net/wireless/scan.c

// SPDX-License-Identifier: GPL-2.0
/*
 * cfg80211 scan result handling
 *
 * Copyright 2008 Johannes Berg <johannes@sipsolutions.net>
 * Copyright 2013-2014  Intel Mobile Communications GmbH
 * Copyright 2016	Intel Deutschland GmbH
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/wireless.h>
#include <linux/nl80211.h>
#include <linux/etherdevice.h>
#include <net/arp.h>
#include <net/cfg80211.h>
#include <net/cfg80211-wext.h>
#include <net/iw_handler.h>
#include "core.h"
#include "nl80211.h"
#include "wext-compat.h"
#include "rdev-ops.h"

/**
 * DOC: BSS tree/list structure
 *
 * At the top level, the BSS list is kept in both a list in each
 * registered device (@bss_list) as well as an RB-tree for faster
 * lookup. In the RB-tree, entries can be looked up using their
 * channel, MESHID, MESHCONF (for MBSSes) or channel, BSSID, SSID
 * for other BSSes.
 *
 * Due to the possibility of hidden SSIDs, there's a second level
 * structure, the "hidden_list" and "hidden_beacon_bss" pointer.
 * The hidden_list connects all BSSes belonging to a single AP
 * that has a hidden SSID, and connects beacon and probe response
 * entries. For a probe response entry for a hidden SSID, the
 * hidden_beacon_bss pointer points to the BSS struct holding the
 * beacon's information.
 *
 * Reference counting is done for all these references except for
 * the hidden_list, so that a beacon BSS struct that is otherwise
 * not referenced has one reference for being on the bss_list and
 * one for each probe response entry that points to it using the
 * hidden_beacon_bss pointer. When a BSS struct that has such a
 * pointer is get/put, the refcount update is also propagated to
 * the referenced struct, this ensure that it cannot get removed
 * while somebody is using the probe response version.
 *
 * Note that the hidden_beacon_bss pointer never changes, due to
 * the reference counting. Therefore, no locking is needed for
 * it.
 *
 * Also note that the hidden_beacon_bss pointer is only relevant
 * if the driver uses something other than the IEs, e.g. private
 * data stored stored in the BSS struct, since the beacon IEs are
 * also linked into the probe response struct.
 */

/*
 * Limit the number of BSS entries stored in mac80211. Each one is
 * a bit over 4k at most, so this limits to roughly 4-5M of memory.
 * If somebody wants to really attack this though, they'd likely
 * use small beacons, and only one type of frame, limiting each of
 * the entries to a much smaller size (in order to generate more
 * entries in total, so overhead is bigger.)
 */
static int bss_entries_limit = 1000;
module_param(bss_entries_limit, int, 0644);
MODULE_PARM_DESC(bss_entries_limit,
                 "limit to number of scan BSS entries (per wiphy, default 1000)");

#define IEEE80211_SCAN_RESULT_EXPIRE	(7 * HZ)

static void bss_free(struct cfg80211_internal_bss *bss)
{
	struct cfg80211_bss_ies *ies;

	if (WARN_ON(atomic_read(&bss->hold)))
		return;

	ies = (void *)rcu_access_pointer(bss->pub.beacon_ies);
	if (ies && !bss->pub.hidden_beacon_bss)
		kfree_rcu(ies, rcu_head);
	ies = (void *)rcu_access_pointer(bss->pub.proberesp_ies);
	if (ies)
		kfree_rcu(ies, rcu_head);

	/*
	 * This happens when the module is removed, it doesn't
	 * really matter any more save for completeness
	 */
	if (!list_empty(&bss->hidden_list))
		list_del(&bss->hidden_list);

	kfree(bss);
}

static inline void bss_ref_get(struct cfg80211_registered_device *rdev,
			       struct cfg80211_internal_bss *bss)
{
	lockdep_assert_held(&rdev->bss_lock);

	bss->refcount++;
	if (bss->pub.hidden_beacon_bss) {
		bss = container_of(bss->pub.hidden_beacon_bss,
				   struct cfg80211_internal_bss,
				   pub);
		bss->refcount++;
	}
}

static inline void bss_ref_put(struct cfg80211_registered_device *rdev,
			       struct cfg80211_internal_bss *bss)
{
	lockdep_assert_held(&rdev->bss_lock);

	if (bss->pub.hidden_beacon_bss) {
		struct cfg80211_internal_bss *hbss;
		hbss = container_of(bss->pub.hidden_beacon_bss,
				    struct cfg80211_internal_bss,
				    pub);
		hbss->refcount--;
		if (hbss->refcount == 0)
			bss_free(hbss);
	}
	bss->refcount--;
	if (bss->refcount == 0)
		bss_free(bss);
}

static bool __cfg80211_unlink_bss(struct cfg80211_registered_device *rdev,
				  struct cfg80211_internal_bss *bss)
{
	lockdep_assert_held(&rdev->bss_lock);

	if (!list_empty(&bss->hidden_list)) {
		/*
		 * don't remove the beacon entry if it has
		 * probe responses associated with it
		 */
		if (!bss->pub.hidden_beacon_bss)
			return false;
		/*
		 * if it's a probe response entry break its
		 * link to the other entries in the group
		 */
		list_del_init(&bss->hidden_list);
	}

	list_del_init(&bss->list);
	rb_erase(&bss->rbn, &rdev->bss_tree);
	rdev->bss_entries--;
	WARN_ONCE((rdev->bss_entries == 0) ^ list_empty(&rdev->bss_list),
		  "rdev bss entries[%d]/list[empty:%d] corruption\n",
		  rdev->bss_entries, list_empty(&rdev->bss_list));
	bss_ref_put(rdev, bss);
	return true;
}

static void __cfg80211_bss_expire(struct cfg80211_registered_device *rdev,
				  unsigned long expire_time)
{
	struct cfg80211_internal_bss *bss, *tmp;
	bool expired = false;

	lockdep_assert_held(&rdev->bss_lock);

	list_for_each_entry_safe(bss, tmp, &rdev->bss_list, list) {
		if (atomic_read(&bss->hold))
			continue;
		if (!time_after(expire_time, bss->ts))
			continue;

		if (__cfg80211_unlink_bss(rdev, bss))
			expired = true;
	}

	if (expired)
		rdev->bss_generation++;
}

static bool cfg80211_bss_expire_oldest(struct cfg80211_registered_device *rdev)
{
	struct cfg80211_internal_bss *bss, *oldest = NULL;
	bool ret;

	lockdep_assert_held(&rdev->bss_lock);

	list_for_each_entry(bss, &rdev->bss_list, list) {
		if (atomic_read(&bss->hold))
			continue;

		if (!list_empty(&bss->hidden_list) &&
		    !bss->pub.hidden_beacon_bss)
			continue;

		if (oldest && time_before(oldest->ts, bss->ts))
			continue;
		oldest = bss;
	}

	if (WARN_ON(!oldest))
		return false;

	/*
	 * The callers make sure to increase rdev->bss_generation if anything
	 * gets removed (and a new entry added), so there's no need to also do
	 * it here.
	 */

	ret = __cfg80211_unlink_bss(rdev, oldest);
	WARN_ON(!ret);
	return ret;
}

void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev,
			   bool send_message)
{
	struct cfg80211_scan_request *request;
	struct wireless_dev *wdev;
	struct sk_buff *msg;
#ifdef CONFIG_CFG80211_WEXT
	union iwreq_data wrqu;
#endif

	ASSERT_RTNL();

	if (rdev->scan_msg) {
		nl80211_send_scan_msg(rdev, rdev->scan_msg);
		rdev->scan_msg = NULL;
		return;
	}

	request = rdev->scan_req;
	if (!request)
		return;

	wdev = request->wdev;

