| PPPoPPTP-Android plugin |
| ======================= |
| |
| This plugin was written for AOSP project from scratch. It has nothing to do with |
| accel-pptp plugin [1]. |
| |
| This plugin adds support for upstream kernel PPTP implementation in pppd daemon. |
| Only PNS (client) part of PPTP is implemented, as we don't use Android devices |
| in PAC mode. |
| |
| In general case, the execution flow for VPN startup on Android devices is: |
| 1. Run PPTP client (mtpd) |
| 2. mtpd obtains remote Call ID on OCRP (Outgoing-Call-Reply) packet |
| 3. mtpd creates PPTP socket |
| 4. mtpd runs pppd, passing PPTP socket as to pppopptp-android (as parameter) |
| 5. pppd dlopen() pppopptp-android plugin (because it received corresponding |
| arguments from mtpd) |
| |
| Main task of this plugin is to obtain PPTP socket FD from mtpd and pass it |
| back to pppd when .connect() callback is executed. |
| |
| All control packets are handled in mtpd. PPP packets (like LCP) are handled in |
| pppd. Data packets are handled by kernel PPTP driver. |
| |
| [1] http://accel-pptp.sourceforge.net/ |
