% MAP masquerading application

% (C) 2010 by Harald Welte <laforge@gnumonks.org>
% (C) 2010 by On-Waves
%
% All Rights Reserved
%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 2 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License along
% with this program; if not, write to the Free Software Foundation, Inc.,
% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-module(osmo_map_masq).
-author('Harald Welte <laforge@gnumonks.org>').
-export([init/4]).

-record(loop_data,
        {udpSocket, udpSrvPort, udpRxAddr, udpRxPort,
	 ipaSocket, ipaStreamID, ipaDstAddr, ipaDstPort}).
	

init(UdpServerPort, IpaDstAddr, IpaDstPort, IpaStreamID) ->
	{ok, UdpSock} = gen_udp:open(UdpServerPort, [binary, inet]),
	{ok, TcpSock} = ipa_proto:connect(IpaDstAddr, IpaDstPort, []),
	% FIXME: result evaluation
	ipa_proto:register_stream(TcpSock, IpaStreamID, self()),
	loop(#loop_data{udpSocket=UdpSock, udpSrvPort=UdpServerPort,
			ipaSocket=TcpSock, ipaStreamID=IpaStreamID, ipaDstAddr=IpaDstAddr, ipaDstPort=IpaDstPort}).


loop(#loop_data{}=LoopData) ->
	io:format("osmo_masq_loop~n"),
	receive 
		{udp, S, ClientIP, ClientPort, Packet} when S =:= LoopData#loop_data.udpSocket ->
			io:format("UDP received from ~p:~p ==> ~p~n", [ClientIP, ClientPort, Packet]),
			{ok, SccpHdr, SccpPayload} = sccp_proto:split_udt_sync(Packet),
			{ok, NewSccpPayload} = tcap_map_patch:handle_tcap_msg(binary_to_list(SccpPayload)),
			{ok, NewSccpBinary} = sccp_proto:wrap_udt_sync(SccpHdr, list_to_binary(NewSccpPayload)),
			ipa_proto:send(LoopData#loop_data.ipaSocket, LoopData#loop_data.ipaStreamID, NewSccpBinary),
			% loop using the (new?) UDP socket Rx IP and Port number
			loop(LoopData#loop_data{udpRxAddr=ClientIP, udpRxPort=ClientPort});
		{ipa, S, StreamID, Message} when S =:= LoopData#loop_data.ipaSocket,
						  StreamID =:= LoopData#loop_data.ipaStreamID ->
			io:format("IPA received (Stream ~p)~n", [LoopData#loop_data.ipaStreamID]),
			{ok, SccpHdr, SccpPayload} = sccp_proto:split_udt_sync(Message),
			{ok, NewSccpPayload} = tcap_map_patch:handle_tcap_msg(binary_to_list(SccpPayload)),
			{ok, NewSccpBinary} = sccp_proto:wrap_udt_sync(SccpHdr, list_to_binary(NewSccpPayload)),
			gen_udp:send(LoopData#loop_data.udpSocket, LoopData#loop_data.udpRxAddr,
				     LoopData#loop_data.udpRxPort, NewSccpBinary),
			loop(LoopData);
		{ipa_closed, S} when S =:= LoopData#loop_data.ipaSocket ->
			io:format("IPA socket was closed, stopping process~n")
	end.