	/*
	 * This must be before sending the other events!
	 * Otherwise, wpa_supplicant gets completely confused with
	 * wext events.
	 */
	if (wdev->netdev)
		cfg80211_sme_scan_done(wdev->netdev);

	if (!request->info.aborted &&
	    request->flags & NL80211_SCAN_FLAG_FLUSH) {
		/* flush entries from previous scans */
		spin_lock_bh(&rdev->bss_lock);
		__cfg80211_bss_expire(rdev, request->scan_start);
		spin_unlock_bh(&rdev->bss_lock);
	}

	msg = nl80211_build_scan_msg(rdev, wdev, request->info.aborted);

#ifdef CONFIG_CFG80211_WEXT
	if (wdev->netdev && !request->info.aborted) {
		memset(&wrqu, 0, sizeof(wrqu));

		wireless_send_event(wdev->netdev, SIOCGIWSCAN, &wrqu, NULL);
	}
#endif

	if (wdev->netdev)
		dev_put(wdev->netdev);

	rdev->scan_req = NULL;
	kfree(request);

	if (!send_message)
		rdev->scan_msg = msg;
	else
		nl80211_send_scan_msg(rdev, msg);
}

void __cfg80211_scan_done(struct work_struct *wk)
{
	struct cfg80211_registered_device *rdev;

	rdev = container_of(wk, struct cfg80211_registered_device,
			    scan_done_wk);

	rtnl_lock();
	___cfg80211_scan_done(rdev, true);
	rtnl_unlock();
}

void cfg80211_scan_done(struct cfg80211_scan_request *request,
			struct cfg80211_scan_info *info)
{
	trace_cfg80211_scan_done(request, info);
	WARN_ON(request != wiphy_to_rdev(request->wiphy)->scan_req);

	request->info = *info;
	request->notified = true;
	queue_work(cfg80211_wq, &wiphy_to_rdev(request->wiphy)->scan_done_wk);
}
EXPORT_SYMBOL(cfg80211_scan_done);

void cfg80211_add_sched_scan_req(struct cfg80211_registered_device *rdev,
				 struct cfg80211_sched_scan_request *req)
{
	ASSERT_RTNL();

	list_add_rcu(&req->list, &rdev->sched_scan_req_list);
}

static void cfg80211_del_sched_scan_req(struct cfg80211_registered_device *rdev,
					struct cfg80211_sched_scan_request *req)
{
	ASSERT_RTNL();

	list_del_rcu(&req->list);
	kfree_rcu(req, rcu_head);
}

static struct cfg80211_sched_scan_request *
cfg80211_find_sched_scan_req(struct cfg80211_registered_device *rdev, u64 reqid)
{
	struct cfg80211_sched_scan_request *pos;

	WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());

	list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list) {
		if (pos->reqid == reqid)
			return pos;
	}
	return NULL;
}

/*
 * Determines if a scheduled scan request can be handled. When a legacy
 * scheduled scan is running no other scheduled scan is allowed regardless
 * whether the request is for legacy or multi-support scan. When a multi-support
 * scheduled scan is running a request for legacy scan is not allowed. In this
 * case a request for multi-support scan can be handled if resources are
 * available, ie. struct wiphy::max_sched_scan_reqs limit is not yet reached.
 */
int cfg80211_sched_scan_req_possible(struct cfg80211_registered_device *rdev,
				     bool want_multi)
{
	struct cfg80211_sched_scan_request *pos;
	int i = 0;

	list_for_each_entry(pos, &rdev->sched_scan_req_list, list) {
		/* request id zero means legacy in progress */
		if (!i && !pos->reqid)
			return -EINPROGRESS;
		i++;
	}

	if (i) {
		/* no legacy allowed when multi request(s) are active */
		if (!want_multi)
			return -EINPROGRESS;

		/* resource limit reached */
		if (i == rdev->wiphy.max_sched_scan_reqs)
			return -ENOSPC;
	}
	return 0;
}

void cfg80211_sched_scan_results_wk(struct work_struct *work)
{
	struct cfg80211_registered_device *rdev;
	struct cfg80211_sched_scan_request *req, *tmp;

	rdev = container_of(work, struct cfg80211_registered_device,
			   sched_scan_res_wk);

	rtnl_lock();
	list_for_each_entry_safe(req, tmp, &rdev->sched_scan_req_list, list) {
		if (req->report_results) {
			req->report_results = false;
			if (req->flags & NL80211_SCAN_FLAG_FLUSH) {
				/* flush entries from previous scans */
				spin_lock_bh(&rdev->bss_lock);
				__cfg80211_bss_expire(rdev, req->scan_start);
				spin_unlock_bh(&rdev->bss_lock);
				req->scan_start = jiffies;
			}
			nl80211_send_sched_scan(req,
						NL80211_CMD_SCHED_SCAN_RESULTS);
		}
	}
	rtnl_unlock();
}

void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 reqid)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
	struct cfg80211_sched_scan_request *request;

	trace_cfg80211_sched_scan_results(wiphy, reqid);
	/* ignore if we're not scanning */

	rcu_read_lock();
	request = cfg80211_find_sched_scan_req(rdev, reqid);
	if (request) {
		request->report_results = true;
		queue_work(cfg80211_wq, &rdev->sched_scan_res_wk);
	}
	rcu_read_unlock();
}
EXPORT_SYMBOL(cfg80211_sched_scan_results);

void cfg80211_sched_scan_stopped_rtnl(struct wiphy *wiphy, u64 reqid)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);

	ASSERT_RTNL();

	trace_cfg80211_sched_scan_stopped(wiphy, reqid);

	__cfg80211_stop_sched_scan(rdev, reqid, true);
}
EXPORT_SYMBOL(cfg80211_sched_scan_stopped_rtnl);

void cfg80211_sched_scan_stopped(struct wiphy *wiphy, u64 reqid)
{
	rtnl_lock();
	cfg80211_sched_scan_stopped_rtnl(wiphy, reqid);
	rtnl_unlock();
}
EXPORT_SYMBOL(cfg80211_sched_scan_stopped);

int cfg80211_stop_sched_scan_req(struct cfg80211_registered_device *rdev,
				 struct cfg80211_sched_scan_request *req,
				 bool driver_initiated)
{
	ASSERT_RTNL();

	if (!driver_initiated) {
		int err = rdev_sched_scan_stop(rdev, req->dev, req->reqid);
		if (err)
			return err;
	}

	nl80211_send_sched_scan(req, NL80211_CMD_SCHED_SCAN_STOPPED);

	cfg80211_del_sched_scan_req(rdev, req);

	return 0;
}

int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
			       u64 reqid, bool driver_initiated)
{
	struct cfg80211_sched_scan_request *sched_scan_req;

	ASSERT_RTNL();

	sched_scan_req = cfg80211_find_sched_scan_req(rdev, reqid);
	if (!sched_scan_req)
		return -ENOENT;

	return cfg80211_stop_sched_scan_req(rdev, sched_scan_req,
					    driver_initiated);
}

void cfg80211_bss_age(struct cfg80211_registered_device *rdev,
                      unsigned long age_secs)
{
	struct cfg80211_internal_bss *bss;
	unsigned long age_jiffies = msecs_to_jiffies(age_secs * MSEC_PER_SEC);

	spin_lock_bh(&rdev->bss_lock);
	list_for_each_entry(bss, &rdev->bss_list, list)
		bss->ts -= age_jiffies;
	spin_unlock_bh(&rdev->bss_lock);
}

void cfg80211_bss_expire(struct cfg80211_registered_device *rdev)
{
	__cfg80211_bss_expire(rdev, jiffies - IEEE80211_SCAN_RESULT_EXPIRE);
}

const u8 *cfg80211_find_ie_match(u8 eid, const u8 *ies, int len,
				 const u8 *match, int match_len,
				 int match_offset)
{
	const struct element *elem;

