Merge pull request #2973 from valentinewallace/2024-03-om-mailbox
[rust-lightning] / lightning / src / onion_message / messenger.rs
index 2f8f3798cb001704e8bdc59c7046cb98b6339fe4..97fcbfd94afa5e4c3ff7c866cd637392050e5cc3 100644 (file)
@@ -176,6 +176,8 @@ where
        message_router: MR,
        offers_handler: OMH,
        custom_handler: CMH,
+       intercept_messages_for_offline_peers: bool,
+       pending_events: Mutex<Vec<Event>>,
 }
 
 /// [`OnionMessage`]s buffered to be sent.
@@ -841,6 +843,48 @@ where
        pub fn new(
                entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL, message_router: MR,
                offers_handler: OMH, custom_handler: CMH
+       ) -> Self {
+               Self::new_inner(
+                       entropy_source, node_signer, logger, node_id_lookup, message_router,
+                       offers_handler, custom_handler, false
+               )
+       }
+
+       /// Similar to [`Self::new`], but rather than dropping onion messages that are
+       /// intended to be forwarded to offline peers, we will intercept them for
+       /// later forwarding.
+       ///
+       /// Interception flow:
+       /// 1. If an onion message for an offline peer is received, `OnionMessenger` will
+       ///    generate an [`Event::OnionMessageIntercepted`]. Event handlers can
+       ///    then choose to persist this onion message for later forwarding, or drop
+       ///    it.
+       /// 2. When the offline peer later comes back online, `OnionMessenger` will
+       ///    generate an [`Event::OnionMessagePeerConnected`]. Event handlers will
+       ///    then fetch all previously intercepted onion messages for this peer.
+       /// 3. Once the stored onion messages are fetched, they can finally be
+       ///    forwarded to the now-online peer via [`Self::forward_onion_message`].
+       ///
+       /// # Note
+       ///
+       /// LDK will not rate limit how many [`Event::OnionMessageIntercepted`]s
+       /// are generated, so it is the caller's responsibility to limit how many
+       /// onion messages are persisted and only persist onion messages for relevant
+       /// peers.
+       pub fn new_with_offline_peer_interception(
+               entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL,
+               message_router: MR, offers_handler: OMH, custom_handler: CMH
+       ) -> Self {
+               Self::new_inner(
+                       entropy_source, node_signer, logger, node_id_lookup, message_router,
+                       offers_handler, custom_handler, true
+               )
+       }
+
+       fn new_inner(
+               entropy_source: ES, node_signer: NS, logger: L, node_id_lookup: NL,
+               message_router: MR, offers_handler: OMH, custom_handler: CMH,
+               intercept_messages_for_offline_peers: bool
        ) -> Self {
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
@@ -854,6 +898,8 @@ where
                        message_router,
                        offers_handler,
                        custom_handler,
+                       intercept_messages_for_offline_peers,
+                       pending_events: Mutex::new(Vec::new()),
                }
        }
 
@@ -962,6 +1008,27 @@ where
                }
        }
 
+       /// Forwards an [`OnionMessage`] to `peer_node_id`. Useful if we initialized
+       /// the [`OnionMessenger`] with [`Self::new_with_offline_peer_interception`]
+       /// and want to forward a previously intercepted onion message to a peer that
+       /// has just come online.
+       pub fn forward_onion_message(
+               &self, message: OnionMessage, peer_node_id: &PublicKey
+       ) -> Result<(), SendError> {
+               let mut message_recipients = self.message_recipients.lock().unwrap();
+               if outbound_buffer_full(&peer_node_id, &message_recipients) {
+                       return Err(SendError::BufferFull);
+               }
+
+               match message_recipients.entry(*peer_node_id) {
+                       hash_map::Entry::Occupied(mut e) if e.get().is_connected() => {
+                               e.get_mut().enqueue_message(message);
+                               Ok(())
+                       },
+                       _ => Err(SendError::InvalidFirstHop(*peer_node_id))
+               }
+       }
+
        #[cfg(any(test, feature = "_test_utils"))]
        pub fn send_onion_message_using_path<T: OnionMessageContents>(
                &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
@@ -1004,6 +1071,20 @@ where
                }
                msgs
        }
+
+       fn enqueue_event(&self, event: Event) {
+               const MAX_EVENTS_BUFFER_SIZE: usize = (1 << 10) * 256;
+               let mut pending_events = self.pending_events.lock().unwrap();
+               let total_buffered_bytes: usize = pending_events
+                       .iter()
+                       .map(|ev| ev.serialized_length())
+                       .sum();
+               if total_buffered_bytes >= MAX_EVENTS_BUFFER_SIZE {
+                       log_trace!(self.logger, "Dropping event {:?}: buffer full", event);
+                       return
+               }
+               pending_events.push(event);
+       }
 }
 
 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageRecipient>) -> bool {
@@ -1048,6 +1129,11 @@ where
                                }
                        }
                }
+               let mut events = Vec::new();
+               core::mem::swap(&mut *self.pending_events.lock().unwrap(), &mut events);
+               for ev in events {
+                       handler.handle_event(ev);
+               }
        }
 }
 
@@ -1121,6 +1207,13 @@ where
                                                e.get_mut().enqueue_message(onion_message);
                                                log_trace!(logger, "Forwarding an onion message to peer {}", next_node_id);
                                        },
+                                       _ if self.intercept_messages_for_offline_peers => {
+                                               self.enqueue_event(
+                                                       Event::OnionMessageIntercepted {
+                                                               peer_node_id: next_node_id, message: onion_message
+                                                       }
+                                               );
+                                       },
                                        _ => {
                                                log_trace!(
                                                        logger,
@@ -1142,6 +1235,11 @@ where
                                .entry(*their_node_id)
                                .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()))
                                .mark_connected();
+                       if self.intercept_messages_for_offline_peers {
+                               self.enqueue_event(
+                                       Event::OnionMessagePeerConnected { peer_node_id: *their_node_id }
+                               );
+                       }
                } else {
                        self.message_recipients.lock().unwrap().remove(their_node_id);
                }