mac80211: clean up sta_info and document locking

[mirror_ubuntu-artful-kernel.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 "ieee80211_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() or
 * mesh_plink_alloc(), the caller owns that structure. It must then either
 * destroy it using @sta_info_destroy() (which is pretty useless) or insert
 * it into the hash table using @sta_info_insert() which demotes the reference
 * from ownership to a regular RCU-protected reference; if the function
 * is called without protection by an RCU critical section the reference
 * is instantly invalidated.
 *
 * Because there are debugfs entries for each station, and adding those
 * must be able to sleep, it is also possible to "pin" a station entry,
 * that means it can be removed from the hash table but not be freed.
 * See the comment in @__sta_info_unlink() for more information.
 *
 * In order to remove a STA info structure, the caller needs to first
 * unlink it (@sta_info_unlink()) from the list and hash tables and
 * then wait for an RCU synchronisation before it can be freed. Due to
 * the pinning and the possibility of multiple callers trying to remove
 * the same STA info at the same time, @sta_info_unlink() can clear the
 * STA info pointer it is passed to indicate that the STA info is owned
 * by somebody else now.
 *
 * If @sta_info_unlink() did not clear the pointer then the caller owns
 * the STA info structure now and is responsible of destroying it with
 * a call to @sta_info_destroy(), not before RCU synchronisation, of
 * course. Note that sta_info_destroy() must be protected by the RTNL.
 *
 * In all other cases, 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->addr)];
	if (!s)
		return -ENOENT;
	if (s == sta) {
		rcu_assign_pointer(local->sta_hash[STA_HASH(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 */
static struct sta_info *__sta_info_find(struct ieee80211_local *local,
					u8 *addr)
{
	struct sta_info *sta;

	sta = rcu_dereference(local->sta_hash[STA_HASH(addr)]);
	while (sta) {
		if (compare_ether_addr(sta->addr, addr) == 0)
			break;
		sta = rcu_dereference(sta->hnext);
	}
	return sta;
}

struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr)
{
	return __sta_info_find(local, addr);
}
EXPORT_SYMBOL(sta_info_get);

struct sta_info *sta_info_get_by_idx(struct ieee80211_local *local, int idx,
				     struct net_device *dev)
{
	struct sta_info *sta;
	int i = 0;

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

	return NULL;
}

void sta_info_destroy(struct sta_info *sta)
{
	struct ieee80211_local *local = sta->local;
	struct sk_buff *skb;
	int i;
	DECLARE_MAC_BUF(mbuf);

	if (!sta)
		return;

	ASSERT_RTNL();
	might_sleep();

	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);
#endif

	/*
	 * NOTE: This will call synchronize_rcu() internally to
	 * make sure no key references can be in use. We rely on
	 * that here for the mesh code!
	 */
	ieee80211_key_free(sta->key);
	WARN_ON(sta->key);

#ifdef CONFIG_MAC80211_MESH
	if (ieee80211_vif_is_mesh(&sta->sdata->vif))
		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++) {
		del_timer_sync(&sta->ampdu_mlme.tid_rx[i].session_timer);
		del_timer_sync(&sta->ampdu_mlme.tid_tx[i].addba_resp_timer);
	}
	rate_control_free_sta(sta->rate_ctrl, sta->rate_ctrl_priv);
	rate_control_put(sta->rate_ctrl);

#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
	printk(KERN_DEBUG "%s: Destroyed STA %s\n",
	       wiphy_name(local->hw.wiphy), print_mac(mbuf, 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->addr)];
	rcu_assign_pointer(local->sta_hash[STA_HASH(sta->addr)], sta);
}

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;
	DECLARE_MAC_BUF(mbuf);

	sta = kzalloc(sizeof(*sta), gfp);
	if (!sta)
		return NULL;

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

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

	spin_lock_init(&sta->ampdu_mlme.ampdu_rx);
	spin_lock_init(&sta->ampdu_mlme.ampdu_tx);
	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;
		/* tid to tx queue: initialize according to HW (0 is valid) */
		sta->tid_to_tx_q[i] = local->hw.queues;
		/* rx timers */
		sta->ampdu_mlme.tid_rx[i].session_timer.function =
			sta_rx_agg_session_timer_expired;
		sta->ampdu_mlme.tid_rx[i].session_timer.data =
			(unsigned long)&sta->timer_to_tid[i];
		init_timer(&sta->ampdu_mlme.tid_rx[i].session_timer);
		/* tx timers */
		sta->ampdu_mlme.tid_tx[i].addba_resp_timer.function =
			sta_addba_resp_timer_expired;
		sta->ampdu_mlme.tid_tx[i].addba_resp_timer.data =
			(unsigned long)&sta->timer_to_tid[i];
		init_timer(&sta->ampdu_mlme.tid_tx[i].addba_resp_timer);
	}
	skb_queue_head_init(&sta->ps_tx_buf);
	skb_queue_head_init(&sta->tx_filtered);

