text: /*
  
  Copyright (c) 2007-2018, Arvid Norberg
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
  
      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the distribution.
      * Neither the name of the author nor the names of its
        contributors may be used to endorse or promote products derived
        from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.
  
  */
  
  #include "libtorrent/config.hpp"
  #include "libtorrent/enum_net.hpp"
  #include "libtorrent/broadcast_socket.hpp"
  #include "libtorrent/assert.hpp"
  #include "libtorrent/aux_/socket_type.hpp"
  #ifdef TORRENT_WINDOWS
  #include "libtorrent/aux_/win_util.hpp"
  #endif
  
  #include <functional>
  #include <cstdlib> // for wcstombscstombs
  
  #include "libtorrent/aux_/disable_warnings_push.hpp"
  
  #include <boost/asio/ip/host_name.hpp>
  #include <boost/optional.hpp>
  
  #if TORRENT_USE_IFCONF
  #include <sys/ioctl.h>
  #include <sys/socket.h>
  #include <netinet/in.h>
  #include <net/if.h>
  #include <cstring>
  #endif
  
  #if TORRENT_USE_SYSCTL
  #include <sys/sysctl.h>
  #ifdef __APPLE__
  #include "TargetConditionals.h"
  #endif
  
  #if defined TARGET_IPHONE_SIMULATOR || defined TARGET_OS_IPHONE
  // net/route.h is not included in the iphone sdk.
  #include "libtorrent/aux_/route.h"
  #else
  #include <net/route.h>
  #endif
  #endif // TORRENT_USE_SYSCTL
  
  #if TORRENT_USE_GETIPFORWARDTABLE || TORRENT_USE_GETADAPTERSADDRESSES
  #include "libtorrent/aux_/windows.hpp"
  #include <iphlpapi.h>
  #endif
  
  #if TORRENT_USE_NETLINK
  #include <linux/netlink.h>
  #include <linux/rtnetlink.h>
  #include <asm/types.h>
  #include <netinet/ether.h>
  #include <netinet/in.h>
  #include <net/if.h>
  #include <cstdio>
  #include <sys/socket.h>
  #include <sys/ioctl.h>
  #include <sys/types.h>
  #include <arpa/inet.h>
  #include <string.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sys/types.h>
  
  #if defined TORRENT_ANDROID && !defined IFA_F_DADFAILED
  #define IFA_F_DADFAILED 8
  #endif
  
  #endif
  
  #if TORRENT_USE_IFADDRS
  #include <ifaddrs.h>
  #endif
  
  #if TORRENT_USE_IFADDRS || TORRENT_USE_IFCONF || TORRENT_USE_NETLINK || TORRENT_USE_SYSCTL
  // capture this here where warnings are disabled (the macro generates warnings)
  const unsigned long siocgifmtu = SIOCGIFMTU;
  #endif
  
  #include "libtorrent/aux_/disable_warnings_pop.hpp"
  
  #if defined(TORRENT_OS2) && !defined(IF_NAMESIZE)
  #define IF_NAMESIZE IFNAMSIZ
  #endif
  
  namespace libtorrent {
  namespace {
  
  
  #if !defined TORRENT_BUILD_SIMULATOR
  	address_v4 inaddr_to_address(void const* ina, int const len = 4)
  	{
  		boost::asio::ip::address_v4::bytes_type b = {};
  		if (len > 0) std::memcpy(b.data(), ina, std::min(std::size_t(len), b.size()));
  		return address_v4(b);
  	}
  
  	address_v6 inaddr6_to_address(void const* ina6, int const len = 16)
  	{
  		boost::asio::ip::address_v6::bytes_type b = {};
  		if (len > 0) std::memcpy(b.data(), ina6, std::min(std::size_t(len), b.size()));
  		return address_v6(b);
  	}
  
  #if !TORRENT_USE_NETLINK
  	int sockaddr_len(sockaddr const* sin)
  	{
  #if TORRENT_HAS_SALEN
  		return sin->sa_len;
  #else
  		return sin->sa_family == AF_INET ? sizeof(sockaddr_in) : sizeof(sockaddr_in6);
  #endif
  	}
  
  	address sockaddr_to_address(sockaddr const* sin, int assume_family = -1)
  	{
  		if (sin->sa_family == AF_INET || assume_family == AF_INET)
  			return inaddr_to_address(&reinterpret_cast<sockaddr_in const*>(sin)->sin_addr
  				, sockaddr_len(sin) - int(offsetof(sockaddr, sa_data)));
  		else if (sin->sa_family == AF_INET6 || assume_family == AF_INET6)
  		{
  			auto saddr = reinterpret_cast<sockaddr_in6 const*>(sin);
  			auto ret = inaddr6_to_address(&saddr->sin6_addr
  				, sockaddr_len(sin) - int(offsetof(sockaddr, sa_data)));
  			ret.scope_id(saddr->sin6_scope_id);
  			return ret;
  		}
  		return address();
  	}
  #endif
  
  	bool valid_addr_family(int family)
  	{
  		return (family == AF_INET
  			|| family == AF_INET6
  		);
  	}
  
  #if TORRENT_USE_NETLINK
  
  	int read_nl_sock(int sock, span<char> buf, std::uint32_t const seq, std::uint32_t const pid)
  	{
  		nlmsghdr* nl_hdr;
  
  		int msg_len = 0;
  
  		for (;;)
  		{
  			auto next_msg = buf.subspan(msg_len);
  			int const read_len = int(recv(sock, next_msg.data(), static_cast<std::size_t>(next_msg.size()), 0));
  			if (read_len < 0) return -1;
  
  			nl_hdr = reinterpret_cast<nlmsghdr*>(next_msg.data());
  
