i2pd/libi2pd_client/I2PTunnel.cpp

/*
* Copyright (c) 2013-2020, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/

#include <cassert>
#include "Base.h"
#include "Log.h"
#include "Destination.h"
#include "ClientContext.h"
#include "I2PTunnel.h"

namespace i2p
{
namespace client
{

	/** set standard socket options */
	static void I2PTunnelSetSocketOptions(std::shared_ptr<boost::asio::ip::tcp::socket> socket)
	{
		if (socket && socket->is_open())
		{
			boost::asio::socket_base::receive_buffer_size option(I2P_TUNNEL_CONNECTION_BUFFER_SIZE);
			socket->set_option(option);
		}
	}

	I2PTunnelConnection::I2PTunnelConnection (I2PService * owner, std::shared_ptr<boost::asio::ip::tcp::socket> socket,
		std::shared_ptr<const i2p::data::LeaseSet> leaseSet, int port):
		I2PServiceHandler(owner), m_Socket (socket), m_RemoteEndpoint (socket->remote_endpoint ()),
		m_IsQuiet (true)
	{
		m_Stream = GetOwner()->GetLocalDestination ()->CreateStream (leaseSet, port);
	}

	I2PTunnelConnection::I2PTunnelConnection (I2PService * owner,
		std::shared_ptr<boost::asio::ip::tcp::socket> socket, std::shared_ptr<i2p::stream::Stream> stream):
		I2PServiceHandler(owner), m_Socket (socket), m_Stream (stream),
		m_RemoteEndpoint (socket->remote_endpoint ()), m_IsQuiet (true)
	{
	}

	I2PTunnelConnection::I2PTunnelConnection (I2PService * owner, std::shared_ptr<i2p::stream::Stream> stream,
		std::shared_ptr<boost::asio::ip::tcp::socket> socket, const boost::asio::ip::tcp::endpoint& target, bool quiet):
		I2PServiceHandler(owner), m_Socket (socket), m_Stream (stream),
		m_RemoteEndpoint (target), m_IsQuiet (quiet)
	{
	}

	I2PTunnelConnection::~I2PTunnelConnection ()
	{
	}

	void I2PTunnelConnection::I2PConnect (const uint8_t * msg, size_t len)
	{
		if (m_Stream)
		{
			if (msg)
				m_Stream->Send (msg, len); // connect and send
			else
				m_Stream->Send (m_Buffer, 0); // connect
		}
		StreamReceive ();
		Receive ();
	}

	static boost::asio::ip::address GetLoopbackAddressFor(const i2p::data::IdentHash & addr)
	{
		boost::asio::ip::address_v4::bytes_type bytes;
		const uint8_t * ident = addr;
		bytes[0] = 127;
		memcpy (bytes.data ()+1, ident, 3);
		boost::asio::ip::address ourIP = boost::asio::ip::address_v4 (bytes);
		return ourIP;
	}

#ifdef __linux__
	static void MapToLoopback(const std::shared_ptr<boost::asio::ip::tcp::socket> & sock, const i2p::data::IdentHash & addr)
	{
		// bind to 127.x.x.x address
		// where x.x.x are first three bytes from ident
		auto ourIP = GetLoopbackAddressFor(addr);
		sock->bind (boost::asio::ip::tcp::endpoint (ourIP, 0));
	}
#endif

	void I2PTunnelConnection::Connect (bool isUniqueLocal)
	{
		I2PTunnelSetSocketOptions(m_Socket);
		if (m_Socket)
		{
#ifdef __linux__
			if (isUniqueLocal && m_RemoteEndpoint.address ().is_v4 () &&
				m_RemoteEndpoint.address ().to_v4 ().to_bytes ()[0] == 127)
			{
				m_Socket->open (boost::asio::ip::tcp::v4 ());
				auto ident = m_Stream->GetRemoteIdentity()->GetIdentHash();
				MapToLoopback(m_Socket, ident);
			}
#endif
			m_Socket->async_connect (m_RemoteEndpoint, std::bind (&I2PTunnelConnection::HandleConnect,
				shared_from_this (), std::placeholders::_1));
		}
	}

	void I2PTunnelConnection::Terminate ()
	{
		if (Kill()) return;
		if (m_Stream)
		{
			m_Stream->Close ();
			m_Stream.reset ();
		}
		boost::system::error_code ec;
		m_Socket->shutdown(boost::asio::ip::tcp::socket::shutdown_send, ec); // avoid RST
		m_Socket->close ();

