Allows passing UAPI fd to service

3 files changed, 111 insertions, 67 deletions

diff --git a/src/main.go b/src/main.go
index 3808c9c..7d86716 100644
--- a/src/main.go
+++ b/src/main.go
@@ -9,7 +9,8 @@ import (
 )
 
 const (
-	EnvWGTunFD = "WG_TUN_FD"
+	ENV_WG_TUN_FD  = "WG_TUN_FD"
+	ENV_WG_UAPI_FD = "WG_UAPI_FD"
 )
 
 func printUsage() {
@@ -65,46 +66,69 @@ func main() {
 		logLevel,
 		fmt.Sprintf("(%s) ", interfaceName),
 	)
+
 	logger.Debug.Println("Debug log enabled")
 
-	// open TUN device
+	// open TUN device (or use supplied fd)
 
 	tun, err := func() (TUNDevice, error) {
-		tunFdStr := os.Getenv(EnvWGTunFD)
+		tunFdStr := os.Getenv(ENV_WG_TUN_FD)
 		if tunFdStr == "" {
 			return CreateTUN(interfaceName)
 		}
 
-		// construct tun device from supplied FD
+		// construct tun device from supplied fd
 
 		fd, err := strconv.ParseUint(tunFdStr, 10, 32)
 		if err != nil {
 			return nil, err
 		}
 
-		file := os.NewFile(uintptr(fd), "/dev/net/tun")
+		file := os.NewFile(uintptr(fd), "")
 		return CreateTUNFromFile(interfaceName, file)
 	}()
 
 	if err != nil {
 		logger.Error.Println("Failed to create TUN device:", err)
+		os.Exit(ExitSetupFailed)
 	}
 
+	// open UAPI file (or use supplied fd)
+
+	fileUAPI, err := func() (*os.File, error) {
+		uapiFdStr := os.Getenv(ENV_WG_UAPI_FD)
+		if uapiFdStr == "" {
+			return UAPIOpen(interfaceName)
+		}
+
+		// use supplied fd
+
+		fd, err := strconv.ParseUint(uapiFdStr, 10, 32)
+		if err != nil {
+			return nil, err
+		}
+
+		return os.NewFile(uintptr(fd), ""), nil
+	}()
+
+	if err != nil {
+		logger.Error.Println("UAPI listen error:", err)
+		os.Exit(ExitSetupFailed)
+		return
+	}
 	// daemonize the process
 
 	if !foreground {
 		env := os.Environ()
-		_, ok := os.LookupEnv(EnvWGTunFD)
-		if !ok {
-			kvp := fmt.Sprintf("%s=3", EnvWGTunFD)
-			env = append(env, kvp)
-		}
+		env = append(env, fmt.Sprintf("%s=3", ENV_WG_TUN_FD))
+		env = append(env, fmt.Sprintf("%s=4", ENV_WG_UAPI_FD))
 		attr := &os.ProcAttr{
 			Files: []*os.File{
 				nil, // stdin
 				nil, // stdout
 				nil, // stderr
 				tun.File(),
+				fileUAPI,
 			},
 			Dir: ".",
 			Env: env,
@@ -112,6 +136,7 @@ func main() {
 		err = Daemonize(attr)
 		if err != nil {
 			logger.Error.Println("Failed to daemonize:", err)
+			os.Exit(ExitSetupFailed)
 		}
 		return
 	}
@@ -123,20 +148,17 @@ func main() {
 	// create wireguard device
 
 	device := NewDevice(tun, logger)
+
 	logger.Info.Println("Device started")
 
-	// start configuration lister
-
-	uapi, err := NewUAPIListener(interfaceName)
-	if err != nil {
-		logger.Error.Println("UAPI listen error:", err)
-		return
-	}
+	// start uapi listener
 
 	errs := make(chan error)
 	term := make(chan os.Signal)
 	wait := device.WaitChannel()
 
+	uapi, err := UAPIListen(interfaceName, fileUAPI)
+
 	go func() {
 		for {
 			conn, err := uapi.Accept()
@@ -161,9 +183,10 @@ func main() {
 	case <-errs:
 	}
 
