tipc: introduce jumbo frame support for broadcast

Until now, we have only been supporting a fix MTU size of 1500 bytes
for all broadcast media, irrespective of their actual capability.

We now make the broadcast MTU adaptable to the carrying media, i.e.,
we use the smallest MTU supported by any of the interfaces attached
to TIPC.

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.h b/net/tipc/link.h
index 28a6396..9b5198e9 100644
--- a/net/tipc/link.h
+++ b/net/tipc/link.h
@@ -281,6 +281,8 @@
 			      struct tipc_link *rcv_l,
 			      struct sk_buff_head *xmitq);
 int tipc_link_bc_peers(struct tipc_link *l);
+void tipc_link_set_mtu(struct tipc_link *l, int mtu);
+int tipc_link_mtu(struct tipc_link *l);
 void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
 			  struct sk_buff_head *xmitq);
 void tipc_link_build_bc_sync_msg(struct tipc_link *l,