dnsmasq on loopback only

os/dns/default.nix

@@ -8,6 +8,10 @@
       # Not an issue for routing, but we need local DNS with conditional forwarding.
       enable = true;
       resolveLocalQueries = true;
+      settings = {
+        interface = "lo"; # Bind on loopback interface only, so other interface (e.g. libvirt) can run their own DNS server
+        bind-interfaces = true; # Required for above to do anything
+      };
     };
   };
 }