Limit critical pods to kube-system by default

cluster/gce/addons/admission-resource-quota-critical-pods/resource-quota.yaml

@@ -0,0 +1,18 @@
+# critical pods are configured as a limited resource by admission_controller_config.yaml,
+# which means they are disallowed unless explicitly allowed by a namespaced quota object.
+# This quota effectively removes the restriction on the number of critical pods allowed in the kube-system namespace.
+apiVersion: v1
+kind: ResourceQuota
+metadata:
+  name: gcp-critical-pods
+  namespace: kube-system
+  labels:
+    addonmanager.kubernetes.io/mode: Reconcile
+spec:
+  hard:
+    pods: "1000000000"
+  scopeSelector:
+    matchExpressions:
+    - operator : In
+      scopeName: PriorityClass
+      values: ["system-node-critical", "system-cluster-critical"]

cluster/gce/gci/configure-helper.sh

@@ -915,6 +915,20 @@ kind: AdmissionConfiguration
 plugins:
 EOF
 
+    # Add resourcequota config to limit critical pods to kube-system by default
+    cat <<EOF >>/etc/srv/kubernetes/admission_controller_config.yaml
+- name: "ResourceQuota"
+  configuration:
+    apiVersion: apiserver.config.k8s.io/v1
+    kind: ResourceQuotaConfiguration
+    limitedResources:
+    - resource: pods
+      matchScopes:
+      - scopeName: PriorityClass 
+        operator: In
+        values: ["system-node-critical", "system-cluster-critical"]
+EOF
+
     if [[ "${ADMISSION_CONTROL:-}" == *"ImagePolicyWebhook"* ]]; then
       if [[ -z "${GCP_IMAGE_VERIFICATION_URL:-}" ]]; then
         1>&2 echo "The ImagePolicyWebhook admission control plugin was requested, but GCP_IMAGE_VERIFICATION_URL was not provided."
@@ -2528,6 +2542,7 @@ EOF
   if echo "${ADMISSION_CONTROL:-}" | grep -q "LimitRanger"; then
     setup-addon-manifests "admission-controls" "limit-range" "gce"
   fi
+  setup-addon-manifests "addons" "admission-resource-quota-critical-pods"
   if [[ "${NETWORK_POLICY_PROVIDER:-}" == "calico" ]]; then
     setup-addon-manifests "addons" "calico-policy-controller"