ZeroTierOne/node/EthernetTap.cpp

/*
 * ZeroTier One - Global Peer to Peer Ethernet
 * Copyright (C) 2012-2013  ZeroTier Networks LLC
 *
 * 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/>.
 *
 * --
 *
 * ZeroTier may be used and distributed under the terms of the GPLv3, which
 * are available at: http://www.gnu.org/licenses/gpl-3.0.html
 *
 * If you would like to embed ZeroTier into a commercial application or
 * redistribute it in a modified binary form, please contact ZeroTier Networks
 * LLC. Start here: http://www.zerotier.com/
 */

#include <string>
#include <map>
#include <set>
#include <algorithm>

#include "Constants.hpp"
#include "EthernetTap.hpp"
#include "Logger.hpp"
#include "RuntimeEnvironment.hpp"
#include "Utils.hpp"
#include "Mutex.hpp"
#include "Utils.hpp"

// ff:ff:ff:ff:ff:ff with no ADI
static const ZeroTier::MulticastGroup _blindWildcardMulticastGroup(ZeroTier::MAC(0xff),0);

//
// TAP implementation for *nix OSes, with some specialization for different flavors
//

#ifdef __UNIX_LIKE__ /////////////////////////////////////////////////////////

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <netinet/in.h>
#include <net/if_arp.h>
#include <arpa/inet.h>

// Command identifiers used with command finder static (on various *nixes)
#define ZT_UNIX_IP_COMMAND 1
#define ZT_UNIX_IFCONFIG_COMMAND 2
#define ZT_MAC_KEXTLOAD_COMMAND 3
#define ZT_MAC_IPCONFIG_COMMAND 4
#define ZT_MAC_KEXTUNLOAD_COMMAND 5

// Finds external commands on startup
class _CommandFinder
{
public:
	_CommandFinder()
	{
		_findCmd(ZT_UNIX_IFCONFIG_COMMAND,"ifconfig");
#ifdef __LINUX__
		_findCmd(ZT_UNIX_IP_COMMAND,"ip");
#endif
#ifdef __APPLE__
		_findCmd(ZT_MAC_KEXTLOAD_COMMAND,"kextload");
		_findCmd(ZT_MAC_IPCONFIG_COMMAND,"ipconfig");
		_findCmd(ZT_MAC_KEXTUNLOAD_COMMAND,"kextunload");
#endif
	}

	// returns NULL if command was not found
	inline const char *operator[](int id) const
		throw()
	{
		std::map<int,std::string>::const_iterator c(_paths.find(id));
		if (c == _paths.end())
			return (const char *)0;
		return c->second.c_str();
	}

private:
	inline void _findCmd(int id,const char *name)
	{
		char tmp[4096];
		ZeroTier::Utils::snprintf(tmp,sizeof(tmp),"/sbin/%s",name);
		if (ZeroTier::Utils::fileExists(tmp)) {
			_paths[id] = tmp;
			return;
		}
		ZeroTier::Utils::snprintf(tmp,sizeof(tmp),"/usr/sbin/%s",name);
		if (ZeroTier::Utils::fileExists(tmp)) {
			_paths[id] = tmp;
			return;
		}
		ZeroTier::Utils::snprintf(tmp,sizeof(tmp),"/bin/%s",name);
		if (ZeroTier::Utils::fileExists(tmp)) {
			_paths[id] = tmp;
			return;
		}
		ZeroTier::Utils::snprintf(tmp,sizeof(tmp),"/usr/bin/%s",name);
		if (ZeroTier::Utils::fileExists(tmp)) {
			_paths[id] = tmp;
			return;
		}
	}
	std::map<int,std::string> _paths;
};
static const _CommandFinder UNIX_COMMANDS;

#ifdef __LINUX__
#include <linux/if.h>
#include <linux/if_tun.h>
#include <linux/if_addr.h>
#include <linux/if_ether.h>
#endif // __LINUX__

#ifdef __APPLE__
#include <sys/uio.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <net/route.h>
#include <net/if_dl.h>
#include <ifaddrs.h>

static volatile int EthernetTap_instances = 0;
static ZeroTier::Mutex EthernetTap_instances_m;
#endif // __APPLE__

namespace ZeroTier {

// Only permit one tap to be opened concurrently across the entire process
static Mutex __tapCreateLock;

#ifdef __LINUX__
EthernetTap::EthernetTap(
	const RuntimeEnvironment *renv,
	const char *tag,
	const MAC &mac,
	unsigned int mtu,
	void (*handler)(void *,const MAC &,const MAC &,unsigned int,const Buffer<4096> &),
	void *arg)
	throw(std::runtime_error) :
	_mac(mac),
	_mtu(mtu),
	_r(renv),
	_handler(handler),
	_arg(arg),
	_fd(0)
{
	char procpath[128];
	Mutex::Lock _l(__tapCreateLock); // create only one tap at a time, globally

	if (mtu > 4096)
		throw std::runtime_error("max tap MTU is 4096");

	_fd = ::open("/dev/net/tun",O_RDWR);
	if (_fd <= 0)
		throw std::runtime_error(std::string("could not open TUN/TAP device: ") + strerror(errno));

	struct ifreq ifr;
	memset(&ifr,0,sizeof(ifr));

	{ // pick an unused device name
		int devno = 0;
		struct stat sbuf;
		do {
			Utils::snprintf(ifr.ifr_name,sizeof(ifr.ifr_name),"zt%d",devno++);
			Utils::snprintf(procpath,sizeof(procpath),"/proc/sys/net/ipv4/conf/%s",ifr.ifr_name);
		} while (stat(procpath,&sbuf) == 0);
	}

	ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
	if (ioctl(_fd,TUNSETIFF,(void *)&ifr) < 0) {
		::close(_fd);
		throw std::runtime_error("unable to configure TUN/TAP device for TAP operation");
	}

	strcpy(_dev,ifr.ifr_name);

	ioctl(_fd,TUNSETPERSIST,0); // valgrind may generate a false alarm here

	// Open an arbitrary socket to talk to netlink
	int sock = socket(AF_INET,SOCK_DGRAM,0);
	if (sock <= 0) {
		::close(_fd);
		throw std::runtime_error("unable to open netlink socket");
	}

