Add ability to broadcast our own node_announcement.

This is a somewhat-obvious oversight in the capabilities of
rust-lightning, though not a particularly interesting one until we
start relying on node_features (eg for variable-length-onions and
Base AMP).

Sadly its not fully automated as we don't really want to store the
list of available addresses from the user. However, with a simple
call to ChannelManager::broadcast_node_announcement and a sensible
peer_handler, the announcement is made.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -29,8 +29,8 @@ use chain::chaininterface::{BroadcasterInterface,ChainListener,FeeEstimator};
 use chain::transaction::OutPoint;
 use ln::channel::{Channel, ChannelError};
 use ln::channelmonitor::{ChannelMonitor, ChannelMonitorUpdateErr, ManyChannelMonitor, CLTV_CLAIM_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS, ANTI_REORG_DELAY};
+use ln::features::{InitFeatures, NodeFeatures};
 use ln::router::Route;
-use ln::features::InitFeatures;
 use ln::msgs;
 use ln::onion_utils;
 use ln::msgs::{ChannelMessageHandler, DecodeError, LightningError};
@@ -368,6 +368,10 @@ pub struct ChannelManager<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref,
 	channel_state: Mutex<ChannelHolder<ChanSigner>>,
 	our_network_key: SecretKey,
 
+	/// Used to track the last value sent in a node_announcement "timestamp" field. We ensure this
+	/// value increases strictly since we don't assume access to a time source.
+	last_node_announcement_serial: AtomicUsize,
+
 	/// The bulk of our storage will eventually be here (channels and message queues and the like).
 	/// If we are connected to a peer we always at least have an entry here, even if no channels
 	/// are currently open with that peer.
@@ -665,6 +669,8 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref> ChannelMan
 			}),
 			our_network_key: keys_manager.get_node_secret(),
 
+			last_node_announcement_serial: AtomicUsize::new(0),
+
 			per_peer_state: RwLock::new(HashMap::new()),
 
 			pending_events: Mutex::new(Vec::new()),
@@ -1334,6 +1340,50 @@ impl<ChanSigner: ChannelKeys, M: Deref, T: Deref, K: Deref, F: Deref> ChannelMan
 		})
 	}
 
+	#[allow(dead_code)]
+	const HALF_MESSAGE_IS_ADDRS: u32 = 64*1024 / (msgs::NetAddress::MAX_LEN as u32 + 1) / 2;
+	#[deny(const_err)]
+	#[allow(dead_code)]
+	const STATIC_ASSERT: u32 = Self::HALF_MESSAGE_IS_ADDRS - 500; // This will fail to compile if we use half of the message with 500 addresses
+	/// Generates a signed node_announcement from the given arguments and creates a
+	/// BroadcastNodeAnnouncement event. Note that such messages will be ignored unless peers have
+	/// seen a channel_announcement from us (ie unless we have public channels open).
+	///
+	/// RGB is a node "color" and alias is a printable human-readable string to describe this node
+	/// to humans. They carry no in-protocol meaning.
+	///
+	/// addresses represent the set (possibly empty) of socket addresses on which this node accepts
+	/// incoming connections. These will be broadcast to the network, publicly tying these
+	/// addresses together. If you wish to preserve user privacy, addresses should likely contain
+	/// only Tor Onion addresses.
+	///
+	/// Panics if addresses is absurdly large (more than 500).
+	pub fn broadcast_node_announcement(&self, rgb: [u8; 3], alias: [u8; 32], addresses: Vec<msgs::NetAddress>) {
+		let _ = self.total_consistency_lock.read().unwrap();
+
+		if addresses.len() > 500 {
+			panic!("More than half the message size was taken up by public addresses!");
+		}
+
+		let announcement = msgs::UnsignedNodeAnnouncement {
+			features: NodeFeatures::supported(),
+			timestamp: self.last_node_announcement_serial.fetch_add(1, Ordering::AcqRel) as u32,
+			node_id: self.get_our_node_id(),
+			rgb, alias, addresses,
+			excess_address_data: Vec::new(),
+			excess_data: Vec::new(),
+		};
+		let msghash = hash_to_message!(&Sha256dHash::hash(&announcement.encode()[..])[..]);
+
+		let mut channel_state = self.channel_state.lock().unwrap();
+		channel_state.pending_msg_events.push(events::MessageSendEvent::BroadcastNodeAnnouncement {
+			msg: msgs::NodeAnnouncement {
+				signature: self.secp_ctx.sign(&msghash, &self.our_network_key),
+				contents: announcement
+			},
+		});
+	}
+
 	/// Processes HTLCs which are pending waiting on random forward delay.
 	///
 	/// Should only really ever be called in response to a PendingHTLCsForwardable event.
@@ -2970,6 +3020,7 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
 					&events::MessageSendEvent::SendShutdown { ref node_id, .. } => node_id != their_node_id,
 					&events::MessageSendEvent::SendChannelReestablish { ref node_id, .. } => node_id != their_node_id,
 					&events::MessageSendEvent::BroadcastChannelAnnouncement { .. } => true,
+					&events::MessageSendEvent::BroadcastNodeAnnouncement { .. } => true,
 					&events::MessageSendEvent::BroadcastChannelUpdate { .. } => true,
 					&events::MessageSendEvent::HandleError { ref node_id, .. } => node_id != their_node_id,
 					&events::MessageSendEvent::PaymentFailureNetworkUpdate { .. } => true,
@@ -3288,6 +3339,8 @@ impl<ChanSigner: ChannelKeys + Writeable, M: Deref, T: Deref, K: Deref, F: Deref
 			peer_state.latest_features.write(writer)?;
 		}
 
