How to manipulate SR-IOV virtual functions link state

Issue

Proper SR-IOV Virtual Function link up/down simulation.

It is not possible to simply pull the networking cable out from the physical port of the NIC itself.
This will put down the physical function itself as well as all the virtual functions possibly running on it.

Sometimes it is also useful not to put down all the possible running virtual functions on a physical function when it goes down for some reason.
Sometimes it is also useful not to put down virtual functions running on some physical function when it comes down.