mac80211: reply only once to each PS-poll

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / mac80211 / sta_info.c

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2006-2007  Jiri Benc <jbenc@suse.cz>
 *
 * 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/module.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/timer.h>
#include <linux/rtnetlink.h>

#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
#include "rate.h"
#include "sta_info.h"
#include "debugfs_sta.h"
#include "mesh.h"
#include "wme.h"

/**
 * DOC: STA information lifetime rules
 *
 * STA info structures (&struct sta_info) are managed in a hash table
 * for faster lookup and a list for iteration. They are managed using
 * RCU, i.e. access to the list and hash table is protected by RCU.
 *
 * Upon allocating a STA info structure with sta_info_alloc(), the caller
 * owns that structure. It must then insert it into the hash table using
 * either sta_info_insert() or sta_info_insert_rcu(); only in the latter
 * case (which acquires an rcu read section but must not be called from
 * within one) will the pointer still be valid after the call. Note that
 * the caller may not do much with the STA info before inserting it, in
 * particular, it may not start any mesh peer link management or add
 * encryption keys.
 *
 * When the insertion fails (sta_info_insert()) returns non-zero), the
 * structure will have been freed by sta_info_insert()!
 *
 * Station entries are added by mac80211 when you establish a link with a
 * peer. This means different things for the different type of interfaces
 * we support. For a regular station this mean we add the AP sta when we
 * receive an association response from the AP. For IBSS this occurs when
 * get to know about a peer on the same IBSS. For WDS we add the sta for
 * the peer immediately upon device open. When using AP mode we add stations
 * for each respective station upon request from userspace through nl80211.
 *
 * In order to remove a STA info structure, various sta_info_destroy_*()
 * calls are available.
 *
 * There is no concept of ownership on a STA entry, each structure is
 * owned by the global hash table/list until it is removed. All users of
 * the structure need to be RCU protected so that the structure won't be
 * freed before they are done using it.
 */

/* Caller must hold local->sta_lock */
static int sta_info_hash_del(struct ieee80211_local *local,
                             struct sta_info *sta)
{
        struct sta_info *s;

        s = rcu_dereference_protected(local->sta_hash[STA_HASH(sta->sta.addr)],
                                      lockdep_is_held(&local->sta_lock));
        if (!s)
                return -ENOENT;
        if (s == sta) {
                rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)],
                                   s->hnext);
                return 0;
        }

        while (rcu_access_pointer(s->hnext) &&
               rcu_access_pointer(s->hnext) != sta)
                s = rcu_dereference_protected(s->hnext,
                                        lockdep_is_held(&local->sta_lock));
        if (rcu_access_pointer(s->hnext)) {
                rcu_assign_pointer(s->hnext, sta->hnext);
                return 0;
        }

        return -ENOENT;
}

/* protected by RCU */
struct sta_info *sta_info_get(struct ieee80211_sub_if_data *sdata,
                              const u8 *addr)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;

        sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
                                    lockdep_is_held(&local->sta_lock) ||
                                    lockdep_is_held(&local->sta_mtx));
        while (sta) {
                if (sta->sdata == sdata && !sta->dummy &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference_check(sta->hnext,
                                            lockdep_is_held(&local->sta_lock) ||
                                            lockdep_is_held(&local->sta_mtx));
        }
        return sta;
}

/* get a station info entry even if it is a dummy station*/
struct sta_info *sta_info_get_rx(struct ieee80211_sub_if_data *sdata,
                              const u8 *addr)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;

        sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
                                    lockdep_is_held(&local->sta_lock) ||
                                    lockdep_is_held(&local->sta_mtx));
        while (sta) {
                if (sta->sdata == sdata &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference_check(sta->hnext,
                                            lockdep_is_held(&local->sta_lock) ||
                                            lockdep_is_held(&local->sta_mtx));
        }
        return sta;
}

/*
 * Get sta info either from the specified interface
 * or from one of its vlans
 */
struct sta_info *sta_info_get_bss(struct ieee80211_sub_if_data *sdata,
                                  const u8 *addr)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;

        sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
                                    lockdep_is_held(&local->sta_lock) ||
                                    lockdep_is_held(&local->sta_mtx));
        while (sta) {
                if ((sta->sdata == sdata ||
                     (sta->sdata->bss && sta->sdata->bss == sdata->bss)) &&
                    !sta->dummy &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference_check(sta->hnext,
                                            lockdep_is_held(&local->sta_lock) ||
                                            lockdep_is_held(&local->sta_mtx));
        }
        return sta;
}

/*
 * Get sta info either from the specified interface
 * or from one of its vlans (including dummy stations)
 */
struct sta_info *sta_info_get_bss_rx(struct ieee80211_sub_if_data *sdata,
                                  const u8 *addr)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;

        sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
                                    lockdep_is_held(&local->sta_lock) ||
                                    lockdep_is_held(&local->sta_mtx));
        while (sta) {
                if ((sta->sdata == sdata ||
                     (sta->sdata->bss && sta->sdata->bss == sdata->bss)) &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference_check(sta->hnext,
                                            lockdep_is_held(&local->sta_lock) ||
                                            lockdep_is_held(&local->sta_mtx));
        }
        return sta;
}

struct sta_info *sta_info_get_by_idx(struct ieee80211_sub_if_data *sdata,
                                     int idx)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        int i = 0;

        list_for_each_entry_rcu(sta, &local->sta_list, list) {
                if (sdata != sta->sdata)
                        continue;
                if (i < idx) {
                        ++i;
                        continue;
                }
                return sta;
        }

        return NULL;
}

/**
 * __sta_info_free - internal STA free helper
 *
 * @local: pointer to the global information
 * @sta: STA info to free
 *
 * This function must undo everything done by sta_info_alloc()
 * that may happen before sta_info_insert().
 */
static void __sta_info_free(struct ieee80211_local *local,
                            struct sta_info *sta)
{
        if (sta->rate_ctrl) {
                rate_control_free_sta(sta);
                rate_control_put(sta->rate_ctrl);
        }