		Done(shared_from_this ());
	}

	void I2PTunnelConnection::Receive ()
	{
		m_Socket->async_read_some (boost::asio::buffer(m_Buffer, I2P_TUNNEL_CONNECTION_BUFFER_SIZE),
			std::bind(&I2PTunnelConnection::HandleReceived, shared_from_this (),
			std::placeholders::_1, std::placeholders::_2));
	}

	void I2PTunnelConnection::HandleReceived (const boost::system::error_code& ecode, std::size_t bytes_transferred)
	{
		if (ecode)
		{
			if (ecode != boost::asio::error::operation_aborted)
			{
				LogPrint (eLogError, "I2PTunnel: read error: ", ecode.message ());
				Terminate ();
			}
		}
		else
		{
			if (m_Stream)
			{
				auto s = shared_from_this ();
				m_Stream->AsyncSend (m_Buffer, bytes_transferred,
					[s](const boost::system::error_code& ecode)
					{
						if (!ecode)
							s->Receive ();
						else
							s->Terminate ();
					});
			}
		}
	}

	void I2PTunnelConnection::HandleWrite (const boost::system::error_code& ecode)
	{
		if (ecode)
		{
			LogPrint (eLogError, "I2PTunnel: write error: ", ecode.message ());
			if (ecode != boost::asio::error::operation_aborted)
				Terminate ();
		}
		else
			StreamReceive ();
	}

	void I2PTunnelConnection::StreamReceive ()
	{
		if (m_Stream)
		{
			if (m_Stream->GetStatus () == i2p::stream::eStreamStatusNew ||
				m_Stream->GetStatus () == i2p::stream::eStreamStatusOpen) // regular
			{
				m_Stream->AsyncReceive (boost::asio::buffer (m_StreamBuffer, I2P_TUNNEL_CONNECTION_BUFFER_SIZE),
					std::bind (&I2PTunnelConnection::HandleStreamReceive, shared_from_this (),
					std::placeholders::_1, std::placeholders::_2),
					I2P_TUNNEL_CONNECTION_MAX_IDLE);
			}
			else // closed by peer
			{
				// get remaning data
				auto len = m_Stream->ReadSome (m_StreamBuffer, I2P_TUNNEL_CONNECTION_BUFFER_SIZE);
				if (len > 0) // still some data
					Write (m_StreamBuffer, len);
				else // no more data
					Terminate ();
			}
		}
	}

	void I2PTunnelConnection::HandleStreamReceive (const boost::system::error_code& ecode, std::size_t bytes_transferred)
	{
		if (ecode)
		{
			if (ecode != boost::asio::error::operation_aborted)
			{
				LogPrint (eLogError, "I2PTunnel: stream read error: ", ecode.message ());
				if (bytes_transferred > 0)
					Write (m_StreamBuffer, bytes_transferred); // postpone termination
				else if (ecode == boost::asio::error::timed_out && m_Stream && m_Stream->IsOpen ())
					StreamReceive ();
				else
					Terminate ();
			}
			else
				Terminate ();
		}
		else
			Write (m_StreamBuffer, bytes_transferred);
	}

	void I2PTunnelConnection::Write (const uint8_t * buf, size_t len)
	{
		boost::asio::async_write (*m_Socket, boost::asio::buffer (buf, len), boost::asio::transfer_all (),
			std::bind (&I2PTunnelConnection::HandleWrite, shared_from_this (), std::placeholders::_1));
	}

	void I2PTunnelConnection::HandleConnect (const boost::system::error_code& ecode)
	{
		if (ecode)
		{
			LogPrint (eLogError, "I2PTunnel: connect error: ", ecode.message ());
			Terminate ();
		}
		else
		{
			LogPrint (eLogDebug, "I2PTunnel: connected");
			if (m_IsQuiet)
				StreamReceive ();
			else
			{
				// send destination first like received from I2P
				std::string dest = m_Stream->GetRemoteIdentity ()->ToBase64 ();
				dest += "\n";
				if(sizeof(m_StreamBuffer) >= dest.size()) {
					memcpy (m_StreamBuffer, dest.c_str (), dest.size ());
				}
				HandleStreamReceive (boost::system::error_code (), dest.size ());
			}
			Receive ();
		}
	}

	void I2PClientTunnelConnectionHTTP::Write (const uint8_t * buf, size_t len)
	{
		if (m_HeaderSent)
			I2PTunnelConnection::Write (buf, len);
		else
		{
			m_InHeader.clear ();
			m_InHeader.write ((const char *)buf, len);
			std::string line;
			bool endOfHeader = false;
			while (!endOfHeader)
			{
				std::getline(m_InHeader, line);
				if (!m_InHeader.fail ())
				{
					if (line == "\r") endOfHeader = true;
					else
					{
						if (!m_ConnectionSent && !line.compare(0, 10, "Connection"))
						{
							/* close connection, if not Connection: (U|u)pgrade (for websocket) */
							auto x = line.find("pgrade");
							if (x != std::string::npos && std::tolower(line[x - 1]) == 'u')
								m_OutHeader << line << "\r\n";
							else
								m_OutHeader << "Connection: close\r\n";

							m_ConnectionSent = true;
						}
						else if (!m_ProxyConnectionSent && !line.compare(0, 16, "Proxy-Connection"))
						{
							m_OutHeader << "Proxy-Connection: close\r\n";
							m_ProxyConnectionSent = true;
						}
						else
							m_OutHeader << line << "\n";
					}
				}
				else
					break;
			}

			if (endOfHeader)
			{
				if (!m_ConnectionSent) m_OutHeader << "Connection: close\r\n";
				if (!m_ProxyConnectionSent) m_OutHeader << "Proxy-Connection: close\r\n";
				m_OutHeader << "\r\n"; // end of header
				m_OutHeader << m_InHeader.str ().substr (m_InHeader.tellg ()); // data right after header
				m_InHeader.str ("");
				m_HeaderSent = true;
				I2PTunnelConnection::Write ((uint8_t *)m_OutHeader.str ().c_str (), m_OutHeader.str ().length ());
			}
		}
	}

