The goal is not to forward packets blindly like a NAT. You emulate the NAT's behavior by running a TCP state machine in user space and converting packets to re

The goal is not to forward packets blindly like a NAT. You emulate the NAT's behavior by running a TCP state machine in user space and converting packets to regular Android SDK calls. This is what all of the non-root tethering apps likely do, because raw socket access is not allowed.