a call to ieee80211_agg_splice_finish later
 */
static void __acquires(agg_queue)
ieee80211_agg_splice_packets(struct ieee80211_local *local,
                             struct tid_ampdu_tx *tid_tx, u16 tid)
{
        int queue = ieee80211_ac_from_tid(tid);
        unsigned long flags;

        ieee80211_stop_queue_agg(local, tid);

        if (WARN(!tid_tx, "TID %d gone but expected when splicing aggregates"
                          " from the pending queue\n", tid))
                return;

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

static void __releases(agg_queue)
ieee80211_agg_splice_finish(struct ieee80211_local *local, u16 tid)
{
        ieee80211_wake_queue_agg(local, tid);
}

void ieee80211_tx_ba_session_handle_start(struct sta_info *sta, int tid)
{
        struct tid_ampdu_tx *tid_tx;
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        u16 start_seq_num;
        int ret;

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

        /*
         * Start queuing up packets for this aggregation session.
         * We're going to release them once the driver is OK with
         * that.
         */
        clear_bit(HT_AGG_STATE_WANT_START, &tid_tx->state);

        /*
         * Make sure no packets are being processed. This ensures that
         * we have a valid starting sequence number and that in-flight
         * packets have been flushed out and no packets for this TID
         * will go into the driver during the ampdu_action call.
         */
        synchronize_net();

        start_seq_num = sta->tid_seq[tid] >> 4;

        ret = drv_ampdu_action(local, sdata, IEEE80211_AMPDU_TX_START,
                               &sta->sta, tid, &start_seq_num, 0);
        if (ret) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "BA request denied - HW unavailable for"
                                        " tid %d\n", tid);
#endif
                spin_lock_bh(&sta->lock);
                ieee80211_agg_splice_packets(local, tid_tx, tid);
                ieee80211_assign_tid_tx(sta, tid, NULL);
                ieee80211_agg_splice_finish(local, tid);
                spin_unlock_bh(&sta->lock);

                kfree_rcu(tid_tx, rcu_head);
                return;
        }

        /* activate the timer for the recipient's addBA response */
        mod_timer(&tid_tx->addba_resp_timer, jiffies + ADDBA_RESP_INTERVAL);
#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "activated addBA response timer on tid %d\n", tid);
#endif

        spin_lock_bh(&sta->lock);
        sta->ampdu_mlme.addba_req_num[tid]++;
        spin_unlock_bh(&sta->lock);

        /* send AddBA request */
        ieee80211_send_addba_request(sdata, sta->sta.addr, tid,
                                     tid_tx->dialog_token, start_seq_num,
                                     local->hw.max_tx_aggregation_subframes,
                                     tid_tx->timeout);
}

int ieee80211_start_tx_ba_session(struct ieee80211_sta *pubsta, u16 tid,
                                  u16 timeout)
{
        struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct ieee80211_local *local = sdata->local;
        struct tid_ampdu_tx *tid_tx;
        int ret = 0;

        trace_api_start_tx_ba_session(pubsta, tid);

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

        if ((tid >= STA_TID_NUM) ||
            !(local->hw.flags & IEEE80211_HW_AMPDU_AGGREGATION) ||
            (local->hw.flags & IEEE80211_HW_TX_AMPDU_SETUP_IN_HW))
                return -EINVAL;

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

        /*
         * 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 (sdata->vif.type != NL80211_IFTYPE_STATION &&
            sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
            sdata->vif.type != NL80211_IFTYPE_AP)
                return -EINVAL;

        if (test_sta_flag(sta, WLAN_STA_BLOCK_BA)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "BA sessions blocked. "
                       "Denying BA session request\n");
#endif
                return -EINVAL;
        }

        spin_lock_bh(&sta->lock);

        /* 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;
        }

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
        /* check if the TID is not in aggregation flow already */
        if (tid_tx || sta->ampdu_mlme.tid_start_tx[tid]) {
#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;
        }

        /* prepare A-MPDU MLME for Tx aggregation */
        tid_tx = kzalloc(sizeof(struct tid_ampdu_tx), GFP_ATOMIC);
        if (!tid_tx) {
                ret = -ENOMEM;
                goto err_unlock_sta;
        }

        skb_queue_head_init(&tid_tx->pending);
        __set_bit(HT_AGG_STATE_WANT_START, &tid_tx->state);

        tid_tx->timeout = timeout;

