This allows one to create AMT(Automatic Multicast Tunneling)
virtual interfaces that provide multicast tunneling.
There are two roles, Gateway, and Relay.
Gateway Encapsulates IGMP/MLD traffic from listeners to the Relay.
Gateway Decapsulates multicast traffic from the Relay to Listeners.
Relay Encapsulates multicast traffic from Sources to Gateway.
Relay Decapsulates IGMP/MLD traffic from Gateway.

To compile this drivers as a module, choose M here: the module
will be called amt.