src/m3ua_core.erl - erlang/osmo_ss7 - Gitiles

 % M3UA in accordance with RFC4666 (http://tools.ietf.org/html/rfc4666)

 % (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/>.
 %
 % Additional Permission under GNU AGPL version 3 section 7:
 %
 % If you modify this Program, or any covered work, by linking or
 % combining it with runtime libraries of Erlang/OTP as released by
 % Ericsson on http://www.erlang.org (or a modified version of these
 % libraries), containing parts covered by the terms of the Erlang Public
 % License (http://www.erlang.org/EPLICENSE), the licensors of this
 % Program grant you additional permission to convey the resulting work
 % without the need to license the runtime libraries of Erlang/OTP under
 % the GNU Affero General Public License. Corresponding Source for a
 % non-source form of such a combination shall include the source code
 % for the parts of the runtime libraries of Erlang/OTP used as well as
 % that of the covered work.

 -module(m3ua_core).
 -author('Harald Welte <laforge@gnumonks.org>').
 -behaviour(gen_fsm).

 -include_lib("kernel/include/inet_sctp.hrl").
 -include("osmo_util.hrl").
 -include("sccp.hrl").
 -include("m3ua.hrl").

 -export([start_link/1]).

 -export([init/1, terminate/3, code_change/4, handle_event/3, handle_info/3]).

 % FSM states:
 -export([asp_down/2, asp_inactive/2, asp_active/2]).

 -define(T_ACK_TIMEOUT, 2*60*100).

 % Loop Data
 -record(m3ua_state, {
 	  role,		% asp | sgp
 	  asp_state,	% down, inactive, active
 	  t_ack,
 	  user_fun,
 	  user_args,
 	  sctp_remote_ip,
 	  sctp_remote_port,
 	  sctp_sock,
 	  sctp_assoc_id
 	}).

 start_link(InitOpts) ->
 	gen_fsm:start_link(?MODULE, InitOpts, [{debug, [trace]}]).

 reconnect_sctp(L = #m3ua_state{sctp_remote_ip = Ip, sctp_remote_port = Port, sctp_sock = Sock}) ->
 	timer:sleep(1*1000),
 	io:format("SCTP Reconnect ~p:~p~n", [Ip, Port]),
 	InitMsg = #sctp_initmsg{num_ostreams = 2, max_instreams = 2},
 	case gen_sctp:connect(Sock, Ip, Port, [{active, once}, {reuseaddr, true},
 					       {sctp_initmsg, InitMsg}]) of
 		{ok, Assoc} ->
 			send_prim_to_user(L, osmo_util:make_prim('M','SCTP_ESTABLISH',confirm)),
 			L#m3ua_state{sctp_assoc_id = Assoc#sctp_assoc_change.assoc_id};
 		{error, Error } ->
 			io:format("SCTP Error ~p, reconnecting~n", [Error]),
 			reconnect_sctp(L)
 	end.

 build_openopt({sctp_local_port, Port}) ->
 	{port, Port};
 build_openopt({sctp_local_ip, undefined}) ->
 	[];
 build_openopt({sctp_local_ip, Ip}) ->
 	{ip, Ip};
 build_openopt(_) ->
 	[].
 build_openopts(PropList) ->
 	[{active, once}, {reuseaddr, true}] ++
 	lists:flatten(lists:map(fun build_openopt/1, PropList)).

 init(InitOpts) ->
 	{ok, SctpSock} = gen_sctp:open(build_openopts(InitOpts)),
 	LoopDat = #m3ua_state{role = asp, sctp_sock = SctpSock,
 				user_fun = proplists:get_value(user_fun, InitOpts),
 				user_args = proplists:get_value(user_args, InitOpts),
 				sctp_remote_ip = proplists:get_value(sctp_remote_ip, InitOpts),
 				sctp_remote_port = proplists:get_value(sctp_remote_port, InitOpts)},
 	LoopDat2 = reconnect_sctp(LoopDat),
 	{ok, asp_down, LoopDat2}.

 terminate(Reason, _State, LoopDat) ->
 	io:format("Terminating ~p (Reason: ~p)~n", [?MODULE, Reason]),
 	gen_sctp:close(LoopDat#m3ua_state.sctp_sock).

 code_change(_OldVsn, StateName, StateData, _Extra) ->
 	{ok, StateName, StateData}.

