% MGW NAT core routines as well as ISUP + SCCP Rewriting

% (C) 2011 by Harald Welte <laforge@gnumonks.org>
% (C) 2011 OnWaves
%
% All Rights Reserved
%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU Affero General Public License as
% published by the Free Software Foundation; either version 3 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 Affero General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

-module(mgw_nat).
-author("Harald Welte <laforge@gnumonks.org>").

% Main entry function for M2UA binary messages
-export([mangle_rx_data/4]).

% Action functions to apply specific translations
-export([mangle_rx_sccp/4, mangle_rx_isup/4]).

% exports belwo needed by map_masq.erl
-export([isup_party_internationalize/2, isup_party_nationalize/2, isup_party_replace_prefix/3,
	 isup_party_nat00_internationalize/1]).

%-include_lib("kernel/include/inet.hrl").
%-include_lib("kernel/include/inet_sctp.hrl").

-include_lib("osmo_ss7/include/m2ua.hrl").
-include_lib("osmo_ss7/include/mtp3.hrl").
-include_lib("osmo_ss7/include/isup.hrl").
-include_lib("osmo_ss7/include/sccp.hrl").

% mangle the received data
mangle_rx_data(From, Path, Data, Fn) when is_list(Path), is_binary(Data) ->
	{ok, M2ua} = m2ua_codec:parse_m2ua_msg(Data),
	%io:format("M2UA Decode: ~p~n", [M2ua]),
	case M2ua of
		#m2ua_msg{msg_class = ?M2UA_MSGC_MAUP,
			  msg_type = ?M2UA_MAUP_MSGT_DATA} ->
			M2ua_out = mangle_rx_m2ua_maup(Fn, From, Path, M2ua);
		#m2ua_msg{} ->
			% simply pass it along unmodified
			M2ua_out = M2ua
	end,
	% re-encode the data
	%io:format("M2UA Encode: ~p~n", [M2ua_out]),
	m2ua_codec:encode_m2ua_msg(M2ua_out).

% mangle the received M2UA
mangle_rx_m2ua_maup(Fn, From, Path, M2ua = #m2ua_msg{parameters = Params}) ->
	{_Len, M2uaPayload} = proplists:get_value(16#300, Params),
	Mtp3 = mtp3_codec:parse_mtp3_msg(M2uaPayload),
	%io:format("MTP3 Decode: ~p~n", [Mtp3]),
	Mtp3_out = mangle_rx_mtp3(Fn, From, Path ++ [M2ua], Mtp3),
	%io:format("MTP3 Encode: ~p~n", [Mtp3_out]),
	Mtp3OutBin = mtp3_codec:encode_mtp3_msg(Mtp3_out),
	Params2 = proplists:delete(16#300, Params),
	ParamsNew = Params2 ++ [{16#300, {byte_size(Mtp3OutBin), Mtp3OutBin}}],
	% return mangled parsed m2ua msg
	M2ua#m2ua_msg{parameters = ParamsNew}.

% mangle the MTP3 payload
mangle_rx_mtp3(Fn, From, Path, Mtp3 = #mtp3_msg{service_ind = Service}) ->
	mangle_rx_mtp3_serv(Fn, From, Path, Service, Mtp3).

% mangle the ISUP content
mangle_rx_mtp3_serv(Fn, From, Path, ?MTP3_SERV_ISUP, Mtp3 = #mtp3_msg{payload = Payload}) ->
	%io:format("ISUP In: ~p~n", [Payload]),
	Isup = isup_codec:parse_isup_msg(Payload),
	%io:format("ISUP Decode: ~p~n", [Isup]),
	%IsupMangled = mangle_rx_isup(From, Path, Isup#isup_msg.msg_type, Isup),
	try Fn(isup, From, Path, Isup#isup_msg.msg_type, Isup) of
		IsupMangled ->
			if IsupMangled == Isup ->
				% return the unmodified original payload
				Mtp3;
			   true ->
				io:format("ISUP Encode In: ~p~n", [IsupMangled]),
				Payload_out = isup_codec:encode_isup_msg(IsupMangled),
				io:format("ISUP Encode Out: ~p~n", [Payload_out]),
				% return modified MTP3 payload
				Mtp3#mtp3_msg{payload = Payload_out}
			end
	catch error:Error ->
		io:format("ISUP In: ~p~n", [Payload]),
		io:format("ISUP Decode: ~p~n", [Isup]),
		ip:format("ISUP mangling Error: ~p~n", [Error]),
		% return the unmodified original payload
		Mtp3
	end;
% mangle the SCCP content
mangle_rx_mtp3_serv(Fn, From, Path, ?MTP3_SERV_SCCP, Mtp3 = #mtp3_msg{payload = Payload}) ->
	%io:format("SCCP In: ~p~n", [Payload]),
	{ok, Sccp} = sccp_codec:parse_sccp_msg(Payload),
	%io:format("SCCP Decode: ~p~n", [Sccp]),
	SccpMangled = Fn(sccp, From, Path ++ [Mtp3], Sccp#sccp_msg.msg_type, Sccp),
	SccpMasqued = mangle_rx_sccp_map(Fn, From, Path ++ [Mtp3],
					 SccpMangled#sccp_msg.msg_type, SccpMangled),
	%SccpMangled = mangle_rx_sccp(From, Path ++ [Mtp3], Sccp#sccp_msg.msg_type, Sccp),
	%SccpMasqued = sccp_masq:sccp_masq_msg(From, SccpMangled#sccp_msg.msg_type,
	%				      SccpMangled),
	if SccpMasqued == Sccp ->
		Mtp3;
	   true ->
		%io:format("SCCP Encode In: ~p~n", [SccpMasqued]),
		Payload_out = sccp_codec:encode_sccp_msg(SccpMasqued),
		%io:format("SCCP Encode Out: ~p~n", [Payload_out]),
		% return modified MTP3 payload
		Mtp3#mtp3_msg{payload = Payload_out}
	end;
% default: do nothing
mangle_rx_mtp3_serv(_Fn, _From, _Path, _, Mtp3) ->
	Mtp3.

