rt2x00: Forbid aggregation for STAs not programmed into the hw

If a STA is not known by the hw (i.e. has no WCID assigned) don't allow
aggregation since this might mess up tx status reports and we won't be
able to distinguish the reports of multiple WCID-less STAs.
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -4484,8 +4484,19 @@ int rt2800_ampdu_action(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 			struct ieee80211_sta *sta, u16 tid, u16 *ssn,
 			u8 buf_size)
 {
+	struct rt2x00_sta *sta_priv = (struct rt2x00_sta *)sta->drv_priv;
 	int ret = 0;
 
+	/*
+	 * Don't allow aggregation for stations the hardware isn't aware
+	 * of because tx status reports for frames to an unknown station
+	 * always contain wcid=255 and thus we can't distinguish between
+	 * multiple stations which leads to unwanted situations when the
+	 * hw reorders frames due to aggregation.
+	 */
+	if (sta_priv->wcid < 0)
+		return 1;
+
 	switch (action) {
 	case IEEE80211_AMPDU_RX_START:
 	case IEEE80211_AMPDU_RX_STOP: