listenUnix.go

func listenUnix(socket_path string) (*net.UnixListener, error) {
	addr, err := net.ResolveUnixAddr("unix", socket_path)
	if err != nil {
		return nil, err
	}

	fi, err := os.Lstat(socket_path)
	switch {
	case os.IsNotExist(err):
		return net.ListenUnix("unix", addr)
	case err != nil:
		return nil, &os.PathError{Op: "lstat", Path: socket_path, Err: err}
	case fi.Mode()&os.ModeSocket == 0: // is not a socket
		return nil, &os.PathError{Op: "lstat", Path: socket_path, Err: os.ErrInvalid}
	default:
		// Check that noone listens on the socket.
		conn, err := net.DialUnix("unix", nil, addr)
		if err == nil {
			conn.Close()
			return nil, &net.OpError{Net: "unix", Op: "listen", Source: nil, Addr: addr, Err: os.ErrExist}
		}
		nerr := err.(*net.OpError)
		if nerr.Op != "dial" || nerr.Net != "unix" || nerr.Err == nil {
			return nil, err
		}
		if _, ok := nerr.Err.(*os.SyscallError); ok {
			// remove socket
			err := os.Remove(socket_path)
			if err != nil {
				return nil, &os.PathError{Op: "remove", Path: socket_path, Err: err}
			}
		}
	}

	return net.ListenUnix("unix", addr)
}