cmd/k8s-operator: optionally configure Connector as exit node

The Kubernetes operator parses Connector custom resource and,
if .spec.isExitNode is set, configures that Tailscale node deployed
for that connector as an exit node.

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

cmd/k8s-operator/connector.go

@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"net/netip"
 	"slices"
-	"strings"
 	"sync"
 	"time"
 
@@ -33,17 +32,16 @@ import (
 )
 
 const (
-	reasonSubnetRouterCreationFailed    = "SubnetRouterCreationFailed"
-	reasonSubnetRouterCreated           = "SubnetRouterCreated"
-	reasonSubnetRouterCleanupFailed     = "SubnetRouterCleanupFailed"
-	reasonSubnetRouterCleanupInProgress = "SubnetRouterCleanupInProgress"
-	reasonSubnetRouterInvalid           = "SubnetRouterInvalid"
-
-	messageSubnetRouterCreationFailed = "Failed creating subnet router for routes %s: %v"
-	messageSubnetRouterInvalid        = "Subnet router is invalid: %v"
-	messageSubnetRouterCreated        = "Created subnet router for routes %s"
-	messageSubnetRouterCleanupFailed  = "Failed cleaning up subnet router resources: %v"
-	msgSubnetRouterCleanupInProgress  = "SubnetRouterCleanupInProgress"
+	reasonConnectorCreationFailed = "ConnectorCreationFailed"
+
+	reasonConnectorCreated           = "ConnectorCreated"
+	reasonConnectorCleanupFailed     = "ConnectorCleanupFailed"
+	reasonConnectorCleanupInProgress = "ConnectorCleanupInProgress"
+	reasonConnectorInvalid           = "ConnectorInvalid"
+
+	messageConnectorCreationFailed   = "Failed creating Connector: %v"
+	messageConnectorInvalid          = "Connector is invalid: %v"
+	messageSubnetRouterCleanupFailed = "Failed cleaning up Connector resources: %v"
 
 	shortRequeue = time.Second * 5
 )
@@ -61,42 +59,39 @@ type ConnectorReconciler struct {
 
 	mu sync.Mutex // protects following
 
-	// subnetRouters tracks the subnet routers managed by this Tailscale
-	// Operator instance.
-	subnetRouters set.Slice[types.UID]
+	connectors set.Slice[types.UID] // for connectors gauge
 }
 
 var (
-	// gaugeIngressResources tracks the number of subnet routers that we're
-	// currently managing.
-	gaugeSubnetRouterResources = clientmetric.NewGauge("k8s_subnet_router_resources")
+	// gaugeConnectorResources tracks the number of Connectors currently managed by this operator instance
+	gaugeConnectorResources = clientmetric.NewGauge("k8s_connector_resources")
 )
 
 func (a *ConnectorReconciler) Reconcile(ctx context.Context, req reconcile.Request) (_ reconcile.Result, err error) {
-	logger := a.logger.With("connector", req.Name)
+	logger := a.logger.With("Connector", req.Name)
 	logger.Debugf("starting reconcile")
 	defer logger.Debugf("reconcile finished")
 
 	cn := new(tsapi.Connector)
 	err = a.Get(ctx, req.NamespacedName, cn)
 	if apierrors.IsNotFound(err) {
-		logger.Debugf("connector not found, assuming it was deleted")
+		logger.Debugf("Connector not found, assuming it was deleted")
 		return reconcile.Result{}, nil
 	} else if err != nil {
 		return reconcile.Result{}, fmt.Errorf("failed to get tailscale.com Connector: %w", err)
 	}
 	if !cn.DeletionTimestamp.IsZero() {
-		logger.Debugf("connector is being deleted or should not be exposed, cleaning up components")
+		logger.Debugf("Connector is being deleted or should not be exposed, cleaning up resources")
 		ix := xslices.Index(cn.Finalizers, FinalizerName)
 		if ix < 0 {
 			logger.Debugf("no finalizer, nothing to do")
 			return reconcile.Result{}, nil
 		}
 