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

	return sta;
}

int sta_info_insert(struct sta_info *sta)
{
	struct ieee80211_local *local = sta->local;
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	unsigned long flags;
	DECLARE_MAC_BUF(mac);

	spin_lock_irqsave(&local->sta_lock, flags);
	/* check if STA exists already */
	if (__sta_info_find(local, sta->addr)) {
		spin_unlock_irqrestore(&local->sta_lock, flags);
		return -EEXIST;
	}
	list_add(&sta->list, &local->sta_list);
	local->num_sta++;
	sta_info_hash_add(local, sta);

	/* notify driver */
	if (local->ops->sta_notify) {
		if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN)
			sdata = sdata->u.vlan.ap;

		local->ops->sta_notify(local_to_hw(local), &sdata->vif,
				       STA_NOTIFY_ADD, sta->addr);
	}

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

	spin_unlock_irqrestore(&local->sta_lock, flags);

#ifdef CONFIG_MAC80211_DEBUGFS
	/* debugfs entry adding might sleep, so schedule process
	 * context task for adding entry for STAs that do not yet
	 * have one. */
	queue_work(local->hw.workqueue, &local->sta_debugfs_add);
#endif

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

	return 0;
}

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)
{
	if (bss)
		__bss_tim_set(bss, sta->aid);
	if (sta->local->ops->set_tim) {
		sta->local->tim_in_locked_section = true;
		sta->local->ops->set_tim(local_to_hw(sta->local), sta->aid, 1);
		sta->local->tim_in_locked_section = false;
	}
}

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

	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)
{
	if (bss)
		__bss_tim_clear(bss, sta->aid);
	if (sta->local->ops->set_tim) {
		sta->local->tim_in_locked_section = true;
		sta->local->ops->set_tim(local_to_hw(sta->local), sta->aid, 0);
		sta->local->tim_in_locked_section = false;
	}
}

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

	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);
}

/*
 * See comment in __sta_info_unlink,
 * caller must hold local->sta_lock.
 */
static void __sta_info_pin(struct sta_info *sta)
{
	WARN_ON(sta->pin_status != STA_INFO_PIN_STAT_NORMAL);
	sta->pin_status = STA_INFO_PIN_STAT_PINNED;
}

/*
 * See comment in __sta_info_unlink, returns sta if it
 * needs to be destroyed.
 */
static struct sta_info *__sta_info_unpin(struct sta_info *sta)
{
	struct sta_info *ret = NULL;
	unsigned long flags;

	spin_lock_irqsave(&sta->local->sta_lock, flags);
	WARN_ON(sta->pin_status != STA_INFO_PIN_STAT_DESTROY &&
		sta->pin_status != STA_INFO_PIN_STAT_PINNED);
	if (sta->pin_status == STA_INFO_PIN_STAT_DESTROY)
		ret = sta;
	sta->pin_status = STA_INFO_PIN_STAT_NORMAL;
	spin_unlock_irqrestore(&sta->local->sta_lock, flags);

	return ret;
}

static void __sta_info_unlink(struct sta_info **sta)
{
	struct ieee80211_local *local = (*sta)->local;
	struct ieee80211_sub_if_data *sdata = (*sta)->sdata;
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
	DECLARE_MAC_BUF(mbuf);
#endif
	/*
	 * pull caller's reference if we're already gone.
	 */
	if (sta_info_hash_del(local, *sta)) {
		*sta = NULL;
		return;
	}

	/*
	 * Also pull caller's reference if the STA is pinned by the
	 * task that is adding the debugfs entries. In that case, we
	 * leave the STA "to be freed".
	 *
	 * The rules are not trivial, but not too complex either:
	 *  (1) pin_status is only modified under the sta_lock
	 *  (2) sta_info_debugfs_add_work() will set the status
	 *	to PINNED when it found an item that needs a new
	 *	debugfs directory created. In that case, that item
	 *	must not be freed although all *RCU* users are done
	 *	with it. Hence, we tell the caller of _unlink()
	 *	that the item is already gone (as can happen when
	 *	two tasks try to unlink/destroy at the same time)
	 *  (3) We set the pin_status to DESTROY here when we
	 *	find such an item.
	 *  (4) sta_info_debugfs_add_work() will reset the pin_status
	 *	from PINNED to NORMAL when it is done with the item,
	 *	but will check for DESTROY before resetting it in
	 *	which case it will free the item.
	 */
	if ((*sta)->pin_status == STA_INFO_PIN_STAT_PINNED) {
		(*sta)->pin_status = STA_INFO_PIN_STAT_DESTROY;
		*sta = NULL;
		return;
	}

