Drop OMs from disconnected peers in OnionMessenger

And refuse to forward OMs to disconnected peers

Author: valentinewallace

lightning/src/ln/features.rs

@@ -540,6 +540,17 @@ impl InitFeatures {
 	pub(crate) fn to_context<C: sealed::Context>(&self) -> Features<C> {
 		self.to_context_internal()
 	}
+
+	/// We do not yet advertise the onion messages feature bit, but we need to detect when peers
+	/// support it.
+	pub(crate) fn supports_onion_messages(&self) -> bool {
+		self.flags[4] & 0b11000000 != 0 // Feature bits 38/39
+	}
+
+	#[cfg(test)]
+	pub(crate) fn set_onion_messages_optional(&mut self) {
+		self.flags[4] |= 0b10000000
+	}
 }
 
 impl InvoiceFeatures {
@@ -767,7 +778,7 @@ impl<T: sealed::GossipQueries> Features<T> {
 
 impl<T: sealed::InitialRoutingSync> Features<T> {
 	// We are no longer setting initial_routing_sync now that gossip_queries
-	// is enabled. This feature is ignored by a peer when gossip_queries has 
+	// is enabled. This feature is ignored by a peer when gossip_queries has
 	// been negotiated.
 	#[cfg(test)]
 	pub(crate) fn clear_initial_routing_sync(&mut self) {

lightning/src/ln/msgs.rs

@@ -949,6 +949,12 @@ pub trait RoutingMessageHandler : MessageSendEventsProvider {
 pub trait OnionMessageHandler : OnionMessageProvider {
 	/// Handle an incoming onion_message message from the given peer.
 	fn handle_onion_message(&self, peer_node_id: &PublicKey, msg: &OnionMessage);
+	/// Called when a connection is established with a peer. Can be used to track which peers
+	/// advertise onion message support and are online.
+	fn peer_connected(&self, their_node_id: &PublicKey, init: &Init);
+	/// Indicates a connection to the peer failed/an existing connection was lost. Allows handlers to
+	/// drop and refuse to forward onion messages to this peer.
+	fn peer_disconnected(&self, their_node_id: &PublicKey, no_connection_possible: bool);
 }
 
 mod fuzzy_internal_msgs {

lightning/src/ln/peer_handler.rs

@@ -81,6 +81,8 @@ impl OnionMessageProvider for IgnoringMessageHandler {
 }
 impl OnionMessageHandler for IgnoringMessageHandler {
 	fn handle_onion_message(&self, _their_node_id: &PublicKey, _msg: &msgs::OnionMessage) {}
+	fn peer_connected(&self, _their_node_id: &PublicKey, _init: &msgs::Init) {}
+	fn peer_disconnected(&self, _their_node_id: &PublicKey, _no_connection_possible: bool) {}
 }
 impl Deref for IgnoringMessageHandler {
 	type Target = IgnoringMessageHandler;
@@ -1123,8 +1125,9 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 			}
 