-		if done, err := a.maybeCleanupSubnetRouter(ctx, logger, cn); err != nil {
+		if done, err := a.maybeCleanupConnector(ctx, logger, cn); err != nil {
 			return reconcile.Result{}, err
 		} else if !done {
-			logger.Debugf("cleanup not finished, will retry...")
+			logger.Debugf("Connector resource cleanup not yet finished, will retry...")
 			return reconcile.Result{RequeueAfter: shortRequeue}, nil
 		}
 
@@ -104,21 +99,20 @@ func (a *ConnectorReconciler) Reconcile(ctx context.Context, req reconcile.Reque
 		if err := a.Update(ctx, cn); err != nil {
 			return reconcile.Result{}, err
 		}
-		logger.Infof("connector resources cleaned up")
+		logger.Infof("Connector resources cleaned up")
 		return reconcile.Result{}, nil
 	}
 
+	var (
+		reason, message string
+		readyStatus     metav1.ConditionStatus
+	)
+
 	oldCnStatus := cn.Status.DeepCopy()
 	defer func() {
-		if cn.Status.SubnetRouter == nil {
-			tsoperator.SetConnectorCondition(cn, tsapi.ConnectorReady, metav1.ConditionUnknown, "", "", cn.Generation, a.clock, logger)
-		} else if cn.Status.SubnetRouter.Ready == metav1.ConditionTrue {
-			tsoperator.SetConnectorCondition(cn, tsapi.ConnectorReady, metav1.ConditionTrue, reasonSubnetRouterCreated, reasonSubnetRouterCreated, cn.Generation, a.clock, logger)
-		} else {
-			tsoperator.SetConnectorCondition(cn, tsapi.ConnectorReady, metav1.ConditionFalse, cn.Status.SubnetRouter.Reason, cn.Status.SubnetRouter.Reason, cn.Generation, a.clock, logger)
-		}
+		tsoperator.SetConnectorCondition(cn, tsapi.ConnectorReady, readyStatus, reason, message, cn.Generation, a.clock, logger)
 		if !apiequality.Semantic.DeepEqual(oldCnStatus, cn.Status) {
-			// an error encountered here should get returned by the Reconcile function
+			// An error encountered here should get returned by the Reconcile function.
 			if updateErr := a.Client.Status().Update(ctx, cn); updateErr != nil {
 				err = updateErr
 			}
@@ -130,67 +124,85 @@ func (a *ConnectorReconciler) Reconcile(ctx context.Context, req reconcile.Reque
 		// because once the finalizer is in place this block gets skipped. So,
 		// this is a nice place to tell the operator that the high level,
 		// multi-reconcile operation is underway.
-		logger.Infof("ensuring connector is set up")
+		logger.Infof("ensuring Connector is set up")
 		cn.Finalizers = append(cn.Finalizers, FinalizerName)
 		if err := a.Update(ctx, cn); err != nil {
 			err = fmt.Errorf("failed to add finalizer: %w", err)
 			logger.Errorf("error adding finalizer: %v", err)
+			reason = reasonConnectorCreationFailed
+			message = fmt.Sprintf(messageConnectorCreationFailed, err)
+			readyStatus = metav1.ConditionFalse
 			return reconcile.Result{}, err
 		}
 	}
 
-	// A Connector with unset .spec.subnetRouter and unset
-	// cn.spec.subnetRouter.Routes will be rejected at apply time (because
-	// these fields are set as required by our CRD validation). This check
-	// is here for if our CRD validation breaks unnoticed we don't crash the
-	// operator with nil pointer exception.
-	if cn.Spec.SubnetRouter == nil || len(cn.Spec.SubnetRouter.Routes) < 1 {
+	if err := a.validate(cn); err != nil {
+		logger.Errorf("error validating Connector spec: %w", err)
+		reason = reasonConnectorInvalid
+		message = fmt.Sprintf(messageConnectorInvalid, err)
+		readyStatus = metav1.ConditionFalse
+		a.recorder.Eventf(cn, corev1.EventTypeWarning, reasonConnectorInvalid, message)
 		return reconcile.Result{}, nil
 	}
 
