TCP fallback tunneling is now working. That hurt more than expected.

node/Node.cpp

@@ -77,7 +77,6 @@ Node::Node(
 	_networks(),
 	_networks_m(),
 	_now(now),
-	_startTimeAfterInactivity(0),
 	_lastPingCheck(0),
 	_lastHousekeepingRun(0),
 	_lastBeacon(0)
@@ -217,17 +216,12 @@ ZT1_ResultCode Node::processBackgroundTasks(uint64_t now,volatile uint64_t *next
 	if ((now - _lastPingCheck) >= ZT_PING_CHECK_INVERVAL) {
 		_lastPingCheck = now;
 
-		// This is used to compute whether we appear to be "online" or not
-		if ((now - _startTimeAfterInactivity) > (ZT_PING_CHECK_INVERVAL * 3))
-			_startTimeAfterInactivity = now;
-
 		try {
 			_PingPeersThatNeedPing pfunc(RR,now);
 			RR->topology->eachPeer<_PingPeersThatNeedPing &>(pfunc);
 
-			const uint64_t lastActivityAgo = now - std::max(_startTimeAfterInactivity,pfunc.lastReceiveFromUpstream);
 			bool oldOnline = _online;
-			_online = (lastActivityAgo < ZT_PEER_ACTIVITY_TIMEOUT);
+			_online = ((now - pfunc.lastReceiveFromUpstream) < ZT_PEER_ACTIVITY_TIMEOUT);
 			if (oldOnline != _online)
 				postEvent(_online ? ZT1_EVENT_ONLINE : ZT1_EVENT_OFFLINE);
 		} catch ( ... ) {

node/Node.hpp

@@ -229,7 +229,6 @@ private:
 	Mutex _backgroundTasksLock;
 
 	uint64_t _now;
-	uint64_t _startTimeAfterInactivity;
 	uint64_t _lastPingCheck;
 	uint64_t _lastHousekeepingRun;
 	uint64_t _lastBeacon;

service/ControlPlane.cpp

@@ -360,18 +360,20 @@ unsigned int ControlPlane::handleRequest(
 				_node->status(&status);
 				Utils::snprintf(json,sizeof(json),
 					"{\n"
-					"\t\"address\":\"%.10llx\",\n"
-					"\t\"publicIdentity\":\"%s\",\n"
-					"\t\"online\":%s,\n"
-					"\t\"versionMajor\":%d,\n"
-					"\t\"versionMinor\":%d,\n"
-					"\t\"versionRev\":%d,\n"
-					"\t\"version\":\"%d.%d.%d\",\n"
+					"\t\"address\": \"%.10llx\",\n"
+					"\t\"publicIdentity\": \"%s\",\n"
+					"\t\"online\": %s,\n"
+					"\t\"tcpFallbackActive\": %s,\n"
+					"\t\"versionMajor\": %d,\n"
+					"\t\"versionMinor\": %d,\n"
+					"\t\"versionRev\": %d,\n"
+					"\t\"version\": \"%d.%d.%d\",\n"
 					"\t\"clock\": %llu\n"
 					"}\n",
 					status.address,
 					status.publicIdentity,
 					(status.online) ? "true" : "false",
+					(_svc->tcpFallbackActive()) ? "true" : "false",
 					ZEROTIER_ONE_VERSION_MAJOR,
 					ZEROTIER_ONE_VERSION_MINOR,
 					ZEROTIER_ONE_VERSION_REVISION,

service/OneService.cpp

@@ -58,6 +58,16 @@
 #include "OneService.hpp"
 #include "ControlPlane.hpp"
 
