Ping nodes from discovery (#10167)

util/network-devp2p/src/discovery.rs

@@ -53,12 +53,15 @@ const REQUEST_BACKOFF: [Duration; 4] = [
 	Duration::from_secs(64)
 ];
 
+const NODE_LAST_SEEN_TIMEOUT: Duration = Duration::from_secs(24*60*60);
+
 #[derive(Clone, Debug)]
 pub struct NodeEntry {
 	pub id: NodeId,
 	pub endpoint: NodeEndpoint,
 }
 
+#[derive(Debug)]
 pub struct BucketEntry {
 	pub address: NodeEntry,
 	pub id_hash: H256,
@@ -89,6 +92,12 @@ struct FindNodeRequest {
 	answered: bool,
 }
 
+#[derive(Clone, Copy)]
+enum PingReason {
+	Default,
+	FromDiscoveryRequest(NodeId)
+}
+
 struct PingRequest {
 	// Time when the request was sent
 	sent_at: Instant,
@@ -99,8 +108,10 @@ struct PingRequest {
 	// The hash Parity used to respond with (until rev 01f825b0e1f1c4c420197b51fc801cbe89284b29)
 	#[deprecated()]
 	deprecated_echo_hash: H256,
+	reason: PingReason
 }
 
+#[derive(Debug)]
 pub struct NodeBucket {
 	nodes: VecDeque<BucketEntry>, //sorted by last active
 }
@@ -178,7 +189,7 @@ impl<'a> Discovery<'a> {
 			if self.node_buckets[dist].nodes.iter().any(|n| n.id_hash == id_hash) {
 				return;
 			}
-			self.try_ping(e);
+			self.try_ping(e, PingReason::Default);
 		}
 	}
 
@@ -221,7 +232,7 @@ impl<'a> Discovery<'a> {
 			} else { None }
 		};
 		if let Some(node) = ping {
-			self.try_ping(node);
+			self.try_ping(node, PingReason::Default);
 		}
 		Some(TableUpdates { added: added_map, removed: HashSet::new() })
 	}
@@ -244,7 +255,7 @@ impl<'a> Discovery<'a> {
 	fn update_new_nodes(&mut self) {
 		while self.in_flight_pings.len() < MAX_NODES_PING {
 			match self.adding_nodes.pop() {
-				Some(next) => self.try_ping(next),
+				Some(next) => self.try_ping(next, PingReason::Default),
 				None => break,
 			}
 		}
@@ -298,7 +309,7 @@ impl<'a> Discovery<'a> {
 		None // a and b are equal, so log distance is -inf
 	}
 
-	fn try_ping(&mut self, node: NodeEntry) {
+	fn try_ping(&mut self, node: NodeEntry, reason: PingReason) {
 		if !self.is_allowed(&node) {
 			trace!(target: "discovery", "Node {:?} not allowed", node);
 			return;
@@ -313,7 +324,7 @@ impl<'a> Discovery<'a> {
 		}
 
 		if self.in_flight_pings.len() < MAX_NODES_PING {
-			self.ping(&node)
+			self.ping(&node, reason)
 				.unwrap_or_else(|e| {
 					warn!(target: "discovery", "Error sending Ping packet: {:?}", e);
 				});
@@ -322,7 +333,7 @@ impl<'a> Discovery<'a> {
 		}
 	}
 
-	fn ping(&mut self, node: &NodeEntry) -> Result<(), Error> {
+	fn ping(&mut self, node: &NodeEntry, reason: PingReason) -> Result<(), Error> {
 		let mut rlp = RlpStream::new_list(4);
 		rlp.append(&PROTOCOL_VERSION);
 		self.public_endpoint.to_rlp_list(&mut rlp);
@@ -336,6 +347,7 @@ impl<'a> Discovery<'a> {
 			node: node.clone(),
 			echo_hash: hash,
 			deprecated_echo_hash: old_parity_hash,
+			reason: reason
 		});
 
 		trace!(target: "discovery", "Sent Ping to {:?} ; node_id={:#x}", &node.endpoint, node.id);
@@ -514,7 +526,7 @@ impl<'a> Discovery<'a> {
 						if request.deprecated_echo_hash == echo_hash {
 							trace!(target: "discovery", "Got Pong from an old parity-ethereum version.");
 						}
-						Some(request.node.clone())
+						Some((request.node.clone(), request.reason.clone()))
 					}
 				};
 
@@ -528,7 +540,10 @@ impl<'a> Discovery<'a> {
 			},
 		};
 
-		if let Some(node) = expected_node {
+		if let Some((node, ping_reason)) = expected_node {
+			if let PingReason::FromDiscoveryRequest(target) = ping_reason {
+				self.respond_with_discovery(target, &node)?;
+			}
 			Ok(self.update_node(node))
 		} else {
 			debug!(target: "discovery", "Got unexpected Pong from {:?} ; request not found", &from);
@@ -536,21 +551,59 @@ impl<'a> Discovery<'a> {
 		}
 	}
 
