module DIAMETER_Emulation {

/* DIAMETER Emulation, runs on top of DIAMETER_CodecPort.  It multiplexes/demultiplexes
 * the individual IMSIs/subscribers, so there can be separate TTCN-3 components handling
 * each of them.
 *
 * The DIAMETER_Emulation.main() function processes DIAMETER primitives from the DIAMETER
 * socket via the DIAMETER_CodecPort, and dispatches them to the per-IMSI components.
 *
 * For each new IMSI, the DiameterOps.create_cb() is called.  It can create
 * or resolve a TTCN-3 component, and returns a component reference to which that IMSI
 * is routed/dispatched.
 *
 * If a pre-existing component wants to register to handle a future inbound IMSI, it can
 * do so by registering an "expect" with the expected IMSI.
 *
 * Inbound DIAMETER messages without IMSI (such as RESET-IND/ACK) are dispatched to
 * the DiameterOps.unitdata_cb() callback, which is registered with an argument to the
 * main() function below.
 *
 * (C) 2019 by Harald Welte <laforge@gnumonks.org>
 * All rights reserved.
 *
 * Released under the terms of GNU General Public License, Version 2 or
 * (at your option) any later version.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

import from DIAMETER_CodecPort all;
import from DIAMETER_CodecPort_CtrlFunct all;
import from DIAMETER_Types all;
import from DIAMETER_Templates all;
import from Osmocom_Types all;
import from IPL4asp_Types all;
import from DNS_Helpers all;
import from MobileL3_Types all;

type hexstring IMSI;

type component DIAMETER_ConnHdlr {
	port DIAMETER_Conn_PT DIAMETER;
	/* procedure based port to register for incoming connections */
	port DIAMETEREM_PROC_PT DIAMETER_PROC;
}

/* port between individual per-connection components and this dispatcher */
type port DIAMETER_Conn_PT message {
	inout PDU_DIAMETER, PDU_ML3_MS_NW, PDU_ML3_NW_MS;
} with { extension "internal" };

/* global test port e.g. for non-imsi/conn specific messages */
type port DIAMETER_PT message {
	inout PDU_DIAMETER;
} with { extension "internal" };


/* represents a single DIAMETER Association */
type record AssociationData {
	DIAMETER_ConnHdlr	comp_ref,
	hexstring	imsi optional
};

type component DIAMETER_Emulation_CT {
	/* Port facing to the UDP SUT */
	port DIAMETER_CODEC_PT DIAMETER;
	/* All DIAMETER_ConnHdlr DIAMETER ports connect here
	 * DIAMETER_Emulation_CT.main needs to figure out what messages
	 * to send where with CLIENT.send() to vc_conn */
	port DIAMETER_Conn_PT DIAMETER_CLIENT;
	/* currently tracked connections */
	var AssociationData SgsapAssociationTable[16];
	/* pending expected CRCX */
	var ExpectData DiameterExpectTable[8];
	/* procedure based port to register for incoming connections */
	port DIAMETEREM_PROC_PT DIAMETER_PROC;
	/* test port for unit data messages */
	port DIAMETER_PT DIAMETER_UNIT;

	var charstring g_diameter_id;
	var integer g_diameter_conn_id := -1;
}

type function DIAMETERCreateCallback(PDU_DIAMETER msg, hexstring imsi, charstring id)
runs on DIAMETER_Emulation_CT return DIAMETER_ConnHdlr;

type function DIAMETERUnitdataCallback(PDU_DIAMETER msg)
runs on DIAMETER_Emulation_CT return template PDU_DIAMETER;

type record DIAMETEROps {
	DIAMETERCreateCallback create_cb,
	DIAMETERUnitdataCallback unitdata_cb
}

type record DIAMETER_conn_parameters {
	HostName remote_ip,
	PortNumber remote_sctp_port,
	HostName local_ip,
	PortNumber local_sctp_port
}

