RFR: 8308807: [AIX] MulticastSocket and jdp test fails due to joinGroup

[Pushkar N Kulkarni]

On Tue, 13 Jun 2023 07:01:28 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>>> Well, in that area we always had deviations on AIX, so definitely this rings a bell. However, since AIX was not the most important platform for us and that particular IPv6/IPv4 multicast feature didn't seem to be mission critical and wouldn't fail TCK tests, we rather resorted to excluding some tests internally, I believe. But it would be good to really resolve this compatibility/spec/documentation issue, if possible.
>> 
>> Thanks. So yes, if some/all of the tests for multicasting were excluded then it helps explain why it didn't come up. The spec doesn't require that a DatgaramSocket or DatagramChannel to an IPv6 socket be capable of joining an IPv4 multicast group. So the tests in several areas might need updates as I don't think we've had a platform to date where it wasn't possible.
>
>> @AlanBateman , is it possible if there is a central place where the change could me made for fixing all of the multicast test cases?
> 
> Your starting point is probably to exclude all of the tests that are failing. This will be tests for DatagramSocket/MulticastSocket, DatagramChannel and the tests for the JMX agent that use the discovery protocol. Once they are excluded then you can start working through the issues.
> 
> For the JMX agent, then I would expect that if if the system property com.sun.management.jdp.address is configured then the protocol family is known so it should be possible to create the DatagramChannel to use that protocol family. It might do so already, but you can check that.
> 
> For the networking and NIO tests then you probably should look at jdk.test.lib.NetworkConfiguration. That has a number of AIX specific comments that may be out of date. After that I think you will need to work through the tests one by one. Between NetworkConfiguration and jdk.test.lib.net.IPSupport, I would expect you have all the infrastructure needed for the tests to not attempt to join IPv4 multicast groups when IPSupport.hasIPv6() is true.

> > Yes, I agree with @AlanBateman and @msheppar . Even when we try to have an IPv4 multicast socket join an IPv4 multicast group, we still fail because the delegate that is created for an IPv4 multicast socket is IPv4/IPv6 (dual stack) in nature. AIX does not allow dual stack (IPv4/IPv6) sockets to join IPv4 multicast groups.
> 
> The "Platform dependencies" section in the java.nio.channels.MulticastChannel (implemented by DatagramChannel) makes it clear that it is implementation specific as to whether a channel to an IPv6 socket can join an IPv4 multicast group. The recommendation is to specify the protocol family when creating the channel. Legacy DatagramSocket/MulticastSocket do not define a constructor that allows the protocol family be specified at xxxSocket create time. That issue has been there since JDK 1.4 when IPv6 support was added. I'm curious why this might be coming up with AIX now.

IIUC what @deepa181  is saying, it looks like the "IPv4 socket being unable to join an IPv4 multicast group" problems surfaced when we moved away from `PlainDatagramSocketImpl` in JDK 17? Probably because the `delegate` created does not factor in the `ProtocolFamily` and though we started with attempting to have an "IPv4 multicast socket join an IPv4 group", we end up trying to have an "IPv4/IPv6 dual-stack socket (the delegate) join an IPv4 group" which AIX doesn't permit.

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PR Comment: https://git.openjdk.org/jdk/pull/14142#issuecomment-1601007522