	I2PServerTunnelConnectionHTTP::I2PServerTunnelConnectionHTTP (I2PService * owner, std::shared_ptr<i2p::stream::Stream> stream,
		std::shared_ptr<boost::asio::ip::tcp::socket> socket,
		const boost::asio::ip::tcp::endpoint& target, const std::string& host):
		I2PTunnelConnection (owner, stream, socket, target), m_Host (host), m_HeaderSent (false), m_From (stream->GetRemoteIdentity ())
	{
	}

	void I2PServerTunnelConnectionHTTP::Write (const uint8_t * buf, size_t len)
	{
		if (m_HeaderSent)
			I2PTunnelConnection::Write (buf, len);
		else
		{
			m_InHeader.clear ();
			m_InHeader.write ((const char *)buf, len);
			std::string line;
			bool endOfHeader = false;
			while (!endOfHeader)
			{
				std::getline(m_InHeader, line);
				if (!m_InHeader.fail ())
				{
					if (line == "\r") endOfHeader = true;
					else
					{
						if (m_Host.length () > 0 && line.find ("Host:") != std::string::npos)
							m_OutHeader << "Host: " << m_Host << "\r\n"; // override host
						else
							m_OutHeader << line << "\n";
					}
				}
				else
					break;
			}
			// add X-I2P fields
			if (m_From)
			{
				m_OutHeader << X_I2P_DEST_B32 << ": " << context.GetAddressBook ().ToAddress(m_From->GetIdentHash ()) << "\r\n";
				m_OutHeader << X_I2P_DEST_HASH << ": " << m_From->GetIdentHash ().ToBase64 () << "\r\n";
				m_OutHeader << X_I2P_DEST_B64 << ": " << m_From->ToBase64 () << "\r\n";
			}

			if (endOfHeader)
			{
				m_OutHeader << "\r\n"; // end of header
				m_OutHeader << m_InHeader.str ().substr (m_InHeader.tellg ()); // data right after header
				m_InHeader.str ("");
				m_HeaderSent = true;
				I2PTunnelConnection::Write ((uint8_t *)m_OutHeader.str ().c_str (), m_OutHeader.str ().length ());
			}
		}
	}

	I2PTunnelConnectionIRC::I2PTunnelConnectionIRC (I2PService * owner, std::shared_ptr<i2p::stream::Stream> stream,
		std::shared_ptr<boost::asio::ip::tcp::socket> socket,
		const boost::asio::ip::tcp::endpoint& target, const std::string& webircpass):
		I2PTunnelConnection (owner, stream, socket, target), m_From (stream->GetRemoteIdentity ()),
		m_NeedsWebIrc (webircpass.length() ? true : false), m_WebircPass (webircpass)
	{
	}

	void I2PTunnelConnectionIRC::Write (const uint8_t * buf, size_t len)
	{
		m_OutPacket.str ("");
		if (m_NeedsWebIrc)
		{
			m_NeedsWebIrc = false;
			m_OutPacket << "WEBIRC " << m_WebircPass << " cgiirc " << context.GetAddressBook ().ToAddress (m_From->GetIdentHash ()) << " " << GetSocket ()->local_endpoint ().address () << std::endl;
		}

		m_InPacket.clear ();
		m_InPacket.write ((const char *)buf, len);

		while (!m_InPacket.eof () && !m_InPacket.fail ())
		{
			std::string line;
			std::getline (m_InPacket, line);
			if (line.length () == 0 && m_InPacket.eof ())
				m_InPacket.str ("");
			auto pos = line.find ("USER");
			if (!pos) // start of line
			{
				pos = line.find (" ");
				pos++;
				pos = line.find (" ", pos);
				pos++;
				auto nextpos = line.find (" ", pos);
				m_OutPacket << line.substr (0, pos);
				m_OutPacket << context.GetAddressBook ().ToAddress (m_From->GetIdentHash ());
				m_OutPacket << line.substr (nextpos) << '\n';
			}
			else
				m_OutPacket << line << '\n';
		}
		I2PTunnelConnection::Write ((uint8_t *)m_OutPacket.str ().c_str (), m_OutPacket.str ().length ());
	}


