[BUG] - DNS with VPN (per tunnel DNS) is unreliable

[Tulis12]

Describe the bug
When I run a tunnel with DNS server set, it works, but after some time (24h-48h), the systems stops using that DNS server (even without rebooting the phone or restarting the app)

Smartphone (please complete the following information):

• Device: Guangdong Oppo Mobile Telecommunications Corp. realme 14 pro+ 5G
• Android Version: Android 16
• App Version: v4.3.1 google
• App mode: VPN (just the system one, without root or kernel)

To Reproduce
Steps to reproduce the behavior:

1. Turn on any tunnel with DNS server
2. Wait for 24-48h
3. System now uses some other DNS (probably the router one)

Expected behavior
Systems and other apps should use the DNS provided in the tunnel

Additional context - How do I know that the apps are not using the DNS?
Some apps (for example Bitwarden, Chrome) work for the first 24-48h, then it just uses some other one (checked also with Termux or Ping Tools) that I actually cannot lookup my local DNS rules.

[zaneschepke]

Hello!

Have you tried updating to the latest version 5.0.7 to see if there are any improvements in this?

Also, have you tried disabling private DNS? With your type of device, it can sometimes start using private DNS again after this duration.

[Tulis12]

I updated and I will use it to see if the issue persists.

As for private DNS I don't have it enabled

[bar-g]

I've seen such undesired (and never configured) sudden "fallback to hardcoded default DNS" behavior is sometimes even caused by some operating system. In particular, with systemd for example.

Something you could try might be to temporarily configure your "per tunnel DNS" as global DNS in wgtunnel and afterwards in the operating system, to see if the behavior is different in these cases.