+/**
+ * Uncomment to enable UDP breakage switch
+ *
+ * If this is defined, the presence of a file called /tmp/ZT_BREAK_UDP
+ * will cause direct UDP TX/RX to stop working. This can be used to
+ * test TCP tunneling fallback and other robustness features. Deleting
+ * this file will cause it to start working again.
+ */
+//#define ZT_BREAK_UDP
+
 #ifdef ZT_ENABLE_NETWORK_CONTROLLER
 #include "../controller/SqliteNetworkController.hpp"
 #else
@@ -369,6 +379,7 @@ struct TcpConnection
 	std::string body;
 
 	std::string writeBuf;
+	Mutex writeBuf_m;
 };
 
 class OneServiceImpl : public OneService
@@ -380,12 +391,13 @@ public:
 #ifdef ZT_ENABLE_NETWORK_CONTROLLER
 		_controller((_homePath + ZT_PATH_SEPARATOR_S + ZT1_CONTROLLER_DB_PATH).c_str()),
 #endif
-		_phy(this,true),
+		_phy(this,false),
 		_overrideRootTopology((overrideRootTopology) ? overrideRootTopology : ""),
 		_node((Node *)0),
 		_controlPlane((ControlPlane *)0),
 		_lastDirectReceiveFromGlobal(0),
 		_lastSendToGlobal(0),
+		_lastRestart(0),
 		_nextBackgroundTaskDeadline(0),
 		_tcpFallbackTunnel((TcpConnection *)0),
 		_termReason(ONE_STILL_RUNNING),
@@ -481,6 +493,8 @@ public:
 			}
 
 			_nextBackgroundTaskDeadline = 0;
+			uint64_t clockShouldBe = OSUtils::now();
+			_lastRestart = clockShouldBe;
 			uint64_t lastTapMulticastGroupCheck = 0;
 			uint64_t lastTcpFallbackResolve = 0;
 #ifdef ZT_AUTO_UPDATE
@@ -496,13 +510,18 @@ public:
 					break;
 				} else _run_m.unlock();
 
-				uint64_t dl = _nextBackgroundTaskDeadline;
 				uint64_t now = OSUtils::now();
+
+				uint64_t dl = _nextBackgroundTaskDeadline;
 				if (dl <= now) {
 					_node->processBackgroundTasks(now,&_nextBackgroundTaskDeadline);
 					dl = _nextBackgroundTaskDeadline;
 				}
 
+				// Attempt to detect sleep/wake events by detecting delay overruns
+				if ((now > clockShouldBe)&&((now - clockShouldBe) > 2000))
+					_lastRestart = now;
+
 #ifdef ZT_AUTO_UPDATE
 				if ((now - lastSoftwareUpdateCheck) >= ZT_AUTO_UPDATE_CHECK_PERIOD) {
 					lastSoftwareUpdateCheck = OSUtils::now();
@@ -532,6 +551,7 @@ public:
 				}
 
 				const unsigned long delay = (dl > now) ? (unsigned long)(dl - now) : 100;
+				clockShouldBe = now + (uint64_t)delay;
 				_phy.poll(delay);
 			}
 		} catch (std::exception &exc) {
@@ -585,6 +605,11 @@ public:
 		return std::string();
 	}
 
+	virtual bool tcpFallbackActive() const
+	{
+		return (_tcpFallbackTunnel != (TcpConnection *)0);
+	}
+
 	virtual void terminate()
 	{
 		_run_m.lock();
@@ -597,7 +622,11 @@ public:
 
 	inline void phyOnDatagram(PhySocket *sock,void **uptr,const struct sockaddr *from,void *data,unsigned long len)
 	{
-		if (reinterpret_cast<const InetAddress *>(from)->ipScope() == InetAddress::IP_SCOPE_GLOBAL)
+#ifdef ZT_BREAK_UDP
+		if (OSUtils::fileExists("/tmp/ZT_BREAK_UDP"))
+			return;
+#endif
+		if ((len >= 16)&&(reinterpret_cast<const InetAddress *>(from)->ipScope() == InetAddress::IP_SCOPE_GLOBAL))
 			_lastDirectReceiveFromGlobal = OSUtils::now();
 		ZT1_ResultCode rc = _node->processWirePacket(
 			OSUtils::now(),
@@ -624,7 +653,7 @@ public:
 
 		TcpConnection *tc = &(_tcpConnections[sock]);
 		tc->type = TcpConnection::TCP_TUNNEL_OUTGOING;
-		tc->shouldKeepAlive = true; // unused
+		tc->shouldKeepAlive = true;
 		tc->parent = this;
 		tc->sock = sock;
 		// from and parser are not used
@@ -634,8 +663,6 @@ public:
 		tc->writeBuf = "";
 		*uptr = (void *)tc;
 
