rns_net/interface/

tcp_server.rs

//! TCP server interface with HDLC framing.
//!
//! Accepts client connections and spawns per-client reader threads.
//! Each client gets a dynamically allocated InterfaceId.
//! Matches Python `TCPServerInterface` from `TCPInterface.py`.

use std::io::{self, Read, Write};
use std::net::{TcpListener, TcpStream};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
use std::thread;

use rns_core::constants;
use rns_core::transport::types::{InterfaceId, InterfaceInfo};

use crate::event::{Event, EventSender};
use crate::hdlc;
use crate::interface::Writer;

/// Configuration for a TCP server interface.
#[derive(Debug, Clone)]
pub struct TcpServerConfig {
    pub name: String,
    pub listen_ip: String,
    pub listen_port: u16,
    pub interface_id: InterfaceId,
}

impl Default for TcpServerConfig {
    fn default() -> Self {
        TcpServerConfig {
            name: String::new(),
            listen_ip: "0.0.0.0".into(),
            listen_port: 4242,
            interface_id: InterfaceId(0),
        }
    }
}

/// Writer that sends HDLC-framed data over a TCP stream.
struct TcpServerWriter {
    stream: TcpStream,
}

impl Writer for TcpServerWriter {
    fn send_frame(&mut self, data: &[u8]) -> io::Result<()> {
        self.stream.write_all(&hdlc::frame(data))
    }
}

/// Start a TCP server. Spawns a listener thread that accepts connections
/// and per-client reader threads. Returns immediately.
///
/// `next_id` is shared with the node for allocating unique InterfaceIds
/// for each connected client.
pub fn start(
    config: TcpServerConfig,
    tx: EventSender,
    next_id: Arc<AtomicU64>,
) -> io::Result<()> {
    let addr = format!("{}:{}", config.listen_ip, config.listen_port);
    let listener = TcpListener::bind(&addr)?;

    log::info!("[{}] TCP server listening on {}", config.name, addr);

    let name = config.name.clone();
    thread::Builder::new()
        .name(format!("tcp-server-{}", config.interface_id.0))
        .spawn(move || {
            listener_loop(listener, name, tx, next_id);
        })?;

    Ok(())
}

/// Listener thread: accepts connections and spawns reader threads.
fn listener_loop(
    listener: TcpListener,
    name: String,
    tx: EventSender,
    next_id: Arc<AtomicU64>,
) {
    for stream_result in listener.incoming() {
        let stream = match stream_result {
            Ok(s) => s,
            Err(e) => {
                log::warn!("[{}] accept failed: {}", name, e);
                continue;
            }
        };

        let client_id = InterfaceId(next_id.fetch_add(1, Ordering::Relaxed));
        let peer_addr = stream.peer_addr().ok();

        log::info!(
            "[{}] client connected: {:?} → id {}",
            name,
            peer_addr,
            client_id.0
        );

        // Set TCP_NODELAY on the client socket
        if let Err(e) = stream.set_nodelay(true) {
            log::warn!("[{}] set_nodelay failed: {}", name, e);
        }

        // Clone stream for writer
        let writer_stream = match stream.try_clone() {
            Ok(s) => s,
            Err(e) => {
                log::warn!("[{}] failed to clone stream: {}", name, e);
                continue;
            }
        };

        let writer: Box<dyn Writer> = Box::new(TcpServerWriter { stream: writer_stream });

        let info = InterfaceInfo {
            id: client_id,
            name: format!("TCPServerInterface/Client-{}", client_id.0),
            mode: constants::MODE_FULL,
            out_capable: true,
            in_capable: true,
            bitrate: None,
            announce_rate_target: None,
            announce_rate_grace: 0,
            announce_rate_penalty: 0.0,
            announce_cap: constants::ANNOUNCE_CAP,
            is_local_client: false,
            wants_tunnel: false,
            tunnel_id: None,
        };

        // Send InterfaceUp with InterfaceInfo for dynamic registration
        if tx
            .send(Event::InterfaceUp(client_id, Some(writer), Some(info)))
            .is_err()
        {
            // Driver shut down
            return;
        }

        // Spawn reader thread for this client
        let client_tx = tx.clone();
        let client_name = name.clone();
        thread::Builder::new()
            .name(format!("tcp-server-reader-{}", client_id.0))
            .spawn(move || {
                client_reader_loop(stream, client_id, client_name, client_tx);
            })
            .ok();
    }
}

/// Per-client reader thread: reads HDLC frames, sends to driver.
fn client_reader_loop(
    mut stream: TcpStream,
    id: InterfaceId,
    name: String,
    tx: EventSender,
) {
    let mut decoder = hdlc::Decoder::new();
    let mut buf = [0u8; 4096];

    loop {
        match stream.read(&mut buf) {
            Ok(0) => {
                log::info!("[{}] client {} disconnected", name, id.0);
                let _ = tx.send(Event::InterfaceDown(id));
                return;
            }
            Ok(n) => {
                for frame in decoder.feed(&buf[..n]) {
                    if tx
                        .send(Event::Frame {
                            interface_id: id,
                            data: frame,
                        })
                        .is_err()
                    {
                        // Driver shut down
                        return;
                    }
                }
            }
            Err(e) => {
                log::warn!("[{}] client {} read error: {}", name, id.0, e);
                let _ = tx.send(Event::InterfaceDown(id));
                return;
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::net::TcpStream;
    use std::sync::mpsc;
    use std::time::Duration;

    fn find_free_port() -> u16 {
        TcpListener::bind("127.0.0.1:0")
            .unwrap()
            .local_addr()
            .unwrap()
            .port()
    }

