support hostIP in downward API

pkg/api/v1/conversion.go

@@ -190,6 +190,7 @@ func addConversionFuncs(scheme *runtime.Scheme) error {
 				"spec.restartPolicy",
 				"spec.serviceAccountName",
 				"status.phase",
+				"status.hostIP",
 				"status.podIP":
 				return label, value, nil
 				// This is for backwards compatibility with old v1 clients which send spec.host

pkg/api/validation/validation.go

@@ -1416,7 +1416,7 @@ func ValidateEnv(vars []api.EnvVar, fldPath *field.Path) field.ErrorList {
 	return allErrs
 }
 
-var validFieldPathExpressionsEnv = sets.NewString("metadata.name", "metadata.namespace", "spec.nodeName", "spec.serviceAccountName", "status.podIP")
+var validFieldPathExpressionsEnv = sets.NewString("metadata.name", "metadata.namespace", "spec.nodeName", "spec.serviceAccountName", "status.hostIP", "status.podIP")
 var validContainerResourceFieldPathExpressions = sets.NewString("limits.cpu", "limits.memory", "requests.cpu", "requests.memory")
 
 func validateEnvVarValueFrom(ev api.EnvVar, fldPath *field.Path) field.ErrorList {

pkg/api/validation/validation_test.go

@@ -2153,6 +2153,24 @@ func TestValidateEnv(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name: "abc",
+			ValueFrom: &api.EnvVarSource{
+				FieldRef: &api.ObjectFieldSelector{
+					APIVersion: api.Registry.GroupOrDie(api.GroupName).GroupVersion.String(),
+					FieldPath:  "status.hostIP",
+				},
+			},
+		},
+		{
+			Name: "abc",
+			ValueFrom: &api.EnvVarSource{
+				FieldRef: &api.ObjectFieldSelector{
+					APIVersion: api.Registry.GroupOrDie(api.GroupName).GroupVersion.String(),
+					FieldPath:  "status.podIP",
+				},
+			},
+		},
 		{
 			Name: "secret_value",
 			ValueFrom: &api.EnvVarSource{
@@ -2328,7 +2346,7 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.podIP`,
+			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.labels": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.hostIP, status.podIP`,
 		},
 		{
 			name: "invalid fieldPath annotations",
@@ -2341,7 +2359,7 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.podIP`,
+			expectedError: `[0].valueFrom.fieldRef.fieldPath: Unsupported value: "metadata.annotations": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.hostIP, status.podIP`,
 		},
 		{
 			name: "unsupported fieldPath",
@@ -2354,7 +2372,7 @@ func TestValidateEnv(t *testing.T) {
 					},
 				},
 			}},
-			expectedError: `valueFrom.fieldRef.fieldPath: Unsupported value: "status.phase": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.podIP`,
+			expectedError: `valueFrom.fieldRef.fieldPath: Unsupported value: "status.phase": supported values: metadata.name, metadata.namespace, spec.nodeName, spec.serviceAccountName, status.hostIP, status.podIP`,
 		},
 	}
 	for _, tc := range errorCases {

pkg/fieldpath/fieldpath.go

@@ -41,11 +41,6 @@ func FormatMap(m map[string]string) (fmtStr string) {
 // ExtractFieldPathAsString extracts the field from the given object
 // and returns it as a string.  The object must be a pointer to an
 // API type.
-//
-// Currently, this API is limited to supporting the fieldpaths:
-//
-// 1.  metadata.name - The name of an API object
-// 2.  metadata.namespace - The namespace of an API object
 func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error) {
 	accessor, err := meta.Accessor(obj)
 	if err != nil {

pkg/kubelet/kubelet_pods.go

@@ -617,6 +617,8 @@ func (kl *Kubelet) podFieldSelectorRuntimeValue(fs *v1.ObjectFieldSelector, pod
 		return pod.Spec.NodeName, nil
 	case "spec.serviceAccountName":
 		return pod.Spec.ServiceAccountName, nil
+	case "status.hostIP":
+		return pod.Status.HostIP, nil
 	case "status.podIP":
 		return podIP, nil
 	}

test/e2e/common/downward_api.go

@@ -73,11 +73,19 @@ var _ = framework.KubeDescribe("Downward API", func() {
 						FieldPath:  "status.podIP",
 					},
 				},
+				Name: "HOST_IP",
+				ValueFrom: &v1.EnvVarSource{
+					FieldRef: &v1.ObjectFieldSelector{
+						APIVersion: "v1",
+						FieldPath:  "status.hostIP",
+					},
+				},
 			},
 		}
 
 		expectations := []string{
 			"POD_IP=(?:\\d+)\\.(?:\\d+)\\.(?:\\d+)\\.(?:\\d+)",
+			"HOST_IP=(?:\\d+)\\.(?:\\d+)\\.(?:\\d+)\\.(?:\\d+)",
 		}
 
 		testDownwardAPI(f, podName, env, expectations)

test/fixtures/doc-yaml/user-guide/downward-api/dapi-pod.yaml

@@ -20,4 +20,8 @@ spec:
           valueFrom:
             fieldRef:
               fieldPath: status.podIP
+        - name: MY_HOST_IP
+          valueFrom:
+            fieldRef:
+               fieldPath: status.hostIP
   restartPolicy: Never