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

[Chris Hegarty]

Thank you for looking at this issue Chris Y.

I don’t disagree with the changes, but if you want to confirm your
suspicion, that the same port is being reused, then printing out
the client’s bound port would do that ( since the servers port is
already printed in the logs ). 

If such a change was integrated, then the next observed failure
would confirm or disconfirm your suspicion.

-Chris H.

> On 20 Sep 2018, at 11:50, Chris Yin <xu.y.yin at oracle.com> wrote:
> 
> 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
>