	// Set MAC address
	ifr.ifr_ifru.ifru_hwaddr.sa_family = ARPHRD_ETHER;
	memcpy(ifr.ifr_ifru.ifru_hwaddr.sa_data,mac.data,6);
	if (ioctl(sock,SIOCSIFHWADDR,(void *)&ifr) < 0) {
		::close(_fd);
		::close(sock);
		throw std::runtime_error("unable to configure TAP hardware (MAC) address");
		return;
	}

	// Set MTU
	ifr.ifr_ifru.ifru_mtu = (int)mtu;
	if (ioctl(sock,SIOCSIFMTU,(void *)&ifr) < 0) {
		::close(_fd);
		::close(sock);
		throw std::runtime_error("unable to configure TAP MTU");
	}

	if (fcntl(_fd,F_SETFL,fcntl(_fd,F_GETFL) & ~O_NONBLOCK) == -1) {
		::close(_fd);
		throw std::runtime_error("unable to set flags on file descriptor for TAP device");
	}

	/* Bring interface up */
	if (ioctl(sock,SIOCGIFFLAGS,(void *)&ifr) < 0) {
		::close(_fd);
		::close(sock);
		throw std::runtime_error("unable to get TAP interface flags");
	}
	ifr.ifr_flags |= IFF_UP;
	if (ioctl(sock,SIOCSIFFLAGS,(void *)&ifr) < 0) {
		::close(_fd);
		::close(sock);
		throw std::runtime_error("unable to set TAP interface flags");
	}

	::close(sock);

	::pipe(_shutdownSignalPipe);

	TRACE("tap %s created",_dev);

	_thread = Thread::start(this);
}
#endif // __LINUX__

#ifdef __APPLE__
EthernetTap::EthernetTap(
	const RuntimeEnvironment *renv,
	const char *tag,
	const MAC &mac,
	unsigned int mtu,
	void (*handler)(void *,const MAC &,const MAC &,unsigned int,const Buffer<4096> &),
	void *arg)
	throw(std::runtime_error) :
	_mac(mac),
	_mtu(mtu),
	_r(renv),
	_handler(handler),
	_arg(arg),
	_dhcp(false),
	_dhcp6(false),
	_fd(0)
{
	char devpath[64],ethaddr[64],mtustr[16],tmp[4096];
	struct stat stattmp;
	Mutex::Lock _l(__tapCreateLock); // create only one tap at a time, globally

	if (mtu > 4096)
		throw std::runtime_error("max tap MTU is 4096");

	// Check for existence of ZT tap devices, try to load module if not there
	const char *kextload = UNIX_COMMANDS[ZT_MAC_KEXTLOAD_COMMAND];
	if ((stat("/dev/zt0",&stattmp))&&(kextload)) {
		strcpy(tmp,_r->homePath.c_str());
		long kextpid = (long)vfork();
		if (kextpid == 0) {
			chdir(tmp);
			execl(kextload,kextload,"-q","-repository",tmp,"tap.kext",(const char *)0);
			_exit(-1);
		} else if (kextpid > 0) {
			int exitcode = -1;
			waitpid(kextpid,&exitcode,0);
			usleep(500);
		} else throw std::runtime_error("unable to create subprocess with fork()");
	}
	if (stat("/dev/zt0",&stattmp))
		throw std::runtime_error("/dev/zt# tap devices do not exist and unable to load kernel extension");

	// Open the first available device (ones in use will fail with resource busy)
	for(int i=0;i<256;++i) {
		Utils::snprintf(devpath,sizeof(devpath),"/dev/zt%d",i);
		if (stat(devpath,&stattmp))
			throw std::runtime_error("no more TAP devices available");
		_fd = ::open(devpath,O_RDWR);
		if (_fd > 0) {
			Utils::snprintf(_dev,sizeof(_dev),"zt%d",i);
			break;
		}
	}
	if (_fd <= 0)
		throw std::runtime_error("unable to open TAP device or no more devices available");

	if (fcntl(_fd,F_SETFL,fcntl(_fd,F_GETFL) & ~O_NONBLOCK) == -1) {
		::close(_fd);
		throw std::runtime_error("unable to set flags on file descriptor for TAP device");
	}

	const char *ifconfig = UNIX_COMMANDS[ZT_UNIX_IFCONFIG_COMMAND];
	if (!ifconfig) {
		::close(_fd);
		throw std::runtime_error("unable to find 'ifconfig' command on system");
	}

	// Configure MAC address and MTU, bring interface up
	Utils::snprintf(ethaddr,sizeof(ethaddr),"%.2x:%.2x:%.2x:%.2x:%.2x:%.2x",(int)mac[0],(int)mac[1],(int)mac[2],(int)mac[3],(int)mac[4],(int)mac[5]);
	Utils::snprintf(mtustr,sizeof(mtustr),"%u",mtu);
	long cpid;
	if ((cpid = (long)vfork()) == 0) {
		execl(ifconfig,ifconfig,_dev,"lladdr",ethaddr,"mtu",mtustr,"up",(const char *)0);
		_exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		if (exitcode) {
			::close(_fd);
			throw std::runtime_error("ifconfig failure setting link-layer address and activating tap interface");
		}
	}

	whack(); // turns on IPv6 on OSX

	::pipe(_shutdownSignalPipe);

	_thread = Thread::start(this);

	EthernetTap_instances_m.lock();
	++EthernetTap_instances;
	EthernetTap_instances_m.unlock();
}
#endif // __APPLE__

EthernetTap::~EthernetTap()
{
	::write(_shutdownSignalPipe[1],"\0",1); // causes thread to exit
	Thread::join(_thread);
	::close(_fd);

#ifdef __APPLE__
	EthernetTap_instances_m.lock();
	int instances = --EthernetTap_instances;
	EthernetTap_instances_m.unlock();
	if (instances <= 0) {
		// Unload OSX kernel extension on the deletion of the last EthernetTap
		// instance.
		const char *kextunload = UNIX_COMMANDS[ZT_MAC_KEXTUNLOAD_COMMAND];
		if (kextunload) {
			char tmp[4096];
			sprintf(tmp,"%s/tap.kext",_r->homePath.c_str());
			long kextpid = (long)vfork();
			if (kextpid == 0) {
				execl(kextunload,kextunload,tmp,(const char *)0);
				_exit(-1);
			} else if (kextpid > 0) {
				int exitcode = -1;
				waitpid(kextpid,&exitcode,0);
			}
		}
	}
#endif // __APPLE__
}