	/* match_offset can't be smaller than 2, unless match_len is
	 * zero, in which case match_offset must be zero as well.
	 */
	if (WARN_ON((match_len && match_offset < 2) ||
		    (!match_len && match_offset)))
		return NULL;

	for_each_element_id(elem, eid, ies, len) {
		if (elem->datalen >= match_offset - 2 + match_len &&
		    !memcmp(elem->data + match_offset - 2, match, match_len))
			return (void *)elem;
	}

	return NULL;
}
EXPORT_SYMBOL(cfg80211_find_ie_match);

const u8 *cfg80211_find_vendor_ie(unsigned int oui, int oui_type,
				  const u8 *ies, int len)
{
	const u8 *ie;
	u8 match[] = { oui >> 16, oui >> 8, oui, oui_type };
	int match_len = (oui_type < 0) ? 3 : sizeof(match);

	if (WARN_ON(oui_type > 0xff))
		return NULL;

	ie = cfg80211_find_ie_match(WLAN_EID_VENDOR_SPECIFIC, ies, len,
				    match, match_len, 2);

	if (ie && (ie[1] < 4))
		return NULL;

	return ie;
}
EXPORT_SYMBOL(cfg80211_find_vendor_ie);

static bool is_bss(struct cfg80211_bss *a, const u8 *bssid,
		   const u8 *ssid, size_t ssid_len)
{
	const struct cfg80211_bss_ies *ies;
	const u8 *ssidie;

	if (bssid && !ether_addr_equal(a->bssid, bssid))
		return false;

	if (!ssid)
		return true;

	ies = rcu_access_pointer(a->ies);
	if (!ies)
		return false;
	ssidie = cfg80211_find_ie(WLAN_EID_SSID, ies->data, ies->len);
	if (!ssidie)
		return false;
	if (ssidie[1] != ssid_len)
		return false;
	return memcmp(ssidie + 2, ssid, ssid_len) == 0;
}

/**
 * enum bss_compare_mode - BSS compare mode
 * @BSS_CMP_REGULAR: regular compare mode (for insertion and normal find)
 * @BSS_CMP_HIDE_ZLEN: find hidden SSID with zero-length mode
 * @BSS_CMP_HIDE_NUL: find hidden SSID with NUL-ed out mode
 */
enum bss_compare_mode {
	BSS_CMP_REGULAR,
	BSS_CMP_HIDE_ZLEN,
	BSS_CMP_HIDE_NUL,
};

static int cmp_bss(struct cfg80211_bss *a,
		   struct cfg80211_bss *b,
		   enum bss_compare_mode mode)
{
	const struct cfg80211_bss_ies *a_ies, *b_ies;
	const u8 *ie1 = NULL;
	const u8 *ie2 = NULL;
	int i, r;

	if (a->channel != b->channel)
		return b->channel->center_freq - a->channel->center_freq;

	a_ies = rcu_access_pointer(a->ies);
	if (!a_ies)
		return -1;
	b_ies = rcu_access_pointer(b->ies);
	if (!b_ies)
		return 1;

	if (WLAN_CAPABILITY_IS_STA_BSS(a->capability))
		ie1 = cfg80211_find_ie(WLAN_EID_MESH_ID,
				       a_ies->data, a_ies->len);
	if (WLAN_CAPABILITY_IS_STA_BSS(b->capability))
		ie2 = cfg80211_find_ie(WLAN_EID_MESH_ID,
				       b_ies->data, b_ies->len);
	if (ie1 && ie2) {
		int mesh_id_cmp;

		if (ie1[1] == ie2[1])
			mesh_id_cmp = memcmp(ie1 + 2, ie2 + 2, ie1[1]);
		else
			mesh_id_cmp = ie2[1] - ie1[1];

		ie1 = cfg80211_find_ie(WLAN_EID_MESH_CONFIG,
				       a_ies->data, a_ies->len);
		ie2 = cfg80211_find_ie(WLAN_EID_MESH_CONFIG,
				       b_ies->data, b_ies->len);
		if (ie1 && ie2) {
			if (mesh_id_cmp)
				return mesh_id_cmp;
			if (ie1[1] != ie2[1])
				return ie2[1] - ie1[1];
			return memcmp(ie1 + 2, ie2 + 2, ie1[1]);
		}
	}

	r = memcmp(a->bssid, b->bssid, sizeof(a->bssid));
	if (r)
		return r;

	ie1 = cfg80211_find_ie(WLAN_EID_SSID, a_ies->data, a_ies->len);
	ie2 = cfg80211_find_ie(WLAN_EID_SSID, b_ies->data, b_ies->len);

	if (!ie1 && !ie2)
		return 0;

	/*
	 * Note that with "hide_ssid", the function returns a match if
	 * the already-present BSS ("b") is a hidden SSID beacon for
	 * the new BSS ("a").
	 */

	/* sort missing IE before (left of) present IE */
	if (!ie1)
		return -1;
	if (!ie2)
		return 1;

	switch (mode) {
	case BSS_CMP_HIDE_ZLEN:
		/*
		 * In ZLEN mode we assume the BSS entry we're
		 * looking for has a zero-length SSID. So if
		 * the one we're looking at right now has that,
		 * return 0. Otherwise, return the difference
		 * in length, but since we're looking for the
		 * 0-length it's really equivalent to returning
		 * the length of the one we're looking at.
		 *
		 * No content comparison is needed as we assume
		 * the content length is zero.
		 */
		return ie2[1];
	case BSS_CMP_REGULAR:
	default:
		/* sort by length first, then by contents */
		if (ie1[1] != ie2[1])
			return ie2[1] - ie1[1];
		return memcmp(ie1 + 2, ie2 + 2, ie1[1]);
	case BSS_CMP_HIDE_NUL:
		if (ie1[1] != ie2[1])
			return ie2[1] - ie1[1];
		/* this is equivalent to memcmp(zeroes, ie2 + 2, len) */
		for (i = 0; i < ie2[1]; i++)
			if (ie2[i + 2])
				return -1;
		return 0;
	}
}

static bool cfg80211_bss_type_match(u16 capability,
				    enum nl80211_band band,
				    enum ieee80211_bss_type bss_type)
{
	bool ret = true;
	u16 mask, val;

	if (bss_type == IEEE80211_BSS_TYPE_ANY)
		return ret;

	if (band == NL80211_BAND_60GHZ) {
		mask = WLAN_CAPABILITY_DMG_TYPE_MASK;
		switch (bss_type) {
		case IEEE80211_BSS_TYPE_ESS:
			val = WLAN_CAPABILITY_DMG_TYPE_AP;
			break;
		case IEEE80211_BSS_TYPE_PBSS:
			val = WLAN_CAPABILITY_DMG_TYPE_PBSS;
			break;
		case IEEE80211_BSS_TYPE_IBSS:
			val = WLAN_CAPABILITY_DMG_TYPE_IBSS;
			break;
		default:
			return false;
		}
	} else {
		mask = WLAN_CAPABILITY_ESS | WLAN_CAPABILITY_IBSS;
		switch (bss_type) {
		case IEEE80211_BSS_TYPE_ESS:
			val = WLAN_CAPABILITY_ESS;
			break;
		case IEEE80211_BSS_TYPE_IBSS:
			val = WLAN_CAPABILITY_IBSS;
			break;
		case IEEE80211_BSS_TYPE_MBSS:
			val = 0;
			break;
		default:
			return false;
		}
	}

	ret = ((capability & mask) == val);
	return ret;
}

/* Returned bss is reference counted and must be cleaned up appropriately. */
struct cfg80211_bss *cfg80211_get_bss(struct wiphy *wiphy,
				      struct ieee80211_channel *channel,
				      const u8 *bssid,
				      const u8 *ssid, size_t ssid_len,
				      enum ieee80211_bss_type bss_type,
				      enum ieee80211_privacy privacy)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
	struct cfg80211_internal_bss *bss, *res = NULL;
	unsigned long now = jiffies;
	int bss_privacy;