-		_tcpFallbackTunnel = tc;
-
 		// Send "hello" message
 		tc->writeBuf.push_back((char)0x17);
 		tc->writeBuf.push_back((char)0x03);
@@ -647,6 +674,8 @@ public:
 		tc->writeBuf.push_back((char)((ZEROTIER_ONE_VERSION_REVISION >> 8) & 0xff));
 		tc->writeBuf.push_back((char)(ZEROTIER_ONE_VERSION_REVISION & 0xff));
 		_phy.tcpSetNotifyWritable(sock,true);
+
+		_tcpFallbackTunnel = tc;
 	}
 
 	inline void phyOnTcpAccept(PhySocket *sockL,PhySocket *sockN,void **uptrL,void **uptrN,const struct sockaddr *from)
@@ -699,11 +728,7 @@ public:
 
 			case TcpConnection::TCP_TUNNEL_OUTGOING:
 				tc->body.append((const char *)data,len);
-				if (tc->body.length() > 65535) {
-					// sanity limit -- a message will never be this big since mlen is 16-bit
-					_phy.close(sock);
-					return;
-				} else if (tc->body.length() >= 5) {
+				while (tc->body.length() >= 5) {
 					const char *data = tc->body.data();
 					const unsigned long mlen = ( ((((unsigned long)data[3]) & 0xff) << 8) | (((unsigned long)data[4]) & 0xff) );
 					if (tc->body.length() >= (mlen + 5)) {
@@ -768,7 +793,7 @@ public:
 						if (tc->body.length() > (mlen + 5))
 							tc->body = tc->body.substr(mlen + 5);
 						else tc->body = "";
-					}
+					} else break;
 				}
 				break;
 
@@ -778,18 +803,23 @@ public:
 	inline void phyOnTcpWritable(PhySocket *sock,void **uptr)
 	{
 		TcpConnection *tc = reinterpret_cast<TcpConnection *>(*uptr);
-		if (tc->writeBuf.length()) {
+		Mutex::Lock _l(tc->writeBuf_m);
+		if (tc->writeBuf.length() > 0) {
 			long sent = (long)_phy.tcpSend(sock,tc->writeBuf.data(),(unsigned long)tc->writeBuf.length(),true);
 			if (sent > 0) {
 				tc->lastActivity = OSUtils::now();
-				if ((unsigned long)sent == (unsigned long)tc->writeBuf.length()) {
+				if ((unsigned long)sent >= (unsigned long)tc->writeBuf.length()) {
 					tc->writeBuf = "";
 					_phy.tcpSetNotifyWritable(sock,false);
 					if (!tc->shouldKeepAlive)
 						_phy.close(sock); // will call close handler to delete from _tcpConnections
-				} else tc->writeBuf = tc->writeBuf.substr(sent);
+				} else {
+					tc->writeBuf = tc->writeBuf.substr(sent);
+				}
 			}
-		} else _phy.tcpSetNotifyWritable(sock,false); // sanity check... shouldn't happen
+		} else {
+			_phy.tcpSetNotifyWritable(sock,false);
+		}
 	}
 
 	inline int nodeVirtualNetworkConfigFunction(uint64_t nwid,enum ZT1_VirtualNetworkConfigOperation op,const ZT1_VirtualNetworkConfig *nwc)
@@ -939,24 +969,26 @@ public:
 		int result = -1;
 		switch(addr->ss_family) {
 			case AF_INET:
-				//if (_v4UdpSocket)
-					//result = (_phy.udpSend(_v4UdpSocket,(const struct sockaddr *)addr,data,len) ? 0 : -1);
+#ifdef ZT_BREAK_UDP
+				if (!OSUtils::fileExists("/tmp/ZT_BREAK_UDP")) {
+#endif
+				if (_v4UdpSocket)
+					result = ((_phy.udpSend(_v4UdpSocket,(const struct sockaddr *)addr,data,len) != 0) ? 0 : -1);
+#ifdef ZT_BREAK_UDP
+				}
+#endif
 
