add new file implementing SCCP routing (no GTT yet)

1 files changed, 300 insertions, 0 deletions

diff --git a/src/sccp_routing.erl b/src/sccp_routing.erl
new file mode 100644
index 0000000..46c10a4
--- /dev/null
+++ b/src/sccp_routing.erl
@@ -0,0 +1,300 @@
+% SCCP routing code
+
+% (C) 2011 by Harald Welte <laforge@gnumonks.org>
+%
+% 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(sccp_routing).
+-author('Harald Welte <laforge@gnumonks.org>').
+
+-include_lib("osmo_ss7/include/osmo_util.hrl").
+-include_lib("osmo_ss7/include/sccp.hrl").
+-include_lib("osmo_ss7/include/mtp3.hrl").
+
+-export([route_mtp3_sccp_in/1, route_local_out/1]).
+
+pointcode_is_local(Pc) ->
+	% FIXME: use SCRC routing information
+	true.
+
+% local helper function
+msg_return_or_cr_refusal(SccpMsg, RetCause, RefCause) ->
+	case sccp_codec:is_connectionless(SccpMsg) of
+	   false ->
+		% if CL -> message return procedure
+		message_return(SccpMsg, RetCause);
+	   true ->
+		% if CR -> connection refusal
+		connection_refusal(SccpMsg, RefCause)
+	end.
+
+% local outgoing CL or CR message
+route_local_out(SccpMsg) when is_record(SccpMsg, sccp_msg) ->
+	CalledParty = proplists:get_value(called_party_addr, SccpMsg#sccp_msg.parameters),
+	#sccp_addr{global_title = Gt, ssn = Ssn, point_code = Pc} = CalledParty,
+	if
+	    (Gt == undefined) and ((Ssn == undefined) or (Ssn == 0)) ->
+		% left-most colunm of Table 1/Q714 -> Action four
+		Action = 4;
+	    (Gt /= undefined) and ((Ssn == undefined) or (Ssn == 0)) ->
+		% second (from left) column of Table 1/Q.714
+		if (Pc == undefined) ->
+			Action = 2;
+		   true ->
+			case pointcode_is_local(Pc) of
+			    true ->
+				Action = 2;
+			    false ->
+				Action = 3
+			end
+		end;
+	    (Gt == undefined) and (Ssn /= undefined) ->
+		% third (from left) column of Table 1/Q.714
+		if (Pc == undefined) ->
+			Action = 4;
+		   true ->
+			Action = 1
+		end;
+	    (Gt /= undefined) and (Ssn /= undefined) ->
+		% last (from left) column of Table 1/Q.714
+		if (Pc == undefined) ->
+			Action = 2;
+		   true ->
+			if CalledParty#sccp_addr.route_on_ssn ->
+				Action = 1;
+			   true ->
+				case pointcode_is_local(Pc) of
+				    true ->
+					Action = 2;
+				    false ->
+					Action = 3
+				end
+			end
+		end
+	end,
+	route_local_out_action(Action, SccpMsg, CalledParty).
+
+% Acccording to 2.3.2 Action (1)
+route_local_out_action(1, SccpMsg, CalledParty) ->
+	#sccp_addr{global_title = Gt, ssn = Ssn, point_code = Pc} = CalledParty,
+	case pointcode_is_local(Pc) of
+	    true ->
+		% c) procedures 2.3.1, item 2) are folloed
+		case sccp_user:local_ssn_avail(Ssn, Pc) of
+		    true ->
+			% pass to either SCOC or SCLC
+			{local, SccpMsg};
+		    false ->
+			% message return / connection refusal
+			msg_return_or_cr_refusal(SccpMsg,
+						 ?SCCP_CAUSE_RET_UNEQUIP_USER,
+						 ?SCCP_CAUSE_REF_UNEQUIPPED_USER)
+		end;
+	    false ->
+		% If the DPC is not the node itself and the remote DPC, SCCP
+		% and SSN are available, then the MTP-TRANSFER request
+		% primitive is invoked unless the compatibility test returns
+		% the message to SCLC or unless the message is discarded by the
+		% traffic limitation mechanism;
+		{remote, SccpMsg}
+	end;
+
+% Acccording to 2.3.2 Action (2)
+route_local_out_action(2, SccpMsg, CalledParty) ->
+	% perform GTT
+	case gtt() of
+	    undefined ->
+		% if CL -> message return procedure
+		% if CR -> connection refusal
+		msg_return_or_cr_refusal(SccpMsg,
+				?SCCP_CAUSE_RET_UNEQUIP_USER,
+				?SCCP_CAUSE_REF_UNEQUIPPED_USER);
+	    Dpc ->
+		case pointcode_is_local(Dpc) of
+		    true ->
+			% message is passed, based on the message type, to
+			% either SCOC or SCLC;
+			{local, SccpMsg};
+		    false ->
+			% MTP-TRANSFER request primitive is invoked unless the
+			% compatibility test returns the message to SCLC or
+			% unless the message is discarded by the traffic
+			% limitation mechanism
+			{remote, SccpMsg}
+		end
+	end;
+
+% Acccording to 2.3.2 Action (3)
+route_local_out_action(3, SccpMsg, CalledParty) ->
+	% The same actions as Action (1) apply, without checking the SSN.