	trace_cfg80211_get_bss(wiphy, channel, bssid, ssid, ssid_len, bss_type,
			       privacy);

	spin_lock_bh(&rdev->bss_lock);

	list_for_each_entry(bss, &rdev->bss_list, list) {
		if (!cfg80211_bss_type_match(bss->pub.capability,
					     bss->pub.channel->band, bss_type))
			continue;

		bss_privacy = (bss->pub.capability & WLAN_CAPABILITY_PRIVACY);
		if ((privacy == IEEE80211_PRIVACY_ON && !bss_privacy) ||
		    (privacy == IEEE80211_PRIVACY_OFF && bss_privacy))
			continue;
		if (channel && bss->pub.channel != channel)
			continue;
		if (!is_valid_ether_addr(bss->pub.bssid))
			continue;
		/* Don't get expired BSS structs */
		if (time_after(now, bss->ts + IEEE80211_SCAN_RESULT_EXPIRE) &&
		    !atomic_read(&bss->hold))
			continue;
		if (is_bss(&bss->pub, bssid, ssid, ssid_len)) {
			res = bss;
			bss_ref_get(rdev, res);
			break;
		}
	}

	spin_unlock_bh(&rdev->bss_lock);
	if (!res)
		return NULL;
	trace_cfg80211_return_bss(&res->pub);
	return &res->pub;
}
EXPORT_SYMBOL(cfg80211_get_bss);

static void rb_insert_bss(struct cfg80211_registered_device *rdev,
			  struct cfg80211_internal_bss *bss)
{
	struct rb_node **p = &rdev->bss_tree.rb_node;
	struct rb_node *parent = NULL;
	struct cfg80211_internal_bss *tbss;
	int cmp;

	while (*p) {
		parent = *p;
		tbss = rb_entry(parent, struct cfg80211_internal_bss, rbn);

		cmp = cmp_bss(&bss->pub, &tbss->pub, BSS_CMP_REGULAR);

		if (WARN_ON(!cmp)) {
			/* will sort of leak this BSS */
			return;
		}

		if (cmp < 0)
			p = &(*p)->rb_left;
		else
			p = &(*p)->rb_right;
	}

	rb_link_node(&bss->rbn, parent, p);
	rb_insert_color(&bss->rbn, &rdev->bss_tree);
}

static struct cfg80211_internal_bss *
rb_find_bss(struct cfg80211_registered_device *rdev,
	    struct cfg80211_internal_bss *res,
	    enum bss_compare_mode mode)
{
	struct rb_node *n = rdev->bss_tree.rb_node;
	struct cfg80211_internal_bss *bss;
	int r;

	while (n) {
		bss = rb_entry(n, struct cfg80211_internal_bss, rbn);
		r = cmp_bss(&res->pub, &bss->pub, mode);

		if (r == 0)
			return bss;
		else if (r < 0)
			n = n->rb_left;
		else
			n = n->rb_right;
	}

	return NULL;
}

static bool cfg80211_combine_bsses(struct cfg80211_registered_device *rdev,
				   struct cfg80211_internal_bss *new)
{
	const struct cfg80211_bss_ies *ies;
	struct cfg80211_internal_bss *bss;
	const u8 *ie;
	int i, ssidlen;
	u8 fold = 0;
	u32 n_entries = 0;

	ies = rcu_access_pointer(new->pub.beacon_ies);
	if (WARN_ON(!ies))
		return false;

	ie = cfg80211_find_ie(WLAN_EID_SSID, ies->data, ies->len);
	if (!ie) {
		/* nothing to do */
		return true;
	}

	ssidlen = ie[1];
	for (i = 0; i < ssidlen; i++)
		fold |= ie[2 + i];

	if (fold) {
		/* not a hidden SSID */
		return true;
	}

	/* This is the bad part ... */

	list_for_each_entry(bss, &rdev->bss_list, list) {
		/*
		 * we're iterating all the entries anyway, so take the
		 * opportunity to validate the list length accounting
		 */
		n_entries++;

		if (!ether_addr_equal(bss->pub.bssid, new->pub.bssid))
			continue;
		if (bss->pub.channel != new->pub.channel)
			continue;
		if (bss->pub.scan_width != new->pub.scan_width)
			continue;
		if (rcu_access_pointer(bss->pub.beacon_ies))
			continue;
		ies = rcu_access_pointer(bss->pub.ies);
		if (!ies)
			continue;
		ie = cfg80211_find_ie(WLAN_EID_SSID, ies->data, ies->len);
		if (!ie)
			continue;
		if (ssidlen && ie[1] != ssidlen)
			continue;
		if (WARN_ON_ONCE(bss->pub.hidden_beacon_bss))
			continue;
		if (WARN_ON_ONCE(!list_empty(&bss->hidden_list)))
			list_del(&bss->hidden_list);
		/* combine them */
		list_add(&bss->hidden_list, &new->hidden_list);
		bss->pub.hidden_beacon_bss = &new->pub;
		new->refcount += bss->refcount;
		rcu_assign_pointer(bss->pub.beacon_ies,
				   new->pub.beacon_ies);
	}

	WARN_ONCE(n_entries != rdev->bss_entries,
		  "rdev bss entries[%d]/list[len:%d] corruption\n",
		  rdev->bss_entries, n_entries);

	return true;
}

/* Returned bss is reference counted and must be cleaned up appropriately. */
static struct cfg80211_internal_bss *
cfg80211_bss_update(struct cfg80211_registered_device *rdev,
		    struct cfg80211_internal_bss *tmp,
		    bool signal_valid)
{
	struct cfg80211_internal_bss *found = NULL;

	if (WARN_ON(!tmp->pub.channel))
		return NULL;

	tmp->ts = jiffies;

	spin_lock_bh(&rdev->bss_lock);

	if (WARN_ON(!rcu_access_pointer(tmp->pub.ies))) {
		spin_unlock_bh(&rdev->bss_lock);
		return NULL;
	}

	found = rb_find_bss(rdev, tmp, BSS_CMP_REGULAR);

	if (found) {
		/* Update IEs */
		if (rcu_access_pointer(tmp->pub.proberesp_ies)) {
			const struct cfg80211_bss_ies *old;

			old = rcu_access_pointer(found->pub.proberesp_ies);

			rcu_assign_pointer(found->pub.proberesp_ies,
					   tmp->pub.proberesp_ies);
			/* Override possible earlier Beacon frame IEs */
			rcu_assign_pointer(found->pub.ies,
					   tmp->pub.proberesp_ies);
			if (old)
				kfree_rcu((struct cfg80211_bss_ies *)old,
					  rcu_head);
		} else if (rcu_access_pointer(tmp->pub.beacon_ies)) {
			const struct cfg80211_bss_ies *old;
			struct cfg80211_internal_bss *bss;

			if (found->pub.hidden_beacon_bss &&
			    !list_empty(&found->hidden_list)) {
				const struct cfg80211_bss_ies *f;

				/*
				 * The found BSS struct is one of the probe
				 * response members of a group, but we're
				 * receiving a beacon (beacon_ies in the tmp
				 * bss is used). This can only mean that the
				 * AP changed its beacon from not having an
				 * SSID to showing it, which is confusing so
				 * drop this information.
				 */

				f = rcu_access_pointer(tmp->pub.beacon_ies);
				kfree_rcu((struct cfg80211_bss_ies *)f,
					  rcu_head);
				goto drop;
			}

			old = rcu_access_pointer(found->pub.beacon_ies);

			rcu_assign_pointer(found->pub.beacon_ies,
					   tmp->pub.beacon_ies);