-				if (reinterpret_cast<const InetAddress *>(addr)->ipScope() == InetAddress::IP_SCOPE_GLOBAL) {
+#ifdef ZT1_TCP_FALLBACK_RELAY
+				// TCP fallback tunnel support
+				if ((len >= 16)&&(reinterpret_cast<const InetAddress *>(addr)->ipScope() == InetAddress::IP_SCOPE_GLOBAL)) {
 					uint64_t now = OSUtils::now();
 
-					/* Engage TCP fallback if we've sent something more than PING_CHECK_INTERVAL ago,
-					 * less than twice the fallback period ago, and haven't heard anything in the fallback
-					 * timeout period. In that case our packets to the global IP scope are probably
-					 * being blocked, so start trying to tunnel them out.
-					 *
-					 * Note that we *always* send them as plain UDP above. This way if we ever get unblocked
-					 * or if our connectivity changes for the better, we will instantly "fail forward" back
-					 * to plain vanilla UDP and abandon the tunnel.
-					 *
-					 * TCP fallback is currently only supported for tunneling to IPv4 addresses. */
-					if (((now - _lastSendToGlobal) < ZT1_TCP_FALLBACK_AFTER)&&((now - _lastSendToGlobal) > ZT_PING_CHECK_INVERVAL)&&((now - _lastDirectReceiveFromGlobal) > ZT1_TCP_FALLBACK_AFTER)) {
+					// Engage TCP tunnel fallback if we haven't received anything valid from a global
+					// IP address in ZT1_TCP_FALLBACK_AFTER milliseconds. If we do start getting
+					// valid direct traffic we'll stop using it and close the socket after a while.
+					if (((now - _lastDirectReceiveFromGlobal) > ZT1_TCP_FALLBACK_AFTER)&&((now - _lastRestart) > ZT1_TCP_FALLBACK_AFTER)) {
 						if (_tcpFallbackTunnel) {
+							Mutex::Lock _l(_tcpFallbackTunnel->writeBuf_m);
 							if (!_tcpFallbackTunnel->writeBuf.length())
 								_phy.tcpSetNotifyWritable(_tcpFallbackTunnel->sock,true);
 							unsigned long mlen = len + 7;
@@ -969,7 +1001,8 @@ public:
 							_tcpFallbackTunnel->writeBuf.append(reinterpret_cast<const char *>(reinterpret_cast<const void *>(&(reinterpret_cast<const struct sockaddr_in *>(addr)->sin_addr.s_addr))),4);
 							_tcpFallbackTunnel->writeBuf.append(reinterpret_cast<const char *>(reinterpret_cast<const void *>(&(reinterpret_cast<const struct sockaddr_in *>(addr)->sin_port))),2);
 							_tcpFallbackTunnel->writeBuf.append((const char *)data,len);
-						} else {
+							result = 0;
+						} else if (((now - _lastSendToGlobal) < ZT1_TCP_FALLBACK_AFTER)&&((now - _lastSendToGlobal) > (ZT_PING_CHECK_INVERVAL / 2))) {
 							std::vector<InetAddress> tunnelIps(_tcpFallbackResolver.get());
 							if (tunnelIps.empty()) {
 								if (!_tcpFallbackResolver.running())
@@ -985,11 +1018,18 @@ public:
 
 					_lastSendToGlobal = now;
 				}
+#endif // ZT1_TCP_FALLBACK_RELAY
 
 				break;
 			case AF_INET6:
+#ifdef ZT_BREAK_UDP
+				if (!OSUtils::fileExists("/tmp/ZT_BREAK_UDP")) {
+#endif
 				if (_v6UdpSocket)
-					result = (_phy.udpSend(_v6UdpSocket,(const struct sockaddr *)addr,data,len) ? 0 : -1);
+					result = ((_phy.udpSend(_v6UdpSocket,(const struct sockaddr *)addr,data,len) != 0) ? 0 : -1);
+#ifdef ZT_BREAK_UDP
+				}
+#endif
 				break;
 			default:
 				return -1;
@@ -1039,16 +1079,19 @@ public:
 		}
 