+	% FIXME
+	ok;
+
+% Acccording to 2.3.2 Action (4)
+route_local_out_action(4, SccpMsg, CalledParty) ->
+	% insufficient information.
+	msg_return_or_cr_refusal(SccpMsg, ?SCCP_CAUSE_RET_NOTRANS_ADDR,
+					  ?SCCP_CAUSE_REF_DEST_UNKNOWN).
+
+
+
+route_cr_connless(Mtp3Msg, SccpMsg) when is_record(SccpMsg, sccp_msg) ->
+	CalledParty = proplists:get_value(called_party_addr, SccpMsg#sccp_msg.parameters),
+	case CalledParty#sccp_addr.route_on_ssn of
+	    1 -> % sheet 3 (6)
+		#sccp_addr{ssn = Ssn, point_code = Pc}= CalledParty,
+		% check if the subsystem is available (FIXME: move this into SCLC ?!?)
+		case sccp_user:pid_for_ssn(Ssn, Pc) of
+		    {ok, UserPid} ->
+			% forward to SCOC/SCLC
+			{local, SccpMsg, Mtp3Msg};
+		    {error, Error} ->
+			% invoke connection refusal (if CR) or message return
+			msg_return_or_cr_refusal(SccpMsg,
+						 ?SCCP_CAUSE_RET_UNEQUIP_USER,
+						 ?SCCP_CAUSE_REF_UNEQUIPPED_USER)
+		end;
+	    0 ->
+		% Check for hop counter and increment it
+		MsgPostHop = check_and_dec_hopctr(SccpMsg),
+		MsgClass = proplists:get_value(?SCCP_PNC_PROTOCOL_CLASS,
+						MsgPostHop#sccp_msg.parameters),
+		case MsgClass of
+		    0 ->
+			% FIXME: Assign SLS
+			ok;
+		    1 ->
+			% FIXME: Map incoming SLS to outgoing SLS
+			ok;
+		    _Default ->
+			ok
+		end,
+		% Optional screening function
+		% GTT needs to be performed
+		ok
+	end,
+	% FIXME: handle UDTS/XUDTS/LUDTS messages (RI=0 check) of C.1/Q.714 (1/12)
+	% FIXME: handle translation already performed == yes) case of C.1/Q.714 (1/12)
+	route_main(SccpMsg),
+	{remote}.
+
+
+% CR or connectionless message, coming in from MTP
+% return values
+%	{local, SccpMsg, Mtp3Msg}
+%	{remote}
+route_mtp3_sccp_in(Mtp3Msg) when is_record(Mtp3Msg, mtp3_msg) ->
+	{ok, Msg} = sccp_codec:parse_sccp_msg(Mtp3Msg#mtp3_msg.payload),
+        io:format("Parsed Msg: ~p~n", [Msg]),
+	case Msg of
+	    #sccp_msg{msg_type = ?SCCP_MSGT_CR} ->
+		route_cr_connless(Mtp3Msg, Msg);
+	    _ ->
+		case sccp_codec:is_connectionless(Msg) of
+		    true ->
+			route_cr_connless(Mtp3Msg, Msg);
+		    false ->
+			{local, Msg, Mtp3Msg}
+		end
+	end.
+
+% Check if the message has a hop counter; decrement it if yes.