			/* Override IEs if they were from a beacon before */
			if (old == rcu_access_pointer(found->pub.ies))
				rcu_assign_pointer(found->pub.ies,
						   tmp->pub.beacon_ies);

			/* Assign beacon IEs to all sub entries */
			list_for_each_entry(bss, &found->hidden_list,
					    hidden_list) {
				const struct cfg80211_bss_ies *ies;

				ies = rcu_access_pointer(bss->pub.beacon_ies);
				WARN_ON(ies != old);

				rcu_assign_pointer(bss->pub.beacon_ies,
						   tmp->pub.beacon_ies);
			}

			if (old)
				kfree_rcu((struct cfg80211_bss_ies *)old,
					  rcu_head);
		}

		found->pub.beacon_interval = tmp->pub.beacon_interval;
		/*
		 * don't update the signal if beacon was heard on
		 * adjacent channel.
		 */
		if (signal_valid)
			found->pub.signal = tmp->pub.signal;
		found->pub.capability = tmp->pub.capability;
		found->ts = tmp->ts;
		found->ts_boottime = tmp->ts_boottime;
		found->parent_tsf = tmp->parent_tsf;
		ether_addr_copy(found->parent_bssid, tmp->parent_bssid);
	} else {
		struct cfg80211_internal_bss *new;
		struct cfg80211_internal_bss *hidden;
		struct cfg80211_bss_ies *ies;

		/*
		 * create a copy -- the "res" variable that is passed in
		 * is allocated on the stack since it's not needed in the
		 * more common case of an update
		 */
		new = kzalloc(sizeof(*new) + rdev->wiphy.bss_priv_size,
			      GFP_ATOMIC);
		if (!new) {
			ies = (void *)rcu_dereference(tmp->pub.beacon_ies);
			if (ies)
				kfree_rcu(ies, rcu_head);
			ies = (void *)rcu_dereference(tmp->pub.proberesp_ies);
			if (ies)
				kfree_rcu(ies, rcu_head);
			goto drop;
		}
		memcpy(new, tmp, sizeof(*new));
		new->refcount = 1;
		INIT_LIST_HEAD(&new->hidden_list);

		if (rcu_access_pointer(tmp->pub.proberesp_ies)) {
			hidden = rb_find_bss(rdev, tmp, BSS_CMP_HIDE_ZLEN);
			if (!hidden)
				hidden = rb_find_bss(rdev, tmp,
						     BSS_CMP_HIDE_NUL);
			if (hidden) {
				new->pub.hidden_beacon_bss = &hidden->pub;
				list_add(&new->hidden_list,
					 &hidden->hidden_list);
				hidden->refcount++;

				ies = (void *)rcu_access_pointer(new->pub.beacon_ies);
				rcu_assign_pointer(new->pub.beacon_ies,
						   hidden->pub.beacon_ies);
				if (ies)
					kfree_rcu(ies, rcu_head);
			}
		} else {
			/*
			 * Ok so we found a beacon, and don't have an entry. If
			 * it's a beacon with hidden SSID, we might be in for an
			 * expensive search for any probe responses that should
			 * be grouped with this beacon for updates ...
			 */
			if (!cfg80211_combine_bsses(rdev, new)) {
				bss_ref_put(rdev, new);
				goto drop;
			}
		}

		if (rdev->bss_entries >= bss_entries_limit &&
		    !cfg80211_bss_expire_oldest(rdev)) {
			bss_ref_put(rdev, new);
			goto drop;
		}

		list_add_tail(&new->list, &rdev->bss_list);
		rdev->bss_entries++;
		rb_insert_bss(rdev, new);
		found = new;
	}

	rdev->bss_generation++;
	bss_ref_get(rdev, found);
	spin_unlock_bh(&rdev->bss_lock);

	return found;
 drop:
	spin_unlock_bh(&rdev->bss_lock);
	return NULL;
}

/*
 * Update RX channel information based on the available frame payload
 * information. This is mainly for the 2.4 GHz band where frames can be received
 * from neighboring channels and the Beacon frames use the DSSS Parameter Set
 * element to indicate the current (transmitting) channel, but this might also
 * be needed on other bands if RX frequency does not match with the actual
 * operating channel of a BSS.
 */
static struct ieee80211_channel *
cfg80211_get_bss_channel(struct wiphy *wiphy, const u8 *ie, size_t ielen,
			 struct ieee80211_channel *channel,
			 enum nl80211_bss_scan_width scan_width)
{
	const u8 *tmp;
	u32 freq;
	int channel_number = -1;
	struct ieee80211_channel *alt_channel;

	tmp = cfg80211_find_ie(WLAN_EID_DS_PARAMS, ie, ielen);
	if (tmp && tmp[1] == 1) {
		channel_number = tmp[2];
	} else {
		tmp = cfg80211_find_ie(WLAN_EID_HT_OPERATION, ie, ielen);
		if (tmp && tmp[1] >= sizeof(struct ieee80211_ht_operation)) {
			struct ieee80211_ht_operation *htop = (void *)(tmp + 2);

			channel_number = htop->primary_chan;
		}
	}

	if (channel_number < 0) {
		/* No channel information in frame payload */
		return channel;
	}

	freq = ieee80211_channel_to_frequency(channel_number, channel->band);
	alt_channel = ieee80211_get_channel(wiphy, freq);
	if (!alt_channel) {
		if (channel->band == NL80211_BAND_2GHZ) {
			/*
			 * Better not allow unexpected channels when that could
			 * be going beyond the 1-11 range (e.g., discovering
			 * BSS on channel 12 when radio is configured for
			 * channel 11.
			 */
			return NULL;
		}

		/* No match for the payload channel number - ignore it */
		return channel;
	}

	if (scan_width == NL80211_BSS_CHAN_WIDTH_10 ||
	    scan_width == NL80211_BSS_CHAN_WIDTH_5) {
		/*
		 * Ignore channel number in 5 and 10 MHz channels where there
		 * may not be an n:1 or 1:n mapping between frequencies and
		 * channel numbers.
		 */
		return channel;
	}

	/*
	 * Use the channel determined through the payload channel number
	 * instead of the RX channel reported by the driver.
	 */
	if (alt_channel->flags & IEEE80211_CHAN_DISABLED)
		return NULL;
	return alt_channel;
}

/* Returned bss is reference counted and must be cleaned up appropriately. */
struct cfg80211_bss *
cfg80211_inform_bss_data(struct wiphy *wiphy,
			 struct cfg80211_inform_bss *data,
			 enum cfg80211_bss_frame_type ftype,
			 const u8 *bssid, u64 tsf, u16 capability,
			 u16 beacon_interval, const u8 *ie, size_t ielen,
			 gfp_t gfp)
{
	struct cfg80211_bss_ies *ies;
	struct ieee80211_channel *channel;
	struct cfg80211_internal_bss tmp = {}, *res;
	int bss_type;
	bool signal_valid;

	if (WARN_ON(!wiphy))
		return NULL;

	if (WARN_ON(wiphy->signal_type == CFG80211_SIGNAL_TYPE_UNSPEC &&
		    (data->signal < 0 || data->signal > 100)))
		return NULL;

	channel = cfg80211_get_bss_channel(wiphy, ie, ielen, data->chan,
					   data->scan_width);
	if (!channel)
		return NULL;

	memcpy(tmp.pub.bssid, bssid, ETH_ALEN);
	tmp.pub.channel = channel;
	tmp.pub.scan_width = data->scan_width;
	tmp.pub.signal = data->signal;
	tmp.pub.beacon_interval = beacon_interval;
	tmp.pub.capability = capability;
	tmp.ts_boottime = data->boottime_ns;

