mac80211: fix allmulti/promisc behaviour

When an interface with promisc/allmulti bit is taken down,
the mac80211 state can become confused. This fixes it by
making mac80211 keep track of all *active* interfaces that
have the promisc/allmulti bit set in the sdata, we sync
the interface bit into sdata at set_multicast_list() time
so this works.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211.c

@@ -267,6 +267,17 @@ static int ieee80211_open(struct net_device *dev)
 		tasklet_enable(&local->tasklet);
 	}
 
+	/*
+	 * set_multicast_list will be invoked by the networking core
+	 * which will check whether any increments here were done in
+	 * error and sync them down to the hardware as filter flags.
+	 */
+	if (sdata->flags & IEEE80211_SDATA_ALLMULTI)
+		atomic_inc(&local->iff_allmultis);
+
+	if (sdata->flags & IEEE80211_SDATA_PROMISC)
+		atomic_inc(&local->iff_promiscs);
+
 	local->open_count++;
 
 	netif_start_queue(dev);
@@ -284,6 +295,18 @@ static int ieee80211_stop(struct net_device *dev)
 
 	netif_stop_queue(dev);
 
+	/*
+	 * Don't count this interface for promisc/allmulti while it
+	 * is down. dev_mc_unsync() will invoke set_multicast_list
+	 * on the master interface which will sync these down to the
+	 * hardware as filter flags.
+	 */
+	if (sdata->flags & IEEE80211_SDATA_ALLMULTI)
+		atomic_dec(&local->iff_allmultis);
+
+	if (sdata->flags & IEEE80211_SDATA_PROMISC)
+		atomic_dec(&local->iff_promiscs);
+
 	dev_mc_unsync(local->mdev, dev);
 
 	/* down all dependent devices, that is VLANs */