sta_info.c

/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2006-2007	Jiri Benc <jbenc@suse.cz>
 * Copyright 2013-2014  Intel Mobile Communications GmbH
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/etherdevice.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.
 */

static const struct rhashtable_params sta_rht_params = {
	.nelem_hint = 3, /* start small */
	.head_offset = offsetof(struct sta_info, hash_node),
	.key_offset = offsetof(struct sta_info, sta.addr),
	.key_len = ETH_ALEN,
	.hashfn = sta_addr_hash,
};

/* Caller must hold local->sta_mtx */
static int sta_info_hash_del(struct ieee80211_local *local,
			     struct sta_info *sta)
{
	return rhashtable_remove_fast(&local->sta_hash, &sta->hash_node,
				      sta_rht_params);
}

static void __cleanup_single_sta(struct sta_info *sta)
{
	int ac, i;
	struct tid_ampdu_tx *tid_tx;
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	struct ieee80211_local *local = sdata->local;
	struct ps_data *ps;

	if (test_sta_flag(sta, WLAN_STA_PS_STA) ||
	    test_sta_flag(sta, WLAN_STA_PS_DRIVER) ||
	    test_sta_flag(sta, WLAN_STA_PS_DELIVER)) {
		if (sta->sdata->vif.type == NL80211_IFTYPE_AP ||
		    sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
			ps = &sdata->bss->ps;
		else if (ieee80211_vif_is_mesh(&sdata->vif))
			ps = &sdata->u.mesh.ps;
		else
			return;

		clear_sta_flag(sta, WLAN_STA_PS_STA);
		clear_sta_flag(sta, WLAN_STA_PS_DRIVER);
		clear_sta_flag(sta, WLAN_STA_PS_DELIVER);

		atomic_dec(&ps->num_sta_ps);
	}

	if (sta->sta.txq[0]) {
		for (i = 0; i < ARRAY_SIZE(sta->sta.txq); i++) {
			struct txq_info *txqi = to_txq_info(sta->sta.txq[i]);
			int n = skb_queue_len(&txqi->queue);

			ieee80211_purge_tx_queue(&local->hw, &txqi->queue);
			atomic_sub(n, &sdata->txqs_len[txqi->txq.ac]);
		}
	}

	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
		local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);
		ieee80211_purge_tx_queue(&local->hw, &sta->ps_tx_buf[ac]);
		ieee80211_purge_tx_queue(&local->hw, &sta->tx_filtered[ac]);
	}

	if (ieee80211_vif_is_mesh(&sdata->vif))
		mesh_sta_cleanup(sta);

	cancel_work_sync(&sta->drv_deliver_wk);

	/*
	 * Destroy aggregation state here. It would be nice to wait for the
	 * driver to finish aggregation stop and then clean up, but for now
	 * drivers have to handle aggregation stop being requested, followed
	 * directly by station destruction.
	 */
	for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
		kfree(sta->ampdu_mlme.tid_start_tx[i]);
		tid_tx = rcu_dereference_raw(sta->ampdu_mlme.tid_tx[i]);
		if (!tid_tx)
			continue;
		ieee80211_purge_tx_queue(&local->hw, &tid_tx->pending);
		kfree(tid_tx);
	}
}

static void cleanup_single_sta(struct sta_info *sta)
{
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	struct ieee80211_local *local = sdata->local;

	__cleanup_single_sta(sta);
	sta_info_free(local, sta);
}

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

	return rhashtable_lookup_fast(&local->sta_hash, addr, sta_rht_params);
}

/*
 * 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;
	struct rhash_head *tmp;
	const struct bucket_table *tbl;

	rcu_read_lock();
	tbl = rht_dereference_rcu(local->sta_hash.tbl, &local->sta_hash);

	for_each_sta_info(local, tbl, addr, sta, tmp) {
		if (sta->sdata == sdata ||
		    (sta->sdata->bss && sta->sdata->bss == sdata->bss)) {
			rcu_read_unlock();
			/* this is safe as the caller must already hold
			 * another rcu read section or the mutex
			 */
			return sta;
		}
	}
	rcu_read_unlock();
	return NULL;
}

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 - free STA
 *
 * @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(). It may only be
 * called when sta_info_insert() has not been attempted (and
 * if that fails, the station is freed anyway.)
 */
void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
{
	if (sta->rate_ctrl)
		rate_control_free_sta(sta);

	sta_dbg(sta->sdata, "Destroyed STA %pM\n", sta->sta.addr);

	if (sta->sta.txq[0])
		kfree(to_txq_info(sta->sta.txq[0]));
	kfree(rcu_dereference_raw(sta->sta.rates));
	kfree(sta);
}

