/* NS Provider for NS/UDP/IP
 * (C) 2020-2021 Harald Welte <laforge@gnumonks.org>
 * contributions by sysmocom - s.f.m.c. GmbH
 * 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
 */

/* This provider can be operated in two modes:
 *
 * 1) the "classic" mode, where - similar to the NS_Provider_FR - there is
 *    only one NSVC per provider.  In this mode, the "NSE" port is used to
 *    exchange data with the next higher level component, such as a NSVC_CT
 *    or a RAW_NS_CT.
 *
 * 2) the enew "endpoint" mode, where one provider can host a number of different
 *    NSVCs.  This is needed in most non-trivial IP-SNS scenarios.   The 'NSE'
 *    port of this component is no longer used.  Instead, there is a NSVC port
 *    array, one of which will be used for each NSVC.   The NSVCs are dynamically
 *    added and removed via the PROC procedure port, controlled by NS_CT.
 */

module NS_Provider_IPL4 {

import from Misc_Helpers all;
import from NS_Emulation all;
import from NS_Types all;

import from IPL4asp_Types all;
import from IPL4asp_PortType all;

/* maximum number of NS-VCs within one Provider (== IP endpoint) */
private const integer NUM_MAX_NSVC := 16;

type component NS_Provider_IPL4_CT extends NS_Provider_CT {
	/* down-facing port towards IPL4asp to IUT */
	port IPL4asp_PT IPL4;
	var integer g_conn_id := -1;

	/* per-NSVC ports and state */
	port NS_PROVIDER_PT NSVC[NUM_MAX_NSVC];
	var PerNsvcState g_nsvc[NUM_MAX_NSVC];

	/* management port via which  */
	port NSPIP_PROC_PT PROC;
};

type record PerNsvcState {
	charstring remote_ip,
	PortNumber remote_port,
	NSVC_CT	vc_nsvc
};

signature NSPIP_add_nsvc(charstring remote_ip, PortNumber remote_port, NSVC_CT vc_nsvc);
signature NSPIP_del_nsvc(charstring remote_ip, PortNumber remote_port);

type port NSPIP_PROC_PT procedure {
	inout NSPIP_add_nsvc, NSPIP_del_nsvc;
} with { extension "internal" };

/* add a new NSVC to the provider */
private function f_nsvc_add(PerNsvcState nsvc) runs on NS_Provider_IPL4_CT
{
	for (var integer i := 0; i < sizeof(g_nsvc); i := i+1) {
		if (g_nsvc[i].vc_nsvc == null) {
			g_nsvc[i] := nsvc;
			connect(self:NSVC[i], nsvc.vc_nsvc:NSCP);
			NSVC[i].send(NS_Provider_Evt:{link_status := NS_PROV_LINK_STATUS_UP});
			return;
		}
	}
	Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("Overflow of g_nsvc array"));
}

private function f_nsvc_del(PerNsvcState nsvc) runs on NS_Provider_IPL4_CT
{
	for (var integer i := 0; i < sizeof(g_nsvc); i := i+1) {
		if (g_nsvc[i].vc_nsvc != null and
		    g_nsvc[i].remote_ip == nsvc.remote_ip and
		    g_nsvc[i].remote_port == nsvc.remote_port) {
			g_nsvc[i] := {
				remote_ip := -,
				remote_port := -,
				vc_nsvc := null
			}
			NSVC[i].send(NS_Provider_Evt:{link_status := NS_PROV_LINK_STATUS_DOWN});
			disconnect(self:NSVC[i], nsvc.vc_nsvc:NSCP);
			return;
		}
	}
	Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, log2str("attempt to delete unknown NSVC"));
}

private function f_get_nsvc_idx(charstring remote_ip, PortNumber remote_port)
runs on NS_Provider_IPL4_CT return integer
{
	for (var integer i := 0; i < sizeof(g_nsvc); i := i+1) {
		if (g_nsvc[i].vc_nsvc != null and
		    g_nsvc[i].remote_ip == remote_ip and g_nsvc[i].remote_port == remote_port) {
			return i;
		}
	}
	return -1;
}

function main(NSVCConfiguration config, NSConfiguration nsconfig, charstring id) runs on NS_Provider_IPL4_CT {
	for (var integer i := 0; i < sizeof(g_nsvc); i := i+1) {
		g_nsvc[i].vc_nsvc := null;
	}