	/*
	 * If we do not know here whether the IEs are from a Beacon or Probe
	 * Response frame, we need to pick one of the options and only use it
	 * with the driver that does not provide the full Beacon/Probe Response
	 * frame. Use Beacon frame pointer to avoid indicating that this should
	 * override the IEs pointer should we have received an earlier
	 * indication of Probe Response data.
	 */
	ies = kzalloc(sizeof(*ies) + ielen, gfp);
	if (!ies)
		return NULL;
	ies->len = ielen;
	ies->tsf = tsf;
	ies->from_beacon = false;
	memcpy(ies->data, ie, ielen);

	switch (ftype) {
	case CFG80211_BSS_FTYPE_BEACON:
		ies->from_beacon = true;
		/* fall through to assign */
	case CFG80211_BSS_FTYPE_UNKNOWN:
		rcu_assign_pointer(tmp.pub.beacon_ies, ies);
		break;
	case CFG80211_BSS_FTYPE_PRESP:
		rcu_assign_pointer(tmp.pub.proberesp_ies, ies);
		break;
	}
	rcu_assign_pointer(tmp.pub.ies, ies);

	signal_valid = abs(data->chan->center_freq - channel->center_freq) <=
		wiphy->max_adj_channel_rssi_comp;
	res = cfg80211_bss_update(wiphy_to_rdev(wiphy), &tmp, signal_valid);
	if (!res)
		return NULL;

	if (channel->band == NL80211_BAND_60GHZ) {
		bss_type = res->pub.capability & WLAN_CAPABILITY_DMG_TYPE_MASK;
		if (bss_type == WLAN_CAPABILITY_DMG_TYPE_AP ||
		    bss_type == WLAN_CAPABILITY_DMG_TYPE_PBSS)
			regulatory_hint_found_beacon(wiphy, channel, gfp);
	} else {
		if (res->pub.capability & WLAN_CAPABILITY_ESS)
			regulatory_hint_found_beacon(wiphy, channel, gfp);
	}

	trace_cfg80211_return_bss(&res->pub);
	/* cfg80211_bss_update gives us a referenced result */
	return &res->pub;
}
EXPORT_SYMBOL(cfg80211_inform_bss_data);

/* cfg80211_inform_bss_width_frame helper */
struct cfg80211_bss *
cfg80211_inform_bss_frame_data(struct wiphy *wiphy,
			       struct cfg80211_inform_bss *data,
			       struct ieee80211_mgmt *mgmt, size_t len,
			       gfp_t gfp)

{
	struct cfg80211_internal_bss tmp = {}, *res;
	struct cfg80211_bss_ies *ies;
	struct ieee80211_channel *channel;
	bool signal_valid;
	size_t ielen = len - offsetof(struct ieee80211_mgmt,
				      u.probe_resp.variable);
	int bss_type;

	BUILD_BUG_ON(offsetof(struct ieee80211_mgmt, u.probe_resp.variable) !=
			offsetof(struct ieee80211_mgmt, u.beacon.variable));

	trace_cfg80211_inform_bss_frame(wiphy, data, mgmt, len);

	if (WARN_ON(!mgmt))
		return NULL;

	if (WARN_ON(!wiphy))
		return NULL;

	if (WARN_ON(wiphy->signal_type == CFG80211_SIGNAL_TYPE_UNSPEC &&
		    (data->signal < 0 || data->signal > 100)))
		return NULL;

	if (WARN_ON(len < offsetof(struct ieee80211_mgmt, u.probe_resp.variable)))
		return NULL;

	channel = cfg80211_get_bss_channel(wiphy, mgmt->u.beacon.variable,
					   ielen, data->chan, data->scan_width);
	if (!channel)
		return NULL;

	ies = kzalloc(sizeof(*ies) + ielen, gfp);
	if (!ies)
		return NULL;
	ies->len = ielen;
	ies->tsf = le64_to_cpu(mgmt->u.probe_resp.timestamp);
	ies->from_beacon = ieee80211_is_beacon(mgmt->frame_control);
	memcpy(ies->data, mgmt->u.probe_resp.variable, ielen);

	if (ieee80211_is_probe_resp(mgmt->frame_control))
		rcu_assign_pointer(tmp.pub.proberesp_ies, ies);
	else
		rcu_assign_pointer(tmp.pub.beacon_ies, ies);
	rcu_assign_pointer(tmp.pub.ies, ies);

	memcpy(tmp.pub.bssid, mgmt->bssid, ETH_ALEN);
	tmp.pub.channel = channel;
	tmp.pub.scan_width = data->scan_width;
	tmp.pub.signal = data->signal;
	tmp.pub.beacon_interval = le16_to_cpu(mgmt->u.probe_resp.beacon_int);
	tmp.pub.capability = le16_to_cpu(mgmt->u.probe_resp.capab_info);
	tmp.ts_boottime = data->boottime_ns;
	tmp.parent_tsf = data->parent_tsf;
	ether_addr_copy(tmp.parent_bssid, data->parent_bssid);

	signal_valid = abs(data->chan->center_freq - channel->center_freq) <=
		wiphy->max_adj_channel_rssi_comp;
	res = cfg80211_bss_update(wiphy_to_rdev(wiphy), &tmp, signal_valid);
	if (!res)
		return NULL;

	if (channel->band == NL80211_BAND_60GHZ) {
		bss_type = res->pub.capability & WLAN_CAPABILITY_DMG_TYPE_MASK;
		if (bss_type == WLAN_CAPABILITY_DMG_TYPE_AP ||
		    bss_type == WLAN_CAPABILITY_DMG_TYPE_PBSS)
			regulatory_hint_found_beacon(wiphy, channel, gfp);
	} else {
		if (res->pub.capability & WLAN_CAPABILITY_ESS)
			regulatory_hint_found_beacon(wiphy, channel, gfp);
	}

	trace_cfg80211_return_bss(&res->pub);
	/* cfg80211_bss_update gives us a referenced result */
	return &res->pub;
}
EXPORT_SYMBOL(cfg80211_inform_bss_frame_data);

void cfg80211_ref_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
	struct cfg80211_internal_bss *bss;

	if (!pub)
		return;

	bss = container_of(pub, struct cfg80211_internal_bss, pub);

	spin_lock_bh(&rdev->bss_lock);
	bss_ref_get(rdev, bss);
	spin_unlock_bh(&rdev->bss_lock);
}
EXPORT_SYMBOL(cfg80211_ref_bss);

void cfg80211_put_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
	struct cfg80211_internal_bss *bss;

	if (!pub)
		return;

	bss = container_of(pub, struct cfg80211_internal_bss, pub);

	spin_lock_bh(&rdev->bss_lock);
	bss_ref_put(rdev, bss);
	spin_unlock_bh(&rdev->bss_lock);
}
EXPORT_SYMBOL(cfg80211_put_bss);

void cfg80211_unlink_bss(struct wiphy *wiphy, struct cfg80211_bss *pub)
{
	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
	struct cfg80211_internal_bss *bss;

	if (WARN_ON(!pub))
		return;

	bss = container_of(pub, struct cfg80211_internal_bss, pub);

	spin_lock_bh(&rdev->bss_lock);
	if (!list_empty(&bss->list)) {
		if (__cfg80211_unlink_bss(rdev, bss))
			rdev->bss_generation++;
	}
	spin_unlock_bh(&rdev->bss_lock);
}
EXPORT_SYMBOL(cfg80211_unlink_bss);

#ifdef CONFIG_CFG80211_WEXT
static struct cfg80211_registered_device *
cfg80211_get_dev_from_ifindex(struct net *net, int ifindex)
{
	struct cfg80211_registered_device *rdev;
	struct net_device *dev;

