[Bug]: Windows DNS is not applied when change_system_dns = true

[Plushkin]

Before submitting, please confirm

• I read the README and followed all setup steps in order
• I searched existing issues and found no duplicates
• I am using the latest version of the TrustTunnel console client

Environment details

Summary

On Windows, the TrustTunnel client does not apply system DNS settings even when change_system_dns = true is enabled in the configuration. The tunnel connects successfully, but Windows continues using the previous DNS servers.

Environment

OS: Windows 11 Pro (also reproduced on Windows 10)

TrustTunnel Client: v1.0.23

Execution: run as Administrator

Listener: tun

Interface created: Adguard VpnLibs test tunnel

App version

last

Steps to reproduce

Steps to Reproduce

Start TrustTunnel client on Windows as Administrator.

Tunnel connects successfully.

Check system DNS configuration using:

Get-DnsClientServerAddress

Expected behavior

Expected Behavior

DNS on the TUN interface should be updated automatically to the configured upstreams (for example 1.1.1.1 and 8.8.8.8) or to the local DNS proxy (127.0.0.1) used by TrustTunnel.

Actual behavior

Actual Behavior

DNS on the TUN interface remains unchanged.

Example output:

InterfaceAlias : Adguard VpnLibs test tunnel
InterfaceIndex : 17
ServerAddresses : 46.243.231.30, 46.243.231.31

These DNS servers are inherited from the network or VPN provider and are not replaced by TrustTunnel.

As a result:

TrustTunnel DNS proxy is not used

DNS traffic does not follow the expected routing

DNS leaks may occur

Screenshots

Screenshot 1

Additional Information

Workaround

Manually setting DNS after startup fixes the issue:

Set-DnsClientServerAddress -InterfaceIndex 17 -ServerAddresses 1.1.1.1,8.8.8.8
ipconfig /flushdns

After doing this manually, DNS works correctly through the tunnel.

Notes

Client is started with administrator privileges.

TUN interface is successfully created.

VPN connection works correctly.

Issue appears to be related only to applying DNS settings on Windows.

[sfionov]

Hello! When dns_servers are set, 46.243.231.30 is used just as an address to intercept DNS packets and to forward them to specified DNS servers. When they are empty, packets are forwarded directly to 46.243.231.30 through the tunnel.

[Plushkin]

Additionally I see repeated errors in the logs:

DNS_HANDLER client_handler: DNS proxy request id=XX failed

This happens multiple times after the tunnel is connected.

So the issue is not only the DNS address shown in Windows.
It seems the internal DNS proxy fails to resolve requests.

Configuration:

dns_upstreams = ["1.1.1.1:53","8.8.8.8:53"]

Could this be related to UDP DNS forwarding or MTU?

DNS_HANDLER client_handler: DNS proxy request id=15 failed
DNS_HANDLER client_handler: DNS proxy request id=16 failed
DNS_HANDLER client_handler: DNS proxy request id=17 failed

[Plushkin]

I also tried different DNS transport options such as:
• plain DNS (1.1.1.1:53)
• TCP DNS (tcp://1.1.1.1:53)
• DNS-over-TLS

However the behavior remains the same and the client still prints repeated DNS proxy errors in the logs.

So it does not appear to be related to a specific DNS provider or protocol.

[sfionov]

Hello! Can you please enable debug logging in the config, reproduce the problem, and send debug logs to devteam@trusttunnel.org ?