Binder.hpp

/*
 * Copyright (c)2013-2020 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.
 */
/****/

#ifndef ZT_BINDER_HPP
#define ZT_BINDER_HPP

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

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef __WINDOWS__
#include <shlobj.h>
#include <winsock2.h>
#include <windows.h>
#include <iphlpapi.h>
#include <netioapi.h>
#else
#include <ifaddrs.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#ifdef __LINUX__
#include <net/if.h>
#include <sys/ioctl.h>
#include <linux/if_addr.h>
#endif
#endif

#if (defined(__unix__) || defined(__APPLE__)) && !defined(__LINUX__) && !defined(ZT_SDK)
#include <net/if.h>
#if TARGET_OS_OSX
#include <netinet6/in6_var.h>
#endif
#include <sys/ioctl.h>
#endif

#include "../node/InetAddress.hpp"
#include "../node/Mutex.hpp"
#include "../node/Utils.hpp"
#include "OSUtils.hpp"
#include "Phy.hpp"

#include <algorithm>
#include <atomic>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>

// Period between refreshes of bindings
#define ZT_BINDER_REFRESH_PERIOD 30000

// Max number of bindings
#define ZT_BINDER_MAX_BINDINGS 256

// Maximum physical interface name length. This number is gigantic because of Windows.
#define ZT_MAX_PHYSIFNAME 256

namespace ZeroTier {

/**
 * Enumerates local devices and binds to all potential ZeroTier path endpoints
 *
 * This replaces binding to wildcard (0.0.0.0 and ::0) with explicit binding
 * as part of the path to default gateway support. Under the hood it uses
 * different queries on different OSes to enumerate devices, and also exposes
 * device enumeration and endpoint IP data for use elsewhere.
 *
 * On OSes that do not support local port enumeration or where this is not
 * meaningful, this degrades to binding to wildcard.
 */
class Binder {
  private:
	struct _Binding {
		_Binding() : udpSock((PhySocket*)0)
		{
		}
		PhySocket* udpSock;
		InetAddress address;
		char ifname[256] = {};
	};

  public:
	Binder() : _bindingCount(0)
	{
	}

	/**
	 * Close all bound ports, should be called on shutdown
	 *
	 * @param phy Physical interface
	 */
	template <typename PHY_HANDLER_TYPE> void closeAll(Phy<PHY_HANDLER_TYPE>& phy)
	{
		Mutex::Lock _l(_lock);
		for (unsigned int b = 0, c = _bindingCount; b < c; ++b) {
			phy.close(_bindings[b].udpSock, false);
		}
		_bindingCount = 0;
	}

	/**
	 * Scan local devices and addresses and rebind TCP and UDP
	 *
	 * This should be called after wake from sleep, on detected network device
	 * changes, on startup, or periodically (e.g. every 30-60s).
	 *
	 * @param phy Physical interface
	 * @param ports Ports to bind on all interfaces
	 * @param portCount Number of ports
	 * @param explicitBind If present, override interface IP detection and bind to these (if possible)
	 * @param ifChecker Interface checker function to see if an interface should be used
	 * @tparam PHY_HANDLER_TYPE Type for Phy<> template
	 * @tparam INTERFACE_CHECKER Type for class containing shouldBindInterface() method
	 */
	template <typename PHY_HANDLER_TYPE, typename INTERFACE_CHECKER> void refresh(Phy<PHY_HANDLER_TYPE>& phy, unsigned int* ports, unsigned int portCount, const std::vector<InetAddress> explicitBind, INTERFACE_CHECKER& ifChecker)
	{
		std::map<InetAddress, std::string> localIfAddrs;
		PhySocket *udps;
		Mutex::Lock _l(_lock);
		bool interfacesEnumerated = true;

