Merge pull request #1808 from zerotier/dev-tcp-proxy

Dig tcp-proxy out of the git history

.gitignore

@@ -136,4 +136,5 @@ zeroidc/target/
 __pycache__
 *.pyc
 *_source.tar.bz2
-snap/.snapcraft
+snap/.snapcraft
+tcp-proxy/tcp-proxy

tcp-proxy/Makefile

@@ -0,0 +1,7 @@
+CXX=$(shell which clang++ g++ c++ 2>/dev/null | head -n 1)
+
+all:
+	$(CXX) -O3 -fno-rtti -o tcp-proxy tcp-proxy.cpp
+
+clean:
+	rm -f *.o tcp-proxy *.dSYM

tcp-proxy/README.md

@@ -0,0 +1,35 @@
+TCP Proxy Server
+======
+
+This is the TCP proxy server we run for TCP tunneling from peers behind difficult NATs. Regular users won't have much use for this.
+
+## How to run your own
+Currently you must build it and distribute it to your server manually. 
+
+To reduce latency, the tcp-relay should be as close as possible to the nodes it is serving. A datacenter in the same city or the LAN would be ideal.
+
+
+### Build
+`cd tcp-relay`
+`make`
+
+### Point your node at it
+ The default tcp relay is at `204.80.128.1/443` -an anycast address.
+
+#### Option 1 - local.conf configuration
+See [Service docs](https://github.com/zerotier/ZeroTierOne/blob/e0acccc3c918b59678033e585b31eb000c68fdf2/service/README.md) for more info on local.conf
+`{ "settings": { "tcpFallbackRelay": "198.51.100.123/443"  } }`
+
+
+#### Option 2 - redirect 204.80.128.1 to your own IP
+
+If you are the admin of the network that is blocking ZeroTier UDP, you can transparently redirect 204.80.128.1 to one of your IP addresses. Users won't need to edit their local client configuration.
+
+Configuring this in your Enterprise Firewall is left as an exercise to the reader.
+
+Here is an iptables example for illustrative purposes:
+
+``` shell
+-A PREROUTING -p tcp -d 204.80.128.1 --dport 443 -j DNAT --to-destination 198.51.100.123
+-A POSTROUTING -p tcp -d 198.51.100.123 --dport 443 -j SNAT --to-source 204.80.128.1
+```

