fix resolv on windows

[ahorek]

bug #4755

[kares]

sun.net.dns.ResolverConfiguration OpenJDK specific right? and it will get hidden away under Java 9+
definitely better than nothing I am just asking if you have any input or ideas on doing this in a different way.

[ahorek]

sun.net.dns.ResolverConfiguration is marked as deprecated, but it still works
jruby 9.2.0.0-SNAPSHOT (2.5.0) 2018-05-10 00c19bb Java HotSpot(TM) 64-Bit Server VM 10.0.1+10 on 10.0.1+10 +jit [mswin32-x86_64]
btw. with this patch the behaviour is the same as 9.1.17.0

I think the only way to do this right and fix https://bugs.ruby-lang.org/issues/12604 is to reimplement this
https://github.com/ruby/ruby/blob/202bbda2bf5f25343e286099140fb9282880ecba/ext/win32/resolv/resolv.c using JNI.

What do you think? Should I try it or is there a better way?

[headius]

@ahorek Is this fix perhaps "good enough" to merge now in case we can't do the "right" fix before the 9.2 release (within a week from now)?

[ahorek]

my only concern is that sun.net.dns.ResolverConfiguration will become deprecated (I tested it on Oracle's Java 8 and Java 10 and it works fine for now)
it should be fixed before 9.2 release, otherwise bundler won't work on Windows.

[headius]

my only concern is that sun.net.dns.ResolverConfiguration will become deprecated

A valid concern. There are builds of 11, can you try to test one of them too? That would get us working into the next LTS version of OpenJDK.

it should be fixed before 9.2 release, otherwise bundler won't work on Windows.

Yikes! 😨 cc @enebo

[ahorek]

I've never used jnr.ffi before and I'm a little bit stucked :). Maybe someone could help me with it? #5178

[ahorek]

daeb255 fixed the issue, thanks @enebo

[enebo]

@ahorek thanks for the first stab too. I agree that jnr/ffi and friends are super confusing in this case. Using the previous call for number of bytes to next call is weird. In Ruby FFI it was a bit easier to figure out. Plus Ruby...