+		(self.last_node_announcement_serial.load(Ordering::Acquire) as u32).write(writer)?;
+
 		Ok(())
 	}
 }
@@ -3459,6 +3512,8 @@ impl<'a, ChanSigner: ChannelKeys + Readable, M: Deref, T: Deref, K: Deref, F: De
 			per_peer_state.insert(peer_pubkey, Mutex::new(peer_state));
 		}
 
+		let last_node_announcement_serial: u32 = Readable::read(reader)?;
+
 		let channel_manager = ChannelManager {
 			genesis_hash,
 			fee_estimator: args.fee_estimator,
@@ -3478,6 +3533,8 @@ impl<'a, ChanSigner: ChannelKeys + Readable, M: Deref, T: Deref, K: Deref, F: De
 			}),
 			our_network_key: args.keys_manager.get_node_secret(),
 
+			last_node_announcement_serial: AtomicUsize::new(last_node_announcement_serial as usize),
+
 			per_peer_state: RwLock::new(per_peer_state),
 
 			pending_events: Mutex::new(Vec::new()),

lightning/src/ln/functional_test_utils.rs

@@ -394,10 +394,33 @@ pub fn create_announced_chan_between_nodes<'a, 'b, 'c, 'd>(nodes: &'a Vec<Node<'
 
 pub fn create_announced_chan_between_nodes_with_value<'a, 'b, 'c, 'd>(nodes: &'a Vec<Node<'b, 'c, 'd>>, a: usize, b: usize, channel_value: u64, push_msat: u64, a_flags: InitFeatures, b_flags: InitFeatures) -> (msgs::ChannelUpdate, msgs::ChannelUpdate, [u8; 32], Transaction) {
 	let chan_announcement = create_chan_between_nodes_with_value(&nodes[a], &nodes[b], channel_value, push_msat, a_flags, b_flags);
+
+	nodes[a].node.broadcast_node_announcement([0, 0, 0], [0; 32], Vec::new());
+	let a_events = nodes[a].node.get_and_clear_pending_msg_events();
+	assert_eq!(a_events.len(), 1);
+	let a_node_announcement = match a_events[0] {
+		MessageSendEvent::BroadcastNodeAnnouncement { ref msg } => {
+			(*msg).clone()
+		},
+		_ => panic!("Unexpected event"),
+	};
+
+	nodes[b].node.broadcast_node_announcement([1, 1, 1], [1; 32], Vec::new());
+	let b_events = nodes[b].node.get_and_clear_pending_msg_events();
+	assert_eq!(b_events.len(), 1);
+	let b_node_announcement = match b_events[0] {
+		MessageSendEvent::BroadcastNodeAnnouncement { ref msg } => {
+			(*msg).clone()
+		},
+		_ => panic!("Unexpected event"),
+	};
+
 	for node in nodes {
 		assert!(node.router.handle_channel_announcement(&chan_announcement.0).unwrap());
 		node.router.handle_channel_update(&chan_announcement.1).unwrap();
 		node.router.handle_channel_update(&chan_announcement.2).unwrap();
+		node.router.handle_node_announcement(&a_node_announcement).unwrap();
+		node.router.handle_node_announcement(&b_node_announcement).unwrap();
 	}
 	(chan_announcement.1, chan_announcement.2, chan_announcement.3, chan_announcement.4)
 }

lightning/src/ln/msgs.rs

@@ -302,6 +302,9 @@ impl NetAddress {
 			&NetAddress::OnionV3 { .. } => { 37 },
 		}
 	}
+
+	/// The maximum length of any address descriptor, not including the 1-byte type
+	pub(crate) const MAX_LEN: u16 = 37;
 }
 