	/* in order to support any number of NSVC on this endpoiint, we only bind the socket
	 * to its local ip/port, but do not connect it to the remote peer provided in 'config'. */
	map(self:IPL4, system:IPL4);
	var Result res := f_IPL4_listen(IPL4, config.provider.ip.local_ip,
					 config.provider.ip.local_udp_port, { udp := {}});
	if (not ispresent(res.connId)) {
		setverdict(fail, "Could not connect NS UDP socket ", config.provider.ip);
		mtc.stop;
	}
	g_conn_id := res.connId;

	if (NSE.checkstate("Connected")) {
		NSE.send(NS_Provider_Evt:{link_status := NS_PROV_LINK_STATUS_UP});
	}

	/* transceive between user-facing port and UDP socket */
	while (true) {
	var ASP_RecvFrom rx_rf;
	var PDU_NS rx_pdu;
	var integer rx_idx;
	var charstring remote_ip;
	var PortNumber remote_port;
	var NSVC_CT vc_nsvc;
	var NS_CT vc_caller;
	alt {

	[] IPL4.receive(ASP_RecvFrom:?) -> value rx_rf {
		/* we have to resolve the NS-VC based on the remote peer */
		var integer nsvc_idx := f_get_nsvc_idx(rx_rf.remName, rx_rf.remPort);
		if (nsvc_idx == -1) {
			/* backwards compatibility; if there's no NSVC, send to NSE port */
			NSE.send(dec_PDU_NS(rx_rf.msg));
		} else {
			/* endpoint mode; send to the per-NSVC component via NSVC port */
			NSVC[nsvc_idx].send(dec_PDU_NS(rx_rf.msg));
		}
		}

	[] IPL4.receive(ASP_ConnId_ReadyToRelease:?) {
		}

	[] IPL4.receive(ASP_Event:?) {
		}

	[] any from NSVC.receive(PDU_NS:?) -> value rx_pdu @index value rx_idx {
		/* we can use the port array index directly into the g_nsvc array in order
		 * to resolve the IP + port of the remote peer to which to send */
		var ASP_SendTo tx := {
			connId := g_conn_id,
			remName := g_nsvc[rx_idx].remote_ip,
			remPort := g_nsvc[rx_idx].remote_port,
			proto := { udp := {} },
			msg := enc_PDU_NS(rx_pdu)
		};
		IPL4.send(tx);
		}
	[] NSE.receive(PDU_NS:?) -> value rx_pdu {
		/* backwards compatibility: If user uses the NSE port, use the destination
		 * provided during main() initialization */
		var ASP_SendTo tx := {
			connId := g_conn_id,
			remName := config.provider.ip.remote_ip,
			remPort := config.provider.ip.remote_udp_port,
			proto := { udp := {} },
			msg := enc_PDU_NS(rx_pdu)
		};
		IPL4.send(tx);
		}

	/* procedure port to add/remove NSVCs from this provider */
	[] PROC.getcall(NSPIP_add_nsvc:{?,?,?}) -> param (remote_ip, remote_port, vc_nsvc) sender vc_caller {
		f_nsvc_add(PerNsvcState:{remote_ip, remote_port, vc_nsvc});
		PROC.reply(NSPIP_add_nsvc:{remote_ip, remote_port, vc_nsvc}) to vc_caller;
		}
	[] PROC.getcall(NSPIP_del_nsvc:{?,?}) -> param (remote_ip, remote_port) sender vc_caller {
		f_nsvc_del(PerNsvcState:{remote_ip, remote_port});
		PROC.reply(NSPIP_del_nsvc:{remote_ip, remote_port}) to vc_caller;
		}

	} /* alt */
	} /* while */

} /* main */

function f_nspip_add_nsvc(NS_Provider_IPL4_CT vc_ipep, charstring remote_ip, PortNumber remote_port, NSVC_CT vc_nsvc)
runs on NS_CT {
	NSPIP_PROC.call(NSPIP_add_nsvc:{remote_ip, remote_port, vc_nsvc}) to vc_ipep {
		[] NSPIP_PROC.getreply(NSPIP_add_nsvc:{?,?,?});
	}
}

} /* module */