		if (explicitBind.empty()) {
#ifdef __WINDOWS__

			char aabuf[32768];
			ULONG aalen = sizeof(aabuf);
			if (GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_ANYCAST | GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER, (void*)0, reinterpret_cast<PIP_ADAPTER_ADDRESSES>(aabuf), &aalen) == NO_ERROR) {
				PIP_ADAPTER_ADDRESSES a = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(aabuf);
				while (a) {
					PIP_ADAPTER_UNICAST_ADDRESS ua = a->FirstUnicastAddress;
					while (ua) {
						// Don't bind temporary/random IPv6 addresses
						if (ua->SuffixOrigin != IpSuffixOriginRandom) {
							InetAddress ip(ua->Address.lpSockaddr);
							char strBuf[128] = { 0 };
							wcstombs(strBuf, a->FriendlyName, sizeof(strBuf));
							if (ifChecker.shouldBindInterface(strBuf, ip)) {
								switch (ip.ipScope()) {
									default:
										break;
									case InetAddress::IP_SCOPE_PSEUDOPRIVATE:
									case InetAddress::IP_SCOPE_GLOBAL:
									case InetAddress::IP_SCOPE_SHARED:
									case InetAddress::IP_SCOPE_PRIVATE:
										for (int x = 0; x < (int)portCount; ++x) {
											ip.setPort(ports[x]);
											localIfAddrs.insert(std::pair<InetAddress, std::string>(ip, std::string()));
										}
										break;
								}
							}
						}
						ua = ua->Next;
					}
					a = a->Next;
				}
			}
			else {
				interfacesEnumerated = false;
			}

#else	// not __WINDOWS__

			/* On Linux we use an alternative method if available since getifaddrs()
			 * gets very slow when there are lots of network namespaces. This won't
			 * work unless /proc/PID/net/if_inet6 exists and it may not on some
			 * embedded systems, so revert to getifaddrs() there. */

#ifdef __LINUX__
			char fn[256], tmp[256];
			std::set<std::string> ifnames;
			const unsigned long pid = (unsigned long)getpid();

			// Get all device names
			OSUtils::ztsnprintf(fn, sizeof(fn), "/proc/%lu/net/dev", pid);
			FILE* procf = fopen(fn, "r");
			if (procf) {
				while (fgets(tmp, sizeof(tmp), procf)) {
					tmp[255] = 0;
					char* saveptr = (char*)0;
					for (char* f = Utils::stok(tmp, " \t\r\n:|", &saveptr); (f); f = Utils::stok((char*)0, " \t\r\n:|", &saveptr)) {
						if ((strcmp(f, "Inter-") != 0) && (strcmp(f, "face") != 0) && (f[0] != 0))
							ifnames.insert(f);
						break;	 // we only want the first field
					}
				}
				fclose(procf);
			}
			else {
				interfacesEnumerated = false;
			}

			// Get IPv6 addresses (and any device names we don't already know)
			OSUtils::ztsnprintf(fn, sizeof(fn), "/proc/%lu/net/if_inet6", pid);
			procf = fopen(fn, "r");
			if (procf) {
				while (fgets(tmp, sizeof(tmp), procf)) {
					tmp[255] = 0;
					char* saveptr = (char*)0;
					unsigned char ipbits[16];
					memset(ipbits, 0, sizeof(ipbits));
					char* devname = (char*)0;
					int flags = 0;
					int n = 0;
					for (char* f = Utils::stok(tmp, " \t\r\n", &saveptr); (f); f = Utils::stok((char*)0, " \t\r\n", &saveptr)) {
						switch (n++) {
							case 0:	  // IP in hex
								Utils::unhex(f, 32, ipbits, 16);
								break;
							case 4:
								flags = atoi(f);
								break;
							case 5:	  // device name
								devname = f;
								break;
						}
					}

