l2tp: netlink api for l2tpv3 ipv6 unmanaged tunnels

This patch adds support for unmanaged L2TPv3 tunnels over IPv6 using
the netlink API. We already support unmanaged L2TPv3 tunnels over
IPv4. A patch to iproute2 to make use of this feature will be
submitted separately.

Signed-off-by: Chris Elston <celston@katalix.com>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/l2tp.h b/include/linux/l2tp.h
index e77d7f9..16b8347 100644
--- a/include/linux/l2tp.h
+++ b/include/linux/l2tp.h
@@ -108,6 +108,8 @@
 	L2TP_ATTR_MTU,			/* u16 */
 	L2TP_ATTR_MRU,			/* u16 */
 	L2TP_ATTR_STATS,		/* nested */
+	L2TP_ATTR_IP6_SADDR,		/* struct in6_addr */
+	L2TP_ATTR_IP6_DADDR,		/* struct in6_addr */
 	__L2TP_ATTR_MAX,
 };