tcp-proxy/tcp-proxy.cpp

@@ -0,0 +1,317 @@
+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2016  ZeroTier, Inc.  https://www.zerotier.com/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// 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>
+#include <time.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <signal.h>
+
+#include <map>
+#include <set>
+#include <string>
+#include <algorithm>
+#include <vector>
+
+#include "../osdep/Phy.hpp"
+
+#define ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS 300
+#define ZT_TCP_PROXY_TCP_PORT 443
+
+using namespace ZeroTier;
+
+/*
+ * ZeroTier TCP Proxy Server
+ *
+ * This implements a simple packet encapsulation that is designed to look like
+ * a TLS connection. It's not a TLS connection, but it sends TLS format record
+ * headers. It could be extended in the future to implement a fake TLS
+ * handshake.
+ *
+ * At the moment, each packet is just made to look like TLS application data:
+ *   <[1] TLS content type> - currently 0x17 for "application data"
+ *   <[1] TLS major version> - currently 0x03 for TLS 1.2
+ *   <[1] TLS minor version> - currently 0x03 for TLS 1.2
+ *   <[2] payload length> - 16-bit length of payload in bytes
+ *   <[...] payload> - Message payload
+ *
+ * TCP is inherently inefficient for encapsulating Ethernet, since TCP and TCP
+ * like protocols over TCP lead to double-ACKs. So this transport is only used
+ * to enable access when UDP or other datagram protocols are not available.
+ *
+ * Clients send a greeting, which is a four-byte message that contains:
+ *   <[1] ZeroTier major version>
+ *   <[1] minor version>
+ *   <[2] revision>
+ *
+ * If a client has sent a greeting, it uses the new version of this protocol
+ * in which every encapsulated ZT packet is prepended by an IP address where
+ * it should be forwarded (or where it came from for replies). This causes
+ * this proxy to act as a remote UDP socket similar to a socks proxy, which
+ * will allow us to move this function off the rootservers and onto dedicated
+ * proxy nodes.
+ *
+ * Older ZT clients that do not send this message get their packets relayed
+ * to/from 127.0.0.1:9993, which will allow them to talk to and relay via
+ * the ZT node on the same machine as the proxy. We'll only support this for
+ * as long as such nodes appear to be in the wild.
+ */
+
+struct TcpProxyService;
+struct TcpProxyService
+{
+	Phy<TcpProxyService *> *phy;
+	int udpPortCounter;
+	struct Client
+	{
+		char tcpReadBuf[131072];
+		char tcpWriteBuf[131072];
+		unsigned long tcpWritePtr;
+		unsigned long tcpReadPtr;
+		PhySocket *tcp;
+		PhySocket *udp;
+		time_t lastActivity;
+		bool newVersion;
+	};
+	std::map< PhySocket *,Client > clients;
+
+	PhySocket *getUnusedUdp(void *uptr)
+	{
+		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 *localAddr,const struct sockaddr *from,void *data,unsigned long len)
+	{
+		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->setNotifyWritable(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)) = ((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 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.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)
+	{
+		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)
+	{
+		Client &c = *((Client *)*uptr);
+		c.lastActivity = time((time_t *)0);
+
+		for(unsigned long i=0;i<len;++i) {
+			if (c.tcpReadPtr >= sizeof(c.tcpReadBuf)) {
+				phy->close(sock);
+				return;
+			}
+			c.tcpReadBuf[c.tcpReadPtr++] = ((const char *)data)[i];
+
+			if (c.tcpReadPtr >= 5) {
+				unsigned long mlen = ( ((((unsigned long)c.tcpReadBuf[3]) & 0xff) << 8) | (((unsigned long)c.tcpReadBuf[4]) & 0xff) );
+				if (c.tcpReadPtr >= (mlen + 5)) {
+					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;
+
+						struct sockaddr_in dest;
+						memset(&dest,0,sizeof(dest));
+						if (c.newVersion) {
+							if (*payload == (char)4) {
+								// New clients tell us where their packets go.
+								++payload;
+								dest.sin_family = AF_INET;
+								dest.sin_addr.s_addr = *((uint32_t *)payload);
+								payload += 4;
+								dest.sin_port = *((uint16_t *)payload); // will be in network byte order already
+								payload += 2;
+								payloadLen -= 7;
+							}
+						} else {
+							// For old clients we will just proxy everything to a local ZT instance. The
+							// fact that this will come from 127.0.0.1 will in turn prevent that instance
+							// from doing unite() with us. It'll just forward. There will not be many of
+							// these.
+							dest.sin_family = AF_INET;
+							dest.sin_addr.s_addr = htonl(0x7f000001); // 127.0.0.1
+							dest.sin_port = htons(9993);
+						}
+
+						// Note: we do not relay to privileged ports... just an abuse prevention rule.
+						if ((ntohs(dest.sin_port) > 1024)&&(payloadLen >= 16)) {
+							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));
+						}
+					}
+
+					memmove(c.tcpReadBuf,c.tcpReadBuf + (mlen + 5),c.tcpReadPtr -= (mlen + 5));
+				}
+			}
+		}
+	}
+
+	void phyOnTcpWritable(PhySocket *sock,void **uptr)
+	{
+		Client &c = *((Client *)*uptr);
+		if (c.tcpWritePtr) {
+			long n = phy->streamSend(sock,c.tcpWriteBuf,c.tcpWritePtr);
+			if (n > 0) {
+				memmove(c.tcpWriteBuf,c.tcpWriteBuf + n,c.tcpWritePtr -= (unsigned long)n);
+				if (!c.tcpWritePtr)
+					phy->setNotifyWritable(sock,false);
+			}
+		} else phy->setNotifyWritable(sock,false);
+	}
+
+	void doHousekeeping()
+	{
+		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) {
+				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);
+	}
+};
+
+int main(int argc,char **argv)
+{
+	signal(SIGPIPE,SIG_IGN);
+	signal(SIGHUP,SIG_IGN);
+	srand(time((time_t *)0));
+
+	TcpProxyService svc;
+	Phy<TcpProxyService *> phy(&svc,false,true);
+	svc.phy = &phy;
+	svc.udpPortCounter = 1023;
+
+	{
+		struct sockaddr_in laddr;
+		memset(&laddr,0,sizeof(laddr));
+		laddr.sin_family = AF_INET;
+		laddr.sin_port = htons(ZT_TCP_PROXY_TCP_PORT);
+		if (!phy.tcpListen((const struct sockaddr *)&laddr)) {
+			fprintf(stderr,"%s: fatal error: unable to bind TCP port %d\n",argv[0],ZT_TCP_PROXY_TCP_PORT);
+			return 1;
+		}
+	}
+
+	time_t lastDidHousekeeping = time((time_t *)0);
+	for(;;) {
+		phy.poll(120000);
+		time_t now = time((time_t *)0);
+		if ((now - lastDidHousekeeping) > 120) {
+			lastDidHousekeeping = now;
+			svc.doHousekeeping();
+		}
+	}
+
+	return 0;
+}