 % Helper function to send data to the SCTP peer
 send_sctp_to_peer(LoopDat, PktData, StreamId) when is_binary(PktData) ->
 	#m3ua_state{sctp_sock = Sock, sctp_assoc_id = Assoc} = LoopDat,
 	SndRcvInfo = #sctp_sndrcvinfo{assoc_id = Assoc, ppid = 3, stream = StreamId},
 	gen_sctp:send(Sock, SndRcvInfo, PktData).

 % same as above, but for un-encoded #m3ua_msg{}
 send_sctp_to_peer(LoopDat, M3uaMsg) when is_record(M3uaMsg, m3ua_msg) ->
 	MsgBin = m3ua_codec:encode_m3ua_msg(M3uaMsg),
 	StreamId = sctp_stream_for_m3ua(M3uaMsg),
 	send_sctp_to_peer(LoopDat, MsgBin, StreamId).

 % resolve the Stream ID depending on the m3ua_msg: 0 == management, 1 == trafic
 sctp_stream_for_m3ua(#m3ua_msg{msg_class = Class}) when
 				Class == ?M3UA_MSGC_TRANSFER ->
 	1;
 sctp_stream_for_m3ua(#m3ua_msg{}) ->
 	0.


 send_prim_to_user(LoopDat, Prim) when is_record(LoopDat, m3ua_state), is_record(Prim, primitive) ->
 	#m3ua_state{user_fun = Fun, user_args = Args} = LoopDat,
 	Fun(Prim, Args).

 % helper to send one of the up/down/act/inact management messages + start timer
 send_msg_start_tack(LoopDat, State, MsgClass, MsgType, Params) ->
 	% generate and send the respective message
 	Msg = #m3ua_msg{version = 1, msg_class = MsgClass, msg_type = MsgType, payload = Params},
 	send_sctp_to_peer(LoopDat, Msg),
 	% start T(ack) timer and wait for ASP_UP_ACK
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	{ok, Tack} = timer:apply_after(?T_ACK_TIMEOUT, gen_fsm, send_event,
 				 [self(), {timer_expired, t_ack, {MsgClass, MsgType, Params}}]),
 	{next_state, State, LoopDat#m3ua_state{t_ack = Tack}}.


 handle_event(Event, State, LoopDat) ->
 	io:format("Unknown Event ~p in state ~p~n", [Event, State]),
 	{next_state, State, LoopDat}.


 handle_info({sctp, Socket, _RemoteIp, _RemotePort, {ANC, SAC}},
 	     _State, LoopDat) when is_record(SAC, sctp_assoc_change) ->
 	io:format("SCTP Assoc Change ~p ~p~n", [ANC, SAC]),
 	#sctp_assoc_change{state = SacState, outbound_streams = _OutStreams,
 			   inbound_streams = _InStreams, assoc_id = _AssocId} = SAC,
 	case SacState of
 		comm_up ->
 			% primmitive to the user
 			send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_ESTABLISH',confirm)),
 			LoopDat2 = LoopDat;
 		comm_lost ->
 			send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
 			LoopDat2 = reconnect_sctp(LoopDat);
 		shutdown_comp ->
 			send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
 			LoopDat2 = reconnect_sctp(LoopDat);
 		addr_unreachable ->
 			LoopDat2 = reconnect_sctp(LoopDat)
 	end,
 	inet:setopts(Socket, [{active, once}]),
 	{next_state, asp_down, LoopDat2};

 handle_info({sctp, Socket, _RemoteIp, _RemotePort, {ANC, SPC}},
 	     State, LoopDat) when is_record(SPC, sctp_paddr_change) ->
 	io:format("SCTP Peer address change ~p ~p~n", [ANC, SPC]),
 	{NewState, LoopDat2} = case SPC#sctp_paddr_change.state of
 		addr_available ->
 			% we don't care
 			{State, LoopDat};
 		addr_unreachable ->
 			send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
 			{asp_down, reconnect_sctp(LoopDat)};
 		addr_removed ->
 			% FIXME: what if the last one is removed
 			{State, LoopDat};
 		addr_added ->
 			% we don't care
 			{State, LoopDat};
 		addr_made_prim ->
 			% FIXME: do we need to change remote_ip in our LoopDat?
 			{State, LoopDat}
 	end,
 	inet:setopts(Socket, [{active, once}]),
 	{next_state, NewState, LoopDat2};