#ifdef __APPLE__
void EthernetTap::whack()
{
	const char *ipconfig = UNIX_COMMANDS[ZT_MAC_IPCONFIG_COMMAND];
	if (ipconfig) {
		long cpid = (long)vfork();
		if (cpid == 0) {
			execl(ipconfig,ipconfig,"set",_dev,"AUTOMATIC-V6",(const char *)0);
			_exit(-1);
		} else {
			int exitcode = -1;
			waitpid(cpid,&exitcode,0);
		}
	}
}
#else
void EthernetTap::whack() {}
#endif // __APPLE__ / !__APPLE__

bool EthernetTap::setDhcpEnabled(bool dhcp)
{
	// TODO
	return _dhcp;
}

bool EthernetTap::setDhcp6Enabled(bool dhcp)
{
	return _dhcp6;
}

void EthernetTap::setDisplayName(const char *dn)
{
}

#ifdef __LINUX__
static bool ___removeIp(const char *_dev,const InetAddress &ip)
{
	const char *ipcmd = UNIX_COMMANDS[ZT_UNIX_IP_COMMAND];
	if (!ipcmd)
		return false;
	long cpid = (long)vfork();
	if (cpid == 0) {
		execl(ipcmd,ipcmd,"addr","del",ip.toString().c_str(),"dev",_dev,(const char *)0);
		_exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		return (exitcode == 0);
	}
}

bool EthernetTap::addIP(const InetAddress &ip)
{
	const char *ipcmd = UNIX_COMMANDS[ZT_UNIX_IP_COMMAND];
	if (!ipcmd) {
		LOG("ERROR: could not configure IP address for %s: unable to find 'ip' command on system (checked /sbin, /bin, /usr/sbin, /usr/bin)",_dev);
		return false;
	}

	Mutex::Lock _l(_ips_m);

	if (!ip)
		return false;
	if (_ips.count(ip) > 0)
		return true;

	// Remove and reconfigure if address is the same but netmask is different
	for(std::set<InetAddress>::iterator i(_ips.begin());i!=_ips.end();++i) {
		if (i->ipsEqual(ip)) {
			if (___removeIp(_dev,*i)) {
				_ips.erase(i);
				break;
			} else {
				LOG("WARNING: failed to remove old IP/netmask %s to replace with %s",i->toString().c_str(),ip.toString().c_str());
			}
		}
	}

	long cpid;
	if ((cpid = (long)vfork()) == 0) {
		execl(ipcmd,ipcmd,"addr","add",ip.toString().c_str(),"dev",_dev,(const char *)0);
		_exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		if (exitcode == 0) {
			_ips.insert(ip);
			return true;
		} else return false;
	}

	return false;
}
#endif // __LINUX__

#ifdef __APPLE__
static bool ___removeIp(const char *_dev,const InetAddress &ip)
{
	const char *ifconfig = UNIX_COMMANDS[ZT_UNIX_IFCONFIG_COMMAND];
	if (!ifconfig)
		return false;
	long cpid;
	if ((cpid = (long)vfork()) == 0) {
		execl(ifconfig,ifconfig,_dev,"inet",ip.toIpString().c_str(),"-alias",(const char *)0);
		_exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		return (exitcode == 0);
	}
	return false; // never reached, make compiler shut up about return value
}

bool EthernetTap::addIP(const InetAddress &ip)
{
	const char *ifconfig = UNIX_COMMANDS[ZT_UNIX_IFCONFIG_COMMAND];
	if (!ifconfig) {
		LOG("ERROR: could not configure IP address for %s: unable to find 'ifconfig' command on system (checked /sbin, /bin, /usr/sbin, /usr/bin)",_dev);
		return false;
	}

	Mutex::Lock _l(_ips_m);

	if (!ip)
		return false;
	if (_ips.count(ip) > 0)
		return true; // IP/netmask already assigned

	// Remove and reconfigure if address is the same but netmask is different
	for(std::set<InetAddress>::iterator i(_ips.begin());i!=_ips.end();++i) {
		if ((i->ipsEqual(ip))&&(i->netmaskBits() != ip.netmaskBits())) {
			if (___removeIp(_dev,*i)) {
				_ips.erase(i);
				break;
			} else {
				LOG("WARNING: failed to remove old IP/netmask %s to replace with %s",i->toString().c_str(),ip.toString().c_str());
			}
		}
	}

	long cpid;
	if ((cpid = (long)vfork()) == 0) {
		execl(ifconfig,ifconfig,_dev,ip.isV4() ? "inet" : "inet6",ip.toString().c_str(),"alias",(const char *)0);
		_exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		if (exitcode == 0) {
			_ips.insert(ip);
			return true;
		}
	}

	return false;
}
#endif // __APPLE__

bool EthernetTap::removeIP(const InetAddress &ip)
{
	Mutex::Lock _l(_ips_m);
	if (_ips.count(ip) > 0) {
		if (___removeIp(_dev,ip)) {
			_ips.erase(ip);
			return true;
		}
	}
	return false;
}

std::set<InetAddress> EthernetTap::allIps() const
{
	// TODO
	return ips();
}

void EthernetTap::put(const MAC &from,const MAC &to,unsigned int etherType,const void *data,unsigned int len)
{
	char putBuf[4096 + 14];
	if ((_fd > 0)&&(len <= _mtu)) {
		for(int i=0;i<6;++i)
			putBuf[i] = to.data[i];
		for(int i=0;i<6;++i)
			putBuf[i+6] = from.data[i];
		*((uint16_t *)(putBuf + 12)) = htons((uint16_t)etherType);
		memcpy(putBuf + 14,data,len);
		len += 14;

		int n = ::write(_fd,putBuf,len);
		if (n <= 0) {
			LOG("error writing packet to Ethernet tap device: %s",strerror(errno));
		} else if (n != (int)len) {
			// Saw this gremlin once, so log it if we see it again... OSX tap
			// or something seems to have goofy issues with certain MTUs.
			LOG("ERROR: write underrun: %s tap write() wrote %d of %u bytes of frame",_dev,n,len);
		}
	}
}

