add configtest flag

cmd/wireproxy/main.go

@@ -13,7 +13,7 @@ import (
 const daemonProcess = "daemon-process"
 
 func main() {
-	isDaemonProcess := os.Args[1] == daemonProcess
+	isDaemonProcess := len(os.Args) > 1 && os.Args[1] == daemonProcess
 	args := os.Args
 	if isDaemonProcess {
 		args = []string{args[0]}
@@ -24,6 +24,7 @@ func main() {
 
 	config := parser.String("c", "config", &argparse.Options{Required: true, Help: "Path of configuration file"})
 	daemon := parser.Flag("d", "daemon", &argparse.Options{Help: "Make wireproxy run in background"})
+	configTest := parser.Flag("n", "configtest", &argparse.Options{Help: "Configtest mode. Only check the configuration file for validity."})
 
 	err := parser.Parse(args)
 	if err != nil {
@@ -31,6 +32,16 @@ func main() {
 		return
 	}
 
+	conf, err := wireproxy.ParseConfig(*config)
+	if err != nil {
+		log.Panic(err)
+	}
+
+	if *configTest {
+		fmt.Println("Config OK")
+		return
+	}
+
 	if isDaemonProcess {
 		os.Stdout, _ = os.Open(os.DevNull)
 		os.Stderr, _ = os.Open(os.DevNull)
@@ -53,11 +64,6 @@ func main() {
 		return
 	}
 
-	conf, err := wireproxy.ParseConfig(*config)
-	if err != nil {
-		log.Panic(err)
-	}
-
 	tnet, err := wireproxy.StartWireguard(conf.Device)
 	if err != nil {
 		log.Panic(err)