function tr_DIAMETER_RecvFrom_R(template PDU_DIAMETER msg)
runs on DIAMETER_Emulation_CT return template DIAMETER_RecvFrom {
	var template DIAMETER_RecvFrom mrf := {
		connId := g_diameter_conn_id,
		remName := ?,
		remPort := ?,
		locName := ?,
		locPort := ?,
		msg := msg
	}
	return mrf;
}

private function f_imsi_known(hexstring imsi)
runs on DIAMETER_Emulation_CT return boolean {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (SgsapAssociationTable[i].imsi == imsi) {
			return true;
		}
	}
	return false;
}

private function f_comp_known(DIAMETER_ConnHdlr client)
runs on DIAMETER_Emulation_CT return boolean {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (SgsapAssociationTable[i].comp_ref == client) {
			return true;
		}
	}
	return false;
}

private function f_comp_by_imsi(hexstring imsi)
runs on DIAMETER_Emulation_CT return DIAMETER_ConnHdlr {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (SgsapAssociationTable[i].imsi == imsi) {
			return SgsapAssociationTable[i].comp_ref;
		}
	}
	setverdict(fail, "DIAMETER Association Table not found by IMSI", imsi);
	mtc.stop;
}

private function f_imsi_by_comp(DIAMETER_ConnHdlr client)
runs on DIAMETER_Emulation_CT return hexstring {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (SgsapAssociationTable[i].comp_ref == client) {
			return SgsapAssociationTable[i].imsi;
		}
	}
	setverdict(fail, "DIAMETER Association Table not found by component ", client);
	mtc.stop;
}

private function f_imsi_table_add(DIAMETER_ConnHdlr comp_ref, hexstring imsi)
runs on DIAMETER_Emulation_CT {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (not isvalue(SgsapAssociationTable[i].imsi)) {
			SgsapAssociationTable[i].imsi := imsi;
			SgsapAssociationTable[i].comp_ref := comp_ref;
			return;
		}
	}
	testcase.stop("DIAMETER Association Table full!");
}

private function f_imsi_table_del(DIAMETER_ConnHdlr comp_ref, hexstring imsi)
runs on DIAMETER_Emulation_CT {
	var integer i;
	for (i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		if (SgsapAssociationTable[i].comp_ref == comp_ref and
		    SgsapAssociationTable[i].imsi == imsi) {
			SgsapAssociationTable[i].imsi := omit;
			SgsapAssociationTable[i].comp_ref := null;
			return;
		}
	}
	setverdict(fail, "DIAMETER Association Table: Couldn't find to-be-deleted entry!");
	mtc.stop;
}


private function f_imsi_table_init()
runs on DIAMETER_Emulation_CT {
	for (var integer i := 0; i < sizeof(SgsapAssociationTable); i := i+1) {
		SgsapAssociationTable[i].comp_ref := null;
		SgsapAssociationTable[i].imsi := omit;
	}
}

function f_DIAMETER_get_avp(PDU_DIAMETER pdu, template (present) AVP_Code avp_code)
return template (omit) AVP
{
	var integer i;

	for (i := 0; i < lengthof(pdu.avps); i := i+1) {
		if (not ispresent(pdu.avps[i].avp)) {
			continue;
		}
		var AVP_Header hdr := pdu.avps[i].avp.avp_header;
		if (match(hdr.avp_code, avp_code)) {
			return pdu.avps[i].avp;
		}
	}
	return omit;
}

function f_DIAMETER_get_imsi(PDU_DIAMETER pdu) return template (omit) IMSI
{
	var template (omit) AVP imsi_avp;

	imsi_avp := f_DIAMETER_get_avp(pdu, c_AVP_Code_BASE_NONE_User_Name);
	if (istemplatekind(imsi_avp, "omit")) {
		return omit;
	} else {
		var octetstring imsi_oct := valueof(imsi_avp.avp_data.avp_BASE_NONE_User_Name);
		return str2hex(oct2char(imsi_oct));
	}
}

private template (value) SctpTuple ts_SCTP(template (omit) integer ppid := omit) := {
	sinfo_stream := omit,
	sinfo_ppid := ppid,
	remSocks := omit,
	assocId := omit
};

private template PortEvent tr_SctpAssocChange := {
	sctpEvent := {
		sctpAssocChange := ?
	}
}
private template PortEvent tr_SctpPeerAddrChange := {
	sctpEvent := {
		sctpPeerAddrChange := ?
	}
}

private function f_diameter_xceive(template (value) PDU_DIAMETER tx,
				   template PDU_DIAMETER rx_t := ?)
runs on DIAMETER_Emulation_CT return PDU_DIAMETER {
	timer T := 10.0;
	var DIAMETER_RecvFrom mrf;

