mac80211: fix num_mcast_sta counting issues

Moving a STA to an AP VLAN prevents num_mcast_sta from being decremented
once the STA leaves, because sta->sdata changes. Fix this by checking
for AP VLANs as well.

Also exclude 4-addr VLAN stations from num_mcast_sta - remote 4-addr
stations ignore 3-address multicast frames anyway. In a typical bridge
configuration they receive the same packets as 4-address unicast.

This patch also fixes clearing the sdata->u.vlan.sta pointer when the
STA is removed from a 4-addr VLAN.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 510a745c3108..70b2af2315a6 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1005,6 +1005,9 @@ static int ieee80211_change_station(struct wiphy *wiphy,
         }
 
         if (params->vlan && params->vlan != sta->sdata->dev) {
+                bool prev_4addr = false;
+                bool new_4addr = false;
+
                 vlansdata = IEEE80211_DEV_TO_SUB_IF(params->vlan);
 
                 if (vlansdata->vif.type != NL80211_IFTYPE_AP_VLAN &&
@@ -1020,9 +1023,25 @@ static int ieee80211_change_station(struct wiphy *wiphy,
                         }
 
                         rcu_assign_pointer(vlansdata->u.vlan.sta, sta);
+                        new_4addr = true;
+                }
+
+                if (sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
+                    sta->sdata->u.vlan.sta) {
+                        rcu_assign_pointer(sta->sdata->u.vlan.sta, NULL);
+                        prev_4addr = true;
                 }
 
                 sta->sdata = vlansdata;
+
+                if (sta->sta_state == IEEE80211_STA_AUTHORIZED &&
+                    prev_4addr != new_4addr) {
+                        if (new_4addr)
+                                atomic_dec(&sta->sdata->bss->num_mcast_sta);
+                        else
+                                atomic_inc(&sta->sdata->bss->num_mcast_sta);
+                }
+
                 ieee80211_send_layer2_update(sta);
         }