 handle_info({sctp, Socket, RemoteIp, RemotePort, {[Anc], Data}}, State, LoopDat) ->
 	io:format("SCTP rx data: ~p ~p~n", [Anc, Data]),
 	% process incoming SCTP data
 	if Socket == LoopDat#m3ua_state.sctp_sock,
 	   RemoteIp == LoopDat#m3ua_state.sctp_remote_ip,
 	   RemotePort == LoopDat#m3ua_state.sctp_remote_port,
 	   3 == Anc#sctp_sndrcvinfo.ppid ->
 		Ret = rx_sctp(Anc, Data, State, LoopDat);
 	   true ->
 		io:format("unknown SCTP: ~p ~p~n", [Anc, Data]),
 		Ret = {next_state, State, LoopDat}
 	end,
 	inet:setopts(Socket, [{active, once}]),
 	Ret;

 handle_info({sctp, Socket, RemoteIp, RemotePort, {_Anc, Data}}, _State, LoopDat)
 					when is_record(Data, sctp_shutdown_event) ->
 	io:format("SCTP remote ~p:~p shutdown~n", [RemoteIp, RemotePort]),
 	inet:setopts(Socket, [{active, once}]),
 	{next_state, asp_down, LoopDat}.


 asp_down(#primitive{subsystem = 'M', gen_name = 'ASP_UP',
 		    spec_name = request, parameters = _Params}, LoopDat) ->
 	% M-ASP_UP.req from user, generate message and send to remote peer
 	send_msg_start_tack(LoopDat, asp_down, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, []);
 asp_down({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, Params}}, LoopDat) ->
 	send_msg_start_tack(LoopDat, asp_down, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, Params);

 asp_down(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
 		   msg_type = ?M3UA_MSGT_ASPSM_ASPUP_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition into ASP_INACTIVE
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_UP',confirm)),
 	{next_state, asp_inactive, LoopDat};

 asp_down(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
 	rx_m3ua(M3uaMsg, asp_down, LoopDat).


 asp_inactive(#primitive{subsystem = 'M', gen_name = 'ASP_ACTIVE',
 			spec_name = request, parameters = _Params}, LoopDat) ->
 	% M-ASP_ACTIVE.req from user, generate message and send to remote peer
 	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC,
 			   [{?M3UA_IEI_TRAF_MODE_TYPE, <<0,0,0,1>>}]);

 asp_inactive({timer_expired, t_ack, {?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC, Params}}, LoopDat) ->
 	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC, Params);

 asp_inactive(#primitive{subsystem = 'M', gen_name = 'ASP_DOWN',
 		      spec_name = request, parameters = _Params}, LoopDat) ->
 	% M-ASP_DOWN.req from user, generate message and send to remote peer
 	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, []);

 asp_inactive({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params}}, LoopDat) ->
 	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params);

 asp_inactive(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
 		       msg_type = ?M3UA_MSGT_ASPTM_ASPAC_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition into ASP_ACTIVE
 	% signal this to the user
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_ACTIVE',confirm)),
 	{next_state, asp_active, LoopDat};

 asp_inactive(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
 		       msg_type = ?M3UA_MSGT_ASPSM_ASPDN_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition into ASP_DOWN
 	% signal this to the user
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_DOWN',confirm)),
 	{next_state, asp_down, LoopDat};

 asp_inactive(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
 	rx_m3ua(M3uaMsg, asp_inactive, LoopDat).


 asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
 		     msg_type = ?M3UA_MSGT_ASPSM_ASPDN_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition into ASP_DOWN
 	% signal this to the user
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_DOWN',confirm)),
 	{next_state, asp_down, LoopDat};

 asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
 		     msg_type = ?M3UA_MSGT_ASPTM_ASPIA_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition into ASP_INACTIVE
 	% signal this to the user
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_INACTIVE',confirm)),
 	{next_state, asp_inactive, LoopDat};

 asp_active(#primitive{subsystem = 'M', gen_name = 'ASP_DOWN',
 		      spec_name = request, parameters = _Params}, LoopDat) ->
 	% M-ASP_DOWN.req from user, generate message and send to remote peer
 	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, []);

 asp_active({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params}}, LoopDat) ->
 	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params);

