6lowpan: set and use mac_len for mac header length

Set the mac header length while creating the 802.15.4 mac header.

Drop the function for recalculate mac header length in upper layers
which was static and works for intra pan communication only.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Reviewed-by: Werner Almesberger <werner@almesberger.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan.c

@@ -1100,17 +1100,6 @@ static int lowpan_set_address(struct net_device *dev, void *p)
 	return 0;
 }
 
-static int lowpan_get_mac_header_length(struct sk_buff *skb)
-{
-	/*
-	 * Currently long addressing mode is supported only, so the overall
-	 * header size is 21:
-	 * FC SeqNum DPAN DA  SA  Sec
-	 * 2  +  1  +  2 + 8 + 8 + 0  = 21
-	 */
-	return 21;
-}
-
 static int
 lowpan_fragment_xmit(struct sk_buff *skb, u8 *head,
 			int mlen, int plen, int offset, int type)
@@ -1150,7 +1139,7 @@ lowpan_skb_fragmentation(struct sk_buff *skb, struct net_device *dev)
 	int  err, header_length, payload_length, tag, offset = 0;
 	u8 head[5];
 
-	header_length = lowpan_get_mac_header_length(skb);
+	header_length = skb->mac_len;
 	payload_length = skb->len - header_length;
 	tag = lowpan_dev_info(dev)->fragment_tag++;
 

net/mac802154/wpan.c

@@ -208,6 +208,8 @@ static int mac802154_header_create(struct sk_buff *skb,
 	head[1] = fc >> 8;
 
 	memcpy(skb_push(skb, pos), head, pos);
+	skb_reset_mac_header(skb);
+	skb->mac_len = pos;
 
 	return pos;
 }