monero/contrib/epee/src/net_helper.cpp

#include "net/net_helper.h"

namespace epee
{
namespace net_utils
{
	boost::unique_future<boost::asio::ip::tcp::socket>
	direct_connect::operator()(const std::string& addr, const std::string& port, boost::asio::steady_timer& timeout) const
	{
		// Get a list of endpoints corresponding to the server name.
		//////////////////////////////////////////////////////////////////////////
		boost::asio::ip::tcp::resolver resolver(GET_IO_SERVICE(timeout));
		boost::asio::ip::tcp::resolver::query query(boost::asio::ip::tcp::v4(), addr, port, boost::asio::ip::tcp::resolver::query::canonical_name);

		bool try_ipv6 = false;
		boost::asio::ip::tcp::resolver::iterator iterator;
		boost::asio::ip::tcp::resolver::iterator end;
		boost::system::error_code resolve_error;
		try
		{
			iterator = resolver.resolve(query, resolve_error);
			if(iterator == end) // Documentation states that successful call is guaranteed to be non-empty
			{
				// if IPv4 resolution fails, try IPv6.  Unintentional outgoing IPv6 connections should only
				// be possible if for some reason a hostname was given and that hostname fails IPv4 resolution,
				// so at least for now there should not be a need for a flag "using ipv6 is ok"
				try_ipv6 = true;
			}

		}
		catch (const boost::system::system_error& e)
		{
			if (resolve_error != boost::asio::error::host_not_found &&
					resolve_error != boost::asio::error::host_not_found_try_again)
			{
				throw;
			}
			try_ipv6 = true;
		}
		if (try_ipv6)
		{
			boost::asio::ip::tcp::resolver::query query6(boost::asio::ip::tcp::v6(), addr, port, boost::asio::ip::tcp::resolver::query::canonical_name);
			iterator = resolver.resolve(query6);
			if (iterator == end)
				throw boost::system::system_error{boost::asio::error::fault, "Failed to resolve " + addr};
		}

		//////////////////////////////////////////////////////////////////////////

		struct new_connection
		{
			boost::promise<boost::asio::ip::tcp::socket> result_;
			boost::asio::ip::tcp::socket socket_;

			explicit new_connection(boost::asio::io_service& io_service)
			  : result_(), socket_(io_service)
			{}
		};

		const auto shared = std::make_shared<new_connection>(GET_IO_SERVICE(timeout));
		timeout.async_wait([shared] (boost::system::error_code error)
		{
			if (error != boost::system::errc::operation_canceled && shared && shared->socket_.is_open())
			{
				shared->socket_.shutdown(boost::asio::ip::tcp::socket::shutdown_both);
				shared->socket_.close();
			}
		});
		shared->socket_.async_connect(*iterator, [shared] (boost::system::error_code error)
		{
			if (shared)
			{
				if (error)
					shared->result_.set_exception(boost::system::system_error{error});
				else
					shared->result_.set_value(std::move(shared->socket_));
			}
		});
		return shared->result_.get_future();
	}
}
}