 asp_active(#primitive{subsystem = 'M', gen_name = 'ASP_INACTIVE',
 		      spec_name = request, parameters = _Params}, LoopDat) ->
 	% M-ASP_INACTIVE.req from user, generate message and send to remote peer
 	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, []);

 asp_active({timer_expired, t_ack, {?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, Params}}, LoopDat) ->
 	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, Params);

 asp_active(#primitive{subsystem = 'MTP', gen_name = 'TRANSFER',
 		      spec_name = request, parameters = Params}, LoopDat) ->
 	% MTP-TRANSFER.req from user app: Send message to remote peer
 	OptList = [{?M3UA_IEI_PROTOCOL_DATA, Params}],
 	Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_TRANSFER,
 			msg_type = ?M3UA_MSGT_XFR_DATA,
 			payload = OptList},
 	send_sctp_to_peer(LoopDat, Msg),
 	{next_state, asp_active, LoopDat};
 asp_active(#m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_TRANSFER,
 		     msg_type = ?M3UA_MSGT_XFR_DATA, payload = Params}, LoopDat) ->
 	% Data transfer from remote entity: Send MTP-TRANSFER.ind primitive to the user
 	Mtp3 = proplists:get_value(?M3UA_IEI_PROTOCOL_DATA, Params),
 	send_prim_to_user(LoopDat, osmo_util:make_prim('MTP','TRANSFER',indication,Mtp3)),
 	{next_state, asp_active, LoopDat};
 asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
 		     msg_type = ?M3UA_MSGT_ASPTM_ASPIA_ACK}, LoopDat) ->
 	timer:cancel(LoopDat#m3ua_state.t_ack),
 	% transition to ASP_INACTIVE
         {next_state, asp_inactive, LoopDat};

 asp_active(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
 	rx_m3ua(M3uaMsg, asp_active, LoopDat).


 rx_sctp(_Anc, Data, State, LoopDat) ->
 	M3uaMsg = m3ua_codec:parse_m3ua_msg(Data),
 	gen_fsm:send_event(self(), M3uaMsg),
 	{next_state, State, LoopDat}.


 rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_MGMT,
 			msg_type = ?M3UA_MSGT_MGMT_NTFY}, State, LoopDat) ->
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','NOTIFY',indication,[Msg])),
 	{next_state, State, LoopDat};

 rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_ASPSM,
 			msg_type = ?M3UA_MSGT_ASPSM_BEAT}, State, LoopDat) ->
 	% Send BEAT_ACK using the same payload as the BEAT msg
 	send_sctp_to_peer(LoopDat, Msg#m3ua_msg{msg_type = ?M3UA_MSGT_ASPSM_BEAT_ACK}),
 	{next_state, State, LoopDat};

 rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_MGMT,
 			msg_type = ?M3UA_MSGT_MGMT_ERR}, State, LoopDat) ->
 	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ERROR',indication,[Msg])),
 	{next_state, State, LoopDat};

 rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_SSNM,
 		        msg_type = MsgType, payload = Params}, State, LoopDat) ->
 	% transform to classic MTP primitive and send up to the user
 	Mtp = map_ssnm_to_mtp_prim(MsgType),
 	send_prim_to_user(LoopDat, Mtp),
 	{next_state, State, LoopDat};

 rx_m3ua(Msg = #m3ua_msg{}, State, LoopDat) ->
 	io:format("M3UA Unknown messge ~p in state ~p~n", [Msg, State]),
 	{next_state, State, LoopDat}.

 % Transform the M3UA SSNM messages into classic MTP primitives
 map_ssnm_to_mtp_prim(MsgType) ->
 	Mtp = #primitive{subsystem = 'MTP', spec_name = indication},
 	case MsgType of
 	    ?M3UA_MSGT_SSNM_DUNA -> Mtp#primitive{gen_name = 'PAUSE'};
 	    ?M3UA_MSGT_SSNM_DAVA -> Mtp#primitive{gen_name = 'RESUME'};
 	    ?M3UA_MSGT_SSNM_SCON -> Mtp#primitive{gen_name = 'STATUS'};
 	    ?M3UA_MSGT_SSNM_DUPU -> Mtp#primitive{gen_name = 'STATUS'}
 	end.
	% M3UA in accordance with RFC4666 (http://tools.ietf.org/html/rfc4666)