	/* This handler tries to establish a connection with the desired server and dies if it fails to do so */
	class I2PClientTunnelHandler: public I2PServiceHandler, public std::enable_shared_from_this<I2PClientTunnelHandler>
	{
		public:
			I2PClientTunnelHandler (I2PClientTunnel * parent, std::shared_ptr<const Address> address,
				int destinationPort, std::shared_ptr<boost::asio::ip::tcp::socket> socket):
				I2PServiceHandler(parent), m_Address(address),
				m_DestinationPort (destinationPort), m_Socket(socket) {};
			void Handle();
			void Terminate();
		private:
			void HandleStreamRequestComplete (std::shared_ptr<i2p::stream::Stream> stream);
			std::shared_ptr<const Address> m_Address;
			int m_DestinationPort;
			std::shared_ptr<boost::asio::ip::tcp::socket> m_Socket;
	};

	void I2PClientTunnelHandler::Handle()
	{
		GetOwner()->CreateStream (
			std::bind (&I2PClientTunnelHandler::HandleStreamRequestComplete, shared_from_this(), std::placeholders::_1),
			m_Address, m_DestinationPort);
	}

	void I2PClientTunnelHandler::HandleStreamRequestComplete (std::shared_ptr<i2p::stream::Stream> stream)
	{
		if (stream)
		{
			if (Kill()) return;
			LogPrint (eLogDebug, "I2PTunnel: new connection");
			auto connection = std::make_shared<I2PTunnelConnection>(GetOwner(), m_Socket, stream);
			GetOwner()->AddHandler (connection);
			connection->I2PConnect ();
			Done(shared_from_this());
		}
		else
		{
			LogPrint (eLogError, "I2PTunnel: Client Tunnel Issue when creating the stream, check the previous warnings for more info.");
			Terminate();
		}
	}

	void I2PClientTunnelHandler::Terminate()
	{
		if (Kill()) return;
		if (m_Socket)
		{
			m_Socket->close();
			m_Socket = nullptr;
		}
		Done(shared_from_this());
	}

	I2PClientTunnel::I2PClientTunnel (const std::string& name, const std::string& destination,
		const std::string& address, int port, std::shared_ptr<ClientDestination> localDestination, int destinationPort):
		TCPIPAcceptor (address, port, localDestination), m_Name (name), m_Destination (destination),
		m_DestinationPort (destinationPort)
	{
	}

	void I2PClientTunnel::Start ()
	{
		TCPIPAcceptor::Start ();
		GetAddress ();
	}

	void I2PClientTunnel::Stop ()
	{
		TCPIPAcceptor::Stop();
		m_Address = nullptr;
	}

	/* HACK: maybe we should create a caching IdentHash provider in AddressBook */
	std::shared_ptr<const Address> I2PClientTunnel::GetAddress ()
	{
		if (!m_Address)
		{
			m_Address = i2p::client::context.GetAddressBook ().GetAddress (m_Destination);
			if (!m_Address)
				LogPrint (eLogWarning, "I2PTunnel: Remote destination ", m_Destination, " not found");
		}
		return m_Address;
	}

	std::shared_ptr<I2PServiceHandler> I2PClientTunnel::CreateHandler(std::shared_ptr<boost::asio::ip::tcp::socket> socket)
	{
		auto address = GetAddress ();
		if (address)
			return std::make_shared<I2PClientTunnelHandler>(this, address, m_DestinationPort, socket);
		else
			return nullptr;
	}

	I2PServerTunnel::I2PServerTunnel (const std::string& name, const std::string& address,
		int port, std::shared_ptr<ClientDestination> localDestination, int inport, bool gzip):
		I2PService (localDestination), m_IsUniqueLocal(true), m_Name (name), m_Address (address), m_Port (port), m_IsAccessList (false)
	{
		m_PortDestination = localDestination->CreateStreamingDestination (inport > 0 ? inport : port, gzip);
	}

	void I2PServerTunnel::Start ()
	{
		m_Endpoint.port (m_Port);
		boost::system::error_code ec;
		auto addr = boost::asio::ip::address::from_string (m_Address, ec);
		if (!ec)
		{
			m_Endpoint.address (addr);
			Accept ();
		}
		else
		{
			auto resolver = std::make_shared<boost::asio::ip::tcp::resolver>(GetService ());
			resolver->async_resolve (boost::asio::ip::tcp::resolver::query (m_Address, ""),
				std::bind (&I2PServerTunnel::HandleResolve, this,
					std::placeholders::_1, std::placeholders::_2, resolver));
		}
	}

	void I2PServerTunnel::Stop ()
	{
		ClearHandlers ();
	}

	void I2PServerTunnel::HandleResolve (const boost::system::error_code& ecode, boost::asio::ip::tcp::resolver::iterator it,
		std::shared_ptr<boost::asio::ip::tcp::resolver> resolver)
	{
		if (!ecode)
		{
			auto addr = (*it).endpoint ().address ();
			LogPrint (eLogInfo, "I2PTunnel: server tunnel ", (*it).host_name (), " has been resolved to ", addr);
			m_Endpoint.address (addr);
			Accept ();
		}
		else
			LogPrint (eLogError, "I2PTunnel: Unable to resolve server tunnel address: ", ecode.message ());
	}

