/*
 * 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 <iostream>
#include <string>
#include "EthernetTap.hpp"
#include "Logger.hpp"
#include "RuntimeEnvironment.hpp"
#include "Utils.hpp"
#include "Mutex.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>

#ifdef __LINUX__

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

#define ZT_ETHERTAP_IP_COMMAND "/sbin/ip"
#define ZT_ETHERTAP_SYSCTL_COMMAND "/sbin/sysctl"

#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>

#define ZT_ETHERTAP_IFCONFIG "/sbin/ifconfig"
#define ZT_MAC_KEXTLOAD "/sbin/kextload"
#define ZT_MAC_IPCONFIG "/usr/sbin/ipconfig"

#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 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 {
			sprintf(ifr.ifr_name,"zt%d",devno++);
			sprintf(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 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 devpath[64],ethaddr[64],mtustr[16];
	struct stat tmp;
	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
	if (stat("/dev/zt0",&tmp)) {
		int kextpid;
		char tmp[4096];
		strcpy(tmp,_r->homePath.c_str());
		if ((kextpid = (int)vfork()) == 0) {
			chdir(tmp);
			execl(ZT_MAC_KEXTLOAD,ZT_MAC_KEXTLOAD,"-q","-repository",tmp,"tap.kext",(const char *)0);
			exit(-1);
		} else {
			int exitcode = -1;
			waitpid(kextpid,&exitcode,0);
			usleep(500);
		}
	}
	if (stat("/dev/zt0",&tmp))
		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) {
		sprintf(devpath,"/dev/zt%d",i);
		if (stat(devpath,&tmp))
			throw std::runtime_error("no more TAP devices available");
		_fd = ::open(devpath,O_RDWR);
		if (_fd > 0) {
			sprintf(_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");
	}

	sprintf(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]);
	sprintf(mtustr,"%u",mtu);

	// Configure MAC address and MTU, bring interface up
	long cpid;
	if ((cpid = (long)vfork()) == 0) {
		execl(ZT_ETHERTAP_IFCONFIG,ZT_ETHERTAP_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);
}
#endif // __APPLE__

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

#ifdef __APPLE__
void EthernetTap::whack()
{
	long cpid = (long)vfork();
	if (cpid == 0) {
		execl(ZT_MAC_IPCONFIG,ZT_MAC_IPCONFIG,"set",_dev,"AUTOMATIC-V6",(const char *)0);
		exit(-1);
	} else {
		int exitcode = -1;
		waitpid(cpid,&exitcode,0);
		if (exitcode) {
			LOG("%s: ipconfig set AUTOMATIC-V6 failed",_dev);
		}
	}
}
#else
void EthernetTap::whack() {}
#endif // __APPLE__ / !__APPLE__

#ifdef __LINUX__
static bool ___removeIp(const char *_dev,const InetAddress &ip)
{
	long cpid = (long)vfork();
	if (cpid == 0) {
		execl(ZT_ETHERTAP_IP_COMMAND,ZT_ETHERTAP_IP_COMMAND,"addr","del",ip.toString().c_str(),"dev",_dev,(const char *)0);
		exit(1); /* not reached unless exec fails */
	} else {
		int exitcode = 1;
		waitpid(cpid,&exitcode,0);
		return (exitcode == 0);
	}
}

bool EthernetTap::addIP(const InetAddress &ip)
{
	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(ZT_ETHERTAP_IP_COMMAND,ZT_ETHERTAP_IP_COMMAND,"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)
{
	int cpid;
	if ((cpid = (int)vfork()) == 0) {
		execl(ZT_ETHERTAP_IFCONFIG,ZT_ETHERTAP_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)
{
	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());
			}
		}
	}

	int cpid;
	if ((cpid = (int)vfork()) == 0) {
		execl(ZT_ETHERTAP_IFCONFIG,ZT_ETHERTAP_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;
}

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;
	char getBuf[4096 + 14];
	Buffer<4096> data;

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

	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)) {
			int n = (int)::read(_fd,getBuf,_mtu + 14);

			if (n > 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];
				data.copyFrom(getBuf + 14,(unsigned int)n - 14);
				_handler(_arg,from,to,ntohs(((const uint16_t *)getBuf)[6]),data);
			} else if (n < 0) {
				if ((errno != EINTR)&&(errno != ETIMEDOUT)) {
					TRACE("unexpected error reading from tap: %s",strerror(errno));
					break;
				}
			}
		}
	}
}

} // namespace ZeroTier

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

#ifdef __WINDOWS__

// TODO

#endif // __WINDOWS__