  #ifdef __clang__
  #pragma clang diagnostic push
  // NLMSG_OK uses signed/unsigned compare in the same expression
  #pragma clang diagnostic ignored "-Wsign-compare"
  #endif
  			if ((NLMSG_OK(nl_hdr, read_len) == 0) || (nl_hdr->nlmsg_type == NLMSG_ERROR))
  				return -1;
  #ifdef __clang__
  #pragma clang diagnostic pop
  #endif
  
  			// this function doesn't handle multiple requests at the same time
  			// so report an error if the message does not have the expected seq and pid
  			if (nl_hdr->nlmsg_seq != seq || nl_hdr->nlmsg_pid != pid)
  				return -1;
  
  			if (nl_hdr->nlmsg_type == NLMSG_DONE) break;
  
  			msg_len += read_len;
  
  			if ((nl_hdr->nlmsg_flags & NLM_F_MULTI) == 0) break;
  		}
  		return msg_len;
  	}
  
  	constexpr int NL_BUFSIZE = 8192;
  
  	int nl_dump_request(int sock, std::uint16_t type, std::uint32_t seq, char family, span<char> msg, std::size_t msg_len)
  	{
  		nlmsghdr* nl_msg = reinterpret_cast<nlmsghdr*>(msg.data());
  		nl_msg->nlmsg_len = std::uint32_t(NLMSG_LENGTH(msg_len));
  		nl_msg->nlmsg_type = type;
  		nl_msg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
  		nl_msg->nlmsg_seq = seq;
  		// in theory nlmsg_pid should be set to the netlink port ID (NOT the process ID)
  		// of the sender, but the kernel ignores this field so it is typically set to
  		// zero
  		nl_msg->nlmsg_pid = 0;
  		// first byte of routing messages is always the family
  		msg[sizeof(nlmsghdr)] = family;
  
  		if (::send(sock, nl_msg, nl_msg->nlmsg_len, 0) < 0)
  		{
  			return -1;
  		}
  
  		// get the socket's port ID so that we can verify it in the repsonse
  		sockaddr_nl sock_addr;
  		socklen_t sock_addr_len = sizeof(sock_addr);
  		if (::getsockname(sock, reinterpret_cast<sockaddr*>(&sock_addr), &sock_addr_len) < 0)
  		{
  			return -1;
  		}
  
  		return read_nl_sock(sock, msg, seq, sock_addr.nl_pid);
  	}
  
  	address to_address(int const address_family, void const* in)
  	{
  		if (address_family == AF_INET6) return inaddr6_to_address(in);
  		else return inaddr_to_address(in);
  	}
  
  	bool parse_route(int s, nlmsghdr* nl_hdr, ip_route* rt_info)
  	{
  		rtmsg* rt_msg = reinterpret_cast<rtmsg*>(NLMSG_DATA(nl_hdr));
  
  		if (!valid_addr_family(rt_msg->rtm_family) || (rt_msg->rtm_table != RT_TABLE_MAIN
  			&& rt_msg->rtm_table != RT_TABLE_LOCAL))
  			return false;
  
  		// make sure the defaults have the right address family
  		// in case the attributes are not present
  		if (rt_msg->rtm_family == AF_INET6)
  		{
  			rt_info->gateway = address_v6();
  			rt_info->destination = address_v6();
  		}
  
  		int if_index = 0;
  		auto rt_len = RTM_PAYLOAD(nl_hdr);
  #ifdef __clang__
  #pragma clang diagnostic push
  #pragma clang diagnostic ignored "-Wcast-align"
  #endif
  		for (rtattr* rt_attr = reinterpret_cast<rtattr*>(RTM_RTA(rt_msg));
  			RTA_OK(rt_attr, rt_len); rt_attr = RTA_NEXT(rt_attr, rt_len))
  		{
  			switch(rt_attr->rta_type)
  			{
  				case RTA_OIF:
  					if_index = *reinterpret_cast<int*>(RTA_DATA(rt_attr));
  					break;
  				case RTA_GATEWAY:
  					rt_info->gateway = to_address(rt_msg->rtm_family, RTA_DATA(rt_attr));
  					break;
  				case RTA_DST:
  					rt_info->destination = to_address(rt_msg->rtm_family, RTA_DATA(rt_attr));
  					break;
  			}
  		}
  #ifdef __clang__
  #pragma clang diagnostic pop
  #endif
  
  		if (rt_info->gateway.is_v6() && rt_info->gateway.to_v6().is_link_local())
  		{
  			address_v6 gateway6 = rt_info->gateway.to_v6();
  			gateway6.scope_id(std::uint32_t(if_index));
  			rt_info->gateway = gateway6;
  		}
  
  		ifreq req = {};
  		::if_indextoname(std::uint32_t(if_index), req.ifr_name);
  		static_assert(sizeof(rt_info->name) >= sizeof(req.ifr_name), "ip_route::name is too small");
  		std::memcpy(rt_info->name, req.ifr_name, sizeof(req.ifr_name));
  		::ioctl(s, ::siocgifmtu, &req);
  		rt_info->mtu = req.ifr_mtu;
  		rt_info->netmask = build_netmask(rt_msg->rtm_dst_len, rt_msg->rtm_family);
  		return true;
  	}
  
  	bool parse_nl_address(nlmsghdr* nl_hdr, ip_interface* ip_info)
  	{
  		ifaddrmsg* addr_msg = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(nl_hdr));
  
  		if (!valid_addr_family(addr_msg->ifa_family))
  			return false;
  
  		ip_info->preferred = (addr_msg->ifa_flags & (IFA_F_DADFAILED | IFA_F_DEPRECATED | IFA_F_TENTATIVE)) == 0;
  		ip_info->netmask = build_netmask(addr_msg->ifa_prefixlen, addr_msg->ifa_family);
  
