PowerVS: Use random subnet

We are seeing:
dhcp server failed to create private network: unable to retrieve active status for new PER connection information after create private network
This error might be alleviated by not conflicting the CIDR when we create the DHCP network.  One way to mitigate this is to use a random subnet address.

Author: hamzy

pkg/asset/manifests/powervs/cluster.go

@@ -2,7 +2,9 @@ package powervs
 
 import (
 	"context"
+	"crypto/rand"
 	"fmt"
+	"math/big"
 
 	"github.com/sirupsen/logrus"
 	corev1 "k8s.io/api/core/v1"
@@ -22,6 +24,7 @@ func GenerateClusterAssets(installConfig *installconfig.InstallConfig, clusterID
 	var (
 		manifests          []*asset.RuntimeFile
 		network            string
+		dhcpSubnet         = "192.168.0.0/24"
 		service            capibm.IBMPowerVSResourceReference
 		vpcName            string
 		vpcRegion          string
@@ -53,6 +56,12 @@ func GenerateClusterAssets(installConfig *installconfig.InstallConfig, clusterID
 
 	network = fmt.Sprintf("%s-network", clusterID.InfraID)
 
+	n, err := rand.Int(rand.Reader, big.NewInt(253))
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate random subnet: %w", err)
+	}
+	dhcpSubnet = fmt.Sprintf("192.168.%d.0/24", n.Int64())
+
 	if installConfig.Config.PowerVS.ServiceInstanceGUID == "" {
 		serviceName := fmt.Sprintf("%s-power-iaas", clusterID.InfraID)
 
@@ -105,6 +114,9 @@ func GenerateClusterAssets(installConfig *installconfig.InstallConfig, clusterID
 			Network: capibm.IBMPowerVSResourceReference{
 				Name: &network,
 			},
+			DHCPServer: &capibm.DHCPServer{
+				Cidr: &dhcpSubnet,
+			},
 			ServiceInstance: &service,
 			Zone:            &installConfig.Config.Platform.PowerVS.Zone,
 			ResourceGroup: &capibm.IBMPowerVSResourceReference{
@@ -163,9 +175,7 @@ func GenerateClusterAssets(installConfig *installconfig.InstallConfig, clusterID
 			return nil, fmt.Errorf("unable to find a DNS server for specified VPC: %s %w", installConfig.Config.PowerVS.VPCName, err)
 		}
 
-		powerVSCluster.Spec.DHCPServer = &capibm.DHCPServer{
-			DNSServer: &dnsServerIP,
-		}
+		powerVSCluster.Spec.DHCPServer.DNSServer = &dnsServerIP
 	}
 
 	// If a VPC was specified, pass all subnets in it to cluster API