					if ( (flags & IFA_F_TEMPORARY) != 0) {
						continue;
					}
					if (devname) {
						ifnames.insert(devname);
						InetAddress ip(ipbits, 16, 0);
						if (ifChecker.shouldBindInterface(devname, ip)) {
							switch (ip.ipScope()) {
								default:
									break;
								case InetAddress::IP_SCOPE_PSEUDOPRIVATE:
								case InetAddress::IP_SCOPE_GLOBAL:
								case InetAddress::IP_SCOPE_SHARED:
								case InetAddress::IP_SCOPE_PRIVATE:
									for (int x = 0; x < (int)portCount; ++x) {
										ip.setPort(ports[x]);
										localIfAddrs.insert(std::pair<InetAddress, std::string>(ip, std::string(devname)));
									}
									break;
							}
						}
					}
				}
				fclose(procf);
			}

			// Get IPv4 addresses for each device
			if (! ifnames.empty()) {
				const int controlfd = (int)socket(AF_INET, SOCK_DGRAM, 0);
				struct ifconf configuration;
				configuration.ifc_len = 0;
				configuration.ifc_buf = nullptr;

				if (controlfd < 0)
					goto ip4_address_error;
				if (ioctl(controlfd, SIOCGIFCONF, &configuration) < 0)
					goto ip4_address_error;
				configuration.ifc_buf = (char*)malloc(configuration.ifc_len);
				if (ioctl(controlfd, SIOCGIFCONF, &configuration) < 0)
					goto ip4_address_error;

				for (int i = 0; i < (int)(configuration.ifc_len / sizeof(ifreq)); i++) {
					struct ifreq& request = configuration.ifc_req[i];
					struct sockaddr* addr = &request.ifr_ifru.ifru_addr;
					if (addr->sa_family != AF_INET)
						continue;
					std::string ifname = request.ifr_ifrn.ifrn_name;
					// name can either be just interface name or interface name followed by ':' and arbitrary label
					if (ifname.find(':') != std::string::npos)
						ifname = ifname.substr(0, ifname.find(':'));

					InetAddress ip(&(((struct sockaddr_in*)addr)->sin_addr), 4, 0);
					if (ifChecker.shouldBindInterface(ifname.c_str(), ip)) {
						switch (ip.ipScope()) {
							default:
								break;
							case InetAddress::IP_SCOPE_PSEUDOPRIVATE:
							case InetAddress::IP_SCOPE_GLOBAL:
							case InetAddress::IP_SCOPE_SHARED:
							case InetAddress::IP_SCOPE_PRIVATE:
								for (int x = 0; x < (int)portCount; ++x) {
									ip.setPort(ports[x]);
									localIfAddrs.insert(std::pair<InetAddress, std::string>(ip, ifname));
								}
								break;
						}
					}
				}

			ip4_address_error:
				free(configuration.ifc_buf);
				if (controlfd > 0)
					close(controlfd);
			}

			const bool gotViaProc = (! localIfAddrs.empty());
#else
			const bool gotViaProc = false;
#endif

			//
			// prevent:
			// warning: unused variable 'gotViaProc'
			//
			(void)gotViaProc;

#if ! defined(__ANDROID__)	  // getifaddrs() freeifaddrs() not available on Android
			if (! gotViaProc) {
				struct ifaddrs* ifatbl = (struct ifaddrs*)0;
				struct ifaddrs* ifa;
#if (defined(__unix__) || defined(__APPLE__)) && !defined(__LINUX__) && !defined(ZT_SDK)
				// set up an IPv6 socket so we can check the state of interfaces via SIOCGIFAFLAG_IN6
				int infoSock = socket(AF_INET6, SOCK_DGRAM, 0);
#endif
				if ((getifaddrs(&ifatbl) == 0) && (ifatbl)) {
					ifa = ifatbl;
					while (ifa) {
						if ((ifa->ifa_name) && (ifa->ifa_addr)) {
							InetAddress ip = *(ifa->ifa_addr);
#if (defined(__unix__) || defined(__APPLE__)) && !defined(__LINUX__) && !defined(ZT_SDK) && TARGET_OS_OSX
							// Check if the address is an IPv6 Temporary Address, macOS/BSD version
							if (ifa->ifa_addr->sa_family == AF_INET6) {
								struct sockaddr_in6* sa6 = (struct sockaddr_in6*)ifa->ifa_addr;
								struct in6_ifreq ifr6;
								memset(&ifr6, 0, sizeof(ifr6));
								strcpy(ifr6.ifr_name, ifa->ifa_name);
								ifr6.ifr_ifru.ifru_addr = *sa6;

