[Android Apps and Games] DiamondJohn:
I am running Bliss Android 11 custom ROM and there is no interface to see the DNS used while on mobile provider network data (Vodafone AU). I can get to it via getprop in a shell (see below). Its easily visible for WiFI, just not while on mobile.

To your direct question,

i) I dont use Chrome as my web browser, I use DuckDuckGo's browser & it's search engine within my browser

ii) The ads that I am seeing on Mobile network are in Aps. I don't browse the web so much off of WIFI; buit they are there as well when on the mobile provider network

ii) when I set my WiFI DNS 's to google DNS servers, the ads are blocked as expected while on WiFI. The same as if using the 1.1.1.1 DNS's. ie it makes not difference which DNS I use, the host file is checked first. I dont get where the hostfile is ignored, when I switch to mobile network

Did I miss any of your questions?

This is where it gets interesting. Previously, I used to check & set lines in my build.prop file once on boot, and it would stick when I switched between WiFi and network data. However, now, using the Magisk resetprop feature, at first, the settings sticks, but after a few seconds, the DNS is switched back to the providers DNS. I modded my previous script (which worked a charm in A8) to use the magisk method, and log the values before and after i set them in code, and these are extracts from my logs at various points in time/stages. The BEFORE and AFTER are getprop shell command outputs; the only apparent dodgy one is for net.dns[n], so I am only showing that log section. So the log shows that milliseconds after setting the property, its as I set it, but the next run, the BEFORE shows it has reverted! Logically, the next BEFORE should stay on the value of AFTER of the previous stage/run. So stage 3 shoudld of set it and it should show the new setting (1.1.1.1) on before for stage 5; but it has somehow switched back. ARRRRgggghhhh!

>>Stage 1, while on WIFI
20 Starting work on line net.dns at 2023-04-18 15:03:29
BEFORE: net.dns1=1.0.0.1 at 2023-04-18 15:03:29
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:03:29
BEFORE: net.dns2=1.1.1.1 at 2023-04-18 15:03:29
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:03:29

>>Stage 2, after a while, still on WiFI
20 Starting work on line net.dns at 2023-04-18 15:08:26
BEFORE: net.dns1=1.1.1.1 at 2023-04-18 15:08:26
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:08:26
BEFORE: net.dns2=1.0.0.1 at 2023-04-18 15:08:26
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:08:26

>>Stage 3, just after switching to Network data
20 Starting work on line net.dns at 2023-04-18 15:09:30
BEFORE: net.dns1=10.143.147.147 at 2023-04-18 15:09:30
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:09:30
BEFORE: net.dns2=10.143.147.148 at 2023-04-18 15:09:30
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:09:30

>>Stage 4, after a while on Network Data
20 Starting work on line net.dns at 2023-04-18 15:10:19
BEFORE: net.dns1=10.143.147.147 at 2023-04-18 15:10:19
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:10:19
BEFORE: net.dns2=10.143.147.148 at 2023-04-18 15:10:19
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:10:19

>>Stage 5, some more time on Netwrok data
20 Starting work on line net.dns at 2023-04-18 15:10:52
BEFORE: net.dns1=10.143.147.147 at 2023-04-18 15:10:52
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:10:52
BEFORE: net.dns2=10.143.147.148 at 2023-04-18 15:10:52
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:10:52

>>stage 6. After switch to WiFI
20 Starting work on line net.dns at 2023-04-18 15:12:44
BEFORE: net.dns1=1.0.0.1 at 2023-04-18 15:12:44
AFTER: net.dns1=1.1.1.1 at 2023-04-18 15:12:44
BEFORE: net.dns2=1.1.1.1 at 2023-04-18 15:12:44
AFTER: net.dns2=1.0.0.1 at 2023-04-18 15:12:44

I have attached my script for reference. The includes are basically setting the log file location and name, and bb=busybox, and logging the entry and exit of the script. Its shared by all my boot scripts

I am surprised I am the only one that is seeing this behaviour. I have a Pixel 4a 4G and I saw the exact same behavior when I was running the stock Google ROM, which from my understanding would be running a close to AOSP ROM. I think it is something Vodafone AU are specifically doing in their network. Like regulary changing the DNS while it is connect to their data newtwork :poop:

And thanks for your time and consideration(y)