Address PR feedback

rust/src/cli/l2cap/client_bridge.rs

@@ -0,0 +1,191 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// L2CAP CoC client bridge: connects to a BLE device, then waits for an inbound
+/// TCP connection on a specified port number. When a TCP client connects, an
+/// L2CAP CoC channel connection to the BLE device is established, and the data
+/// is bridged in both directions, with flow control.
+/// When the TCP connection is closed by the client, the L2CAP CoC channel is
+/// disconnected, but the connection to the BLE device remains, ready for a new
+/// TCP client to connect.
+/// When the L2CAP CoC channel is closed, the TCP connection is closed as well.
+use crate::cli::l2cap::{
+    proxy_l2cap_rx_to_tcp_tx, proxy_tcp_rx_to_l2cap_tx, run_future_with_current_task_locals,
+    BridgeData,
+};
+use bumble::wrapper::{
+    device::{Connection, Device},
+    hci::HciConstant,
+};
+use futures::executor::block_on;
+use owo_colors::OwoColorize;
+use pyo3::{PyResult, Python};
+use std::{net::SocketAddr, sync::Arc};
+use tokio::{
+    join,
+    net::{TcpListener, TcpStream},
+    sync::{mpsc, Mutex},
+};
+
+pub struct Args {
+    pub psm: u16,
+    pub max_credits: Option<u16>,
+    pub mtu: Option<u16>,
+    pub mps: Option<u16>,
+    pub bluetooth_address: String,
+    pub tcp_host: String,
+    pub tcp_port: u16,
+}
+
+pub async fn start(args: &Args, device: &mut Device) -> PyResult<()> {
+    println!(
+        "{}",
+        format!("### Connecting to {}...", args.bluetooth_address).yellow()
+    );
+    let mut ble_connection = device.connect(&args.bluetooth_address).await?;
+    ble_connection.on_disconnection(|_py, reason| {
+        let disconnection_info = match HciConstant::error_name(reason) {
+            Ok(info_string) => info_string,
+            Err(py_err) => format!("failed to get disconnection error name ({})", py_err),
+        };
+        println!(
+            "{} {}",
+            "@@@ Bluetooth disconnection: ".red(),
+            disconnection_info,
+        );
+        Ok(())
+    })?;
+
+    // Start the TCP server.
+    let listener = TcpListener::bind(format!("{}:{}", args.tcp_host, args.tcp_port))
+        .await
+        .expect("failed to bind tcp to address");
+    println!(
+        "{}",
+        format!(
+            "### Listening for TCP connections on port {}",
+            args.tcp_port
+        )
+        .magenta()
+    );
+
+    let psm = args.psm;
+    let max_credits = args.max_credits;
+    let mtu = args.mtu;
+    let mps = args.mps;
+    let ble_connection = Arc::new(Mutex::new(ble_connection));
+    // Ensure Python event loop is available to l2cap `disconnect`
+    let _ = run_future_with_current_task_locals(async move {
+        while let Ok((tcp_stream, addr)) = listener.accept().await {
+            let ble_connection = ble_connection.clone();
+            let _ = run_future_with_current_task_locals(proxy_data_between_tcp_and_l2cap(
+                ble_connection,
+                tcp_stream,
+                addr,
+                psm,
+                max_credits,
+                mtu,
+                mps,
+            ));
+        }
+        Ok(())
+    });
+    Ok(())
+}
+
+async fn proxy_data_between_tcp_and_l2cap(
+    ble_connection: Arc<Mutex<Connection>>,
+    tcp_stream: TcpStream,
+    addr: SocketAddr,
+    psm: u16,
+    max_credits: Option<u16>,
+    mtu: Option<u16>,
+    mps: Option<u16>,
+) -> PyResult<()> {
+    println!("{}", format!("<<< TCP connection from {}", addr).magenta());
+    println!(
+        "{}",
+        format!(">>> Opening L2CAP channel on PSM = {}", psm).yellow()
+    );
+
+    let mut l2cap_channel = match ble_connection
+        .lock()
+        .await
+        .open_l2cap_channel(psm, max_credits, mtu, mps)
+        .await
+    {
+        Ok(channel) => channel,
+        Err(e) => {
+            println!("{}", format!("!!! Connection failed: {e}").red());
+            // TCP stream will get dropped after returning, automatically shutting it down.
+            return Err(e);
+        }
+    };
+    let channel_info = l2cap_channel
+        .debug_string()
+        .unwrap_or_else(|e| format!("failed to get l2cap channel info ({e})"));
+
+    println!("{}{}", "*** L2CAP channel: ".cyan(), channel_info);
+
+    let (l2cap_to_tcp_tx, l2cap_to_tcp_rx) = mpsc::channel::<BridgeData>(10);
+
+    // Set l2cap callback (`set_sink`) for when data is received.
+    let l2cap_to_tcp_tx_clone = l2cap_to_tcp_tx.clone();
+    l2cap_channel
+        .set_sink(move |_py, sdu| {
+            block_on(l2cap_to_tcp_tx_clone.send(BridgeData::Data(sdu.into())))
+                .expect("failed to channel data to tcp");
+            Ok(())
+        })
+        .expect("failed to set sink for l2cap connection");
+
+    // Set l2cap callback for when the channel is closed.
+    l2cap_channel
+        .on_close(move |_py| {
+            println!("{}", "*** L2CAP channel closed".red());
+            block_on(l2cap_to_tcp_tx.send(BridgeData::CloseSignal))
+                .expect("failed to channel close signal to tcp");
+            Ok(())
+        })
+        .expect("failed to set on_close callback for l2cap channel");
+
+    let l2cap_channel = Arc::new(Mutex::new(Some(l2cap_channel)));
+    let (tcp_reader, tcp_writer) = tcp_stream.into_split();
+
+    // Do tcp stuff when something happens on the l2cap channel.
+    let handle_l2cap_data_future =
+        proxy_l2cap_rx_to_tcp_tx(l2cap_to_tcp_rx, tcp_writer, l2cap_channel.clone());
+
+    // Do l2cap stuff when something happens on tcp.
+    let handle_tcp_data_future = proxy_tcp_rx_to_l2cap_tx(tcp_reader, l2cap_channel.clone(), true);
+
+    let (handle_l2cap_result, handle_tcp_result) =
+        join!(handle_l2cap_data_future, handle_tcp_data_future);
+
+    if let Err(e) = handle_l2cap_result {
+        println!("!!! Error: {e}");
+    }
+
+    if let Err(e) = handle_tcp_result {
+        println!("!!! Error: {e}");
+    }
+
+    Python::with_gil(|_| {
+        // Must hold GIL at least once while/after dropping for Python heap object to ensure
+        // de-allocation.
+        drop(l2cap_channel);
+    });
+
+    Ok(())
+}