* Add IPv6 support for (*, G), i.e., on-demand, routing rules.
In SMCRoute 1.99.0 IPv4 support for source-less multicast routes was
added. Adding support for IPv6 should be fairly straight forward, but
needs figuring out the kernel interface and extensive testing.
* Support for detecting link up/down on interfaces
Also requires updating VIF/MIFs and mroutes accordingly.
Optimal, and almost required, behavior would be to handle such
transitions without losing any traffic over established/active