 			self.message_handler.route_handler.peer_connected(&their_node_id, &msg);
-
 			self.message_handler.chan_handler.peer_connected(&their_node_id, &msg);
+			self.message_handler.onion_message_handler.peer_connected(&their_node_id, &msg);
+
 			peer_lock.their_features = Some(msg.features);
 			return Ok(None);
 		} else if peer_lock.their_features.is_none() {
@@ -1685,6 +1688,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 					}
 					descriptor.disconnect_socket();
 					self.message_handler.chan_handler.peer_disconnected(&node_id, false);
+					self.message_handler.onion_message_handler.peer_disconnected(&node_id, false);
 				}
 			}
 		}
@@ -1712,6 +1716,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 						log_pubkey!(node_id), if no_connection_possible { "no " } else { "" });
 					self.node_id_to_descriptor.lock().unwrap().remove(&node_id);
 					self.message_handler.chan_handler.peer_disconnected(&node_id, no_connection_possible);
+					self.message_handler.onion_message_handler.peer_disconnected(&node_id, no_connection_possible);
 				}
 			}
 		};
@@ -1732,6 +1737,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 			log_trace!(self.logger, "Disconnecting peer with id {} due to client request", node_id);
 			peers_lock.remove(&descriptor);
 			self.message_handler.chan_handler.peer_disconnected(&node_id, no_connection_possible);
+			self.message_handler.onion_message_handler.peer_disconnected(&node_id, no_connection_possible);
 			descriptor.disconnect_socket();
 		}
 	}
@@ -1747,6 +1753,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 			if let Some(node_id) = peer.lock().unwrap().their_node_id {
 				log_trace!(self.logger, "Disconnecting peer with id {} due to client request to disconnect all peers", node_id);
 				self.message_handler.chan_handler.peer_disconnected(&node_id, false);
+				self.message_handler.onion_message_handler.peer_disconnected(&node_id, false);
 			}
 			descriptor.disconnect_socket();
 		}
@@ -1837,6 +1844,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 							log_trace!(self.logger, "Disconnecting peer with id {} due to ping timeout", node_id);
 							self.node_id_to_descriptor.lock().unwrap().remove(&node_id);
 							self.message_handler.chan_handler.peer_disconnected(&node_id, false);
+							self.message_handler.onion_message_handler.peer_disconnected(&node_id, false);
 						}
 					}
 				}

lightning/src/onion_message/functional_tests.rs

@@ -10,13 +10,14 @@
 //! Onion message testing and test utilities live here.
 
 use chain::keysinterface::{KeysInterface, Recipient};
-use ln::msgs::OnionMessageHandler;
+use ln::features::InitFeatures;
+use ln::msgs::{self, OnionMessageHandler};
 use super::{BlindedRoute, Destination, OnionMessenger, SendError};
 use util::enforcing_trait_impls::EnforcingSigner;
 use util::test_utils;
 
 use bitcoin::network::constants::Network;
-use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
+use bitcoin::secp256k1::{PublicKey, Secp256k1};
 
 use sync::Arc;
 
@@ -34,18 +35,26 @@ impl MessengerNode {
 }
 
 fn create_nodes(num_messengers: u8) -> Vec<MessengerNode> {
-	let mut res = Vec::new();
+	let mut nodes = Vec::new();
 	for i in 0..num_messengers {
 		let logger = Arc::new(test_utils::TestLogger::with_id(format!("node {}", i)));
 		let seed = [i as u8; 32];
 		let keys_manager = Arc::new(test_utils::TestKeysInterface::new(&seed, Network::Testnet));
-		res.push(MessengerNode {
+		nodes.push(MessengerNode {
 			keys_manager: keys_manager.clone(),
 			messenger: OnionMessenger::new(keys_manager, logger.clone()),
 			logger,
 		});
 	}
-	res
+	for idx in 0..num_messengers - 1 {
+		let i = idx as usize;
+		let mut features = InitFeatures::known();
+		features.set_onion_messages_optional();
+		let init_msg = msgs::Init { features, remote_network_address: None };
+		nodes[i].messenger.peer_connected(&nodes[i + 1].get_node_pk(), &init_msg.clone());
+		nodes[i + 1].messenger.peer_connected(&nodes[i].get_node_pk(), &init_msg.clone());
+	}
+	nodes
 }
 
 fn pass_along_path(mut path: Vec<MessengerNode>, expected_path_id: Option<[u8; 32]>) {
@@ -110,12 +119,9 @@ fn three_blinded_hops() {
 #[test]
 fn too_big_packet_error() {
 	// Make sure we error as expected if a packet is too big to send.
-	let nodes = create_nodes(1);
-
-	let hop_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
-	let secp_ctx = Secp256k1::new();
-	let hop_node_id = PublicKey::from_secret_key(&secp_ctx, &hop_secret);
+	let nodes = create_nodes(2);
 
