Use constants instead of magic string for runtime names

pkg/kubelet/apis/kubeletconfig/v1alpha1/defaults.go

@@ -82,7 +82,7 @@ func SetDefaults_KubeletConfiguration(obj *KubeletConfiguration) {
 		obj.VolumeStatsAggPeriod = metav1.Duration{Duration: time.Minute}
 	}
 	if obj.ContainerRuntime == "" {
-		obj.ContainerRuntime = "docker"
+		obj.ContainerRuntime = kubetypes.DockerContainerRuntime
 	}
 	if obj.RuntimeRequestTimeout == zeroDuration {
 		obj.RuntimeRequestTimeout = metav1.Duration{Duration: 2 * time.Minute}

pkg/kubelet/kubelet_network.go

@@ -27,6 +27,7 @@ import (
 	"k8s.io/api/core/v1"
 	"k8s.io/kubernetes/pkg/kubelet/apis/kubeletconfig"
 	"k8s.io/kubernetes/pkg/kubelet/network"
+	kubetypes "k8s.io/kubernetes/pkg/kubelet/types"
 	utiliptables "k8s.io/kubernetes/pkg/util/iptables"
 )
 
@@ -57,7 +58,7 @@ func effectiveHairpinMode(hairpinMode kubeletconfig.HairpinMode, containerRuntim
 	// - It's set to "none".
 	if hairpinMode == kubeletconfig.PromiscuousBridge || hairpinMode == kubeletconfig.HairpinVeth {
 		// Only on docker.
-		if containerRuntime != "docker" {
+		if containerRuntime != kubetypes.DockerContainerRuntime {
 			glog.Warningf("Hairpin mode set to %q but container runtime is %q, ignoring", hairpinMode, containerRuntime)
 			return kubeletconfig.HairpinNone, nil
 		}

pkg/security/apparmor/validate.go

@@ -28,6 +28,7 @@ import (
 	"k8s.io/api/core/v1"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/kubernetes/pkg/features"
+	kubetypes "k8s.io/kubernetes/pkg/kubelet/types"
 	utilfile "k8s.io/kubernetes/pkg/util/file"
 )
 
@@ -111,7 +112,7 @@ func validateHost(runtime string) error {
 	}
 
 	// Check runtime support. Currently only Docker is supported.
-	if runtime != "docker" && runtime != "remote" {
+	if runtime != kubetypes.DockerContainerRuntime && runtime != kubetypes.RemoteContainerRuntime {
 		return fmt.Errorf("AppArmor is only enabled for 'docker' and 'remote' runtimes. Found: %q.", runtime)
 	}