	% (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/>.
	%
	% Additional Permission under GNU AGPL version 3 section 7:
	%
	% If you modify this Program, or any covered work, by linking or
	% combining it with runtime libraries of Erlang/OTP as released by
	% Ericsson on http://www.erlang.org (or a modified version of these
	% libraries), containing parts covered by the terms of the Erlang Public
	% License (http://www.erlang.org/EPLICENSE), the licensors of this
	% Program grant you additional permission to convey the resulting work
	% without the need to license the runtime libraries of Erlang/OTP under
	% the GNU Affero General Public License. Corresponding Source for a
	% non-source form of such a combination shall include the source code
	% for the parts of the runtime libraries of Erlang/OTP used as well as
	% that of the covered work.

	-module(m3ua_core).
	-author('Harald Welte <laforge@gnumonks.org>').
	-behaviour(gen_fsm).

	-include_lib("kernel/include/inet_sctp.hrl").
	-include("osmo_util.hrl").
	-include("sccp.hrl").
	-include("m3ua.hrl").

	-export([start_link/1]).

	-export([init/1, terminate/3, code_change/4, handle_event/3, handle_info/3]).

	% FSM states:
	-export([asp_down/2, asp_inactive/2, asp_active/2]).

	-define(T_ACK_TIMEOUT, 260100).

	% Loop Data
	-record(m3ua_state, {
	role, % asp \| sgp
	asp_state, % down, inactive, active
	t_ack,
	user_fun,
	user_args,
	sctp_remote_ip,
	sctp_remote_port,
	sctp_sock,
	sctp_assoc_id
	}).

	start_link(InitOpts) ->
	gen_fsm:start_link(?MODULE, InitOpts, [{debug, [trace]}]).

	reconnect_sctp(L = #m3ua_state{sctp_remote_ip = Ip, sctp_remote_port = Port, sctp_sock = Sock}) ->
	timer:sleep(1*1000),
	io:format("SCTP Reconnect ~p:~p~n", [Ip, Port]),
	InitMsg = #sctp_initmsg{num_ostreams = 2, max_instreams = 2},
	case gen_sctp:connect(Sock, Ip, Port, [{active, once}, {reuseaddr, true},
	{sctp_initmsg, InitMsg}]) of
	{ok, Assoc} ->
	send_prim_to_user(L, osmo_util:make_prim('M','SCTP_ESTABLISH',confirm)),
	L#m3ua_state{sctp_assoc_id = Assoc#sctp_assoc_change.assoc_id};
	{error, Error } ->
	io:format("SCTP Error ~p, reconnecting~n", [Error]),
	reconnect_sctp(L)
	end.

	build_openopt({sctp_local_port, Port}) ->
	{port, Port};
	build_openopt({sctp_local_ip, undefined}) ->
	[];
	build_openopt({sctp_local_ip, Ip}) ->
	{ip, Ip};
	build_openopt(_) ->
	[].
	build_openopts(PropList) ->
	[{active, once}, {reuseaddr, true}] ++
	lists:flatten(lists:map(fun build_openopt/1, PropList)).

	init(InitOpts) ->
	{ok, SctpSock} = gen_sctp:open(build_openopts(InitOpts)),
	LoopDat = #m3ua_state{role = asp, sctp_sock = SctpSock,
	user_fun = proplists:get_value(user_fun, InitOpts),
	user_args = proplists:get_value(user_args, InitOpts),
	sctp_remote_ip = proplists:get_value(sctp_remote_ip, InitOpts),
	sctp_remote_port = proplists:get_value(sctp_remote_port, InitOpts)},
	LoopDat2 = reconnect_sctp(LoopDat),
	{ok, asp_down, LoopDat2}.

	terminate(Reason, _State, LoopDat) ->
	io:format("Terminating ~p (Reason: ~p)~n", [?MODULE, Reason]),
	gen_sctp:close(LoopDat#m3ua_state.sctp_sock).

	code_change(_OldVsn, StateName, StateData, _Extra) ->
	{ok, StateName, StateData}.

