[node operator] helper: find control plane IPs using kubernetes API

Signed-off-by: Malte Poll <mp@edgeless.systems>

operators/constellation-node-operator/internal/controlplane/controlplane.go

@@ -0,0 +1,32 @@
+package controlplane
+
+import (
+	"context"
+	"fmt"
+
+	corev1 "k8s.io/api/core/v1"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	nodeutil "github.com/edgelesssys/constellation/operators/constellation-node-operator/internal/node"
+)
+
+// ListControlPlaneIPs retrieves a list of VPC IPs for the control plane nodes from kubernetes.
+func ListControlPlaneIPs(k8sClient client.Client) ([]string, error) {
+	var nodes corev1.NodeList
+	if err := k8sClient.List(context.TODO(), &nodes); err != nil {
+		return nil, fmt.Errorf("listing nodes: %w", err)
+	}
+	var ips []string
+	for _, node := range nodes.Items {
+		if !nodeutil.IsControlPlaneNode(&node) {
+			continue
+		}
+		for _, addr := range node.Status.Addresses {
+			if addr.Type == corev1.NodeInternalIP {
+				ips = append(ips, addr.Address)
+			}
+		}
+	}
+
+	return ips, nil
+}

operators/constellation-node-operator/internal/controlplane/controlplane_test.go

@@ -0,0 +1,77 @@
+package controlplane
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+func TestListControlPlaneIPs(t *testing.T) {
+	testCases := map[string]struct {
+		nodes   []corev1.Node
+		listErr error
+		wantIPs []string
+		wantErr bool
+	}{
+		"listing works": {
+			nodes: []corev1.Node{
+				{
+					ObjectMeta: metav1.ObjectMeta{
+						Labels: map[string]string{"node-role.kubernetes.io/control-plane": ""},
+					},
+					Status: corev1.NodeStatus{Addresses: []corev1.NodeAddress{{
+						Type:    corev1.NodeInternalIP,
+						Address: "192.0.2.1",
+					}}},
+				},
+				{
+					Status: corev1.NodeStatus{Addresses: []corev1.NodeAddress{{
+						Type:    corev1.NodeInternalIP,
+						Address: "192.0.2.2",
+					}}},
+				},
+			},
+			wantIPs: []string{"192.0.2.1"},
+		},
+		"listing fails": {
+			listErr: errors.New("listing failed"),
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			client := &stubClient{
+				nodes:   tc.nodes,
+				listErr: tc.listErr,
+			}
+			gotIPs, err := ListControlPlaneIPs(client)
+			if tc.wantErr {
+				assert.Error(err)
+				return
+			}
+			require.NoError(err)
+			assert.ElementsMatch(tc.wantIPs, gotIPs)
+		})
+	}
+}
+
+type stubClient struct {
+	nodes   []corev1.Node
+	listErr error
+	client.Client
+}
+
+func (c *stubClient) List(ctx context.Context, list client.ObjectList, opts ...client.ListOption) error {
+	list.(*corev1.NodeList).Items = c.nodes
+	return c.listErr
+}