ZeroTierOne/osdep/LinuxEthernetTap.cpp

/*
 * Copyright (c)2019 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2026-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#ifdef __GNUC__
#pragma GCC diagnostic ignored "-Wrestrict"
#endif

#include "../node/Constants.hpp"
#include "../node/Metrics.hpp"

#ifdef __LINUX__

#include "../node/Dictionary.hpp"
#include "../node/Mutex.hpp"
#include "../node/Utils.hpp"
#include "LinuxEthernetTap.hpp"
#include "LinuxNetLink.hpp"
#include "OSUtils.hpp"

#include <algorithm>
#include <arpa/inet.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <linux/if.h>
#include <linux/if_addr.h>
#include <linux/if_ether.h>
#include <linux/if_tun.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utility>

#ifndef IFNAMSIZ
#define IFNAMSIZ 16
#endif

#define ZT_TAP_BUF_SIZE (1024 * 16)

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

namespace ZeroTier {

// determine if we're running a really old linux kernel.
// Kernels in the 2.6.x series don't behave the same when bringing up
// the tap devices.
//
// Returns true if the kernel major version is < 3
bool isOldLinuxKernel()
{
	struct utsname buffer;
	char* p;
	long ver[16];
	int i = 0;
	if (uname(&buffer) != 0) {
		perror("uname");
		exit(EXIT_FAILURE);
	}

	p = buffer.release;

	while (*p) {
		if (isdigit(*p)) {
			ver[i] = strtol(p, &p, 10);
			i++;
		}
		else {
			p++;
		}
	}

	return ver[0] < 3;
}

static const char _base32_chars[32] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '2', '3', '4', '5', '6', '7' };
static void _base32_5_to_8(const uint8_t* in, char* out)
{
	out[0] = _base32_chars[(in[0]) >> 3];
	out[1] = _base32_chars[(in[0] & 0x07) << 2 | (in[1] & 0xc0) >> 6];
	out[2] = _base32_chars[(in[1] & 0x3e) >> 1];
	out[3] = _base32_chars[(in[1] & 0x01) << 4 | (in[2] & 0xf0) >> 4];
	out[4] = _base32_chars[(in[2] & 0x0f) << 1 | (in[3] & 0x80) >> 7];
	out[5] = _base32_chars[(in[3] & 0x7c) >> 2];
	out[6] = _base32_chars[(in[3] & 0x03) << 3 | (in[4] & 0xe0) >> 5];
	out[7] = _base32_chars[(in[4] & 0x1f)];
}

LinuxEthernetTap::LinuxEthernetTap(
	const char* homePath,
	unsigned int concurrency,
	bool pinning,
	const MAC& mac,
	unsigned int mtu,
	unsigned int metric,
	uint64_t nwid,
	const char* friendlyName,
	void (*handler)(void*, void*, uint64_t, const MAC&, const MAC&, unsigned int, unsigned int, const void*, unsigned int),
	void* arg)
	: _handler(handler)
	, _arg(arg)
	, _nwid(nwid)
	, _mac(mac)
	, _homePath(homePath)
	, _mtu(mtu)
	, _fd(0)
	, _enabled(true)
	, _run(true)
	, _lastIfAddrsUpdate(0)
{
	static std::mutex s_tapCreateLock;
	char procpath[128], nwids[32];
	struct stat sbuf;

	// Create only one tap at a time globally.
	std::lock_guard<std::mutex> tapCreateLock(s_tapCreateLock);

	// Make sure Linux netlink is initialized.
	(void)LinuxNetLink::getInstance();

	OSUtils::ztsnprintf(nwids, sizeof(nwids), "%.16llx", nwid);

	_fd = ::open("/dev/net/tun", O_RDWR);
	if (_fd <= 0) {
		_fd = ::open("/dev/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));

	// Restore device names from legacy devicemap, but for new devices we use a base32-based
	// canonical device name.
	std::map<std::string, std::string> globalDeviceMap;
	FILE* devmapf = fopen((_homePath + ZT_PATH_SEPARATOR_S + "devicemap").c_str(), "r");
	if (devmapf) {
		char buf[256];
		while (fgets(buf, sizeof(buf), devmapf)) {
			char* x = (char*)0;
			char* y = (char*)0;
			char* saveptr = (char*)0;
			for (char* f = Utils::stok(buf, "\r\n=", &saveptr); (f); f = Utils::stok((char*)0, "\r\n=", &saveptr)) {
				if (! x)
					x = f;
				else if (! y)
					y = f;
				else
					break;
			}
			if ((x) && (y) && (x[0]) && (y[0]))
				globalDeviceMap[x] = y;
		}
		fclose(devmapf);
	}
	bool recalledDevice = false;
	std::map<std::string, std::string>::const_iterator gdmEntry = globalDeviceMap.find(nwids);
	if (gdmEntry != globalDeviceMap.end()) {
		Utils::scopy(ifr.ifr_name, sizeof(ifr.ifr_name), gdmEntry->second.c_str());
		OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
		recalledDevice = (stat(procpath, &sbuf) != 0);
	}

