Add notion of upstream that is separate from root in Topology, etc.

node/Packet.hpp

@@ -617,10 +617,8 @@ public:
 		 *   <[1] protocol address length (4 for IPv4, 16 for IPv6)>
 		 *   <[...] protocol address (network byte order)>
 		 *
-		 * This is sent by a relaying node to initiate NAT traversal between two
-		 * peers that are communicating by way of indirect relay. The relay will
-		 * send this to both peers at the same time on a periodic basis, telling
-		 * each where it might find the other on the network.
+		 * An upstream node can send this to inform both sides of a relay of
+		 * information they might use to establish a direct connection.
 		 *
 		 * Upon receipt a peer sends HELLO to establish a direct link.
 		 *
@@ -1051,7 +1049,18 @@ public:
 		 * OK or ERROR and has no special semantics outside of whatever the user
 		 * (via the ZeroTier core API) chooses to give it.
 		 */
-		VERB_USER_MESSAGE = 0x14
+		VERB_USER_MESSAGE = 0x14,
+
+		/**
+		 * Information related to federation and mesh-like behavior:
+		 *   <[2] 16-bit length of Dictionary>
+		 *   <[...] topology definition info Dictionary>
+		 *
+		 * This message can carry information that can be used to define topology
+		 * and implement "mesh-like" behavior. It can optionally generate OK or
+		 * ERROR, and these carry the same payload.
+		 */
+		VERB_TOPOLOGY_HINT = 0x15
 	};
 
 	/**