[deliverable/linux.git] / net / mac80211 / agg-tx.c

/*
 * 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
 * Copyright(c) 2015 Intel Deutschland GmbH
 *
 * 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"

/**
 * DOC: TX A-MPDU aggregation
 *
 * Aggregation on the TX side requires setting the hardware flag
 * %IEEE80211_HW_AMPDU_AGGREGATION. The driver will then be handed
 * packets with a flag indicating A-MPDU aggregation. The driver
 * or device is responsible for actually aggregating the frames,
 * as well as deciding how many and which to aggregate.
 *
 * 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_irqsafe() function, which will really
 * start the aggregation session after the peer has also responded.
 * If the peer responds negatively, the session will be stopped
 * again right away. Note that it is possible for the aggregation
 * session to be stopped before the driver has indicated that it
 * is done setting it up, in which case it must not indicate the
 * setup completion.
 *
 * Also note that, since we also need to wait for a response from
 * the peer, the driver is notified of the completion of the
 * handshake by the %IEEE80211_AMPDU_TX_OPERATIONAL action to the
 * @ampdu_action callback.
 *
 * Similarly, when the aggregation session is stopped by the peer
 * or something calling 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_irqsafe().
 * Note that the sta can get destroyed before the BA tear down is
 * complete.
 */

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 ||
            sdata->vif.type == NL80211_IFTYPE_MESH_POINT)
                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);
        else if (sdata->vif.type == NL80211_IFTYPE_ADHOC)
                memcpy(mgmt->bssid, sdata->u.ibss.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 << 0);          /* bit 0 A-MSDU support */
        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_CTL_REQ_TX_STATUS;
        ieee80211_tx_skb_tid(sdata, skb, tid);
}
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);
}

/*
 * 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_sub_if_data *sdata, int tid)
{
        int queue = sdata->vif.hw_queue[ieee80211_ac_from_tid(tid)];

        /* we do refcounting here, so don't use the queue reason refcounting */

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

static void __releases(agg_queue)
ieee80211_wake_queue_agg(struct ieee80211_sub_if_data *sdata, int tid)
{
        int queue = sdata->vif.hw_queue[ieee80211_ac_from_tid(tid)];

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

static void
ieee80211_agg_stop_txq(struct sta_info *sta, int tid)
{
        struct ieee80211_txq *txq = sta->sta.txq[tid];
        struct ieee80211_sub_if_data *sdata;
        struct fq *fq;
        struct txq_info *txqi;

        if (!txq)
                return;

        txqi = to_txq_info(txq);
        sdata = vif_to_sdata(txq->vif);
        fq = &sdata->local->fq;

        /* Lock here to protect against further seqno updates on dequeue */
        spin_lock_bh(&fq->lock);
        set_bit(IEEE80211_TXQ_STOP, &txqi->flags);
        spin_unlock_bh(&fq->lock);
}

static void
ieee80211_agg_start_txq(struct sta_info *sta, int tid, bool enable)
{
        struct ieee80211_txq *txq = sta->sta.txq[tid];
        struct txq_info *txqi;

        if (!txq)
                return;

        txqi = to_txq_info(txq);

        if (enable)
                set_bit(IEEE80211_TXQ_AMPDU, &txqi->flags);
        else
                clear_bit(IEEE80211_TXQ_AMPDU, &txqi->flags);

        clear_bit(IEEE80211_TXQ_STOP, &txqi->flags);
        drv_wake_tx_queue(sta->sdata->local, txqi);
}

/*
 * 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_sub_if_data *sdata,
                             struct tid_ampdu_tx *tid_tx, u16 tid)
{
        struct ieee80211_local *local = sdata->local;
        int queue = sdata->vif.hw_queue[ieee80211_ac_from_tid(tid)];
        unsigned long flags;

        ieee80211_stop_queue_agg(sdata, 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_sub_if_data *sdata, u16 tid)
{
        ieee80211_wake_queue_agg(sdata, tid);
}

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);
        ieee80211_agg_start_txq(sta, tid, false);

        kfree_rcu(tid_tx, rcu_head);
}

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;
        struct ieee80211_ampdu_params params = {
                .sta = &sta->sta,
                .tid = tid,
                .buf_size = 0,
                .amsdu = false,
                .timeout = 0,
                .ssn = 0,
        };
        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:
                params.action = IEEE80211_AMPDU_TX_STOP_CONT;
                break;
        case AGG_STOP_DESTROY_STA:
                params.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;
                params.action = IEEE80211_AMPDU_TX_STOP_FLUSH_CONT;
                ret = drv_ampdu_action(local, sta->sdata, &params);
                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, &params);

        /* 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.
                 */
        }