	if (! recalledDevice) {
#ifdef __SYNOLOGY__
		int devno = 50;
		do {
			OSUtils::ztsnprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "eth%d", devno++);
			OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
		} while (stat(procpath, &sbuf) == 0);	// try zt#++ until we find one that does not exist
#else
		uint64_t trial = 0;	  // incremented in the very unlikely event of a name collision with another network
		do {
			const uint64_t nwid40 = (nwid ^ (nwid >> 24)) + trial++;
			uint8_t tmp2[5];
			char tmp3[11];
			tmp2[0] = (uint8_t)((nwid40 >> 32) & 0xff);
			tmp2[1] = (uint8_t)((nwid40 >> 24) & 0xff);
			tmp2[2] = (uint8_t)((nwid40 >> 16) & 0xff);
			tmp2[3] = (uint8_t)((nwid40 >> 8) & 0xff);
			tmp2[4] = (uint8_t)(nwid40 & 0xff);
			tmp3[0] = 'z';
			tmp3[1] = 't';
			_base32_5_to_8(tmp2, tmp3 + 2);
			tmp3[10] = (char)0;
			memcpy(ifr.ifr_name, tmp3, 11);
			OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
		} while (stat(procpath, &sbuf) == 0);
#endif
	}

	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");
	}

	::ioctl(_fd, TUNSETPERSIST, 0);	  // valgrind may generate a false alarm here
	_dev = ifr.ifr_name;
	::fcntl(_fd, F_SETFD, fcntl(_fd, F_GETFD) | FD_CLOEXEC);

	(void)::pipe(_shutdownSignalPipe);

	for (unsigned int i = 0; i < concurrency; ++i) {
		_rxThreads.push_back(std::thread([this, i, concurrency, pinning] {
			if (pinning) {
				int pinCore = i % concurrency;
				fprintf(stderr, "Pinning tap thread %d to core %d\n", i, pinCore);
				pthread_t self = pthread_self();
				cpu_set_t cpuset;
				CPU_ZERO(&cpuset);
				CPU_SET(pinCore, &cpuset);
				int rc = pthread_setaffinity_np(self, sizeof(cpu_set_t), &cpuset);
				if (rc != 0) {
					fprintf(stderr, "Failed to pin tap thread %d to core %d: %s\n", i, pinCore, strerror(errno));
					exit(1);
				}
			}

			uint8_t b[ZT_TAP_BUF_SIZE];
			fd_set readfds, nullfds;
			int n, nfds, r;
			if (i == 0) {
				struct ifreq ifr;
				memset(&ifr, 0, sizeof(ifr));
				strcpy(ifr.ifr_name, _dev.c_str());

				const int sock = socket(AF_INET, SOCK_DGRAM, 0);
				if (sock <= 0)
					return;

				if (ioctl(sock, SIOCGIFFLAGS, (void*)&ifr) < 0) {
					::close(sock);
					printf("WARNING: ioctl() failed setting up Linux tap device (bring interface up)\n");
					return;
				}

				ifr.ifr_ifru.ifru_hwaddr.sa_family = ARPHRD_ETHER;
				_mac.copyTo(ifr.ifr_ifru.ifru_hwaddr.sa_data, 6);
				if (ioctl(sock, SIOCSIFHWADDR, (void*)&ifr) < 0) {
					::close(sock);
					printf("WARNING: ioctl() failed setting up Linux tap device (set MAC)\n");
					return;
				}

				usleep(100000);

				if (isOldLinuxKernel()) {
					ifr.ifr_ifru.ifru_mtu = (int)_mtu;
					if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
						::close(sock);
						printf("WARNING: ioctl() failed setting up Linux tap device (set MTU)\n");
						return;
					}

					usleep(100000);
				}

				ifr.ifr_flags |= IFF_MULTICAST;
				ifr.ifr_flags |= IFF_UP;
				if (ioctl(sock, SIOCSIFFLAGS, (void*)&ifr) < 0) {
					::close(sock);
					printf("WARNING: ioctl() failed setting up Linux tap device (bring interface up)\n");
					return;
				}

				usleep(100000);

				if (! isOldLinuxKernel()) {
					ifr.ifr_ifru.ifru_hwaddr.sa_family = ARPHRD_ETHER;
					_mac.copyTo(ifr.ifr_ifru.ifru_hwaddr.sa_data, 6);
					if (ioctl(sock, SIOCSIFHWADDR, (void*)&ifr) < 0) {
						::close(sock);
						printf("WARNING: ioctl() failed setting up Linux tap device (set MAC)\n");
						return;
					}

					ifr.ifr_ifru.ifru_mtu = (int)_mtu;
					if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
						::close(sock);
						printf("WARNING: ioctl() failed setting up Linux tap device (set MTU)\n");
						return;
					}
				}

				fcntl(_fd, F_SETFL, O_NONBLOCK);

