rt2x00: Only update rssi average approximation on receiving beacon frames.

Restrict rssi average updating to beacon frames of the bssid the
interface is
associated with. Without this restriction, strong signals belonging to other
BSS, e.g. beacon frames coming from a nearby AP, would cause incorrectly high
rssi approximation values. This would then cause the link tuner to reduce
sensitivity, resulting in transmissions from the BSS associated to to be
missed.
Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00.h

@@ -32,6 +32,7 @@
 #include <linux/workqueue.h>
 #include <linux/firmware.h>
 #include <linux/mutex.h>
+#include <linux/etherdevice.h>
 
 #include <net/mac80211.h>
 
@@ -149,6 +150,12 @@ static inline int is_probe_resp(u16 fc)
 		((fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_PROBE_RESP));
 }
 
+static inline int is_beacon(u16 fc)
+{
+	return (((fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_MGMT) &&
+		((fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_BEACON));
+}
+
 /*
  * Chipset identification
  * The chipset on the device is composed of a RT and RF chip.

drivers/net/wireless/rt2x00/rt2x00dev.c

@@ -526,11 +526,14 @@ void rt2x00lib_rxdone(struct data_entry *entry, struct sk_buff *skb,
 		      struct rxdata_entry_desc *desc)
 {
 	struct rt2x00_dev *rt2x00dev = entry->ring->rt2x00dev;
+	struct interface *intf = &rt2x00dev->interface;
 	struct ieee80211_rx_status *rx_status = &rt2x00dev->rx_status;
 	struct ieee80211_hw_mode *mode;
 	struct ieee80211_rate *rate;
+	struct ieee80211_hdr *hdr;
 	unsigned int i;
 	int val = 0;
+	u16 fc;
 
 	/*
 	 * Update RX statistics.
@@ -555,7 +558,21 @@ void rt2x00lib_rxdone(struct data_entry *entry, struct sk_buff *skb,
 		}
 	}
 
-	rt2x00lib_update_link_stats(&rt2x00dev->link, desc->rssi);
+	/*
+	 * Only update link status if this is a beacon frame carrying our
+	 * bssid.
+	 */
+	hdr = (struct ieee80211_hdr *) skb->data;
+	if (skb->len >= sizeof(struct ieee80211_hdr *)) {
+		fc = le16_to_cpu(hdr->frame_control);
+		if ((intf->type == IEEE80211_IF_TYPE_STA
+		     || intf->type == IEEE80211_IF_TYPE_IBSS)
+		    && is_beacon(fc)
+		    && compare_ether_addr(hdr->addr3, intf->bssid) == 0)
+			rt2x00lib_update_link_stats(&rt2x00dev->link,
+						    desc->rssi);
+	}
+
 	rt2x00dev->link.qual.rx_success++;
 
 	rx_status->rate = val;