	DIAMETER.send(t_DIAMETER_Send(g_diameter_conn_id, tx));
	alt {
	[] DIAMETER.receive(tr_DIAMETER_RecvFrom_R(rx_t)) -> value mrf { }
	[] DIAMETER.receive(tr_SctpAssocChange) { repeat; }
	[] DIAMETER.receive(tr_SctpPeerAddrChange)  { repeat; }
	[] T.timeout {
		setverdict(fail, "Timeout waiting for ", rx_t);
		mtc.stop;
		}
	}
	return mrf.msg;
}

function main(DIAMETEROps ops, DIAMETER_conn_parameters p, charstring id) runs on DIAMETER_Emulation_CT {
	var Result res;
	g_diameter_id := id;
	f_imsi_table_init();
	f_expect_table_init();

	map(self:DIAMETER, system:DIAMETER_CODEC_PT);
	if (p.remote_sctp_port == -1) {
		res := DIAMETER_CodecPort_CtrlFunct.f_IPL4_listen(DIAMETER, p.local_ip, p.local_sctp_port, { sctp := valueof(ts_SCTP) });
	} else {
		res := DIAMETER_CodecPort_CtrlFunct.f_IPL4_connect(DIAMETER, p.remote_ip, p.remote_sctp_port,
								p.local_ip, p.local_sctp_port, -1, { sctp := valueof(ts_SCTP) });
	}
	if (not ispresent(res.connId)) {
		setverdict(fail, "Could not connect DIAMETER socket, check your configuration");
		mtc.stop;
	}
	g_diameter_conn_id := res.connId;

	while (true) {
		var DIAMETER_ConnHdlr vc_conn;
		var PDU_ML3_MS_NW l3_mo;
		var PDU_ML3_NW_MS l3_mt;
		var template IMSI imsi_t;
		var hexstring imsi;
		var DIAMETER_RecvFrom mrf;
		var PDU_DIAMETER msg;
		var charstring vlr_name, mme_name;
		var PortEvent port_evt;

		alt {
		[] DIAMETER.receive(PortEvent:{connOpened := ?}) -> value port_evt {
			g_diameter_conn_id := port_evt.connOpened.connId;
			}
		[] DIAMETER.receive(PortEvent:?) { }
		/* DIAMETER from client */
		[] DIAMETER_CLIENT.receive(PDU_DIAMETER:?) -> value msg sender vc_conn {
			/* Pass message through */
			/* TODO: check which ConnectionID client has allocated + store in table? */
			DIAMETER.send(t_DIAMETER_Send(g_diameter_conn_id, msg));
			}

		/* handle CER/CEA handshake */
		[] DIAMETER.receive(tr_DIAMETER_RecvFrom_R(tr_DIAMETER_R(cmd_code := Capabilities_Exchange))) -> value mrf {
			var template (value) PDU_DIAMETER resp;
			resp := ts_DIA_CEA(mrf.msg.hop_by_hop_id, mrf.msg.end_to_end_id);
			DIAMETER.send(t_DIAMETER_Send(g_diameter_conn_id, resp));
			}