	void I2PServerTunnel::SetAccessList (const std::set<i2p::data::IdentHash>& accessList)
	{
		m_AccessList = accessList;
		m_IsAccessList = true;
	}

	void I2PServerTunnel::Accept ()
	{
		if (m_PortDestination)
			m_PortDestination->SetAcceptor (std::bind (&I2PServerTunnel::HandleAccept, this, std::placeholders::_1));

		auto localDestination = GetLocalDestination ();
		if (localDestination)
		{
			if (!localDestination->IsAcceptingStreams ()) // set it as default if not set yet
				localDestination->AcceptStreams (std::bind (&I2PServerTunnel::HandleAccept, this, std::placeholders::_1));
		}
		else
			LogPrint (eLogError, "I2PTunnel: Local destination not set for server tunnel");
	}

	void I2PServerTunnel::HandleAccept (std::shared_ptr<i2p::stream::Stream> stream)
	{
		if (stream)
		{
			if (m_IsAccessList)
			{
				if (!m_AccessList.count (stream->GetRemoteIdentity ()->GetIdentHash ()))
				{
					LogPrint (eLogWarning, "I2PTunnel: Address ", stream->GetRemoteIdentity ()->GetIdentHash ().ToBase32 (), " is not in white list. Incoming connection dropped");
					stream->Close ();
					return;
				}
			}
			// new connection
			auto conn = CreateI2PConnection (stream);
			AddHandler (conn);
			conn->Connect (m_IsUniqueLocal);
		}
	}

	std::shared_ptr<I2PTunnelConnection> I2PServerTunnel::CreateI2PConnection (std::shared_ptr<i2p::stream::Stream> stream)
	{
		return std::make_shared<I2PTunnelConnection> (this, stream, std::make_shared<boost::asio::ip::tcp::socket> (GetService ()), GetEndpoint ());

	}

	I2PServerTunnelHTTP::I2PServerTunnelHTTP (const std::string& name, const std::string& address,
		int port, std::shared_ptr<ClientDestination> localDestination,
		const std::string& host, int inport, bool gzip):
		I2PServerTunnel (name, address, port, localDestination, inport, gzip),
		m_Host (host)
	{
	}

	std::shared_ptr<I2PTunnelConnection> I2PServerTunnelHTTP::CreateI2PConnection (std::shared_ptr<i2p::stream::Stream> stream)
	{
		return std::make_shared<I2PServerTunnelConnectionHTTP> (this, stream,
			std::make_shared<boost::asio::ip::tcp::socket> (GetService ()), GetEndpoint (), m_Host);
	}

	I2PServerTunnelIRC::I2PServerTunnelIRC (const std::string& name, const std::string& address,
		int port, std::shared_ptr<ClientDestination> localDestination,
		const std::string& webircpass, int inport, bool gzip):
		I2PServerTunnel (name, address, port, localDestination, inport, gzip),
		m_WebircPass (webircpass)
	{
	}

	std::shared_ptr<I2PTunnelConnection> I2PServerTunnelIRC::CreateI2PConnection (std::shared_ptr<i2p::stream::Stream> stream)
	{
		return std::make_shared<I2PTunnelConnectionIRC> (this, stream, std::make_shared<boost::asio::ip::tcp::socket> (GetService ()), GetEndpoint (), this->m_WebircPass);
	}

	void I2PUDPServerTunnel::HandleRecvFromI2P(const i2p::data::IdentityEx& from, uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
	{
		if (!m_LastSession || m_LastSession->Identity.GetLL()[0] != from.GetIdentHash ().GetLL()[0] || fromPort != m_LastSession->RemotePort)
		{
			std::lock_guard<std::mutex> lock(m_SessionsMutex);
			m_LastSession = ObtainUDPSession(from, toPort, fromPort);
		}
		m_LastSession->IPSocket.send_to(boost::asio::buffer(buf, len), m_RemoteEndpoint);
		m_LastSession->LastActivity = i2p::util::GetMillisecondsSinceEpoch();
	}

	void I2PUDPServerTunnel::HandleRecvFromI2PRaw (uint16_t, uint16_t, const uint8_t * buf, size_t len)
	{
		if (m_LastSession)
		{
			m_LastSession->IPSocket.send_to(boost::asio::buffer(buf, len), m_RemoteEndpoint);
			m_LastSession->LastActivity = i2p::util::GetMillisecondsSinceEpoch();
		}	
	}	
		
	void I2PUDPServerTunnel::ExpireStale(const uint64_t delta) {
		std::lock_guard<std::mutex> lock(m_SessionsMutex);
		uint64_t now = i2p::util::GetMillisecondsSinceEpoch();
		auto itr = m_Sessions.begin();
		while(itr != m_Sessions.end()) {
			if(now - (*itr)->LastActivity >= delta )
				itr = m_Sessions.erase(itr);
			else
				++itr;
		}
	}

	void I2PUDPClientTunnel::ExpireStale(const uint64_t delta) {
		std::lock_guard<std::mutex> lock(m_SessionsMutex);
		uint64_t now = i2p::util::GetMillisecondsSinceEpoch();
		std::vector<uint16_t> removePorts;
		for (const auto & s : m_Sessions) {
			if (now - s.second->second >= delta)
				removePorts.push_back(s.first);
		}
		for(auto port : removePorts) {
			m_Sessions.erase(port);
		}
	}

