GCP userProvisioned DNS is featuregated

Add validation to make sure that feature gate is enabled when the
feature is enabled.

Author: sadasu

pkg/types/gcp/validation/featuregates.go

@@ -6,6 +6,7 @@ import (
 	configv1 "github.com/openshift/api/config/v1"
 	"github.com/openshift/installer/pkg/types"
 	"github.com/openshift/installer/pkg/types/featuregates"
+	"github.com/openshift/installer/pkg/types/gcp"
 )
 
 // GatedFeatures determines all of the install config fields that should
@@ -23,5 +24,10 @@ func GatedFeatures(c *types.InstallConfig) []featuregates.GatedInstallConfigFeat
 			Condition:       len(g.UserTags) > 0,
 			Field:           field.NewPath("platform", "gcp", "userTags"),
 		},
+		{
+			FeatureGateName: configv1.FeatureGateGCPClusterHostedDNS,
+			Condition:       g.UserProvisionedDNS == gcp.UserProvisionedDNSEnabled,
+			Field:           field.NewPath("platform", "gcp", "userProvisionedDNS"),
+		},
 	}
 }

pkg/types/validation/featuregate_test.go

@@ -47,6 +47,16 @@ func TestFeatureGates(t *testing.T) {
 				return c
 			}(),
 		},
+		{
+			name: "GCP UserProvisionedDNS is not allowed without Feature Gates",
+			installConfig: func() *types.InstallConfig {
+				c := validInstallConfig()
+				c.GCP = validGCPPlatform()
+				c.GCP.UserProvisionedDNS = gcp.UserProvisionedDNSEnabled
+				return c
+			}(),
+			expected: `^platform.gcp.userProvisionedDNS: Forbidden: this field is protected by the GCPClusterHostedDNS feature gate which must be enabled through either the TechPreviewNoUpgrade or CustomNoUpgrade feature set$`,
+		},
 		{
 			name: "GCP UserLabels is not allowed without Feature Gates",
 			installConfig: func() *types.InstallConfig {