-	if err := validateSubnetRouter(*cn.Spec.SubnetRouter); err != nil {
-		msg := fmt.Sprintf(messageSubnetRouterInvalid, err)
-		cn.Status.SubnetRouter = &tsapi.SubnetRouterStatus{
-			Ready:   metav1.ConditionFalse,
-			Reason:  reasonSubnetRouterInvalid,
-			Message: msg,
+	if err = a.maybeProvisionConnector(ctx, logger, cn); err != nil {
+		logger.Errorf("error creating Connector resources: %w", err)
+		reason = reasonConnectorCreationFailed
+		message = fmt.Sprintf(messageConnectorCreationFailed, err)
+		readyStatus = metav1.ConditionFalse
+		a.recorder.Eventf(cn, corev1.EventTypeWarning, reason, message)
+	} else {
+		logger.Info("Connector resources synced")
+		reason = reasonConnectorCreated
+		message = reasonConnectorCreated
+		readyStatus = metav1.ConditionTrue
+		cn.Status.IsExitNode = cn.Spec.ExitNode
+		if cn.Spec.SubnetRouter != nil {
+			cn.Status.SubnetRoutes = cn.Spec.SubnetRouter.Routes.Stringify()
+		} else {
+			cn.Status.SubnetRoutes = ""
 		}
-		a.recorder.Eventf(cn, corev1.EventTypeWarning, reasonSubnetRouterInvalid, msg)
-		return reconcile.Result{}, nil
 	}
+	return reconcile.Result{}, err
+}
 
-	var sb strings.Builder
-	sb.WriteString(string(cn.Spec.SubnetRouter.Routes[0]))
-	for _, r := range cn.Spec.SubnetRouter.Routes[1:] {
-		sb.WriteString(fmt.Sprintf(",%s", r))
+// maybeProvisionConnector ensures that any new resources required for this
+// Connector instance are deployed to the cluster.
+func (a *ConnectorReconciler) maybeProvisionConnector(ctx context.Context, logger *zap.SugaredLogger, cn *tsapi.Connector) error {
+	hostname := cn.Name + "-connector"
+	if cn.Spec.Hostname != "" {
+		hostname = string(cn.Spec.Hostname)
 	}
-	cidrsS := sb.String()
-	logger.Debugf("ensuring a subnet router is deployed")
-	err = a.maybeProvisionSubnetRouter(ctx, logger, cn, cidrsS)
-	if err != nil {
-		msg := fmt.Sprintf(messageSubnetRouterCreationFailed, cidrsS, err)
-		cn.Status.SubnetRouter = &tsapi.SubnetRouterStatus{
-			Ready:   metav1.ConditionFalse,
-			Reason:  reasonSubnetRouterCreationFailed,
-			Message: msg,
-		}
-		a.recorder.Eventf(cn, corev1.EventTypeWarning, reasonSubnetRouterCreationFailed, msg)
-		return reconcile.Result{}, err
+	crl := childResourceLabels(cn.Name, a.tsnamespace, "connector")
+	sts := &tailscaleSTSConfig{
+		ParentResourceName:  cn.Name,
+		ParentResourceUID:   string(cn.UID),
+		Hostname:            hostname,
+		ChildResourceLabels: crl,
+		Tags:                cn.Spec.Tags.Stringify(),
+		Connector: &connector{
+			isExitNode: cn.Spec.ExitNode,
+		},
 	}
-	cn.Status.SubnetRouter = &tsapi.SubnetRouterStatus{
-		Routes:  cidrsS,
-		Ready:   metav1.ConditionTrue,
-		Reason:  reasonSubnetRouterCreated,
-		Message: fmt.Sprintf(messageSubnetRouterCreated, cidrsS),
+
+	if cn.Spec.SubnetRouter != nil && len(cn.Spec.SubnetRouter.Routes) > 0 {
+		sts.Connector.routes = cn.Spec.SubnetRouter.Routes.Stringify()
 	}
-	return reconcile.Result{}, nil
+
+	a.mu.Lock()
+	a.connectors.Add(cn.UID)
+	gaugeConnectorResources.Set(int64(a.connectors.Len()))
+	a.mu.Unlock()
+
+	_, err := a.ssr.Provision(ctx, logger, sts)
+	return err
 }
 