-	fn on_find_node(&mut self, rlp: &Rlp, _node: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, Error> {
+	fn on_find_node(&mut self, rlp: &Rlp, node_id: &NodeId, from: &SocketAddr) -> Result<Option<TableUpdates>, Error> {
 		trace!(target: "discovery", "Got FindNode from {:?}", &from);
 		let target: NodeId = rlp.val_at(0)?;
 		let timestamp: u64 = rlp.val_at(1)?;
 		self.check_timestamp(timestamp)?;
+
+		let node = NodeEntry {
+			id: node_id.clone(),
+			endpoint: NodeEndpoint {
+				address: *from,
+				udp_port: from.port()
+			}
+		};
+
+		if self.is_a_valid_known_node(&node) {
+			self.respond_with_discovery(target, &node)?;
+		} else {
+			// Make sure the request source is actually there and responds to pings before actually responding
+			self.try_ping(node, PingReason::FromDiscoveryRequest(target));
+		}
+		Ok(None)
+	}
+
+	fn is_a_valid_known_node(&self, node: &NodeEntry) -> bool {
+		let id_hash = keccak(node.id);
+		let dist = match Discovery::distance(&self.id_hash, &id_hash) {
+			Some(dist) => dist,
+			None => {
+				debug!(target: "discovery", "Got an incoming discovery request from self: {:?}", node);
+				return false;
+			}
+		};
+
+		let bucket = &self.node_buckets[dist];
+		if let Some(known_node) = bucket.nodes.iter().find(|n| n.address.id == node.id) {
+			debug!(target: "discovery", "Found a known node in a bucket when processing discovery: {:?}/{:?}", known_node, node);
+			(known_node.address.endpoint == node.endpoint) && (known_node.last_seen.elapsed() < NODE_LAST_SEEN_TIMEOUT)
+		} else {
+			false
+		}
+	}
+
+	fn respond_with_discovery(&mut self, target: NodeId, node: &NodeEntry) -> Result<(), Error> {
 		let nearest = self.nearest_node_entries(&target);
 		if nearest.is_empty() {
-			return Ok(None);
+			return Ok(());
 		}
 		let mut packets = Discovery::prepare_neighbours_packets(&nearest);
 		for p in packets.drain(..) {
-			self.send_packet(PACKET_NEIGHBOURS, from, &p)?;
+			self.send_packet(PACKET_NEIGHBOURS, &node.endpoint.address, &p)?;
 		}
-		trace!(target: "discovery", "Sent {} Neighbours to {:?}", nearest.len(), &from);
+		trace!(target: "discovery", "Sent {} Neighbours to {:?}", nearest.len(), &node.endpoint);
-		Ok(None)
+		Ok(())
 	}
 
 	fn prepare_neighbours_packets(nearest: &[NodeEntry]) -> Vec<Bytes> {
@@ -825,7 +878,7 @@ mod tests {
 		}
 
 		// After 4 discovery rounds, the first one should have learned about the rest.
-		for _round in 0 .. 4 {
+		for _round in 0 .. 5 {
 			discovery_handlers[0].round();
 
 			let mut continue_loop = true;
@@ -833,9 +886,9 @@ mod tests {
 				continue_loop = false;
 
 				// Process all queued messages.
-				for i in 0 .. 5 {
+				for i in 0 .. 20 {
-					let src = discovery_handlers[i].public_endpoint.address.clone();
+					let src = discovery_handlers[i%5].public_endpoint.address.clone();
-					while let Some(datagram) = discovery_handlers[i].dequeue_send() {
+					while let Some(datagram) = discovery_handlers[i%5].dequeue_send() {
 						let dest = discovery_handlers.iter_mut()
 							.find(|disc| datagram.address == disc.public_endpoint.address)
 							.unwrap();
@@ -927,14 +980,14 @@ mod tests {
 		let mut discovery = Discovery { request_backoff: &request_backoff, ..discovery };
 
 		for _ in 0..2 {
-			discovery.ping(&node_entries[101]).unwrap();
+			discovery.ping(&node_entries[101], PingReason::Default).unwrap();
 			let num_nodes = total_bucket_nodes(&discovery.node_buckets);
 			discovery.check_expired(Instant::now() + PING_TIMEOUT);
 			let removed = num_nodes - total_bucket_nodes(&discovery.node_buckets);
 			assert_eq!(removed, 0);
 		}
 
-		discovery.ping(&node_entries[101]).unwrap();
+		discovery.ping(&node_entries[101], PingReason::Default).unwrap();
 		let num_nodes = total_bucket_nodes(&discovery.node_buckets);
 		discovery.check_expired(Instant::now() + PING_TIMEOUT);
 		let removed = num_nodes - total_bucket_nodes(&discovery.node_buckets);
@@ -1121,7 +1174,7 @@ mod tests {
 		let mut discovery1 = Discovery::new(&key1, ep1.clone(), IpFilter::default());
 		let mut discovery2 = Discovery::new(&key2, ep2.clone(), IpFilter::default());
 
-		discovery1.ping(&NodeEntry { id: discovery2.id, endpoint: ep2.clone() }).unwrap();
+		discovery1.ping(&NodeEntry { id: discovery2.id, endpoint: ep2.clone() }, PingReason::Default).unwrap();
 		let ping_data = discovery1.dequeue_send().unwrap();
 		assert!(!discovery1.any_sends_queued());
 		let data = &ping_data.payload[(32 + 65)..];