core-utils: use 64-bit WPAN address for a 6LoWPAN IID

If the hardware address is a 64-bit value it can be used directly as an
IEEE EUI-64 address when generating an interface identifier.

src/nm-core-utils.c

@@ -15,7 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *
- * Copyright 2004 - 2014 Red Hat, Inc.
+ * Copyright 2004 - 2018 Red Hat, Inc.
  * Copyright 2005 - 2008 Novell, Inc.
  */
 
@@ -3018,6 +3018,11 @@ nm_utils_get_ipv6_interface_identifier (NMLinkType link_type,
 		out_iid->id_u8[3] = 0xFE;
 		memcpy (out_iid->id_u8 + 4, &addr, 4);
 		return TRUE;
+	case NM_LINK_TYPE_6LOWPAN:
+		/* The hardware address is already 64-bit. This is the case for
+		* IEEE 802.15.4 networks. */
+		memcpy (out_iid->id_u8, hwaddr, sizeof (out_iid->id_u8));
+		return TRUE;
 	default:
 		if (hwaddr_len == ETH_ALEN) {
 			/* Translate 48-bit MAC address to a 64-bit Modified EUI-64.  See