-func (a *ConnectorReconciler) maybeCleanupSubnetRouter(ctx context.Context, logger *zap.SugaredLogger, cn *tsapi.Connector) (bool, error) {
-	if done, err := a.ssr.Cleanup(ctx, logger, childResourceLabels(cn.Name, a.tsnamespace, "subnetrouter")); err != nil {
-		return false, fmt.Errorf("failed to cleanup: %w", err)
+func (a *ConnectorReconciler) maybeCleanupConnector(ctx context.Context, logger *zap.SugaredLogger, cn *tsapi.Connector) (bool, error) {
+	if done, err := a.ssr.Cleanup(ctx, logger, childResourceLabels(cn.Name, a.tsnamespace, "connector")); err != nil {
+		return false, fmt.Errorf("failed to cleanup Connector resources: %w", err)
 	} else if !done {
-		logger.Debugf("cleanup not done yet, waiting for next reconcile")
+		logger.Debugf("Connector cleanup not done yet, waiting for next reconcile")
 		return false, nil
 	}
 
@@ -198,42 +210,31 @@ func (a *ConnectorReconciler) maybeCleanupSubnetRouter(ctx context.Context, logg
 	// exactly once at the very end of cleanup, because the final step of
 	// cleanup removes the tailscale finalizer, which will make all future
 	// reconciles exit early.
-	logger.Infof("cleaned up subnet router")
+	logger.Infof("cleaned up Connector resources")
 	a.mu.Lock()
 	defer a.mu.Unlock()
-	a.subnetRouters.Remove(cn.UID)
-	gaugeSubnetRouterResources.Set(int64(a.subnetRouters.Len()))
+	a.connectors.Remove(cn.UID)
+	gaugeConnectorResources.Set(int64(a.connectors.Len()))
 	return true, nil
 }
 
-// maybeProvisionSubnetRouter maybe deploys subnet router that exposes a subset of cluster cidrs to the tailnet
-func (a *ConnectorReconciler) maybeProvisionSubnetRouter(ctx context.Context, logger *zap.SugaredLogger, cn *tsapi.Connector, cidrs string) error {
-	if cn.Spec.SubnetRouter == nil || len(cn.Spec.SubnetRouter.Routes) < 1 {
+func (a *ConnectorReconciler) validate(cn *tsapi.Connector) error {
+	// Connector fields are already validated at apply time with CEL validation
+	// on custom resource fields. The checks here are a backup in case the
+	// CEL validation breaks without us noticing.
+	if !(cn.Spec.SubnetRouter != nil || cn.Spec.ExitNode) {
+		return errors.New("invalid Connector spec- a Connector must be either expose subnet routes or act as exit node (or both)")
+	}
+	if cn.Spec.SubnetRouter == nil {
 		return nil
 	}
-	a.mu.Lock()
-	a.subnetRouters.Add(cn.UID)
-	gaugeSubnetRouterResources.Set(int64(a.subnetRouters.Len()))
-	a.mu.Unlock()
+	return validateSubnetRouter(cn.Spec.SubnetRouter)
+}
 
-	crl := childResourceLabels(cn.Name, a.tsnamespace, "subnetrouter")
-	hostname := hostnameForSubnetRouter(cn)
-	sts := &tailscaleSTSConfig{
-		ParentResourceName:  cn.Name,
-		ParentResourceUID:   string(cn.UID),
-		Hostname:            hostname,
-		ChildResourceLabels: crl,
-		Routes:              cidrs,
-	}
-	for _, tag := range cn.Spec.SubnetRouter.Tags {
-		sts.Tags = append(sts.Tags, string(tag))
+func validateSubnetRouter(sb *tsapi.SubnetRouter) error {
+	if len(sb.Routes) < 1 {
+		return errors.New("invalid subnet router spec: no routes defined")
 	}
-
-	_, err := a.ssr.Provision(ctx, logger, sts)
-
-	return err
-}
-func validateSubnetRouter(sb tsapi.SubnetRouter) error {
 	var err error
 	for _, route := range sb.Routes {
 		pfx, e := netip.ParsePrefix(string(route))
@@ -247,13 +248,3 @@ func validateSubnetRouter(sb tsapi.SubnetRouter) error {
 	}
 	return err
 }
-
-func hostnameForSubnetRouter(cn *tsapi.Connector) string {
-	if cn.Spec.SubnetRouter == nil {
-		return ""
-	}
-	if cn.Spec.SubnetRouter.Hostname != "" {
-		return string(cn.Spec.SubnetRouter.Hostname)
-	}
-	return cn.Name + "-" + "subnetrouter"
-}