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        wiphy_debug(local->hw.wiphy, "Destroyed STA %pM\n", sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */

        kfree(sta);
}

/* Caller must hold local->sta_lock */
static void sta_info_hash_add(struct ieee80211_local *local,
                              struct sta_info *sta)
{
        sta->hnext = local->sta_hash[STA_HASH(sta->sta.addr)];
        rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)], sta);
}

static void sta_unblock(struct work_struct *wk)
{
        struct sta_info *sta;

        sta = container_of(wk, struct sta_info, drv_unblock_wk);

        if (sta->dead)
                return;

        if (!test_sta_flags(sta, WLAN_STA_PS_STA))
                ieee80211_sta_ps_deliver_wakeup(sta);
        else if (test_and_clear_sta_flags(sta, WLAN_STA_PSPOLL)) {
                clear_sta_flags(sta, WLAN_STA_PS_DRIVER);

                local_bh_disable();
                ieee80211_sta_ps_deliver_poll_response(sta);
                local_bh_enable();
        } else if (test_and_clear_sta_flags(sta, WLAN_STA_UAPSD)) {
                clear_sta_flags(sta, WLAN_STA_PS_DRIVER);

                local_bh_disable();
                ieee80211_sta_ps_deliver_uapsd(sta);
                local_bh_enable();
        } else
                clear_sta_flags(sta, WLAN_STA_PS_DRIVER);
}

static int sta_prepare_rate_control(struct ieee80211_local *local,
                                    struct sta_info *sta, gfp_t gfp)
{
        if (local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL)
                return 0;

        sta->rate_ctrl = rate_control_get(local->rate_ctrl);
        sta->rate_ctrl_priv = rate_control_alloc_sta(sta->rate_ctrl,
                                                     &sta->sta, gfp);
        if (!sta->rate_ctrl_priv) {
                rate_control_put(sta->rate_ctrl);
                return -ENOMEM;
        }

        return 0;
}

struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
                                u8 *addr, gfp_t gfp)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta;
        struct timespec uptime;
        int i;

        sta = kzalloc(sizeof(*sta) + local->hw.sta_data_size, gfp);
        if (!sta)
                return NULL;

        spin_lock_init(&sta->lock);
        spin_lock_init(&sta->flaglock);
        INIT_WORK(&sta->drv_unblock_wk, sta_unblock);
        INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);
        mutex_init(&sta->ampdu_mlme.mtx);

        memcpy(sta->sta.addr, addr, ETH_ALEN);
        sta->local = local;
        sta->sdata = sdata;
        sta->last_rx = jiffies;

        do_posix_clock_monotonic_gettime(&uptime);
        sta->last_connected = uptime.tv_sec;
        ewma_init(&sta->avg_signal, 1024, 8);

        if (sta_prepare_rate_control(local, sta, gfp)) {
                kfree(sta);
                return NULL;
        }

        for (i = 0; i < STA_TID_NUM; i++) {
                /*
                 * timer_to_tid must be initialized with identity mapping
                 * to enable session_timer's data differentiation. See
                 * sta_rx_agg_session_timer_expired for usage.
                 */
                sta->timer_to_tid[i] = i;
        }
        for (i = 0; i < IEEE80211_NUM_ACS; i++) {
                skb_queue_head_init(&sta->ps_tx_buf[i]);
                skb_queue_head_init(&sta->tx_filtered[i]);
        }

        for (i = 0; i < NUM_RX_DATA_QUEUES; i++)
                sta->last_seq_ctrl[i] = cpu_to_le16(USHRT_MAX);

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        wiphy_debug(local->hw.wiphy, "Allocated STA %pM\n", sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */

#ifdef CONFIG_MAC80211_MESH
        sta->plink_state = NL80211_PLINK_LISTEN;
        init_timer(&sta->plink_timer);
#endif

        return sta;
}

static int sta_info_finish_insert(struct sta_info *sta,
                                bool async, bool dummy_reinsert)
{
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct station_info sinfo;
        unsigned long flags;
        int err = 0;

        lockdep_assert_held(&local->sta_mtx);

        if (!sta->dummy || dummy_reinsert) {
                /* notify driver */
                if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                        sdata = container_of(sdata->bss,
                                             struct ieee80211_sub_if_data,
                                             u.ap);
                err = drv_sta_add(local, sdata, &sta->sta);
                if (err) {
                        if (!async)
                                return err;
                        printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to "
                                          "driver (%d) - keeping it anyway.\n",
                               sdata->name, sta->sta.addr, err);
                } else {
                        sta->uploaded = true;
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                        if (async)
                                wiphy_debug(local->hw.wiphy,
                                            "Finished adding IBSS STA %pM\n",
                                            sta->sta.addr);
#endif
                }

                sdata = sta->sdata;
        }

        if (!dummy_reinsert) {
                if (!async) {
                        local->num_sta++;
                        local->sta_generation++;
                        smp_mb();

