[occm] cherrypick: LB - Fix floating ip subnet detection and ipv6 handling (kubernetes#2022)

* [occm] Skip External network with IPv6 for FIPs creation (kubernetes#1992)

OpenStack does not support creation of floating IPs
with IPv6. However, it's still possible to exist external
networks with IPv6 Subnets, which could break the creation
of Floating IPs for a load-balancer if CCM uses it.
This commit avoids this issue by making sure only external
networks with IPv4 Subnets are used when creating a Floating IP.

* Improve retrival of external Network (kubernetes#2014)

When attempting to fetch an external Network with IPv4 Subnets to
create a Floating IP, it's possible that no Subnets from that Network
are shared with the tenant, consequently it would not be possible to
filter them by IPVersion and no Network would be used. This commit
improve the detection of external Network by only allowing usage of
Networks that is possible to detect at least one IPV4 Subnet or that
is not possible to detect any info about the Subnets.

Co-authored-by: Maysa De Macedo Souza <maysa.souza@ccc.ufcg.edu.br>
Co-authored-by: Maysa De Macedo Souza <maysa.macedo95@gmail.com>

Author: chrigl

pkg/util/openstack/network.go

@@ -23,6 +23,7 @@ import (
 	"github.com/gophercloud/gophercloud/openstack/networking/v2/extensions/layer3/floatingips"
 	"github.com/gophercloud/gophercloud/openstack/networking/v2/networks"
 	neutronports "github.com/gophercloud/gophercloud/openstack/networking/v2/ports"
+	"github.com/gophercloud/gophercloud/openstack/networking/v2/subnets"
 	"github.com/gophercloud/gophercloud/pagination"
 
 	"k8s.io/cloud-provider-openstack/pkg/metrics"
@@ -85,48 +86,57 @@ func GetFloatingIPByPortID(client *gophercloud.ServiceClient, portID string) (*f
 
 // GetFloatingNetworkID returns a floating network ID.
 func GetFloatingNetworkID(client *gophercloud.ServiceClient) (string, error) {
-	var floatingNetworkIds []string
-
 	type NetworkWithExternalExt struct {
 		networks.Network
 		external.NetworkExternalExt
 	}
+	var allNetworks []NetworkWithExternalExt
 
 	mc := metrics.NewMetricContext("network", "list")
-	err := networks.List(client, networks.ListOpts{}).EachPage(func(page pagination.Page) (bool, error) {
-		var externalNetwork []NetworkWithExternalExt
-		err := networks.ExtractNetworksInto(page, &externalNetwork)
-		if err != nil {
-			return false, err
-		}
-
-		for _, externalNet := range externalNetwork {
-			if externalNet.External {
-				floatingNetworkIds = append(floatingNetworkIds, externalNet.ID)
-			}
-		}
-
-		if len(floatingNetworkIds) > 1 {
-			return false, cpoerrors.ErrMultipleResults
-		}
-		return true, nil
-	})
+	page, err := networks.List(client, networks.ListOpts{}).AllPages()
 	if err != nil {
-		if cpoerrors.IsNotFound(err) {
-			return "", mc.ObserveRequest(cpoerrors.ErrNotFound)
-		}
+		return "", mc.ObserveRequest(err)
+	}
 
-		if err == cpoerrors.ErrMultipleResults {
-			return floatingNetworkIds[0], mc.ObserveRequest(nil)
-		}
+	err = networks.ExtractNetworksInto(page, &allNetworks)
+	if err != nil {
 		return "", mc.ObserveRequest(err)
 	}
 
-	if len(floatingNetworkIds) == 0 {
-		return "", mc.ObserveRequest(cpoerrors.ErrNotFound)
+	for _, network := range allNetworks {
+		if network.External && len(network.Subnets) > 0 {
+			mc := metrics.NewMetricContext("subnet", "list")
+			page, err := subnets.List(client, subnets.ListOpts{NetworkID: network.ID}).AllPages()
+			if err != nil {
+				return "", mc.ObserveRequest(err)
+			}
+			subnetList, err := subnets.ExtractSubnets(page)
+			if err != nil {
+				return "", mc.ObserveRequest(err)
+			}
+			for _, networkSubnet := range network.Subnets {
+				subnet := getSubnet(networkSubnet, subnetList)
+				if subnet != nil {
+					if subnet.IPVersion == 4 {
+						return network.ID, nil
+					}
+				} else {
+					return network.ID, nil
+				}
+			}
+		}
 	}
+	return "", mc.ObserveRequest(cpoerrors.ErrNotFound)
+}
 
-	return floatingNetworkIds[0], mc.ObserveRequest(nil)
+// getSubnet checks if a Subnet is present in the list of Subnets the tenant has access to and returns it
+func getSubnet(networkSubnet string, subnetList []subnets.Subnet) *subnets.Subnet {
+	for _, subnet := range subnetList {
+		if subnet.ID == networkSubnet {
+			return &subnet
+		}
+	}
+	return nil
 }
 
 // GetPorts gets all the filtered ports.