								int flags = 0;
								if (ioctl(infoSock, SIOCGIFAFLAG_IN6, (unsigned long long)&ifr6) != -1) {
									flags = ifr6.ifr_ifru.ifru_flags6;
								}

								// if this is a temporary IPv6 address, skip to the next address
								if (flags & IN6_IFF_TEMPORARY) {
#ifdef ZT_TRACE
									char buf[64];
									fprintf(stderr, "skip binding to temporary IPv6 address: %s\n", ip.toIpString(buf));
#endif
									ifa = ifa->ifa_next;
									continue;
								}
							}
#endif
							if (ifChecker.shouldBindInterface(ifa->ifa_name, ip)) {
								switch (ip.ipScope()) {
									default:
										break;
									case InetAddress::IP_SCOPE_PSEUDOPRIVATE:
									case InetAddress::IP_SCOPE_GLOBAL:
									case InetAddress::IP_SCOPE_SHARED:
									case InetAddress::IP_SCOPE_PRIVATE:
										for (int x = 0; x < (int)portCount; ++x) {
											ip.setPort(ports[x]);
											localIfAddrs.insert(std::pair<InetAddress, std::string>(ip, std::string(ifa->ifa_name)));
										}
										break;
								}
							}
						}
						ifa = ifa->ifa_next;
					}
					freeifaddrs(ifatbl);
				}
				else {
					interfacesEnumerated = false;
				}
#if (defined(__unix__) || defined(__APPLE__)) && !defined(__LINUX__) && !defined(ZT_SDK)
				close(infoSock);
#endif
			}
#endif

#endif
		}
		else {
			for (std::vector<InetAddress>::const_iterator i(explicitBind.begin()); i != explicitBind.end(); ++i) {
				InetAddress ip = InetAddress(*i);
				for (int x = 0; x < (int)portCount; ++x) {
					ip.setPort(ports[x]);
					localIfAddrs.insert(std::pair<InetAddress, std::string>(ip, std::string()));
				}
			}
		}

		// Default to binding to wildcard if we can't enumerate addresses
		if (! interfacesEnumerated && localIfAddrs.empty()) {
			for (int x = 0; x < (int)portCount; ++x) {
				localIfAddrs.insert(std::pair<InetAddress, std::string>(InetAddress((uint32_t)0, ports[x]), std::string()));
				localIfAddrs.insert(std::pair<InetAddress, std::string>(InetAddress((const void*)"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16, ports[x]), std::string()));
			}
		}

		const unsigned int oldBindingCount = _bindingCount;
		_bindingCount = 0;

		// Save bindings that are still valid, close those that are not
		for (unsigned int b = 0; b < oldBindingCount; ++b) {
			if (localIfAddrs.find(_bindings[b].address) != localIfAddrs.end()) {
				if (_bindingCount != b)
					_bindings[(unsigned int)_bindingCount] = _bindings[b];
				++_bindingCount;
			}
			else {
				PhySocket* const udps = _bindings[b].udpSock;
				_bindings[b].udpSock = (PhySocket*)0;
				phy.close(udps, false);
			}
		}

