/proc/net/fib_trie was denied or failedID:
FIB_TRIE_DENIEDCategory: Routes and network stack Status in RKNHardering 2.10.0: Active check Role in the verdict: Medium
This page describes the actual implementation in RKNHardering 2.10.0. It distinguishes what can be done without root, what requires root, and where a mitigation only reduces one signal without hiding the VPN as a whole.
detectFibTrieAccess() only opens /proc/net/fib_trie. A successful open emits nothing; EACCES or EPERM produces SELinux denies, ENOENT is neutral, and any other errno also emits a line. In the deep checker, the kind is neither high-confidence nor informational, so it produces medium-confidence needsReview evidence.
Opening /proc/net/fib_trie returned EACCES, EPERM, or any error other than ENOENT.
This checks access to a diagnostic path; it is not VPN detection. On modern Android, denial for untrusted_app may be normal policy. The line warrants review, but it is not a reason to “fix” SELinux.
How the line affects the report: The line does not produce a final verdict on its own, but it sets needsReview=true and adds medium-confidence evidence.
The name can be misleading: denial normally improves privacy and closes an information leak. The code does not attempt to read the contents after a successful open and does not report “accessible.” The shell and app UID run in different SELinux domains.
This line must be evaluated together with neighboring signals. A clean result from a single API does not simultaneously cover Java Binder, libc, raw netlink/syscalls, procfs/sysfs, local sockets, and server-side indicators.
Do not weaken anything. Record the Android version and ROM, then compare the result with a clean device running the same build. If the app reports errno=N, decode the errno and check whether the procfs mount is damaged.
Do not add an allow rule merely to make the line disappear; that would expose route data to an ordinary app. For laboratory diagnostics, inspect AVC logs instead of putting SELinux into permissive mode.
adb shell 'cat /proc/net/fib_trie >/dev/null; echo shell_rc=$?'
adb logcat -d | grep -E 'avc: denied.*fib_trie' | tail -30
Shell success or failure does not reproduce the untrusted_app context; the final result must be checked inside RKNHardering.
After any change, force-stop both RKNHardering and the VPN client, start them again, and repeat the full scan. Zygisk, Xposed, and kernel modules usually require a reboot. Compare not only this line but also neighboring signals: a partial hook often creates inconsistencies between APIs.
The probe itself runs with ordinary app permissions and does not request root. The ADB commands below are for orientation only: adb shell runs under a different UID and may see either more or less than the app process. The decisive test is to run the check again after a force-stop.
SELinux permissive mode or a broad allow rule exposes network state and weakens the entire sandbox. That is worse than the review signal itself.
Remove the test sepolicy rule, restore enforcing mode, and reboot the device. Confirm that getenforce returns Enforcing.
Medium. Verified against the errno branches; the kind remains a medium-confidence review finding.
The status of a third-party solution does not automatically carry over to this device. A module developer’s claim is only the initial hypothesis; confirmation requires a reproducible RKNHardering result on the specific Android version, firmware, and kernel.
native_signs_probe.cpp — native probe implementation.VpnNativeDetectorChecker.kt — deep VPN verdict and confidence.NativeSignalId.kt — complete ID registry.NativeSignalCatalog.kt — category, slug, and line mapping.Related signals: bpf-map-accessible, sysfs-vpn-leak, syscall-unavailable.