mac80211: filter multicast data packets on AP / AP_VLAN

This patch adds filtering for multicast data packets on AP_VLAN
interfaces that have no authorized station connected and changes
filtering on AP interfaces to not count stations assigned to
AP_VLAN interfaces.

This saves airtime and avoids waking up other stations currently
authorized in this BSS. When using WPA, the packets dropped could
not be decrypted by any station.

The behaviour when there are no AP_VLAN interfaces is left unchanged.

When there are AP_VLAN interfaces, this patch
1. adds filtering multicast data packets sent on AP_VLAN interfaces
   that have no authorized station connected.
   No filtering happens on 4addr AP_VLAN interfaces.
2. makes filtering of multicast data packets sent on AP interfaces
   depend on the number of authorized stations in this bss not
   assigned to an AP_VLAN interface.

Therefore, a new num_mcast_sta counter is added for AP_VLAN interfaces.
The existing one for AP interfaces is altered to not track stations
assigned to an AP_VLAN interface.

The new counter is exposed in debugfs.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
[reformat commit message a bit, unline ieee80211_vif_{inc,dec}_num_mcast]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 34c2add2c455..103187ca9474 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -307,6 +307,7 @@ struct ieee80211_if_vlan {
 
 	/* used for all tx if the VLAN is configured to 4-addr mode */
 	struct sta_info __rcu *sta;
+	atomic_t num_mcast_sta; /* number of stations receiving multicast */
 };
 
 struct mesh_stats {
@@ -1527,6 +1528,23 @@ ieee80211_have_rx_timestamp(struct ieee80211_rx_status *status)
 	return false;
 }
 
+void ieee80211_vif_inc_num_mcast(struct ieee80211_sub_if_data *sdata);
+void ieee80211_vif_dec_num_mcast(struct ieee80211_sub_if_data *sdata);
+
+/* This function returns the number of multicast stations connected to this
+ * interface. It returns -1 if that number is not tracked, that is for netdevs
+ * not in AP or AP_VLAN mode or when using 4addr.
+ */
+static inline int
+ieee80211_vif_get_num_mcast_if(struct ieee80211_sub_if_data *sdata)
+{
+	if (sdata->vif.type == NL80211_IFTYPE_AP)
+		return atomic_read(&sdata->u.ap.num_mcast_sta);
+	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN && !sdata->u.vlan.sta)
+		return atomic_read(&sdata->u.vlan.num_mcast_sta);
+	return -1;
+}
+
 u64 ieee80211_calculate_rx_timestamp(struct ieee80211_local *local,
 				     struct ieee80211_rx_status *status,
 				     unsigned int mpdu_len,