/* Caller must hold local->sta_mtx */
static void sta_info_hash_add(struct ieee80211_local *local,
			      struct sta_info *sta)
{
	rhashtable_insert_fast(&local->sta_hash, &sta->hash_node,
			       sta_rht_params);
}

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

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

	if (sta->dead)
		return;

	local_bh_disable();
	if (!test_sta_flag(sta, WLAN_STA_PS_STA))
		ieee80211_sta_ps_deliver_wakeup(sta);
	else if (test_and_clear_sta_flag(sta, WLAN_STA_PSPOLL))
		ieee80211_sta_ps_deliver_poll_response(sta);
	else if (test_and_clear_sta_flag(sta, WLAN_STA_UAPSD))
		ieee80211_sta_ps_deliver_uapsd(sta);
	local_bh_enable();
}

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

	return 0;
}

struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
				const u8 *addr, gfp_t gfp)
{
	struct ieee80211_local *local = sdata->local;
	struct ieee80211_hw *hw = &local->hw;
	struct sta_info *sta;
	struct timespec uptime;
	int i;

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

	spin_lock_init(&sta->lock);
	spin_lock_init(&sta->ps_lock);
	INIT_WORK(&sta->drv_deliver_wk, sta_deliver_ps_frames);
	INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);
	mutex_init(&sta->ampdu_mlme.mtx);
#ifdef CONFIG_MAC80211_MESH
	spin_lock_init(&sta->plink_lock);
	if (ieee80211_vif_is_mesh(&sdata->vif) &&
	    !sdata->u.mesh.user_mpm)
		init_timer(&sta->plink_timer);
	sta->nonpeer_pm = NL80211_MESH_POWER_ACTIVE;
#endif

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

	sta->sta_state = IEEE80211_STA_NONE;

	/* Mark TID as unreserved */
	sta->reserved_tid = IEEE80211_TID_UNRESERVED;

	ktime_get_ts(&uptime);
	sta->last_connected = uptime.tv_sec;
	ewma_init(&sta->avg_signal, 1024, 8);
	for (i = 0; i < ARRAY_SIZE(sta->chain_signal_avg); i++)
		ewma_init(&sta->chain_signal_avg[i], 1024, 8);

	if (local->ops->wake_tx_queue) {
		void *txq_data;
		int size = sizeof(struct txq_info) +
			   ALIGN(hw->txq_data_size, sizeof(void *));

		txq_data = kcalloc(ARRAY_SIZE(sta->sta.txq), size, gfp);
		if (!txq_data)
			goto free;

		for (i = 0; i < ARRAY_SIZE(sta->sta.txq); i++) {
			struct txq_info *txq = txq_data + i * size;

			ieee80211_init_tx_queue(sdata, sta, txq, i);
		}
	}

	if (sta_prepare_rate_control(local, sta, gfp))
		goto free_txq;

	for (i = 0; i < IEEE80211_NUM_TIDS; 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 < IEEE80211_NUM_TIDS; i++)
		sta->last_seq_ctrl[i] = cpu_to_le16(USHRT_MAX);

	sta->sta.smps_mode = IEEE80211_SMPS_OFF;
	if (sdata->vif.type == NL80211_IFTYPE_AP ||
	    sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
		struct ieee80211_supported_band *sband =
			hw->wiphy->bands[ieee80211_get_sdata_band(sdata)];
		u8 smps = (sband->ht_cap.cap & IEEE80211_HT_CAP_SM_PS) >>
				IEEE80211_HT_CAP_SM_PS_SHIFT;
		/*
		 * Assume that hostapd advertises our caps in the beacon and
		 * this is the known_smps_mode for a station that just assciated
		 */
		switch (smps) {
		case WLAN_HT_SMPS_CONTROL_DISABLED:
			sta->known_smps_mode = IEEE80211_SMPS_OFF;
			break;
		case WLAN_HT_SMPS_CONTROL_STATIC:
			sta->known_smps_mode = IEEE80211_SMPS_STATIC;
			break;
		case WLAN_HT_SMPS_CONTROL_DYNAMIC:
			sta->known_smps_mode = IEEE80211_SMPS_DYNAMIC;
			break;
		default:
			WARN_ON(1);
		}
	}

	sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr);

	return sta;

free_txq:
	if (sta->sta.txq[0])
		kfree(to_txq_info(sta->sta.txq[0]));
free:
	kfree(sta);
	return NULL;
}

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(ether_addr_equal(sta->sta.addr, sdata->vif.addr) ||
		    is_multicast_ether_addr(sta->sta.addr)))
		return -EINVAL;

	return 0;
}

static int sta_info_insert_drv_state(struct ieee80211_local *local,
				     struct ieee80211_sub_if_data *sdata,
				     struct sta_info *sta)
{
	enum ieee80211_sta_state state;
	int err = 0;

	for (state = IEEE80211_STA_NOTEXIST; state < sta->sta_state; state++) {
		err = drv_sta_state(local, sdata, sta, state, state + 1);
		if (err)
			break;
	}

	if (!err) {
		/*
		 * Drivers using legacy sta_add/sta_remove callbacks only
		 * get uploaded set to true after sta_add is called.
		 */
		if (!local->ops->sta_add)
			sta->uploaded = true;
		return 0;
	}

	if (sdata->vif.type == NL80211_IFTYPE_ADHOC) {
		sdata_info(sdata,
			   "failed to move IBSS STA %pM to state %d (%d) - keeping it anyway\n",
			   sta->sta.addr, state + 1, err);
		err = 0;
	}

	/* unwind on error */
	for (; state > IEEE80211_STA_NOTEXIST; state--)
		WARN_ON(drv_sta_state(local, sdata, sta, state, state - 1));

	return err;
}

/*
 * should be called with sta_mtx locked
 * this function replaces the mutex lock
 * with a RCU lock
 */
static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
{
	struct ieee80211_local *local = sta->local;
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	struct station_info sinfo;
	int err = 0;

	lockdep_assert_held(&local->sta_mtx);

	/* check if STA exists already */
	if (sta_info_get_bss(sdata, sta->sta.addr)) {
		err = -EEXIST;
		goto out_err;
	}

	local->num_sta++;
	local->sta_generation++;
	smp_mb();

	/* simplify things and don't accept BA sessions yet */
	set_sta_flag(sta, WLAN_STA_BLOCK_BA);

	/* make the station visible */
	sta_info_hash_add(local, sta);

	list_add_tail_rcu(&sta->list, &local->sta_list);

	/* notify driver */
	err = sta_info_insert_drv_state(local, sdata, sta);
	if (err)
		goto out_remove;

	set_sta_flag(sta, WLAN_STA_INSERTED);
	/* accept BA sessions now */
	clear_sta_flag(sta, WLAN_STA_BLOCK_BA);

	ieee80211_recalc_min_chandef(sdata);
	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);

	sta_dbg(sdata, "Inserted STA %pM\n", sta->sta.addr);

	/* 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_remove:
	sta_info_hash_del(local, sta);
	list_del_rcu(&sta->list);
	local->num_sta--;
	synchronize_net();
	__cleanup_single_sta(sta);
 out_err:
	mutex_unlock(&local->sta_mtx);
	rcu_read_lock();
	return err;
}

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

	might_sleep();

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

	mutex_lock(&local->sta_mtx);

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

	return 0;
 out_free:
	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(u8 *tim, u16 id)
{
	/*
	 * This format has been mandated by the IEEE specifications,
	 * so this line may not be changed to use the __set_bit() format.
	 */
	tim[id / 8] |= (1 << (id % 8));
}

static inline void __bss_tim_clear(u8 *tim, u16 id)
{
	/*
	 * This format has been mandated by the IEEE specifications,
	 * so this line may not be changed to use the __clear_bit() format.
	 */
	tim[id / 8] &= ~(1 << (id % 8));
}

static inline bool __bss_tim_get(u8 *tim, u16 id)
{
	/*
	 * This format has been mandated by the IEEE specifications,
	 * so this line may not be changed to use the test_bit() format.
	 */
	return tim[id / 8] & (1 << (id % 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;
	}
}

static void __sta_info_recalc_tim(struct sta_info *sta, bool ignore_pending)
{
	struct ieee80211_local *local = sta->local;
	struct ps_data *ps;
	bool indicate_tim = false;
	u8 ignore_for_tim = sta->sta.uapsd_queues;
	int ac;
	u16 id;

	if (sta->sdata->vif.type == NL80211_IFTYPE_AP ||
	    sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
		if (WARN_ON_ONCE(!sta->sdata->bss))
			return;

		ps = &sta->sdata->bss->ps;
		id = sta->sta.aid;
#ifdef CONFIG_MAC80211_MESH
	} else if (ieee80211_vif_is_mesh(&sta->sdata->vif)) {
		ps = &sta->sdata->u.mesh.ps;
		/* TIM map only for 1 <= PLID <= IEEE80211_MAX_AID */
		id = sta->plid % (IEEE80211_MAX_AID + 1);
#endif
	} else {
		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;

	if (ignore_pending)
		ignore_for_tim = BIT(IEEE80211_NUM_ACS) - 1;

	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;
		indicate_tim |=
			sta->txq_buffered_tids & tids;
	}

 done:
	spin_lock_bh(&local->tim_lock);

	if (indicate_tim == __bss_tim_get(ps->tim, id))
		goto out_unlock;

	if (indicate_tim)
		__bss_tim_set(ps->tim, id);
	else
		__bss_tim_clear(ps->tim, id);

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

out_unlock:
	spin_unlock_bh(&local->tim_lock);
}

void sta_info_recalc_tim(struct sta_info *sta)
{
	__sta_info_recalc_tim(sta, false);
}

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;
		ieee80211_free_txskb(&local->hw, 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--;
		ps_dbg(sta->sdata, "Buffered frame expired (STA %pM)\n",
		       sta->sta.addr);
		ieee80211_free_txskb(&local->hw, 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/MBSS interfaces */
	if (!sta->sdata->bss &&
	    !ieee80211_vif_is_mesh(&sta->sdata->vif))
		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_part1(struct sta_info *sta)
{
	struct ieee80211_local *local;
	struct ieee80211_sub_if_data *sdata;
	int ret;

	might_sleep();

	if (!sta)
		return -ENOENT;

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

	lockdep_assert_held(&local->sta_mtx);

	/*
	 * 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_flag(sta, WLAN_STA_BLOCK_BA);
	ieee80211_sta_tear_down_BA_sessions(sta, AGG_STOP_DESTROY_STA);

	ret = sta_info_hash_del(local, sta);
	if (WARN_ON(ret))
		return ret;

	/*
	 * for TDLS peers, make sure to return to the base channel before
	 * removal.
	 */
	if (test_sta_flag(sta, WLAN_STA_TDLS_OFF_CHANNEL)) {
		drv_tdls_cancel_channel_switch(local, sdata, &sta->sta);
		clear_sta_flag(sta, WLAN_STA_TDLS_OFF_CHANNEL);
	}

	list_del_rcu(&sta->list);

	drv_sta_pre_rcu_remove(local, sta->sdata, sta);

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

	return 0;
}

static void __sta_info_destroy_part2(struct sta_info *sta)
{
	struct ieee80211_local *local = sta->local;
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	struct station_info sinfo = {};
	int ret;

	/*
	 * NOTE: This assumes at least synchronize_net() was done
	 *	 after _part1 and before _part2!
	 */

	might_sleep();
	lockdep_assert_held(&local->sta_mtx);

	/* now keys can no longer be reached */
	ieee80211_free_sta_keys(local, sta);

	/* disable TIM bit - last chance to tell driver */
	__sta_info_recalc_tim(sta, true);

	sta->dead = true;

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

	while (sta->sta_state > IEEE80211_STA_NONE) {
		ret = sta_info_move_state(sta, sta->sta_state - 1);
		if (ret) {
			WARN_ON_ONCE(1);
			break;
		}
	}

	if (sta->uploaded) {
		ret = drv_sta_state(local, sdata, sta, IEEE80211_STA_NONE,
				    IEEE80211_STA_NOTEXIST);
		WARN_ON_ONCE(ret != 0);
	}

	sta_dbg(sdata, "Removed STA %pM\n", sta->sta.addr);

	sta_set_sinfo(sta, &sinfo);
	cfg80211_del_sta_sinfo(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);

	rate_control_remove_sta_debugfs(sta);
	ieee80211_sta_debugfs_remove(sta);
	ieee80211_recalc_min_chandef(sdata);

	cleanup_single_sta(sta);
}

int __must_check __sta_info_destroy(struct sta_info *sta)
{
	int err = __sta_info_destroy_part1(sta);

	if (err)
		return err;

	synchronize_net();

	__sta_info_destroy_part2(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;
	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));
}

u32 sta_addr_hash(const void *key, u32 length, u32 seed)
{
	return jhash(key, ETH_ALEN, seed);
}

int sta_info_init(struct ieee80211_local *local)
{
	int err;

	err = rhashtable_init(&local->sta_hash, &sta_rht_params);
	if (err)
		return err;

	spin_lock_init(&local->tim_lock);
	mutex_init(&local->sta_mtx);
	INIT_LIST_HEAD(&local->sta_list);

	setup_timer(&local->sta_cleanup, sta_info_cleanup,
		    (unsigned long)local);
	return 0;
}

void sta_info_stop(struct ieee80211_local *local)
{