✨ Add EKS Control Plane private subnet restriction flag

config/crd/bases/controlplane.cluster.x-k8s.io_awsmanagedcontrolplanes.yaml

@@ -2832,6 +2832,11 @@ spec:
               region:
                 description: The AWS Region the cluster lives in.
                 type: string
+              restrictPrivateSubnets:
+                default: false
+                description: RestrictPrivateSubnets indicates that the EKS control
+                  plane should only use private subnets.
+                type: boolean
               roleAdditionalPolicies:
                 description: |-
                   RoleAdditionalPolicies allows you to attach additional polices to

controlplane/eks/api/v1beta1/conversion.go

@@ -40,6 +40,7 @@ func (r *AWSManagedControlPlane) ConvertTo(dstRaw conversion.Hub) error {
 	}
 	dst.Spec.VpcCni.Disable = r.Spec.DisableVPCCNI
 	dst.Spec.Partition = restored.Spec.Partition
+	dst.Spec.RestrictPrivateSubnets = restored.Spec.RestrictPrivateSubnets
 
 	return nil
 }

controlplane/eks/api/v1beta2/awsmanagedcontrolplane_types.go

@@ -173,6 +173,10 @@ type AWSManagedControlPlaneSpec struct { //nolint: maligned
 	// +optional
 	VpcCni VpcCni `json:"vpcCni,omitempty"`
 
+	// RestrictPrivateSubnets indicates that the EKS control plane should only use private subnets.
+	// +kubebuilder:default=false
+	RestrictPrivateSubnets bool `json:"restrictPrivateSubnets,omitempty"`
+
 	// KubeProxy defines managed attributes of the kube-proxy daemonset
 	KubeProxy KubeProxy `json:"kubeProxy,omitempty"`
 }

controlplane/eks/api/v1beta2/awsmanagedcontrolplane_webhook.go

@@ -91,6 +91,7 @@ func (r *AWSManagedControlPlane) ValidateCreate() (admission.Warnings, error) {
 	allErrs = append(allErrs, r.validateSecondaryCIDR()...)
 	allErrs = append(allErrs, r.validateEKSAddons()...)
 	allErrs = append(allErrs, r.validateDisableVPCCNI()...)
+	allErrs = append(allErrs, r.validateRestrictPrivateSubnets()...)
 	allErrs = append(allErrs, r.validateKubeProxy()...)
 	allErrs = append(allErrs, r.Spec.AdditionalTags.Validate()...)
 	allErrs = append(allErrs, r.validateNetwork()...)
@@ -126,6 +127,7 @@ func (r *AWSManagedControlPlane) ValidateUpdate(old runtime.Object) (admission.W
 	allErrs = append(allErrs, r.validateSecondaryCIDR()...)
 	allErrs = append(allErrs, r.validateEKSAddons()...)
 	allErrs = append(allErrs, r.validateDisableVPCCNI()...)
+	allErrs = append(allErrs, r.validateRestrictPrivateSubnets()...)
 	allErrs = append(allErrs, r.validateKubeProxy()...)
 	allErrs = append(allErrs, r.Spec.AdditionalTags.Validate()...)
 	allErrs = append(allErrs, r.validatePrivateDNSHostnameTypeOnLaunch()...)
@@ -392,6 +394,22 @@ func (r *AWSManagedControlPlane) validateDisableVPCCNI() field.ErrorList {
 	return allErrs
 }
 
+func (r *AWSManagedControlPlane) validateRestrictPrivateSubnets() field.ErrorList {
+	var allErrs field.ErrorList
+
+	if r.Spec.RestrictPrivateSubnets && r.Spec.NetworkSpec.VPC.IsUnmanaged(r.Spec.EKSClusterName) {
+		boolField := field.NewPath("spec", "restrictPrivateSubnets")
+		if len(r.Spec.NetworkSpec.Subnets.FilterPrivate()) == 0 {
+			allErrs = append(allErrs, field.Invalid(boolField, r.Spec.RestrictPrivateSubnets, "cannot enable private subnets restriction when no private subnets are specified"))
+		}
+	}
+
+	if len(allErrs) == 0 {
+		return nil
+	}
+	return allErrs
+}
+
 func (r *AWSManagedControlPlane) validatePrivateDNSHostnameTypeOnLaunch() field.ErrorList {
 	var allErrs field.ErrorList
 

pkg/cloud/scope/managedcontrolplane.go

@@ -407,6 +407,11 @@ func (s *ManagedControlPlaneScope) VpcCni() ekscontrolplanev1.VpcCni {
 	return s.ControlPlane.Spec.VpcCni
 }
 
+// RestrictPrivateSubnets returns whether Control Plane should be restricted to Private subnets.
+func (s *ManagedControlPlaneScope) RestrictPrivateSubnets() bool {
+	return s.ControlPlane.Spec.RestrictPrivateSubnets
+}
+
 // OIDCIdentityProviderConfig returns the OIDC identity provider config.
 func (s *ManagedControlPlaneScope) OIDCIdentityProviderConfig() *ekscontrolplanev1.OIDCIdentityProviderConfig {
 	return s.ControlPlane.Spec.OIDCIdentityProviderConfig

pkg/cloud/services/eks/cluster.go

@@ -359,9 +359,18 @@ func makeEksLogging(loggingSpec *ekscontrolplanev1.ControlPlaneLoggingSpec) *eks
 }
 
 func (s *Service) createCluster(eksClusterName string) (*eks.Cluster, error) {
+	var (
+		vpcConfig *eks.VpcConfigRequest
+		err       error
+	)
 	logging := makeEksLogging(s.scope.ControlPlane.Spec.Logging)
 	encryptionConfigs := makeEksEncryptionConfigs(s.scope.ControlPlane.Spec.EncryptionConfig)
-	vpcConfig, err := makeVpcConfig(s.scope.Subnets(), s.scope.ControlPlane.Spec.EndpointAccess, s.scope.SecurityGroups())
+	if s.scope.ControlPlane.Spec.RestrictPrivateSubnets {
+		s.scope.Info("Filtering private subnets")
+		vpcConfig, err = makeVpcConfig(s.scope.Subnets().FilterPrivate(), s.scope.ControlPlane.Spec.EndpointAccess, s.scope.SecurityGroups())
+	} else {
+		vpcConfig, err = makeVpcConfig(s.scope.Subnets(), s.scope.ControlPlane.Spec.EndpointAccess, s.scope.SecurityGroups())
+	}
 	if err != nil {
 		return nil, errors.Wrap(err, "couldn't create vpc config for cluster")
 	}
@@ -542,8 +551,16 @@ func publicAccessCIDRsEqual(as []*string, bs []*string) bool {
 }
 
 func (s *Service) reconcileVpcConfig(vpcConfig *eks.VpcConfigResponse) (*eks.VpcConfigRequest, error) {
+	var (
+		updatedVpcConfig *eks.VpcConfigRequest
+		err              error
+	)
 	endpointAccess := s.scope.ControlPlane.Spec.EndpointAccess
-	updatedVpcConfig, err := makeVpcConfig(s.scope.Subnets(), endpointAccess, s.scope.SecurityGroups())
+	if s.scope.ControlPlane.Spec.RestrictPrivateSubnets {
+		updatedVpcConfig, err = makeVpcConfig(s.scope.Subnets().FilterPrivate(), endpointAccess, s.scope.SecurityGroups())
+	} else {
+		updatedVpcConfig, err = makeVpcConfig(s.scope.Subnets(), endpointAccess, s.scope.SecurityGroups())
+	}
 	if err != nil {
 		return nil, err
 	}