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

[Alan Bateman]

On Wed, 21 Jun 2023 15:18:32 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

> 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`.

Right now, Net.canIPv6SocketJoinIPv4Group() returns false on AIX so it will never attempt to join an IPv4 multicast group when the socket is IPv6.  The old DatagamSocketImpl didn't have an eager check, which makes me wonder what AIX supports and doesn't support, it's not clear.

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PR Comment: https://git.openjdk.org/jdk/pull/14142#issuecomment-1601085660