 		Utils::snprintf(tmpn,sizeof(tmpn),"HTTP/1.1 %.3u %s\r\nCache-Control: no-cache\r\nPragma: no-cache\r\n",scode,scodestr);
-		tc->writeBuf.assign(tmpn);
-		tc->writeBuf.append("Content-Type: ");
-		tc->writeBuf.append(contentType);
-		Utils::snprintf(tmpn,sizeof(tmpn),"\r\nContent-Length: %lu\r\n",(unsigned long)data.length());
-		tc->writeBuf.append(tmpn);
-		if (!tc->shouldKeepAlive)
-			tc->writeBuf.append("Connection: close\r\n");
-		tc->writeBuf.append("\r\n");
-		if (tc->parser.method != HTTP_HEAD)
-			tc->writeBuf.append(data);
+		{
+			Mutex::Lock _l(tc->writeBuf_m);
+			tc->writeBuf.assign(tmpn);
+			tc->writeBuf.append("Content-Type: ");
+			tc->writeBuf.append(contentType);
+			Utils::snprintf(tmpn,sizeof(tmpn),"\r\nContent-Length: %lu\r\n",(unsigned long)data.length());
+			tc->writeBuf.append(tmpn);
+			if (!tc->shouldKeepAlive)
+				tc->writeBuf.append("Connection: close\r\n");
+			tc->writeBuf.append("\r\n");
+			if (tc->parser.method != HTTP_HEAD)
+				tc->writeBuf.append(data);
+		}
 
 		_phy.tcpSetNotifyWritable(tc->sock,true);
 	}
@@ -1092,6 +1135,7 @@ private:
 	ControlPlane *_controlPlane;
 	uint64_t _lastDirectReceiveFromGlobal;
 	uint64_t _lastSendToGlobal;
+	uint64_t _lastRestart;
 	volatile uint64_t _nextBackgroundTaskDeadline;
 
 	std::map< uint64_t,EthernetTap * > _taps;

service/OneService.hpp

@@ -126,6 +126,11 @@ public:
 	 */
 	virtual std::string portDeviceName(uint64_t nwid) const = 0;
 
+	/**
+	 * @return True if TCP fallback is currently active
+	 */
+	virtual bool tcpFallbackActive() const = 0;
+
 	/**
 	 * Terminate background service (can be called from other threads)
 	 */

service/README.md

@@ -26,6 +26,7 @@ A *jsonp* URL argument may be supplied to request JSONP encapsulation. A JSONP r
 <tr><td>address</td><td>string</td><td>10-digit hexadecimal ZeroTier address of this node</td><td>no</td></tr>
 <tr><td>publicIdentity</td><td>string</td><td>Full public ZeroTier identity of this node</td><td>no</td></tr>
 <tr><td>online</td><td>boolean</td><td>Does this node appear to have upstream network access?</td><td>no</td></tr>
+<tr><td>tcpFallbackActive</td><td>boolean</td><td>Is TCP fallback mode active?</td><td>no</td></tr>
 <tr><td>versionMajor</td><td>integer</td><td>ZeroTier major version</td><td>no</td></tr>
 <tr><td>versionMinor</td><td>integer</td><td>ZeroTier minor version</td><td>no</td></tr>
 <tr><td>versionRev</td><td>integer</td><td>ZeroTier revision</td><td>no</td></tr>

tcp-proxy/tcp-proxy.cpp

@@ -25,6 +25,17 @@
  * LLC. Start here: http://www.zerotier.com/
  */
 
+// HACK! Will eventually use epoll() or something in Phy<> instead of select().
+// Also be sure to change ulimit -n and fs.file-max in /etc/sysctl.conf on relays.
+#if defined(__linux__) || defined(__LINUX__) || defined(__LINUX) || defined(LINUX)
+#include <linux/posix_types.h>
+#include <bits/types.h>
+#undef __FD_SETSIZE
+#define __FD_SETSIZE 1048576
+#undef FD_SETSIZE
+#define FD_SETSIZE 1048576
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -41,10 +52,7 @@
 
 #include "../osdep/Phy.hpp"
 
