CORS-4209: ensure NodeIPFamilies field is kept as-is after transforming

pkg/cloud/aws/aws_config_transformer.go

@@ -54,7 +54,8 @@ func readAWSConfig(source string) (*awsconfig.CloudConfig, error) {
 }
 
 func marshalAWSConfig(cfg *awsconfig.CloudConfig) (string, error) {
-	file := ini.Empty()
+	// Configure iniv1 to allow shadow fields to enable multiple entries of NodeIPFamilies.
+	file := ini.Empty(ini.LoadOptions{AllowShadows: true})
 	if err := file.Section("Global").ReflectFrom(&cfg.Global); err != nil {
 		return "", fmt.Errorf("failed to reflect global config: %w", err)
 	}
@@ -65,6 +66,25 @@ func marshalAWSConfig(cfg *awsconfig.CloudConfig) (string, error) {
 		}
 	}
 
+	// In dual-stack environment, the CCM expects NodeIPFamilies to be in the format:
+	//
+	// NodeIPFamilies=ipv4
+	// NodeIPFamilies=ipv6
+	//
+	// However, iniv1 is serializing go slices as comma-separated list, for example:
+	//
+	// NodeIPFamilies=ipv4,ipv6
+	//
+	// Below logic ensures the original NodeIPFamilies field is kept as-is after transforming.
+	nodeIPKey := file.Section("Global").Key("NodeIPFamilies")
+	for i, ipFamily := range cfg.Global.NodeIPFamilies {
+		if i == 0 {
+			nodeIPKey.SetValue(ipFamily)
+		} else if err := nodeIPKey.AddShadow(ipFamily); err != nil {
+			return "", fmt.Errorf("failed to set NodeIPFamilies: %w", err)
+		}
+	}
+
 	for _, section := range file.Sections() {
 		for key, value := range section.KeysHash() {
 			// Ignore anything that is the zero value for its type.

pkg/cloud/aws/aws_config_transformer_test.go

@@ -83,6 +83,20 @@ URL           = https://s3.foo.bar
 SigningRegion = signing_region
 `, // Ordered based on the order of fields in the AWS CloudConfig struct.
 		},
+		{
+			name: "with NodeIPFamilies",
+			source: `[Global]
+NodeIPFamilies = ipv4
+NodeIPFamilies = ipv6
+			`,
+			expected: `[Global]
+DisableSecurityGroupIngress                     = false
+NodeIPFamilies                                  = ipv4
+NodeIPFamilies                                  = ipv6
+ClusterServiceLoadBalancerHealthProbeMode       = Shared
+ClusterServiceSharedLoadBalancerHealthProbePort = 0
+`,
+		},
 	}
 
 	for _, tc := range testCases {