fix(elasticloadbalancingv2): open, dual-stack-without-public-ipv4 ALB…

… allows IPv6 inbound traffic (#32203)

### Issue #

Closes #32197

### Reason for this change

Default generated security group ingress rules for open, dual-stack-without-public-ipv4 ALB does not allow IPv6 traffic.  Only a rule for IPv4 ingress traffic is added to the security group rules currently.

### Description of changes

Default generated security group ingress rules now have an additional rule that allows IPv6 ingress from anywhere.

### Description of how you validated changes

Added a unit test, and updated an existing integration test

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2/test/integ.alb.dualstack-without-public-ipv4.js.snapshot/aws-cdk-elbv2-integ-dualstack-without-public-ipv4.template.json

@@ -530,6 +530,13 @@
       "FromPort": 80,
       "IpProtocol": "tcp",
       "ToPort": 80
+     },
+     {
+      "CidrIpv6": "::/0",
+      "Description": "Allow from anyone on port 80",
+      "FromPort": 80,
+      "IpProtocol": "tcp",
+      "ToPort": 80
      }
     ],
     "VpcId": {

packages/aws-cdk-lib/aws-elasticloadbalancingv2/README.md

@@ -298,13 +298,14 @@ const lb = new elbv2.ApplicationLoadBalancer(this, 'LB', {
 });
 ```
 
-By setting `DUAL_STACK_WITHOUT_PUBLIC_IPV4`, you can provision load balancers without public IPv4s
+By setting `DUAL_STACK_WITHOUT_PUBLIC_IPV4`, you can provision load balancers without public IPv4s:
 
 ```ts
 declare const vpc: ec2.Vpc;
 
 const lb = new elbv2.ApplicationLoadBalancer(this, 'LB', {
   vpc,
+  internetFacing: true,
   ipAddressType: elbv2.IpAddressType.DUAL_STACK_WITHOUT_PUBLIC_IPV4,
 });
 ```

packages/aws-cdk-lib/aws-elasticloadbalancingv2/lib/alb/application-listener.ts

@@ -303,7 +303,8 @@ export class ApplicationListener extends BaseListener implements IApplicationLis
 
     if (props.open !== false) {
       this.connections.allowDefaultPortFrom(ec2.Peer.anyIpv4(), `Allow from anyone on port ${port}`);
-      if (this.loadBalancer.ipAddressType === IpAddressType.DUAL_STACK) {
+      if (this.loadBalancer.ipAddressType === IpAddressType.DUAL_STACK ||
+        this.loadBalancer.ipAddressType === IpAddressType.DUAL_STACK_WITHOUT_PUBLIC_IPV4) {
         this.connections.allowDefaultPortFrom(ec2.Peer.anyIpv6(), `Allow from anyone on port ${port}`);
       }
     }

packages/aws-cdk-lib/aws-elasticloadbalancingv2/test/alb/listener.test.ts

@@ -107,6 +107,43 @@ describe('tests', () => {
     });
   });
 
+  test('Listener default to open - IPv6 (dual stack without public IPV4)', () => {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'Stack');
+    const loadBalancer = new elbv2.ApplicationLoadBalancer(stack, 'LB', {
+      vpc,
+      internetFacing: true,
+      ipAddressType: elbv2.IpAddressType.DUAL_STACK_WITHOUT_PUBLIC_IPV4,
+    });
+
+    // WHEN
+    loadBalancer.addListener('MyListener', {
+      port: 80,
+      defaultTargetGroups: [new elbv2.ApplicationTargetGroup(stack, 'Group', { vpc, port: 80 })],
+    });
+
+    // THEN
+    Template.fromStack(stack).hasResourceProperties('AWS::EC2::SecurityGroup', {
+      SecurityGroupIngress: [
+        {
+          Description: 'Allow from anyone on port 80',
+          CidrIp: '0.0.0.0/0',
+          FromPort: 80,
+          IpProtocol: 'tcp',
+          ToPort: 80,
+        },
+        {
+          Description: 'Allow from anyone on port 80',
+          CidrIpv6: '::/0',
+          FromPort: 80,
+          IpProtocol: 'tcp',
+          ToPort: 80,
+        },
+      ],
+    });
+  });
+
   test('HTTPS listener requires certificate', () => {
     // GIVEN
     const stack = new cdk.Stack();