vlan: dont drop packets from unknown vlans in promiscuous mode

Roger Luethi noticed packets for unknown VLANs getting silently dropped
even in promiscuous mode.

Check for promiscuous mode in __vlan_hwaccel_rx() and vlan_gro_common()
before drops.

As suggested by Patrick, mark such packets to have skb->pkt_type set to
PACKET_OTHERHOST to make sure they are dropped by IP stack.
Reported-by: Roger Luethi <rl@hellgate.ch>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan_core.c

@@ -24,8 +24,11 @@ int __vlan_hwaccel_rx(struct sk_buff *skb, struct vlan_group *grp,
 
 	if (vlan_dev)
 		skb->dev = vlan_dev;
-	else if (vlan_id)
-		goto drop;
+	else if (vlan_id) {
+		if (!(skb->dev->flags & IFF_PROMISC))
+			goto drop;
+		skb->pkt_type = PACKET_OTHERHOST;
+	}
 
 	return (polling ? netif_receive_skb(skb) : netif_rx(skb));
 
@@ -102,8 +105,11 @@ vlan_gro_common(struct napi_struct *napi, struct vlan_group *grp,
 
 	if (vlan_dev)
 		skb->dev = vlan_dev;
-	else if (vlan_id)
-		goto drop;
+	else if (vlan_id) {
+		if (!(skb->dev->flags & IFF_PROMISC))
+			goto drop;
+		skb->pkt_type = PACKET_OTHERHOST;
+	}
 
 	for (p = napi->gro_list; p; p = p->next) {
 		NAPI_GRO_CB(p)->same_flow =