Workaround a crash in x11vnc

Fix? #569

gns3server/modules/docker/docker_vm.py

@@ -415,7 +415,8 @@ class DockerVM(BaseVM):
         if shutil.which("Xvfb") is None or shutil.which("x11vnc") is None:
             raise DockerError("Please install Xvfb and x11vnc before using the VNC support")
         self._xvfb_process = yield from asyncio.create_subprocess_exec("Xvfb", "-nolisten", "tcp", ":{}".format(self._display), "-screen", "0", self._console_resolution + "x16")
-        self._x11vnc_process = yield from asyncio.create_subprocess_exec("x11vnc", "-forever", "-nopw", "-shared", "-geometry", self._console_resolution, "-display", "WAIT:{}".format(self._display), "-rfbport", str(self.console), "-noncache", "-listen", self._manager.port_manager.console_host)
+        # We pass a port for TCPV6 due to a crash in X11VNC if not here: https://github.com/GNS3/gns3-server/issues/569
+        self._x11vnc_process = yield from asyncio.create_subprocess_exec("x11vnc", "-forever", "-nopw", "-shared", "-geometry", self._console_resolution, "-display", "WAIT:{}".format(self._display), "-rfbport", str(self.console), "-rfbportv6", str(self.console), "-noncache", "-listen", self._manager.port_manager.console_host)
 
         x11_socket = os.path.join("/tmp/.X11-unix/", "X{}".format(self._display))
         yield from wait_for_file_creation(x11_socket)

tests/modules/docker/test_docker_vm.py

@@ -891,7 +891,7 @@ def test_start_vnc(vm, loop):
                 loop.run_until_complete(asyncio.async(vm._start_vnc()))
     assert vm._display is not None
     mock_exec.assert_any_call("Xvfb", "-nolisten", "tcp", ":{}".format(vm._display), "-screen", "0", "1280x1024x16")
-    mock_exec.assert_any_call("x11vnc", "-forever", "-nopw", "-shared", "-geometry", "1280x1024", "-display", "WAIT:{}".format(vm._display), "-rfbport", str(vm.console), "-noncache", "-listen", "127.0.0.1")
+    mock_exec.assert_any_call("x11vnc", "-forever", "-nopw", "-shared", "-geometry", "1280x1024", "-display", "WAIT:{}".format(vm._display), "-rfbport", str(vm.console), "-rfbportv6", str(vm.console), "-noncache", "-listen", "127.0.0.1")
     mock_wait.assert_called_with("/tmp/.X11-unix/X{}".format(vm._display))