IPv6 only environment OL9 x64 IPV6 only configured environment

test result: Error. Agent error: java.lang.Exception: Agent 23 timed out with a timeout of 1200 seconds; check console log for any additional details

This is run agentvm mode hence test diagnostic output is missing. Test is stuck in multicast receive

"AgentVMThread" #38 [139654] prio=5 os_prio=0 cpu=22.00ms elapsed=1212.34s allocated=271K defined_classes=25 tid=0x00007f8a1439b9e0 nid=139654 runnable [0x00007f89fc29c000]
   java.lang.Thread.State: RUNNABLE
at sun.nio.ch.DatagramChannelImpl.receive0(java.base@21-ea/Native Method)
at sun.nio.ch.DatagramChannelImpl.receiveIntoNativeBuffer(java.base@21-ea/DatagramChannelImpl.java:789)
at sun.nio.ch.DatagramChannelImpl.receive(java.base@21-ea/DatagramChannelImpl.java:773)
at sun.nio.ch.DatagramChannelImpl.receive(java.base@21-ea/DatagramChannelImpl.java:577)
at Loopback.test(Loopback.java:129)
at Loopback.main(Loopback.java:83)
at java.lang.invoke.LambdaForm$DMH/0x00000001000c0000.invokeStatic(java.base@21-ea/LambdaForm$DMH)
at java.lang.invoke.LambdaForm$MH/0x0000000100141800.invoke(java.base@21-ea/LambdaForm$MH)
at java.lang.invoke.Invokers$Holder.invokeExact_MT(java.base@21-ea/Invokers$Holder)
at jdk.internal.reflect.DirectMethodHandleAccessor.invokeImpl(java.base@21-ea/DirectMethodHandleAccessor.java:154)
at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(java.base@21-ea/DirectMethodHandleAccessor.java:103)
at java.lang.reflect.Method.invoke(java.base@21-ea/Method.java:578)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:333)
at java.lang.Thread.runWith(java.base@21-ea/Thread.java:1605)
at java.lang.Thread.run(java.base@21-ea/Thread.java:1592)

loopback receive not effective

            // -- IP_MULTICAST_LOOP enabled --

            assertTrue(dc.getOption(IP_MULTICAST_LOOP), "IP_MULTICAST_LOOP not enabled");
            System.out.println("IP_MULTICAST_LOOP enabled");

            // send datagram to multicast group
            System.out.format("send %s -> %s%n", dc.getLocalAddress(), target);
            ByteBuffer src = ByteBuffer.wrap("hello".getBytes("UTF-8"));
            dc.send(src, target);

            // receive datagram sent to multicast group
            ByteBuffer dst = ByteBuffer.allocate(100);
            int senderPort;
            do {
                dst.clear();
                SocketAddress sender = dc.receive(dst);
                System.out.format("received %s from %s%n", dst, sender);
                senderPort = ((InetSocketAddress) sender).getPort();
            } while (senderPort != localPort);
            dst.flip();
            assertTrue(dst.remaining() == src.capacity(), "Unexpected message size");