std::string EthernetTap::deviceName() const
{
	return std::string(_dev);
}

#ifdef __LINUX__
bool EthernetTap::updateMulticastGroups(std::set<MulticastGroup> &groups)
{
	char *ptr,*ptr2;
	unsigned char mac[6];
	std::set<MulticastGroup> newGroups;

	int fd = ::open("/proc/net/dev_mcast",O_RDONLY);
	if (fd > 0) {
		char buf[131072];
		int n = (int)::read(fd,buf,sizeof(buf));
		if ((n > 0)&&(n < (int)sizeof(buf))) {
			buf[n] = (char)0;
			for(char *l=strtok_r(buf,"\r\n",&ptr);(l);l=strtok_r((char *)0,"\r\n",&ptr)) {
				int fno = 0;
				char *devname = (char *)0;
				char *mcastmac = (char *)0;
				for(char *f=strtok_r(l," \t",&ptr2);(f);f=strtok_r((char *)0," \t",&ptr2)) {
					if (fno == 1)
						devname = f;
					else if (fno == 4)
						mcastmac = f;
					++fno;
				}
				if ((devname)&&(!strcmp(devname,_dev))&&(mcastmac)&&(Utils::unhex(mcastmac,mac,6) == 6))
					newGroups.insert(MulticastGroup(MAC(mac),0));
			}
		}
		::close(fd);
	}

	{
		Mutex::Lock _l(_ips_m);
		for(std::set<InetAddress>::const_iterator i(_ips.begin());i!=_ips.end();++i)
			newGroups.insert(MulticastGroup::deriveMulticastGroupForAddressResolution(*i));
	}

	bool changed = false;

	newGroups.insert(_blindWildcardMulticastGroup); // always join this

	for(std::set<MulticastGroup>::iterator mg(newGroups.begin());mg!=newGroups.end();++mg) {
		if (!groups.count(*mg)) {
			groups.insert(*mg);
			changed = true;
		}
	}
	for(std::set<MulticastGroup>::iterator mg(groups.begin());mg!=groups.end();) {
		if (!newGroups.count(*mg)) {
			groups.erase(mg++);
			changed = true;
		} else ++mg;
	}

	return changed;
}
#endif // __LINUX__

#ifdef __APPLE__
bool EthernetTap::updateMulticastGroups(std::set<MulticastGroup> &groups)
{
	std::set<MulticastGroup> newGroups;
	struct ifmaddrs *ifmap = (struct ifmaddrs *)0;
	if (!getifmaddrs(&ifmap)) {
		struct ifmaddrs *p = ifmap;
		while (p) {
			if (p->ifma_addr->sa_family == AF_LINK) {
				struct sockaddr_dl *in = (struct sockaddr_dl *)p->ifma_name;
				struct sockaddr_dl *la = (struct sockaddr_dl *)p->ifma_addr;
				if ((la->sdl_alen == 6)&&(in->sdl_nlen <= sizeof(_dev))&&(!memcmp(_dev,in->sdl_data,in->sdl_nlen)))
					newGroups.insert(MulticastGroup(MAC(la->sdl_data + la->sdl_nlen),0));
			}
			p = p->ifma_next;
		}
		freeifmaddrs(ifmap);
	}

	{
		Mutex::Lock _l(_ips_m);
		for(std::set<InetAddress>::const_iterator i(_ips.begin());i!=_ips.end();++i)
			newGroups.insert(MulticastGroup::deriveMulticastGroupForAddressResolution(*i));
	}

	bool changed = false;

	newGroups.insert(_blindWildcardMulticastGroup); // always join this

	for(std::set<MulticastGroup>::iterator mg(newGroups.begin());mg!=newGroups.end();++mg) {
		if (!groups.count(*mg)) {
			groups.insert(*mg);
			changed = true;
		}
	}
	for(std::set<MulticastGroup>::iterator mg(groups.begin());mg!=groups.end();) {
		if (!newGroups.count(*mg)) {
			groups.erase(mg++);
			changed = true;
		} else ++mg;
	}

	return changed;
}
#endif // __APPLE__

void EthernetTap::threadMain()
	throw()
{
	fd_set readfds,nullfds;
	MAC to,from;
	int n,nfds,r;
	char getBuf[8194];
	Buffer<4096> data;

	// Wait for a moment after startup -- wait for Network to finish
	// constructing itself.
	Thread::sleep(500);

	FD_ZERO(&readfds);
	FD_ZERO(&nullfds);
	nfds = (int)std::max(_shutdownSignalPipe[0],_fd) + 1;

	r = 0;
	for(;;) {
		FD_SET(_shutdownSignalPipe[0],&readfds);
		FD_SET(_fd,&readfds);
		select(nfds,&readfds,&nullfds,&nullfds,(struct timeval *)0);

		if (FD_ISSET(_shutdownSignalPipe[0],&readfds)) // writes to shutdown pipe terminate thread
			break;

		if (FD_ISSET(_fd,&readfds)) {
			n = (int)::read(_fd,getBuf + r,sizeof(getBuf) - r);
			if (n < 0) {
				if ((errno != EINTR)&&(errno != ETIMEDOUT)) {
					TRACE("unexpected error reading from tap: %s",strerror(errno));
					break;
				}
			} else {
				// Some tap drivers like to send the ethernet frame and the
				// payload in two chunks, so handle that by accumulating
				// data until we have at least a frame.
				r += n;
				if (r > 14) {
					if (r > ((int)_mtu + 14)) // sanity check for weird TAP behavior on some platforms
						r = _mtu + 14;
					for(int i=0;i<6;++i)
						to.data[i] = (unsigned char)getBuf[i];
					for(int i=0;i<6;++i)
						from.data[i] = (unsigned char)getBuf[i + 6];
					unsigned int etherType = ntohs(((const uint16_t *)getBuf)[6]);
					if (etherType != 0x8100) { // VLAN tagged frames are not supported!
						data.copyFrom(getBuf + 14,(unsigned int)r - 14);
						_handler(_arg,from,to,etherType,data);
					}
					r = 0;
				}
			}
		}
	}
}

