Add private mount propagation to API.

And make it default

pkg/apis/core/types.go

@@ -1540,6 +1540,12 @@ type VolumeMount struct {
 type MountPropagationMode string
 
 const (
+	// MountPropagationNone means that the volume in a container will
+	// not receive new mounts from the host or other containers, and filesystems
+	// mounted inside the container won't be propagated to the host or other
+	// containers.
+	// Note that this mode corresponds to "private" in Linux terminology.
+	MountPropagationNone MountPropagationMode = "None"
 	// MountPropagationHostToContainer means that the volume in a container will
 	// receive new mounts from the host or other containers, but filesystems
 	// mounted inside the container won't be propagated to the host or other

pkg/apis/core/validation/validation.go

@@ -1140,7 +1140,7 @@ func validateMountPropagation(mountPropagation *core.MountPropagationMode, conta
 		return allErrs
 	}
 
-	supportedMountPropagations := sets.NewString(string(core.MountPropagationBidirectional), string(core.MountPropagationHostToContainer))
+	supportedMountPropagations := sets.NewString(string(core.MountPropagationBidirectional), string(core.MountPropagationHostToContainer), string(core.MountPropagationNone))
 	if !supportedMountPropagations.Has(string(*mountPropagation)) {
 		allErrs = append(allErrs, field.NotSupported(fldPath, *mountPropagation, supportedMountPropagations.List()))
 	}

pkg/apis/core/validation/validation_test.go

@@ -4704,6 +4704,7 @@ func TestValidateMountPropagation(t *testing.T) {
 
 	propagationBidirectional := core.MountPropagationBidirectional
 	propagationHostToContainer := core.MountPropagationHostToContainer
+	propagationNone := core.MountPropagationNone
 	propagationInvalid := core.MountPropagationMode("invalid")
 
 	tests := []struct {
@@ -4723,6 +4724,12 @@ func TestValidateMountPropagation(t *testing.T) {
 			defaultContainer,
 			false,
 		},
+		{
+			// non-privileged container + None
+			core.VolumeMount{Name: "foo", MountPath: "/foo", MountPropagation: &propagationNone},
+			defaultContainer,
+			false,
+		},
 		{
 			// error: implicitly non-privileged container + Bidirectional
 			core.VolumeMount{Name: "foo", MountPath: "/foo", MountPropagation: &propagationBidirectional},

pkg/kubelet/kubelet_pods.go

@@ -269,12 +269,14 @@ func translateMountPropagation(mountMode *v1.MountPropagationMode) (runtimeapi.M
 	}
 	switch {
 	case mountMode == nil:
-		// HostToContainer is the default
+		// PRIVATE is the default
-		return runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER, nil
+		return runtimeapi.MountPropagation_PROPAGATION_PRIVATE, nil
 	case *mountMode == v1.MountPropagationHostToContainer:
 		return runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER, nil
 	case *mountMode == v1.MountPropagationBidirectional:
 		return runtimeapi.MountPropagation_PROPAGATION_BIDIRECTIONAL, nil
+	case *mountMode == v1.MountPropagationNone:
+		return runtimeapi.MountPropagation_PROPAGATION_PRIVATE, nil
 	default:
 		return 0, fmt.Errorf("invalid MountPropagation mode: %q", mountMode)
 	}

pkg/kubelet/kubelet_pods_test.go

@@ -55,6 +55,7 @@ func TestMakeMounts(t *testing.T) {
 	bTrue := true
 	propagationHostToContainer := v1.MountPropagationHostToContainer
 	propagationBidirectional := v1.MountPropagationBidirectional
+	propagationNone := v1.MountPropagationNone
 
 	testCases := map[string]struct {
 		container      v1.Container
@@ -79,9 +80,10 @@ func TestMakeMounts(t *testing.T) {
 						MountPropagation: &propagationHostToContainer,
 					},
 					{
-						MountPath: "/mnt/path3",
+						MountPath:        "/mnt/path3",
-						Name:      "disk",
+						Name:             "disk",
-						ReadOnly:  true,
+						ReadOnly:         true,
+						MountPropagation: &propagationNone,
 					},
 					{
 						MountPath: "/mnt/path4",
@@ -110,7 +112,7 @@ func TestMakeMounts(t *testing.T) {
 					HostPath:       "/mnt/disk",
 					ReadOnly:       true,
 					SELinuxRelabel: false,
-					Propagation:    runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER,
+					Propagation:    runtimeapi.MountPropagation_PROPAGATION_PRIVATE,
 				},
 				{
 					Name:           "disk4",
@@ -118,7 +120,7 @@ func TestMakeMounts(t *testing.T) {
 					HostPath:       "/mnt/host",
 					ReadOnly:       false,
 					SELinuxRelabel: false,
-					Propagation:    runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER,
+					Propagation:    runtimeapi.MountPropagation_PROPAGATION_PRIVATE,
 				},
 				{
 					Name:           "disk5",
@@ -126,7 +128,7 @@ func TestMakeMounts(t *testing.T) {
 					HostPath:       "/var/lib/kubelet/podID/volumes/empty/disk5",
 					ReadOnly:       false,
 					SELinuxRelabel: false,
-					Propagation:    runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER,
+					Propagation:    runtimeapi.MountPropagation_PROPAGATION_PRIVATE,
 				},
 			},
 			expectErr: false,
@@ -185,7 +187,7 @@ func TestMakeMounts(t *testing.T) {
 					HostPath:       "/mnt/host",
 					ReadOnly:       false,
 					SELinuxRelabel: false,
-					Propagation:    runtimeapi.MountPropagation_PROPAGATION_HOST_TO_CONTAINER,
+					Propagation:    runtimeapi.MountPropagation_PROPAGATION_PRIVATE,
 				},
 			},
 			expectErr: false,

staging/src/k8s.io/api/core/v1/types.go

@@ -1624,6 +1624,12 @@ type VolumeMount struct {
 type MountPropagationMode string
 
 const (
+	// MountPropagationNone means that the volume in a container will
+	// not receive new mounts from the host or other containers, and filesystems
+	// mounted inside the container won't be propagated to the host or other
+	// containers.
+	// Note that this mode corresponds to "private" in Linux terminology.
+	MountPropagationNone MountPropagationMode = "None"
 	// MountPropagationHostToContainer means that the volume in a container will
 	// receive new mounts from the host or other containers, but filesystems
 	// mounted inside the container won't be propagated to the host or other