path: root/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 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)],
				    rcu_read_lock_held() ||
				    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,
					    rcu_read_lock_held() ||
					    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)],
				    rcu_read_lock_held() ||
				    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,
					    rcu_read_lock_held() ||
					    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 S