Leaks when using kernel module backend on Android

[Rachid Alaoui]

Hello all,

I have recently configured a WireGuard tunnel between my Android phone and a CentOS Server. The userspace backend implementation functions as expected, I also get the key icon in the status bar on Android.

After granting root access to the WireGuard app and enabling the kernel module backend, I discovered that some traffic was being routed outside the tunnel. To confirm this, I created a dummy VPN profile and connected to it. As expected, I lost internet access entirely. However, suprisingly, I still received notifications from Firebase Cloud Messaging (FCM).
Additionally, the key icon is missing from the status bar when using the kernel module backend.

Stock Android with Google Play Services
Wireguard for Android : v1.0.20231018
Kernel module backend : v1.0.0

Best,
Rachid Alaoui
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