-#define ZT_TCP_PROXY_UDP_POOL_SIZE 1024
-#define ZT_TCP_PROXY_UDP_POOL_START_PORT 10000
 #define ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS 300
-
 #define ZT_TCP_PROXY_TCP_PORT 443
 
 using namespace ZeroTier;
@@ -90,8 +98,7 @@ struct TcpProxyService;
 struct TcpProxyService
 {
 	Phy<TcpProxyService *> *phy;
-	PhySocket *udpPool[ZT_TCP_PROXY_UDP_POOL_SIZE];
-
+	int udpPortCounter;
 	struct Client
 	{
 		char tcpReadBuf[131072];
@@ -99,99 +106,101 @@ struct TcpProxyService
 		unsigned long tcpWritePtr;
 		unsigned long tcpReadPtr;
 		PhySocket *tcp;
-		PhySocket *assignedUdp;
+		PhySocket *udp;
 		time_t lastActivity;
 		bool newVersion;
 	};
-
 	std::map< PhySocket *,Client > clients;
 
-	struct ReverseMappingKey
+	PhySocket *getUnusedUdp(void *uptr)
 	{
-		uint64_t sourceZTAddress;
-		PhySocket *sendingUdpSocket;
-		uint32_t destIp;
-		unsigned int destPort;
-
-		ReverseMappingKey() {}
-		ReverseMappingKey(uint64_t zt,PhySocket *s,uint32_t ip,unsigned int port) : sourceZTAddress(zt),sendingUdpSocket(s),destIp(ip),destPort(port) {}
-		inline bool operator<(const ReverseMappingKey &k) const throw() { return (memcmp((const void *)this,(const void *)&k,sizeof(ReverseMappingKey)) < 0); }
-		inline bool operator==(const ReverseMappingKey &k) const throw() { return (memcmp((const void *)this,(const void *)&k,sizeof(ReverseMappingKey)) == 0); }
-	};
-
-	std::map< ReverseMappingKey,Client * > reverseMappings;
+		for(int i=0;i<65535;++i) {
+			++udpPortCounter;
+			if (udpPortCounter > 0xfffe)
+				udpPortCounter = 1024;
+			struct sockaddr_in laddr;
+			memset(&laddr,0,sizeof(struct sockaddr_in));
+			laddr.sin_family = AF_INET;
+			laddr.sin_port = htons((uint16_t)udpPortCounter);
+			PhySocket *udp = phy->udpBind(reinterpret_cast<struct sockaddr *>(&laddr),uptr);
+			if (udp)
+				return udp;
+		}
+		return (PhySocket *)0;
+	}
 
 	void phyOnDatagram(PhySocket *sock,void **uptr,const struct sockaddr *from,void *data,unsigned long len)
 	{
-		if ((from->sa_family == AF_INET)&&(len > 16)&&(len < 2048)) {
-			const uint64_t destZt = (
-				(((uint64_t)(((const unsigned char *)data)[8])) << 32) |
-				(((uint64_t)(((const unsigned char *)data)[9])) << 24) |
-				(((uint64_t)(((const unsigned char *)data)[10])) << 16) |
-				(((uint64_t)(((const unsigned char *)data)[11])) << 8) |
-				((uint64_t)(((const unsigned char *)data)[12])) );
-			const uint32_t fromIp = ((const struct sockaddr_in *)from)->sin_addr.s_addr;
-			const unsigned int fromPort = ntohs(((const struct sockaddr_in *)from)->sin_port);
-
-			std::map< ReverseMappingKey,Client * >::iterator rm(reverseMappings.find(ReverseMappingKey(destZt,sock,fromIp,fromPort)));
-			if (rm != reverseMappings.end()) {
-				Client &c = *(rm->second);
-
-				unsigned long mlen = len;
-				if (c.newVersion)
-					mlen += 7; // new clients get IP info
-
-				if ((c.tcpWritePtr + 5 + mlen) <= sizeof(c.tcpWriteBuf)) {
-					if (!c.tcpWritePtr)
-						phy->tcpSetNotifyWritable(c.tcp,true);
-
-					c.tcpWriteBuf[c.tcpWritePtr++] = 0x17; // look like TLS data
-					c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
-					c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
-
-					c.tcpWriteBuf[c.tcpWritePtr++] = (char)((mlen >> 8) & 0xff);
-					c.tcpWriteBuf[c.tcpWritePtr++] = (char)(mlen & 0xff);
-
-					if (c.newVersion) {
-						c.tcpWriteBuf[c.tcpWritePtr++] = (char)4; // IPv4
-						*((uint32_t *)(c.tcpWriteBuf + c.tcpWritePtr)) = fromIp;
-						c.tcpWritePtr += 4;
-						c.tcpWriteBuf[c.tcpWritePtr++] = (char)((fromPort >> 8) & 0xff);
-						c.tcpWriteBuf[c.tcpWritePtr++] = (char)(fromPort & 0xff);
-					}
+		if (!*uptr)
+			return;
+		if ((from->sa_family == AF_INET)&&(len >= 16)&&(len < 2048)) {
+			Client &c = *((Client *)*uptr);
+			c.lastActivity = time((time_t *)0);
+
+			unsigned long mlen = len;
+			if (c.newVersion)
+				mlen += 7; // new clients get IP info
+
+			if ((c.tcpWritePtr + 5 + mlen) <= sizeof(c.tcpWriteBuf)) {
+				if (!c.tcpWritePtr)
+					phy->tcpSetNotifyWritable(c.tcp,true);
+
+				c.tcpWriteBuf[c.tcpWritePtr++] = 0x17; // look like TLS data
+				c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
+				c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
+
+				c.tcpWriteBuf[c.tcpWritePtr++] = (char)((mlen >> 8) & 0xff);
+				c.tcpWriteBuf[c.tcpWritePtr++] = (char)(mlen & 0xff);
 
