[ipv6] Regarding 8220673: Add test library support for determining platform IP support

[Chris Hegarty]

Alan,

> On 9 May 2019, at 07:22, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> 
> On 08/05/2019 12:02, Chris Hegarty wrote:
>> :
>>> 
>>> New webrev: http://cr.openjdk.java.net/~aeubanks/8220673/webrev.03/
>> 
>> :
>> 
>> P.S. adding nio-dev since there are a few tests in that area
>> being updated.
> Thanks for forwarding.
> 
> IPSupports.skipIfConcurrentConfigurationIsInvalid is a bit strange and I think the first use of SkippedException in the jdk tests. I'm tempted to suggest this should be a key that tests should select on via the @requires tag but that may not be feasible because it depends on properties such as preferIPv4Stack.

The alternative of using `@requires` was considered and rejected, for
the same reason you mention [1]. Additionally, using SkippedException
will be more straight forward to detect skipped tests and the reason
( the IP configuration ) why the test was skipped.

> So I guess the approach is okay but we should rename the method to start with "skipTest" as it's not clear from the use-case what is being skipped. Also "ConcurrentConfigurationIsInvalid" is vague and I think it would be useful if the method description could emulate the conditions a bit better so that someone seeing a IPSupport.skipTestXXX knows what is means.

I agree that the method name could be improved. It’s really:

“skip test if cannot create a minimally-operational IPv4 or IPv6 socket"

Some concrete method name suggestions ( more welcome ):

  - IPSupport::skipTestIfNonOperational
  - IPSupport::skipTestIfCannotCreateAnyIPSockets
  

Suggested method-level documentation improvement:

  /**
   * Ensures that the platform supports the ability to create a
   * minimally-operational socket whose protocol is either one of IPv4
   * or IPv6.
   *
   * <p> A minimally-operation socket is one that can be created and
   * bound to an IP-specific loopback address. IP support is
   * considered non-operational if a socket cannot be bound to either
   * one of, an IPv4 loopback address, or the IPv6 loopback address.
   *
   * @throws SkippedException if the current networking configuration
   *         is non-operational
   */
  public static void skipTestIfNonOperational() throws SkippedException


-Chris.

P.S. 8220673 has been pushed already, but we should continue the
discussion here and I will create a follow-on JIRA issue to track it.

[1] https://mail.openjdk.java.net/pipermail/net-dev/2019-April/012348.html