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use std::{future::Future, io, time::Duration};
use tokio::{
io::{AsyncRead, AsyncWrite, split},
net::TcpStream,
sync::{mpsc, oneshot},
time::timeout,
};
use tracing::*;
use crate::{
Connection, Pea2Pea,
node::NodeTask,
protocols::{ProtocolHandler, ReturnableConnection},
};
/// Can be used to specify and enable network handshakes. Upon establishing a connection, both sides will
/// need to adhere to the specified handshake rules in order to finalize the connection and be able to send
/// or receive any messages.
pub trait Handshake: Pea2Pea
where
Self: Clone + Send + Sync + 'static,
{
/// The maximum time allowed for a connection to perform a handshake before it is rejected.
const TIMEOUT_MS: u64 = 3_000;
/// Prepares the node to perform specified network handshakes.
fn enable_handshake(&self) -> impl Future<Output = ()> + Send {
async {
let (from_node_sender, mut from_node_receiver) =
mpsc::unbounded_channel::<ReturnableConnection>();
// use a channel to know when the handshake task is ready
let (tx, rx) = oneshot::channel();
// spawn a background task dedicated to handling the handshakes
let self_clone = self.clone();
let handshake_task = tokio::spawn(async move {
trace!(parent: self_clone.node().span(), "spawned the Handshake handler task");
if tx.send(()).is_err() {
error!(parent: self_clone.node().span(), "Handshake handler creation interrupted! shutting down the node");
self_clone.node().shut_down().await;
return;
}
while let Some((conn, result_sender)) = from_node_receiver.recv().await {
let addr = conn.addr();
let node = self_clone.clone();
tokio::spawn(async move {
debug!(parent: node.node().span(), "shaking hands with {addr} as the {:?}", !conn.side());
let result = timeout(
Duration::from_millis(Self::TIMEOUT_MS),
node.perform_handshake(conn),
)
.await;
let ret = match result {
Ok(Ok(conn)) => {
debug!(parent: node.node().span(), "successfully handshaken with {addr}");
Ok(conn)
}
Ok(Err(e)) => {
error!(parent: node.node().span(), "handshake with {addr} failed: {e}");
Err(e)
}
Err(_) => {
error!(parent: node.node().span(), "handshake with {addr} timed out");
Err(io::ErrorKind::TimedOut.into())
}
};
// return the Connection to the Node, resuming Node::adapt_stream
if result_sender.send(ret).is_err() {
error!(parent: node.node().span(), "couldn't return a Connection with {addr} from the Handshake handler");
}
});
}
});
let _ = rx.await;
self.node()
.tasks
.lock()
.insert(NodeTask::Handshake, handshake_task);
// register the Handshake handler with the Node
let hdl = ProtocolHandler(from_node_sender);
assert!(
self.node().protocols.handshake.set(hdl).is_ok(),
"the Handshake protocol was enabled more than once!"
);
}
}
/// Performs the handshake; temporarily assumes control of the [`Connection`] and returns it if the handshake is
/// successful.
fn perform_handshake(
&self,
conn: Connection,
) -> impl Future<Output = io::Result<Connection>> + Send;
/// Borrows the full connection stream to be used in the implementation of [`Handshake::perform_handshake`].
fn borrow_stream<'a>(&self, conn: &'a mut Connection) -> &'a mut TcpStream {
conn.stream.as_mut().unwrap()
}
/// Assumes full control of a connection's stream in the implementation of [`Handshake::perform_handshake`], by
/// the end of which it *must* be followed by [`Handshake::return_stream`].
fn take_stream(&self, conn: &mut Connection) -> TcpStream {
conn.stream.take().unwrap()
}
/// This method only needs to be called if [`Handshake::take_stream`] had been called before; it is used to
/// return a (potentially modified) stream back to the applicable connection.
fn return_stream<T: AsyncRead + AsyncWrite + Send + Sync + 'static>(
&self,
conn: &mut Connection,
stream: T,
) {
let (reader, writer) = split(stream);
conn.reader = Some(Box::new(reader));
conn.writer = Some(Box::new(writer));
}
}