全国dns服务器IP地址大全 https://moneyslow.com/dns-ip.html
全球ping监控 https://ping.pe/
网卡流量统计 Linux network statistics https://humdi.net/vnstat/
Global DNS check https://www.whatsmydns.net/
隧道工具大全 Awesome-tunneling https://github.com/anderspitman/awesome-tunneling
隧道GRE tunnel setup：https://community.hetzner.com/tutorials/linux-setup-gre-tunnel
https://aoyouer.com/posts/gre-tunnel-transit/