[Dnsmasq-discuss] How to turn off DNS?

[Tom Isaacson]

Apologies if this is an obvious question but I'm new to this.

I have a device with internal Wifi setup as a hotspot. This device can either be standalone or connected to Ethernet and provided with internet access. When I connect a phone to the Wifi I want it to have access to internet if it's available, otherwise it should be able to use it's mobile data at the same time. Unfortunately some phones (like iPhone) won't allow you to use mobile data if they think the Wifi provides internet. We didn't think this was possible until we found another product that achieves what we want. It seems that they set the DHCP Gateway but don't set a DNS server unless internet is available on the Ethernet.

Right now dnsmasq.conf is set to:
expand-hosts
addn-hosts=/etc/
domain=local
dhcp-range=192.168.76.2,192.168.76.100,12h
dhcp-option=3,192.168.76.1
interface=ap
bind-interfaces
cname=smith,jones,jones.local

This allows the phone to access internet on Ethernet if it's available, but the phone won't use its own mobile data. I managed to get that to work by adding:
dhcp-option=6
but now the phone won't access the internet from Ethernet. I think I need something halfway - allow the DNS to be set from Ethernet if it's available, otherwise don't set it.

Does anyone have any suggestions how I might achieve this?

Tom Isaacson