                        /* make the station visible */
                        spin_lock_irqsave(&local->sta_lock, flags);
                        sta_info_hash_add(local, sta);
                        spin_unlock_irqrestore(&local->sta_lock, flags);
                }

                list_add(&sta->list, &local->sta_list);
        } else {
                sta->dummy = false;
        }

        if (!sta->dummy) {
                ieee80211_sta_debugfs_add(sta);
                rate_control_add_sta_debugfs(sta);

                memset(&sinfo, 0, sizeof(sinfo));
                sinfo.filled = 0;
                sinfo.generation = local->sta_generation;
                cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
        }

        return 0;
}

static void sta_info_finish_pending(struct ieee80211_local *local)
{
        struct sta_info *sta;
        unsigned long flags;

        spin_lock_irqsave(&local->sta_lock, flags);
        while (!list_empty(&local->sta_pending_list)) {
                sta = list_first_entry(&local->sta_pending_list,
                                       struct sta_info, list);
                list_del(&sta->list);
                spin_unlock_irqrestore(&local->sta_lock, flags);

                sta_info_finish_insert(sta, true, false);

                spin_lock_irqsave(&local->sta_lock, flags);
        }
        spin_unlock_irqrestore(&local->sta_lock, flags);
}

static void sta_info_finish_work(struct work_struct *work)
{
        struct ieee80211_local *local =
                container_of(work, struct ieee80211_local, sta_finish_work);

        mutex_lock(&local->sta_mtx);
        sta_info_finish_pending(local);
        mutex_unlock(&local->sta_mtx);
}

static int sta_info_insert_check(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;

        /*
         * Can't be a WARN_ON because it can be triggered through a race:
         * something inserts a STA (on one CPU) without holding the RTNL
         * and another CPU turns off the net device.
         */
        if (unlikely(!ieee80211_sdata_running(sdata)))
                return -ENETDOWN;

        if (WARN_ON(compare_ether_addr(sta->sta.addr, sdata->vif.addr) == 0 ||
                    is_multicast_ether_addr(sta->sta.addr)))
                return -EINVAL;

        return 0;
}

static int sta_info_insert_ibss(struct sta_info *sta) __acquires(RCU)
{
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        unsigned long flags;

        spin_lock_irqsave(&local->sta_lock, flags);
        /* check if STA exists already */
        if (sta_info_get_bss_rx(sdata, sta->sta.addr)) {
                spin_unlock_irqrestore(&local->sta_lock, flags);
                rcu_read_lock();
                return -EEXIST;
        }

        local->num_sta++;
        local->sta_generation++;
        smp_mb();
        sta_info_hash_add(local, sta);

        list_add_tail(&sta->list, &local->sta_pending_list);

        rcu_read_lock();
        spin_unlock_irqrestore(&local->sta_lock, flags);

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        wiphy_debug(local->hw.wiphy, "Added IBSS STA %pM\n",
                        sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */

        ieee80211_queue_work(&local->hw, &local->sta_finish_work);

        return 0;
}

/*
 * should be called with sta_mtx locked
 * this function replaces the mutex lock
 * with a RCU lock
 */
static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
{
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        unsigned long flags;
        struct sta_info *exist_sta;
        bool dummy_reinsert = false;
        int err = 0;

        lockdep_assert_held(&local->sta_mtx);

        /*
         * On first glance, this will look racy, because the code
         * in this function, which inserts a station with sleeping,
         * unlocks the sta_lock between checking existence in the
         * hash table and inserting into it.
         *
         * However, it is not racy against itself because it keeps
         * the mutex locked.
         */

        spin_lock_irqsave(&local->sta_lock, flags);
        /*
         * check if STA exists already.
         * only accept a scenario of a second call to sta_info_insert_non_ibss
         * with a dummy station entry that was inserted earlier
         * in that case - assume that the dummy station flag should
         * be removed.
         */
        exist_sta = sta_info_get_bss_rx(sdata, sta->sta.addr);
        if (exist_sta) {
                if (exist_sta == sta && sta->dummy) {
                        dummy_reinsert = true;
                } else {
                        spin_unlock_irqrestore(&local->sta_lock, flags);
                        mutex_unlock(&local->sta_mtx);
                        rcu_read_lock();
                        return -EEXIST;
                }
        }

        spin_unlock_irqrestore(&local->sta_lock, flags);

        err = sta_info_finish_insert(sta, false, dummy_reinsert);
        if (err) {
                mutex_unlock(&local->sta_mtx);
                rcu_read_lock();
                return err;
        }

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        wiphy_debug(local->hw.wiphy, "Inserted %sSTA %pM\n",
                        sta->dummy ? "dummy " : "", sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */

        /* move reference to rcu-protected */
        rcu_read_lock();
        mutex_unlock(&local->sta_mtx);

        if (ieee80211_vif_is_mesh(&sdata->vif))
                mesh_accept_plinks_update(sdata);

        return 0;
}

int sta_info_insert_rcu(struct sta_info *sta) __acquires(RCU)
{
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        int err = 0;

        err = sta_info_insert_check(sta);
        if (err) {
                rcu_read_lock();
                goto out_free;
        }