-	// clean up UAPI bind
+	// clean up
 
 	uapi.Close()
+	device.Close()
 
 	logger.Info.Println("Shutting down")
 }
diff --git a/src/tun_linux.go b/src/tun_linux.go
index ce6304c..2a5b276 100644
--- a/src/tun_linux.go
+++ b/src/tun_linux.go
@@ -227,7 +227,7 @@ func (tun *NativeTun) MTU() (int, error) {
 
 	val := binary.LittleEndian.Uint32(ifr[16:20])
 	if val >= (1 << 31) {
-		return int(val-(1<<31)) - (1 << 31), nil
+		return int(toInt32(val)), nil
 	}
 	return int(val), nil
 }
diff --git a/src/uapi_linux.go b/src/uapi_linux.go
index cb9d858..f97a18a 100644
--- a/src/uapi_linux.go
+++ b/src/uapi_linux.go
@@ -10,12 +10,12 @@ import (
 )
 
 const (
-	ipcErrorIO         = -int64(unix.EIO)
-	ipcErrorProtocol   = -int64(unix.EPROTO)
-	ipcErrorInvalid    = -int64(unix.EINVAL)
-	ipcErrorPortInUse  = -int64(unix.EADDRINUSE)
-	socketDirectory    = "/var/run/wireguard"
-	socketName         = "%s.sock"
+	ipcErrorIO        = -int64(unix.EIO)
+	ipcErrorProtocol  = -int64(unix.EPROTO)
+	ipcErrorInvalid   = -int64(unix.EINVAL)
+	ipcErrorPortInUse = -int64(unix.EADDRINUSE)
+	socketDirectory   = "/var/run/wireguard"
+	socketName        = "%s.sock"
 )
 
 type UAPIListener struct {
@@ -50,49 +50,11 @@ func (l *UAPIListener) Addr() net.Addr {
 	return nil
 }
 
-func connectUnixSocket(path string) (net.Listener, error) {
+func UAPIListen(name string, file *os.File) (net.Listener, error) {
 
-	// attempt inital connection
+	// wrap file in listener
 
-	listener, err := net.Listen("unix", path)
-	if err == nil {
-		return listener, nil
-	}
-
-	// check if active
-
-	_, err = net.Dial("unix", path)
-	if err == nil {
-		return nil, errors.New("Unix socket in use")
-	}
-
-	// attempt cleanup
-
-	err = os.Remove(path)
-	if err != nil {
-		return nil, err
-	}
-
-	return net.Listen("unix", path)
-}
-
-func NewUAPIListener(name string) (net.Listener, error) {
-
-	// check if path exist
-
-	err := os.MkdirAll(socketDirectory, 077)
-	if err != nil && !os.IsExist(err) {
-		return nil, err
-	}
-
-	// open UNIX socket
-
-	socketPath := path.Join(
-		socketDirectory,
-		fmt.Sprintf(socketName, name),
-	)
-
-	listener, err := connectUnixSocket(socketPath)
+	listener, err := net.FileListener(file)
 	if err != nil {
 		return nil, err
 	}
@@ -105,6 +67,11 @@ func NewUAPIListener(name string) (net.Listener, error) {
 
 	// watch for deletion of socket
 
+	socketPath := path.Join(
+		socketDirectory,
+		fmt.Sprintf(socketName, name),
+	)
+
 	uapi.inotifyFd, err = unix.InotifyInit()
 	if err != nil {
 		return nil, err
@@ -125,11 +92,12 @@ func NewUAPIListener(name string) (net.Listener, error) {
 	go func(l *UAPIListener) {
 		var buff [4096]byte
 		for {
-			unix.Read(uapi.inotifyFd, buff[:])
+			// start with lstat to avoid race condition
 			if _, err := os.Lstat(socketPath); os.IsNotExist(err) {
 				l.connErr <- err
 				return
 			}
+			unix.Read(uapi.inotifyFd, buff[:])
 		}
 	}(uapi)
 
@@ -148,3 +116,56 @@ func NewUAPIListener(name string) (net.Listener, error) {
 
 	return uapi, nil
 }
+
+func UAPIOpen(name string) (*os.File, error) {
+
+	// check if path exist
+
+	err := os.MkdirAll(socketDirectory, 0600)
+	if err != nil && !os.IsExist(err) {
+		return nil, err
+	}
+
+	// open UNIX socket
+
+	socketPath := path.Join(
+		socketDirectory,
+		fmt.Sprintf(socketName, name),
+	)
+
+	addr, err := net.ResolveUnixAddr("unix", socketPath)
+	if err != nil {
+		return nil, err
+	}
+
+	listener, err := func() (*net.UnixListener, error) {
+
+		// initial connection attempt
+
+		listener, err := net.ListenUnix("unix", addr)
+		if err == nil {
+			return listener, nil
+		}
+
+		// check if socket already active
+
+		_, err = net.Dial("unix", socketPath)
+		if err == nil {
+			return nil, errors.New("unix socket in use")
+		}
+
+		// cleanup & attempt again
+
+		err = os.Remove(socketPath)
+		if err != nil {
+			return nil, err
+		}
+		return net.ListenUnix("unix", addr)
+	}()
+
+	if err != nil {
+		return nil, err
+	}
+
+	return listener.File()
+}