% Mangle the actual MAP payload inside the UDT data portion
mangle_rx_sccp_map(Fn, From, Path, ?SCCP_MSGT_UDT, Msg = #sccp_msg{parameters = Opts}) ->
	UserData = proplists:get_value(user_data, Opts),
	MapDec = map_codec:parse_tcap_msg(UserData),
	%MapDecNew = map_masq:mangle_map(From, MapDec),
	MapDecNew = Fn(map, From, Path ++ [Msg], 0, MapDec),
	MapEncNew = maybe_re_encode(MapDec, MapDecNew, UserData),
	Opts3 = lists:keyreplace(user_data, 1, Opts,
				 {user_data, MapEncNew}),
	Msg#sccp_msg{parameters = Opts3};
mangle_rx_sccp_map(_Fn, _From, _Path, _MsgType, Msg) ->
	Msg.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Actual mangling of the decoded SCCP messages
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% iterate over list of rewrite tuples and apply translation if there is a match
do_sccp_gt_rewrite(GT, _From, []) ->
	GT;
do_sccp_gt_rewrite(GT = #global_title{phone_number = PhoneNum}, from_stp, [Head|List]) ->
	{MscSide, StpSide, Comment} = Head,
	StpSideList = osmo_util:int2digit_list(StpSide),
	MscSideList = osmo_util:int2digit_list(MscSide),
	if PhoneNum == StpSideList ->
		NewPhoneNum = MscSideList,
		io:format("SCCP STP->MSC rewrite (~p) ~p -> ~p~n",
			  [Comment, PhoneNum, NewPhoneNum]),
		GT#global_title{phone_number = NewPhoneNum};
	   true ->
		do_sccp_gt_rewrite(GT, from_stp, List)
	end;
do_sccp_gt_rewrite(GT = #global_title{phone_number = PhoneNum}, from_msc, [Head|List]) ->
	{MscSide, StpSide, Comment} = Head,
	StpSideList = osmo_util:int2digit_list(StpSide),
	MscSideList = osmo_util:int2digit_list(MscSide),
	if PhoneNum == MscSideList ->
		NewPhoneNum = StpSideList,
		io:format("SCCP MSC->STP rewrite (~p) ~p -> ~p~n",
			  [Comment, PhoneNum, NewPhoneNum]),
		GT#global_title{phone_number = NewPhoneNum};
	   true ->
		do_sccp_gt_rewrite(GT, from_msc, List)
	end.

% mangle called address
mangle_rx_called(from_stp, Addr = #sccp_addr{global_title = GT}) ->
	{ok, RewriteTbl} = application:get_env(sccp_rewrite_tbl),
	GTout = do_sccp_gt_rewrite(GT, from_stp, RewriteTbl),
	Addr#sccp_addr{global_title = GTout};
mangle_rx_called(_From, Addr) ->
	Addr.

% mangle calling address
mangle_rx_calling(from_msc, Addr = #sccp_addr{global_title = GT}) ->
	{ok, RewriteTbl} = application:get_env(sccp_rewrite_tbl),
	GTout = do_sccp_gt_rewrite(GT, from_msc, RewriteTbl),
	Addr#sccp_addr{global_title = GTout};
mangle_rx_calling(_From, Addr) ->
	Addr.

maybe_re_encode(DecOrig, DecNew, MapEncOld) when DecOrig == DecNew ->
	MapEncOld;
maybe_re_encode(_DecOrig, DecNew, _MapEncOld) ->
	map_codec:encode_tcap_msg(DecNew).