} // namespace ZeroTier

#endif // __UNIX_LIKE__ //////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////////

#ifdef __WINDOWS__ ///////////////////////////////////////////////////////////

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <WinSock2.h>
#include <Windows.h>
#include <iphlpapi.h>
#include <ws2ipdef.h>
#include <WS2tcpip.h>
#include <tchar.h>
#include <winreg.h>
#include <wchar.h>
#include <nldef.h>
#include <netioapi.h>

#include "..\vsprojects\TapDriver\tap-windows.h"

namespace ZeroTier {

// Helper function to get an adapter's LUID and index from its GUID. The LUID is
// constant but the index can change, so go ahead and just look them both up by
// the GUID which is constant. (The GUID is the instance ID in the registry.)
static inline std::pair<NET_LUID,NET_IFINDEX> _findAdapterByGuid(const GUID &guid)
	throw(std::runtime_error)
{
	MIB_IF_TABLE2 *ift = (MIB_IF_TABLE2 *)0;

	if (GetIfTable2Ex(MibIfTableRaw,&ift) != NO_ERROR)
		throw std::runtime_error("GetIfTable2Ex() failed");

	for(ULONG i=0;i<ift->NumEntries;++i) {
		if (ift->Table[i].InterfaceGuid == guid) {
			std::pair<NET_LUID,NET_IFINDEX> tmp(ift->Table[i].InterfaceLuid,ift->Table[i].InterfaceIndex);
			FreeMibTable(ift);
			return tmp;
		}
	}

	FreeMibTable(&ift);

	throw std::runtime_error("interface not found");
}

static Mutex _systemTapInitLock;

EthernetTap::EthernetTap(
	const RuntimeEnvironment *renv,
	const char *tag,
	const MAC &mac,
	unsigned int mtu,
	void (*handler)(void *,const MAC &,const MAC &,unsigned int,const Buffer<4096> &),
	void *arg)
	throw(std::runtime_error) :
	_mac(mac),
	_mtu(mtu),
	_r(renv),
	_handler(handler),
	_arg(arg),
	_dhcp(false),
	_dhcp6(false),
	_tap(INVALID_HANDLE_VALUE),
	_injectSemaphore(INVALID_HANDLE_VALUE),
	_run(true)
{
	char subkeyName[4096];
	char subkeyClass[4096];
	char data[4096];

	if (mtu > ZT_IF_MTU)
		throw std::runtime_error("MTU too large for Windows tap");

#ifdef _WIN64
	const char *devcon = "\\devcon64.exe";
#else
	BOOL f64 = FALSE;
	const char *devcon = ((IsWow64Process(GetCurrentProcess(),&f64) == TRUE) ? "\\devcon64.exe" : "\\devcon32.exe");
#endif

	Mutex::Lock _l(_systemTapInitLock); // only init one tap at a time, process-wide

	HKEY nwAdapters;
	if (RegOpenKeyExA(HKEY_LOCAL_MACHINE,"SYSTEM\\CurrentControlSet\\Control\\Class\\{4D36E972-E325-11CE-BFC1-08002BE10318}",0,KEY_READ|KEY_WRITE,&nwAdapters) != ERROR_SUCCESS)
		throw std::runtime_error("unable to open registry key for network adapter enumeration");

	std::set<std::string> existingDeviceInstances;
	std::string mySubkeyName;

	// Enumerate tap instances and look for one tagged with this tag
	for(DWORD subkeyIndex=0;subkeyIndex!=-1;) {
		DWORD type;
		DWORD dataLen;
		DWORD subkeyNameLen = sizeof(subkeyName);
		DWORD subkeyClassLen = sizeof(subkeyClass);
		FILETIME lastWriteTime;
		switch (RegEnumKeyExA(nwAdapters,subkeyIndex++,subkeyName,&subkeyNameLen,(DWORD *)0,subkeyClass,&subkeyClassLen,&lastWriteTime)) {
			case ERROR_NO_MORE_ITEMS: subkeyIndex = -1; break;
			case ERROR_SUCCESS:
				type = 0;
				dataLen = sizeof(data);
				if (RegGetValueA(nwAdapters,subkeyName,"ComponentId",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS) {
					data[dataLen] = '\0';
					if (!strnicmp(data,"zttap",5)) {
						std::string instanceId;
						type = 0;
						dataLen = sizeof(data);
						if (RegGetValueA(nwAdapters,subkeyName,"NetCfgInstanceId",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS) {
							instanceId.assign(data,dataLen);
							existingDeviceInstances.insert(instanceId);
						}

						std::string instanceIdPath;
						type = 0;
						dataLen = sizeof(data);
						if (RegGetValueA(nwAdapters,subkeyName,"DeviceInstanceID",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS)
							instanceIdPath.assign(data,dataLen);

						if ((_myDeviceInstanceId.length() == 0)&&(instanceId.length() != 0)&&(instanceIdPath.length() != 0)) {
							type = 0;
							dataLen = sizeof(data);
							if (RegGetValueA(nwAdapters,subkeyName,"_ZeroTierTapIdentifier",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS) {
								data[dataLen] = '\0';
								if (!strcmp(data,tag)) {
									_myDeviceInstanceId = instanceId;
									_myDeviceInstanceIdPath = instanceIdPath;
									mySubkeyName = subkeyName;
									subkeyIndex = -1; // break outer loop
								}
							}
						}
					}
				}
				break;
		}
	}

	// If there is no device, try to create one
	if (_myDeviceInstanceId.length() == 0) {
		// Execute devcon to install an instance of the Microsoft Loopback Adapter
		STARTUPINFOA startupInfo;
		startupInfo.cb = sizeof(startupInfo);
		PROCESS_INFORMATION processInfo;
		memset(&startupInfo,0,sizeof(STARTUPINFOA));
		memset(&processInfo,0,sizeof(PROCESS_INFORMATION));
		if (!CreateProcessA(NULL,(LPSTR)(std::string("\"") + _r->homePath + devcon + "\" install \"" + _r->homePath + "\\ztTap100.inf\" ztTap100").c_str(),NULL,NULL,FALSE,0,NULL,NULL,&startupInfo,&processInfo)) {
			RegCloseKey(nwAdapters);
			throw std::runtime_error(std::string("unable to find or execute devcon at ")+devcon);
		}
		WaitForSingleObject(processInfo.hProcess,INFINITE);
		CloseHandle(processInfo.hProcess);
		CloseHandle(processInfo.hThread);
 
