To install the IPv6 extension you need to update the jdk runtime classes
(ie: rt.jar) to include the new version of some of the classes, and you
also need to copy a new dynamic librairy which will be used by the new classes.

This can be done under bash by:

cd jdkv6ext

export JDKDIR=/path/to/your/jdk_directory
export JDKLIB=$JDKDIR/jre/lib
export JDKARCH=`find $JDKLIB -name 'libnet.so' | sed "s|^$JDKLIB/||" | sed 's|/libnet.so$||'`

(cd classes ; jar uvf $JDKLIB/rt.jar `find . -type f -name '*.class'`)
cp jre/lib/$JDKARCH/*.so  $JDKLIB/$JDKARCH/