	% Helper function to send data to the SCTP peer
	send_sctp_to_peer(LoopDat, PktData, StreamId) when is_binary(PktData) ->
	#m3ua_state{sctp_sock = Sock, sctp_assoc_id = Assoc} = LoopDat,
	SndRcvInfo = #sctp_sndrcvinfo{assoc_id = Assoc, ppid = 3, stream = StreamId},
	gen_sctp:send(Sock, SndRcvInfo, PktData).

	% same as above, but for un-encoded #m3ua_msg{}
	send_sctp_to_peer(LoopDat, M3uaMsg) when is_record(M3uaMsg, m3ua_msg) ->
	MsgBin = m3ua_codec:encode_m3ua_msg(M3uaMsg),
	StreamId = sctp_stream_for_m3ua(M3uaMsg),
	send_sctp_to_peer(LoopDat, MsgBin, StreamId).

	% resolve the Stream ID depending on the m3ua_msg: 0 == management, 1 == trafic
	sctp_stream_for_m3ua(#m3ua_msg{msg_class = Class}) when
	Class == ?M3UA_MSGC_TRANSFER ->
	1;
	sctp_stream_for_m3ua(#m3ua_msg{}) ->
	0.


	send_prim_to_user(LoopDat, Prim) when is_record(LoopDat, m3ua_state), is_record(Prim, primitive) ->
	#m3ua_state{user_fun = Fun, user_args = Args} = LoopDat,
	Fun(Prim, Args).

	% helper to send one of the up/down/act/inact management messages + start timer
	send_msg_start_tack(LoopDat, State, MsgClass, MsgType, Params) ->
	% generate and send the respective message
	Msg = #m3ua_msg{version = 1, msg_class = MsgClass, msg_type = MsgType, payload = Params},
	send_sctp_to_peer(LoopDat, Msg),
	% start T(ack) timer and wait for ASP_UP_ACK
	timer:cancel(LoopDat#m3ua_state.t_ack),
	{ok, Tack} = timer:apply_after(?T_ACK_TIMEOUT, gen_fsm, send_event,
	[self(), {timer_expired, t_ack, {MsgClass, MsgType, Params}}]),
	{next_state, State, LoopDat#m3ua_state{t_ack = Tack}}.



	handle_event(Event, State, LoopDat) ->
	io:format("Unknown Event ~p in state ~p~n", [Event, State]),
	{next_state, State, LoopDat}.



	handle_info({sctp, Socket, _RemoteIp, _RemotePort, {ANC, SAC}},
	_State, LoopDat) when is_record(SAC, sctp_assoc_change) ->
	io:format("SCTP Assoc Change ~p ~p~n", [ANC, SAC]),
	#sctp_assoc_change{state = SacState, outbound_streams = _OutStreams,
	inbound_streams = _InStreams, assoc_id = _AssocId} = SAC,
	case SacState of
	comm_up ->
	% primmitive to the user
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_ESTABLISH',confirm)),
	LoopDat2 = LoopDat;
	comm_lost ->
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
	LoopDat2 = reconnect_sctp(LoopDat);
	shutdown_comp ->
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
	LoopDat2 = reconnect_sctp(LoopDat);
	addr_unreachable ->
	LoopDat2 = reconnect_sctp(LoopDat)
	end,
	inet:setopts(Socket, [{active, once}]),
	{next_state, asp_down, LoopDat2};

	handle_info({sctp, Socket, _RemoteIp, _RemotePort, {ANC, SPC}},
	State, LoopDat) when is_record(SPC, sctp_paddr_change) ->
	io:format("SCTP Peer address change ~p ~p~n", [ANC, SPC]),
	{NewState, LoopDat2} = case SPC#sctp_paddr_change.state of
	addr_available ->
	% we don't care
	{State, LoopDat};
	addr_unreachable ->
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','SCTP_RELEASE',indication)),
	{asp_down, reconnect_sctp(LoopDat)};
	addr_removed ->
	% FIXME: what if the last one is removed
	{State, LoopDat};
	addr_added ->
	% we don't care
	{State, LoopDat};
	addr_made_prim ->
	% FIXME: do we need to change remote_ip in our LoopDat?
	{State, LoopDat}
	end,
	inet:setopts(Socket, [{active, once}]),
	{next_state, NewState, LoopDat2};

