mac80211: allow driver to prevent two stations w/ same address

Some devices or drivers cannot deal with having the same station
address for different virtual interfaces, say as a client to two
virtual AP interfaces. Rather than requiring each driver with a
limitation like that to enforce it, add a hardware flag for it.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -1901,6 +1901,11 @@ struct ieee80211_txq {
  * @IEEE80211_HW_BEACON_TX_STATUS: The device/driver provides TX status
  *	for sent beacons.
  *
+ * @IEEE80211_HW_NEEDS_UNIQUE_STA_ADDR: Hardware (or driver) requires that each
+ *	station has a unique address, i.e. each station entry can be identified
+ *	by just its MAC address; this prevents, for example, the same station
+ *	from connecting to two virtual AP interfaces at the same time.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
@@ -1936,6 +1941,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_TDLS_WIDER_BW,
 	IEEE80211_HW_SUPPORTS_AMSDU_IN_AMPDU,
 	IEEE80211_HW_BEACON_TX_STATUS,
+	IEEE80211_HW_NEEDS_UNIQUE_STA_ADDR,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS