add client labels to k8s plugin metadata (#6475)

Signed-off-by: Nolan Miles <nolanpmiles@gmail.com>

plugin/kubernetes/README.md

@@ -207,9 +207,11 @@ plugin is also enabled:
  * `kubernetes/service`: the service name in the query
  * `kubernetes/client-namespace`: the client pod's namespace (see requirements below)
  * `kubernetes/client-pod-name`: the client pod's name (see requirements below)
+ * `kubernetes/client-label/<label key>`: a label on the client pod (see requirements below)
 
-The `kubernetes/client-namespace` and `kubernetes/client-pod-name` metadata work by reconciling the
-client IP address in the DNS request packet to a known pod IP address. Therefore the following is required:
+The `kubernetes/client-namespace`, `kubernetes/client-pod-name`, and `kubernetes/client-label/<label key>`
+metadata work by reconciling the client IP address in the DNS request packet to a known pod IP address.
+Therefore the following is required:
  * `pods verified` mode must be enabled
  * the remote IP address in the DNS packet received by CoreDNS must be the IP address
    of the Pod that sent the request.

plugin/kubernetes/handler_test.go

@@ -580,7 +580,13 @@ func (APIConnServeTest) PodIndex(ip string) []*object.Pod {
 		return []*object.Pod{}
 	}
 	a := []*object.Pod{
-		{Namespace: "podns", Name: "foo", PodIP: "10.240.0.1"}, // Remote IP set in test.ResponseWriter
+		{
+			Namespace: "podns", Name: "foo", PodIP: "10.240.0.1",
+			Labels: map[string]string{
+				"app.kubernetes.io/name": "foo",
+				"bar":                    "baz",
+			},
+		}, // Remote IP set in test.ResponseWriter
 	}
 	return a
 }

plugin/kubernetes/metadata.go

@@ -19,6 +19,13 @@ func (k *Kubernetes) Metadata(ctx context.Context, state request.Request) contex
 		metadata.SetValueFunc(ctx, "kubernetes/client-pod-name", func() string {
 			return pod.Name
 		})
+
+		for k, v := range pod.Labels {
+			v := v
+			metadata.SetValueFunc(ctx, "kubernetes/client-label/"+k, func() string {
+				return v
+			})
+		}
 	}
 
 	zone := plugin.Zones(k.Zones).Matches(state.Name())

plugin/kubernetes/metadata_test.go

@@ -141,8 +141,10 @@ func TestMetadataPodsVerified(t *testing.T) {
 	k.Metadata(ctx, state)
 
 	expect := map[string]string{
-		"kubernetes/client-namespace": "podns",
-		"kubernetes/client-pod-name":  "foo",
+		"kubernetes/client-namespace":                    "podns",
+		"kubernetes/client-pod-name":                     "foo",
+		"kubernetes/client-label/app.kubernetes.io/name": "foo",
+		"kubernetes/client-label/bar":                    "baz",
 	}
 
 	md := make(map[string]string)

plugin/kubernetes/object/pod.go

@@ -16,6 +16,7 @@ type Pod struct {
 	PodIP     string
 	Name      string
 	Namespace string
+	Labels    map[string]string
 
 	*Empty
 }
@@ -33,6 +34,7 @@ func ToPod(obj meta.Object) (meta.Object, error) {
 		PodIP:     apiPod.Status.PodIP,
 		Namespace: apiPod.GetNamespace(),
 		Name:      apiPod.GetName(),
+		Labels:    apiPod.GetLabels(),
 	}
 	t := apiPod.ObjectMeta.DeletionTimestamp
 	if t != nil && !(*t).Time.IsZero() {