Wifi vs Mobile Data

GrimMalazan

Hi,
On my home network I have a pi-hole. Because my router has the pi-hole server as it's DNS, whenever I'm connected to Wifi (on any android device), there will be a small exclamation mark next to the wifi symbol indicating that there is "no internet" connection, even though everything works fine. I assume some sort of ping is being blocked by the DNS sinkhole.. What this however leads to, is that grapheneos will "connect" to the wifi but it will not switch over from mobile data, i.e., wifi is technically marked as connected, but the phone will keep using mobile data. The only way to switch to wifi, is to manually click on disconnect and then connect again. Then grapheneos finally starts to use Wifi. This same thing happens if there is just a router that actually is not connected to the internet. I can connect to the router via wifi, but the phone will not automatically switch over.
Now to my question, is there any way how to force grapheneos to connect wifi automatically? The "Auto-connect" is toggled on, so I would assume this should work out of the box, but apparently the phone tries to avoid networks without internet (which is at least my assumption).

Any help with this would be greatly appreciated :)

thmf

GrimMalazan is there any way how to force grapheneos to connect wifi automatically?

I'd recommend to try solving the actual networking issue rather than a symptom on your phone. Trying to fix this on your phone means a nonstandard configuration, thus may affect how it works with other networks.

Does this happen on any other WiFi or strictly on your home network?

For a start, can you temporarily set your router's DNS and router's DHCP's DNS to something like 9.9.9.9, then reboot your phone, and then check of the issue is still happening?

vividsquirrel

The option most similar to what you're describing is to turn off internet connectivity checks in settings > network > connectivity check. This will stop your phone from deciding to use the WiFi connection based on it being able to ping a server. However, I would try other things first because disabling connectivity checks will mean your phone will not know when your internet actually doesn't work. It will also break captive portals for public WiFi networks.

IMO the option to try first is to fix whatever is making the OS think it doesn't have internet. Go back to connectivity check settings and see which one you're using. I think the default is to use Google's server because it will make your phone blend in with other Android devices. You might have a blocklist enabled on the Pi-Hole that is blocking gstatic.com (the domain used for Google connectivity checks). You can also try changing connectivity checks to the GrapheneOS server.

thmf

vividsquirrel I think the default is to use Google's server

Small correction. By default it's the GrapheneOS server (source)

You can change the connectivity check URLs via the Settings > Network & internet > Internet connectivity check setting. At the moment, it can be toggled between the GrapheneOS server (default), the Standard (Google) server used by billions of other Android devices or Off.
By default, the GrapheneOS server is used [...]

GrimMalazan

thmf Disabling the connectivity check worked like a charm! :)

Now, I don't view it as a problem that pi-hole blocks "heartbeat" connections. However, if you say that it indeed is problematic, I'll have a look!
Briefly looking over what is blocked; gstatic is not blocked, but "connectivitycheck.gstatic.com" is. I most likely at some point in the past saw this and deemed it unnecessary thus I blocked it (the idea may have very well been "if X is not necessary then block X"). In fact looking further "connectivitycheck.grapheneos.network" is blocked as well, because I have a blocking regex "^.*connectivitycheck.*".

thmf

GrimMalazan In fact looking further "connectivitycheck.grapheneos.network" is blocked as well, because I have a blocking regex "^.connectivitycheck.".

Then here it is. Good find! Once fixed on the PiHole's side, don't forget to enable the default GrapheneOS connectivity checks back in phone settings to restore captive portal functionality.