8241786: 3 DatagramChannel tests and 2 MulticastSocket tests fail due to "SocketException: No buffer space available"

[Chris Hegarty]

Daniel,

> On 1 Apr 2020, at 18:42, Daniel Fuchs <daniel.fuchs at oracle.com> wrote:
> 
> Hi,
> 
> Please find below a fix for:
> 
> 8241786: 3 DatagramChannel tests and 2 MulticastSocket tests
>         fail due to "SocketException: No buffer space available"
> https://bugs.openjdk.java.net/browse/JDK-8241786

Good work. A really tough issue to diagnose.

This is a functional change that affects the product build. Maybe that
would be a little clearer from a different bug synopsis. Suggest
something like:

  Improve heuristic to determine default network interface on macOS

> webrev:
> http://cr.openjdk.java.net/~dfuchs/webrev_8241786/webrev.01/

DefaultInterface.java

  Unless I'm mistaken, the first IPv4+IPv6+nonLinkLocal interface is not
necessarily returned. The second will be returned if there are two such
interfaces. I'm not saying that this is necessarily a problem, just
trying to reconsile the code with the comment. Maybe the `preferred` can
be skipped, just returning such an IPv4+IPv6+nonLinkLocal if found.

-Chris.