OpenStack builder: allow floating IP network name

Add support for the external network reference by it's name apart from
ID.
Include external network id in a log message of
the openstack/step_allocate_ip.

builder/openstack/networks.go

@@ -3,6 +3,7 @@ package openstack
 import (
 	"fmt"
 
+	"github.com/google/uuid"
 	"github.com/gophercloud/gophercloud"
 	"github.com/gophercloud/gophercloud/openstack/compute/v2/extensions/attachinterfaces"
 	"github.com/gophercloud/gophercloud/openstack/networking/v2/extensions/external"
@@ -112,3 +113,39 @@ func GetInstancePortID(client *gophercloud.ServiceClient, id string) (string, er
 
 	return interfaces[0].PortID, nil
 }
+
+// CheckExternalNetworkRef checks provided network reference and returns a valid
+// Networking service ID.
+func CheckExternalNetworkRef(client *gophercloud.ServiceClient, networkRef string) (string, error) {
+	if _, err := uuid.Parse(networkRef); err != nil {
+		return GetExternalNetworkIDByName(client, networkRef)
+	}
+
+	return networkRef, nil
+}
+
+// GetExternalNetworkIDByName searches for the external network ID by the provided name.
+func GetExternalNetworkIDByName(client *gophercloud.ServiceClient, networkName string) (string, error) {
+	var externalNetworks []ExternalNetwork
+
+	allPages, err := networks.List(client, networks.ListOpts{
+		Name: networkName,
+	}).AllPages()
+	if err != nil {
+		return "", err
+	}
+
+	if err := networks.ExtractNetworksInto(allPages, &externalNetworks); err != nil {
+		return "", err
+	}
+
+	if len(externalNetworks) == 0 {
+		return "", fmt.Errorf("can't find external network %s", networkName)
+	}
+	// Check and return the first external network.
+	if !externalNetworks[0].External {
+		return "", fmt.Errorf("network %s is not external", networkName)
+	}
+
+	return externalNetworks[0].ID, nil
+}

builder/openstack/step_allocate_ip.go

@@ -75,10 +75,19 @@ func (s *StepAllocateIp) Run(_ context.Context, state multistep.StateBag) multis
 
 	// Create a new floating IP if it wasn't obtained in the previous step.
 	if instanceIP.ID == "" {
-		// Search for the external network that can be used for the floating IPs if
-		// user hasn't provided any.
-		floatingNetwork := s.FloatingIPNetwork
-		if floatingNetwork == "" {
+		var floatingNetwork string
+
+		if s.FloatingIPNetwork != "" {
+			// Validate provided external network reference and get an ID.
+			floatingNetwork, err = CheckExternalNetworkRef(networkClient, s.FloatingIPNetwork)
+			if err != nil {
+				err := fmt.Errorf("Error using the provided floating_ip_network: %s", err)
+				state.Put("error", err)
+				ui.Error(err.Error())
+				return multistep.ActionHalt
+			}
+		} else {
+			// Search for the external network that can be used for the floating IPs.
 			ui.Say(fmt.Sprintf("Searching for the external network..."))
 			externalNetwork, err := FindExternalNetwork(networkClient)
 			if err != nil {
@@ -87,11 +96,10 @@ func (s *StepAllocateIp) Run(_ context.Context, state multistep.StateBag) multis
 				ui.Error(err.Error())
 				return multistep.ActionHalt
 			}
-
 			floatingNetwork = externalNetwork.ID
 		}
 
-		ui.Say(fmt.Sprintf("Creating floating IP..."))
+		ui.Say(fmt.Sprintf("Creating floating IP using network %s ...", floatingNetwork))
 		newIP, err := floatingips.Create(networkClient, floatingips.CreateOpts{
 			FloatingNetworkID: floatingNetwork,
 		}).Extract()