% Mangle the SCCP Calling / Called Addresses
mangle_rx_sccp(From, _Path, ?SCCP_MSGT_UDT, Msg = #sccp_msg{parameters = Opts}) ->
	CalledParty = proplists:get_value(called_party_addr, Opts),
	CalledPartyNew = mangle_rx_called(From, CalledParty),
	CallingParty = proplists:get_value(calling_party_addr, Opts),
	CallingPartyNew = mangle_rx_calling(From, CallingParty),
	Opts1 = lists:keyreplace(called_party_addr, 1, Opts,
				 {called_party_addr, CalledPartyNew}),
	Opts2 = lists:keyreplace(calling_party_addr, 1, Opts1,
				 {calling_party_addr, CallingPartyNew}),
	Msg#sccp_msg{parameters = Opts2};
mangle_rx_sccp(_From, _Path, _MsgType, Msg) ->
	Msg.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Actual mangling of the decoded ISUP messages 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% iterate over list of parameters and call mangle_rx_isup_par() for each one
mangle_rx_isup_params(_From, _MsgType, _Msg, ParListOut, []) ->
	ParListOut;
mangle_rx_isup_params(From, MsgType, Msg, ParListOut, [Par|ParList]) ->
	ParOut = mangle_rx_isup_par(From, MsgType, Msg, Par),
	mangle_rx_isup_params(From, MsgType, Msg, ParListOut++[ParOut], ParList).

% manipulate phone numbers
mangle_rx_isup_par(From, MsgType, _Msg, {ParType, ParBody}) when
					ParType == ?ISUP_PAR_CALLED_P_NUM;
					ParType == ?ISUP_PAR_CONNECTED_NUM;
					ParType == ?ISUP_PAR_CALLING_P_NUM ->
	NewParBody = mangle_isup_number(From, MsgType, ParType, ParBody),
	{ParType, NewParBody};
% defauly case: do not mangle this parameter
mangle_rx_isup_par(_From, _MsgType, _Msg, Par) ->
	Par.

% mangle an incoming ISUP message
mangle_rx_isup(From, _Path, MsgType, Msg = #isup_msg{parameters = Params}) ->
	ParamsOut = mangle_rx_isup_params(From, MsgType, Msg, [], Params),
	% return message with modified parameter list
	Msg#isup_msg{parameters = ParamsOut}.

% STP->MSC: Mangle a Party Number in IAM
mangle_isup_number(from_stp, ?ISUP_MSGT_IAM, NumType, PartyNum) ->
	case NumType of
		?ISUP_PAR_CALLED_P_NUM ->
			% First convert to international number, if it is national
			{ok, InternPfx} = application:get_env(intern_pfx),
			{ok, MsrnPfxStp} = application:get_env(msrn_pfx_stp),
			{ok, MsrnPfxMsc} = application:get_env(msrn_pfx_msc),
			Num1 = isup_party_internationalize(PartyNum, InternPfx),
			io:format("IAM MSRN rewrite (STP->MSC): "),
			isup_party_replace_prefix(Num1, MsrnPfxStp, MsrnPfxMsc);
		?ISUP_PAR_CALLING_P_NUM ->
			isup_party_nat00_internationalize(PartyNum);
		_ ->
			PartyNum
	end;
% MSC->STP: Mangle connected number in response to IAM
mangle_isup_number(from_msc, MsgT, NumType, PartyNum) when MsgT == ?ISUP_MSGT_CON;
							   MsgT == ?ISUP_MSGT_ANM ->
	case NumType of
		?ISUP_PAR_CONNECTED_NUM ->
			{ok, InternPfx} = application:get_env(intern_pfx),
			{ok, MsrnPfxStp} = application:get_env(msrn_pfx_stp),
			{ok, MsrnPfxMsc} = application:get_env(msrn_pfx_msc),
			io:format("CON MSRN rewrite (MSC->STP): "),
			Num1 = isup_party_replace_prefix(PartyNum, MsrnPfxStp, MsrnPfxMsc),
			% Second: convert to national number, if it is international
			isup_party_nationalize(Num1, InternPfx);
		_ ->
			PartyNum
	end;
% MAC->STP: Mangle IAM international -> national
mangle_isup_number(from_msc, ?ISUP_MSGT_IAM, NumType, PartyNum) ->
	case NumType of
		?ISUP_PAR_CALLED_P_NUM ->
			{ok, InternPfx} = application:get_env(intern_pfx),
			isup_party_nationalize(PartyNum, InternPfx);
		_ ->
			PartyNum
	end;
% STP->MSC: Mangle connected number in response to IAM (national->international)
mangle_isup_number(from_stp, MsgT, NumType, PartyNum) when MsgT == ?ISUP_MSGT_CON;
							   MsgT == ?ISUP_MSGT_ANM ->
	case NumType of
		?ISUP_PAR_CONNECTED_NUM ->
			{ok, InternPfx} = application:get_env(intern_pfx),
			isup_party_internationalize(PartyNum, InternPfx);
		_ ->
			PartyNum
	end;
% default case: no rewrite
mangle_isup_number(from_msc, _, _, PartyNum) ->
	PartyNum.

