Feature Request: Add Wi-Fi callback example

[owenthewizard]

I'm trying to use WifiDriver::set_callbacks but I'm not successful. I think an example would be helpful.
Context: I'm trying to implement this in idiomatic Rust: https://github.com/dokmic/eth2wlan/blob/master/main/main.c

[owenthewizard]

This is my non-working code. It seems the callbacks never get called.

    // Wrap your drivers in Arc<Mutex<_>> to allow shared mutable access.
    let eth_mutex = Arc::new(Mutex::new(eth));
    let wifi_mutex = Arc::new(Mutex::new(wifi));

    // Clone the Arcs for use in closures
    let eth_mutex_clone = eth_mutex.clone();
    let wifi_mutex_clone = wifi_mutex.clone();

    // Forward from eth to wifi
    eth_mutex
        .lock()
        .unwrap()
        .driver_mut()
        .set_rx_callback(move |frame| {
            info!("Forwarding frame from eth to wifi...");
            if let Err(e) = wifi_mutex_clone
                .lock()
                .unwrap()
                .send(WifiDeviceId::Sta, frame)
            {
                error!("Failed to forward eth frame to wifi: {}", e);
            }
        })?;

    // Forward from wifi to eth
    wifi_mutex.lock().unwrap().set_callbacks(move |_, frame| {
        info!("Forwarding frame from wifi to eth...");
        if let Err(e) = eth_mutex_clone.lock().unwrap().driver_mut().send(frame) {
            error!("Failed to forward wifi frame to eth: {}", e);
        }
        Ok(())
    }, |_, _, _| {})?;

[owenthewizard]

Hm, when callbacks are set the interfaces are stopped.

[owenthewizard]

The C functions are noted to be internal to ESP and not recommended for customers to use. Regardless, they seem to function. Better documentation is needed.

[Vollbrecht]

I wrote a esp sniffer using the promiscuous mode and streamed the data via callback's as PCAP packets back over uart directly into wireshark on a host machine.

I am telling you this because you need to be really careful using the callbacks. By that i am talking about that the callbacks are working inside the wifi thread with a high system priority. You should not do any blocking there as you will stale the complete wifi driver. Best is to just grab the data/info you want and just push it out. Don't use Mutex's that maybe can deadlock you or are to slow. Just stream out the data via a mpsc channel or something.

At that time i didn't use this callbacks but the unsafe esp-idf-sys methods directly but it should be similar-

[owenthewizard]

Another development, the callback functions seem to be broken, there's a workaround in https://github.com/makischu/ESP_eth2wifi.

[ivmarkov]

The original purpose of these callbacks was not to do what you are trying to do (i.e., have the callbacks and the netif stack on top running together somehow), but to rather allow users to have a driver (eth and/or wifi) that operates purely on L2 level, and then potentially layer a user-provided IP stack layer on top of the callbacks. Say - the pure Rust smoltcp one.

With that said, I have not tried whether that would work, as I don't yet have that usecase, but I don't see why it wouldn't given that the ESP IDF netif layer uses these very same callbacks.

With that said, your use case is different, so you probably need to inspect or even patch the netif stack so that callbacks or their equivalents are usable even when the netif stack continues to run on top.

[owenthewizard]

@ivmarkov Can I just patch the esp-idf sources in .embuild or is there a "proper" way to do it that I can integrate into build.rs?

[ivmarkov]

Just use your own esp idf git fork. You can pass the git url and/or the path to your local ESP IDF to esp-idf-sys.

[owenthewizard]

You can pass the git url and/or the path to your local ESP IDF to esp-idf-sys.

Is there a doc or somewhere I can read more directions for this? Sorry if I'm dense, this is my first endeavor into Rust on ESP32 (and the ESP32 itself for that matter).

For anyone reading along, it looks like there's an up to date example here (sta2eth): https://github.com/espressif/esp-idf/tree/master/examples/network
I'm going to try it out.

[ivmarkov]

https://github.com/esp-rs/esp-idf-sys/blob/master/BUILD-OPTIONS.md