cmd/k8s-operator/connector_test.go

@@ -7,6 +7,7 @@ package main
 
 import (
 	"context"
+	"fmt"
 	"testing"
 
 	"go.uber.org/zap"
@@ -21,6 +22,8 @@ import (
 )
 
 func TestConnector(t *testing.T) {
+	// Create a Connector that defines a Tailscale node that advertises
+	// 10.40.0.0/14 route and acts as an exit node.
 	cn := &tsapi.Connector{
 		ObjectMeta: metav1.ObjectMeta{
 			Name: "test",
@@ -34,6 +37,7 @@ func TestConnector(t *testing.T) {
 			SubnetRouter: &tsapi.SubnetRouter{
 				Routes: []tsapi.Route{"10.40.0.0/14"},
 			},
+			ExitNode: true,
 		},
 	}
 	fc := fake.NewClientBuilder().
@@ -48,7 +52,6 @@ func TestConnector(t *testing.T) {
 	}
 
 	cl := tstest.NewClock(tstest.ClockOpts{})
-	// Create a Connector with a subnet router definition
 	cr := &ConnectorReconciler{
 		Client: fc,
 		ssr: &tailscaleSTSReconciler{
@@ -63,26 +66,95 @@ func TestConnector(t *testing.T) {
 	}
 
 	expectReconciled(t, cr, "", "test")
-	fullName, shortName := findGenName(t, fc, "", "test", "subnetrouter")
+	fullName, shortName := findGenName(t, fc, "", "test", "connector")
 
-	expectEqual(t, fc, expectedSecret(fullName, "", "subnetrouter"))
-	expectEqual(t, fc, expectedConnectorSTS(shortName, fullName, "10.40.0.0/14"))
+	expectEqual(t, fc, expectedSecret(fullName, "", "connector"))
+	opts := connectorSTSOpts{
+		connectorName: "test",
+		stsName:       shortName,
+		secretName:    fullName,
+		routes:        "10.40.0.0/14",
+		isExitNode:    true,
+	}
+	expectEqual(t, fc, expectedConnectorSTS(opts))
 
-	// Add another CIDR
+	// Add another route to be advertised.
 	mustUpdate[tsapi.Connector](t, fc, "", "test", func(conn *tsapi.Connector) {
 		conn.Spec.SubnetRouter.Routes = []tsapi.Route{"10.40.0.0/14", "10.44.0.0/20"}
 	})
 	expectReconciled(t, cr, "", "test")
-	expectEqual(t, fc, expectedConnectorSTS(shortName, fullName, "10.40.0.0/14,10.44.0.0/20"))
+	opts.routes = "10.40.0.0/14,10.44.0.0/20"
+
+	expectEqual(t, fc, expectedConnectorSTS(opts))
 