	list_del(&(*sta)->list);

	if ((*sta)->flags & WLAN_STA_PS) {
		(*sta)->flags &= ~WLAN_STA_PS;
		if (sdata->bss)
			atomic_dec(&sdata->bss->num_sta_ps);
		__sta_info_clear_tim_bit(sdata->bss, *sta);
	}

	local->num_sta--;

	if (local->ops->sta_notify) {
		if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN)
			sdata = sdata->u.vlan.ap;

		local->ops->sta_notify(local_to_hw(local), &sdata->vif,
				       STA_NOTIFY_REMOVE, (*sta)->addr);
	}

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

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

void sta_info_unlink(struct sta_info **sta)
{
	struct ieee80211_local *local = (*sta)->local;
	unsigned long flags;

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

static inline int sta_info_buffer_expired(struct ieee80211_local *local,
					  struct sta_info *sta,
					  struct sk_buff *skb)
{
	struct ieee80211_tx_packet_data *pkt_data;
	int timeout;

	if (!skb)
		return 0;

	pkt_data = (struct ieee80211_tx_packet_data *) skb->cb;

	/* Timeout: (2 * listen_interval * beacon_int * 1024 / 1000000) sec */
	timeout = (sta->listen_interval * local->hw.conf.beacon_int * 32 /
		   15625) * HZ;
	if (timeout < STA_TX_BUFFER_EXPIRE)
		timeout = STA_TX_BUFFER_EXPIRE;
	return time_after(jiffies, pkt_data->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;
	DECLARE_MAC_BUF(mac);

	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(local, 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--;
		printk(KERN_DEBUG "Buffered frame expired (STA "
		       "%s)\n", print_mac(mac, sta->addr));
		dev_kfree_skb(skb);

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


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();

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

#ifdef CONFIG_MAC80211_DEBUGFS
static void sta_info_debugfs_add_work(struct work_struct *work)
{
	struct ieee80211_local *local =
		container_of(work, struct ieee80211_local, sta_debugfs_add);
	struct sta_info *sta, *tmp;
	unsigned long flags;

	while (1) {
		sta = NULL;

		spin_lock_irqsave(&local->sta_lock, flags);
		list_for_each_entry(tmp, &local->sta_list, list) {
			if (!tmp->debugfs.dir) {
				sta = tmp;
				__sta_info_pin(sta);
				break;
			}
		}
		spin_unlock_irqrestore(&local->sta_lock, flags);

		if (!sta)
			break;

		ieee80211_sta_debugfs_add(sta);
		rate_control_add_sta_debugfs(sta);

		sta = __sta_info_unpin(sta);

		if (sta) {
			synchronize_rcu();
			sta_info_destroy(sta);
		}
	}
}
#endif

void sta_info_init(struct ieee80211_local *local)
{
	spin_lock_init(&local->sta_lock);
	INIT_LIST_HEAD(&local->sta_list);

	setup_timer(&local->sta_cleanup, sta_info_cleanup,
		    (unsigned long)local);
	local->sta_cleanup.expires =
		round_jiffies(jiffies + STA_INFO_CLEANUP_INTERVAL);

#ifdef CONFIG_MAC80211_DEBUGFS
	INIT_WORK(&local->sta_debugfs_add, sta_info_debugfs_add_work);
#endif
}

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
 * @local: local interface data
 * @sdata: matching rule for the net device (sta->dev) or %NULL to match all STAs
 */
void sta_info_flush(struct ieee80211_local *local,
		    struct ieee80211_sub_if_data *sdata)
{
	struct sta_info *sta, *tmp;
	LIST_HEAD(tmp_list);
	unsigned long flags;

	might_sleep();

	spin_lock_irqsave(&local->sta_lock, flags);
	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
		if (!sdata || sdata == sta->sdata) {
			__sta_info_unlink(&sta);
			if (sta)
				list_add_tail(&sta->list, &tmp_list);
		}
	}
	spin_unlock_irqrestore(&local->sta_lock, flags);

	synchronize_rcu();

	list_for_each_entry_safe(sta, tmp, &tmp_list, list)
		sta_info_destroy(sta);
}