	handle_info({sctp, Socket, RemoteIp, RemotePort, {[Anc], Data}}, State, LoopDat) ->
	io:format("SCTP rx data: ~p ~p~n", [Anc, Data]),
	% process incoming SCTP data
	if Socket == LoopDat#m3ua_state.sctp_sock,
	RemoteIp == LoopDat#m3ua_state.sctp_remote_ip,
	RemotePort == LoopDat#m3ua_state.sctp_remote_port,
	3 == Anc#sctp_sndrcvinfo.ppid ->
	Ret = rx_sctp(Anc, Data, State, LoopDat);
	true ->
	io:format("unknown SCTP: ~p ~p~n", [Anc, Data]),
	Ret = {next_state, State, LoopDat}
	end,
	inet:setopts(Socket, [{active, once}]),
	Ret;

	handle_info({sctp, Socket, RemoteIp, RemotePort, {_Anc, Data}}, _State, LoopDat)
	when is_record(Data, sctp_shutdown_event) ->
	io:format("SCTP remote ~p:~p shutdown~n", [RemoteIp, RemotePort]),
	inet:setopts(Socket, [{active, once}]),
	{next_state, asp_down, LoopDat}.



	asp_down(#primitive{subsystem = 'M', gen_name = 'ASP_UP',
	spec_name = request, parameters = _Params}, LoopDat) ->
	% M-ASP_UP.req from user, generate message and send to remote peer
	send_msg_start_tack(LoopDat, asp_down, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, []);
	asp_down({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, Params}}, LoopDat) ->
	send_msg_start_tack(LoopDat, asp_down, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPUP, Params);

	asp_down(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
	msg_type = ?M3UA_MSGT_ASPSM_ASPUP_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition into ASP_INACTIVE
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_UP',confirm)),
	{next_state, asp_inactive, LoopDat};

	asp_down(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
	rx_m3ua(M3uaMsg, asp_down, LoopDat).


	asp_inactive(#primitive{subsystem = 'M', gen_name = 'ASP_ACTIVE',
	spec_name = request, parameters = _Params}, LoopDat) ->
	% M-ASP_ACTIVE.req from user, generate message and send to remote peer
	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC,
	[{?M3UA_IEI_TRAF_MODE_TYPE, <<0,0,0,1>>}]);

	asp_inactive({timer_expired, t_ack, {?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC, Params}}, LoopDat) ->
	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPAC, Params);

	asp_inactive(#primitive{subsystem = 'M', gen_name = 'ASP_DOWN',
	spec_name = request, parameters = _Params}, LoopDat) ->
	% M-ASP_DOWN.req from user, generate message and send to remote peer
	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, []);

	asp_inactive({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params}}, LoopDat) ->
	send_msg_start_tack(LoopDat, asp_inactive, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params);

	asp_inactive(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
	msg_type = ?M3UA_MSGT_ASPTM_ASPAC_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition into ASP_ACTIVE
	% signal this to the user
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_ACTIVE',confirm)),
	{next_state, asp_active, LoopDat};

	asp_inactive(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
	msg_type = ?M3UA_MSGT_ASPSM_ASPDN_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition into ASP_DOWN
	% signal this to the user
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_DOWN',confirm)),
	{next_state, asp_down, LoopDat};

	asp_inactive(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
	rx_m3ua(M3uaMsg, asp_inactive, LoopDat).



	asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPSM,
	msg_type = ?M3UA_MSGT_ASPSM_ASPDN_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition into ASP_DOWN
	% signal this to the user
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_DOWN',confirm)),
	{next_state, asp_down, LoopDat};

	asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
	msg_type = ?M3UA_MSGT_ASPTM_ASPIA_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition into ASP_INACTIVE
	% signal this to the user
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ASP_INACTIVE',confirm)),
	{next_state, asp_inactive, LoopDat};

	asp_active(#primitive{subsystem = 'M', gen_name = 'ASP_DOWN',
	spec_name = request, parameters = _Params}, LoopDat) ->
	% M-ASP_DOWN.req from user, generate message and send to remote peer
	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, []);

	asp_active({timer_expired, t_ack, {?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params}}, LoopDat) ->
	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPSM, ?M3UA_MSGT_ASPSM_ASPDN, Params);

	asp_active(#primitive{subsystem = 'M', gen_name = 'ASP_INACTIVE',
	spec_name = request, parameters = _Params}, LoopDat) ->
	% M-ASP_INACTIVE.req from user, generate message and send to remote peer
	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, []);

