ieee802154: 6lowpan: fix non-lowpan wpan interfaces

We receive all 802.15.4 frames on the packet handler "lowpan_rcv" this
patch checks if the wpan device belongs to a lowpan interface.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/ieee802154/6lowpan/rx.c

@@ -67,6 +67,10 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct ieee802154_hdr hdr;
 	int ret;
 
+	if (dev->type != ARPHRD_IEEE802154 ||
+	    !dev->ieee802154_ptr->lowpan_dev)
+		goto drop;
+
 	skb = skb_share_check(skb, GFP_ATOMIC);
 	if (!skb)
 		goto drop;
@@ -77,9 +81,6 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
 	if (skb->pkt_type == PACKET_OTHERHOST)
 		goto drop_skb;
 
-	if (dev->type != ARPHRD_IEEE802154)
-		goto drop_skb;
-
 	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
 		goto drop_skb;