		// Create new bindings for those not already bound
		for (std::map<InetAddress, std::string>::const_iterator ii(localIfAddrs.begin()); ii != localIfAddrs.end(); ++ii) {
			unsigned int bi = 0;
			while (bi != _bindingCount) {
				if (_bindings[bi].address == ii->first)
					break;
				++bi;
			}
			if (bi == _bindingCount) {
				udps = phy.udpBind(reinterpret_cast<const struct sockaddr*>(&(ii->first)), (void*)0, ZT_UDP_DESIRED_BUF_SIZE);
				if (udps) {
#ifdef __LINUX__
					// Bind Linux sockets to their device so routes that we manage do not override physical routes (wish all platforms had this!)
					if (ii->second.length() > 0) {
						char tmp[256];
						Utils::scopy(tmp, sizeof(tmp), ii->second.c_str());
						int fd = (int)Phy<PHY_HANDLER_TYPE>::getDescriptor(udps);
						if (fd >= 0) {
							setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, tmp, strlen(tmp));
						}
					}
#endif	 // __LINUX__
					if (_bindingCount < ZT_BINDER_MAX_BINDINGS) {
						_bindings[_bindingCount].udpSock = udps;
						_bindings[_bindingCount].address = ii->first;
						memcpy(_bindings[_bindingCount].ifname, (char*)ii->second.c_str(), (int)ii->second.length());
						++_bindingCount;
					}
				}
				else {
					phy.close(udps, false);
				}
			}
		}
	}

	/**
	 * @return All currently bound local interface addresses
	 */
	inline std::vector<InetAddress> allBoundLocalInterfaceAddresses() const
	{
		std::vector<InetAddress> aa;
		Mutex::Lock _l(_lock);
		for (unsigned int b = 0, c = _bindingCount; b < c; ++b)
			aa.push_back(_bindings[b].address);
		return aa;
	}

	/**
	 * Send from all bound UDP sockets
	 */
	template <typename PHY_HANDLER_TYPE> inline bool udpSendAll(Phy<PHY_HANDLER_TYPE>& phy, const struct sockaddr_storage* addr, const void* data, unsigned int len, unsigned int ttl)
	{
		bool r = false;
		Mutex::Lock _l(_lock);
		for (unsigned int b = 0, c = _bindingCount; b < c; ++b) {
			if (ttl)
				phy.setIp4UdpTtl(_bindings[b].udpSock, ttl);
			if (phy.udpSend(_bindings[b].udpSock, (const struct sockaddr*)addr, data, len))
				r = true;
			if (ttl)
				phy.setIp4UdpTtl(_bindings[b].udpSock, 255);
		}
		return r;
	}

	/**
	 * @param addr Address to check
	 * @return True if this is a bound local interface address
	 */
	inline bool isBoundLocalInterfaceAddress(const InetAddress& addr) const
	{
		Mutex::Lock _l(_lock);
		for (unsigned int b = 0; b < _bindingCount; ++b) {
			if (_bindings[b].address == addr)
				return true;
		}
		return false;
	}

	/**
	 * Quickly check that a UDP socket is valid
	 *
	 * @param udpSock UDP socket to check
	 * @return True if socket is currently bound/allocated
	 */
	inline bool isUdpSocketValid(PhySocket* const udpSock)
	{
		for (unsigned int b = 0, c = _bindingCount; b < c; ++b) {
			if (_bindings[b].udpSock == udpSock)
				return (b < _bindingCount);	  // double check atomic which may have changed
		}
		return false;
	}

	/**
	 * @param s Socket object
	 * @param nameBuf Buffer to store name of interface which this Socket object is bound to
	 * @param buflen Length of buffer to copy name into
	 */
	void getIfName(PhySocket* s, char* nameBuf, int buflen) const
	{
		Mutex::Lock _l(_lock);
		for (unsigned int b = 0, c = _bindingCount; b < c; ++b) {
			if (_bindings[b].udpSock == s) {
				memcpy(nameBuf, _bindings[b].ifname, buflen);
				break;
			}
		}
	}

  private:
	_Binding _bindings[ZT_BINDER_MAX_BINDINGS];
	std::atomic<unsigned int> _bindingCount;
	Mutex _lock;
};

}	// namespace ZeroTier

#endif