	UDPSessionPtr I2PUDPServerTunnel::ObtainUDPSession(const i2p::data::IdentityEx& from, uint16_t localPort, uint16_t remotePort)
	{
		auto ih = from.GetIdentHash();
		for (auto & s : m_Sessions )
		{
			if (s->Identity.GetLL()[0] == ih.GetLL()[0] && remotePort == s->RemotePort)
			{
				/** found existing session */
				LogPrint(eLogDebug, "UDPServer: found session ", s->IPSocket.local_endpoint(), " ", ih.ToBase32());
				return s;
			}
		}
		boost::asio::ip::address addr;
		/** create new udp session */
		if(m_IsUniqueLocal && m_LocalAddress.is_loopback())
		{
			auto ident = from.GetIdentHash();
			addr = GetLoopbackAddressFor(ident);
		}
		else
			addr = m_LocalAddress;
		boost::asio::ip::udp::endpoint ep(addr, 0);
		m_Sessions.push_back(std::make_shared<UDPSession>(ep, m_LocalDest, m_RemoteEndpoint, &ih, localPort, remotePort));
		auto & back = m_Sessions.back();
		return back;
	}

	UDPSession::UDPSession(boost::asio::ip::udp::endpoint localEndpoint,
		const std::shared_ptr<i2p::client::ClientDestination> & localDestination,
		boost::asio::ip::udp::endpoint endpoint, const i2p::data::IdentHash * to,
		uint16_t ourPort, uint16_t theirPort) :
		m_Destination(localDestination->GetDatagramDestination()),
		IPSocket(localDestination->GetService(), localEndpoint),
		SendEndpoint(endpoint),
		LastActivity(i2p::util::GetMillisecondsSinceEpoch()),
		LocalPort(ourPort),
		RemotePort(theirPort)
	{
		IPSocket.set_option (boost::asio::socket_base::receive_buffer_size (I2P_UDP_MAX_MTU ));
		memcpy(Identity, to->data(), 32);
		Receive();
	}

	void UDPSession::Receive() {
		LogPrint(eLogDebug, "UDPSession: Receive");
		IPSocket.async_receive_from(boost::asio::buffer(m_Buffer, I2P_UDP_MAX_MTU),
			FromEndpoint, std::bind(&UDPSession::HandleReceived, this, std::placeholders::_1, std::placeholders::_2));
	}

	void UDPSession::HandleReceived(const boost::system::error_code & ecode, std::size_t len)
	{
		if(!ecode)
		{
			LogPrint(eLogDebug, "UDPSession: forward ", len, "B from ", FromEndpoint);
			auto ts = i2p::util::GetMillisecondsSinceEpoch();
			auto session = m_Destination->GetSession (Identity);
			if (ts > LastActivity + I2P_UDP_REPLIABLE_DATAGRAM_INTERVAL)
				m_Destination->SendDatagram(session, m_Buffer, len, LocalPort, RemotePort);
			else
				m_Destination->SendRawDatagram(session, m_Buffer, len, LocalPort, RemotePort);
			size_t numPackets = 0;
			while (numPackets < i2p::datagram::DATAGRAM_SEND_QUEUE_MAX_SIZE)
			{	
				boost::system::error_code ec;
				size_t moreBytes = IPSocket.available(ec);
				if (ec || !moreBytes) break;
				len = IPSocket.receive_from (boost::asio::buffer (m_Buffer, I2P_UDP_MAX_MTU), FromEndpoint, 0, ec);
				m_Destination->SendRawDatagram (session, m_Buffer, len, LocalPort, RemotePort);			
				numPackets++;
			}	
			if (numPackets > 0)
				LogPrint(eLogDebug, "UDPSession: forward more ", numPackets, "packets B from ", FromEndpoint);
			m_Destination->FlushSendQueue (session);
			LastActivity = ts;
			Receive();
		} 
		else
			LogPrint(eLogError, "UDPSession: ", ecode.message());
	}

