add comments for compatibility

cmd/kube-controller-manager/app/core.go

@@ -159,8 +159,12 @@ func startNodeIpamController(ctx ControllerContext) (http.Handler, bool, error)
 
 	var nodeCIDRMaskSizeIPv4, nodeCIDRMaskSizeIPv6 int
 	if utilfeature.DefaultFeatureGate.Enabled(kubefeatures.IPv6DualStack) {
+		// only --node-cidr-mask-size-ipv4 and --node-cidr-mask-size-ipv6 supported with dual stack clusters.
+		// --node-cidr-mask-size flag is incompatible with dual stack clusters.
 		nodeCIDRMaskSizeIPv4, nodeCIDRMaskSizeIPv6, err = setNodeCIDRMaskSizesDualStack(ctx.ComponentConfig.NodeIPAMController)
 	} else {
+		// only --node-cidr-mask-size supported with single stack clusters.
+		// --node-cidr-mask-size-ipv4 and --node-cidr-mask-size-ipv6 flags are incompatible with dual stack clusters.
 		nodeCIDRMaskSizeIPv4, nodeCIDRMaskSizeIPv6, err = setNodeCIDRMaskSizes(ctx.ComponentConfig.NodeIPAMController)
 	}
 
@@ -623,12 +627,13 @@ func setNodeCIDRMaskSizesDualStack(cfg nodeipamconfig.NodeIPAMControllerConfigur
 // getNodeCIDRMaskSizes is a helper function that helps the generate the node cidr mask
 // sizes slice based on the cluster cidr slice
 func getNodeCIDRMaskSizes(clusterCIDRs []*net.IPNet, maskSizeIPv4, maskSizeIPv6 int) []int {
-	nodeMaskCIDRs := []int{}
-	for _, clusterCIDR := range clusterCIDRs {
+	nodeMaskCIDRs := make([]int, len(clusterCIDRs))
+
+	for idx, clusterCIDR := range clusterCIDRs {
 		if netutils.IsIPv6CIDR(clusterCIDR) {
-			nodeMaskCIDRs = append(nodeMaskCIDRs, maskSizeIPv6)
+			nodeMaskCIDRs[idx] = maskSizeIPv6
 		} else {
-			nodeMaskCIDRs = append(nodeMaskCIDRs, maskSizeIPv4)
+			nodeMaskCIDRs[idx] = maskSizeIPv4
 		}
 	}
 	return nodeMaskCIDRs

pkg/controller/nodeipam/config/types.go

@@ -23,9 +23,12 @@ type NodeIPAMControllerConfiguration struct {
 	// secondaryServiceCIDR is CIDR Range for Services in cluster. This is used in dual stack clusters. SecondaryServiceCIDR must be of different IP family than ServiceCIDR
 	SecondaryServiceCIDR string
 	// NodeCIDRMaskSize is the mask size for node cidr in single-stack cluster.
+	// This can be used only with single stack clusters and is incompatible with dual stack clusters.
 	NodeCIDRMaskSize int32
-	// NodeCIDRMaskSizeIPv4 is the mask size for node cidr in dual-stack cluster.
+	// NodeCIDRMaskSizeIPv4 is the mask size for IPv4 node cidr in dual-stack cluster.
+	// This can be used only with dual stack clusters and is incompatible with single stack clusters.
 	NodeCIDRMaskSizeIPv4 int32
-	// NodeCIDRMaskSizeIPv6 is the mask size for node cidr in dual-stack cluster.
+	// NodeCIDRMaskSizeIPv6 is the mask size for IPv6 node cidr in dual-stack cluster.
+	// This can be used only with dual stack clusters and is incompatible with single stack clusters.
 	NodeCIDRMaskSizeIPv6 int32
 }