tipc: add support for link state subscriptions

When links are established over a bearer plane, we create a node
local publication containing information about the peer node and
bearer plane. This allows TIPC applications to use the standard
TIPC topology server subscription mechanism to get notifications
when a link goes up or down.

Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/tipc.h b/include/uapi/linux/tipc.h
index 852373d..53cd790 100644
--- a/include/uapi/linux/tipc.h
+++ b/include/uapi/linux/tipc.h
@@ -87,6 +87,7 @@
 
 #define TIPC_CFG_SRV		0	/* configuration service name type */
 #define TIPC_TOP_SRV		1	/* topology service name type */
+#define TIPC_LINK_STATE		2	/* link state name type */
 #define TIPC_RESERVED_TYPES	64	/* lowest user-publishable name type */
 
 /*