  		ip_info->interface_address = address();
  		int rt_len = int(IFA_PAYLOAD(nl_hdr));
  #ifdef __clang__
  #pragma clang diagnostic push
  #pragma clang diagnostic ignored "-Wcast-align"
  #endif
  		for (rtattr* rt_attr = reinterpret_cast<rtattr*>(IFA_RTA(addr_msg));
  			RTA_OK(rt_attr, rt_len); rt_attr = RTA_NEXT(rt_attr, rt_len))
  		{
  			switch(rt_attr->rta_type)
  			{
  			case IFA_ADDRESS:
  				// if this is a point-to-point link then IFA_LOCAL holds
  				// the local address while IFA_ADDRESS is the destination
  				// don't overwrite the former with the latter
  				if (!ip_info->interface_address.is_unspecified())
  					break;
  				BOOST_FALLTHROUGH;
  			case IFA_LOCAL:
  				if (addr_msg->ifa_family == AF_INET6)
  				{
  					address_v6 addr = inaddr6_to_address(RTA_DATA(rt_attr));
  					if (addr_msg->ifa_scope == RT_SCOPE_LINK)
  						addr.scope_id(addr_msg->ifa_index);
  					ip_info->interface_address = addr;
  				}
  				else
  				{
  					ip_info->interface_address = inaddr_to_address(RTA_DATA(rt_attr));
  				}
  				break;
  			}
  		}
  #ifdef __clang__
  #pragma clang diagnostic pop
  #endif
  
  		static_assert(sizeof(ip_info->name) >= IF_NAMESIZE, "not enough space in ip_interface::name");
  		if_indextoname(addr_msg->ifa_index, ip_info->name);
  		return true;
  	}
  #endif // TORRENT_USE_NETLINK
  #endif // !BUILD_SIMULATOR
  
  #if TORRENT_USE_SYSCTL && !defined TORRENT_BUILD_SIMULATOR
  #ifdef TORRENT_OS2
  int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldlenp, void *newp, size_t newlen);
  #endif
  
  	bool parse_route(int, rt_msghdr* rtm, ip_route* rt_info)
  	{
  		sockaddr* rti_info[RTAX_MAX];
  		auto* sa = reinterpret_cast<sockaddr*>(rtm + 1);
  		for (int i = 0; i < RTAX_MAX; ++i)
  		{
  			if ((rtm->rtm_addrs & (1 << i)) == 0)
  			{
  				rti_info[i] = nullptr;
  				continue;
  			}
  			rti_info[i] = sa;
  
  #define ROUNDUP(a) \
  	((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
  
  			sa = reinterpret_cast<sockaddr*>(reinterpret_cast<char*>(sa) + ROUNDUP(sa->sa_len));
  
  #undef ROUNDUP
  		}
  
  		sa = rti_info[RTAX_GATEWAY];
  		if (sa == nullptr
  			|| rti_info[RTAX_DST] == nullptr
  			|| rti_info[RTAX_NETMASK] == nullptr
  			|| !valid_addr_family(sa->sa_family))
  			return false;
  
  		rt_info->gateway = sockaddr_to_address(rti_info[RTAX_GATEWAY]);
  		rt_info->destination = sockaddr_to_address(rti_info[RTAX_DST]);
  		rt_info->netmask = sockaddr_to_address(rti_info[RTAX_NETMASK]
  			, rt_info->destination.is_v4() ? AF_INET : AF_INET6);
  		if_indextoname(rtm->rtm_index, rt_info->name);
  		return true;
  	}
  #endif
  
  #if TORRENT_USE_IFADDRS && !defined TORRENT_BUILD_SIMULATOR
  	bool iface_from_ifaddrs(ifaddrs *ifa, ip_interface &rv)
  	{
  		if (!valid_addr_family(ifa->ifa_addr->sa_family))
  		{
  			return false;
  		}
  
  		std::strncpy(rv.name, ifa->ifa_name, sizeof(rv.name));
  		rv.name[sizeof(rv.name) - 1] = '\0';
  
  		// determine address
  		rv.interface_address = sockaddr_to_address(ifa->ifa_addr);
  		// determine netmask
  		if (ifa->ifa_netmask != nullptr)
  		{
  			rv.netmask = sockaddr_to_address(ifa->ifa_netmask);
  		}
  		return true;
  	}
  #endif
  
  	void build_netmask_impl(span<unsigned char> mask, int prefix_bits)
  	{
  		TORRENT_ASSERT(prefix_bits <= mask.size() * 8);
  		int i = 0;
  		while (prefix_bits >= 8)
  		{
  			mask[i] = 0xff;
  			prefix_bits -= 8;
  			++i;
  		}
  		if (i < mask.size())
  		{
  			mask[i] = (0xff << (8 - prefix_bits)) & 0xff;
  			++i;
  			while (i < mask.size())
  			{
  				mask[i] = 0;
  				++i;
  			}
  		}
  	}
  
  } // <anonymous>
  
  	address build_netmask(int prefix_bits, int const family)
  	{
  		if (family == AF_INET)
  		{
  			address_v4::bytes_type b;
  			build_netmask_impl(b, prefix_bits);
  			return address_v4(b);
  		}
  		else if (family == AF_INET6)
  		{
  			address_v6::bytes_type b;
  			build_netmask_impl(b, prefix_bits);
  			return address_v6(b);
  		}
  		return {};
  	}
  
