@@ -284,29 +284,41 @@ func newRouterOptions(config *config.Config, daemon *daemon.Daemon) (routerOptio

 }

 func (cli *DaemonCli) reloadConfig() {

-	reload := func(config *config.Config) {

+	reload := func(c *config.Config) {

 		// Revalidate and reload the authorization plugins

-		if err := validateAuthzPlugins(config.AuthorizationPlugins, cli.d.PluginStore); err != nil {

+		if err := validateAuthzPlugins(c.AuthorizationPlugins, cli.d.PluginStore); err != nil {

 			logrus.Fatalf("Error validating authorization plugin: %v", err)

 			return

 		}

-		cli.authzMiddleware.SetPlugins(config.AuthorizationPlugins)

+		cli.authzMiddleware.SetPlugins(c.AuthorizationPlugins)

+

+		// The namespaces com.docker.*, io.docker.*, org.dockerproject.* have been documented

+		// to be reserved for Docker's internal use, but this was never enforced.  Allowing

+		// configured labels to use these namespaces are deprecated for 18.05.

+		//

+		// The following will check the usage of such labels, and report a warning for deprecation.

+		//

+		// TODO: At the next stable release, the validation should be folded into the other

+		// configuration validation functions and an error will be returned instead, and this

+		// block should be deleted.

+		if err := config.ValidateReservedNamespaceLabels(c.Labels); err != nil {

+			logrus.Warnf("Configured labels using reserved namespaces is deprecated: %s", err)

+		}

-		if err := cli.d.Reload(config); err != nil {

+		if err := cli.d.Reload(c); err != nil {

 			logrus.Errorf("Error reconfiguring the daemon: %v", err)

 			return

 		}

-		if config.IsValueSet("debug") {

+		if c.IsValueSet("debug") {

 			debugEnabled := debug.IsEnabled()

 			switch {

-			case debugEnabled && !config.Debug: // disable debug

+			case debugEnabled && !c.Debug: // disable debug

 				debug.Disable()

-			case config.Debug && !debugEnabled: // enable debug

+			case c.Debug && !debugEnabled: // enable debug

 				debug.Enable()

 			}

-

 		}

 	}

@@ -406,6 +418,18 @@ func loadDaemonCliConfig(opts *daemonOptions) (*config.Config, error) {

 	if err != nil {

 		return nil, err

 	}

+	// The namespaces com.docker.*, io.docker.*, org.dockerproject.* have been documented

+	// to be reserved for Docker's internal use, but this was never enforced.  Allowing

+	// configured labels to use these namespaces are deprecated for 18.05.

+	//

+	// The following will check the usage of such labels, and report a warning for deprecation.

+	//

+	// TODO: At the next stable release, the validation should be folded into the other

+	// configuration validation functions and an error will be returned instead, and this

+	// block should be deleted.

+	if err := config.ValidateReservedNamespaceLabels(newLabels); err != nil {

+		logrus.Warnf("Configured labels using reserved namespaces is deprecated: %s", err)

+	}

 	conf.Labels = newLabels

 	// Regardless of whether the user sets it to true or false, if they

@@ -262,6 +262,25 @@ func GetConflictFreeLabels(labels []string) ([]string, error) {

 	return newLabels, nil

 }

+// ValidateReservedNamespaceLabels errors if the reserved namespaces com.docker.*,

+// io.docker.*, org.dockerproject.* are used in a configured engine label.

+//

+// TODO: This is a separate function because we need to warn users first of the

+// deprecation.  When we return an error, this logic can be added to Validate

+// or GetConflictFreeLabels instead of being here.

+func ValidateReservedNamespaceLabels(labels []string) error {

+	for _, label := range labels {

+		lowered := strings.ToLower(label)

+		if strings.HasPrefix(lowered, "com.docker.") || strings.HasPrefix(lowered, "io.docker.") ||

+			strings.HasPrefix(lowered, "org.dockerproject.") {

+			return fmt.Errorf(

+				"label %s not allowed: the namespaces com.docker.*, io.docker.*, and org.dockerproject.* are reserved for Docker's internal use",

+				label)

+		}

+	}

+	return nil

+}

+

 // Reload reads the configuration in the host and reloads the daemon and server.

 func Reload(configFile string, flags *pflag.FlagSet, reload func(*Config)) error {

 	logrus.Infof("Got signal to reload configuration, reloading from: %s", configFile)

@@ -193,6 +193,40 @@ func TestFindConfigurationConflictsWithMergedValues(t *testing.T) {

 	}

 }

+func TestValidateReservedNamespaceLabels(t *testing.T) {

+	for _, validLabels := range [][]string{

+		nil, // no error if there are no labels

+		{ // no error if there aren't any reserved namespace labels

+			"hello=world",

+			"label=me",

+		},

+		{ // only reserved namespaces that end with a dot are invalid

+			"com.dockerpsychnotreserved.label=value",

+			"io.dockerproject.not=reserved",

+			"org.docker.not=reserved",

+		},

+	} {

+		assert.Check(t, ValidateReservedNamespaceLabels(validLabels))

+	}

+

+	for _, invalidLabel := range []string{

+		"com.docker.feature=enabled",

+		"io.docker.configuration=0",

+		"org.dockerproject.setting=on",

+		// casing doesn't matter

+		"COM.docker.feature=enabled",

+		"io.DOCKER.CONFIGURATION=0",

+		"Org.Dockerproject.Setting=on",

+	} {

+		err := ValidateReservedNamespaceLabels([]string{

+			"valid=label",

+			invalidLabel,

+			"another=valid",

+		})

+		assert.Check(t, is.ErrorContains(err, invalidLabel))

+	}

+}

+

 func TestValidateConfigurationErrors(t *testing.T) {

 	minusNumber := -10

 	testCases := []struct {