This project show how to implement simple bridge via tun interface. The main program(bridge.c) will create two tun interface: tun0, tun1. Then keep forwarding IP packet between the two interfaces. To demonstrate the bridging functionality, use the setup.sh to create a seperate network namespace and move the tun1 into that namespace. Then setup.sh will config address for each interface. After that we can ping 10.10.0.100 from host network and ping 10.10.0.200 from ns0 network namespace.