  	// return (a1 & mask) == (a2 & mask)
  	bool match_addr_mask(address const& a1, address const& a2, address const& mask)
  	{
  		// all 3 addresses needs to belong to the same family
  		if (a1.is_v4() != a2.is_v4()) return false;
  		if (a1.is_v4() != mask.is_v4()) return false;
  
  		if (a1.is_v6())
  		{
  			address_v6::bytes_type b1 = a1.to_v6().to_bytes();
  			address_v6::bytes_type b2 = a2.to_v6().to_bytes();
  			address_v6::bytes_type m = mask.to_v6().to_bytes();
  			for (std::size_t i = 0; i < b1.size(); ++i)
  			{
  				b1[i] &= m[i];
  				b2[i] &= m[i];
  			}
  			return b1 == b2;
  		}
  		return (a1.to_v4().to_ulong() & mask.to_v4().to_ulong())
  			== (a2.to_v4().to_ulong() & mask.to_v4().to_ulong());
  	}
  
  	bool in_local_network(io_service& ios, address const& addr, error_code& ec)
  	{
  		std::vector<ip_interface> net = enum_net_interfaces(ios, ec);
  		if (ec) return false;
  		return in_local_network(net, addr);
  	}
  
  	bool in_local_network(std::vector<ip_interface> const& net, address const& addr)
  	{
  		return std::any_of(net.begin(), net.end(), [&addr](ip_interface const& i)
  			{ return match_addr_mask(addr, i.interface_address, i.netmask); });
  	}
  
  	std::vector<ip_interface> enum_net_interfaces(io_service& ios, error_code& ec)
  	{
  		TORRENT_UNUSED(ios); // this may be unused depending on configuration
  		std::vector<ip_interface> ret;
  		ec.clear();
  #if defined TORRENT_BUILD_SIMULATOR
  
  		std::vector<address> ips = ios.get_ips();
  
  		for (auto const& ip : ips)
  		{
  			ip_interface wan;
  			wan.interface_address = ip;
  			wan.netmask = address_v4::from_string("255.255.255.255");
  			std::strcpy(wan.name, "eth0");
  			std::strcpy(wan.friendly_name, "Ethernet");
  			std::strcpy(wan.description, "Simulator Ethernet Adapter");
  			ret.push_back(wan);
  		}
  #elif TORRENT_USE_NETLINK
  		int sock = ::socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
  		if (sock < 0)
  		{
  			ec = error_code(errno, system_category());
  			return ret;
  		}
  
  		char msg[NL_BUFSIZE] = {};
  		nlmsghdr* nl_msg = reinterpret_cast<nlmsghdr*>(msg);
  		int len = nl_dump_request(sock, RTM_GETADDR, 0, AF_PACKET, msg, sizeof(ifaddrmsg));
  		if (len < 0)
  		{
  			ec = error_code(errno, system_category());
  			::close(sock);
  			return ret;
  		}
  
  #ifdef __clang__
  #pragma clang diagnostic push
  #pragma clang diagnostic ignored "-Wcast-align"
  			// NLMSG_OK uses signed/unsigned compare in the same expression
  #pragma clang diagnostic ignored "-Wsign-compare"
  #endif
  		for (; NLMSG_OK(nl_msg, len); nl_msg = NLMSG_NEXT(nl_msg, len))
  		{
  			ip_interface iface;
  			if (parse_nl_address(nl_msg, &iface)) ret.push_back(iface);
  		}
  #ifdef __clang__
  #pragma clang diagnostic pop
  #endif
  
  		::close(sock);
  #elif TORRENT_USE_IFADDRS
  		int s = ::socket(AF_INET, SOCK_DGRAM, 0);
  		if (s < 0)
  		{
  			ec = error_code(errno, system_category());
  			return ret;
  		}
  
  		ifaddrs *ifaddr;
  		if (getifaddrs(&ifaddr) == -1)
  		{
  			ec = error_code(errno, system_category());
  			::close(s);
  			return ret;
  		}
  
  		for (ifaddrs* ifa = ifaddr; ifa != nullptr; ifa = ifa->ifa_next)
  		{
  			if (ifa->ifa_addr == nullptr) continue;
  			if ((ifa->ifa_flags & IFF_UP) == 0) continue;
  
  			if (valid_addr_family(ifa->ifa_addr->sa_family))
  			{
  				ip_interface iface;
  				if (iface_from_ifaddrs(ifa, iface))
  					ret.push_back(iface);
  			}
  		}
  		::close(s);
  		freeifaddrs(ifaddr);
  // MacOS X, BSD and solaris
  #elif TORRENT_USE_IFCONF
  		int s = ::socket(AF_INET, SOCK_DGRAM, 0);
  		if (s < 0)
  		{
  			ec = error_code(errno, system_category());
  			return ret;
  		}
  		ifconf ifc;
  		// make sure the buffer is aligned to hold ifreq structs
  		ifreq buf[40];
  		ifc.ifc_len = sizeof(buf);
  		ifc.ifc_buf = reinterpret_cast<char*>(buf);
  		if (ioctl(s, SIOCGIFCONF, &ifc) < 0)
  		{
  			ec = error_code(errno, system_category());
  			::close(s);
  			return ret;
  		}
  
  		char *ifr = reinterpret_cast<char*>(ifc.ifc_req);
  		int remaining = ifc.ifc_len;
  
  		while (remaining > 0)
  		{
  			ifreq const& item = *reinterpret_cast<ifreq*>(ifr);
  