-	// Remove a CIDR
+	// Remove a route.
 	mustUpdate[tsapi.Connector](t, fc, "", "test", func(conn *tsapi.Connector) {
 		conn.Spec.SubnetRouter.Routes = []tsapi.Route{"10.44.0.0/20"}
 	})
 	expectReconciled(t, cr, "", "test")
-	expectEqual(t, fc, expectedConnectorSTS(shortName, fullName, "10.44.0.0/20"))
+	opts.routes = "10.44.0.0/20"
+	expectEqual(t, fc, expectedConnectorSTS(opts))
+
+	// Remove the subnet router.
+	mustUpdate[tsapi.Connector](t, fc, "", "test", func(conn *tsapi.Connector) {
+		conn.Spec.SubnetRouter = nil
+	})
+	expectReconciled(t, cr, "", "test")
+	opts.routes = ""
+	expectEqual(t, fc, expectedConnectorSTS(opts))
+
+	// Re-add the subnet router.
+	mustUpdate[tsapi.Connector](t, fc, "", "test", func(conn *tsapi.Connector) {
+		conn.Spec.SubnetRouter = &tsapi.SubnetRouter{
+			Routes: []tsapi.Route{"10.44.0.0/20"},
+		}
+	})
+	expectReconciled(t, cr, "", "test")
+	opts.routes = "10.44.0.0/20"
+	expectEqual(t, fc, expectedConnectorSTS(opts))
+
+	// Delete the Connector.
+	if err = fc.Delete(context.Background(), cn); err != nil {
+		t.Fatalf("error deleting Connector: %v", err)
+	}
+
+	expectRequeue(t, cr, "", "test")
+	expectReconciled(t, cr, "", "test")
+
+	expectMissing[appsv1.StatefulSet](t, fc, "operator-ns", shortName)
+	expectMissing[corev1.Secret](t, fc, "operator-ns", fullName)
+
+	// Create a Connector that advertises a route and is not an exit node.
+	cn = &tsapi.Connector{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test",
+			UID:  types.UID("1234-UID"),
+		},
+		TypeMeta: metav1.TypeMeta{
+			Kind:       tsapi.ConnectorKind,
+			APIVersion: "tailscale.io/v1alpha1",
+		},
+		Spec: tsapi.ConnectorSpec{
+			SubnetRouter: &tsapi.SubnetRouter{
+				Routes: []tsapi.Route{"10.40.0.0/14"},
+			},
+		},
+	}
+	mustCreate(t, fc, cn)
+	expectReconciled(t, cr, "", "test")
+	fullName, shortName = findGenName(t, fc, "", "test", "connector")
+
+	expectEqual(t, fc, expectedSecret(fullName, "", "connector"))
+	opts = connectorSTSOpts{
+		connectorName: "test",
+		stsName:       shortName,
+		secretName:    fullName,
+		routes:        "10.40.0.0/14",
+		isExitNode:    false,
+	}
+	expectEqual(t, fc, expectedConnectorSTS(opts))
 
-	// Delete the Connector
+	// Delete the Connector.
 	if err = fc.Delete(context.Background(), cn); err != nil {
 		t.Fatalf("error deleting Connector: %v", err)
 	}
@@ -92,23 +164,45 @@ func TestConnector(t *testing.T) {
 
 	expectMissing[appsv1.StatefulSet](t, fc, "operator-ns", shortName)
 	expectMissing[corev1.Secret](t, fc, "operator-ns", fullName)
+}
 
+type connectorSTSOpts struct {
+	stsName       string
+	secretName    string
+	connectorName string
+	hostname      string
+	routes        string
+	isExitNode    bool
 }
 
