1  // Copyright (c) 2025 ADnet Contributors
  2  // This file is part of the adnet-core library.
  3  // Derived from snarkOS, originally by Provable Inc.
  4  
  5  // Licensed under the Apache License, Version 2.0 (the "License");
  6  // you may not use this file except in compliance with the License.
  7  // You may obtain a copy of the License at:
  8  
  9  // http://www.apache.org/licenses/LICENSE-2.0
 10  
 11  // Unless required by applicable law or agreed to in writing, software
 12  // distributed under the License is distributed on an "AS IS" BASIS,
 13  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  // See the License for the specific language governing permissions and
 15  // limitations under the License.
 16  
 17  #[cfg(doc)]
 18  use crate::{Config, protocols::Handshake};
 19  use crate::{
 20      ConnectionSide, P2P, Tcp,
 21      protocols::{ProtocolHandler, ReturnableConnection},
 22  };
 23  
 24  use async_trait::async_trait;
 25  use bytes::BytesMut;
 26  use futures_util::StreamExt;
 27  use std::{io, net::SocketAddr};
 28  use tokio::{
 29      io::AsyncRead,
 30      sync::{mpsc, oneshot},
 31  };
 32  use tokio_util::codec::{Decoder, FramedRead};
 33  use tracing::*;
 34  
 35  /// Can be used to specify and enable reading, i.e. receiving inbound messages. If the [`Handshake`]
 36  /// protocol is enabled too, it goes into force only after the handshake has been concluded.
 37  ///
 38  /// Each inbound message is isolated by the user-supplied [`Reading::Codec`], creating a [`Reading::Message`],
 39  /// which is immediately queued (with a [`Reading::MESSAGE_QUEUE_DEPTH`] limit) to be processed by
 40  /// [`Reading::process_message`]. The configured fatal IO errors result in an immediate disconnect
 41  /// (in order to e.g. avoid accidentally reading "borked" messages).
 42  #[async_trait]
 43  pub trait Reading: P2P
 44  where
 45      Self: Clone + Send + Sync + 'static,
 46  {
 47      /// The depth of per-connection queues used to process inbound messages; the greater it is, the more inbound
 48      /// messages the node can enqueue, but setting it to a large value can make the node more susceptible to DoS
 49      /// attacks.
 50      ///
 51      /// The default value is 1024.
 52      fn message_queue_depth(&self) -> usize {
 53          1024
 54      }
 55  
 56      /// The initial size of a per-connection buffer for reading inbound messages. Can be set to the maximum expected size
 57      /// of the inbound message in order to only allocate it once.
 58      ///
 59      /// The default value is 1024KiB.
 60      const INITIAL_BUFFER_SIZE: usize = 1024 * 1024;
 61  
 62      /// The final (deserialized) type of inbound messages.
 63      type Message: Send;
 64  
 65      /// The user-supplied [`Decoder`] used to interpret inbound messages.
 66      type Codec: Decoder<Item = Self::Message, Error = io::Error> + Send;
 67  
 68      /// Prepares the node to receive messages.
 69      async fn enable_reading(&self) {
 70          let (conn_sender, mut conn_receiver) = mpsc::unbounded_channel();
 71  
 72          // use a channel to know when the reading task is ready
 73          let (tx_reading, rx_reading) = oneshot::channel();
 74  
 75          // the main task spawning per-connection tasks reading messages from their streams
 76          let self_clone = self.clone();
 77          let reading_task = tokio::spawn(async move {
 78              trace!(parent: self_clone.tcp().span(), "spawned the Reading handler task");
 79              tx_reading.send(()).unwrap(); // safe; the channel was just opened
 80  
 81              // these objects are sent from `Tcp::adapt_stream`
 82              while let Some(returnable_conn) = conn_receiver.recv().await {
 83                  self_clone.handle_new_connection(returnable_conn).await;
 84              }
 85          });
 86          let _ = rx_reading.await;
 87          self.tcp().tasks.lock().push(reading_task);
 88  
 89          // register the Reading handler with the Tcp
 90          let hdl = Box::new(ProtocolHandler(conn_sender));
 91          assert!(
 92              self.tcp().protocols.reading.set(hdl).is_ok(),
 93              "the Reading protocol was enabled more than once!"
 94          );
 95      }
 96  
 97      /// Creates a [`Decoder`] used to interpret messages from the network.
 98      /// The `side` param indicates the connection side **from the node's perspective**.
 99      fn codec(&self, addr: SocketAddr, side: ConnectionSide) -> Self::Codec;
100  
101      /// Processes an inbound message. Can be used to update state, send replies etc.
102      async fn process_message(&self, source: SocketAddr, message: Self::Message) -> io::Result<()>;
103  }
104  
105  /// This trait is used to restrict access to methods that would otherwise be public in [`Reading`].
106  #[async_trait]
107  trait ReadingInternal: Reading {
108      /// Applies the [`Reading`] protocol to a single connection.
109      async fn handle_new_connection(&self, (conn, conn_returner): ReturnableConnection);
110  
111      /// Wraps the user-supplied [`Decoder`] ([`Reading::Codec`]) in another one used for message accounting.
