观察数据流向

参考资料：https://cclinuxer.gitee.io/2020/08/Linux%E5%86%85%E6%A0%B8%E8%B0%83%E8%AF%95%E4%B9%8Biptables%E8%A7%82%E5%AF%9F%E6%95%B0%E6%8D%AE%E5%8C%85%E6%B5%81%E5%90%91/

https://cclinuxer.gitee.io/2020/08/Linux%E5%86%85%E6%A0%B8%E8%B0%83%E8%AF%95%E4%B9%8Bnetfilter%E5%87%BD%E6%95%B0%E5%AE%9A%E4%BD%8D/