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Commit dd9dfb9f authored by Dmitry Tarnyagin's avatar Dmitry Tarnyagin Committed by John W. Linville
Browse files

cfg80211: merge in beacon ies of hidden bss. 



The problem with PSM when a hidden SSID was used was originally
reported by Juuso Oikarinen.

 - When generally scanning, the AP is getting a bss entry with
   a zero SSID.
 - When associating, a probe-req is sent to the AP with the SSID,
   and as a result a probe-response is received with the hidden
   SSID in place. As a consequence, a second bss entry is created
   for the AP, now with the real SSID.
 - After association, mac80211 executes ieee80211_recalc_ps(),
   but does not switch to powersave because the beacon-ies are missing.

As result, the STA does not ever enter PSM.

The patch merges in beacon ies of hidden bss from beacon to the probe
response, creating a consistent set of ies in place.

Patch is depended on "cfg80211: fix cmp_ies" made by Johannes.

Signed-off-by: default avatarDmitry Tarnyagin <dmitry.tarnyagin@stericsson.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 1eb54c8a

net/wireless/scan.c

+114 −3
Original line number Diff line number Diff line
@@ -355,7 +355,7 @@ static bool is_mesh(struct cfg80211_bss *a, 
	    sizeof(struct ieee80211_meshconf_ie) - 2) == 0;

}



static int cmp_bss(struct cfg80211_bss *a,

static int cmp_bss_core(struct cfg80211_bss *a,

			struct cfg80211_bss *b)

{

	int r;
@@ -378,7 +378,15 @@ static int cmp_bss(struct cfg80211_bss *a, 
			       b->len_information_elements);

	}



	r = memcmp(a->bssid, b->bssid, ETH_ALEN);

	return memcmp(a->bssid, b->bssid, ETH_ALEN);

}



static int cmp_bss(struct cfg80211_bss *a,

		   struct cfg80211_bss *b)

{

	int r;



	r = cmp_bss_core(a, b);

	if (r)

		return r;
@@ -389,6 +397,52 @@ static int cmp_bss(struct cfg80211_bss *a, 
		       b->len_information_elements);

}



static int cmp_hidden_bss(struct cfg80211_bss *a,

		   struct cfg80211_bss *b)

{

	const u8 *ie1;

	const u8 *ie2;

	int i;

	int r;



	r = cmp_bss_core(a, b);

	if (r)

		return r;



	ie1 = cfg80211_find_ie(WLAN_EID_SSID,

			a->information_elements,

			a->len_information_elements);

	ie2 = cfg80211_find_ie(WLAN_EID_SSID,

			b->information_elements,

			b->len_information_elements);



	/* Key comparator must use same algorithm in any rb-tree

	 * search function (order is important), otherwise ordering

	 * of items in the tree is broken and search gives incorrect

	 * results. This code uses same order as cmp_ies() does. */



	/* sort missing IE before (left of) present IE */

	if (!ie1)

		return -1;

	if (!ie2)

		return 1;



	/* zero-size SSID is used as an indication of the hidden bss */

	if (!ie2[1])

		return 0;



	/* sort by length first, then by contents */

	if (ie1[1] != ie2[1])

		return ie2[1] - ie1[1];



	/* zeroed SSID ie is another indication of a hidden bss */

	for (i = 0; i < ie2[1]; i++)

		if (ie2[i + 2])

			return -1;



	return 0;

}



struct cfg80211_bss *cfg80211_get_bss(struct wiphy *wiphy,

				      struct ieee80211_channel *channel,

				      const u8 *bssid,
@@ -504,6 +558,48 @@ rb_find_bss(struct cfg80211_registered_device *dev, 
	return NULL;

}



static struct cfg80211_internal_bss *

rb_find_hidden_bss(struct cfg80211_registered_device *dev,

	    struct cfg80211_internal_bss *res)

{

	struct rb_node *n = dev->bss_tree.rb_node;

	struct cfg80211_internal_bss *bss;

	int r;



	while (n) {

		bss = rb_entry(n, struct cfg80211_internal_bss, rbn);

		r = cmp_hidden_bss(&res->pub, &bss->pub);



		if (r == 0)

			return bss;

		else if (r < 0)

			n = n->rb_left;

		else

			n = n->rb_right;

	}



	return NULL;

}



static void

copy_hidden_ies(struct cfg80211_internal_bss *res,

		 struct cfg80211_internal_bss *hidden)

{

	if (unlikely(res->pub.beacon_ies))

		return;

	if (WARN_ON(!hidden->pub.beacon_ies))

		return;



	res->pub.beacon_ies = kmalloc(hidden->pub.len_beacon_ies, GFP_ATOMIC);

	if (unlikely(!res->pub.beacon_ies))

		return;



	res->beacon_ies_allocated = true;

	res->pub.len_beacon_ies = hidden->pub.len_beacon_ies;

	memcpy(res->pub.beacon_ies, hidden->pub.beacon_ies,

			res->pub.len_beacon_ies);

}



static struct cfg80211_internal_bss *

cfg80211_bss_update(struct cfg80211_registered_device *dev,

		    struct cfg80211_internal_bss *res)
@@ -607,6 +703,21 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev, 


		kref_put(&res->ref, bss_release);

	} else {

		struct cfg80211_internal_bss *hidden;



		/* First check if the beacon is a probe response from

		 * a hidden bss. If so, copy beacon ies (with nullified

		 * ssid) into the probe response bss entry (with real ssid).

		 * It is required basically for PSM implementation

		 * (probe responses do not contain tim ie) */



		/* TODO: The code is not trying to update existing probe

		 * response bss entries when beacon ies are

		 * getting changed. */

		hidden = rb_find_hidden_bss(dev, res);

		if (hidden)

			copy_hidden_ies(res, hidden);



		/* this "consumes" the reference */

		list_add_tail(&res->list, &dev->bss_list);

		rb_insert_bss(dev, res);