		// Scan for the new instance by simply looking for taps that weren't
		// there originally.
		for(DWORD subkeyIndex=0;subkeyIndex!=-1;) {
			DWORD type;
			DWORD dataLen;
			DWORD subkeyNameLen = sizeof(subkeyName);
			DWORD subkeyClassLen = sizeof(subkeyClass);
			FILETIME lastWriteTime;
			switch (RegEnumKeyExA(nwAdapters,subkeyIndex++,subkeyName,&subkeyNameLen,(DWORD *)0,subkeyClass,&subkeyClassLen,&lastWriteTime)) {
				case ERROR_NO_MORE_ITEMS: subkeyIndex = -1; break;
				case ERROR_SUCCESS:
					type = 0;
					dataLen = sizeof(data);
					if (RegGetValueA(nwAdapters,subkeyName,"ComponentId",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS) {
						data[dataLen] = '\0';
						if (!strnicmp(data,"zttap",5)) {
							type = 0;
							dataLen = sizeof(data);
							if (RegGetValueA(nwAdapters,subkeyName,"NetCfgInstanceId",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS) {
								if (existingDeviceInstances.count(std::string(data,dataLen)) == 0) {
									RegSetKeyValueA(nwAdapters,subkeyName,"_ZeroTierTapIdentifier",REG_SZ,tag,(DWORD)(strlen(tag)+1));
									_myDeviceInstanceId.assign(data,dataLen);
									type = 0;
									dataLen = sizeof(data);
									if (RegGetValueA(nwAdapters,subkeyName,"DeviceInstanceID",RRF_RT_ANY,&type,(PVOID)data,&dataLen) == ERROR_SUCCESS)
										_myDeviceInstanceIdPath.assign(data,dataLen);
									mySubkeyName = subkeyName;
									subkeyIndex = -1; // break outer loop
								}
							}
						}
					}
					break;
			}
		}
	}

	// If we have a device, configure it
	if (_myDeviceInstanceId.length() > 0) {
		char tmps[4096];
		unsigned int tmpsl = Utils::snprintf(tmps,sizeof(tmps),"%.2X-%.2X-%.2X-%.2X-%.2X-%.2X",(unsigned int)mac.data[0],(unsigned int)mac.data[1],(unsigned int)mac.data[2],(unsigned int)mac.data[3],(unsigned int)mac.data[4],(unsigned int)mac.data[5]) + 1;
		RegSetKeyValueA(nwAdapters,mySubkeyName.c_str(),"NetworkAddress",REG_SZ,tmps,tmpsl);
		RegSetKeyValueA(nwAdapters,mySubkeyName.c_str(),"MAC",REG_SZ,tmps,tmpsl);
		DWORD tmp = mtu;
		RegSetKeyValueA(nwAdapters,mySubkeyName.c_str(),"MTU",REG_DWORD,(LPCVOID)&tmp,sizeof(tmp));
		tmp = 0;
		RegSetKeyValueA(nwAdapters,mySubkeyName.c_str(),"EnableDHCP",REG_DWORD,(LPCVOID)&tmp,sizeof(tmp));
	}

	// Done with registry
	RegCloseKey(nwAdapters);	

	// If we didn't get a device, we can't start
	if (_myDeviceInstanceId.length() == 0)
		throw std::runtime_error("unable to create new tap adapter");

	// Convert device GUID junk... blech
	{
		char nobraces[128];
		const char *nbtmp1 = _myDeviceInstanceId.c_str();
		char *nbtmp2 = nobraces;
		while (*nbtmp1) {
			if ((*nbtmp1 != '{')&&(*nbtmp1 != '}'))
				*nbtmp2++ = *nbtmp1;
			++nbtmp1;
		}
		*nbtmp2 = (char)0;
		if (UuidFromStringA((RPC_CSTR)nobraces,&_deviceGuid) != RPC_S_OK)
			throw std::runtime_error("unable to convert instance ID GUID to native GUID (invalid NetCfgInstanceId in registry?)");
	}

	setDhcpEnabled(false);
	setDhcp6Enabled(false);

	// Disable and enable interface to ensure registry settings take effect
	{
		STARTUPINFOA startupInfo;
		startupInfo.cb = sizeof(startupInfo);
		PROCESS_INFORMATION processInfo;
		memset(&startupInfo,0,sizeof(STARTUPINFOA));
		memset(&processInfo,0,sizeof(PROCESS_INFORMATION));
		if (!CreateProcessA(NULL,(LPSTR)(std::string("\"") + _r->homePath + devcon + "\" disable @" + _myDeviceInstanceIdPath).c_str(),NULL,NULL,FALSE,0,NULL,NULL,&startupInfo,&processInfo)) {
			RegCloseKey(nwAdapters);
			throw std::runtime_error(std::string("unable to find or execute devcon at ")+devcon);
		}
		WaitForSingleObject(processInfo.hProcess,INFINITE);
		CloseHandle(processInfo.hProcess);
		CloseHandle(processInfo.hThread);
	}
	{
		STARTUPINFOA startupInfo;
		startupInfo.cb = sizeof(startupInfo);
		PROCESS_INFORMATION processInfo;
		memset(&startupInfo,0,sizeof(STARTUPINFOA));
		memset(&processInfo,0,sizeof(PROCESS_INFORMATION));
		if (!CreateProcessA(NULL,(LPSTR)(std::string("\"") + _r->homePath + devcon + "\" enable @" + _myDeviceInstanceIdPath).c_str(),NULL,NULL,FALSE,0,NULL,NULL,&startupInfo,&processInfo)) {
			RegCloseKey(nwAdapters);
			throw std::runtime_error(std::string("unable to find or execute devcon at ")+devcon);
		}
		WaitForSingleObject(processInfo.hProcess,INFINITE);
		CloseHandle(processInfo.hProcess);
		CloseHandle(processInfo.hThread);
	}