% replace the prefix of PartyNum with NewPfx _if_ the current prefix matches MatchPfx
isup_party_replace_prefix(PartyNum, MatchPfxInt, NewPfxInt) ->
	DigitsIn = PartyNum#party_number.phone_number,
	NewPfx = osmo_util:int2digit_list(NewPfxInt),
	MatchPfx = osmo_util:int2digit_list(MatchPfxInt),
	MatchPfxLen = length(MatchPfx),
	Pfx = lists:sublist(DigitsIn, 1, MatchPfxLen),
	if Pfx == MatchPfx ->
		Trailer = lists:sublist(DigitsIn, MatchPfxLen+1, length(DigitsIn)-MatchPfxLen),
		DigitsOut = NewPfx ++ Trailer,
		io:format("Prefix rewrite: ~p -> ~p~n", [DigitsIn, DigitsOut]);
	   true ->
		io:format("Prefix rewrite: NO MATCH (~p != ~p)~n", [Pfx, MatchPfx]),
		DigitsOut = DigitsIn
	end,
	PartyNum#party_number{phone_number = DigitsOut}.

isup_party_internationalize(PartyNum, CountryCodeInt) ->
	#party_number{phone_number = DigitsIn, nature_of_addr_ind = Nature} = PartyNum,
	CountryCode = osmo_util:int2digit_list(CountryCodeInt),
	case Nature of
		?ISUP_ADDR_NAT_NATIONAL ->
			DigitsOut = CountryCode ++ DigitsIn,
			NatureOut = ?ISUP_ADDR_NAT_INTERNATIONAL,
			io:format("Internationalize: ~p -> ~p~n", [DigitsIn, DigitsOut]);
		_ ->
			DigitsOut = DigitsIn,
			NatureOut = Nature
	end,
	PartyNum#party_number{phone_number = DigitsOut, nature_of_addr_ind = NatureOut}.

% take something like {national, 00493024033902} and make {intl, 493024033902}
isup_party_nat00_internationalize(PartyNum) ->
	#party_number{phone_number = DigitsIn, nature_of_addr_ind = Nature} = PartyNum,
	case Nature of
		?ISUP_ADDR_NAT_NATIONAL ->
			{Pfx, Remain} = lists:split(2, DigitsIn),
			if Pfx == [0, 0] ->
				DigitsOut = Remain,
				NatureOut = ?ISUP_ADDR_NAT_INTERNATIONAL,
				io:format("National+00 -> International: ~p -> ~p~n",
					  [DigitsIn, DigitsOut]);
			   true ->
				DigitsOut = DigitsIn,
				NatureOut = Nature
			end;
		_ ->
			DigitsOut = DigitsIn,
			NatureOut = Nature
	end,
	PartyNum#party_number{phone_number = DigitsOut, nature_of_addr_ind = NatureOut}.

isup_party_nationalize(PartyNum, CountryCodeInt) ->
	#party_number{phone_number = DigitsIn, nature_of_addr_ind = Nature} = PartyNum,
	CountryCode = osmo_util:int2digit_list(CountryCodeInt),
	CountryCodeLen = length(CountryCode),
	case Nature of
		?ISUP_ADDR_NAT_INTERNATIONAL ->
			Pfx = lists:sublist(DigitsIn, CountryCodeLen),
			if Pfx == CountryCode ->
				DigitsOut = lists:sublist(DigitsIn, CountryCodeLen+1,
							  length(DigitsIn)-CountryCodeLen),
				NatureOut = ?ISUP_ADDR_NAT_NATIONAL,
				io:format("Nationalize: ~p -> ~p~n", [DigitsIn, DigitsOut]);
			   true ->
				DigitsOut = DigitsIn,
				NatureOut = Nature
			end;
		_ ->
			DigitsOut = DigitsIn,
			NatureOut = Nature
	end,
	PartyNum#party_number{phone_number = DigitsOut, nature_of_addr_ind = NatureOut}.