--- a/mtctest/Makefile	Sat Jul 09 23:29:54 2022 -0800
+++ b/mtctest/Makefile	Sun Jul 10 00:24:19 2022 -0800
@@ -1,7 +1,7 @@
 CC=	gcc
 CFLAGS=	-O2
 PROG=	themwi-test-mtc
-OBJS=	disconnect.o main.o setup.o sig_handler.o sock_conn.o
+OBJS=	disconnect.o dummy_rtp.o main.o setup.o sig_handler.o sock_conn.o
 LIBS=	../libnumdb/libnumdb.a ../libutil/libutil.a
 INSTBIN=/usr/local/bin
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mtctest/dummy_rtp.c	Sun Jul 10 00:24:19 2022 -0800
@@ -0,0 +1,65 @@
+/*
+ * In this module we implement the code that connects to themwi-mgw
+ * and obtains a dummy GSM-side RTP endpoint.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include "../include/tmgw_ctrl.h"
+#include "../include/tmgw_const.h"
+
+struct sockaddr_storage dummy_rtp_endp;
+
+static char tmgw_socket_pathname[] = "/var/gsm/tmgw_socket";
+
+obtain_dummy_rtp()
+{
+	struct sockaddr_un sa;
+	unsigned sa_len;
+	int fd, rc;
+	struct tmgw_ctrl_req req;
+	struct tmgw_ctrl_resp resp;
+
+	fd = socket(AF_UNIX, SOCK_SEQPACKET, 0);
+	if (fd < 0) {
+		perror("socket(AF_UNIX, SOCK_SEQPACKET, 0)");
+		exit(1);
+	}
+	fill_sockaddr_un(tmgw_socket_pathname, &sa, &sa_len);
+	rc = connect(fd, (struct sockaddr *) &sa, sa_len);
+	if (rc < 0) {
+		perror(tmgw_socket_pathname);
+		exit(1);
+	}
+	bzero(&req, sizeof req);
+	req.opcode = TMGW_CTRL_OP_CRCX;
+	req.ep_id = TMGW_EP_TYPE_DUMMY_GSM;
+	rc = send(fd, &req, sizeof req, 0);
+	if (rc < 0) {
+		perror("send to TMGW socket");
+		exit(1);
+	}
+	rc = recv(fd, &resp, sizeof resp, 0);
+	if (rc < 0) {
+		perror("recv from TMGW socket");
+		exit(1);
+	}
+	if (rc != sizeof resp) {
+		fprintf(stderr,
+	"error: response packet from TMGW has wrong length (%d bytes)\n",
+			rc);
+		exit(1);
+	}
+	if (resp.res != TMGW_RESP_OK) {
+		fprintf(stderr, "TMGW CRCX returned error %u\n", resp.res);
+		exit(1);
+	}
+	bcopy(&resp.gsm_addr, &dummy_rtp_endp, sizeof(struct sockaddr_storage));
+	return(0);
+}

--- a/mtctest/main.c	Sat Jul 09 23:29:54 2022 -0800
+++ b/mtctest/main.c	Sun Jul 10 00:24:19 2022 -0800
@@ -40,6 +40,7 @@
 		goto usage;
 	openlog("themwi-test-mtc", 0, LOG_LOCAL5);
 	init_setup_msg(from, argv[optind]);
+	obtain_dummy_rtp();
 	connect_mtc_socket();
 	send_setup_msg();
 	/* main select loop */

--- a/mtctest/sig_handler.c	Sat Jul 09 23:29:54 2022 -0800
+++ b/mtctest/sig_handler.c	Sun Jul 10 00:24:19 2022 -0800
@@ -15,6 +15,7 @@
 #include "../include/gsm48_const.h"
 
 extern int disconnect_mode;
+extern struct sockaddr_storage dummy_rtp_endp;
 
 static void
 print_bearer_cap(bcap)
@@ -286,6 +287,10 @@
 	printf("MNCC_RTP_CREATE: RTP info from MSC\n");
 	printf("payload_type=0x%x payload_msg_type=0x%x\n", msg->payload_type,
 		msg->payload_msg_type);
+	printf("Responding with MNCC_RTP_CONNECT (dummy RTP endpoint)\n");
+	msg->msg_type = MNCC_RTP_CONNECT;
+	bcopy(&dummy_rtp_endp, &msg->addr, sizeof(struct sockaddr_storage));
+	send_mncc_to_gsm(msg, sizeof(struct gsm_mncc_rtp));
 }
 
 void