	ASSERT_RTNL();

	dev = dev_get_by_index(net, ifindex);
	if (!dev)
		return ERR_PTR(-ENODEV);
	if (dev->ieee80211_ptr)
		rdev = wiphy_to_rdev(dev->ieee80211_ptr->wiphy);
	else
		rdev = ERR_PTR(-ENODEV);
	dev_put(dev);
	return rdev;
}

int cfg80211_wext_siwscan(struct net_device *dev,
			  struct iw_request_info *info,
			  union iwreq_data *wrqu, char *extra)
{
	struct cfg80211_registered_device *rdev;
	struct wiphy *wiphy;
	struct iw_scan_req *wreq = NULL;
	struct cfg80211_scan_request *creq = NULL;
	int i, err, n_channels = 0;
	enum nl80211_band band;

	if (!netif_running(dev))
		return -ENETDOWN;

	if (wrqu->data.length == sizeof(struct iw_scan_req))
		wreq = (struct iw_scan_req *)extra;

	rdev = cfg80211_get_dev_from_ifindex(dev_net(dev), dev->ifindex);

	if (IS_ERR(rdev))
		return PTR_ERR(rdev);

	if (rdev->scan_req || rdev->scan_msg) {
		err = -EBUSY;
		goto out;
	}

	wiphy = &rdev->wiphy;

	/* Determine number of channels, needed to allocate creq */
	if (wreq && wreq->num_channels)
		n_channels = wreq->num_channels;
	else
		n_channels = ieee80211_get_num_supported_channels(wiphy);

	creq = kzalloc(sizeof(*creq) + sizeof(struct cfg80211_ssid) +
		       n_channels * sizeof(void *),
		       GFP_ATOMIC);
	if (!creq) {
		err = -ENOMEM;
		goto out;
	}

	creq->wiphy = wiphy;
	creq->wdev = dev->ieee80211_ptr;
	/* SSIDs come after channels */
	creq->ssids = (void *)&creq->channels[n_channels];
	creq->n_channels = n_channels;
	creq->n_ssids = 1;
	creq->scan_start = jiffies;

	/* translate "Scan on frequencies" request */
	i = 0;
	for (band = 0; band < NUM_NL80211_BANDS; band++) {
		int j;

		if (!wiphy->bands[band])
			continue;

		for (j = 0; j < wiphy->bands[band]->n_channels; j++) {
			/* ignore disabled channels */
			if (wiphy->bands[band]->channels[j].flags &
						IEEE80211_CHAN_DISABLED)
				continue;

			/* If we have a wireless request structure and the
			 * wireless request specifies frequencies, then search
			 * for the matching hardware channel.
			 */
			if (wreq && wreq->num_channels) {
				int k;
				int wiphy_freq = wiphy->bands[band]->channels[j].center_freq;
				for (k = 0; k < wreq->num_channels; k++) {
					struct iw_freq *freq =
						&wreq->channel_list[k];
					int wext_freq =
						cfg80211_wext_freq(freq);

					if (wext_freq == wiphy_freq)
						goto wext_freq_found;
				}
				goto wext_freq_not_found;
			}

		wext_freq_found:
			creq->channels[i] = &wiphy->bands[band]->channels[j];
			i++;
		wext_freq_not_found: ;
		}
	}
	/* No channels found? */
	if (!i) {
		err = -EINVAL;
		goto out;
	}

	/* Set real number of channels specified in creq->channels[] */
	creq->n_channels = i;

	/* translate "Scan for SSID" request */
	if (wreq) {
		if (wrqu->data.flags & IW_SCAN_THIS_ESSID) {
			if (wreq->essid_len > IEEE80211_MAX_SSID_LEN) {
				err = -EINVAL;
				goto out;
			}
			memcpy(creq->ssids[0].ssid, wreq->essid, wreq->essid_len);
			creq->ssids[0].ssid_len = wreq->essid_len;
		}
		if (wreq->scan_type == IW_SCAN_TYPE_PASSIVE)
			creq->n_ssids = 0;
	}

	for (i = 0; i < NUM_NL80211_BANDS; i++)
		if (wiphy->bands[i])
			creq->rates[i] = (1 << wiphy->bands[i]->n_bitrates) - 1;

	eth_broadcast_addr(creq->bssid);

	rdev->scan_req = creq;
	err = rdev_scan(rdev, creq);
	if (err) {
		rdev->scan_req = NULL;
		/* creq will be freed below */
	} else {
		nl80211_send_scan_start(rdev, dev->ieee80211_ptr);
		/* creq now owned by driver */
		creq = NULL;
		dev_hold(dev);
	}
 out:
	kfree(creq);
	return err;
}
EXPORT_WEXT_HANDLER(cfg80211_wext_siwscan);

static char *ieee80211_scan_add_ies(struct iw_request_info *info,
				    const struct cfg80211_bss_ies *ies,
				    char *current_ev, char *end_buf)
{
	const u8 *pos, *end, *next;
	struct iw_event iwe;

	if (!ies)
		return current_ev;

	/*
	 * If needed, fragment the IEs buffer (at IE boundaries) into short
	 * enough fragments to fit into IW_GENERIC_IE_MAX octet messages.
	 */
	pos = ies->data;
	end = pos + ies->len;

	while (end - pos > IW_GENERIC_IE_MAX) {
		next = pos + 2 + pos[1];
		while (next + 2 + next[1] - pos < IW_GENERIC_IE_MAX)
			next = next + 2 + next[1];

		memset(&iwe, 0, sizeof(iwe));
		iwe.cmd = IWEVGENIE;
		iwe.u.data.length = next - pos;
		current_ev = iwe_stream_add_point_check(info, current_ev,
							end_buf, &iwe,
							(void *)pos);
		if (IS_ERR(current_ev))
			return current_ev;
		pos = next;
	}

	if (end > pos) {
		memset(&iwe, 0, sizeof(iwe));
		iwe.cmd = IWEVGENIE;
		iwe.u.data.length = end - pos;
		current_ev = iwe_stream_add_point_check(info, current_ev,
							end_buf, &iwe,
							(void *)pos);
		if (IS_ERR(current_ev))
			return current_ev;
	}

	return current_ev;
}

static char *
ieee80211_bss(struct wiphy *wiphy, struct iw_request_info *info,
	      struct cfg80211_internal_bss *bss, char *current_ev,
	      char *end_buf)
{
	const struct cfg80211_bss_ies *ies;
	struct iw_event iwe;
	const u8 *ie;
	u8 buf[50];
	u8 *cfg, *p, *tmp;
	int rem, i, sig;
	bool ismesh = false;

	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = SIOCGIWAP;
	iwe.u.ap_addr.sa_family = ARPHRD_ETHER;
	memcpy(iwe.u.ap_addr.sa_data, bss->pub.bssid, ETH_ALEN);
	current_ev = iwe_stream_add_event_check(info, current_ev, end_buf, &iwe,
						IW_EV_ADDR_LEN);
	if (IS_ERR(current_ev))
		return current_ev;

	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = SIOCGIWFREQ;
	iwe.u.freq.m = ieee80211_frequency_to_channel(bss->pub.channel->center_freq);
	iwe.u.freq.e = 0;
	current_ev = iwe_stream_add_event_check(info, current_ev, end_buf, &iwe,
						IW_EV_FREQ_LEN);
	if (IS_ERR(current_ev))
		return current_ev;