		/* DIAMETER from remote peer */
		[] DIAMETER.receive(tr_DIAMETER_RecvFrom_R(?)) -> value mrf {
			imsi_t := f_DIAMETER_get_imsi(mrf.msg);
			if (isvalue(imsi_t)) {
				imsi := valueof(imsi_t);
				if (f_imsi_known(imsi)) {
					vc_conn := f_comp_by_imsi(imsi);
					DIAMETER_CLIENT.send(mrf.msg) to vc_conn;
				} else {
					vc_conn := ops.create_cb.apply(mrf.msg, imsi, id);
					f_imsi_table_add(vc_conn, imsi);
					DIAMETER_CLIENT.send(mrf.msg) to vc_conn;
				}
			} else {
				/* message contained no IMSI; is not IMSI-oriented */
				var template PDU_DIAMETER resp := ops.unitdata_cb.apply(mrf.msg);
				if (isvalue(resp)) {
					DIAMETER.send(t_DIAMETER_Send(g_diameter_conn_id, valueof(resp)));
				}
			}
			}
		[] DIAMETER.receive(tr_SctpAssocChange) { }
		[] DIAMETER.receive(tr_SctpPeerAddrChange)  { }
		[] DIAMETER_PROC.getcall(DIAMETEREM_register:{?,?}) -> param(imsi, vc_conn) {
			f_create_expect(imsi, vc_conn);
			DIAMETER_PROC.reply(DIAMETEREM_register:{imsi, vc_conn}) to vc_conn;
			}

		}

	}
}

/* "Expect" Handling */

type record ExpectData {
	hexstring imsi optional,
	DIAMETER_ConnHdlr vc_conn
}

signature DIAMETEREM_register(in hexstring imsi, in DIAMETER_ConnHdlr hdlr);

type port DIAMETEREM_PROC_PT procedure {
	inout DIAMETEREM_register;
} with { extension "internal" };

/* Function that can be used as create_cb and will usse the expect table */
function ExpectedCreateCallback(PDU_DIAMETER msg, hexstring imsi, charstring id)
runs on DIAMETER_Emulation_CT return DIAMETER_ConnHdlr {
	var DIAMETER_ConnHdlr ret := null;
	var integer i;

	for (i := 0; i < sizeof(DiameterExpectTable); i := i+1) {
		if (not ispresent(DiameterExpectTable[i].imsi)) {
			continue;
		}
		if (imsi == DiameterExpectTable[i].imsi) {
			ret := DiameterExpectTable[i].vc_conn;
			/* Release this entry */
			DiameterExpectTable[i].imsi := omit;
			DiameterExpectTable[i].vc_conn := null;
			log("Found Expect[", i, "] for ", msg, " handled at ", ret);
			return ret;
		}
	}
	setverdict(fail, "Couldn't find Expect for ", msg);
	mtc.stop;
}

private function f_create_expect(hexstring imsi, DIAMETER_ConnHdlr hdlr)
runs on DIAMETER_Emulation_CT {
	var integer i;

	/* Check an entry like this is not already presnt */
	for (i := 0; i < sizeof(DiameterExpectTable); i := i+1) {
		if (imsi == DiameterExpectTable[i].imsi) {
			setverdict(fail, "IMSI already present", imsi);
			mtc.stop;
		}
	}
	for (i := 0; i < sizeof(DiameterExpectTable); i := i+1) {
		if (not ispresent(DiameterExpectTable[i].imsi)) {
			DiameterExpectTable[i].imsi := imsi;
			DiameterExpectTable[i].vc_conn := hdlr;
			log("Created Expect[", i, "] for ", imsi, " to be handled at ", hdlr);
			return;
		}
	}
	testcase.stop("No space left in DiameterExpectTable")
}

/* client/conn_hdlr side function to use procedure port to create expect in emulation */
function f_diameter_expect(hexstring imsi) runs on DIAMETER_ConnHdlr {
	DIAMETER_PROC.call(DIAMETEREM_register:{imsi, self}) {
		[] DIAMETER_PROC.getreply(DIAMETEREM_register:{?,?}) {};
	}
}

private function f_expect_table_init()
runs on DIAMETER_Emulation_CT {
	var integer i;
	for (i := 0; i < sizeof(DiameterExpectTable); i := i + 1) {
		DiameterExpectTable[i].imsi := omit;
	}
}

function DummyUnitdataCallback(PDU_DIAMETER msg)
runs on DIAMETER_Emulation_CT return template PDU_DIAMETER {
	log("Ignoring DIAMETER ", msg);
	return omit;
}


}