        /*
         * In ad-hoc mode, we sometimes need to insert stations
         * from tasklet context from the RX path. To avoid races,
         * always do so in that case -- see the comment below.
         */
        if (sdata->vif.type == NL80211_IFTYPE_ADHOC) {
                err = sta_info_insert_ibss(sta);
                if (err)
                        goto out_free;

                return 0;
        }

        /*
         * It might seem that the function called below is in race against
         * the function call above that atomically inserts the station... That,
         * however, is not true because the above code can only
         * be invoked for IBSS interfaces, and the below code will
         * not be -- and the two do not race against each other as
         * the hash table also keys off the interface.
         */

        might_sleep();

        mutex_lock(&local->sta_mtx);

        err = sta_info_insert_non_ibss(sta);
        if (err)
                goto out_free;

        return 0;
 out_free:
        BUG_ON(!err);
        __sta_info_free(local, sta);
        return err;
}

int sta_info_insert(struct sta_info *sta)
{
        int err = sta_info_insert_rcu(sta);

        rcu_read_unlock();

        return err;
}

/* Caller must hold sta->local->sta_mtx */
int sta_info_reinsert(struct sta_info *sta)
{
        struct ieee80211_local *local = sta->local;
        int err = 0;

        err = sta_info_insert_check(sta);
        if (err) {
                mutex_unlock(&local->sta_mtx);
                return err;
        }

        might_sleep();

        err = sta_info_insert_non_ibss(sta);
        rcu_read_unlock();
        return err;
}

static inline void __bss_tim_set(struct ieee80211_if_ap *bss, u16 aid)
{
        /*
         * This format has been mandated by the IEEE specifications,
         * so this line may not be changed to use the __set_bit() format.
         */
        bss->tim[aid / 8] |= (1 << (aid % 8));
}

static inline void __bss_tim_clear(struct ieee80211_if_ap *bss, u16 aid)
{
        /*
         * This format has been mandated by the IEEE specifications,
         * so this line may not be changed to use the __clear_bit() format.
         */
        bss->tim[aid / 8] &= ~(1 << (aid % 8));
}

static unsigned long ieee80211_tids_for_ac(int ac)
{
        /* If we ever support TIDs > 7, this obviously needs to be adjusted */
        switch (ac) {
        case IEEE80211_AC_VO:
                return BIT(6) | BIT(7);
        case IEEE80211_AC_VI:
                return BIT(4) | BIT(5);
        case IEEE80211_AC_BE:
                return BIT(0) | BIT(3);
        case IEEE80211_AC_BK:
                return BIT(1) | BIT(2);
        default:
                WARN_ON(1);
                return 0;
        }
}

void sta_info_recalc_tim(struct sta_info *sta)
{
        struct ieee80211_local *local = sta->local;
        struct ieee80211_if_ap *bss = sta->sdata->bss;
        unsigned long flags;
        bool indicate_tim = false;
        u8 ignore_for_tim = sta->sta.uapsd_queues;
        int ac;

        if (WARN_ON_ONCE(!sta->sdata->bss))
                return;

        /* No need to do anything if the driver does all */
        if (local->hw.flags & IEEE80211_HW_AP_LINK_PS)
                return;

        if (sta->dead)
                goto done;

        /*
         * If all ACs are delivery-enabled then we should build
         * the TIM bit for all ACs anyway; if only some are then
         * we ignore those and build the TIM bit using only the
         * non-enabled ones.
         */
        if (ignore_for_tim == BIT(IEEE80211_NUM_ACS) - 1)
                ignore_for_tim = 0;

        for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
                unsigned long tids;

                if (ignore_for_tim & BIT(ac))
                        continue;

                indicate_tim |= !skb_queue_empty(&sta->tx_filtered[ac]) ||
                                !skb_queue_empty(&sta->ps_tx_buf[ac]);
                if (indicate_tim)
                        break;

                tids = ieee80211_tids_for_ac(ac);

                indicate_tim |=
                        sta->driver_buffered_tids & tids;
        }

 done:
        spin_lock_irqsave(&local->sta_lock, flags);

        if (indicate_tim)
                __bss_tim_set(bss, sta->sta.aid);
        else
                __bss_tim_clear(bss, sta->sta.aid);

        if (local->ops->set_tim) {
                local->tim_in_locked_section = true;
                drv_set_tim(local, &sta->sta, indicate_tim);
                local->tim_in_locked_section = false;
        }

        spin_unlock_irqrestore(&local->sta_lock, flags);
}

static bool sta_info_buffer_expired(struct sta_info *sta, struct sk_buff *skb)
{
        struct ieee80211_tx_info *info;
        int timeout;

        if (!skb)
                return false;

        info = IEEE80211_SKB_CB(skb);

        /* Timeout: (2 * listen_interval * beacon_int * 1024 / 1000000) sec */
        timeout = (sta->listen_interval *
                   sta->sdata->vif.bss_conf.beacon_int *
                   32 / 15625) * HZ;
        if (timeout < STA_TX_BUFFER_EXPIRE)
                timeout = STA_TX_BUFFER_EXPIRE;
        return time_after(jiffies, info->control.jiffies + timeout);
}


static bool sta_info_cleanup_expire_buffered_ac(struct ieee80211_local *local,
                                                struct sta_info *sta, int ac)
{
        unsigned long flags;
        struct sk_buff *skb;

        /*
         * First check for frames that should expire on the filtered
         * queue. Frames here were rejected by the driver and are on
         * a separate queue to avoid reordering with normal PS-buffered
         * frames. They also aren't accounted for right now in the
         * total_ps_buffered counter.
         */
        for (;;) {
                spin_lock_irqsave(&sta->tx_filtered[ac].lock, flags);
                skb = skb_peek(&sta->tx_filtered[ac]);
                if (sta_info_buffer_expired(sta, skb))
                        skb = __skb_dequeue(&sta->tx_filtered[ac]);
                else
                        skb = NULL;
                spin_unlock_irqrestore(&sta->tx_filtered[ac].lock, flags);

