mac80211: allow station add/remove to sleep

[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"

/**
 * 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 assocation 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 imediately 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 = local->sta_hash[STA_HASH(sta->sta.addr)];
        if (!s)
                return -ENOENT;
        if (s == sta) {
                rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)],
                                   s->hnext);
                return 0;
        }

        while (s->hnext && s->hnext != sta)
                s = s->hnext;
        if (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(local->sta_hash[STA_HASH(addr)]);
        while (sta) {
                if (sta->sdata == sdata &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference(sta->hnext);
        }
        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(local->sta_hash[STA_HASH(addr)]);
        while (sta) {
                if ((sta->sdata == sdata ||
                     sta->sdata->bss == sdata->bss) &&
                    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
                        break;
                sta = rcu_dereference(sta->hnext);
        }
        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
        printk(KERN_DEBUG "%s: Destroyed STA %pM\n",
               wiphy_name(local->hw.wiphy), 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))
                ieee80211_sta_ps_deliver_poll_response(sta);
}

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;
        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);

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

        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. refer to
                 * sta_rx_agg_session_timer_expired for useage */
                sta->timer_to_tid[i] = i;
                /* rx */
                sta->ampdu_mlme.tid_state_rx[i] = HT_AGG_STATE_IDLE;
                sta->ampdu_mlme.tid_rx[i] = NULL;
                /* tx */
                sta->ampdu_mlme.tid_state_tx[i] = HT_AGG_STATE_IDLE;
                sta->ampdu_mlme.tid_tx[i] = NULL;
                sta->ampdu_mlme.addba_req_num[i] = 0;
        }
        skb_queue_head_init(&sta->ps_tx_buf);
        skb_queue_head_init(&sta->tx_filtered);

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

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

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

        return sta;
}

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

        WARN_ON(!mutex_is_locked(&local->sta_mtx));

        /* 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)
                        printk(KERN_DEBUG "%s: Finished adding IBSS STA %pM\n",
                               wiphy_name(local->hw.wiphy), sta->sta.addr);
#endif
        }

        sdata = sta->sdata;

        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);

        ieee80211_sta_debugfs_add(sta);
        rate_control_add_sta_debugfs(sta);

        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);

                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);
}

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;
        unsigned long flags;
        int err = 0;

        /*
         * 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))) {
                err = -ENETDOWN;
                rcu_read_lock();
                goto out_free;
        }

        if (WARN_ON(compare_ether_addr(sta->sta.addr, sdata->vif.addr) == 0 ||
                    is_multicast_ether_addr(sta->sta.addr))) {
                err = -EINVAL;
                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) {
                spin_lock_irqsave(&local->sta_lock, flags);
                /* check if STA exists already */
                if (sta_info_get_bss(sdata, sta->sta.addr)) {
                        spin_unlock_irqrestore(&local->sta_lock, flags);
                        rcu_read_lock();
                        err = -EEXIST;
                        goto out_free;
                }

                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
                printk(KERN_DEBUG "%s: Added IBSS STA %pM\n",
                       wiphy_name(local->hw.wiphy), sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */

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

                return 0;
        }

        /*
         * On first glance, this will look racy, because the code
         * below this point, 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. It still seems to race against the
         * above code 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);

        spin_lock_irqsave(&local->sta_lock, flags);
        /* check if STA exists already */
        if (sta_info_get_bss(sdata, sta->sta.addr)) {
                spin_unlock_irqrestore(&local->sta_lock, flags);
                rcu_read_lock();
                err = -EEXIST;
                goto out_free;
        }

        spin_unlock_irqrestore(&local->sta_lock, flags);

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

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
        printk(KERN_DEBUG "%s: Inserted STA %pM\n",
               wiphy_name(local->hw.wiphy), 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;
 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;
}

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 void __sta_info_set_tim_bit(struct ieee80211_if_ap *bss,
                                   struct sta_info *sta)
{
        BUG_ON(!bss);

        __bss_tim_set(bss, sta->sta.aid);

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

void sta_info_set_tim_bit(struct sta_info *sta)
{
        unsigned long flags;

        BUG_ON(!sta->sdata->bss);

        spin_lock_irqsave(&sta->local->sta_lock, flags);
        __sta_info_set_tim_bit(sta->sdata->bss, sta);
        spin_unlock_irqrestore(&sta->local->sta_lock, flags);
}

static void __sta_info_clear_tim_bit(struct ieee80211_if_ap *bss,
                                     struct sta_info *sta)
{
        BUG_ON(!bss);

        __bss_tim_clear(bss, sta->sta.aid);

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

void sta_info_clear_tim_bit(struct sta_info *sta)
{
        unsigned long flags;

        BUG_ON(!sta->sdata->bss);

        spin_lock_irqsave(&sta->local->sta_lock, flags);
        __sta_info_clear_tim_bit(sta->sdata->bss, sta);
        spin_unlock_irqrestore(&sta->local->sta_lock, flags);
}

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

        if (!skb)
                return 0;

        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 void sta_info_cleanup_expire_buffered(struct ieee80211_local *local,
                                             struct sta_info *sta)
{
        unsigned long flags;
        struct sk_buff *skb;
        struct ieee80211_sub_if_data *sdata;

        if (skb_queue_empty(&sta->ps_tx_buf))
                return;

        for (;;) {
                spin_lock_irqsave(&sta->ps_tx_buf.lock, flags);
                skb = skb_peek(&sta->ps_tx_buf);
                if (sta_info_buffer_expired(sta, skb))
                        skb = __skb_dequeue(&sta->ps_tx_buf);
                else
                        skb = NULL;
                spin_unlock_irqrestore(&sta->ps_tx_buf.lock, flags);

                if (!skb)
                        break;

                sdata = sta->sdata;
                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);

                if (skb_queue_empty(&sta->ps_tx_buf))
                        sta_info_clear_tim_bit(sta);
        }
}