	// Open the tap, which is in this weird Windows analog of /dev
	char tapPath[4096];
	Utils::snprintf(tapPath,sizeof(tapPath),"\\\\.\\Global\\%s.tap",_myDeviceInstanceId.c_str());
	_tap = CreateFileA(tapPath,GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_SYSTEM|FILE_FLAG_OVERLAPPED,NULL);
	if (_tap == INVALID_HANDLE_VALUE)
		throw std::runtime_error("unable to open tap in \\\\.\\Global\\ namespace");

	// Set media status to enabled
	uint32_t tmpi = 1;
	DWORD bytesReturned = 0;
	DeviceIoControl(_tap,TAP_WIN_IOCTL_SET_MEDIA_STATUS,&tmpi,sizeof(tmpi),&tmpi,sizeof(tmpi),&bytesReturned,NULL);

	// Initialized overlapped I/O structures and related events
	memset(&_tapOvlRead,0,sizeof(_tapOvlRead));
	_tapOvlRead.hEvent = CreateEvent(NULL,TRUE,FALSE,NULL);
	memset(&_tapOvlWrite,0,sizeof(_tapOvlWrite));
	_tapOvlWrite.hEvent = CreateEvent(NULL,TRUE,FALSE,NULL);

	// Start background thread that actually performs I/O
	_injectSemaphore = CreateSemaphore(NULL,0,1,NULL);
	_thread = Thread::start(this);
}

EthernetTap::~EthernetTap()
{
	_run = false;
	ReleaseSemaphore(_injectSemaphore,1,NULL);
	Thread::join(_thread);
	CloseHandle(_tap);
	CloseHandle(_tapOvlRead.hEvent);
	CloseHandle(_tapOvlWrite.hEvent);
	CloseHandle(_injectSemaphore);

	// Disable network device on shutdown
#ifdef _WIN64
	const char *devcon = "\\devcon64.exe";
#else
	BOOL f64 = FALSE;
	const char *devcon = ((IsWow64Process(GetCurrentProcess(),&f64) == TRUE) ? "\\devcon64.exe" : "\\devcon32.exe");
#endif
	{
		STARTUPINFOA startupInfo;
		startupInfo.cb = sizeof(startupInfo);
		PROCESS_INFORMATION processInfo;
		memset(&startupInfo,0,sizeof(STARTUPINFOA));
		memset(&processInfo,0,sizeof(PROCESS_INFORMATION));
		if (CreateProcessA(NULL,(LPSTR)(std::string("\"") + _r->homePath + devcon + "\" disable @" + _myDeviceInstanceIdPath).c_str(),NULL,NULL,FALSE,0,NULL,NULL,&startupInfo,&processInfo)) {
			WaitForSingleObject(processInfo.hProcess,INFINITE);
			CloseHandle(processInfo.hProcess);
			CloseHandle(processInfo.hThread);
		}
	}
}

void EthernetTap::whack()
{
}

bool EthernetTap::setDhcpEnabled(bool dhcp)
{
	HKEY tcpIpInterfaces;
	if (RegOpenKeyExA(HKEY_LOCAL_MACHINE,"SYSTEM\\CurrentControlSet\\services\\Tcpip\\Parameters\\Interfaces",0,KEY_READ|KEY_WRITE,&tcpIpInterfaces) == ERROR_SUCCESS) {
		_dhcp = dhcp;
		DWORD enable = (dhcp ? 1 : 0);
		RegSetKeyValueA(tcpIpInterfaces,_myDeviceInstanceId.c_str(),"EnableDHCP",REG_DWORD,&enable,sizeof(enable));
		RegCloseKey(tcpIpInterfaces);
	} else _dhcp = false;

	return _dhcp;
}

bool EthernetTap::setDhcp6Enabled(bool dhcp)
{
	// TODO
	return _dhcp6;
}

void EthernetTap::setDisplayName(const char *dn)
{
	HKEY ifp;
	if (RegOpenKeyExA(HKEY_LOCAL_MACHINE,(std::string("SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}\\") + _myDeviceInstanceId).c_str(),0,KEY_READ|KEY_WRITE,&ifp) == ERROR_SUCCESS) {
		RegSetKeyValueA(ifp,"Connection","Name",REG_SZ,(LPCVOID)dn,(DWORD)(strlen(dn)+1));
		RegCloseKey(ifp);
	}
}

bool EthernetTap::addIP(const InetAddress &ip)
{
	Mutex::Lock _l(_ips_m);

	if (_ips.count(ip))
		return true;

	if (!ip.port())
		return false;

	try {
		std::pair<NET_LUID,NET_IFINDEX> ifidx = _findAdapterByGuid(_deviceGuid);
		MIB_UNICASTIPADDRESS_ROW ipr;

		InitializeUnicastIpAddressEntry(&ipr);
		if (ip.isV4()) {
			ipr.Address.Ipv4.sin_family = AF_INET;
			ipr.Address.Ipv4.sin_addr.S_un.S_addr = *((const uint32_t *)ip.rawIpData());
			ipr.OnLinkPrefixLength = ip.port();
		} else if (ip.isV6()) {
		} else return false;

		ipr.PrefixOrigin = IpPrefixOriginManual;
		ipr.SuffixOrigin = IpSuffixOriginManual;
		ipr.ValidLifetime = 0xffffffff;
		ipr.PreferredLifetime = 0xffffffff;

		ipr.InterfaceLuid = ifidx.first;
		ipr.InterfaceIndex = ifidx.second;

		if (CreateUnicastIpAddressEntry(&ipr) == NO_ERROR) {
			_ips.insert(ip);
			return true;
		}
	} catch ( ... ) {}

	return false;
}

bool EthernetTap::removeIP(const InetAddress &ip)
{
	try {
		MIB_UNICASTIPADDRESS_TABLE *ipt = (MIB_UNICASTIPADDRESS_TABLE *)0;
		std::pair<NET_LUID,NET_IFINDEX> ifidx = _findAdapterByGuid(_deviceGuid);