	I2PUDPServerTunnel::I2PUDPServerTunnel(const std::string & name, std::shared_ptr<i2p::client::ClientDestination> localDestination,
		boost::asio::ip::address localAddress, boost::asio::ip::udp::endpoint forwardTo, uint16_t port, bool gzip) :
		m_IsUniqueLocal(true),
		m_Name(name),
		m_LocalAddress(localAddress),
		m_RemoteEndpoint(forwardTo)
	{
		m_LocalDest = localDestination;
		m_LocalDest->Start();
		auto dgram = m_LocalDest->CreateDatagramDestination(gzip);
		dgram->SetReceiver(std::bind(&I2PUDPServerTunnel::HandleRecvFromI2P, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, std::placeholders::_4, std::placeholders::_5));
		dgram->SetRawReceiver(std::bind(&I2PUDPServerTunnel::HandleRecvFromI2PRaw, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, std::placeholders::_4));	
	}

	I2PUDPServerTunnel::~I2PUDPServerTunnel()
	{
		auto dgram = m_LocalDest->GetDatagramDestination();
		if (dgram) dgram->ResetReceiver();

		LogPrint(eLogInfo, "UDPServer: done");
	}

	void I2PUDPServerTunnel::Start() {
		m_LocalDest->Start();
	}

	std::vector<std::shared_ptr<DatagramSessionInfo> > I2PUDPServerTunnel::GetSessions()
	{
		std::vector<std::shared_ptr<DatagramSessionInfo> > sessions;
		std::lock_guard<std::mutex> lock(m_SessionsMutex);

		for ( UDPSessionPtr s : m_Sessions )
		{
			if (!s->m_Destination) continue;
			auto info = s->m_Destination->GetInfoForRemote(s->Identity);
			if(!info) continue;

			auto sinfo = std::make_shared<DatagramSessionInfo>();
			sinfo->Name = m_Name;
			sinfo->LocalIdent = std::make_shared<i2p::data::IdentHash>(m_LocalDest->GetIdentHash().data());
			sinfo->RemoteIdent = std::make_shared<i2p::data::IdentHash>(s->Identity.data());
			sinfo->CurrentIBGW = info->IBGW;
			sinfo->CurrentOBEP = info->OBEP;
			sessions.push_back(sinfo);
		}
		return sessions;
	}

	I2PUDPClientTunnel::I2PUDPClientTunnel(const std::string & name, const std::string &remoteDest,
		boost::asio::ip::udp::endpoint localEndpoint,
		std::shared_ptr<i2p::client::ClientDestination> localDestination,
		uint16_t remotePort, bool gzip) :
		m_Name(name),
		m_RemoteDest(remoteDest),
		m_LocalDest(localDestination),
		m_LocalEndpoint(localEndpoint),
		m_RemoteIdent(nullptr),
		m_ResolveThread(nullptr),
		m_LocalSocket(localDestination->GetService(), localEndpoint),
		RemotePort(remotePort), m_LastPort (0),
		m_cancel_resolve(false)
	{
		m_LocalSocket.set_option (boost::asio::socket_base::receive_buffer_size (I2P_UDP_MAX_MTU ));

		auto dgram = m_LocalDest->CreateDatagramDestination(gzip);
		dgram->SetReceiver(std::bind(&I2PUDPClientTunnel::HandleRecvFromI2P, this,
			std::placeholders::_1, std::placeholders::_2,
			std::placeholders::_3, std::placeholders::_4,
			std::placeholders::_5));
		dgram->SetRawReceiver(std::bind(&I2PUDPClientTunnel::HandleRecvFromI2PRaw, this,
			std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, std::placeholders::_4));	
	}

	void I2PUDPClientTunnel::Start() {
		m_LocalDest->Start();
		if (m_ResolveThread == nullptr)
			m_ResolveThread = new std::thread(std::bind(&I2PUDPClientTunnel::TryResolving, this));
		RecvFromLocal();
	}

	void I2PUDPClientTunnel::RecvFromLocal()
	{
		m_LocalSocket.async_receive_from(boost::asio::buffer(m_RecvBuff, I2P_UDP_MAX_MTU),
			m_RecvEndpoint, std::bind(&I2PUDPClientTunnel::HandleRecvFromLocal, this, std::placeholders::_1, std::placeholders::_2));
	}