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

        might_sleep();

        if (!sta)
                return -ENOENT;

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

        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;

        if (sta->key) {
                ieee80211_key_free(sta->key);
                /*
                 * We have only unlinked the key, and actually destroying it
                 * may mean it is removed from hardware which requires that
                 * the key->sta pointer is still valid, so flush the key todo
                 * list here.
                 *
                 * ieee80211_key_todo() will synchronize_rcu() so after this
                 * nothing can reference this sta struct any more.
                 */
                ieee80211_key_todo();

                WARN_ON(sta->key);
        }

        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_clear_tim_bit(sdata->bss, 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;
        }

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

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

        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

        while ((skb = skb_dequeue(&sta->ps_tx_buf)) != NULL) {
                local->total_ps_buffered--;
                dev_kfree_skb_any(skb);
        }

        while ((skb = skb_dequeue(&sta->tx_filtered)) != NULL)
                dev_kfree_skb_any(skb);

        for (i = 0; i <  STA_TID_NUM; i++) {
                struct tid_ampdu_rx *tid_rx;
                struct tid_ampdu_tx *tid_tx;

                spin_lock_bh(&sta->lock);
                tid_rx = sta->ampdu_mlme.tid_rx[i];
                /* Make sure timer won't free the tid_rx struct, see below */
                if (tid_rx)
                        tid_rx->shutdown = true;

                spin_unlock_bh(&sta->lock);

                /*
                 * Outside spinlock - shutdown is true now so that the timer
                 * won't free tid_rx, we have to do that now. Can't let the
                 * timer do it because we have to sync the timer outside the
                 * lock that it takes itself.
                 */
                if (tid_rx) {
                        del_timer_sync(&tid_rx->session_timer);
                        kfree(tid_rx);
                }

                /*
                 * No need to do such complications for TX agg sessions, the
                 * path leading to freeing the tid_tx struct goes via a call
                 * from the driver, and thus needs to look up the sta struct
                 * again, which cannot be found when we get here. Hence, we
                 * just need to delete the timer and free the aggregation
                 * info; we won't be telling the peer about it then but that
                 * doesn't matter if we're not talking to it again anyway.
                 */
                tid_tx = sta->ampdu_mlme.tid_tx[i];
                if (tid_tx) {
                        del_timer_sync(&tid_tx->addba_resp_timer);
                        /*
                         * STA removed while aggregation session being
                         * started? Bit odd, but purge frames anyway.
                         */
                        skb_queue_purge(&tid_tx->pending);
                        kfree(tid_tx);
                }
        }

        __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(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(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;

        rcu_read_lock();
        list_for_each_entry_rcu(sta, &local->sta_list, list)
                sta_info_cleanup_expire_buffered(local, sta);
        rcu_read_unlock();

        if (local->quiescing)
                return;

        local->sta_cleanup.expires =
                round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL);
        add_timer(&local->sta_cleanup);
}

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);
        local->sta_cleanup.expires =
                round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL);
}

int sta_info_start(struct ieee80211_local *local)
{
        add_timer(&local->sta_cleanup);
        return 0;
}

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_hw(struct ieee80211_hw *hw,
                                               const u8 *addr)
{
        struct sta_info *sta, *nxt;

        /* Just return a random station ... first in list ... */
        for_each_sta_info(hw_to_local(hw), addr, sta, nxt)
                return &sta->sta;
        return NULL;
}
EXPORT_SYMBOL_GPL(ieee80211_find_sta_by_hw);

struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_vif *vif,
                                         const u8 *addr)
{
        struct ieee80211_sub_if_data *sdata;

        if (!vif)
                return NULL;

        sdata = vif_to_sdata(vif);

        return ieee80211_find_sta_by_hw(&sdata->local->hw, addr);
}
EXPORT_SYMBOL(ieee80211_find_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;
        int sent, buffered;

        drv_sta_notify(local, sdata, STA_NOTIFY_AWAKE, &sta->sta);

        if (!skb_queue_empty(&sta->ps_tx_buf))
                sta_info_clear_tim_bit(sta);

        /* Send all buffered frames to the station */
        sent = ieee80211_add_pending_skbs(local, &sta->tx_filtered);
        buffered = ieee80211_add_pending_skbs(local, &sta->ps_tx_buf);
        sent += buffered;
        local->total_ps_buffered -= buffered;

#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, sent - buffered, buffered);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}

void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
{
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        struct ieee80211_local *local = sdata->local;
        struct sk_buff *skb;
        int no_pending_pkts;

        skb = skb_dequeue(&sta->tx_filtered);
        if (!skb) {
                skb = skb_dequeue(&sta->ps_tx_buf);
                if (skb)
                        local->total_ps_buffered--;
        }
        no_pending_pkts = skb_queue_empty(&sta->tx_filtered) &&
                skb_queue_empty(&sta->ps_tx_buf);

        if (skb) {
                struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
                struct ieee80211_hdr *hdr =
                        (struct ieee80211_hdr *) 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_PSPOLL_RESPONSE;

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
                printk(KERN_DEBUG "STA %pM aid %d: PS Poll (entries after %d)\n",
                       sta->sta.addr, sta->sta.aid,
                       skb_queue_len(&sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

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

                ieee80211_add_pending_skb(local, skb);

                if (no_pending_pkts)
                        sta_info_clear_tim_bit(sta);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
        } else {
                /*
                 * FIXME: This can be the result of a race condition between
                 *        us expiring a frame and the station polling for it.
                 *        Should we send it a null-func frame indicating we
                 *        have nothing buffered for it?
                 */
                printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
                       "though there are no buffered frames for it\n",
                       sdata->name, sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
        }
}

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);

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