		if (GetUnicastIpAddressTable(AF_UNSPEC,&ipt) == NO_ERROR) {
			for(DWORD i=0;i<ipt->NumEntries;++i) {
				if ((ipt->Table[i].InterfaceLuid.Value == ifidx.first.Value)&&(ipt->Table[i].InterfaceIndex == ifidx.second)) {
					InetAddress addr;
					switch(ipt->Table[i].Address.si_family) {
						case AF_INET:
							addr.set(&(ipt->Table[i].Address.Ipv4.sin_addr.S_un.S_addr),4,ipt->Table[i].OnLinkPrefixLength);
							break;
						case AF_INET6:
							addr.set(ipt->Table[i].Address.Ipv6.sin6_addr.u.Byte,16,ipt->Table[i].OnLinkPrefixLength);
							break;
					}
					if (addr == ip) {
						DeleteUnicastIpAddressEntry(&(ipt->Table[i]));
						FreeMibTable(ipt);
						Mutex::Lock _l(_ips_m);
						_ips.erase(ip);
						return true;
					}
				}
			}
			FreeMibTable(&ipt);
		}
	} catch ( ... ) {}
	return false;
}

std::set<InetAddress> EthernetTap::allIps() const
{
	static const InetAddress ifLoopback("fe80::1",64);
	std::set<InetAddress> addrs;

	try {
		MIB_UNICASTIPADDRESS_TABLE *ipt = (MIB_UNICASTIPADDRESS_TABLE *)0;
		std::pair<NET_LUID,NET_IFINDEX> ifidx = _findAdapterByGuid(_deviceGuid);

		if (GetUnicastIpAddressTable(AF_UNSPEC,&ipt) == NO_ERROR) {
			for(DWORD i=0;i<ipt->NumEntries;++i) {
				if ((ipt->Table[i].InterfaceLuid.Value == ifidx.first.Value)&&(ipt->Table[i].InterfaceIndex == ifidx.second)) {
					switch(ipt->Table[i].Address.si_family) {
						case AF_INET:
							addrs.insert(InetAddress(&(ipt->Table[i].Address.Ipv4.sin_addr.S_un.S_addr),4,ipt->Table[i].OnLinkPrefixLength));
							break;
						case AF_INET6: {
							InetAddress ip(ipt->Table[i].Address.Ipv6.sin6_addr.u.Byte,16,ipt->Table[i].OnLinkPrefixLength);
							if (ip != ifLoopback) // don't include fe80::1
								addrs.insert(ip);
						}	break;
					}
				}
			}
			FreeMibTable(ipt);
		}
	} catch ( ... ) {}

	return addrs;
}

void EthernetTap::put(const MAC &from,const MAC &to,unsigned int etherType,const void *data,unsigned int len)
{
	if (len > (ZT_IF_MTU))
		return;

	{
		Mutex::Lock _l(_injectPending_m);
		_injectPending.push( std::pair<Array<char,ZT_IF_MTU + 32>,unsigned int>(Array<char,ZT_IF_MTU + 32>(),len + 14) );
		char *d = _injectPending.back().first.data;
		memcpy(d,to.data,6);
		memcpy(d + 6,from.data,6);
		*((uint16_t *)(d + 12)) = Utils::hton(etherType);
		memcpy(d + 14,data,len);
	}

	ReleaseSemaphore(_injectSemaphore,1,NULL);
}

std::string EthernetTap::deviceName() const
{
	return _myDeviceInstanceId;
}

bool EthernetTap::updateMulticastGroups(std::set<MulticastGroup> &groups)
{
	std::set<MulticastGroup> newGroups;

	std::set<InetAddress> ipaddrs(allIps());
	for(std::set<InetAddress>::const_iterator i(ipaddrs.begin());i!=ipaddrs.end();++i)
		newGroups.insert(MulticastGroup::deriveMulticastGroupForAddressResolution(*i));

	bool changed = false;

	newGroups.insert(_blindWildcardMulticastGroup); // always join this

	for(std::set<MulticastGroup>::iterator mg(newGroups.begin());mg!=newGroups.end();++mg) {
		if (!groups.count(*mg)) {
			groups.insert(*mg);
			changed = true;
		}
	}
	for(std::set<MulticastGroup>::iterator mg(groups.begin());mg!=groups.end();) {
		if (!newGroups.count(*mg)) {
			groups.erase(mg++);
			changed = true;
		} else ++mg;
	}

	return changed;
}

void EthernetTap::threadMain()
	throw()
{
	HANDLE wait4[3];
	wait4[0] = _injectSemaphore;
	wait4[1] = _tapOvlRead.hEvent;
	wait4[2] = _tapOvlWrite.hEvent;

	ReadFile(_tap,_tapReadBuf,sizeof(_tapReadBuf),NULL,&_tapOvlRead);
	bool writeInProgress = false;

	for(;;) {
		if (!_run) break;
		WaitForMultipleObjectsEx(3,wait4,FALSE,INFINITE,TRUE);
		if (!_run) break;

		if (HasOverlappedIoCompleted(&_tapOvlRead)) {
			DWORD bytesRead = 0;
			if (GetOverlappedResult(_tap,&_tapOvlRead,&bytesRead,FALSE)) {
				if (bytesRead > 14) {
					MAC to(_tapReadBuf);
					MAC from(_tapReadBuf + 6);
					unsigned int etherType = Utils::ntoh(*((const uint16_t *)(_tapReadBuf + 12)));
					Buffer<4096> tmp(_tapReadBuf + 14,bytesRead - 14);
					//printf("GOT FRAME: %u bytes: %s\r\n",(unsigned int)bytesRead,Utils::hex(_tapReadBuf,bytesRead).c_str());
					_handler(_arg,from,to,etherType,tmp);
				}
			}
			ReadFile(_tap,_tapReadBuf,sizeof(_tapReadBuf),NULL,&_tapOvlRead);
		}

		if (writeInProgress) {
			if (HasOverlappedIoCompleted(&_tapOvlWrite)) {
				writeInProgress = false;
				_injectPending_m.lock();
				_injectPending.pop();
			} else continue; // still writing, so skip code below and wait
		} else _injectPending_m.lock();

		if (!_injectPending.empty()) {
			WriteFile(_tap,_injectPending.front().first.data,_injectPending.front().second,NULL,&_tapOvlWrite);
			writeInProgress = true;
		}

		_injectPending_m.unlock();
	}

	CancelIo(_tap);
}

} // namespace ZeroTier

#endif // __WINDOWS__ ////////////////////////////////////////////////////////