-					for(unsigned long i=0;i<len;++i)
-						c.tcpWriteBuf[c.tcpWritePtr++] = ((const char *)data)[i];
+				if (c.newVersion) {
+					c.tcpWriteBuf[c.tcpWritePtr++] = (char)4; // IPv4
+					*((uint32_t *)(c.tcpWriteBuf + c.tcpWritePtr)) = ((const struct sockaddr_in *)from)->sin_addr.s_addr;
+					c.tcpWritePtr += 4;
+					*((uint16_t *)(c.tcpWriteBuf + c.tcpWritePtr)) = ((const struct sockaddr_in *)from)->sin_port;
+					c.tcpWritePtr += 2;
 				}
+
+				for(unsigned long i=0;i<len;++i)
+					c.tcpWriteBuf[c.tcpWritePtr++] = ((const char *)data)[i];
 			}
+
+			//printf("<< UDP %s:%d -> %.16llx\n",inet_ntoa(reinterpret_cast<const struct sockaddr_in *>(from)->sin_addr),(int)ntohs(reinterpret_cast<const struct sockaddr_in *>(from)->sin_port),(unsigned long long)&c);
 		}
 	}
 
 	void phyOnTcpConnect(PhySocket *sock,void **uptr,bool success)
 	{
-		// unused, we don't initiate
+		// unused, we don't initiate outbound connections
 	}
 
 	void phyOnTcpAccept(PhySocket *sockL,PhySocket *sockN,void **uptrL,void **uptrN,const struct sockaddr *from)
 	{
 		Client &c = clients[sockN];
+		PhySocket *udp = getUnusedUdp((void *)&c);
+		if (!udp) {
+			phy->close(sockN);
+			clients.erase(sockN);
+			//printf("** TCP rejected, no more UDP ports to assign\n");
+			return;
+		}
 		c.tcpWritePtr = 0;
 		c.tcpReadPtr = 0;
 		c.tcp = sockN;
-		c.assignedUdp = udpPool[rand() % ZT_TCP_PROXY_UDP_POOL_SIZE];
+		c.udp = udp;
 		c.lastActivity = time((time_t *)0);
 		c.newVersion = false;
 		*uptrN = (void *)&c;
+		//printf("<< TCP from %s -> %.16llx\n",inet_ntoa(reinterpret_cast<const struct sockaddr_in *>(from)->sin_addr),(unsigned long long)&c);
 	}
 
 	void phyOnTcpClose(PhySocket *sock,void **uptr)
 	{
-		for(std::map< ReverseMappingKey,Client * >::iterator rm(reverseMappings.begin());rm!=reverseMappings.end();) {
-			if (rm->second == (Client *)*uptr)
-				reverseMappings.erase(rm++);
-			else ++rm;
-		}
+		if (!*uptr)
+			return;
+		Client &c = *((Client *)*uptr);
+		phy->close(c.udp);
 		clients.erase(sock);
+		//printf("** TCP %.16llx closed\n",(unsigned long long)*uptr);
 	}
 
