/*

Copyright (c) 2007-2008, 2010, 2014-2021, Arvid Norberg
Copyright (c) 2016-2018, Alden Torres
Copyright (c) 2017, Steven Siloti
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.

*/

#ifndef TORRENT_ENUM_NET_HPP_INCLUDED
#define TORRENT_ENUM_NET_HPP_INCLUDED

#include "libtorrent/config.hpp"

#include "libtorrent/aux_/disable_warnings_push.hpp"

#if TORRENT_USE_IFCONF || TORRENT_USE_NETLINK || TORRENT_USE_SYSCTL
#include <sys/socket.h> // for SO_BINDTODEVICE
#endif

#include <boost/optional.hpp>

#include "libtorrent/aux_/disable_warnings_pop.hpp"

#include "libtorrent/io_context.hpp"
#include "libtorrent/address.hpp"
#include "libtorrent/error_code.hpp"
#include "libtorrent/socket.hpp"
#include "libtorrent/aux_/bind_to_device.hpp"
#include "libtorrent/span.hpp"
#include "libtorrent/flags.hpp"

#include <vector>

namespace libtorrent {

	// internal
using interface_flags = flags::bitfield_flag<std::uint32_t, struct interface_flags_tag>;

namespace if_flags {

	// internal
	constexpr interface_flags up = 0_bit;
	constexpr interface_flags broadcast = 1_bit;
	constexpr interface_flags loopback = 2_bit;
	constexpr interface_flags pointopoint = 3_bit;
	constexpr interface_flags running = 4_bit;
	constexpr interface_flags noarp = 5_bit;
	constexpr interface_flags promisc = 6_bit;
	constexpr interface_flags allmulti = 7_bit;
	constexpr interface_flags master = 8_bit;
	constexpr interface_flags slave = 9_bit;
	constexpr interface_flags multicast = 10_bit;
	constexpr interface_flags dynamic = 11_bit;
	constexpr interface_flags lower_up = 12_bit;
	constexpr interface_flags dormant = 13_bit;
}

// internal
enum class if_state : std::uint8_t {

	up,
	dormant,
	lowerlayerdown,
	down,
	notpresent,
	testing,
	unknown
};

// internal
	struct ip_interface
	{
		address interface_address;
		address netmask;
		char name[64]{};
		char friendly_name[128]{};
		char description[128]{};
		// an interface is preferred if its address is
		// not tentative/duplicate/deprecated
		bool preferred = true;

		interface_flags flags = if_flags::up;
		if_state state = if_state::unknown;
	};

// internal
	struct ip_route
	{
		address destination;
		address netmask;
		address gateway;
		address source_hint;
		char name[64]{};
		int mtu = 0;
	};

	// returns a list of the configured IP interfaces
	// on the machine
	TORRENT_EXTRA_EXPORT std::vector<ip_interface> enum_net_interfaces(io_context& ios
		, error_code& ec);

	TORRENT_EXTRA_EXPORT std::vector<ip_route> enum_routes(io_context& ios
		, error_code& ec);

	// returns AF_INET or AF_INET6, depending on the address' family
	TORRENT_EXTRA_EXPORT int family(address const& a);

	// return (a1 & mask) == (a2 & mask)
	TORRENT_EXTRA_EXPORT bool match_addr_mask(address const& a1
		, address const& a2, address const& mask);

	// return a netmask with the specified address family and the specified
	// number of prefix bit set, of the most significant bits in the resulting
	// netmask
	TORRENT_EXTRA_EXPORT address build_netmask(int bits, int family);

	// return the gateway for the given ip_interface, if there is one. Otherwise
	// return nullopt.
	TORRENT_EXTRA_EXPORT boost::optional<address> get_gateway(
		ip_interface const& iface, span<ip_route const> routes);

	// returns whether there is a route to the specified device for for any global
	// internet address of the specified address family.
	TORRENT_EXTRA_EXPORT bool has_internet_route(string_view device, int family
		, span<ip_route const> routes);

	// returns whether there are *any* routes to the internet in the routing
	// table. This can be used to determine if the routing table is fully
	// populated or not.
	TORRENT_EXTRA_EXPORT bool has_any_internet_route(span<ip_route const> routes);

	// attempt to bind socket to the device with the specified name. For systems
	// that don't support SO_BINDTODEVICE the socket will be bound to one of the
	// IP addresses of the specified device. In this case it is necessary to
	// verify the local endpoint of the socket once the connection is established.
	// the returned address is the ip the socket was bound to (or address_v4::any()
	// in case SO_BINDTODEVICE succeeded and we don't need to verify it).
	// TODO: 3 use string_view for device_name
	template <class Socket>
	address bind_socket_to_device(io_context& ios, Socket& sock
		, tcp const& protocol
		, char const* device_name, int port, error_code& ec)
	{
		tcp::endpoint bind_ep(address_v4::any(), std::uint16_t(port));

		address ip = make_address(device_name, ec);
		if (!ec)
		{
			// this is to cover the case where "0.0.0.0" is considered any IPv4 or
			// IPv6 address. If we're asking to be bound to an IPv6 address and
			// providing 0.0.0.0 as the device, turn it into "::"
			if (ip == address_v4::any() && protocol == boost::asio::ip::tcp::v6())
				ip = address_v6::any();
			bind_ep.address(ip);
			// it appears to be an IP. Just bind to that address
			sock.bind(bind_ep, ec);
			return bind_ep.address();
		}

		ec.clear();

#if TORRENT_HAS_BINDTODEVICE
		// try to use SO_BINDTODEVICE here, if that exists. If it fails,
		// fall back to the mechanism we have below
		aux::bind_device(sock, device_name, ec);
		if (ec)
#endif
		{
			ec.clear();
			// TODO: 2 this could be done more efficiently by just looking up
			// the interface with the given name, maybe even with if_nametoindex()
			std::vector<ip_interface> ifs = enum_net_interfaces(ios, ec);
			if (ec) return bind_ep.address();

			bool found = false;

			for (auto const& iface : ifs)
			{
				// we're looking for a specific interface, and its address
				// (which must be of the same family as the address we're
				// connecting to)
				if (std::strcmp(iface.name, device_name) != 0) continue;
				if (iface.interface_address.is_v4() != (protocol == boost::asio::ip::tcp::v4()))
					continue;

				bind_ep.address(iface.interface_address);
				found = true;
				break;
			}

			if (!found)
			{
				ec = error_code(boost::system::errc::no_such_device, generic_category());
				return bind_ep.address();
			}
		}
		sock.bind(bind_ep, ec);
		return bind_ep.address();
	}

	// returns the device name whose local address is ``addr``. If
	// no such device is found, an empty string is returned.
	TORRENT_EXTRA_EXPORT std::string device_for_address(address addr
		, io_context& ios, error_code& ec);

}

#endif