Refactor filterCN to use a Set instead of map[string]bool

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
(cherry picked from commit 95797c4)
Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

pkg/cluster/address_controller.go

@@ -8,20 +8,17 @@ import (
 	controllerv1 "github.com/rancher/wrangler/v3/pkg/generated/controllers/core/v1"
 	"github.com/sirupsen/logrus"
 	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/util/sets"
 )
 
 func registerAddressHandlers(ctx context.Context, c *Cluster) {
 	nodes := c.config.Runtime.Core.Core().V1().Node()
 	a := &addressesHandler{
 		nodeController: nodes,
-		allowed:        map[string]bool{},
+		allowed:        sets.New(c.config.SANs...),
 	}
 
-	for _, cn := range c.config.SANs {
-		a.allowed[cn] = true
-	}
-
-	logrus.Infof("Starting dynamiclistener CN filter node controller")
+	logrus.Infof("Starting dynamiclistener CN filter node controller with SANs: %v", c.config.SANs)
 	nodes.OnChange(ctx, "server-cn-filter", a.sync)
 	c.cnFilterFunc = a.filterCN
 }
@@ -30,40 +27,30 @@ type addressesHandler struct {
 	sync.RWMutex
 
 	nodeController controllerv1.NodeController
-	allowed        map[string]bool
+	allowed        sets.Set[string]
 }
 
 // filterCN filters a list of potential server CNs (hostnames or IPs), removing any which do not correspond to
 // valid cluster servers (control-plane or etcd), or an address explicitly added via the tls-san option.
 func (a *addressesHandler) filterCN(cns ...string) []string {
-	if !a.nodeController.Informer().HasSynced() {
+	if len(cns) == 0 || !a.nodeController.Informer().HasSynced() {
 		return cns
 	}
 
 	a.RLock()
 	defer a.RUnlock()
 
-	filteredCNs := make([]string, 0, len(cns))
-	for _, cn := range cns {
-		if a.allowed[cn] {
-			filteredCNs = append(filteredCNs, cn)
-		} else {
-			logrus.Debugf("CN filter controller rejecting certificate CN: %s", cn)
-		}
-	}
-	return filteredCNs
+	return a.allowed.Intersection(sets.New(cns...)).UnsortedList()
 }
 
 // sync updates the allowed address list to include addresses for the node
 func (a *addressesHandler) sync(key string, node *v1.Node) (*v1.Node, error) {
-	if node != nil {
-		if node.Labels[util.ControlPlaneRoleLabelKey] != "" || node.Labels[util.ETCDRoleLabelKey] != "" {
-			a.Lock()
-			defer a.Unlock()
+	if node != nil && (node.Labels[util.ControlPlaneRoleLabelKey] != "" || node.Labels[util.ETCDRoleLabelKey] != "") {
+		a.Lock()
+		defer a.Unlock()
 
-			for _, address := range node.Status.Addresses {
-				a.allowed[address.String()] = true
-			}
+		for _, address := range node.Status.Addresses {
+			a.allowed.Insert(address.String())
 		}
 	}
 	return node, nil