				::close(sock);
			}

			if (! _run) {
				return;
			}

			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)) {
					break;
				}
				if (FD_ISSET(_fd, &readfds)) {
					for (;;) {
						// read until there are no more packets, then return to outer select() loop
						n = (int)::read(_fd, b + r, ZT_TAP_BUF_SIZE - r);
						if (n > 0) {
							// 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;

								if (_enabled) {
									MAC to(b, 6), from(b + 6, 6);
									unsigned int etherType = Utils::ntoh(((const uint16_t*)b)[6]);
									_handler(_arg, nullptr, _nwid, from, to, etherType, 0, (const void*)(b + 14), (unsigned int)(r - 14));
								}

								r = 0;
							}
						}
						else {
							r = 0;
							break;
						}
					}
				}
			}
		}));
	}
}

LinuxEthernetTap::~LinuxEthernetTap()
{
	_run = false;
	(void)::write(_shutdownSignalPipe[1], "\0", 1);
	::close(_fd);
	::close(_shutdownSignalPipe[0]);
	::close(_shutdownSignalPipe[1]);
	for (std::thread& t : _rxThreads) {
		t.join();
	}
}

void LinuxEthernetTap::setEnabled(bool en)
{
	_enabled = en;
}

bool LinuxEthernetTap::enabled() const
{
	return _enabled;
}

static bool ___removeIp(const std::string& _dev, const InetAddress& ip)
{
	LinuxNetLink::getInstance().removeAddress(ip, _dev.c_str());
	return true;
}

bool LinuxEthernetTap::addIps(std::vector<InetAddress> ips)
{
#ifdef __SYNOLOGY__
	std::string filepath = "/etc/sysconfig/network-scripts/ifcfg-" + _dev;
	std::string cfg_contents = "DEVICE=" + _dev + "\nBOOTPROTO=static";
	int ip4 = 0, ip6 = 0, ip4_tot = 0, ip6_tot = 0;

	for (int i = 0; i < (int)ips.size(); i++) {
		if (ips[i].isV4())
			ip4_tot++;
		else
			ip6_tot++;
	}
	// Assemble and write contents of ifcfg-dev file
	for (int i = 0; i < (int)ips.size(); i++) {
		if (ips[i].isV4()) {
			char iptmp[64], iptmp2[64];
			std::string numstr4 = ip4_tot > 1 ? std::to_string(ip4) : "";
			cfg_contents += "\nIPADDR" + numstr4 + "=" + ips[i].toIpString(iptmp) + "\nNETMASK" + numstr4 + "=" + ips[i].netmask().toIpString(iptmp2) + "\n";
			ip4++;
		}
		else {
			char iptmp[64], iptmp2[64];
			std::string numstr6 = ip6_tot > 1 ? std::to_string(ip6) : "";
			cfg_contents += "\nIPV6ADDR" + numstr6 + "=" + ips[i].toIpString(iptmp) + "\nNETMASK" + numstr6 + "=" + ips[i].netmask().toIpString(iptmp2) + "\n";
			ip6++;
		}
	}
	OSUtils::writeFile(filepath.c_str(), cfg_contents.c_str(), cfg_contents.length());
	// Finally, add IPs
	for (int i = 0; i < (int)ips.size(); i++) {
		LinuxNetLink::getInstance().addAddress(ips[i], _dev.c_str());
	}
	return true;
#endif	 // __SYNOLOGY__
	return false;
}

bool LinuxEthernetTap::addIp(const InetAddress& ip)
{
	if (! ip)
		return false;

	std::vector<InetAddress> allIps(ips());
	if (std::binary_search(allIps.begin(), allIps.end(), ip))
		return true;

	// Remove and reconfigure if address is the same but netmask is different
	for (std::vector<InetAddress>::iterator i(allIps.begin()); i != allIps.end(); ++i) {
		if (i->ipsEqual(ip))
			___removeIp(_dev, *i);
	}

