snarkos_node_tcp/protocols/
on_connect.rs

1// Copyright (c) 2019-2026 Provable Inc.
2// This file is part of the snarkOS library.
3
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at:
7
8// http://www.apache.org/licenses/LICENSE-2.0
9
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15
16use std::net::SocketAddr;
17
18use tokio::sync::{mpsc, oneshot};
19use tracing::*;
20
21#[cfg(doc)]
22use crate::{
23    Connection,
24    protocols::{Reading, Writing},
25};
26use crate::{
27    P2P,
28    connections::DisconnectOrigin,
29    protocols::{DisconnectOnDrop, ProtocolHandler},
30};
31
32/// Can be used to automatically perform some initial actions once the connection with a peer is
33/// fully established.
34#[async_trait::async_trait]
35pub trait OnConnect: P2P
36where
37    Self: Clone + Send + Sync + 'static,
38{
39    /// Attaches the behavior specified in [`OnConnect::on_connect`] right after every successful
40    /// handshake.
41    async fn enable_on_connect(&self) {
42        let (from_node_sender, mut from_node_receiver) = mpsc::channel::<(
43            SocketAddr,
44            oneshot::Sender<tokio::task::JoinHandle<()>>,
45        )>(self.tcp().config().max_connections as usize);
46
47        // use a channel to know when the on_connect task is ready
48        let (tx, rx) = oneshot::channel::<()>();
49
50        // spawn a background task dedicated to executing the desired post-handshake actions
51        let self_clone = self.clone();
52        let on_connect_task = tokio::spawn(async move {
53            trace!(parent: self_clone.tcp().span(), "spawned the OnConnect handler task");
54            if tx.send(()).is_err() {
55                error!(parent: self_clone.tcp().span(), "OnConnect handler creation interrupted! shutting down the node");
56                self_clone.tcp().shut_down().await;
57                return;
58            }
59
60            while let Some((addr, notifier)) = from_node_receiver.recv().await {
61                let self_clone2 = self_clone.clone();
62                let handle = tokio::spawn(async move {
63                    // disconnect automatically if the OnConnect impl panics
64                    let mut conn_cleanup =
65                        DisconnectOnDrop::new(self_clone2.tcp().clone(), addr, DisconnectOrigin::OnConnectAbort);
66                    // perform the specified initial actions
67                    self_clone2.on_connect(addr).await;
68                    // if there was no panic, do not disconnect - this "defuses" the auto-cleanup
69                    conn_cleanup.node.take();
70                });
71                // notify the node that the initial actions have concluded
72                let _ = notifier.send(handle); // can't really fail
73            }
74        });
75        let _ = rx.await;
76        self.tcp().tasks.lock().push(on_connect_task);
77
78        // register the OnConnect handler with the Node
79        let hdl = Box::new(ProtocolHandler(from_node_sender));
80        assert!(self.tcp().protocols.on_connect.set(hdl).is_ok(), "the OnConnect protocol was enabled more than once!");
81    }
82
83    /// Any initial actions to be executed after the handshake is concluded; in order to be able to
84    /// communicate with the peer in the usual manner (i.e. via [`Writing`]), only its [`SocketAddr`]
85    /// (as opposed to the related [`Connection`] object) is provided as an argument.
86    async fn on_connect(&self, addr: SocketAddr);
87}
snarkos_node_tcp/protocols/on_connect.rs

snarkos_node_tcp/protocols/
on_connect.rs
