@clearscreen said in Avahi trying to broadcast on public interface?:
I was just looking at mdns-bridge source code, but only realized now you're the author
Yes. I'm also the maintainer of the pfSense Avahi package, which is why I felt compelled to write mdns-bridge. 
I’m not very familiar with mDNS, but I’m thinking of trying to implement one-way reflection (blocking either queries or broadcasts in a single direction). My motivation is to limit fingerprinting of my home network while allowing trusted subnets to see devices on less trusted subnets. Before I dive in, is there any technical reason this wouldn’t be feasible? Just want to understand if there’s a fundamental limitation and I figured I might as well ask you first.
With mdns-bridge, you do not block queries or responses, but choose what mDNS names are shared by each network segment. Avahi uses a similar approach, but is limited to what in mdns-bridge terms would be a Global Allow filter list only.
mDNS-Bridge is designed to give you detailed control of what mDNS names each segment is allowed to export or import, but I recommend keeping things simple if possible. I recommend starting with a Global Allow filter list to limit the overall scope, and exploring from there as needed.
One thing to keep in mind, as noted in the mDNS-Bridge README filters that include hostnames are best used only in deny filters.