C++ rcu_dereference_protected_tid_tx函数代码示例

static void ieee80211_remove_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);

	tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

	/*
	 * 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(sta->sdata, 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(sta->sdata, tid);

	kfree_rcu(tid_tx, rcu_head);
}

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_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);
}

/*
 * After accepting the AddBA Response we activated a timer,
 * resetting it after each frame that we send.
 */
static void sta_tx_agg_session_timer_expired(unsigned long data)
{
    /* not an elegant detour, but there is no choice as the timer passes
     * only one argument, and various sta_info are needed here, so init
     * flow in sta_info_create gives the TID as data, while the timer_to_id
     * array gives the sta through container_of */
    u8 *ptid = (u8 *)data;
    u8 *timer_to_id = ptid - *ptid;
    struct sta_info *sta = container_of(timer_to_id, struct sta_info,
                                        timer_to_tid[0]);
    struct tid_ampdu_tx *tid_tx;
    unsigned long timeout;

    tid_tx = rcu_dereference_protected_tid_tx(sta, *ptid);
    if (!tid_tx)
        return;

    timeout = tid_tx->last_tx + TU_TO_JIFFIES(tid_tx->timeout);
    if (time_is_after_jiffies(timeout)) {
        mod_timer(&tid_tx->session_timer, timeout);
        return;
    }

#ifdef CONFIG_MAC80211_HT_DEBUG
    printk(KERN_DEBUG "tx session timer expired on tid %d\n", (u16)*ptid);
#endif

    ieee80211_stop_tx_ba_session(&sta->sta, *ptid);
}

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(&tid_tx->addba_resp_timer);

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

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;
	bool send_delba = false;

	trace_api_stop_tx_ba_cb(sdata, ra, tid);

	if (tid >= IEEE80211_NUM_TIDS) {
		ht_dbg(sdata, "Bad TID value: tid = %d (>= %d)\n",
		       tid, IEEE80211_NUM_TIDS);
		return;
	}

	ht_dbg(sdata, "Stopping Tx BA session for %pM tid %d\n", ra, tid);

	mutex_lock(&local->sta_mtx);

	sta = sta_info_get_bss(sdata, ra);
	if (!sta) {
		ht_dbg(sdata, "Could not find station: %pM\n", ra);
		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)) {
		ht_dbg(sdata,
		       "unexpected callback to A-MPDU stop for %pM tid %d\n",
		       sta->sta.addr, tid);
		goto unlock_sta;
	}

	if (tid_tx->stop_initiator == WLAN_BACK_INITIATOR && tid_tx->tx_stop)
		send_delba = true;

	ieee80211_remove_tid_tx(sta, tid);

 unlock_sta:
	spin_unlock_bh(&sta->lock);

	if (send_delba)
		ieee80211_send_delba(sdata, ra, tid,
			WLAN_BACK_INITIATOR, WLAN_REASON_QSTA_NOT_USE);

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

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);
}

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 >= IEEE80211_NUM_TIDS)
		return -EINVAL;

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

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

	WARN(sta->reserved_tid == tid,
	     "Requested to stop BA session on reserved tid=%d", tid);

	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;
}

int ___ieee80211_stop_tx_ba_session(struct sta_info *sta, u16 tid,
				    enum ieee80211_agg_stop_reason reason)
{
	struct ieee80211_local *local = sta->local;
	struct tid_ampdu_tx *tid_tx;
	enum ieee80211_ampdu_mlme_action action;
	int ret;

	lockdep_assert_held(&sta->ampdu_mlme.mtx);

	switch (reason) {
	case AGG_STOP_DECLINED:
	case AGG_STOP_LOCAL_REQUEST:
	case AGG_STOP_PEER_REQUEST:
		action = IEEE80211_AMPDU_TX_STOP_CONT;
		break;
	case AGG_STOP_DESTROY_STA:
		action = IEEE80211_AMPDU_TX_STOP_FLUSH;
		break;
	default:
		WARN_ON_ONCE(1);
		return -EINVAL;
	}

	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
	 * unless we're destroying it in which case notify the driver
	 */
	if (test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
		spin_unlock_bh(&sta->lock);
		if (reason != AGG_STOP_DESTROY_STA)
			return -EALREADY;
		ret = drv_ampdu_action(local, sta->sdata,
				       IEEE80211_AMPDU_TX_STOP_FLUSH_CONT,
				       &sta->sta, tid, NULL, 0);
		WARN_ON_ONCE(ret);
		return 0;
	}

	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);

	ht_dbg(sta->sdata, "Tx BA session stop requested for %pM tid %u\n",
	       sta->sta.addr, tid);

	del_timer_sync(&tid_tx->addba_resp_timer);
	del_timer_sync(&tid_tx->session_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 = reason == AGG_STOP_PEER_REQUEST ?
					WLAN_BACK_RECIPIENT :
					WLAN_BACK_INITIATOR;
	tid_tx->tx_stop = reason == AGG_STOP_LOCAL_REQUEST;

	ret = drv_ampdu_action(local, sta->sdata, action,
			       &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.
		 */
//.........这里部分代码省略.........