	LinuxNetLink::getInstance().addAddress(ip, _dev.c_str());

	return true;
}

bool LinuxEthernetTap::removeIp(const InetAddress& ip)
{
	if (! ip)
		return true;
	std::vector<InetAddress> allIps(ips());
	if (std::find(allIps.begin(), allIps.end(), ip) != allIps.end()) {
		if (___removeIp(_dev, ip))
			return true;
	}
	return false;
}

std::vector<InetAddress> LinuxEthernetTap::ips() const
{
	uint64_t now = OSUtils::now();

	if ((now - _lastIfAddrsUpdate) <= GETIFADDRS_CACHE_TIME) {
		return _ifaddrs;
	}
	_lastIfAddrsUpdate = now;

	struct ifaddrs* ifa = (struct ifaddrs*)0;
	if (getifaddrs(&ifa))
		return std::vector<InetAddress>();

	std::vector<InetAddress> r;

	struct ifaddrs* p = ifa;
	while (p) {
		if ((! strcmp(p->ifa_name, _dev.c_str())) && (p->ifa_addr) && (p->ifa_netmask) && (p->ifa_addr->sa_family == p->ifa_netmask->sa_family)) {
			switch (p->ifa_addr->sa_family) {
				case AF_INET: {
					struct sockaddr_in* sin = (struct sockaddr_in*)p->ifa_addr;
					struct sockaddr_in* nm = (struct sockaddr_in*)p->ifa_netmask;
					r.push_back(InetAddress(&(sin->sin_addr.s_addr), 4, Utils::countBits((uint32_t)nm->sin_addr.s_addr)));
				} break;
				case AF_INET6: {
					struct sockaddr_in6* sin = (struct sockaddr_in6*)p->ifa_addr;
					struct sockaddr_in6* nm = (struct sockaddr_in6*)p->ifa_netmask;
					uint32_t b[4];
					memcpy(b, nm->sin6_addr.s6_addr, sizeof(b));
					r.push_back(InetAddress(sin->sin6_addr.s6_addr, 16, Utils::countBits(b[0]) + Utils::countBits(b[1]) + Utils::countBits(b[2]) + Utils::countBits(b[3])));
				} break;
			}
		}
		p = p->ifa_next;
	}

	if (ifa)
		freeifaddrs(ifa);

	std::sort(r.begin(), r.end());
	r.erase(std::unique(r.begin(), r.end()), r.end());

	_ifaddrs = r;

	return r;
}

void LinuxEthernetTap::put(const MAC& from, const MAC& to, unsigned int etherType, const void* data, unsigned int len)
{
	// VL2 frame size histogram
	ZeroTier::Metrics::vl2_frame_size_hist.Observe(len);
	if (len > this->_mtu) {
		ZeroTier::Metrics::vl2_would_fragment_or_drop_rx++;
	}
	char putBuf[ZT_MAX_MTU + 64];
	if ((_fd > 0) && (len <= _mtu) && (_enabled)) {
		to.copyTo(putBuf, 6);
		from.copyTo(putBuf + 6, 6);
		*((uint16_t*)(putBuf + 12)) = htons((uint16_t)etherType);
		memcpy(putBuf + 14, data, len);
		len += 14;
		(void)::write(_fd, putBuf, len);
	}
}

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

void LinuxEthernetTap::setFriendlyName(const char* friendlyName)
{
}

void LinuxEthernetTap::scanMulticastGroups(std::vector<MulticastGroup>& added, std::vector<MulticastGroup>& removed)
{
	char *ptr, *ptr2;
	unsigned char mac[6];
	std::vector<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.c_str())) && (mcastmac) && (Utils::unhex(mcastmac, mac, 6) == 6))
					newGroups.push_back(MulticastGroup(MAC(mac, 6), 0));
			}
		}
		::close(fd);
	}

	std::vector<InetAddress> allIps(ips());
	for (std::vector<InetAddress>::iterator ip(allIps.begin()); ip != allIps.end(); ++ip)
		newGroups.push_back(MulticastGroup::deriveMulticastGroupForAddressResolution(*ip));

	std::sort(newGroups.begin(), newGroups.end());
	newGroups.erase(std::unique(newGroups.begin(), newGroups.end()), newGroups.end());

	for (std::vector<MulticastGroup>::iterator m(newGroups.begin()); m != newGroups.end(); ++m) {
		if (! std::binary_search(_multicastGroups.begin(), _multicastGroups.end(), *m))
			added.push_back(*m);
	}
	for (std::vector<MulticastGroup>::iterator m(_multicastGroups.begin()); m != _multicastGroups.end(); ++m) {
		if (! std::binary_search(newGroups.begin(), newGroups.end(), *m))
			removed.push_back(*m);
	}

	_multicastGroups.swap(newGroups);
}

void LinuxEthernetTap::setMtu(unsigned int mtu)
{
	if (_mtu != mtu) {
		_mtu = mtu;
		int sock = socket(AF_INET, SOCK_DGRAM, 0);
		if (sock > 0) {
			struct ifreq ifr;
			memset(&ifr, 0, sizeof(ifr));
			strcpy(ifr.ifr_name, _dev.c_str());
			ifr.ifr_ifru.ifru_mtu = (int)mtu;
			if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
				printf("WARNING: ioctl() failed updating existing Linux tap device (set MTU)\n");
			}
			close(sock);
		}
	}
}

}	// namespace ZeroTier

#endif	 // __LINUX__