manager: don't activate device if the parent is missing

In multiple places we currently proceed to creating a virtual device
even if the connection specifies a parent device which is
missing. This can be easily reproduced with:

  nmcli con add type vxlan ifname vxlan1 \
                vxlan.parent not-exists \
                id 43 remote 172.25.1.1

which creates a vxlan1 interface without activating any
connection. Add a check to prevent this.

https://bugzilla.redhat.com/show_bug.cgi?id=1774074
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/merge_requests/344

src/devices/nm-device.c

@@ -5934,6 +5934,7 @@ check_connection_compatible (NMDevice *self, NMConnection *connection, GError **
 	conn_iface = nm_manager_get_connection_iface (NM_MANAGER_GET,
 	                                              connection,
 	                                              NULL,
+	                                              NULL,
 	                                              &local);
 
 	/* We always need a interface name for virtual devices, but for

src/nm-manager.c

@@ -1715,7 +1715,10 @@ nm_manager_get_state (NMManager *manager)
 /*****************************************************************************/
 
 static NMDevice *
-find_parent_device_for_connection (NMManager *self, NMConnection *connection, NMDeviceFactory *cached_factory)
+find_parent_device_for_connection (NMManager *self,
+                                   NMConnection *connection,
+                                   NMDeviceFactory *cached_factory,
+                                   const char **out_parent_spec)
 {
 	NMManagerPrivate *priv = NM_MANAGER_GET_PRIVATE (self);
 	NMDeviceFactory *factory;
@@ -1725,6 +1728,7 @@ find_parent_device_for_connection (NMManager *self, NMConnection *connection, NM
 	NMDevice *candidate;
 
 	g_return_val_if_fail (NM_IS_CONNECTION (connection), NULL);
+	NM_SET_OUT (out_parent_spec, NULL);
 
 	if (!cached_factory) {
 		factory = nm_device_factory_manager_find_factory_for_connection (connection);
@@ -1737,6 +1741,8 @@ find_parent_device_for_connection (NMManager *self, NMConnection *connection, NM
 	if (!parent_name)
 		return NULL;
 
+	NM_SET_OUT (out_parent_spec, parent_name);
+
 	/* Try as an interface name of a parent device */
 	parent = find_device_by_iface (self, parent_name, NULL, NULL);
 	if (parent)
@@ -1778,6 +1784,9 @@ find_parent_device_for_connection (NMManager *self, NMConnection *connection, NM
  * @self: the #NMManager
  * @connection: the #NMConnection to get the interface for
  * @out_parent: on success, the parent device if any
+ * @out_parent_spec: on return, a string specifying the parent device
+ *   in the connection. This can be a device name, a MAC address or a
+ *   connection UUID.
  * @error: an error if determining the virtual interface name failed
  *
  * Given @connection, returns the interface name that the connection
@@ -1791,14 +1800,15 @@ char *
 nm_manager_get_connection_iface (NMManager *self,
                                  NMConnection *connection,
                                  NMDevice **out_parent,
+                                 const char **out_parent_spec,
                                  GError **error)
 {
 	NMDeviceFactory *factory;
 	char *iface = NULL;
 	NMDevice *parent = NULL;
 
-	if (out_parent)
+	NM_SET_OUT (out_parent, NULL);
-		*out_parent = NULL;
+	NM_SET_OUT (out_parent_spec, NULL);
 
 	factory = nm_device_factory_manager_find_factory_for_connection (connection);
 	if (!factory) {
@@ -1821,7 +1831,7 @@ nm_manager_get_connection_iface (NMManager *self,
 		goto return_ifname_fom_connection;
 	}
 