 impl Writeable for NetAddress {

lightning/src/ln/peer_handler.rs

@@ -133,13 +133,22 @@ impl Peer {
 	/// announcements/updates for the given channel_id then we will send it when we get to that
 	/// point and we shouldn't send it yet to avoid sending duplicate updates. If we've already
 	/// sent the old versions, we should send the update, and so return true here.
-	fn should_forward_channel(&self, channel_id: u64)->bool{
+	fn should_forward_channel_announcement(&self, channel_id: u64)->bool{
 		match self.sync_status {
 			InitSyncTracker::NoSyncRequested => true,
 			InitSyncTracker::ChannelsSyncing(i) => i < channel_id,
 			InitSyncTracker::NodesSyncing(_) => true,
 		}
 	}
+
+	/// Similar to the above, but for node announcements indexed by node_id.
+	fn should_forward_node_announcement(&self, node_id: PublicKey) -> bool {
+		match self.sync_status {
+			InitSyncTracker::NoSyncRequested => true,
+			InitSyncTracker::ChannelsSyncing(_) => false,
+			InitSyncTracker::NodesSyncing(pk) => pk < node_id,
+		}
+	}
 }
 
 struct PeerHolder<Descriptor: SocketDescriptor> {
@@ -954,7 +963,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref> PeerManager<Descriptor, CM> where
 
 							for (ref descriptor, ref mut peer) in peers.peers.iter_mut() {
 								if !peer.channel_encryptor.is_ready_for_encryption() || peer.their_features.is_none() ||
-										!peer.should_forward_channel(msg.contents.short_channel_id) {
+										!peer.should_forward_channel_announcement(msg.contents.short_channel_id) {
 									continue
 								}
 								match peer.their_node_id {
@@ -971,14 +980,29 @@ impl<Descriptor: SocketDescriptor, CM: Deref> PeerManager<Descriptor, CM> where
 							}
 						}
 					},
+					MessageSendEvent::BroadcastNodeAnnouncement { ref msg } => {
+						log_trace!(self, "Handling BroadcastNodeAnnouncement event in peer_handler");
+						if self.message_handler.route_handler.handle_node_announcement(msg).is_ok() {
+							let encoded_msg = encode_msg!(msg);
+
+							for (ref descriptor, ref mut peer) in peers.peers.iter_mut() {
+								if !peer.channel_encryptor.is_ready_for_encryption() || peer.their_features.is_none() ||
+										!peer.should_forward_node_announcement(msg.contents.node_id) {
+									continue
+								}
+								peer.pending_outbound_buffer.push_back(peer.channel_encryptor.encrypt_message(&encoded_msg[..]));
+								self.do_attempt_write_data(&mut (*descriptor).clone(), peer);
+							}
+						}
+					},
 					MessageSendEvent::BroadcastChannelUpdate { ref msg } => {
 						log_trace!(self, "Handling BroadcastChannelUpdate event in peer_handler for short channel id {}", msg.contents.short_channel_id);
 						if self.message_handler.route_handler.handle_channel_update(msg).is_ok() {
 							let encoded_msg = encode_msg!(msg);
 
 							for (ref descriptor, ref mut peer) in peers.peers.iter_mut() {
 								if !peer.channel_encryptor.is_ready_for_encryption() || peer.their_features.is_none() ||
-										!peer.should_forward_channel(msg.contents.short_channel_id)  {
+										!peer.should_forward_channel_announcement(msg.contents.short_channel_id)  {
 									continue
 								}
 								peer.pending_outbound_buffer.push_back(peer.channel_encryptor.encrypt_message(&encoded_msg[..]));

lightning/src/util/events.rs

@@ -278,12 +278,23 @@ pub enum MessageSendEvent {
 	},
 	/// Used to indicate that a channel_announcement and channel_update should be broadcast to all
 	/// peers (except the peer with node_id either msg.contents.node_id_1 or msg.contents.node_id_2).
+	///
+	/// Note that after doing so, you very likely (unless you did so very recently) want to call
+	/// ChannelManager::broadcast_node_announcement to trigger a BroadcastNodeAnnouncement event.
+	/// This ensures that any nodes which see our channel_announcement also have a relevant
+	/// node_announcement, including relevant feature flags which may be important for routing
+	/// through or to us.
 	BroadcastChannelAnnouncement {
 		/// The channel_announcement which should be sent.
 		msg: msgs::ChannelAnnouncement,
 		/// The followup channel_update which should be sent.
 		update_msg: msgs::ChannelUpdate,
 	},
+	/// Used to indicate that a node_announcement should be broadcast to all peers.
+	BroadcastNodeAnnouncement {
+		/// The node_announcement which should be sent.
+		msg: msgs::NodeAnnouncement,
+	},
 	/// Used to indicate that a channel_update should be broadcast to all peers.
 	BroadcastChannelUpdate {
 		/// The channel_update which should be sent.