Overlay network

参考资料

• TUN/TAP内核文档：https://www.kernel.org/doc/Documentation/networking/tuntap.txt

• Network Tunnels with Linux: https://www.jumpingbean.co.za/blogs/mark/linux-network-tunnels

• IP over UDP tunnel with socat: https://www.gabriel.urdhr.fr/2016/01/12/ip-over-udp-with-socat/

• Foo over UDP: https://lwn.net/Articles/614348/

• Multi-Host Networking Overlay with Flannel: https://docker-k8s-lab.readthedocs.io/en/latest/docker/docker-flannel.html（这网站里有很多docker网络相关的动手小实验）