Not THAT all code.
Some frameworks, in their 2015 incarnations break with IPv6, as happens for example with some Java frameworks (been there, done that..)
One example is reverse DNS from some java frameworks/libraries.. and that is just one of the cases.
That breaks some of my code in interceptors for WS-Security.
Now, you might say that that should be in the webserver (nginx, apache..) but there are advantages in having the auth in the java.. as for example some ipv6 addresses/ranges might be considered safe, etc.
Anon, as this might get serious flak.