bluetooth: 6lowpan: use lowpan dispatch helpers

This patch adds a check if the dataroom of skb contains a dispatch value
by checking if skb->len != 0. This patch also change the dispatch
evaluation by the recently introduced helpers for checking the common
6LoWPAN dispatch values for IPv6 and IPHC header.

There was also a forgotten else branch which should drop the packet if
no matching dispatch is available.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/6lowpan.c

@@ -314,15 +314,17 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 	if (!netif_running(dev))
 		goto drop;
 
-	if (dev->type != ARPHRD_6LOWPAN)
+	if (dev->type != ARPHRD_6LOWPAN || !skb->len)
 		goto drop;
 
+	skb_reset_network_header(skb);
+
 	skb = skb_share_check(skb, GFP_ATOMIC);
 	if (!skb)
 		goto drop;
 
 	/* check that it's our buffer */
-	if (skb->data[0] == LOWPAN_DISPATCH_IPV6) {
+	if (lowpan_is_ipv6(*skb_network_header(skb))) {
 		/* Copy the packet so that the IPv6 header is
 		 * properly aligned.
 		 */
@@ -334,7 +336,6 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 		local_skb->protocol = htons(ETH_P_IPV6);
 		local_skb->pkt_type = PACKET_HOST;
 
-		skb_reset_network_header(local_skb);
 		skb_set_transport_header(local_skb, sizeof(struct ipv6hdr));
 
 		if (give_skb_to_upper(local_skb, dev) != NET_RX_SUCCESS) {
@@ -347,9 +348,7 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 
 		consume_skb(local_skb);
 		consume_skb(skb);
-	} else {
-		switch (skb->data[0] & 0xe0) {
-		case LOWPAN_DISPATCH_IPHC:	/* ipv6 datagram */
+	} else if (lowpan_is_iphc(*skb_network_header(skb))) {
 		local_skb = skb_clone(skb, GFP_ATOMIC);
 		if (!local_skb)
 			goto drop;
@@ -375,10 +374,8 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
 
 		consume_skb(local_skb);
 		consume_skb(skb);
-			break;
-		default:
-			break;
-		}
+	} else {
+		goto drop;
 	}
 
 	return NET_RX_SUCCESS;