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))
		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_flags(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) {
#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_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;
}

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;
}

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 */

    if (sdata->vif.type != NL80211_IFTYPE_STATION &&
            sdata->vif.type != NL80211_IFTYPE_MESH_POINT &&
            sdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
            sdata->vif.type != NL80211_IFTYPE_AP &&
            sdata->vif.type != NL80211_IFTYPE_ADHOC)
        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;
    }

    /*
     * 802.11n-2009 11.5.1.1: If the initiating STA is an HT STA, is a
     * member of an IBSS, and has no other existing Block Ack agreement
     * with the recipient STA, then the initiating STA shall transmit a
     * Probe Request frame to the recipient STA and shall not transmit an
     * ADDBA Request frame unless it receives a Probe Response frame
     * from the recipient within dot11ADDBAFailureTimeout.
     *
     * The probe request mechanism for ADDBA is currently not implemented,
     * but we only build up Block Ack session with HT STAs. This information
     * is set when we receive a bss info from a probe response or a beacon.
     */
    if (sta->sdata->vif.type == NL80211_IFTYPE_ADHOC &&
            !sta->sta.ht_cap.ht_supported) {
#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "BA request denied - IBSS STA %pM"
               "does not advertise HT support\n", pubsta->addr);
#endif /* CONFIG_MAC80211_HT_DEBUG */
        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;
    }

    /*
     * if we have tried more than HT_AGG_BURST_RETRIES times we
     * will spread our requests in time to avoid stalling connection
     * for too long
     */
    if (sta->ampdu_mlme.addba_req_num[tid] > HT_AGG_BURST_RETRIES &&
            time_before(jiffies, sta->ampdu_mlme.last_addba_req_time[tid] +
                        HT_AGG_RETRIES_PERIOD)) {
#ifdef CONFIG_MAC80211_HT_DEBUG
        printk(KERN_DEBUG "BA request denied - "
               "waiting a grace period after %d failed requests "
               "on tid %u\n",
               sta->ampdu_mlme.addba_req_num[tid], tid);
#endif /* CONFIG_MAC80211_HT_DEBUG */
        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) {
//.........这里部分代码省略.........

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) {
		ht_dbg(sta->sdata, "wrong addBA response token, %pM tid %d\n",
		       sta->sta.addr, tid);
		goto out;
	}

	del_timer_sync(&tid_tx->addba_resp_timer);

	ht_dbg(sta->sdata, "switched off addBA timer for %pM tid %d\n",
	       sta->sta.addr, tid);

	/*
	 * 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)) {
		ht_dbg(sta->sdata,
		       "got addBA resp for %pM tid %d but we already gave up\n",
		       sta->sta.addr, tid);
		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;

		if (tid_tx->timeout) {
			mod_timer(&tid_tx->session_timer,
				  TU_TO_EXP_TIME(tid_tx->timeout));
			tid_tx->last_tx = jiffies;
		}

	} else {
		___ieee80211_stop_tx_ba_session(sta, tid, AGG_STOP_DECLINED);
	}

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

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;
	struct ieee80211_ampdu_params params = {
		.sta = &sta->sta,
		.action = IEEE80211_AMPDU_TX_START,
		.tid = tid,
		.buf_size = 0,
		.amsdu = false,
		.timeout = 0,
	};
	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);

	ieee80211_agg_stop_txq(sta, tid);

	/*
	 * 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();

	params.ssn = sta->tid_seq[tid] >> 4;
	ret = drv_ampdu_action(local, sdata, &params);
	if (ret) {
		ht_dbg(sdata,
		       "BA request denied - HW unavailable for %pM tid %d\n",
		       sta->sta.addr, tid);
		spin_lock_bh(&sta->lock);
		ieee80211_agg_splice_packets(sdata, tid_tx, tid);
		ieee80211_assign_tid_tx(sta, tid, NULL);
		ieee80211_agg_splice_finish(sdata, tid);
		spin_unlock_bh(&sta->lock);

		ieee80211_agg_start_txq(sta, tid, false);

		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);
	ht_dbg(sdata, "activated addBA response timer on %pM tid %d\n",
	       sta->sta.addr, tid);

	spin_lock_bh(&sta->lock);
	sta->ampdu_mlme.last_addba_req_time[tid] = jiffies;
	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, params.ssn,
				     IEEE80211_MAX_AMPDU_BUF,
				     tid_tx->timeout);
}

/*
 * After accepting the AddBA Response we activated a timer,
 * resetting it after each frame that we send.
 */
static void sta_tx_agg_session_timer_expired(unsigned long data)
{
	/* not an elegant detour, but there is no choice as the timer passes
	 * only one argument, and various sta_info are needed here, so init
	 * flow in sta_info_create gives the TID as data, while the timer_to_id
	 * array gives the sta through container_of */
	u8 *ptid = (u8 *)data;
	u8 *timer_to_id = ptid - *ptid;
	struct sta_info *sta = container_of(timer_to_id, struct sta_info,
					 timer_to_tid[0]);
	struct tid_ampdu_tx *tid_tx;
	unsigned long timeout;

	rcu_read_lock();
	tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[*ptid]);
	if (!tid_tx || test_bit(HT_AGG_STATE_STOPPING, &tid_tx->state)) {
		rcu_read_unlock();
		return;
	}

	timeout = tid_tx->last_tx + TU_TO_JIFFIES(tid_tx->timeout);
	if (time_is_after_jiffies(timeout)) {
		mod_timer(&tid_tx->session_timer, timeout);
		rcu_read_unlock();
		return;
	}

//.........这里部分代码省略.........

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);

	/*
	 * 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_agg(local, tid);

	clear_bit(HT_AGG_STATE_WANT_START, &tid_tx->state);

	/*
	 * make sure no packets are being processed to get
	 * valid starting sequence number
	 */
	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_assign_tid_tx(sta, tid, NULL);
		spin_unlock_bh(&sta->lock);

		ieee80211_wake_queue_agg(local, tid);
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,40))
		kfree_rcu(tid_tx, rcu_head);
#else
		call_rcu(&tid_tx->rcu_head, kfree_tid_tx);
#endif
		return;
	}

	/* we can take packets again now */
	ieee80211_wake_queue_agg(local, tid);

	/* 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);
}