112      fn map_codec<T: AsyncRead>(
113          &self,
114          framed: FramedRead<T, Self::Codec>,
115          addr: SocketAddr,
116      ) -> FramedRead<T, CountingCodec<Self::Codec>>;
117  }
118  
119  #[async_trait]
120  impl<R: Reading> ReadingInternal for R {
121      async fn handle_new_connection(&self, (mut conn, conn_returner): ReturnableConnection) {
122          let addr = conn.addr();
123          let codec = self.codec(addr, !conn.side());
124          let reader = conn.reader.take().expect("missing connection reader!");
125          let framed = FramedRead::new(reader, codec);
126          let mut framed = self.map_codec(framed, addr);
127  
128          // the connection will notify the reading task once it's fully ready
129          let (tx_conn_ready, rx_conn_ready) = oneshot::channel();
130          conn.readiness_notifier = Some(tx_conn_ready);
131  
132          if Self::INITIAL_BUFFER_SIZE != 0 {
133              framed.read_buffer_mut().reserve(Self::INITIAL_BUFFER_SIZE);
134          }
135  
136          let (inbound_message_sender, mut inbound_message_receiver) =
137              mpsc::channel(self.message_queue_depth());
138  
139          // use a channel to know when the processing task is ready
140          let (tx_processing, rx_processing) = oneshot::channel::<()>();
141  
142          // the task for processing parsed messages
143          let self_clone = self.clone();
144          let inbound_processing_task = tokio::spawn(Box::pin(async move {
145              let node = self_clone.tcp();
146              trace!(parent: node.span(), "spawned a task for processing messages from {addr}");
147              tx_processing.send(()).unwrap(); // safe; the channel was just opened
148  
149              while let Some(msg) = inbound_message_receiver.recv().await {
150                  if let Err(e) = self_clone.process_message(addr, msg).await {
151                      error!(parent: node.span(), "can't process a message from {addr}: {e}");
152                      node.known_peers().register_failure(addr.ip());
153                  }
154                  #[cfg(feature = "metrics")]
155                  metrics::decrement_gauge(metrics::tcp::TCP_TASKS, 1f64);
156              }
157          }));
158          let _ = rx_processing.await;
159          conn.tasks.push(inbound_processing_task);
160  
161          // use a channel to know when the reader task is ready
162          let (tx_reader, rx_reader) = oneshot::channel::<()>();
163  
164          // the task for reading messages from a stream
165          let node = self.tcp().clone();
166          let reader_task = tokio::spawn(Box::pin(async move {
167              trace!(parent: node.span(), "spawned a task for reading messages from {addr}");
168              tx_reader.send(()).unwrap(); // safe; the channel was just opened
169  
170              // postpone reads until the connection is fully established; if the process fails,
171              // this task gets aborted, so there is no need for a dedicated timeout
172              let _ = rx_conn_ready.await;
173  
174              while let Some(bytes) = framed.next().await {
175                  match bytes {
176                      Ok(msg) => {
177                          // send the message for further processing
178                          if let Err(e) = inbound_message_sender.try_send(msg) {
179                              error!(parent: node.span(), "can't process a message from {addr}: {e}");
180                              node.stats().register_failure();
181                              if matches!(e, mpsc::error::TrySendError::Closed(_)) {
182                                  break;
183                              }
184                          }
185                          #[cfg(feature = "metrics")]
186                          metrics::increment_gauge(metrics::tcp::TCP_TASKS, 1f64);
187                      }
188                      Err(e) => {
189                          error!(parent: node.span(), "can't read from {addr}: {e}");
190                          node.known_peers().register_failure(addr.ip());
191                          if node.config().fatal_io_errors.contains(&e.kind()) {
192                              break;
193                          }
194                      }
195                  }
196              }
197  
198              let _ = node.disconnect(addr).await;
199          }));
200          let _ = rx_reader.await;
201          conn.tasks.push(reader_task);
202  
203          // return the Connection to the Tcp, resuming Tcp::adapt_stream
204          if conn_returner.send(Ok(conn)).is_err() {
205              unreachable!("couldn't return a Connection to the Tcp");
206          }
207      }
208  
209      fn map_codec<T: AsyncRead>(
210          &self,
211          framed: FramedRead<T, Self::Codec>,
212          addr: SocketAddr,
213      ) -> FramedRead<T, CountingCodec<Self::Codec>> {
214          framed.map_decoder(|codec| CountingCodec {
215              codec,
216              node: self.tcp().clone(),
217              addr,
218              acc: 0,
219          })
220      }
221  }
222  
223  /// A wrapper [`Decoder`] that also counts the inbound messages.
224  struct CountingCodec<D: Decoder> {
225      codec: D,
226      node: Tcp,
227      addr: SocketAddr,
228      acc: usize,
229  }
230  
231  impl<D: Decoder> Decoder for CountingCodec<D> {
232      type Error = D::Error;
233      type Item = D::Item;
234  
235      fn decode(&mut self, src: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
236          let initial_buf_len = src.len();
237          let ret = self.codec.decode(src)?;
238          let final_buf_len = src.len();
239          let read_len = initial_buf_len - final_buf_len + self.acc;
240  
241          if read_len != 0 {
242              trace!(parent: self.node.span(), "read {}B from {}", read_len, self.addr);
243  
244              if ret.is_some() {
245                  self.acc = 0;
246                  self.node
247                      .known_peers()
248                      .register_received_message(self.addr.ip(), read_len);
249                  self.node.stats().register_received_message(read_len);
250              } else {
251                  self.acc = read_len;
252              }
253          }
254  
255          Ok(ret)
256      }
257  }