#####参考链接：
1.iOS 9 Network Extension VPN API编程指南http://www.helusi.com/ios9-network-extension-vpn-api/
2.分享开发 iOS 和 Mac 全新 VPN 的艰难历程https://www.v2ex.com/t/264480
3.Potatso原理解析https://www.kidneyband.com/?p=174
#####苹果开发者文档：
NEPacketTunnelProviderhttps://developer.apple.com/reference/networkextension/nepackettunnelprovider?language=objc
SimpleTunnelhttps://developer.apple.com/library/prerelease/content/samplecode/SimpleTunnel/Introduction/Intro.html