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

        /* assign a dialog token */
        sta->ampdu_mlme.dialog_token_allocator++;
        tid_tx->dialog_token = sta->ampdu_mlme.dialog_token_allocator;

        /*
         * Finally, assign it to the start array; the work item will
         * collect it and move it to the normal array.
         */
        sta->ampdu_mlme.tid_start_tx[tid] = tid_tx;

        ieee80211_queue_work(&local->hw, &sta->ampdu_mlme.work);

        /* this flow continues off the work */
 err_unlock_sta:
        spin_unlock_bh(&sta->lock);
        return ret;
}
EXPORT_SYMBOL(ieee80211_start_tx_ba_session);

static void ieee80211_agg_tx_operational(struct ieee80211_local *local,
                                         struct sta_info *sta, u16 tid)
{
        struct tid_ampdu_tx *tid_tx;

        lockdep_assert_held(&sta->ampdu_mlme.mtx);

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "Aggregation is on for tid %d\n", tid);
#endif

        drv_ampdu_action(local, sta->sdata,
                         IEEE80211_AMPDU_TX_OPERATIONAL,
                         &sta->sta, tid, NULL, tid_tx->buf_size);

        /*
         * synchronize with TX path, while splicing the TX path
         * should block so it won't put more packets onto pending.
         */
        spin_lock_bh(&sta->lock);

        ieee80211_agg_splice_packets(local, tid_tx, tid);
        /*
         * Now mark as operational. This will be visible
         * in the TX path, and lets it go lock-free in
         * the common case.
         */
        set_bit(HT_AGG_STATE_OPERATIONAL, &tid_tx->state);
        ieee80211_agg_splice_finish(local, tid);

        spin_unlock_bh(&sta->lock);
}

void ieee80211_start_tx_ba_cb(struct ieee80211_vif *vif, u8 *ra, u16 tid)
{
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        struct tid_ampdu_tx *tid_tx;

        trace_api_start_tx_ba_cb(sdata, ra, tid);

        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;
        }

        mutex_lock(&local->sta_mtx);
        sta = sta_info_get(sdata, ra);
        if (!sta) {
                mutex_unlock(&local->sta_mtx);
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "Could not find station: %pM\n", ra);
#endif
                return;
        }

        mutex_lock(&sta->ampdu_mlme.mtx);
        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

        if (WARN_ON(!tid_tx)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "addBA was not requested!\n");
#endif
                goto unlock;
        }

        if (WARN_ON(test_and_set_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state)))
                goto unlock;

        if (test_bit(HT_AGG_STATE_RESPONSE_RECEIVED, &tid_tx->state))
                ieee80211_agg_tx_operational(local, sta, tid);

 unlock:
        mutex_unlock(&sta->ampdu_mlme.mtx);
        mutex_unlock(&local->sta_mtx);
}

void ieee80211_start_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
                                      const u8 *ra, u16 tid)
{
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_ra_tid *ra_tid;
        struct sk_buff *skb = dev_alloc_skb(0);

        if (unlikely(!skb))
                return;

        ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
        memcpy(&ra_tid->ra, ra, ETH_ALEN);
        ra_tid->tid = tid;

        skb->pkt_type = IEEE80211_SDATA_QUEUE_AGG_START;
        skb_queue_tail(&sdata->skb_queue, skb);
        ieee80211_queue_work(&local->hw, &sdata->work);
}
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,
                                   bool tx)
{
        int ret;

        mutex_lock(&sta->ampdu_mlme.mtx);

        ret = ___ieee80211_stop_tx_ba_session(sta, tid, initiator, tx);

        mutex_unlock(&sta->ampdu_mlme.mtx);

        return ret;
}

int ieee80211_stop_tx_ba_session(struct ieee80211_sta *pubsta, u16 tid)
{
        struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct ieee80211_local *local = sdata->local;
        struct tid_ampdu_tx *tid_tx;
        int ret = 0;

        trace_api_stop_tx_ba_session(pubsta, tid);

