ANDROID: selinux: modify RTM_GETLINK permission

Map the permission gating RTM_GETLINK messages to a new permission so
that it can be distinguished from the other netlink route permissions
in selinux policy.

This is a temporary Android-only patch that will be deprecated in
newer kernels once the long-term solution lands as discusssed on the
mailing list [1]. The maintainer's recommended solution is more
general, much more complex, and likely not suitable for backporting.
This patch provides the minimal change needed for Android including
the userspace settable trigger which ensures that the permission
change is only applied to the newest version of Android which
contains the changes needed for userpace compatibility.

[1]: https://lore.kernel.org/selinux/20200116142653.61738-1-jeffv@google.com/



Bug: 141455849
Bug: 148218425

Test: CtsSelinuxTargetSdkCurrentTestCases
Test: atest bionic-unit-tests-static
Test: atest NetworkInterfaceTest
Test: Connect to Wi-Fi network
Test: Set up hotspot
Test: Cast from device
Test: Pair Bluetooth device
Test: Call getifaddrs() directly from within an app.
Test: Call NetworkInterface#getNetworkInterfaces() from within an app.

Change-Id: I7b44ce60ad98f858c412722d41b9842f8577151f
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Git-repo: https://android.googlesource.com/kernel/common


Git-commit: ba835f8db4a3005e34542a3af7f19fce30ade6fd
Signed-off-by: Alam Md Danish <amddan@codeaurora.org>