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REFACTOR.md

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Why refactor?

Currently, we extensively use globals, mostly once_cell statics.

This is niceish for a binary crate, but we want to refactor geph4-client to be a proper library crate.

This has several benefits:

  • iOS support is easier and more robust
    • iOS does not support multiple processes, so currently we use a hack where geph4-client is compiled as a C library with a single function that calls the main function. But that's a very bad hack overall, due to reentrance etc issues.
  • Geph can be embedded into GUIs like gephgui-wry rather than separately compiled and packaged in. This simplifies coding and packaging greatly.

The interface after refactoring

  • A GephClient struct, which can be constructed by passing in a configuration struct. This GephClient struct will have methods like send_vpn, recv_vpn, tcp_connect, exit_list, and stats. It can be turned on and off at any time, so it will also have connect, reconnect, and disconnect methods.
  • A GephClientProxy struct, which manages proxying by TUN, SOCKS5, etc, also configured by passing in a configuration struct. This is a conditionally-compiled component.

geph4-client will maintain its old legacy interface, but also support reading in a --client-config and --proxy-config through YAML.

Usage in gephgui-wry

This is relatively straightforward, given that gephgui-wry is also a Rust program. The main thing to note would be that gephgui-wry itself needs to stay in the foreground, so e.g. tray support is crucial.

Before we make those changes, we can still use geph4-client with the old CLI interface.

Usage in geph-android

We can still use the geph4-client CLI as a drop-in, but eventually should move to compiling geph4-client as a JNI library.

We can do something like this: https://mozilla.github.io/firefox-browser-architecture/experiments/2017-09-21-rust-on-android.html

This would require designing a good C API for geph4-client, that involves constructing a struct geph_client *, passing it to functions like geph_send_vpn(struct geph_client *, char *, unsigned int), and manually freeing clients by calling something like geph_free(struct geph_client *). That should not be too hard, and we need that for iOS anyway. This C API can live in a special helper crate.

(One good way would be to represent a geph_client as a index into a concurrent slab, which prevents any memory safety issues.)

Usage in iOS

We call the C API.