+	let hop_node_id = nodes[1].get_node_pk();
 	let hops = [hop_node_id; 400];
 	let err = nodes[0].messenger.send_onion_message(&hops, Destination::Node(hop_node_id)).unwrap_err();
 	assert_eq!(err, SendError::TooBigPacket);

lightning/src/onion_message/messenger.rs

@@ -85,6 +85,7 @@ pub struct OnionMessenger<Signer: Sign, K: Deref, L: Deref>
 	keys_manager: K,
 	logger: L,
 	pending_messages: Mutex<HashMap<PublicKey, Vec<msgs::OnionMessage>>>,
+	peer_set: Mutex<HashSet<PublicKey>>,
 	secp_ctx: Secp256k1<secp256k1::All>,
 	// Coming soon:
 	// invoice_handler: InvoiceHandler,
@@ -121,6 +122,8 @@ pub enum SendError {
 	/// The provided [`Destination`] was an invalid [`BlindedRoute`], due to having fewer than two
 	/// blinded hops.
 	TooFewBlindedHops,
+	/// Our next-hop peer was offline or does not support onion message forwarding.
+	InvalidFirstHop,
 }
 
 impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
@@ -134,6 +137,7 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
 		secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
 		OnionMessenger {
 			keys_manager,
+			peer_set: Mutex::new(HashSet::new()),
 			pending_messages: Mutex::new(HashMap::new()),
 			secp_ctx,
 			logger,
@@ -159,6 +163,9 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
 					(introduction_node_id, blinding_point),
 			}
 		};
+		if !self.peer_connected(&introduction_node_id) {
+			return Err(SendError::InvalidFirstHop)
+		}
 		let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 			&self.secp_ctx, intermediate_nodes, destination, &blinding_secret)
 			.map_err(|e| SendError::Secp256k1(e))?;
@@ -178,6 +185,11 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
 		Ok(())
 	}
 
+	fn peer_connected(&self, peer_node_id: &PublicKey) -> bool {
+		let peers = self.peer_set.lock().unwrap();
+		peers.contains(peer_node_id)
+	}
+
 	#[cfg(test)]
 	pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, Vec<msgs::OnionMessage>> {
 		let mut pending_msgs = self.pending_messages.lock().unwrap();
@@ -229,6 +241,10 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessageHandler for OnionMessenger<Si
 			Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 				next_node_id, next_blinding_override
 			})), Some((next_hop_hmac, new_packet_bytes)))) => {
+				if !self.peer_connected(&next_node_id) {
+					log_trace!(self.logger, "Dropping onion message to disconnected peer {:?}", next_node_id);
+					return
+				}
 				// TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 				// blinded hop and this onion message is destined for us. In this situation, we should keep
 				// unwrapping the onion layers to get to the final payload. Since we don't have the option
@@ -281,6 +297,27 @@ impl<Signer: Sign, K: Deref, L: Deref> OnionMessageHandler for OnionMessenger<Si
 			},
 		};
 	}
+
+	fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init) {
+		if init.features.supports_onion_messages() {
+			let mut peers = self.peer_set.lock().unwrap();
+			peers.insert(their_node_id.clone());
+		}
+	}
+
+	fn peer_disconnected(&self, their_node_id: &PublicKey, no_connection_possible: bool) {
+		{
+			let mut peers = self.peer_set.lock().unwrap();
+			peers.remove(their_node_id);
+		}
+
+		let mut pending_msgs = self.pending_messages.lock().unwrap();
+		if no_connection_possible {
+			pending_msgs.remove(their_node_id);
+		} else if let Some(msgs) = pending_msgs.get_mut(their_node_id) {
+			msgs.clear();
+		}
+	}
 }
 
 impl<Signer: Sign, K: Deref, L: Deref> OnionMessageProvider for OnionMessenger<Signer, K, L>