RTnet from userspace

[Antoine Hoarau via Xenomai]

Hi,
I'm trying to run rtnet executables (ex: rtifconfig) from user-space.
User is in the xenomai group and can run xenomai applications without
sudo/being root.
rtifconfig results in:  ioctl: Operation not permitted
What would be the best/most linux way to only authorize the xenomai group
to access those functions ?
Thanks !