6LoWPAN: add fragmentation support

This patch adds support for frame fragmentation.

Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ieee802154.h b/include/net/ieee802154.h
index d52685d..ee59f8b 100644
--- a/include/net/ieee802154.h
+++ b/include/net/ieee802154.h
@@ -21,11 +21,14 @@
  * Maxim Gorbachyov <maxim.gorbachev@siemens.com>
  * Maxim Osipov <maxim.osipov@siemens.com>
  * Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
+ * Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
  */
 
 #ifndef NET_IEEE802154_H
 #define NET_IEEE802154_H
 
+#define IEEE802154_MTU			127
+
 #define IEEE802154_FC_TYPE_BEACON	0x0	/* Frame is beacon */
 #define	IEEE802154_FC_TYPE_DATA		0x1	/* Frame is data */
 #define IEEE802154_FC_TYPE_ACK		0x2	/* Frame is acknowledgment */
@@ -56,6 +59,9 @@
 	(((x) & IEEE802154_FC_DAMODE_MASK) >> IEEE802154_FC_DAMODE_SHIFT)
 
 
+/* MAC footer size */
+#define IEEE802154_MFR_SIZE	2 /* 2 octets */
+
 /* MAC's Command Frames Identifiers */
 #define IEEE802154_CMD_ASSOCIATION_REQ		0x01
 #define IEEE802154_CMD_ASSOCIATION_RESP		0x02