litep2p/discovery: Publish authority records with external addresses only (#5176)

This PR reduces the occurrences for identified observed addresses.

Litep2p discovers its external addresses by inspecting the
`IdentifyInfo::ObservedAddress` field reported by other peers.
After we get 5 confirmations of the same external observed address (the
address the peer dialed to reach us), the address is reported through
the network layer.

The PR effectively changes this from 5 to 2.
This has a subtle implication on freshly started nodes for the
authority-discovery discussed below.

The PR also makes the authority discovery a bit more robust by not
publishing records if the node doesn't have addresses yet to report.
This aims to fix a scenario where:
- the litep2p node has started, it has some pending observed addresses
but less than 5
- the authorit-discovery publishes a record, but at this time the node
doesn't have any addresses discovered and the record is published
without addresses -> this means other nodes will not be able to reach us

Next Steps
- [ ] versi testing

Closes: #5147

cc @paritytech/networking

---------

Signed-off-by: Alexandru Vasile <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>

Author: lexnv

substrate/client/authority-discovery/src/worker.rs

@@ -37,7 +37,7 @@ use ip_network::IpNetwork;
 use libp2p::kad::{PeerRecord, Record};
 use linked_hash_set::LinkedHashSet;
 
-use log::{debug, error};
+use log::{debug, error, trace};
 use prometheus_endpoint::{register, Counter, CounterVec, Gauge, Opts, U64};
 use prost::Message;
 use rand::{seq::SliceRandom, thread_rng};
@@ -416,10 +416,12 @@ where
 			})
 			.collect::<Vec<_>>();
 
-		debug!(
-			target: LOG_TARGET,
-			"Publishing authority DHT record peer_id='{local_peer_id}' addresses='{addresses:?}'",
-		);
+		if !addresses.is_empty() {
+			debug!(
+				target: LOG_TARGET,
+				"Publishing authority DHT record peer_id='{local_peer_id}' with addresses='{addresses:?}'",
+			);
+		}
 
 		// The address must include the local peer id.
 		addresses
@@ -437,6 +439,17 @@ where
 			Role::Discover => return Ok(()),
 		};
 
+		let addresses = serialize_addresses(self.addresses_to_publish());
+		if addresses.is_empty() {
+			trace!(
+				target: LOG_TARGET,
+				"No addresses to publish. Skipping publication."
+			);
+
+			self.publish_interval.set_to_start();
+			return Ok(())
+		}
+
 		let keys =
 			Worker::<Client, Block, DhtEventStream>::get_own_public_keys_within_authority_set(
 				key_store.clone(),
@@ -459,8 +472,6 @@ where
 			self.query_interval.set_to_start();
 		}
 
-		let addresses = serialize_addresses(self.addresses_to_publish());
-
 		if let Some(metrics) = &self.metrics {
 			metrics.publish.inc();
 			metrics

substrate/client/network/src/litep2p/discovery.rs

@@ -66,12 +66,18 @@ const KADEMLIA_QUERY_INTERVAL: Duration = Duration::from_secs(5);
 /// mDNS query interval.
 const MDNS_QUERY_INTERVAL: Duration = Duration::from_secs(30);
 
-/// Minimum number of confirmations received before an address is verified.
-const MIN_ADDRESS_CONFIRMATIONS: usize = 5;
-
-// The minimum number of peers we expect an answer before we terminate the request.
+/// The minimum number of peers we expect an answer before we terminate the request.
 const GET_RECORD_REDUNDANCY_FACTOR: usize = 4;
 
+/// The maximum number of tracked external addresses we allow.
+const MAX_EXTERNAL_ADDRESSES: u32 = 32;
+
+/// Minimum number of confirmations received before an address is verified.
+///
+/// Note: all addresses are confirmed by libp2p on the first encounter. This aims to make
+/// addresses a bit more robust.
+const MIN_ADDRESS_CONFIRMATIONS: usize = 2;
+
 /// Discovery events.
 #[derive(Debug)]
 pub enum DiscoveryEvent {
@@ -195,7 +201,7 @@ pub struct Discovery {
 	listen_addresses: Arc<RwLock<HashSet<Multiaddr>>>,
 
 	/// External address confirmations.
-	address_confirmations: LruMap<Multiaddr, usize>,
+	address_confirmations: LruMap<Multiaddr, HashSet<PeerId>>,
 
 	/// Delay to next `FIND_NODE` query.
 	duration_to_next_find_query: Duration,
@@ -278,7 +284,7 @@ impl Discovery {
 				find_node_query_id: None,
 				pending_events: VecDeque::new(),
 				duration_to_next_find_query: Duration::from_secs(1),
-				address_confirmations: LruMap::new(ByLength::new(8)),
+				address_confirmations: LruMap::new(ByLength::new(MAX_EXTERNAL_ADDRESSES)),
 				allow_non_global_addresses: config.allow_non_globals_in_dht,
 				public_addresses: config.public_addresses.iter().cloned().map(Into::into).collect(),
 				next_kad_query: Some(Delay::new(KADEMLIA_QUERY_INTERVAL)),
@@ -428,7 +434,7 @@ impl Discovery {
 	}
 
 	/// Check if `address` can be considered a new external address.
-	fn is_new_external_address(&mut self, address: &Multiaddr) -> bool {
+	fn is_new_external_address(&mut self, address: &Multiaddr, peer: PeerId) -> bool {
 		log::trace!(target: LOG_TARGET, "verify new external address: {address}");
 
 		// is the address one of our known addresses
@@ -444,14 +450,14 @@ impl Discovery {
 
 		match self.address_confirmations.get(address) {
 			Some(confirmations) => {
-				*confirmations += 1usize;
+				confirmations.insert(peer);
 
-				if *confirmations >= MIN_ADDRESS_CONFIRMATIONS {
+				if confirmations.len() >= MIN_ADDRESS_CONFIRMATIONS {
 					return true
 				}
 			},
 			None => {
-				self.address_confirmations.insert(address.clone(), 1usize);
+				self.address_confirmations.insert(address.clone(), Default::default());
 			},
 		}
 
@@ -563,7 +569,7 @@ impl Stream for Discovery {
 				supported_protocols,
 				observed_address,
 			})) => {
-				if this.is_new_external_address(&observed_address) {
+				if this.is_new_external_address(&observed_address, peer) {
 					this.pending_events.push_back(DiscoveryEvent::ExternalAddressDiscovered {
 						address: observed_address.clone(),
 					});

substrate/client/network/src/litep2p/mod.rs

@@ -920,7 +920,7 @@ impl<B: BlockT + 'static, H: ExHashT> NetworkBackend<B, H> for Litep2pNetworkBac
 						let mut addresses = self.external_addresses.write();
 
 						if addresses.insert(address.clone()) {
-							log::info!(target: LOG_TARGET, "discovered new external address for our node: {address}");
+							log::info!(target: LOG_TARGET, "🔍 Discovered new external address for our node: {address}");
 						}
 					}
 					Some(DiscoveryEvent::Ping { peer, rtt }) => {