Strange DNS behaviour on hotspot - Google DNS?

keenly-lagged-acts

Since I self-host quite a lot, I need some specific DNS configurations. What I noticed is that my setup works correctly when I am connected from any non-GrapheneOS device and on any non-hotspot connected device.

However, when I connect via my GrapheneOS phone or when I am connected to a hotspot, my graphene phone starts acting as a DNS resolver.

I tried both with and without the private dns setting enabled (OFF & Private DNS provider: dns.quad9.net). DNS answer when connected from my laptop on the GrapheneOS hotspot:

nslookup XXXXXXXX
Server:  UnKnown
Address:  192.168.38.156

Non-authoritative answer:
Name:    XXXXXXXX
Addresses:  64:ff9b::54c1:2218
          YY.YY.YY.YY

DNS answer when not connected to the hotspot:

nslookup XXXXXXXX
Server:  dns9.quad9.net
Address:  9.9.9.9

Non-authoritative answer:
Name:    XXXXXXXX
Address:  YY.YY.YY.YY

So, the address '64:ff9b::54c1:2218' is strange and causes some trouble. I'm a bit worried as to a) why my GrapheneOS phone acts as a DNS server and b) it seems to relate to a service Google provides (https://developers.google.com/speed/public-dns/docs/dns64), but I suppose the latter does not necessarily mean a thing as they simply implement https://www.rfc-editor.org/rfc/rfc8215.html .

In any case, I don't want my phone to resolve DNS requests. Is this a bug or a feature?

DeletedUser286

keenly-lagged-acts

keenly-lagged-acts Since I self-host quite a lot, I need some specific DNS configurations. What I noticed is that my setup works correctly when I am connected from any non-GrapheneOS device and on any non-hotspot connected device.

Are you connected to a LAN device that is serving a LAN IP address and DNS server IP's to your laptop? eg: router

Do your self hosted devices have both LAN and WAN access?

keenly-lagged-acts

DeletedUser286
There are basically three options:

Connected to my own LAN -> yes, I have my own DNS server - no issues, everything resolves to a local address. On most devices I actually still use the quad9 DNS, but I do have some devices that switch to local DNS server when connected to my own LAN.
Connected to another trusted LAN -> I typically use the Quad9 DNS, see the example in my first post
Connected to my hotspot -> That's via the 4g/5g connection of my phone then, my mobile provider also offers DNS indeed, but that's a different DNS sever than the one reported by nslookup .

DeletedUser286

keenly-lagged-acts
On the device/s that you connect to your GrapheneOS hotspot, manually set the DNS server IP's for that particular WiFi connection.

keenly-lagged-acts

DeletedUser286

You mean on the device itself? Of course that's an option that works, but a) it's not very convenient and b) I want to understand why GrapheneOS acts as DNS server. Is that expected behaviour then?

DeletedUser286

keenly-lagged-acts
Any device that is configured solely using DHCP will obtain the IP address, DNS server address/es, gateway address, etc from the router or hotspot.
Dynamic Host Configuration Protocol (DHCP) is a network management protocol that automatically assigns IP addresses and other network configuration parameters to devices on a network.
Unless the DNS server address/es are manually configured on the connecting device, the router or hotspot will pass the network configuration parameters (including DNS) to the connecting device using DHCP.
Would I be correct in saying you would like to manually set the DNS server address that the GrapheneOS device hotspot serves to LAN clients?

keenly-lagged-acts

DeletedUser286

Yes, that is correct. Or at least understand how it works and why it provides that 64:ff9b::54c1:2218' address which breaks my local apps.

keenly-lagged-acts

No actually, the phone itself also uses this DNS. even though I configured it to use the quad9 DNS servers..

keenly-lagged-acts

Could my topic start post be deleted please, it contains a sensitive IP address which I forgot to redact @GrapheneOS