        /*
         * In the case of AGG_STOP_DESTROY_STA, the driver won't
         * necessarily call ieee80211_stop_tx_ba_cb(), so this may
         * seem like we can leave the tid_tx data pending forever.
         * This is true, in a way, but "forever" is only until the
         * station struct is actually destroyed. In the meantime,
         * leaving it around ensures that we don't transmit packets
         * to the driver on this TID which might confuse it.
         */

        return 0;
}

/*
 * 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();
                ht_dbg(sta->sdata,
                       "timer expired on %pM tid %d but we are not (or no longer) expecting addBA response there\n",
                       sta->sta.addr, tid);
                return;
        }

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

        ieee80211_stop_tx_ba_session(&sta->sta, tid);
        rcu_read_unlock();
}

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;
        }

        rcu_read_unlock();

        ht_dbg(sta->sdata, "tx session timer expired on %pM tid %d\n",
               sta->sta.addr, (u16)*ptid);

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

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(sta->reserved_tid == tid,
                 "Requested to start BA session on reserved tid=%d", tid))
                return -EINVAL;

        if (!pubsta->ht_cap.ht_supported)
                return -EINVAL;

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

        if ((tid >= IEEE80211_NUM_TIDS) ||
            !ieee80211_hw_check(&local->hw, AMPDU_AGGREGATION) ||
            ieee80211_hw_check(&local->hw, TX_AMPDU_SETUP_IN_HW))
                return -EINVAL;

        ht_dbg(sdata, "Open BA session requested for %pM tid %u\n",
               pubsta->addr, tid);

        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)) {
                ht_dbg(sdata,
                       "BA sessions blocked - Denying BA session request %pM tid %d\n",
                       sta->sta.addr, tid);
                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) {
                ht_dbg(sdata,
                       "BA request denied - IBSS STA %pM does not advertise HT support\n",
                       pubsta->addr);
                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)) {
                ht_dbg(sdata,
                       "BA request denied - waiting a grace period after %d failed requests on %pM tid %u\n",
                       sta->ampdu_mlme.addba_req_num[tid], sta->sta.addr, tid);
                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]) {
                ht_dbg(sdata,
                       "BA request denied - session is not idle on %pM tid %u\n",
                       sta->sta.addr, tid);
                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;

        /* response 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);

        /* tx timer */
        tid_tx->session_timer.function = sta_tx_agg_session_timer_expired;
        tid_tx->session_timer.data = (unsigned long)&sta->timer_to_tid[tid];
        init_timer_deferrable(&tid_tx->session_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;
        struct ieee80211_ampdu_params params = {
                .sta = &sta->sta,
                .action = IEEE80211_AMPDU_TX_OPERATIONAL,
                .tid = tid,
                .timeout = 0,
                .ssn = 0,
        };

        lockdep_assert_held(&sta->ampdu_mlme.mtx);

        tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
        params.buf_size = tid_tx->buf_size;
        params.amsdu = tid_tx->amsdu;

        ht_dbg(sta->sdata, "Aggregation is on for %pM tid %d\n",
               sta->sta.addr, tid);

        drv_ampdu_action(local, sta->sdata, &params);

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

        spin_unlock_bh(&sta->lock);

        ieee80211_agg_start_txq(sta, tid, true);
}

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

        mutex_lock(&local->sta_mtx);
        sta = sta_info_get_bss(sdata, ra);
        if (!sta) {
                mutex_unlock(&local->sta_mtx);
                ht_dbg(sdata, "Could not find station: %pM\n", ra);
                return;
        }

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

        if (WARN_ON(!tid_tx)) {
                ht_dbg(sdata, "addBA was not requested!\n");
                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_agg_stop_reason reason)
{
        int ret;

        mutex_lock(&sta->ampdu_mlme.mtx);

        ret = ___ieee80211_stop_tx_ba_session(sta, tid, reason);

        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 >= 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;
}
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;
        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_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;
        struct ieee80211_txq *txq;
        u16 capab, tid;
        u8 buf_size;
        bool amsdu;

        capab = le16_to_cpu(mgmt->u.action.u.addba_resp.capab);
        amsdu = capab & IEEE80211_ADDBA_PARAM_AMSDU_MASK;
        tid = (capab & IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;
        buf_size = (capab & IEEE80211_ADDBA_PARAM_BUF_SIZE_MASK) >> 6;
        buf_size = min(buf_size, local->hw.max_tx_aggregation_subframes);

        txq = sta->sta.txq[tid];
        if (!amsdu && txq)
                set_bit(IEEE80211_TXQ_NO_AMSDU, &to_txq_info(txq)->flags);

        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;
                tid_tx->amsdu = amsdu;

                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);
}