[12] RFR 8199931: java/net/MulticastSocket/UnreferencedMulticastSockets.java fails with "incorrect data received"

[Chris Yin]

Loop net-dev since the test is under java/net, thanks

> On 20 Sep 2018, at 5:30 PM, Chris Yin <xu.y.yin at oracle.com> wrote:
> 
> Please review below minor change for 8199931, thanks
> 
> A little explanation about the change here, since the failure samples are too less (seems too hard to repro), so below scenario which caused the failure is a guess. MultcastSocket constructor set reuse address true by default, when call “new MulticastSocket(0)” to create client socket that maybe in a little possibility it used same address with server, that will explain why the failure looks like client received data package from itself. Follow the guessing, I modified test code to explicit create client socket use same port with server, then got same failure error as reported bug on OEL7. Though I cannot make sure the guess is 100% match with the original failure, but at least we could try to prevent such possible scenario.
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8199931
> 
> changes:
> 
> diff -r 43668e3cae4d test/jdk/java/net/MulticastSocket/UnreferencedMulticastSockets.java
> --- a/test/jdk/java/net/MulticastSocket/UnreferencedMulticastSockets.java	Thu Sep 20 08:59:03 2018 +0200
> +++ b/test/jdk/java/net/MulticastSocket/UnreferencedMulticastSockets.java	Thu Sep 20 16:37:36 2018 +0800
> @@ -40,6 +40,7 @@
> import java.net.DatagramSocket;
> import java.net.DatagramSocketImpl;
> import java.net.InetAddress;
> +import java.net.InetSocketAddress;
> import java.net.MulticastSocket;
> import java.net.UnknownHostException;
> import java.nio.file.Files;
> @@ -119,7 +120,10 @@
>         Thread thr = new Thread(svr);
>         thr.start();
> 
> -        MulticastSocket client = new MulticastSocket(0);
> +        MulticastSocket client = new MulticastSocket(null);
> +        // prevent MulticastSocket reuse previous address, see 8199931
> +        client.setReuseAddress(false);
> +        client.bind(new InetSocketAddress(0));
>         client.connect(svr.getHost(), svr.getPort());
>         pendingSockets.add(new NamedWeak(client, pendingQueue, "clientMulticastSocket"));
>         extractRefs(client, "clientMulticastSocket”);
> 
> Regards,
> Chris