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

[Daniel Fuchs]

On Mon, 12 Jun 2023 19:27:28 GMT, Deepa Kumari <duke 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.
>
>> > 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?

> 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.

IIRC It has never been possible to create a non-dual `MulticastSocket` / `DatagramSocket` without setting the property `-Djava.net.preferIPv4Stack=true`. The possibility to select a protocol family independently of this property is only available with `DatagramChannel`.

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PR Comment: https://git.openjdk.org/jdk/pull/14142#issuecomment-1601038453