loadbalancer: resolve ControlPlaneEndpoint.Host when needed

`ControlPlaneEndpoint.Host` is not guaranteed to be an IP address, it
can also be an hostname.

Now we'll try to lookup the hostname if it's not an IP and set that for
the LB VipAddress.

pkg/cloud/services/loadbalancer/loadbalancer.go

@@ -17,8 +17,10 @@ limitations under the License.
 package loadbalancer
 
 import (
+	"context"
 	"errors"
 	"fmt"
+	"net"
 	"reflect"
 	"time"
 
@@ -27,7 +29,7 @@ import (
 	"github.com/gophercloud/gophercloud/openstack/loadbalancer/v2/monitors"
 	"github.com/gophercloud/gophercloud/openstack/loadbalancer/v2/pools"
 	"k8s.io/apimachinery/pkg/util/wait"
-	"k8s.io/utils/net"
+	utilsnet "k8s.io/utils/net"
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
 	"sigs.k8s.io/cluster-api/util"
 
@@ -42,10 +44,28 @@ import (
 const (
 	networkPrefix   string = "k8s-clusterapi"
 	kubeapiLBSuffix string = "kubeapi"
+	resolvedMsg     string = "ControlPlaneEndpoint.Host is not an IP address, using the first resolved IP address"
 )
 
 const loadBalancerProvisioningStatusActive = "ACTIVE"
 
+// We wrap the LookupHost function in a variable to allow overriding it in unit tests.
+//
+//nolint:gocritic
+var lookupHost = func(host string) (string, error) {
+	ctx, cancel := context.WithTimeout(context.TODO(), 30*time.Second)
+	defer cancel()
+	ips, err := net.DefaultResolver.LookupHost(ctx, host)
+	if err != nil {
+		return "", err
+	}
+	if ip := net.ParseIP(ips[0]); ip == nil {
+		return "", fmt.Errorf("failed to resolve IP address for host %s", host)
+	}
+	return ips[0], nil
+}
+
+// ReconcileLoadBalancer reconciles the load balancer for the given cluster.
 func (s *Service) ReconcileLoadBalancer(openStackCluster *infrav1.OpenStackCluster, clusterName string, apiServerPort int) (bool, error) {
 	loadBalancerName := getLoadBalancerName(clusterName)
 	s.scope.Logger().Info("Reconciling load balancer", "name", loadBalancerName)
@@ -57,13 +77,18 @@ func (s *Service) ReconcileLoadBalancer(openStackCluster *infrav1.OpenStackClust
 	}
 
 	var fixedIPAddress string
+	var err error
+
 	switch {
 	case lbStatus.InternalIP != "":
 		fixedIPAddress = lbStatus.InternalIP
 	case openStackCluster.Spec.APIServerFixedIP != "":
 		fixedIPAddress = openStackCluster.Spec.APIServerFixedIP
 	case openStackCluster.Spec.DisableAPIServerFloatingIP && openStackCluster.Spec.ControlPlaneEndpoint.IsValid():
-		fixedIPAddress = openStackCluster.Spec.ControlPlaneEndpoint.Host
+		fixedIPAddress, err = lookupHost(openStackCluster.Spec.ControlPlaneEndpoint.Host)
+		if err != nil {
+			return false, fmt.Errorf("lookup host: %w", err)
+		}
 	}
 
 	providers, err := s.loadbalancerClient.ListLoadBalancerProviders()
@@ -108,7 +133,10 @@ func (s *Service) ReconcileLoadBalancer(openStackCluster *infrav1.OpenStackClust
 		case openStackCluster.Spec.APIServerFloatingIP != "":
 			floatingIPAddress = openStackCluster.Spec.APIServerFloatingIP
 		case openStackCluster.Spec.ControlPlaneEndpoint.IsValid():
-			floatingIPAddress = openStackCluster.Spec.ControlPlaneEndpoint.Host
+			floatingIPAddress, err = lookupHost(openStackCluster.Spec.ControlPlaneEndpoint.Host)
+			if err != nil {
+				return false, fmt.Errorf("lookup host: %w", err)
+			}
 		}
 		fp, err := s.networkingService.GetOrCreateFloatingIP(openStackCluster, openStackCluster, clusterName, floatingIPAddress)
 		if err != nil {
@@ -307,9 +335,9 @@ func validateIPs(openStackCluster *infrav1.OpenStackCluster, definedCIDRs []stri
 
 	for _, v := range definedCIDRs {
 		switch {
-		case net.IsIPv4String(v):
+		case utilsnet.IsIPv4String(v):
 			marshaledCIDRs = append(marshaledCIDRs, v+"/32")
-		case net.IsIPv4CIDRString(v):
+		case utilsnet.IsIPv4CIDRString(v):
 			marshaledCIDRs = append(marshaledCIDRs, v)
 		default:
 			record.Warnf(openStackCluster, "FailedIPAddressValidation", "%s is not a valid IPv4 nor CIDR address and will not get applied to allowed_cidrs", v)

pkg/cloud/services/loadbalancer/loadbalancer_test.go

@@ -17,6 +17,8 @@ limitations under the License.
 package loadbalancer
 
 import (
+	"errors"
+	"net"
 	"testing"
 
 	"github.com/go-logr/logr"
@@ -28,6 +30,7 @@ import (
 	"github.com/gophercloud/gophercloud/openstack/loadbalancer/v2/pools"
 	"github.com/gophercloud/gophercloud/openstack/loadbalancer/v2/providers"
 	. "github.com/onsi/gomega"
+	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
 
 	infrav1 "sigs.k8s.io/cluster-api-provider-openstack/api/v1alpha8"
 	"sigs.k8s.io/cluster-api-provider-openstack/pkg/clients/mock"
@@ -38,9 +41,24 @@ func Test_ReconcileLoadBalancer(t *testing.T) {
 	mockCtrl := gomock.NewController(t)
 	defer mockCtrl.Finish()
 
+	// Stub the call to net.LookupHost
+	lookupHost = func(host string) (addrs string, err error) {
+		if net.ParseIP(host) != nil {
+			return host, nil
+		} else if host == "api.test-cluster.test" {
+			ips := []string{"192.168.100.10"}
+			return ips[0], nil
+		}
+		return "", errors.New("Unknown Host " + host)
+	}
+
 	openStackCluster := &infrav1.OpenStackCluster{
 		Spec: infrav1.OpenStackClusterSpec{
 			DisableAPIServerFloatingIP: true,
+			ControlPlaneEndpoint: clusterv1.APIEndpoint{
+				Host: "api.test-cluster.test",
+				Port: 6443,
+			},
 		},
 		Status: infrav1.OpenStackClusterStatus{
 			ExternalNetwork: &infrav1.NetworkStatus{