IPv6 stackless exception

When there is no available IPv6 stack on the host machine, an exception is thrown out of `utils` when checking for permissions.

Start by locating the utils code that checks permissions and reproduce the behavior on a host without an available IPv6 stack. Trace the exception path and inspect any related tests; done means the permission check handles the missing IPv6 stack without throwing an unexpected exception.

Written by the indexing model from the issue text.