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

        if (tid >= STA_TID_NUM)
                return -EINVAL;

        spin_lock_bh(&sta->lock);
        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

        if (!tid_tx) {
                ret = -ENOENT;
                goto unlock;
        }

        if (test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
                /* already in progress stopping it */
                ret = 0;
                goto unlock;
        }

        set_bit(HT_AGG_STATE_WANT_STOP, &tid_tx->state);
        ieee80211_queue_work(&local->hw, &sta->ampdu_mlme.work);

 unlock:
        spin_unlock_bh(&sta->lock);
        return ret;
}
EXPORT_SYMBOL(ieee80211_stop_tx_ba_session);

void ieee80211_stop_tx_ba_cb(struct ieee80211_vif *vif, u8 *ra, u8 tid)
{
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        struct tid_ampdu_tx *tid_tx;

        trace_api_stop_tx_ba_cb(sdata, ra, tid);

        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 */

        mutex_lock(&local->sta_mtx);

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

        mutex_lock(&sta->ampdu_mlme.mtx);
        spin_lock_bh(&sta->lock);
        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

        if (!tid_tx || !test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG "unexpected callback to A-MPDU stop\n");
#endif
                goto unlock_sta;
        }

        if (tid_tx->stop_initiator == WLAN_BACK_INITIATOR && tid_tx->tx_stop)
                ieee80211_send_delba(sta->sdata, ra, tid,
                        WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);

        /*
         * When we get here, the TX path will not be lockless any more wrt.
         * aggregation, since the OPERATIONAL bit has long been cleared.
         * Thus it will block on getting the lock, if it occurs. So if we
         * stop the queue now, we will not get any more packets, and any
         * that might be being processed will wait for us here, thereby
         * guaranteeing that no packets go to the tid_tx pending queue any
         * more.
         */

        ieee80211_agg_splice_packets(local, tid_tx, tid);

        /* future packets must not find the tid_tx struct any more */
        ieee80211_assign_tid_tx(sta, tid, NULL);

        ieee80211_agg_splice_finish(local, tid);

        kfree_rcu(tid_tx, rcu_head);

 unlock_sta:
        spin_unlock_bh(&sta->lock);
        mutex_unlock(&sta->ampdu_mlme.mtx);
 unlock:
        mutex_unlock(&local->sta_mtx);
}

void ieee80211_stop_tx_ba_cb_irqsafe(struct ieee80211_vif *vif,
                                     const u8 *ra, u16 tid)
{
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_ra_tid *ra_tid;
        struct sk_buff *skb = dev_alloc_skb(0);

        if (unlikely(!skb))
                return;

        ra_tid = (struct ieee80211_ra_tid *) &skb->cb;
        memcpy(&ra_tid->ra, ra, ETH_ALEN);
        ra_tid->tid = tid;

        skb->pkt_type = IEEE80211_SDATA_QUEUE_AGG_STOP;
        skb_queue_tail(&sdata->skb_queue, skb);
        ieee80211_queue_work(&local->hw, &sdata->work);
}
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)
{
        struct tid_ampdu_tx *tid_tx;
        u16 capab, tid;
        u8 buf_size;

        capab = le16_to_cpu(mgmt->u.action.u.addba_resp.capab);
        tid = (capab & IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;
        buf_size = (capab & IEEE80211_ADDBA_PARAM_BUF_SIZE_MASK) >> 6;

        mutex_lock(&sta->ampdu_mlme.mtx);

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
        if (!tid_tx)
                goto out;

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

        del_timer_sync(&tid_tx->addba_resp_timer);

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

        /*
         * addba_resp_timer may have fired before we got here, and
         * caused WANT_STOP to be set. If the stop then was already
         * processed further, STOPPING might be set.
         */
        if (test_bit(HT_AGG_STATE_WANT_STOP, &tid_tx->state) ||
            test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
                printk(KERN_DEBUG
                       "got addBA resp for tid %d but we already gave up\n",
                       tid);
#endif
                goto out;
        }

        /*
         * IEEE 802.11-2007 7.3.1.14:
         * In an ADDBA Response frame, when the Status Code field
         * is set to 0, the Buffer Size subfield is set to a value
         * of at least 1.
         */
        if (le16_to_cpu(mgmt->u.action.u.addba_resp.status)
                        == WLAN_STATUS_SUCCESS && buf_size) {
                if (test_and_set_bit(HT_AGG_STATE_RESPONSE_RECEIVED,
                                     &tid_tx->state)) {
                        /* ignore duplicate response */
                        goto out;
                }

                tid_tx->buf_size = buf_size;

                if (test_bit(HT_AGG_STATE_DRV_READY, &tid_tx->state))
                        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,
                                                true);
        }

 out:
        mutex_unlock(&sta->ampdu_mlme.mtx);
}