	void I2PUDPClientTunnel::HandleRecvFromLocal(const boost::system::error_code & ec, std::size_t transferred)
	{
		if(ec) {
			LogPrint(eLogError, "UDP Client: ", ec.message());
			return;
		}
		if(!m_RemoteIdent) {
			LogPrint(eLogWarning, "UDP Client: remote endpoint not resolved yet");
			RecvFromLocal();
			return; // drop, remote not resolved
		}
		auto remotePort = m_RecvEndpoint.port();
		if (!m_LastPort || m_LastPort != remotePort)
		{	
			auto itr = m_Sessions.find(remotePort);
			if (itr != m_Sessions.end()) 
				m_LastSession = itr->second;
			else	
			{
				m_LastSession = std::make_shared<UDPConvo>(boost::asio::ip::udp::endpoint(m_RecvEndpoint), 0);
				m_Sessions.emplace (remotePort, m_LastSession);
			}	
			m_LastPort = remotePort;
		}	
		// send off to remote i2p destination
		auto ts = i2p::util::GetMillisecondsSinceEpoch();
		LogPrint(eLogDebug, "UDP Client: send ", transferred, " to ", m_RemoteIdent->ToBase32(), ":", RemotePort);
		auto session = m_LocalDest->GetDatagramDestination()->GetSession (*m_RemoteIdent);
		if (ts > m_LastSession->second + I2P_UDP_REPLIABLE_DATAGRAM_INTERVAL)		
			m_LocalDest->GetDatagramDestination()->SendDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort);
		else
			m_LocalDest->GetDatagramDestination()->SendRawDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort);
		size_t numPackets = 0;
		while (numPackets < i2p::datagram::DATAGRAM_SEND_QUEUE_MAX_SIZE)
		{	
			boost::system::error_code ec;
			size_t moreBytes = m_LocalSocket.available(ec);
			if (ec || !moreBytes) break;
			transferred = m_LocalSocket.receive_from (boost::asio::buffer (m_RecvBuff, I2P_UDP_MAX_MTU), m_RecvEndpoint, 0, ec);
			remotePort = m_RecvEndpoint.port();
			// TODO: check remotePort
			m_LocalDest->GetDatagramDestination()->SendRawDatagram (session, m_RecvBuff, transferred, remotePort, RemotePort);			
			numPackets++;
		}	
		if (numPackets)
			LogPrint(eLogDebug, "UDP Client: sent ", numPackets, " more packets to ", m_RemoteIdent->ToBase32());
		m_LocalDest->GetDatagramDestination()->FlushSendQueue (session);
		
		// mark convo as active
		if (m_LastSession)
			m_LastSession->second = ts;
		RecvFromLocal();
	}

	std::vector<std::shared_ptr<DatagramSessionInfo> > I2PUDPClientTunnel::GetSessions()
	{
		// TODO: implement
		std::vector<std::shared_ptr<DatagramSessionInfo> > infos;
		return infos;
	}

	void I2PUDPClientTunnel::TryResolving() {
		LogPrint(eLogInfo, "UDP Tunnel: Trying to resolve ", m_RemoteDest);

		std::shared_ptr<const Address> addr;
		while(!(addr = context.GetAddressBook().GetAddress(m_RemoteDest)) && !m_cancel_resolve)
		{
			LogPrint(eLogWarning, "UDP Tunnel: failed to lookup ", m_RemoteDest);
			std::this_thread::sleep_for(std::chrono::seconds(1));
		}
		if(m_cancel_resolve)
		{
			LogPrint(eLogError, "UDP Tunnel: lookup of ", m_RemoteDest, " was cancelled");
			return;
		}
		if (!addr || !addr->IsIdentHash ())
		{
			LogPrint(eLogError, "UDP Tunnel: ", m_RemoteDest, " not found");
			return;
		}
		m_RemoteIdent = new i2p::data::IdentHash;
		*m_RemoteIdent = addr->identHash;
		LogPrint(eLogInfo, "UDP Tunnel: resolved ", m_RemoteDest, " to ", m_RemoteIdent->ToBase32());
	}

	void I2PUDPClientTunnel::HandleRecvFromI2P(const i2p::data::IdentityEx& from, uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
	{
		if(m_RemoteIdent && from.GetIdentHash() == *m_RemoteIdent)
			HandleRecvFromI2PRaw (fromPort, toPort, buf, len);
		else
			LogPrint(eLogWarning, "UDP Client: unwarranted traffic from ", from.GetIdentHash().ToBase32());
	}

	void I2PUDPClientTunnel::HandleRecvFromI2PRaw(uint16_t fromPort, uint16_t toPort, const uint8_t * buf, size_t len)
	{
		auto itr = m_Sessions.find(toPort);
		// found convo ?
		if(itr != m_Sessions.end())
		{
			// found convo
			if (len > 0) 
			{
				LogPrint(eLogDebug, "UDP Client: got ", len, "B from ", m_RemoteIdent ? m_RemoteIdent->ToBase32() : "");
				m_LocalSocket.send_to(boost::asio::buffer(buf, len), itr->second->first);
				// mark convo as active
				itr->second->second = i2p::util::GetMillisecondsSinceEpoch();
			}
		}
		else
			LogPrint(eLogWarning, "UDP Client: not tracking udp session using port ", (int) toPort);
	}
		
	I2PUDPClientTunnel::~I2PUDPClientTunnel() {
		auto dgram = m_LocalDest->GetDatagramDestination();
		if (dgram) dgram->ResetReceiver();

		m_Sessions.clear();

		if(m_LocalSocket.is_open())
			m_LocalSocket.close();

		m_cancel_resolve = true;

		if(m_ResolveThread)
		{
			m_ResolveThread->join();
			delete m_ResolveThread;
			m_ResolveThread = nullptr;
		}
		if (m_RemoteIdent) delete m_RemoteIdent;
	}
}
}