agg-tx.c

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/*
 * HT handling
 *
 * Copyright 2003, Jouni Malinen <[email protected]>
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright 2006-2007  Jiri Benc <[email protected]>
 * Copyright 2007, Michael Wu <[email protected]>
 * 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 ||
        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 << 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_tid(sdata, skb, tid);
}

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);
}

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);

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

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

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

    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);
    __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);
    __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_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);
}

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) {
        ht_dbg(sdata,
               "BA request denied - HW unavailable for tid %d\n", 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);

        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 tid %d\n", 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, 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;

    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 tid %d\n", (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_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;

    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\n");
        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 tid %u\n",
               sta->ampdu_mlme.addba_req_num[tid], 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 tid %u\n",
               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;

    lockdep_assert_held(&sta->ampdu_mlme.mtx);

    tid_tx = rcu_dereference_protected_tid_tx(sta, tid);

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

    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(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);
}

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) {
        ht_dbg(sdata, "Bad TID value: tid = %d (>= %d)\n",
               tid, STA_TID_NUM);
        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_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) {
        ht_dbg(sdata, "Bad TID value: tid = %d (>= %d)\n",
               tid, STA_TID_NUM);
        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\n");
        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(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);

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

    del_timer_sync(&tid_tx->addba_resp_timer);

    ht_dbg(sta->sdata, "switched off addBA timer for tid %d\n", 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 tid %d but we already gave up\n",
               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, WLAN_BACK_INITIATOR,
                        false);
    }

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