+check_and_dec_hopctr(Msg = #sccp_msg{msg_type = MsgType}) when
+			MsgType == ?SCCP_MSGT_XUDT;
+			MsgType == ?SCCP_MSGT_XUDTS;
+			MsgType == ?SCCP_MSGT_LUDT;
+			MsgType == ?SCCP_MSGT_LUDTS;
+			MsgType == ?SCCP_MSGT_CR ->
+	HopCtr = proplists:get_value(?SCCP_PNC_HOP_COUNTER,
+				     Msg#sccp_msg.parameters),
+	if
+	    HopCtr =< 1 ->
+		% Error: Hop count expired
+		io:format("SCCP hop count expired~n"),
+		Msg;
+	    true ->
+		ParNew = lists:keyreplace(?SCCP_PNC_HOP_COUNTER, 1,
+					  Msg#sccp_msg.parameters,
+					  { ?SCCP_PNC_HOP_COUNTER, HopCtr -1}),
+		Msg#sccp_msg{parameters = ParNew}
+	end.
+
+route_main(SccpMsg) when is_record(SccpMsg, sccp_msg) ->
+	CalledParty = proplists:get_value(called_party_addr, SccpMsg#sccp_msg.parameters),
+	case CalledParty#sccp_addr.point_code of
+		undefined ->
+			fixme
+	end.
+
+
+% Message return procedure (Section 4.2 / Q.714)
+message_return(SccpMsg = #sccp_msg{msg_type = MsgType}, Cause) when
+			MsgType == ?SCCP_MSGT_XUDT;
+			MsgType == ?SCCP_MSGT_UDT;
+			MsgType == ?SCCP_MSGT_LUDT ->
+	% only return the message if the respective option is set
+	{Class, Opt} = proplists:get_value(protocol_class, SccpMsg#sccp_msg.parameters),
+	if Opt /= 8 ->
+		ok;
+	   true ->
+		RetMsg = gen_ret_msg(SccpMsg, Cause),
+		% FIXME: actually return it
+		ok
+	end;
+message_return(_Msg, _Reason) ->
+	ok.
+
+% transform UDT/LUDT/XUDT into UDTS/LUDTS/XUDTS
+gen_ret_msg(SccpMsg = #sccp_msg{msg_type = MsgType, parameters = Params}, Cause) ->
+	% extract information fields required
+	{Class, _Opt} = proplists:get_value(protocol_class, Params),
+	RetMsgType = message_return_type(MsgType),
+	CalledParty = proplists:get_value(called_party_addr, Params),
+	CallingParty = proplists:get_value(calling_party_addr, Params),
+	% build new options proplist
+	Params1 = lists:keyreplace(called_party_addr, 1, Params,
+				   {called_party_addr, CallingParty}),
+	Params2 = lists:keyreplace(calling_party_addr, 1, Params1,
+				   {calling_party_addr, CalledParty}),
+	Params3 = [{return_cause, Cause}, {protocol_class, {Class, 0}}] ++ Params2,
+	% return the new message
+	SccpMsg#sccp_msg{msg_type = RetMsgType,
+			 parameters = Params3}.
+
+connection_refusal(SccpMsg = #sccp_msg{msg_type = ?SCCP_MSGT_CR}, Cause) ->
+	CrefMsg = gen_cref_msg(SccpMsg, Cause),
+	% FIXME: actually return it
+	ok.
+
+gen_cref_msg(SccpMsg = #sccp_msg{msg_type = ?SCCP_MSGT_CR, parameters =
+		Params}, Cause) ->
+	CalledParty = proplists:get_value(called_party_addr, Params),
+	SrcLocalRef = proplists:get_value(src_local_ref, Params),
+	CrefParams = [{dst_local_ref, SrcLocalRef},
+		      {refusal_cause, Cause}],
+	% FIXME: what about class / data/ ... ?
+	#sccp_msg{msg_type = ?SCCP_MSGT_CREF, parameters = CrefParams}.
+
+message_return_type(?SCCP_MSGT_XUDT) ->
+	?SCCP_MSGT_XUDTS;
+message_return_type(?SCCP_MSGT_UDT) ->
+	?SCCP_MSGT_UDTS;
+message_return_type(?SCCP_MSGT_LUDT) ->
+	?SCCP_MSGT_LUDTS.
+
+% dummy for now, we don't do GTT yet
+gtt() ->
+	undefined.