mac80211: MBSSID support in interface handling

Configure multiple BSSID and enhanced multi-BSSID advertisement (EMA)
parameters in mac80211 for AP mode.

For each interface, 'mbssid_tx_vif' points to the transmitting interface of
the MBSSID set. The pointer is set to NULL if MBSSID is disabled.

Function ieee80211_stop() is modified to always bring down all the
non-transmitting interfaces first and the transmitting interface last.

Signed-off-by: John Crispin <john@phrozen.org>
Co-developed-by: Aloka Dixit <alokad@codeaurora.org>
Signed-off-by: Aloka Dixit <alokad@codeaurora.org>
Link: https://lore.kernel.org/r/20210916025437.29138-3-alokad@codeaurora.org
[slightly change logic to be more obvious]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 16a9652..13cad5e 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1723,6 +1723,7 @@ enum ieee80211_offload_flags {
  *	write-protected by sdata_lock and local->mtx so holding either is fine
  *	for read access.
  * @color_change_color: the bss color that will be used after the change.
+ * @mbssid_tx_vif: Pointer to the transmitting interface if MBSSID is enabled.
  */
 struct ieee80211_vif {
 	enum nl80211_iftype type;
@@ -1754,6 +1755,8 @@ struct ieee80211_vif {
 	bool color_change_active;
 	u8 color_change_color;
 
+	struct ieee80211_vif *mbssid_tx_vif;
+
 	/* must be last */
 	u8 drv_priv[] __aligned(sizeof(void *));
 };