                /*
                 * Frames are queued in order, so if this one
                 * hasn't expired yet we can stop testing. If
                 * we actually reached the end of the queue we
                 * also need to stop, of course.
                 */
                if (!skb)
                        break;
                dev_kfree_skb(skb);
        }

        /*
         * Now also check the normal PS-buffered queue, this will
         * only find something if the filtered queue was emptied
         * since the filtered frames are all before the normal PS
         * buffered frames.
         */
        for (;;) {
                spin_lock_irqsave(&sta->ps_tx_buf[ac].lock, flags);
                skb = skb_peek(&sta->ps_tx_buf[ac]);
                if (sta_info_buffer_expired(sta, skb))
                        skb = __skb_dequeue(&sta->ps_tx_buf[ac]);
                else
                        skb = NULL;
                spin_unlock_irqrestore(&sta->ps_tx_buf[ac].lock, flags);

                /*
                 * frames are queued in order, so if this one
                 * hasn't expired yet (or we reached the end of
                 * the queue) we can stop testing
                 */
                if (!skb)
                        break;

                local->total_ps_buffered--;
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                printk(KERN_DEBUG "Buffered frame expired (STA %pM)\n",
                       sta->sta.addr);
#endif
                dev_kfree_skb(skb);
        }

        /*
         * Finally, recalculate the TIM bit for this station -- it might
         * now be clear because the station was too slow to retrieve its
         * frames.
         */
        sta_info_recalc_tim(sta);

        /*
         * Return whether there are any frames still buffered, this is
         * used to check whether the cleanup timer still needs to run,
         * if there are no frames we don't need to rearm the timer.
         */
        return !(skb_queue_empty(&sta->ps_tx_buf[ac]) &&
                 skb_queue_empty(&sta->tx_filtered[ac]));
}

static bool sta_info_cleanup_expire_buffered(struct ieee80211_local *local,
                                             struct sta_info *sta)
{
        bool have_buffered = false;
        int ac;

        /* This is only necessary for stations on BSS interfaces */
        if (!sta->sdata->bss)
                return false;

        for (ac = 0; ac < IEEE80211_NUM_ACS; ac++)
                have_buffered |=
                        sta_info_cleanup_expire_buffered_ac(local, sta, ac);

        return have_buffered;
}

static int __must_check __sta_info_destroy(struct sta_info *sta)
{
        struct ieee80211_local *local;
        struct ieee80211_sub_if_data *sdata;
        unsigned long flags;
        int ret, i, ac;

        might_sleep();

        if (!sta)
                return -ENOENT;

        local = sta->local;
        sdata = sta->sdata;

        /*
         * Before removing the station from the driver and
         * rate control, it might still start new aggregation
         * sessions -- block that to make sure the tear-down
         * will be sufficient.
         */
        set_sta_flags(sta, WLAN_STA_BLOCK_BA);
        ieee80211_sta_tear_down_BA_sessions(sta, true);

        spin_lock_irqsave(&local->sta_lock, flags);
        ret = sta_info_hash_del(local, sta);
        /* this might still be the pending list ... which is fine */
        if (!ret)
                list_del(&sta->list);
        spin_unlock_irqrestore(&local->sta_lock, flags);
        if (ret)
                return ret;

        mutex_lock(&local->key_mtx);
        for (i = 0; i < NUM_DEFAULT_KEYS; i++)
                __ieee80211_key_free(key_mtx_dereference(local, sta->gtk[i]));
        if (sta->ptk)
                __ieee80211_key_free(key_mtx_dereference(local, sta->ptk));
        mutex_unlock(&local->key_mtx);

        sta->dead = true;

        if (test_and_clear_sta_flags(sta,
                                WLAN_STA_PS_STA | WLAN_STA_PS_DRIVER)) {
                BUG_ON(!sdata->bss);

                atomic_dec(&sdata->bss->num_sta_ps);
                sta_info_recalc_tim(sta);
        }

        local->num_sta--;
        local->sta_generation++;

        if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                rcu_assign_pointer(sdata->u.vlan.sta, NULL);

        if (sta->uploaded) {
                if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
                        sdata = container_of(sdata->bss,
                                             struct ieee80211_sub_if_data,
                                             u.ap);
                drv_sta_remove(local, sdata, &sta->sta);
                sdata = sta->sdata;
        }

        /*
         * At this point, after we wait for an RCU grace period,
         * neither mac80211 nor the driver can reference this
         * sta struct any more except by still existing timers
         * associated with this station that we clean up below.
         */
        synchronize_rcu();

        for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
                local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);
                __skb_queue_purge(&sta->ps_tx_buf[ac]);
                __skb_queue_purge(&sta->tx_filtered[ac]);
        }

#ifdef CONFIG_MAC80211_MESH
        if (ieee80211_vif_is_mesh(&sdata->vif))
                mesh_accept_plinks_update(sdata);
#endif

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        wiphy_debug(local->hw.wiphy, "Removed STA %pM\n", sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
        cancel_work_sync(&sta->drv_unblock_wk);

        cfg80211_del_sta(sdata->dev, sta->sta.addr, GFP_KERNEL);

        rate_control_remove_sta_debugfs(sta);
        ieee80211_sta_debugfs_remove(sta);

#ifdef CONFIG_MAC80211_MESH
        if (ieee80211_vif_is_mesh(&sta->sdata->vif)) {
                mesh_plink_deactivate(sta);
                del_timer_sync(&sta->plink_timer);
        }
#endif

        __sta_info_free(local, sta);

        return 0;
}

int sta_info_destroy_addr(struct ieee80211_sub_if_data *sdata, const u8 *addr)
{
        struct sta_info *sta;
        int ret;

        mutex_lock(&sdata->local->sta_mtx);
        sta = sta_info_get_rx(sdata, addr);
        ret = __sta_info_destroy(sta);
        mutex_unlock(&sdata->local->sta_mtx);

        return ret;
}

int sta_info_destroy_addr_bss(struct ieee80211_sub_if_data *sdata,
                              const u8 *addr)
{
        struct sta_info *sta;
        int ret;

        mutex_lock(&sdata->local->sta_mtx);
        sta = sta_info_get_bss_rx(sdata, addr);
        ret = __sta_info_destroy(sta);
        mutex_unlock(&sdata->local->sta_mtx);

        return ret;
}

static void sta_info_cleanup(unsigned long data)
{
        struct ieee80211_local *local = (struct ieee80211_local *) data;
        struct sta_info *sta;
        bool timer_needed = false;

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &local->sta_list, list)
                if (sta_info_cleanup_expire_buffered(local, sta))
                        timer_needed = true;
        rcu_read_unlock();

        if (local->quiescing)
                return;

        if (!timer_needed)
                return;

        mod_timer(&local->sta_cleanup,
                  round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL));
}

void sta_info_init(struct ieee80211_local *local)
{
        spin_lock_init(&local->sta_lock);
        mutex_init(&local->sta_mtx);
        INIT_LIST_HEAD(&local->sta_list);
        INIT_LIST_HEAD(&local->sta_pending_list);
        INIT_WORK(&local->sta_finish_work, sta_info_finish_work);

        setup_timer(&local->sta_cleanup, sta_info_cleanup,
                    (unsigned long)local);
}

void sta_info_stop(struct ieee80211_local *local)
{
        del_timer(&local->sta_cleanup);
        sta_info_flush(local, NULL);
}

/**
 * sta_info_flush - flush matching STA entries from the STA table
 *
 * Returns the number of removed STA entries.
 *
 * @local: local interface data
 * @sdata: matching rule for the net device (sta->dev) or %NULL to match all STAs
 */
int sta_info_flush(struct ieee80211_local *local,
                   struct ieee80211_sub_if_data *sdata)
{
        struct sta_info *sta, *tmp;
        int ret = 0;

        might_sleep();

        mutex_lock(&local->sta_mtx);

        sta_info_finish_pending(local);

        list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
                if (!sdata || sdata == sta->sdata)
                        WARN_ON(__sta_info_destroy(sta));
        }
        mutex_unlock(&local->sta_mtx);

        return ret;
}

void ieee80211_sta_expire(struct ieee80211_sub_if_data *sdata,
                          unsigned long exp_time)
{
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta, *tmp;

        mutex_lock(&local->sta_mtx);
        list_for_each_entry_safe(sta, tmp, &local->sta_list, list)
                if (time_after(jiffies, sta->last_rx + exp_time)) {
#ifdef CONFIG_MAC80211_IBSS_DEBUG
                        printk(KERN_DEBUG "%s: expiring inactive STA %pM\n",
                               sdata->name, sta->sta.addr);
#endif
                        WARN_ON(__sta_info_destroy(sta));
                }
        mutex_unlock(&local->sta_mtx);
}

struct ieee80211_sta *ieee80211_find_sta_by_ifaddr(struct ieee80211_hw *hw,
                                               const u8 *addr,
                                               const u8 *localaddr)
{
        struct sta_info *sta, *nxt;

        /*
         * Just return a random station if localaddr is NULL
         * ... first in list.
         */
        for_each_sta_info(hw_to_local(hw), addr, sta, nxt) {
                if (localaddr &&
                    compare_ether_addr(sta->sdata->vif.addr, localaddr) != 0)
                        continue;
                if (!sta->uploaded)
                        return NULL;
                return &sta->sta;
        }

        return NULL;
}
EXPORT_SYMBOL_GPL(ieee80211_find_sta_by_ifaddr);

struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_vif *vif,
                                         const u8 *addr)
{
        struct sta_info *sta;

        if (!vif)
                return NULL;

        sta = sta_info_get_bss(vif_to_sdata(vif), addr);
        if (!sta)
                return NULL;

        if (!sta->uploaded)
                return NULL;

        return &sta->sta;
}
EXPORT_SYMBOL(ieee80211_find_sta);

static void clear_sta_ps_flags(void *_sta)
{
        struct sta_info *sta = _sta;

        clear_sta_flags(sta, WLAN_STA_PS_DRIVER | WLAN_STA_PS_STA);
}

/* powersave support code */
void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct ieee80211_local *local = sdata->local;
        struct sk_buff_head pending;
        int filtered = 0, buffered = 0, ac;

        clear_sta_flags(sta, WLAN_STA_SP);

        BUILD_BUG_ON(BITS_TO_LONGS(STA_TID_NUM) > 1);
        sta->driver_buffered_tids = 0;

        if (!(local->hw.flags & IEEE80211_HW_AP_LINK_PS))
                drv_sta_notify(local, sdata, STA_NOTIFY_AWAKE, &sta->sta);

        skb_queue_head_init(&pending);

