tipc: introduce capability bit for broadcast synchronization

Until now, we have tried to support both the newer, dedicated broadcast
synchronization mechanism along with the older, less safe, RESET_MSG/
ACTIVATE_MSG based one. The latter method has turned out to be a hazard
in a highly dynamic cluster, so we find it safer to disable it completely
when we find that the former mechanism is supported by the peer node.

For this purpose, we now introduce a new capabability bit,
TIPC_BCAST_SYNCH, to inform any peer nodes that dedicated broadcast
syncronization is supported by the present node. The new bit is conveyed
between peers in the 'capabilities' field of neighbor discovery messages.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/link.c b/net/tipc/link.c
index 363da5f..6a1a9d9 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -191,6 +191,7 @@
  * @session: session to be used by link
  * @ownnode: identity of own node
  * @peer: node id of peer node
+ * @peer_caps: bitmap describing peer node capabilities
  * @maddr: media address to be used
  * @inputq: queue to put messages ready for delivery
  * @namedq: queue to put binding table update messages ready for delivery
@@ -201,7 +202,7 @@
 bool tipc_link_create(struct tipc_node *n, char *if_name, int bearer_id,
 		      int tolerance, char net_plane, u32 mtu, int priority,
 		      int window, u32 session, u32 ownnode, u32 peer,
-		      struct tipc_media_addr *maddr,
+		      u16 peer_caps, struct tipc_media_addr *maddr,
 		      struct sk_buff_head *inputq, struct sk_buff_head *namedq,
 		      struct tipc_link **link)
 {
@@ -226,6 +227,7 @@
 	strcpy((char *)msg_data(hdr), if_name);
 
 	l->addr = peer;
+	l->peer_caps = peer_caps;
 	l->media_addr = maddr;
 	l->owner = n;
 	l->peer_session = WILDCARD_SESSION;
@@ -260,6 +262,7 @@
  * Returns true if link was created, otherwise false
  */
 bool tipc_link_bc_create(struct tipc_node *n, int mtu, int window,
+			 u16 peer_caps,
 			 struct sk_buff_head *inputq,
 			 struct sk_buff_head *namedq,
 			 struct tipc_link **link)
@@ -267,7 +270,7 @@
 	struct tipc_link *l;
 
 	if (!tipc_link_create(n, "", MAX_BEARERS, 0, 'Z', mtu, 0, window,
-			      0, 0, 0, NULL, inputq, namedq, link))
+			      0, 0, 0, peer_caps, NULL, inputq, namedq, link))
 		return false;
 
 	l = *link;