Split-tunneling does not work in Linux Mint

[mwadle]

Describe the bug
Split tunneling does not work on Linux Mint. Apps selected as 'Excluded apps' still have network traffic routed through the VPN.

VPN version:
2.30.0 (2.30.0-noble1)

Affected Platforms:
Linux Mint 22.1 Cinnamon

Prerequisites:

Steps to reproduce:
Turn VPN on with an excluded app selected
Begin capturing traffic through your primary network interface
Generate internet traffic from an excluded app
Note that all internet traffic is either local or sent through the VPN

Alternatively - Exclude your web browser from the VPN connection
Using the excluded web browser, navigate to https://whatismyipaddress.com/
Note that the displayed IP is the VPN's IP address, not yours

Expected result:
Internet traffic from excluded apps does not get sent to the VPN's IP address.

Actual result:
All non-local traffic is sent through the VPN.

Additional notes:

mozillavpn-2025-8-10.log

[mwadle]

I just found this comment and want to mention that the app was installed with apt, not flatpak. Apparently split tunneling issues are to be expected when using flatpak.

[oskirby]

Unfortunately, we cannot support split tunneling with the Cinnamon desktop environment at present. The underlying cause is that Cinnamon doesn't isolate processes by control groups when launching apps, which is necessary for traffic classification by application.

Support for this feature is blocked by linuxmint/cinnamon#12015

We expected this feature to be disabled when installed on Linux mint, which suggests that we have a logic error in FeatureCallback_splitTunnel() that allowed it to be visible.

[mwadle]

Thanks for the thorough response. You saved me from some serious troubleshooting!

I plan to take a look and see why the feature was available to me on Mint, but it'll probably be a week or so before I get the opportunity

[mwadle]

My XDG_CURRENT_DESKTOP string is 'X-Cinnamon' which is interesting because I am running Cinnamon, not xfce.

I was presented the split tunneling option because 'X-Cinnamon' is explicitly allowed here.