        /* Send all buffered frames to the station */
        for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
                int count = skb_queue_len(&pending), tmp;

                skb_queue_splice_tail_init(&sta->tx_filtered[ac], &pending);
                tmp = skb_queue_len(&pending);
                filtered += tmp - count;
                count = tmp;

                skb_queue_splice_tail_init(&sta->ps_tx_buf[ac], &pending);
                tmp = skb_queue_len(&pending);
                buffered += tmp - count;
        }

        ieee80211_add_pending_skbs_fn(local, &pending, clear_sta_ps_flags, sta);

        local->total_ps_buffered -= buffered;

        sta_info_recalc_tim(sta);

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        printk(KERN_DEBUG "%s: STA %pM aid %d sending %d filtered/%d PS frames "
               "since STA not sleeping anymore\n", sdata->name,
               sta->sta.addr, sta->sta.aid, filtered, buffered);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}

static void ieee80211_send_null_response(struct ieee80211_sub_if_data *sdata,
                                         struct sta_info *sta, int tid,
                                         bool uapsd)
{
        struct ieee80211_local *local = sdata->local;
        struct ieee80211_qos_hdr *nullfunc;
        struct sk_buff *skb;
        int size = sizeof(*nullfunc);
        __le16 fc;
        bool qos = test_sta_flags(sta, WLAN_STA_WME);
        struct ieee80211_tx_info *info;

        if (qos) {
                fc = cpu_to_le16(IEEE80211_FTYPE_DATA |
                                 IEEE80211_STYPE_QOS_NULLFUNC |
                                 IEEE80211_FCTL_FROMDS);
        } else {
                size -= 2;
                fc = cpu_to_le16(IEEE80211_FTYPE_DATA |
                                 IEEE80211_STYPE_NULLFUNC |
                                 IEEE80211_FCTL_FROMDS);
        }

        skb = dev_alloc_skb(local->hw.extra_tx_headroom + size);
        if (!skb)
                return;

        skb_reserve(skb, local->hw.extra_tx_headroom);

        nullfunc = (void *) skb_put(skb, size);
        nullfunc->frame_control = fc;
        nullfunc->duration_id = 0;
        memcpy(nullfunc->addr1, sta->sta.addr, ETH_ALEN);
        memcpy(nullfunc->addr2, sdata->vif.addr, ETH_ALEN);
        memcpy(nullfunc->addr3, sdata->vif.addr, ETH_ALEN);

        if (qos) {
                skb->priority = tid;

                skb_set_queue_mapping(skb, ieee802_1d_to_ac[tid]);

                nullfunc->qos_ctrl = cpu_to_le16(tid);

                if (uapsd)
                        nullfunc->qos_ctrl |=
                                cpu_to_le16(IEEE80211_QOS_CTL_EOSP);
        }

        info = IEEE80211_SKB_CB(skb);

        /*
         * Tell TX path to send this frame even though the
         * STA may still remain is PS mode after this frame
         * exchange. Also set EOSP to indicate this packet
         * ends the poll/service period.
         */
        info->flags |= IEEE80211_TX_CTL_POLL_RESPONSE |
                       IEEE80211_TX_STATUS_EOSP |
                       IEEE80211_TX_CTL_REQ_TX_STATUS;

        ieee80211_xmit(sdata, skb);
}

static void
ieee80211_sta_ps_deliver_response(struct sta_info *sta,
                                  int n_frames, u8 ignored_acs,
                                  enum ieee80211_frame_release_type reason)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct ieee80211_local *local = sdata->local;
        bool found = false;
        bool more_data = false;
        int ac;
        unsigned long driver_release_tids = 0;
        struct sk_buff_head frames;

        /* Service or PS-Poll period starts */
        set_sta_flags(sta, WLAN_STA_SP);

        __skb_queue_head_init(&frames);

        /*
         * Get response frame(s) and more data bit for it.
         */
        for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
                unsigned long tids;

                if (ignored_acs & BIT(ac))
                        continue;

                tids = ieee80211_tids_for_ac(ac);

                if (!found) {
                        driver_release_tids = sta->driver_buffered_tids & tids;
                        if (driver_release_tids) {
                                found = true;
                        } else {
                                struct sk_buff *skb;

                                while (n_frames > 0) {
                                        skb = skb_dequeue(&sta->tx_filtered[ac]);
                                        if (!skb) {
                                                skb = skb_dequeue(
                                                        &sta->ps_tx_buf[ac]);
                                                if (skb)
                                                        local->total_ps_buffered--;
                                        }
                                        if (!skb)
                                                break;
                                        n_frames--;
                                        found = true;
                                        __skb_queue_tail(&frames, skb);
                                }
                        }

                        /*
                         * If the driver has data on more than one TID then
                         * certainly there's more data if we release just a
                         * single frame now (from a single TID).
                         */
                        if (reason == IEEE80211_FRAME_RELEASE_PSPOLL &&
                            hweight16(driver_release_tids) > 1) {
                                more_data = true;
                                driver_release_tids =
                                        BIT(ffs(driver_release_tids) - 1);
                                break;
                        }
                }

                if (!skb_queue_empty(&sta->tx_filtered[ac]) ||
                    !skb_queue_empty(&sta->ps_tx_buf[ac])) {
                        more_data = true;
                        break;
                }
        }

        if (!found) {
                int tid;

                /*
                 * For PS-Poll, this can only happen due to a race condition
                 * when we set the TIM bit and the station notices it, but
                 * before it can poll for the frame we expire it.
                 *
                 * For uAPSD, this is said in the standard (11.2.1.5 h):
                 *      At each unscheduled SP for a non-AP STA, the AP shall
                 *      attempt to transmit at least one MSDU or MMPDU, but no
                 *      more than the value specified in the Max SP Length field
                 *      in the QoS Capability element from delivery-enabled ACs,
                 *      that are destined for the non-AP STA.
                 *
                 * Since we have no other MSDU/MMPDU, transmit a QoS null frame.
                 */

