Multicast Networking Support

# Description

Currently, PPP does not support multicasting. Packets destined for multicast addresses will not be sent to the TUN/TAP adapter, and thus cannot be intercepted.

For that, we may want to use TAP adapters, but this may not always be easily available.

Also, with this, we can push out firewall rules that can block/allow types of multicast traffic (mDNS, etc.), between specific clients.