tun驱动程序实现了虚拟网卡的功能，利用tun驱动可以实现linux 下虚拟网卡的创建与管理。-tun/tap driver implements a virtual NIC functionality, tun represents a virtual point to point device, tap represents a virtual Ethernet devices, both devices for network packet implement different packages. Use tun/tap driver can be tcp/ip protocol stack processing subcontractor pass any good network using tun/tap-driven process, and then re-processed by the process sent to a physical link.