Add ClusterClaim deletion validator

1. Refine ClusterClaim webhook, add deletion validator to deny deletion
   if there is any ClusterSet referring to it.
2. Move status data initialization from leader ClusterSet controller to
MemberClusterAnnounce controller and simplify the status:
* When the MemberClusterAnnounce is created, the `Ready` status will be
  true and `Reason` will be `Connected`.
* When the MemberClusterAnnounce is not updated in the agreed period,
  the `Ready` status will be false and `Reason` will be disconnected.
* When the MemberCLusterAnnounce is deleted, the corresponding status
  will be removed.

Signed-off-by: Lan Luo <luola@vmware.com>

multicluster/build/yamls/antrea-multicluster-leader-namespaced.yml

@@ -477,6 +477,7 @@ webhooks:
     operations:
     - CREATE
     - UPDATE
+    - DELETE
     resources:
     - clusterclaims
   sideEffects: None

multicluster/build/yamls/antrea-multicluster-member.yml

@@ -1075,6 +1075,7 @@ webhooks:
     operations:
     - CREATE
     - UPDATE
+    - DELETE
     resources:
     - clusterclaims
   sideEffects: None

multicluster/cmd/multicluster-controller/clusterclaim_webhook.go

@@ -0,0 +1,105 @@
+/*
+Copyright 2022 Antrea Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	admissionv1 "k8s.io/api/admission/v1"
+	"k8s.io/klog/v2"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	mcv1alpha1 "antrea.io/antrea/multicluster/apis/multicluster/v1alpha1"
+	mcv1alpha2 "antrea.io/antrea/multicluster/apis/multicluster/v1alpha2"
+)
+
+//+kubebuilder:webhook:path=/validate-multicluster-crd-antrea-io-v1alpha2-clusterclaim,mutating=false,failurePolicy=fail,sideEffects=None,groups=multicluster.crd.antrea.io,resources=clusterclaims,verbs=create;update;delete,versions=v1alpha2,name=vclusterclaim.kb.io,admissionReviewVersions={v1,v1beta1}
+
+// ClusterClaim validator
+type clusterClaimValidator struct {
+	Client    client.Client
+	decoder   *admission.Decoder
+	namespace string
+}
+
+// Handle handles admission requests.
+func (v *clusterClaimValidator) Handle(ctx context.Context, req admission.Request) admission.Response {
+	clusterClaim := &mcv1alpha2.ClusterClaim{}
+	err := v.decoder.Decode(req, clusterClaim)
+	if err != nil {
+		klog.ErrorS(err, "Error while decoding ClusterClaim", "ClusterClaim", req.Namespace+"/"+req.Name)
+		return admission.Errored(http.StatusBadRequest, err)
+	}
+
+	switch req.Operation {
+	case admissionv1.Create:
+		if clusterClaim.Name != mcv1alpha2.WellKnownClusterClaimClusterSet && clusterClaim.Name != mcv1alpha2.WellKnownClusterClaimID {
+			return admission.Denied(fmt.Sprintf("name %s is not valid, only 'id.k8s.io' and 'clusterset.k8s.io' are valid names for ClusterClaim\n", clusterClaim.Name))
+		}
+	case admissionv1.Update:
+		oldClusterClaim := &mcv1alpha2.ClusterClaim{}
+		if req.OldObject.Raw != nil {
+			if err := json.Unmarshal(req.OldObject.Raw, &oldClusterClaim); err != nil {
+				klog.ErrorS(err, "Error while decoding old ClusterClaim", "ClusterClaim", klog.KObj(clusterClaim))
+				return admission.Errored(http.StatusBadRequest, err)
+			}
+			if oldClusterClaim.Value != clusterClaim.Value {
+				klog.ErrorS(err, "The field 'value' is immutable", "ClusterClaim", klog.KObj(clusterClaim))
+				return admission.Denied("the field 'value' is immutable")
+			}
+			return admission.Allowed("")
+		}
+	case admissionv1.Delete:
+		clusterSetList := &mcv1alpha1.ClusterSetList{}
+		if err := v.Client.List(context.TODO(), clusterSetList, client.InNamespace(v.namespace)); err != nil {
+			klog.ErrorS(err, "Error reading ClusterSet", "Namespace", v.namespace)
+			return admission.Errored(http.StatusPreconditionFailed, err)
+		}
+		deny := false
+		var existingClusterSet mcv1alpha1.ClusterSet
+		if len(clusterSetList.Items) > 0 {
+			// ClusterSet webhook will guarantee that there is at most one ClusterSet in a given Namespace.
+			existingClusterSet = clusterSetList.Items[0]
+			if clusterClaim.Value == existingClusterSet.Name || clusterClaim.Value == existingClusterSet.Spec.Leaders[0].ClusterID {
+				deny = true
+			} else {
+				for _, member := range existingClusterSet.Spec.Members {
+					if clusterClaim.Value == member.ClusterID {
+						deny = true
+						break
+					}
+				}
+			}
+		}
+		// Deny ClusterClaim deletion if the ClusterClaim is referred in a ClusterSet.
+		if deny {
+			klog.ErrorS(err, "The ClusterClaim is referred by a ClusterSet. Cannot delete it", "ClusterClaim", klog.KObj(clusterClaim), "ClusterSet", klog.KObj(&existingClusterSet))
+			return admission.Denied(fmt.Sprintf("the ClusterClaim %s is referred by a ClusterSet %s, please delete the ClusterSet first\n", klog.KObj(clusterClaim), klog.KObj(&existingClusterSet)))
+		}
+		return admission.Allowed("")
+	}
+	return admission.Allowed("")
+}
+
+func (v *clusterClaimValidator) InjectDecoder(d *admission.Decoder) error {
+	v.decoder = d
+	return nil
+}