Finally add an ECHO.

node/IncomingPacket.cpp

@@ -83,6 +83,7 @@ bool IncomingPacket::tryDecode(const RuntimeEnvironment *RR)
 				case Packet::VERB_RENDEZVOUS:                     return _doRENDEZVOUS(RR,peer);
 				case Packet::VERB_FRAME:                          return _doFRAME(RR,peer);
 				case Packet::VERB_EXT_FRAME:                      return _doEXT_FRAME(RR,peer);
+				case Packet::VERB_ECHO:                           return _doECHO(RR,peer);
 				case Packet::VERB_MULTICAST_LIKE:                 return _doMULTICAST_LIKE(RR,peer);
 				case Packet::VERB_NETWORK_MEMBERSHIP_CERTIFICATE: return _doNETWORK_MEMBERSHIP_CERTIFICATE(RR,peer);
 				case Packet::VERB_NETWORK_CONFIG_REQUEST:         return _doNETWORK_CONFIG_REQUEST(RR,peer);
@@ -569,6 +570,18 @@ bool IncomingPacket::_doEXT_FRAME(const RuntimeEnvironment *RR,const SharedPtr<P
 	return true;
 }
 
+bool IncomingPacket::_doECHO(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer)
+{
+	try {
+		Packet outp(peer->address(),RR->identity.address(),Packet::VERB_OK);
+		outp.append((unsigned char)Packet::VERB_ECHO);
+		outp.append(packetId());
+		outp.append(field(ZT_PACKET_IDX_PAYLOAD,size() - ZT_PACKET_IDX_PAYLOAD),size() - ZT_PACKET_IDX_PAYLOAD);
+		RR->sw->send(outp,true,0);
+	} catch ( ... ) {}
+	return true;
+}
+
 bool IncomingPacket::_doMULTICAST_LIKE(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer)
 {
 	try {
@@ -636,7 +649,7 @@ bool IncomingPacket::_doNETWORK_CONFIG_REQUEST(const RuntimeEnvironment *RR,cons
 						outp.append(netconfStr.data(),(unsigned int)netconfStr.length());
 						outp.compress();
 						outp.armor(peer->key(),true);
-						if (outp.size() > ZT_PROTO_MAX_PACKET_LENGTH) {
+						if (outp.size() > ZT_PROTO_MAX_PACKET_LENGTH) { // sanity check
 							TRACE("NETWORK_CONFIG_REQUEST failed: internal error: netconf size %u is too large",(unsigned int)netconfStr.length());
 						} else {
 							RR->node->putPacket(_localAddress,_remoteAddress,outp.data(),outp.size());

node/IncomingPacket.hpp

@@ -138,6 +138,7 @@ private:
 	bool _doRENDEZVOUS(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
 	bool _doFRAME(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
 	bool _doEXT_FRAME(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
+	bool _doECHO(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
 	bool _doMULTICAST_LIKE(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
 	bool _doNETWORK_MEMBERSHIP_CERTIFICATE(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);
 	bool _doNETWORK_CONFIG_REQUEST(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer);

node/Packet.cpp

@@ -45,6 +45,7 @@ const char *Packet::verbString(Verb v)
 		case VERB_RENDEZVOUS: return "RENDEZVOUS";
 		case VERB_FRAME: return "FRAME";
 		case VERB_EXT_FRAME: return "EXT_FRAME";
+		case VERB_ECHO: return "ECHO";
 		case VERB_MULTICAST_LIKE: return "MULTICAST_LIKE";
 		case VERB_NETWORK_MEMBERSHIP_CERTIFICATE: return "NETWORK_MEMBERSHIP_CERTIFICATE";
 		case VERB_NETWORK_CONFIG_REQUEST: return "NETWORK_CONFIG_REQUEST";

node/Packet.hpp

@@ -46,22 +46,20 @@
 #include "../ext/lz4/lz4.h"
 
 /**
- * Protocol version -- incremented only for MAJOR changes
+ * Protocol version -- incremented only for major changes
  *
  * 1 - 0.2.0 ... 0.2.5
  * 2 - 0.3.0 ... 0.4.5
- *   * Added signature and originating peer to multicast frame
- *   * Double size of multicast frame bloom filter
+ *   + Added signature and originating peer to multicast frame
+ *   + Double size of multicast frame bloom filter
  * 3 - 0.5.0 ... 0.6.0
- *   * Yet another multicast redesign
- *   * New crypto completely changes key agreement cipher
+ *   + Yet another multicast redesign
+ *   + New crypto completely changes key agreement cipher
  * 4 - 0.6.0 ... 1.0.6
- *   * New identity format based on hashcash design
+ *   + New identity format based on hashcash design
  * 5 - 1.0.6 ... CURRENT
- *   * Supports CIRCUIT_TEST and friends, otherwise compatibie w/v4
- *
- * This isn't going to change again for a long time unless your
- * author wakes up again at 4am with another great idea. :P
+ *   + Supports circuit test, proof of work, and echo
+ *   + Otherwise backward compatible with 4
  */
 #define ZT_PROTO_VERSION 5
 
@@ -660,8 +658,14 @@ public:
 		 */
 		VERB_EXT_FRAME = 7,
 
-		/* DEPRECATED */
-		//VERB_P5_MULTICAST_FRAME = 8,
+		/**
+		 * ECHO request (a.k.a. ping):
+		 *   <[...] arbitrary payload to be echoed back>
+		 *
+		 * This generates OK with a copy of the transmitted payload. No ERROR
+		 * is generated. Response to ECHO requests is optional.
+		 */
+		VERB_ECHO = 8,
 
 		/**
 		 * Announce interest in multicast group(s):