Update README

README.md

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-# cordova-plugin-tun2socks
+# cordova-plugin-tun2socks
+
+This Cordova plugin provides the ability to start a system-wide VPN for Android devices.
+
+We use [tun2socks](https://github.com/ambrop72/badvpn-googlecode-export/blob/master/tun2socks/badvpn-tun2socks.8) as an adapter; it receives all of the device’s traffic through the VPN network interface (TUN) and forwards it to a SOCKS server.
+
+To handle DNS resoution, we have implemented a local DNS resolver that intercepts DNS queries over UDP and proxies them over TCP (to Google Public DNS) through the SOCKS server.
+
+### Target Devices
+
+This plugin targets Android devices running Marshmellow (API 23), or higher. This requirement stems from calling `bindProcessToNetwork`, a [connectivity API](https://developer.android.com/reference/android/net/ConnectivityManager.html#bindProcessToNetwork(android.net.Network)) introduced in version 23, which allows the client application traffic to bypass the VPN.
+
+### Code Sources
+
+We re-use and have used as a starting point open source code from [Psiphon](https://psiphon.ca/uz@Latn/open-source.html), specifically https://github.com/mei3am/ps.
+
+ * `src/android`:
+  * starting point: https://github.com/mei3am/ps/tree/master/Android/app
+  * `Android/app/src/main/java/ca/psiphon/PsiphonTunnel.java` -> `src/android/org/uproxy/tun2socks/Tunnel.java`
+  * `Android/app/src/main/java/com/psiphon3/psiphonlibrary/TunnelManager.java` -> `src/android/org/uproxy/tun2socks/TunnelManager.java`
+  * `Android/app/src/main/java/com/psiphon3/psiphonlibrary/TunnelVpnService.java` -> `src/android/org/uproxy/tun2socks/TunnelVpnService.java`
+ * `src/badvpn`:
+  * built upon Psiphon's fork of [badvpn](https://github.com/ambrop72/badvpn).
+  * starting point: https://github.com/mei3am/ps/tree/master/Android/badvpn
+  * uProxy-specific changes mostly confined to tun2socks/tun2socks.c and marked with `// ==== UPROXY ====` (like Psiphon-specific changes)
+ * `src/android/libs/jsocks.jar`:
+  * http://jsocks.sourceforge.net/