  #ifdef _SIZEOF_ADDR_IFREQ
  			int current_size = _SIZEOF_ADDR_IFREQ(item);
  #elif defined TORRENT_BSD
  			int current_size = item.ifr_addr.sa_len + IFNAMSIZ;
  #else
  			int current_size = sizeof(ifreq);
  #endif
  
  			if (remaining < current_size) break;
  
  			if (valid_addr_family(item.ifr_addr.sa_family))
  			{
  				ip_interface iface;
  				iface.interface_address = sockaddr_to_address(&item.ifr_addr);
  				std::strncpy(iface.name, item.ifr_name, sizeof(iface.name));
  				iface.name[sizeof(iface.name) - 1] = '\0';
  
  				ifreq req = {};
  				std::strncpy(req.ifr_name, item.ifr_name, IF_NAMESIZE - 1);
  				if (ioctl(s, SIOCGIFNETMASK, &req) < 0)
  				{
  					if (iface.interface_address.is_v6())
  					{
  						// this is expected to fail (at least on MacOS X)
  						iface.netmask = address_v6::any();
  					}
  					else
  					{
  						ec = error_code(errno, system_category());
  						::close(s);
  						return ret;
  					}
  				}
  				else
  				{
  					iface.netmask = sockaddr_to_address(&req.ifr_addr, item.ifr_addr.sa_family);
  				}
  				ret.push_back(iface);
  			}
  
  			ifr += current_size;
  			remaining -= current_size;
  		}
  		::close(s);
  
  #elif TORRENT_USE_GETADAPTERSADDRESSES
  
  #if _WIN32_WINNT >= 0x0501
  		using GetAdaptersAddresses_t = ULONG (WINAPI *)(ULONG,ULONG,PVOID,PIP_ADAPTER_ADDRESSES,PULONG);
  		// Get GetAdaptersAddresses() pointer
  		auto GetAdaptersAddresses =
  			aux::get_library_procedure<aux::iphlpapi, GetAdaptersAddresses_t>("GetAdaptersAddresses");
  
  		if (GetAdaptersAddresses != nullptr)
  		{
  			ULONG buf_size = 10000;
  			std::vector<char> buffer(buf_size);
  			PIP_ADAPTER_ADDRESSES adapter_addresses
  				= reinterpret_cast<IP_ADAPTER_ADDRESSES*>(&buffer[0]);
  
  			DWORD res = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER
  				| GAA_FLAG_SKIP_ANYCAST, nullptr, adapter_addresses, &buf_size);
  			if (res == ERROR_BUFFER_OVERFLOW)
  			{
  				buffer.resize(buf_size);
  				adapter_addresses = reinterpret_cast<IP_ADAPTER_ADDRESSES*>(&buffer[0]);
  				res = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_DNS_SERVER
  					| GAA_FLAG_SKIP_ANYCAST, nullptr, adapter_addresses, &buf_size);
  			}
  			if (res != NO_ERROR)
  			{
  				ec = error_code(WSAGetLastError(), system_category());
  				return std::vector<ip_interface>();
  			}
  
  			for (PIP_ADAPTER_ADDRESSES adapter = adapter_addresses;
  				adapter != 0; adapter = adapter->Next)
  			{
  				ip_interface r;
  				std::strncpy(r.name, adapter->AdapterName, sizeof(r.name));
  				r.name[sizeof(r.name) - 1] = '\0';
  				wcstombs(r.friendly_name, adapter->FriendlyName, sizeof(r.friendly_name));
  				r.friendly_name[sizeof(r.friendly_name) - 1] = '\0';
  				wcstombs(r.description, adapter->Description, sizeof(r.description));
  				r.description[sizeof(r.description) - 1] = '\0';
  				for (IP_ADAPTER_UNICAST_ADDRESS* unicast = adapter->FirstUnicastAddress;
  					unicast; unicast = unicast->Next)
  				{
  					if (!valid_addr_family(unicast->Address.lpSockaddr->sa_family))
  						continue;
  					r.preferred = unicast->DadState == IpDadStatePreferred;
  					r.interface_address = sockaddr_to_address(unicast->Address.lpSockaddr);
  					ret.push_back(r);
  				}
  			}
  
  			return ret;
  		}
  #endif
  
  		SOCKET s = ::socket(AF_INET, SOCK_DGRAM, 0);
  		if (int(s) == SOCKET_ERROR)
  		{
  			ec = error_code(WSAGetLastError(), system_category());
  			return ret;
  		}
  
  		INTERFACE_INFO buffer[30];
  		DWORD size;
  
  		if (WSAIoctl(s, SIO_GET_INTERFACE_LIST, 0, 0, buffer,
  			sizeof(buffer), &size, 0, 0) != 0)
  		{
  			ec = error_code(WSAGetLastError(), system_category());
  			closesocket(s);
  			return ret;
  		}
  		closesocket(s);
  
  		int n = size / sizeof(INTERFACE_INFO);
  
  		for (int i = 0; i < n; ++i)
  		{
  			ip_interface iface;
  			iface.interface_address = sockaddr_to_address(&buffer[i].iiAddress.Address);
  			if (iface.interface_address == address_v4::any()) continue;
  			iface.netmask = sockaddr_to_address(&buffer[i].iiNetmask.Address
  				, iface.interface_address.is_v4() ? AF_INET : AF_INET6);
  			ret.push_back(iface);
  		}
  
  #else
  
  #ifdef _MSC_VER
  #pragma message ( "THIS OS IS NOT RECOGNIZED, enum_net_interfaces WILL PROBABLY NOT WORK" )
  #else
  #warning "THIS OS IS NOT RECOGNIZED, enum_net_interfaces WILL PROBABLY NOT WORK"
  #endif
  
