feature: Enable setting a node address for a dandelion peer (#2263)

* Configuration to set a fixed dandelion peer
* typo + styling
* more idiomatic way of picking the peer

config/src/comments.rs

@@ -230,6 +230,10 @@ fn comments() -> HashMap<String, String> {
 
 # 15 = Bit flags for FULL_NODE
 #This structure needs to be changed internally, to make it more configurable
+
+# A preferred dandelion_peer, mainly used for testing dandelion
+# dandelion_peer = \"10.0.0.1:13144\"
+
 "
 		.to_string(),
 	);

p2p/src/peers.rs

@@ -84,21 +84,29 @@ impl Peers {
 	pub fn update_dandelion_relay(&self) {
 		let peers = self.outgoing_connected_peers();
 
-		match thread_rng().choose(&peers) {
-			Some(peer) => {
-				// Clear the map and add new relay
-				let dandelion_relay = &self.dandelion_relay;
-				dandelion_relay.write().clear();
-				dandelion_relay
-					.write()
-					.insert(Utc::now().timestamp(), peer.clone());
-				debug!(
-					"Successfully updated Dandelion relay to: {}",
-					peer.info.addr
-				);
-			}
+		let peer = &self
+			.config
+			.dandelion_peer
+			.and_then(|ip| peers.iter().find(|x| x.info.addr == ip))
+			.or(thread_rng().choose(&peers));
+
+		match peer {
+			Some(peer) => self.set_dandelion_relay(peer),
 			None => debug!("Could not update dandelion relay"),
-		};
+		}
+	}
+
+	fn set_dandelion_relay(&self, peer: &Arc<Peer>) {
+		// Clear the map and add new relay
+		let dandelion_relay = &self.dandelion_relay;
+		dandelion_relay.write().clear();
+		dandelion_relay
+			.write()
+			.insert(Utc::now().timestamp(), peer.clone());
+		debug!(
+			"Successfully updated Dandelion relay to: {}",
+			peer.info.addr
+		);
 	}
 
 	// Get the dandelion relay

p2p/src/types.rs

@@ -124,6 +124,8 @@ pub struct P2PConfig {
 	pub peer_max_count: Option<u32>,
 
 	pub peer_min_preferred_count: Option<u32>,
+
+	pub dandelion_peer: Option<SocketAddr>,
 }
 
 /// Default address for peer-to-peer connections.
@@ -142,6 +144,7 @@ impl Default for P2PConfig {
 			ban_window: None,
 			peer_max_count: None,
 			peer_min_preferred_count: None,
+			dandelion_peer: None,
 		}
 	}
 }