Linux has network namespaces, which can be used to isolate programs so they don't see any external networking when no VPN is available. Does android not use this for its VPN feature?
Lol. On the other hand, I use Linux network namespaces to make programs run outside the VPN on a specific machine that has the whole system configured to go through the VPN. So yeah if you get namespaces you can use them to both isolate programs and also bypass the VPN.
