Add cross-platform proxy crate (For macOS)

[tyreseluo]

PR Content

Add cross-platform proxy crate with macOS backend and docs.

Currently, only macOS-related proxy enablement and retrieval have been added.

Usage

use robius_proxy::{BypassList, ProxyEndpoint, ProxyManager, ProxyMode, ProxySettings, ProxyState};

let manager = ProxyManager::new()?;
let current = manager.current()?;

println!("Current mode: {:?}", current.mode);

// Get proxy configuration.
match &state.mode {
        ProxyMode::Direct => println!("  mode: Direct (no proxy)"),
        ProxyMode::Manual(settings) => {
            println!("  mode: Manual");
            if let Some(http) = &settings.http {
                println!("    http: {}:{}", http.host, http.port);
            }
            if let Some(https) = &settings.https {
                println!("    https: {}:{}", https.host, https.port);
            }
            if let Some(socks) = &settings.socks {
                println!("    socks: {}:{}", socks.host, socks.port);
            }
            if settings.bypass.entries.is_empty() {
                println!("    bypass: (none)");
            } else {
                println!("    bypass:");
                for entry in &settings.bypass.entries {
                    println!("      - {entry}");
                }
            }
        }
        ProxyMode::AutoConfigUrl { url, bypass } => {
            println!("  mode: PAC url");
            println!("    url: {url}");
            if bypass.entries.is_empty() {
                println!("    bypass: (none)");
            } else {
                println!("    bypass:");
                for entry in &bypass.entries {
                    println!("      - {entry}");
                }
            }
        }
        ProxyMode::AutoDiscovery { bypass } => {
            println!("  mode: Auto-discovery (WPAD)");
            if bypass.entries.is_empty() {
                println!("    bypass: (none)");
            } else {
                println!("    bypass:");
                for entry in &bypass.entries {
                    println!("      - {entry}");
                }
            }
        }
    }

// Apply proxy configuration.
let state = ProxyState::manual(ProxySettings {
    http: Some(ProxyEndpoint::new("proxy.local", 8080)),
    https: None,
    socks: None,
    bypass: BypassList::new(vec!["localhost".into(), "127.0.0.1".into()]),
});

manager.apply(state)?;

[tyreseluo]

Hi! @kevinaboos the proxy crate for macOS proxy retrieval is now complete. Users can now obtain the currently applied proxy information on macOS.

By enhancing the proxy crate to support proxy requests for cross-platform applications from users in the China region.

For instance, after packaging and distributing Robrix, we discovered that users in China cannot connect to the matrix.org network. Although the system applies a proxy, the running Robrix instance operates in a sandboxed environment and cannot access the proxy configuration. Therefore, we should provide such a proxy crate—one that is at least useful and uncomplicated.

I will submit PRs for the proxy crate on each platform separately and gradually improve and finish this proxy crate.

[kevinaboos]

I don't mind adding this crate, but I do have some questions first because I'm not super familiar with system proxies.

1. Do you plan to add support for other platforms as well? Are proxies available on all desktop and mobile platforms, or just desktop, or fewer?
2. Why does each individual application need to be aware of a system proxy? I thought the point was that you establish a proxy connection and then the underlying OS routes all network traffic through that proxy. It seems like the application should not have to be concerned with that level of network knowledge, and I generally do not want to overcomplicate an app like Robrix with this extra complexity. It doesn't really make sense that a system sandbox for an app would allow that app to bypass the system-applied proxy.
3. If this is a macOS-specific issue, perhaps we just need to change some packaging details about Robrix such that it is allowed to access the system-level proxy. Is that possible?