-func expectedConnectorSTS(stsName, secretName, routes string) *appsv1.StatefulSet {
-	return &appsv1.StatefulSet{
+func expectedConnectorSTS(opts connectorSTSOpts) *appsv1.StatefulSet {
+	var hostname string
+	if opts.hostname != "" {
+		hostname = opts.hostname
+	} else {
+		hostname = opts.connectorName + "-connector"
+	}
+	containerEnv := []corev1.EnvVar{
+		{Name: "TS_USERSPACE", Value: "false"},
+		{Name: "TS_AUTH_ONCE", Value: "true"},
+		{Name: "TS_KUBE_SECRET", Value: opts.secretName},
+		{Name: "TS_HOSTNAME", Value: hostname},
+		{Name: "TS_EXTRA_ARGS", Value: fmt.Sprintf("--advertise-exit-node=%v", opts.isExitNode)},
+		{Name: "TS_ROUTES", Value: opts.routes},
+	}
+	sts := &appsv1.StatefulSet{
 		TypeMeta: metav1.TypeMeta{
 			Kind:       "StatefulSet",
 			APIVersion: "apps/v1",
 		},
 		ObjectMeta: metav1.ObjectMeta{
-			Name:      stsName,
+			Name:      opts.stsName,
 			Namespace: "operator-ns",
 			Labels: map[string]string{
 				"tailscale.com/managed":              "true",
 				"tailscale.com/parent-resource":      "test",
 				"tailscale.com/parent-resource-ns":   "",
-				"tailscale.com/parent-resource-type": "subnetrouter",
+				"tailscale.com/parent-resource-type": "connector",
 			},
 		},
 		Spec: appsv1.StatefulSetSpec{
@@ -116,13 +210,13 @@ func expectedConnectorSTS(stsName, secretName, routes string) *appsv1.StatefulSe
 			Selector: &metav1.LabelSelector{
 				MatchLabels: map[string]string{"app": "1234-UID"},
 			},
-			ServiceName: stsName,
+			ServiceName: opts.stsName,
 			Template: corev1.PodTemplateSpec{
 				ObjectMeta: metav1.ObjectMeta{
 					DeletionGracePeriodSeconds: ptr.To[int64](10),
 					Labels:                     map[string]string{"app": "1234-UID"},
 					Annotations: map[string]string{
-						"tailscale.com/operator-last-set-hostname": "test-subnetrouter",
+						"tailscale.com/operator-last-set-hostname": hostname,
 					},
 				},
 				Spec: corev1.PodSpec{
@@ -142,13 +236,7 @@ func expectedConnectorSTS(stsName, secretName, routes string) *appsv1.StatefulSe
 						{
 							Name:  "tailscale",
 							Image: "tailscale/tailscale",
-							Env: []corev1.EnvVar{
-								{Name: "TS_USERSPACE", Value: "false"},
-								{Name: "TS_AUTH_ONCE", Value: "true"},
-								{Name: "TS_KUBE_SECRET", Value: secretName},
-								{Name: "TS_HOSTNAME", Value: "test-subnetrouter"},
-								{Name: "TS_ROUTES", Value: routes},
-							},
+							Env:   containerEnv,
 							SecurityContext: &corev1.SecurityContext{
 								Capabilities: &corev1.Capabilities{
 									Add: []corev1.Capability{"NET_ADMIN"},
@@ -161,4 +249,5 @@ func expectedConnectorSTS(stsName, secretName, routes string) *appsv1.StatefulSe
 			},
 		},
 	}
+	return sts
 }

cmd/k8s-operator/sts.go

@@ -79,9 +79,16 @@ type tailscaleSTSConfig struct {
 	Hostname string
 	Tags     []string // if empty, use defaultTags
 
-	// Routes is a list of CIDRs to pass via --advertise-routes flag
-	// Should only be set if this is config for subnetRouter
-	Routes string
+	// Connector specifies a configuration of a Connector instance if that's
+	// what this StatefulSet should be created for.
+	Connector *connector
+}
+
+type connector struct {
+	// routes is a list of subnet routes that this Connector should expose.
+	routes string
+	// isExitNode defines whether this Connector should act as an exit node.
+	isExitNode bool
 }
 
 type tailscaleSTSReconciler struct {
@@ -419,19 +426,24 @@ func (a *tailscaleSTSReconciler) reconcileSTS(ctx context.Context, logger *zap.S
 				},
 			},
 		})
-	} else if len(sts.Routes) > 0 {
+	} else if sts.Connector != nil {
+		// We need to provide these env vars even if the values are empty to
+		// ensure that a transition from a Connector with a defined subnet
+		// router or exit node to one without succeeds.
+		container.Env = append(container.Env, corev1.EnvVar{
+			Name:  "TS_EXTRA_ARGS",
+			Value: fmt.Sprintf("--advertise-exit-node=%v", sts.Connector.isExitNode),
+		})
 		container.Env = append(container.Env, corev1.EnvVar{
 			Name:  "TS_ROUTES",
-			Value: sts.Routes,
+			Value: sts.Connector.routes,
 		})
-
 	}
 	if a.tsFirewallMode != "" {
 		container.Env = append(container.Env, corev1.EnvVar{
 			Name:  "TS_DEBUG_FIREWALL_MODE",
 			Value: a.tsFirewallMode,
-		},
-		)
+		})
 	}
 	ss.ObjectMeta = metav1.ObjectMeta{
 		Name:      headlessSvc.Name,