NetWork Extension

tun2socks

https://www.yuanmas.com/info/8VaPVVEZOr.html
https://blog.csdn.net/binhoubin/article/details/63251662

Packet Tunnel Provider

https://medium.com/@zicodeng/how-vpn-works-b7549dcc6ce4
https://kean.blog/post/packet-tunnel-provider
https://www.v2ex.com/amp/t/264480/1

ss

https://muyishuangfeng.github.io/2019/09/23/Socks、shadowsocks、vmess协议的差异/
https://github.com/Desgard/iOS-Source-Probe/blob/master/Python/Shadowsocks/Shadowsocks%20Probe%20I%20-%20Socks5%20与%20EventLoop%20事件分发.md

socks5 proxy

https://securityintelligence.com/posts/socks-proxy-primer-what-is-socks5-and-why-should-you-use-it/

TUN介绍

https://blog.csdn.net/lsz137105/article/details/100595948

NEPacketTunnelVPNDemo

https://github.com/davlxd/NEPacketTunnelVPNDemo/blob/master/NEPacketTunnelVPNDemoTunnel/PacketTunnelProvider.swift