-	parent = find_parent_device_for_connection (self, connection, factory);
+	parent = find_parent_device_for_connection (self, connection, factory, out_parent_spec);
 	iface = nm_device_factory_get_connection_iface (factory,
 	                                                connection,
 	                                                parent ? nm_device_get_ip_iface (parent) : NULL,
@@ -1918,6 +1928,7 @@ system_create_virtual_device (NMManager *self, NMConnection *connection)
 	gs_free NMSettingsConnection **connections = NULL;
 	guint i;
 	gs_free char *iface = NULL;
+	const char *parent_spec;
 	NMDevice *device = NULL, *parent = NULL;
 	NMDevice *dev_candidate;
 	GError *error = NULL;
@@ -1926,7 +1937,7 @@ system_create_virtual_device (NMManager *self, NMConnection *connection)
 	g_return_val_if_fail (NM_IS_MANAGER (self), NULL);
 	g_return_val_if_fail (NM_IS_CONNECTION (connection), NULL);
 
-	iface = nm_manager_get_connection_iface (self, connection, &parent, &error);
+	iface = nm_manager_get_connection_iface (self, connection, &parent, &parent_spec, &error);
 	if (!iface) {
 		_LOG3D (LOGD_DEVICE, connection, "can't get a name of a virtual device: %s",
 		        error->message);
@@ -1934,6 +1945,11 @@ system_create_virtual_device (NMManager *self, NMConnection *connection)
 		return NULL;
 	}
 
+	if (parent_spec && !parent) {
+		/* parent is not ready, wait */
+		return NULL;
+	}
+
 	/* See if there's a device that is already compatible with this connection */
 	c_list_for_each_entry (dev_candidate, &priv->devices_lst_head, devices_lst) {
 		if (nm_device_check_connection_compatible (dev_candidate, connection, NULL)) {
@@ -2047,10 +2063,10 @@ retry_connections_for_parent_device (NMManager *self, NMDevice *device)
 		gs_free char *ifname = NULL;
 		NMDevice *parent;
 
-		parent = find_parent_device_for_connection (self, connection, NULL);
+		parent = find_parent_device_for_connection (self, connection, NULL, NULL);
 		if (parent == device) {
 			/* Only try to activate devices that don't already exist */
-			ifname = nm_manager_get_connection_iface (self, connection, &parent, &error);
+			ifname = nm_manager_get_connection_iface (self, connection, &parent, NULL, &error);
 			if (ifname) {
 				if (!nm_platform_link_get_by_ifname (NM_PLATFORM_GET, ifname))
 					connection_changed (self, sett_conn);
@@ -4552,6 +4568,7 @@ _internal_activate_device (NMManager *self, NMActiveConnection *active, GError *
 	NMAuthSubject *subject;
 	GError *local = NULL;
 	NMConnectionMultiConnect multi_connect;
+	const char *parent_spec;
 
 	g_return_val_if_fail (NM_IS_MANAGER (self), FALSE);
 	g_return_val_if_fail (NM_IS_ACTIVE_CONNECTION (active), FALSE);
@@ -4604,7 +4621,14 @@ _internal_activate_device (NMManager *self, NMActiveConnection *active, GError *
 
 		parent = find_parent_device_for_connection (self,
 		                                            nm_settings_connection_get_connection (sett_conn),
-		                                            NULL);
+		                                            NULL,
+		                                            &parent_spec);
+
+		if (parent_spec && !parent) {
+			g_set_error (error, NM_MANAGER_ERROR, NM_MANAGER_ERROR_DEPENDENCY_FAILED,
+			             "parent device '%s' not found", parent_spec);
+			return FALSE;
+		}
 
 		if (parent && !nm_device_is_real (parent)) {
 			NMSettingsConnection *parent_con;
@@ -5159,7 +5183,7 @@ validate_activation_request (NMManager *self,
 			}
 
 			/* Look for an existing device with the connection's interface name */
-			iface = nm_manager_get_connection_iface (self, connection, NULL, error);
+			iface = nm_manager_get_connection_iface (self, connection, NULL, NULL, error);
 			if (!iface)
 				return NULL;
 

src/nm-manager.h

@@ -149,6 +149,7 @@ void                nm_manager_device_route_metric_clear (NMManager *self,
 char *              nm_manager_get_connection_iface (NMManager *self,
                                                      NMConnection *connection,
                                                      NMDevice **out_parent,
+                                                     const char **out_parent_spec,
                                                      GError **error);
 
 const char *        nm_manager_iface_for_uuid          (NMManager *self,