                /* This will evaluate to 1, 3, 5 or 7. */
                tid = 7 - ((ffs(~ignored_acs) - 1) << 1);

                ieee80211_send_null_response(sdata, sta, tid,
                                reason == IEEE80211_FRAME_RELEASE_UAPSD);
                return;
        }

        if (!driver_release_tids) {
                struct sk_buff_head pending;
                struct sk_buff *skb;

                skb_queue_head_init(&pending);

                while ((skb = __skb_dequeue(&frames))) {
                        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
                        struct ieee80211_hdr *hdr = (void *) skb->data;

                        /*
                         * Tell TX path to send this frame even though the
                         * STA may still remain is PS mode after this frame
                         * exchange.
                         */
                        info->flags |= IEEE80211_TX_CTL_POLL_RESPONSE;

                        /*
                         * Use MoreData flag to indicate whether there are
                         * more buffered frames for this STA
                         */
                        if (!more_data)
                                hdr->frame_control &=
                                        cpu_to_le16(~IEEE80211_FCTL_MOREDATA);
                        else
                                hdr->frame_control |=
                                        cpu_to_le16(IEEE80211_FCTL_MOREDATA);

                        if (reason == IEEE80211_FRAME_RELEASE_UAPSD &&
                            skb_queue_empty(&frames)) {
                                /* set EOSP for the frame */
                                u8 *p = ieee80211_get_qos_ctl(hdr);
                                *p |= IEEE80211_QOS_CTL_EOSP;
                        }

                        info->flags |= IEEE80211_TX_STATUS_EOSP |
                                       IEEE80211_TX_CTL_REQ_TX_STATUS;

                        __skb_queue_tail(&pending, skb);
                }

                ieee80211_add_pending_skbs(local, &pending);

                sta_info_recalc_tim(sta);
        } else {
                /*
                 * We need to release a frame that is buffered somewhere in the
                 * driver ... it'll have to handle that.
                 * Note that, as per the comment above, it'll also have to see
                 * if there is more than just one frame on the specific TID that
                 * we're releasing from, and it needs to set the more-data bit
                 * accordingly if we tell it that there's no more data. If we do
                 * tell it there's more data, then of course the more-data bit
                 * needs to be set anyway.
                 */
                drv_release_buffered_frames(local, sta, driver_release_tids,
                                            n_frames, reason, more_data);

                /*
                 * Note that we don't recalculate the TIM bit here as it would
                 * most likely have no effect at all unless the driver told us
                 * that the TID became empty before returning here from the
                 * release function.
                 * Either way, however, when the driver tells us that the TID
                 * became empty we'll do the TIM recalculation.
                 */
        }
}

void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
{
        u8 ignore_for_response = sta->sta.uapsd_queues;

        /*
         * If all ACs are delivery-enabled then we should reply
         * from any of them, if only some are enabled we reply
         * only from the non-enabled ones.
         */
        if (ignore_for_response == BIT(IEEE80211_NUM_ACS) - 1)
                ignore_for_response = 0;

        ieee80211_sta_ps_deliver_response(sta, 1, ignore_for_response,
                                          IEEE80211_FRAME_RELEASE_PSPOLL);
}

void ieee80211_sta_ps_deliver_uapsd(struct sta_info *sta)
{
        int n_frames = sta->sta.max_sp;
        u8 delivery_enabled = sta->sta.uapsd_queues;

        /*
         * If we ever grow support for TSPEC this might happen if
         * the TSPEC update from hostapd comes in between a trigger
         * frame setting WLAN_STA_UAPSD in the RX path and this
         * actually getting called.
         */
        if (!delivery_enabled)
                return;

        switch (sta->sta.max_sp) {
        case 1:
                n_frames = 2;
                break;
        case 2:
                n_frames = 4;
                break;
        case 3:
                n_frames = 6;
                break;
        case 0:
                /* XXX: what is a good value? */
                n_frames = 8;
                break;
        }

        ieee80211_sta_ps_deliver_response(sta, n_frames, ~delivery_enabled,
                                          IEEE80211_FRAME_RELEASE_UAPSD);
}

void ieee80211_sta_block_awake(struct ieee80211_hw *hw,
                               struct ieee80211_sta *pubsta, bool block)
{
        struct sta_info *sta = container_of(pubsta, struct sta_info, sta);

        trace_api_sta_block_awake(sta->local, pubsta, block);

        if (block)
                set_sta_flags(sta, WLAN_STA_PS_DRIVER);
        else if (test_sta_flags(sta, WLAN_STA_PS_DRIVER))
                ieee80211_queue_work(hw, &sta->drv_unblock_wk);
}
EXPORT_SYMBOL(ieee80211_sta_block_awake);

void ieee80211_sta_set_buffered(struct ieee80211_sta *pubsta,
                                u8 tid, bool buffered)
{
        struct sta_info *sta = container_of(pubsta, struct sta_info, sta);

        if (WARN_ON(tid >= STA_TID_NUM))
                return;

        if (buffered)
                set_bit(tid, &sta->driver_buffered_tids);
        else
                clear_bit(tid, &sta->driver_buffered_tids);

        sta_info_recalc_tim(sta);
}
EXPORT_SYMBOL(ieee80211_sta_set_buffered);