Bug 1824426: set primaryClusterNetwork tag for the primary network

In the case of multiple addednetwrorks this tag should allow
cluster-api-provider-openstack to define which ip address to set
as the primary one for machines.
Now CAPO can't do this, because Neutron returns the list of networks
in alphabetical order.

data/data/openstack/topology/private-network.tf

@@ -14,7 +14,7 @@ resource "openstack_networking_network_v2" "openshift-private" {
   count          = var.machines_subnet_id == "" ? 1 : 0
   name           = "${var.cluster_id}-openshift"
   admin_state_up = "true"
-  tags           = ["openshiftClusterID=${var.cluster_id}"]
+  tags           = ["openshiftClusterID=${var.cluster_id}", "primaryClusterNetwork"]
 }
 
 resource "openstack_networking_subnet_v2" "nodes" {

pkg/tfvars/openstack/openstack.go

@@ -11,6 +11,7 @@ import (
 	"github.com/gophercloud/gophercloud/openstack"
 	"github.com/gophercloud/gophercloud/openstack/identity/v3/tokens"
 	"github.com/gophercloud/gophercloud/openstack/imageservice/v2/images"
+	"github.com/gophercloud/gophercloud/openstack/networking/v2/extensions/attributestags"
 	"github.com/gophercloud/gophercloud/openstack/networking/v2/subnets"
 	"github.com/gophercloud/utils/openstack/clientconfig"
 	"github.com/openshift/installer/pkg/rhcos"
@@ -21,6 +22,10 @@ import (
 	"sigs.k8s.io/cluster-api-provider-openstack/pkg/apis/openstackproviderconfig/v1alpha1"
 )
 
+const (
+	primaryClusterNetworkTag = "primaryClusterNetwork"
+)
+
 type config struct {
 	BaseImageName              string   `json:"openstack_base_image_name,omitempty"`
 	ExternalNetwork            string   `json:"openstack_external_network,omitempty"`
@@ -152,6 +157,15 @@ func TFVars(masterConfig *v1alpha1.OpenstackProviderSpec, cloud string, external
 		if err != nil {
 			return nil, err
 		}
+
+		// Make sure that the network has the primary cluster network tag.
+		// In the case of multiple networks this tag is required for
+		// cluster-api-provider-openstack to define which ip address to set as
+		// the primary one.
+		err = setNetworkTag(cloud, cfg.MachinesNetwork, primaryClusterNetworkTag)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return json.MarshalIndent(cfg, "", "  ")
@@ -265,3 +279,22 @@ func getNetworkFromSubnet(cloud string, subnetID string) (string, error) {
 
 	return subnet.NetworkID, nil
 }
+
+// setNetworkTag sets a tag for the network
+func setNetworkTag(cloud string, networkID string, tag string) error {
+	opts := &clientconfig.ClientOpts{
+		Cloud: cloud,
+	}
+
+	networkClient, err := clientconfig.NewServiceClient("network", opts)
+	if err != nil {
+		return err
+	}
+
+	err = attributestags.Add(networkClient, "networks", networkID, tag).ExtractErr()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}