	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = SIOCGIWFREQ;
	iwe.u.freq.m = bss->pub.channel->center_freq;
	iwe.u.freq.e = 6;
	current_ev = iwe_stream_add_event_check(info, current_ev, end_buf, &iwe,
						IW_EV_FREQ_LEN);
	if (IS_ERR(current_ev))
		return current_ev;

	if (wiphy->signal_type != CFG80211_SIGNAL_TYPE_NONE) {
		memset(&iwe, 0, sizeof(iwe));
		iwe.cmd = IWEVQUAL;
		iwe.u.qual.updated = IW_QUAL_LEVEL_UPDATED |
				     IW_QUAL_NOISE_INVALID |
				     IW_QUAL_QUAL_UPDATED;
		switch (wiphy->signal_type) {
		case CFG80211_SIGNAL_TYPE_MBM:
			sig = bss->pub.signal / 100;
			iwe.u.qual.level = sig;
			iwe.u.qual.updated |= IW_QUAL_DBM;
			if (sig < -110)		/* rather bad */
				sig = -110;
			else if (sig > -40)	/* perfect */
				sig = -40;
			/* will give a range of 0 .. 70 */
			iwe.u.qual.qual = sig + 110;
			break;
		case CFG80211_SIGNAL_TYPE_UNSPEC:
			iwe.u.qual.level = bss->pub.signal;
			/* will give range 0 .. 100 */
			iwe.u.qual.qual = bss->pub.signal;
			break;
		default:
			/* not reached */
			break;
		}
		current_ev = iwe_stream_add_event_check(info, current_ev,
							end_buf, &iwe,
							IW_EV_QUAL_LEN);
		if (IS_ERR(current_ev))
			return current_ev;
	}

	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = SIOCGIWENCODE;
	if (bss->pub.capability & WLAN_CAPABILITY_PRIVACY)
		iwe.u.data.flags = IW_ENCODE_ENABLED | IW_ENCODE_NOKEY;
	else
		iwe.u.data.flags = IW_ENCODE_DISABLED;
	iwe.u.data.length = 0;
	current_ev = iwe_stream_add_point_check(info, current_ev, end_buf,
						&iwe, "");
	if (IS_ERR(current_ev))
		return current_ev;

	rcu_read_lock();
	ies = rcu_dereference(bss->pub.ies);
	rem = ies->len;
	ie = ies->data;

	while (rem >= 2) {
		/* invalid data */
		if (ie[1] > rem - 2)
			break;

		switch (ie[0]) {
		case WLAN_EID_SSID:
			memset(&iwe, 0, sizeof(iwe));
			iwe.cmd = SIOCGIWESSID;
			iwe.u.data.length = ie[1];
			iwe.u.data.flags = 1;
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf, &iwe,
								(u8 *)ie + 2);
			if (IS_ERR(current_ev))
				goto unlock;
			break;
		case WLAN_EID_MESH_ID:
			memset(&iwe, 0, sizeof(iwe));
			iwe.cmd = SIOCGIWESSID;
			iwe.u.data.length = ie[1];
			iwe.u.data.flags = 1;
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf, &iwe,
								(u8 *)ie + 2);
			if (IS_ERR(current_ev))
				goto unlock;
			break;
		case WLAN_EID_MESH_CONFIG:
			ismesh = true;
			if (ie[1] != sizeof(struct ieee80211_meshconf_ie))
				break;
			cfg = (u8 *)ie + 2;
			memset(&iwe, 0, sizeof(iwe));
			iwe.cmd = IWEVCUSTOM;
			sprintf(buf, "Mesh Network Path Selection Protocol ID: "
				"0x%02X", cfg[0]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Path Selection Metric ID: 0x%02X",
				cfg[1]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Congestion Control Mode ID: 0x%02X",
				cfg[2]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Synchronization ID: 0x%02X", cfg[3]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Authentication ID: 0x%02X", cfg[4]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Formation Info: 0x%02X", cfg[5]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			sprintf(buf, "Capabilities: 0x%02X", cfg[6]);
			iwe.u.data.length = strlen(buf);
			current_ev = iwe_stream_add_point_check(info,
								current_ev,
								end_buf,
								&iwe, buf);
			if (IS_ERR(current_ev))
				goto unlock;
			break;
		case WLAN_EID_SUPP_RATES:
		case WLAN_EID_EXT_SUPP_RATES:
			/* display all supported rates in readable format */
			p = current_ev + iwe_stream_lcp_len(info);

			memset(&iwe, 0, sizeof(iwe));
			iwe.cmd = SIOCGIWRATE;
			/* Those two flags are ignored... */
			iwe.u.bitrate.fixed = iwe.u.bitrate.disabled = 0;

			for (i = 0; i < ie[1]; i++) {
				iwe.u.bitrate.value =
					((ie[i + 2] & 0x7f) * 500000);
				tmp = p;
				p = iwe_stream_add_value(info, current_ev, p,
							 end_buf, &iwe,
							 IW_EV_PARAM_LEN);
				if (p == tmp) {
					current_ev = ERR_PTR(-E2BIG);
					goto unlock;
				}
			}
			current_ev = p;
			break;
		}
		rem -= ie[1] + 2;
		ie += ie[1] + 2;
	}

	if (bss->pub.capability & (WLAN_CAPABILITY_ESS | WLAN_CAPABILITY_IBSS) ||
	    ismesh) {
		memset(&iwe, 0, sizeof(iwe));
		iwe.cmd = SIOCGIWMODE;
		if (ismesh)
			iwe.u.mode = IW_MODE_MESH;
		else if (bss->pub.capability & WLAN_CAPABILITY_ESS)
			iwe.u.mode = IW_MODE_MASTER;
		else
			iwe.u.mode = IW_MODE_ADHOC;
		current_ev = iwe_stream_add_event_check(info, current_ev,
							end_buf, &iwe,
							IW_EV_UINT_LEN);
		if (IS_ERR(current_ev))
			goto unlock;
	}

	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = IWEVCUSTOM;
	sprintf(buf, "tsf=%016llx", (unsigned long long)(ies->tsf));
	iwe.u.data.length = strlen(buf);
	current_ev = iwe_stream_add_point_check(info, current_ev, end_buf,
						&iwe, buf);
	if (IS_ERR(current_ev))
		goto unlock;
	memset(&iwe, 0, sizeof(iwe));
	iwe.cmd = IWEVCUSTOM;
	sprintf(buf, " Last beacon: %ums ago",
		elapsed_jiffies_msecs(bss->ts));
	iwe.u.data.length = strlen(buf);
	current_ev = iwe_stream_add_point_check(info, current_ev,
						end_buf, &iwe, buf);
	if (IS_ERR(current_ev))
		goto unlock;

	current_ev = ieee80211_scan_add_ies(info, ies, current_ev, end_buf);

 unlock:
	rcu_read_unlock();
	return current_ev;
}


static int ieee80211_scan_results(struct cfg80211_registered_device *rdev,
				  struct iw_request_info *info,
				  char *buf, size_t len)
{
	char *current_ev = buf;
	char *end_buf = buf + len;
	struct cfg80211_internal_bss *bss;
	int err = 0;

	spin_lock_bh(&rdev->bss_lock);
	cfg80211_bss_expire(rdev);

	list_for_each_entry(bss, &rdev->bss_list, list) {
		if (buf + len - current_ev <= IW_EV_ADDR_LEN) {
			err = -E2BIG;
			break;
		}
		current_ev = ieee80211_bss(&rdev->wiphy, info, bss,
					   current_ev, end_buf);
		if (IS_ERR(current_ev)) {
			err = PTR_ERR(current_ev);
			break;
		}
	}
	spin_unlock_bh(&rdev->bss_lock);

	if (err)
		return err;
	return current_ev - buf;
}


int cfg80211_wext_giwscan(struct net_device *dev,
			  struct iw_request_info *info,
			  struct iw_point *data, char *extra)
{
	struct cfg80211_registered_device *rdev;
	int res;

	if (!netif_running(dev))
		return -ENETDOWN;

	rdev = cfg80211_get_dev_from_ifindex(dev_net(dev), dev->ifindex);

	if (IS_ERR(rdev))
		return PTR_ERR(rdev);

	if (rdev->scan_req || rdev->scan_msg)
		return -EAGAIN;

	res = ieee80211_scan_results(rdev, info, extra, data->length);
	data->length = 0;
	if (res >= 0) {
		data->length = res;
		res = 0;
	}

	return res;
}
EXPORT_WEXT_HANDLER(cfg80211_wext_giwscan);
#endif