  		// make a best guess of the interface we're using and its IP
  		udp::resolver r(ios);
  		udp::resolver::iterator i = r.resolve(udp::resolver::query(boost::asio::ip::host_name(ec), "0"), ec);
  		if (ec) return ret;
  		for (;i != udp::resolver::iterator(); ++i)
  		{
  			ip_interface iface;
  			iface.interface_address = i->endpoint().address();
  			if (iface.interface_address.is_v4())
  				iface.netmask = address_v4::netmask(iface.interface_address.to_v4());
  			ret.push_back(iface);
  		}
  #endif
  		return ret;
  	}
  
  	boost::optional<ip_route> get_default_route(io_service& ios
  		, string_view const device, bool const v6, error_code& ec)
  	{
  		std::vector<ip_route> const ret = enum_routes(ios, ec);
  		auto const i = std::find_if(ret.begin(), ret.end()
  			, [device,v6](ip_route const& r)
  		{
  			return r.destination.is_unspecified()
  				&& r.destination.is_v6() == v6
  				&& (device.empty() || r.name == device);
  		});
  		if (i == ret.end()) return boost::none;
  		return *i;
  	}
  
  	address get_default_gateway(io_service& ios
  		, string_view const device, bool const v6, error_code& ec)
  	{
  		auto const default_route = get_default_route(ios, device, v6, ec);
  		return default_route ? default_route->gateway : address();
  	}
  
  	std::vector<ip_route> enum_routes(io_service& ios, error_code& ec)
  	{
  		std::vector<ip_route> ret;
  		TORRENT_UNUSED(ios);
  		TORRENT_UNUSED(ec);
  
  #ifdef TORRENT_BUILD_SIMULATOR
  
  		TORRENT_UNUSED(ec);
  
  		std::vector<address> ips = ios.get_ips();
  
  		for (auto const& ip : ips)
  		{
  			ip_route r;
  			if (ip.is_v4())
  			{
  				r.destination = address_v4();
  				r.netmask = address_v4::from_string("255.255.255.0");
  				address_v4::bytes_type b = ip.to_v4().to_bytes();
  				b[3] = 1;
  				r.gateway = address_v4(b);
  			}
  			else
  			{
  				r.destination = address_v6();
  				r.netmask = address_v6::from_string("FFFF:FFFF:FFFF:FFFF::0");
  				address_v6::bytes_type b = ip.to_v6().to_bytes();
  				b[14] = 1;
  				r.gateway = address_v6(b);
  			}
  			std::strcpy(r.name, "eth0");
  			r.mtu = ios.sim().config().path_mtu(ip, ip);
  			ret.push_back(r);
  		}
  
  #elif TORRENT_USE_SYSCTL
  /*
  		struct rt_msg
  		{
  			rt_msghdr m_rtm;
  			char buf[512];
  		};
  
  		rt_msg m;
  		int len = sizeof(rt_msg);
  		bzero(&m, len);
  		m.m_rtm.rtm_type = RTM_GET;
  		m.m_rtm.rtm_flags = RTF_UP | RTF_GATEWAY;
  		m.m_rtm.rtm_version = RTM_VERSION;
  		m.m_rtm.rtm_addrs = RTA_DST | RTA_GATEWAY | RTA_NETMASK;
  		m.m_rtm.rtm_seq = 0;
  		m.m_rtm.rtm_msglen = len;
  
  		int s = ::socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
  		if (s == -1)
  		{
  			ec = error_code(errno, system_category());
  			return std::vector<ip_route>();
  		}
  
  		int n = write(s, &m, len);
  		if (n == -1)
  		{
  			ec = error_code(errno, system_category());
  			::close(s);
  			return std::vector<ip_route>();
  		}
  		else if (n != len)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			::close(s);
  			return std::vector<ip_route>();
  		}
  		bzero(&m, len);
  
  		n = read(s, &m, len);
  		if (n == -1)
  		{
  			ec = error_code(errno, system_category());
  			::close(s);
  			return std::vector<ip_route>();
  		}
  
  		for (rt_msghdr* ptr = &m.m_rtm; (char*)ptr < ((char*)&m.m_rtm) + n; ptr = (rt_msghdr*)(((char*)ptr) + ptr->rtm_msglen))
  		{
  			std::cout << " rtm_msglen: " << ptr->rtm_msglen << std::endl;
  			std::cout << " rtm_type: " << ptr->rtm_type << std::endl;
  			if (ptr->rtm_errno)
  			{
  				ec = error_code(ptr->rtm_errno, system_category());
  				return std::vector<ip_route>();
  			}
  			if (m.m_rtm.rtm_flags & RTF_UP == 0
  				|| m.m_rtm.rtm_flags & RTF_GATEWAY == 0)
  			{
  				ec = boost::asio::error::operation_not_supported;
  				return address_v4::any();
  			}
  			if (ptr->rtm_addrs & RTA_DST == 0
  				|| ptr->rtm_addrs & RTA_GATEWAY == 0
  				|| ptr->rtm_addrs & RTA_NETMASK == 0)
  			{
  				ec = boost::asio::error::operation_not_supported;
  				return std::vector<ip_route>();
  			}
  			if (ptr->rtm_msglen > len - ((char*)ptr - ((char*)&m.m_rtm)))
  			{
  				ec = boost::asio::error::operation_not_supported;
  				return std::vector<ip_route>();
  			}
  			int min_len = sizeof(rt_msghdr) + 2 * sizeof(sockaddr_in);
  			if (m.m_rtm.rtm_msglen < min_len)
  			{
  				ec = boost::asio::error::operation_not_supported;
  				return std::vector<ip_route>();
  			}
  
  			ip_route r;
  			// destination
  			char* p = m.buf;
  			sockaddr_in* sin = (sockaddr_in*)p;
  			r.destination = sockaddr_to_address((sockaddr*)p);
  
  			// gateway
  			p += sin->sin_len;
  			sin = (sockaddr_in*)p;
  			r.gateway = sockaddr_to_address((sockaddr*)p);
  