 	void phyOnTcpData(PhySocket *sock,void **uptr,void *data,unsigned long len)
@@ -212,6 +221,7 @@ struct TcpProxyService
 					if (mlen == 4) {
 						// Right now just sending this means the client is 'new enough' for the IP header
 						c.newVersion = true;
+						//printf("<< TCP %.16llx HELLO\n",(unsigned long long)*uptr);
 					} else if (mlen >= 7) {
 						char *payload = c.tcpReadBuf + 5;
 						unsigned long payloadLen = mlen;
@@ -241,22 +251,8 @@ struct TcpProxyService
 
 						// Note: we do not relay to privileged ports... just an abuse prevention rule.
 						if ((ntohs(dest.sin_port) > 1024)&&(payloadLen >= 16)) {
-							if ((payloadLen >= 28)&&(payload[13] != (char)0xff)) {
-								// Learn reverse mappings -- we will route replies to these packets
-								// back to their sending TCP socket. They're on a first come first
-								// served basis.
-								const uint64_t sourceZt = (
-									(((uint64_t)(((const unsigned char *)payload)[13])) << 32) |
-									(((uint64_t)(((const unsigned char *)payload)[14])) << 24) |
-									(((uint64_t)(((const unsigned char *)payload)[15])) << 16) |
-									(((uint64_t)(((const unsigned char *)payload)[16])) << 8) |
-									((uint64_t)(((const unsigned char *)payload)[17])) );
-								ReverseMappingKey k(sourceZt,c.assignedUdp,dest.sin_addr.s_addr,ntohl(dest.sin_port));
-								if (reverseMappings.count(k) == 0)
-									reverseMappings[k] = &c;
-							}
-
-							phy->udpSend(c.assignedUdp,(const struct sockaddr *)&dest,payload,payloadLen);
+							phy->udpSend(c.udp,(const struct sockaddr *)&dest,payload,payloadLen);
+							//printf(">> TCP %.16llx to %s:%d\n",(unsigned long long)*uptr,inet_ntoa(dest.sin_addr),(int)ntohs(dest.sin_port));
 						}
 					}
 
@@ -284,11 +280,13 @@ struct TcpProxyService
 		std::vector<PhySocket *> toClose;
 		time_t now = time((time_t *)0);
 		for(std::map< PhySocket *,Client >::iterator c(clients.begin());c!=clients.end();++c) {
-			if ((now - c->second.lastActivity) >= ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS)
+			if ((now - c->second.lastActivity) >= ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS) {
 				toClose.push_back(c->first);
+				toClose.push_back(c->second.udp);
+			}
 		}
 		for(std::vector<PhySocket *>::iterator s(toClose.begin());s!=toClose.end();++s)
-			phy->close(*s); // will call phyOnTcpClose() which does cleanup
+			phy->close(*s);
 	}
 };
 
@@ -299,25 +297,9 @@ int main(int argc,char **argv)
 	srand(time((time_t *)0));
 
 	TcpProxyService svc;
-	Phy<TcpProxyService *> phy(&svc,true);
+	Phy<TcpProxyService *> phy(&svc,false);
 	svc.phy = &phy;
-
-	{
-		int poolSize = 0;
-		for(unsigned int p=ZT_TCP_PROXY_UDP_POOL_START_PORT;((poolSize<ZT_TCP_PROXY_UDP_POOL_SIZE)&&(p<=65535));++p) {
-			struct sockaddr_in laddr;
-			memset(&laddr,0,sizeof(laddr));
-			laddr.sin_family = AF_INET;
-			laddr.sin_port = htons((uint16_t)p);
-			PhySocket *s = phy.udpBind((const struct sockaddr *)&laddr);
-			if (s)
-				svc.udpPool[poolSize++] = s;
-		}
-		if (poolSize < ZT_TCP_PROXY_UDP_POOL_SIZE) {
-			fprintf(stderr,"%s: fatal error: cannot bind %d UDP ports\n",argv[0],ZT_TCP_PROXY_UDP_POOL_SIZE);
-			return 1;
-		}
-	}
+	svc.udpPortCounter = 1023;
 
 	{
 		struct sockaddr_in laddr;