	asp_active({timer_expired, t_ack, {?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, Params}}, LoopDat) ->
	send_msg_start_tack(LoopDat, asp_active, ?M3UA_MSGC_ASPTM, ?M3UA_MSGT_ASPTM_ASPIA, Params);

	asp_active(#primitive{subsystem = 'MTP', gen_name = 'TRANSFER',
	spec_name = request, parameters = Params}, LoopDat) ->
	% MTP-TRANSFER.req from user app: Send message to remote peer
	OptList = [{?M3UA_IEI_PROTOCOL_DATA, Params}],
	Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_TRANSFER,
	msg_type = ?M3UA_MSGT_XFR_DATA,
	payload = OptList},
	send_sctp_to_peer(LoopDat, Msg),
	{next_state, asp_active, LoopDat};
	asp_active(#m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_TRANSFER,
	msg_type = ?M3UA_MSGT_XFR_DATA, payload = Params}, LoopDat) ->
	% Data transfer from remote entity: Send MTP-TRANSFER.ind primitive to the user
	Mtp3 = proplists:get_value(?M3UA_IEI_PROTOCOL_DATA, Params),
	send_prim_to_user(LoopDat, osmo_util:make_prim('MTP','TRANSFER',indication,Mtp3)),
	{next_state, asp_active, LoopDat};
	asp_active(#m3ua_msg{msg_class = ?M3UA_MSGC_ASPTM,
	msg_type = ?M3UA_MSGT_ASPTM_ASPIA_ACK}, LoopDat) ->
	timer:cancel(LoopDat#m3ua_state.t_ack),
	% transition to ASP_INACTIVE
	{next_state, asp_inactive, LoopDat};

	asp_active(M3uaMsg, LoopDat) when is_record(M3uaMsg, m3ua_msg) ->
	rx_m3ua(M3uaMsg, asp_active, LoopDat).



	rx_sctp(_Anc, Data, State, LoopDat) ->
	M3uaMsg = m3ua_codec:parse_m3ua_msg(Data),
	gen_fsm:send_event(self(), M3uaMsg),
	{next_state, State, LoopDat}.



	rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_MGMT,
	msg_type = ?M3UA_MSGT_MGMT_NTFY}, State, LoopDat) ->
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','NOTIFY',indication,[Msg])),
	{next_state, State, LoopDat};

	rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_ASPSM,
	msg_type = ?M3UA_MSGT_ASPSM_BEAT}, State, LoopDat) ->
	% Send BEAT_ACK using the same payload as the BEAT msg
	send_sctp_to_peer(LoopDat, Msg#m3ua_msg{msg_type = ?M3UA_MSGT_ASPSM_BEAT_ACK}),
	{next_state, State, LoopDat};

	rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_MGMT,
	msg_type = ?M3UA_MSGT_MGMT_ERR}, State, LoopDat) ->
	send_prim_to_user(LoopDat, osmo_util:make_prim('M','ERROR',indication,[Msg])),
	{next_state, State, LoopDat};

	rx_m3ua(Msg = #m3ua_msg{version = 1, msg_class = ?M3UA_MSGC_SSNM,
	msg_type = MsgType, payload = Params}, State, LoopDat) ->
	% transform to classic MTP primitive and send up to the user
	Mtp = map_ssnm_to_mtp_prim(MsgType),
	send_prim_to_user(LoopDat, Mtp),
	{next_state, State, LoopDat};

	rx_m3ua(Msg = #m3ua_msg{}, State, LoopDat) ->
	io:format("M3UA Unknown messge ~p in state ~p~n", [Msg, State]),
	{next_state, State, LoopDat}.

	% Transform the M3UA SSNM messages into classic MTP primitives
	map_ssnm_to_mtp_prim(MsgType) ->
	Mtp = #primitive{subsystem = 'MTP', spec_name = indication},
	case MsgType of
	?M3UA_MSGT_SSNM_DUNA -> Mtp#primitive{gen_name = 'PAUSE'};
	?M3UA_MSGT_SSNM_DAVA -> Mtp#primitive{gen_name = 'RESUME'};
	?M3UA_MSGT_SSNM_SCON -> Mtp#primitive{gen_name = 'STATUS'};
	?M3UA_MSGT_SSNM_DUPU -> Mtp#primitive{gen_name = 'STATUS'}
	end.