ipv6 MDNS support

[deanagny]

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Is your feature request related to a problem? Please describe.

mdns-repeater does not support ipv6, and the author seemingly has no intention of adding support.
geekman/mdns-repeater#3

I now have an IPv6 only client subnet, and these become more common over time, using tayga to provide 6to4.

Printers and other devices are on a seperate subject, do avertise their ipv6 addresses in MDNS, but as mdns-repeater doesn't support ipv6 doesn't repeat these into the ipv6 only subnet.

Describe the solution you like

Support for mdns relaying between suubnets using ipv6

Describe alternatives you considered

I have not come up with any workable workarounds but I can see the following options

• Write a patch for mdns-repeater
• Switch plugin to Avahi
• Add Avahi plug to provide choice

Additional context

https://forum.opnsense.org/index.php?topic=13238.0

EDIT: Spelling