RFR[8233307]: MulticastSocket getOption(IP_MULTICAST_IF) returns interface when not set

[Chris Hegarty]

Patrick,

> On 27 Nov 2019, at 14:54, Patrick Concannon <patrick.concannon at oracle.com> wrote:
> 
> Hi,
> 
> 
> Could someone please review my fix and CSR for issue JDK-8233307 'MulticastSocket getOption(IP_MULTICAST_IF) returns interface when not set'?
> 
> The IP_MULTICAST_IF socket option is specified to have an initial value of null to mean that the interface has not been set. However, if MulticastSocket.getOption(IP_MULTICAST_IF) is called when the interface is not set, it returns a dummy NetworkInterface.
> 
> This fix changes the getOption() method to return 'null' as specified instead of a dummy networkInterface.
> 
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8233307
> 
> csr: https://bugs.openjdk.java.net/browse/JDK-8234811
> webrev: http://cr.openjdk.java.net/~pconcannon/8233307/webrevs/webrev.01/

This looks good. Some small comments on the test:

1) The test should use the (test library) NetworkConfiguration 
   multicastInterfaces method, instead of retrieving all the system
   interfaces. The former will filter out potentially problematic system
   interfaces that could affect the stability of the test.

2) Enumeration :-( Suggest [ subject to the above comment ]
   a) NetworkInterface.networkInterfaces().collect(toList()) , or
   b) Collections.list(NetworkInterface.getNetworkInterfaces())

3) While the test does run in othervm mode, it should probably be a good
   citizen and close the sockets that it opens.

-Chris