OCPBUGS-66244: default Azure to marketplace image

In 4.21, the installer stopped creating a cluster-specific image
gallery and moved to marketplace images. This PR updates the default
for a minimal provider spec to use a hard-coded marketplace image,
similar to the approach used for GCP.

Author: patrickdillon

pkg/webhooks/machine_webhook.go

@@ -65,24 +65,27 @@ var (
 	defaultAzureNetworkResourceGroup = func(clusterID string) string {
 		return fmt.Sprintf("%s-rg", clusterID)
 	}
-	defaultAzureImageResourceID = func(clusterID string) string {
-		// image gallery names cannot have dashes
-		galleryName := strings.Replace(clusterID, "-", "_", -1)
-		imageName := clusterID
+	defaultAzureImage = func() machinev1beta1.Image {
 		if arch == ARM64 {
-			// append gen2 to the image name for ARM64.
-			// Although the installer creates a gen2 image for AMD64, we cannot guarantee that clusters created
-			// before that change will have a -gen2 image.
-			imageName = fmt.Sprintf("%s-gen2", clusterID)
+			return urnToImage(defaultAzureARMImageURN)
 		}
-		return fmt.Sprintf("/resourceGroups/%s/providers/Microsoft.Compute/galleries/gallery_%s/images/%s/versions/%s", clusterID+"-rg", galleryName, imageName, azureRHCOSVersion)
+		return urnToImage(defaultAzureX86ImageURN)
 	}
 	defaultAzureManagedIdentiy = func(clusterID string) string {
 		return fmt.Sprintf("%s-identity", clusterID)
 	}
 	defaultAzureResourceGroup = func(clusterID string) string {
 		return fmt.Sprintf("%s-rg", clusterID)
 	}
+	urnToImage = func(urn string) machinev1beta1.Image {
+		attributes := strings.Split(urn, ":")
+		return machinev1beta1.Image{
+			Publisher: attributes[0],
+			Offer:     attributes[1],
+			SKU:       attributes[2],
+			Version:   attributes[3],
+		}
+	}
 
 	// GCP Defaults
 	defaultGCPNetwork = func(clusterID string) string {
@@ -164,6 +167,8 @@ const (
 	defaultAzureCredentialsSecret = "azure-cloud-credentials"
 	defaultAzureOSDiskOSType      = "Linux"
 	defaultAzureOSDiskStorageType = "Premium_LRS"
+	defaultAzureX86ImageURN       = "azureopenshift:aro4:aro_420:9.6.20251015" // hyperV Gen1
+	defaultAzureARMImageURN       = "azureopenshift:aro4:420-arm:9.6.20251015"
 
 	// Azure OSDisk constants
 	azureMaxDiskSizeGB                 = 32768
@@ -1012,7 +1017,7 @@ func defaultAzure(m *machinev1beta1.Machine, config *admissionConfig) (bool, []s
 	}
 
 	if providerSpec.Image == (machinev1beta1.Image{}) {
-		providerSpec.Image.ResourceID = defaultAzureImageResourceID(config.clusterID)
+		providerSpec.Image = defaultAzureImage()
 	}
 
 	if providerSpec.UserDataSecret == nil {

pkg/webhooks/machine_webhook_test.go

@@ -1712,11 +1712,9 @@ func TestMachineUpdate(t *testing.T) {
 		Vnet:                 defaultAzureVnet(azureClusterID),
 		Subnet:               defaultAzureSubnet(azureClusterID),
 		NetworkResourceGroup: defaultAzureNetworkResourceGroup(azureClusterID),
-		Image: machinev1beta1.Image{
-			ResourceID: defaultAzureImageResourceID(azureClusterID),
-		},
-		ManagedIdentity: defaultAzureManagedIdentiy(azureClusterID),
-		ResourceGroup:   defaultAzureResourceGroup(azureClusterID),
+		Image:                defaultAzureImage(),
+		ManagedIdentity:      defaultAzureManagedIdentiy(azureClusterID),
+		ResourceGroup:        defaultAzureResourceGroup(azureClusterID),
 		UserDataSecret: &corev1.SecretReference{
 			Name:      defaultUserDataSecret,
 			Namespace: defaultSecretNamespace,
@@ -3767,9 +3765,7 @@ func TestDefaultAzureProviderSpec(t *testing.T) {
 				VMSize: defaultInstanceType,
 				Vnet:   defaultAzureVnet(clusterID),
 				Subnet: defaultAzureSubnet(clusterID),
-				Image: machinev1beta1.Image{
-					ResourceID: defaultAzureImageResourceID(clusterID),
-				},
+				Image:  defaultAzureImage(),
 				UserDataSecret: &corev1.SecretReference{
 					Name: defaultUserDataSecret,
 				},

pkg/webhooks/machineset_webhook_test.go

@@ -602,11 +602,9 @@ func TestMachineSetUpdate(t *testing.T) {
 		Vnet:                 defaultAzureVnet(azureClusterID),
 		Subnet:               defaultAzureSubnet(azureClusterID),
 		NetworkResourceGroup: defaultAzureNetworkResourceGroup(azureClusterID),
-		Image: machinev1beta1.Image{
-			ResourceID: defaultAzureImageResourceID(azureClusterID),
-		},
-		ManagedIdentity: defaultAzureManagedIdentiy(azureClusterID),
-		ResourceGroup:   defaultAzureResourceGroup(azureClusterID),
+		Image:                defaultAzureImage(),
+		ManagedIdentity:      defaultAzureManagedIdentiy(azureClusterID),
+		ResourceGroup:        defaultAzureResourceGroup(azureClusterID),
 		UserDataSecret: &corev1.SecretReference{
 			Name:      defaultUserDataSecret,
 			Namespace: defaultSecretNamespace,