  			// netmask
  			p += sin->sin_len;
  			sin = (sockaddr_in*)p;
  			r.netmask = sockaddr_to_address((sockaddr*)p);
  			ret.push_back(r);
  		}
  		::close(s);
  */
  	int mib[6] = {CTL_NET, PF_ROUTE, 0, AF_UNSPEC, NET_RT_DUMP, 0};
  
  	std::size_t needed = 0;
  #ifdef TORRENT_OS2
  	if (__libsocket_sysctl(mib, 6, 0, &needed, 0, 0) < 0)
  #else
  	if (sysctl(mib, 6, nullptr, &needed, nullptr, 0) < 0)
  #endif
  	{
  		ec = error_code(errno, system_category());
  		return std::vector<ip_route>();
  	}
  
  	if (needed == 0)
  	{
  		return std::vector<ip_route>();
  	}
  
  	std::unique_ptr<char[]> buf(new (std::nothrow) char[needed]);
  	if (buf == nullptr)
  	{
  		ec = boost::asio::error::no_memory;
  		return std::vector<ip_route>();
  	}
  
  #ifdef TORRENT_OS2
  	if (__libsocket_sysctl(mib, 6, buf.get(), &needed, 0, 0) < 0)
  #else
  	if (sysctl(mib, 6, buf.get(), &needed, nullptr, 0) < 0)
  #endif
  	{
  		ec = error_code(errno, system_category());
  		return std::vector<ip_route>();
  	}
  
  	char* end = buf.get() + needed;
  
  	int s = ::socket(AF_INET, SOCK_DGRAM, 0);
  	if (s < 0)
  	{
  		ec = error_code(errno, system_category());
  		return std::vector<ip_route>();
  	}
  	rt_msghdr* rtm;
  	for (char* next = buf.get(); next < end; next += rtm->rtm_msglen)
  	{
  		rtm = reinterpret_cast<rt_msghdr*>(next);
  		if (rtm->rtm_version != RTM_VERSION
  			|| (rtm->rtm_type != RTM_ADD
  			&& rtm->rtm_type != RTM_GET))
  		{
  			continue;
  		}
  
  		ip_route r;
  		if (parse_route(s, rtm, &r)) ret.push_back(r);
  	}
  	::close(s);
  
  #elif TORRENT_USE_GETIPFORWARDTABLE
  /*
  	move this to enum_net_interfaces
  		// Get GetAdaptersInfo() pointer
  		using GetAdaptersInfo_t = DWORD (WINAPI*)(PIP_ADAPTER_INFO, PULONG);
  		GetAdaptersInfo_t GetAdaptersInfo = get_library_procedure<iphlpapi, GetAdaptersInfo_t>("GetAdaptersInfo");
  		if (GetAdaptersInfo == nullptr)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			return std::vector<ip_route>();
  		}
  
  		PIP_ADAPTER_INFO adapter_info = 0;
  		ULONG out_buf_size = 0;
  		if (GetAdaptersInfo(adapter_info, &out_buf_size) != ERROR_BUFFER_OVERFLOW)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			return std::vector<ip_route>();
  		}
  
  		adapter_info = (IP_ADAPTER_INFO*)malloc(out_buf_size);
  		if (!adapter_info)
  		{
  			ec = boost::asio::error::no_memory;
  			return std::vector<ip_route>();
  		}
  
  		if (GetAdaptersInfo(adapter_info, &out_buf_size) == NO_ERROR)
  		{
  			for (PIP_ADAPTER_INFO adapter = adapter_info;
  				adapter != 0; adapter = adapter->Next)
  			{
  
  				ip_route r;
  				r.destination = address::from_string(adapter->IpAddressList.IpAddress.String, ec);
  				r.gateway = address::from_string(adapter->GatewayList.IpAddress.String, ec);
  				r.netmask = address::from_string(adapter->IpAddressList.IpMask.String, ec);
  				strncpy(r.name, adapter->AdapterName, sizeof(r.name));
  
  				if (ec)
  				{
  					ec = error_code();
  					continue;
  				}
  				ret.push_back(r);
  			}
  		}
  
  		// Free memory
  		free(adapter_info);
  */
  
  		using GetIfEntry_t = DWORD (WINAPI *)(PMIB_IFROW pIfRow);
  		auto GetIfEntry = aux::get_library_procedure<aux::iphlpapi, GetIfEntry_t>(
  			"GetIfEntry");
  
  		if (GetIfEntry == nullptr)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			return std::vector<ip_route>();
  		}
  
  #if _WIN32_WINNT >= 0x0600
  		using GetIpForwardTable2_t = DWORD (WINAPI *)(
  			ADDRESS_FAMILY, PMIB_IPFORWARD_TABLE2*);
  		using FreeMibTable_t = void (WINAPI *)(PVOID Memory);
  
