Release 4.11 net/wireless/scan.c

/*
 * 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	(30 * 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);
}

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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++;
	}
}

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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);
}

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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;
}

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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++;
}

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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;
}

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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);
}

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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();
}

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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);
}
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EXPORT_SYMBOL(cfg80211_scan_done);



void __cfg80211_sched_scan_results(struct work_struct *wk)
{
	struct cfg80211_registered_device *rdev;
	struct cfg80211_sched_scan_request *request;

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

	rtnl_lock();

	request = rtnl_dereference(rdev->sched_scan_req);

	/* we don't have sched_scan_req anymore if the scan is stopping */
	if (request) {
		if (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);
			request->scan_start = jiffies;
		}
		nl80211_send_sched_scan(rdev, request->dev,
					NL80211_CMD_SCHED_SCAN_RESULTS);
	}

	rtnl_unlock();
}

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void cfg80211_sched_scan_results(struct wiphy *wiphy)
{
	trace_cfg80211_sched_scan_results(wiphy);
	/* ignore if we're not scanning */

	if (rcu_access_pointer(wiphy_to_rdev(wiphy)->sched_scan_req))
		queue_work(cfg80211_wq,
			   &wiphy_to_rdev(wiphy)->sched_scan_results_wk);
}
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EXPORT_SYMBOL(cfg80211_sched_scan_results);



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

	ASSERT_RTNL();

	trace_cfg80211_sched_scan_stopped(wiphy);

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



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



int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
			       bool driver_initiated)
{
	struct cfg80211_sched_scan_request *sched_scan_req;
	struct net_device *dev;

	ASSERT_RTNL();

	if (!rdev->sched_scan_req)
		return -ENOENT;

	sched_scan_req = rtnl_dereference(rdev->sched_scan_req);
	dev = sched_scan_req->dev;

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

	nl80211_send_sched_scan(rdev, dev, NL80211_CMD_SCHED_SCAN_STOPPED);

	RCU_INIT_POINTER(rdev->sched_scan_req, NULL);
	kfree_rcu(sched_scan_req, rcu_head);

	return 0;
}

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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);
}

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

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

	while (len >= 2 && len >= ies[1] + 2) {
		if ((ies[0] == eid) &&
		    (ies[1] + 2 >= match_offset + match_len) &&
		    !memcmp(ies + match_offset, match, match_len))
			return ies;

		len -= ies[1] + 2;
		ies += ies[1] + 2;
	}

	return NULL;
}
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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;
}
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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;
}

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/**
 * 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;
	}
}

Contributors
Person
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CommitProp
Johannes Berg
385
77.00%
5
62.50%
Dmitry Tarnyagin
98
19.60%
1
12.50%
Javier Cardona
9
1.80%
1
12.50%
Emmanuel Grumbach
8
1.60%
1
12.50%
Total
500
100.00%
8
100.00%



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;
}

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Dedy Lansky
138
98.57%
1
50.00%
Johannes Berg
2
1.43%
1
50.00%
Total
140
100.00%
2
100.00%

/* 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;
}
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CommitProp
Johannes Berg
184
68.91%
6
60.00%
Dedy Lansky
54
20.22%
1
10.00%
Beni Lev
23
8.61%
1
10.00%
Zhao, Gang
6
2.25%
2
20.00%
Total
267
100.00%
10
100.00%


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);
}

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Johannes Berg
146
97.99%
3
75.00%
Zhao, Gang
3
2.01%
1
25.00%
Total
149
100.00%
4
100.00%


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