--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mgw/ctrl_sock.c	Sat Jul 09 22:51:44 2022 -0800
@@ -0,0 +1,78 @@
+/*
+ * In this module we implement the logic of listening on the
+ * TMGW control socket and accepting control connections.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <syslog.h>
+#include <unistd.h>
+#include "struct.h"
+#include "select.h"
+
+static char ctrl_socket_pathname[] = "/var/gsm/tmgw_socket";
+
+extern void ctrl_message_handler();
+
+void
+ctrlsock_accept_handler(listener_fd)
+{
+	struct sockaddr_un sa;
+	socklen_t sa_len;
+	int conn_fd;
+	struct ctrl_conn *conn;
+
+	sa_len = sizeof sa;
+	conn_fd = accept(listener_fd, (struct sockaddr *) &sa, &sa_len);
+	if (conn_fd < 0) {
+		syslog(LOG_CRIT, "accept on UNIX socket: %m");
+		exit(1);
+	}
+	conn = malloc(sizeof(struct ctrl_conn));
+	if (!conn) {
+		syslog(LOG_CRIT, "malloc for ctrl socket conn: %m");
+		close(conn_fd);
+		return;
+	}
+	bzero(conn, sizeof(struct ctrl_conn));
+	update_max_fd(conn_fd);
+	FD_SET(conn_fd, &select_for_read);
+	select_handlers[conn_fd] = ctrl_message_handler;
+	select_data[conn_fd] = (void *) conn;
+	syslog(LOG_INFO, "accepted ctrl connection");
+}
+
+create_ctrl_socket()
+{
+	struct sockaddr_un sa;
+	unsigned sa_len;
+	int fd, rc;
+
+	fd = socket(AF_UNIX, SOCK_SEQPACKET, 0);
+	if (fd < 0) {
+		syslog(LOG_CRIT, "socket(AF_UNIX, SOCK_SEQPACKET, 0): %m");
+		return(-1);
+	}
+	unlink(ctrl_socket_pathname);
+	fill_sockaddr_un(ctrl_socket_pathname, &sa, &sa_len);
+	rc = bind(fd, (struct sockaddr *) &sa, sa_len);
+	if (rc < 0) {
+		syslog(LOG_ERR, "bind to %s: %m", ctrl_socket_pathname);
+		return(-1);
+	}
+	rc = listen(fd, 3);
+	if (rc < 0) {
+		syslog(LOG_CRIT, "listen on UNIX socket: %m");
+		return(-1);
+	}
+	update_max_fd(fd);
+	FD_SET(fd, &select_for_read);
+	select_handlers[fd] = ctrlsock_accept_handler;
+	return(0);
+}