    #[test]
    fn accept_connection() {
        let port = find_free_port();
        let (tx, rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(1000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(1),
        };

        start(config, tx, next_id).unwrap();

        // Give server time to start listening
        thread::sleep(Duration::from_millis(50));

        // Connect a client
        let _client = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();

        // Should receive InterfaceUp with InterfaceInfo (dynamic)
        let event = rx.recv_timeout(Duration::from_secs(2)).unwrap();
        match event {
            Event::InterfaceUp(id, writer, info) => {
                assert_eq!(id, InterfaceId(1000));
                assert!(writer.is_some());
                assert!(info.is_some());
            }
            other => panic!("expected InterfaceUp, got {:?}", other),
        }
    }

    #[test]
    fn receive_frame_from_client() {
        let port = find_free_port();
        let (tx, rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(2000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(2),
        };

        start(config, tx, next_id).unwrap();
        thread::sleep(Duration::from_millis(50));

        let mut client = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();

        // Drain InterfaceUp
        let _ = rx.recv_timeout(Duration::from_secs(1)).unwrap();

        // Send an HDLC frame (>= 19 bytes)
        let payload: Vec<u8> = (0..32).collect();
        let framed = hdlc::frame(&payload);
        client.write_all(&framed).unwrap();

        // Should receive Frame event
        let event = rx.recv_timeout(Duration::from_secs(2)).unwrap();
        match event {
            Event::Frame { interface_id, data } => {
                assert_eq!(interface_id, InterfaceId(2000));
                assert_eq!(data, payload);
            }
            other => panic!("expected Frame, got {:?}", other),
        }
    }

    #[test]
    fn send_frame_to_client() {
        let port = find_free_port();
        let (tx, rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(3000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(3),
        };

        start(config, tx, next_id).unwrap();
        thread::sleep(Duration::from_millis(50));

        let mut client = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();
        client.set_read_timeout(Some(Duration::from_secs(2))).unwrap();

        // Get the writer from InterfaceUp
        let event = rx.recv_timeout(Duration::from_secs(1)).unwrap();
        let mut writer = match event {
            Event::InterfaceUp(_, Some(w), _) => w,
            other => panic!("expected InterfaceUp with writer, got {:?}", other),
        };

        // Send a frame via writer
        let payload: Vec<u8> = (0..24).collect();
        writer.send_frame(&payload).unwrap();

        // Read from client side
        let mut buf = [0u8; 256];
        let n = client.read(&mut buf).unwrap();
        let expected = hdlc::frame(&payload);
        assert_eq!(&buf[..n], &expected[..]);
    }

    #[test]
    fn multiple_clients() {
        let port = find_free_port();
        let (tx, rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(4000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(4),
        };

        start(config, tx, next_id).unwrap();
        thread::sleep(Duration::from_millis(50));

        // Connect two clients
        let _client1 = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();
        let _client2 = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();

        // Collect InterfaceUp events
        let mut ids = Vec::new();
        for _ in 0..2 {
            let event = rx.recv_timeout(Duration::from_secs(2)).unwrap();
            match event {
                Event::InterfaceUp(id, _, _) => ids.push(id),
                other => panic!("expected InterfaceUp, got {:?}", other),
            }
        }

        // Should have unique IDs
        assert_eq!(ids.len(), 2);
        assert_ne!(ids[0], ids[1]);
    }

    #[test]
    fn client_disconnect() {
        let port = find_free_port();
        let (tx, rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(5000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(5),
        };

        start(config, tx, next_id).unwrap();
        thread::sleep(Duration::from_millis(50));

        let client = TcpStream::connect(format!("127.0.0.1:{}", port)).unwrap();

        // Drain InterfaceUp
        let _ = rx.recv_timeout(Duration::from_secs(1)).unwrap();

        // Disconnect
        drop(client);

        // Should receive InterfaceDown
        let event = rx.recv_timeout(Duration::from_secs(2)).unwrap();
        assert!(
            matches!(event, Event::InterfaceDown(InterfaceId(5000))),
            "expected InterfaceDown(5000), got {:?}",
            event
        );
    }

    #[test]
    fn server_bind_port() {
        let port = find_free_port();
        let (tx, _rx) = mpsc::channel();
        let next_id = Arc::new(AtomicU64::new(6000));

        let config = TcpServerConfig {
            name: "test-server".into(),
            listen_ip: "127.0.0.1".into(),
            listen_port: port,
            interface_id: InterfaceId(6),
        };

        // Should not error
        start(config, tx, next_id).unwrap();
    }
}