  		auto GetIpForwardTable2 = aux::get_library_procedure<aux::iphlpapi, GetIpForwardTable2_t>("GetIpForwardTable2");
  		auto FreeMibTable = aux::get_library_procedure<aux::iphlpapi, FreeMibTable_t>("FreeMibTable");
  		if (GetIpForwardTable2 != nullptr && FreeMibTable != nullptr)
  		{
  			MIB_IPFORWARD_TABLE2* routes = nullptr;
  			int res = GetIpForwardTable2(AF_UNSPEC, &routes);
  			if (res == NO_ERROR)
  			{
  				for (int i = 0; i < int(routes->NumEntries); ++i)
  				{
  					ip_route r;
  					r.gateway = sockaddr_to_address((const sockaddr*)&routes->Table[i].NextHop);
  					// The scope_id in NextHop is always zero because that would make
  					// things too easy apparently
  					if (r.gateway.is_v6() && r.gateway.to_v6().is_link_local())
  					{
  						address_v6 gateway6 = r.gateway.to_v6();
  						gateway6.scope_id(routes->Table[i].InterfaceIndex);
  						r.gateway = gateway6;
  					}
  					r.destination = sockaddr_to_address(
  						(const sockaddr*)&routes->Table[i].DestinationPrefix.Prefix);
  					r.netmask = build_netmask(routes->Table[i].DestinationPrefix.PrefixLength
  						, routes->Table[i].DestinationPrefix.Prefix.si_family);
  					MIB_IFROW ifentry;
  					ifentry.dwIndex = routes->Table[i].InterfaceIndex;
  					if (GetIfEntry(&ifentry) == NO_ERROR)
  					{
  						WCHAR* name = ifentry.wszName;
  						// strip UNC prefix to match the names returned by enum_net_interfaces
  						if (wcsncmp(name, L"\\DEVICE\\TCPIP_", wcslen(L"\\DEVICE\\TCPIP_")) == 0)
  						{
  							name += wcslen(L"\\DEVICE\\TCPIP_");
  						}
  						wcstombs(r.name, name, sizeof(r.name));
  						r.name[sizeof(r.name) - 1] = 0;
  						r.mtu = ifentry.dwMtu;
  						ret.push_back(r);
  					}
  				}
  			}
  			if (routes) FreeMibTable(routes);
  			return ret;
  		}
  #endif
  
  		// Get GetIpForwardTable() pointer
  		using GetIpForwardTable_t = DWORD (WINAPI*)(PMIB_IPFORWARDTABLE pIpForwardTable,PULONG pdwSize,BOOL bOrder);
  
  		auto GetIpForwardTable = aux::get_library_procedure<aux::iphlpapi, GetIpForwardTable_t>("GetIpForwardTable");
  		if (GetIpForwardTable == nullptr)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			return std::vector<ip_route>();
  		}
  
  		MIB_IPFORWARDTABLE* routes = nullptr;
  		ULONG out_buf_size = 0;
  		if (GetIpForwardTable(routes, &out_buf_size, FALSE) != ERROR_INSUFFICIENT_BUFFER)
  		{
  			ec = boost::asio::error::operation_not_supported;
  			return std::vector<ip_route>();
  		}
  
  		routes = (MIB_IPFORWARDTABLE*)malloc(out_buf_size);
  		if (!routes)
  		{
  			ec = boost::asio::error::no_memory;
  			return std::vector<ip_route>();
  		}
  
  		if (GetIpForwardTable(routes, &out_buf_size, FALSE) == NO_ERROR)
  		{
  			for (int i = 0; i < int(routes->dwNumEntries); ++i)
  			{
  				ip_route r;
  				r.destination = inaddr_to_address(&routes->table[i].dwForwardDest);
  				r.netmask = inaddr_to_address(&routes->table[i].dwForwardMask);
  				r.gateway = inaddr_to_address(&routes->table[i].dwForwardNextHop);
  				MIB_IFROW ifentry;
  				ifentry.dwIndex = routes->table[i].dwForwardIfIndex;
  				if (GetIfEntry(&ifentry) == NO_ERROR)
  				{
  					wcstombs(r.name, ifentry.wszName, sizeof(r.name));
  					r.name[sizeof(r.name) - 1] = 0;
  					r.mtu = ifentry.dwMtu;
  					ret.push_back(r);
  				}
  			}
  		}
  
  		// Free memory
  		free(routes);
  #elif TORRENT_USE_NETLINK
  		int sock = ::socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
  		if (sock < 0)
  		{
  			ec = error_code(errno, system_category());
  			return std::vector<ip_route>();
  		}
  
  		std::uint32_t seq = 0;
  
  		char msg[NL_BUFSIZE] = {};
  		nlmsghdr* nl_msg = reinterpret_cast<nlmsghdr*>(msg);
  		int len = nl_dump_request(sock, RTM_GETROUTE, seq++, AF_UNSPEC, msg, sizeof(rtmsg));
  		if (len < 0)
  		{
  			ec = error_code(errno, system_category());
  			::close(sock);
  			return std::vector<ip_route>();
  		}
  
  		close(sock);
  		sock = ::socket(AF_INET, SOCK_DGRAM, 0);
  		if (sock < 0)
  		{
  			ec = error_code(errno, system_category());
  			return std::vector<ip_route>();
  		}
  #ifdef __clang__
  #pragma clang diagnostic push
  #pragma clang diagnostic ignored "-Wcast-align"
  // NLMSG_OK uses signed/unsigned compare in the same expression
  #pragma clang diagnostic ignored "-Wsign-compare"
  #endif
  		for (; NLMSG_OK(nl_msg, len); nl_msg = NLMSG_NEXT(nl_msg, len))
  		{
  			ip_route r;
  			if (parse_route(sock, nl_msg, &r)) ret.push_back(r);
  		}
  #ifdef __clang__
  #pragma clang diagnostic pop
  #endif
  		::close(sock);
  
  #endif
  		return ret;
  	}
  
  	// returns the device name whose local address is ``addr``. If
  	// no such device is found, an empty string is returned.
  	std::string device_for_address(address addr, io_service& ios, error_code& ec)
  	{
  		std::vector<ip_interface> ifs = enum_net_interfaces(ios, ec);
  		if (ec) return {};
  
  		auto const iter = std::find_if(ifs.begin(), ifs.end()
  			, [&addr](ip_interface const& iface)
  			{ return iface.interface_address == addr; });
  		return (iter == ifs.end()) ? std::string() : iter->name;
  	}
  }
  