Add --create-nat gke-deployer flag

kubetest2-gke/deployer/down.go

@@ -17,6 +17,7 @@ limitations under the License.
 package deployer
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 
@@ -55,13 +56,27 @@ func (d *Deployer) Down() error {
 		klog.V(1).Infof("Deleted %d network firewall rules", numDeletedFWRules)
 	}
 
-	if err := d.TeardownNetwork(); err != nil {
-		return err
+	errCleanNat := d.CleanupNat()
+	if errCleanNat != nil {
+		klog.Errorf("Error cleaning up NAT: %v", errCleanNat)
 	}
-	if err := d.DeleteSubnets(d.retryCount); err != nil {
-		return err
+
+	errTeardownNetwork := d.TeardownNetwork()
+	if errTeardownNetwork != nil {
+		klog.Errorf("Error tearing down network: %v", errTeardownNetwork)
+	}
+
+	errDeleteSubnets := d.DeleteSubnets(d.retryCount)
+	if errDeleteSubnets != nil {
+		klog.Errorf("Error deleting subnets: %v", errDeleteSubnets)
+	}
+
+	errDeleteNetwork := d.DeleteNetwork()
+	if errDeleteNetwork != nil {
+		klog.Errorf("Error deleting network: %v", errDeleteNetwork)
 	}
-	return d.DeleteNetwork()
+
+	return errors.Join(errCleanFirewalls, errCleanNat, errTeardownNetwork, errDeleteSubnets, errDeleteNetwork)
 }
 
 func (d *Deployer) DeleteClusters(retryCount int) {

kubetest2-gke/deployer/nat.go

@@ -0,0 +1,98 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package deployer
+
+import (
+	"fmt"
+
+	"k8s.io/klog/v2"
+	"sigs.k8s.io/kubetest2/pkg/exec"
+)
+
+func (d *Deployer) EnsureNat() error {
+	if !d.CreateNat {
+		return nil
+	}
+	if d.Network == "default" {
+		return fmt.Errorf("NAT router should be set manually for the default network")
+	}
+	region := regionFromLocation(d.Regions, d.Zones, d.retryCount)
+	nat := d.getNatName()
+	hostProject := d.Projects[0]
+
+	if runWithNoOutput(exec.Command("gcloud", "compute", "routers", "describe", nat,
+		"--project="+hostProject,
+		"--region="+region,
+		"--format=value(name)")) != nil {
+		klog.V(1).Infof("Couldn't describe router '%s', assuming it doesn't exist and creating it", nat)
+		if err := runWithOutput(exec.Command("gcloud", "compute", "routers", "create", nat,
+			"--project="+hostProject,
+			"--network="+d.Network,
+			"--region="+region)); err != nil {
+			return fmt.Errorf("error creating NAT router: %w", err)
+		}
+	}
+	// Create this unique NAT configuration only if it does not exist yet.
+	if runWithNoOutput(exec.Command("gcloud", "compute", "routers", "nats", "describe", nat,
+		"--project="+hostProject,
+		"--router="+nat,
+		"--region="+region,
+		"--format=value(name)")) != nil {
+		klog.V(1).Infof("Couldn't describe NAT '%s', assuming it doesn't exist and creating it", nat)
+		if err := runWithOutput(exec.Command("gcloud", "compute", "routers", "nats", "create", nat,
+			"--project="+hostProject,
+			"--router="+nat,
+			"--region="+region,
+			"--auto-allocate-nat-external-ips",
+			"--nat-primary-subnet-ip-ranges")); err != nil {
+			return fmt.Errorf("error adding NAT to a router: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func (d *Deployer) getNatName() string {
+	return "nat-router-" + d.Clusters[0]
+}
+
+func (d *Deployer) CleanupNat() error {
+	if !d.CreateNat {
+		return nil
+	}
+	region := regionFromLocation(d.Regions, d.Zones, d.retryCount)
+	nat := d.getNatName()
+	hostProject := d.Projects[0]
+
+	// Delete NAT router. That will remove NAT configuration as well.
+	if runWithNoOutput(exec.Command("gcloud", "compute", "routers", "describe", nat,
+		"--project="+hostProject,
+		"--region="+region,
+		"--format=value(name)")) == nil {
+		klog.V(1).Infof("Found NAT router '%s', deleting", nat)
+		err := runWithOutput(exec.Command("gcloud", "compute", "routers", "delete", "-q", nat,
+			"--project="+hostProject,
+			"--region="+region))
+		if err != nil {
+			return fmt.Errorf("error deleting NAT router: %w", err)
+		}
+	} else {
+		klog.V(1).Infof("Found no NAT router '%s', assuming resources are clean", nat)
+	}
+
+	return nil
+}

kubetest2-gke/deployer/options/network.go

@@ -25,4 +25,5 @@ type NetworkOptions struct {
 	EnableULAInternalIPv6        bool     `flag:"~enable-ula-internal-ipv6" desc:"Enable Unique Local IPv6 Addresses (ULA). Adds the --enable-ula-internal-ipv6 flag to the gcloud compute networks create command"`
 
 	RemoveNetwork bool `flag:"~remove-network" desc:"At the end of the test remove non-default network that was used by cluster. The 'default' network is never deleted. Defaults to true if not provided."`
+	CreateNat     bool `flag:"~create-nat" desc:"Configure Cloud NAT allowing outbound connections in cluster with private nodes."`
 }

kubetest2-gke/deployer/up.go

@@ -334,6 +334,9 @@ func (d *Deployer) TestSetup() error {
 	if err := d.EnsureFirewallRules(); err != nil {
 		return err
 	}
+	if err := d.EnsureNat(); err != nil {
+		return err
+	}
 	d.testPrepared = true
 	return nil
 }