limit amount of hints resulting from filter_channels to 20 and shuffles hints

Author: cdmoss

lightning-invoice/Cargo.toml

@@ -27,6 +27,7 @@ num-traits = { version = "0.2.8", default-features = false }
 bitcoin_hashes = { version = "0.11", default-features = false }
 hashbrown = { version = "0.8", optional = true }
 serde = { version = "1.0.118", optional = true }
+rand = "0.8.5"
 
 [dev-dependencies]
 lightning = { version = "0.0.112", path = "../lightning", default-features = false, features = ["_test_utils"] }

lightning-invoice/src/utils.rs

@@ -20,6 +20,8 @@ use lightning::util::logger::Logger;
 use secp256k1::PublicKey;
 use core::ops::Deref;
 use core::time::Duration;
+use rand::thread_rng;
+use rand::seq::SliceRandom;
 
 #[cfg(feature = "std")]
 /// Utility to create an invoice that can be paid to one of multiple nodes, or a "phantom invoice."
@@ -529,7 +531,7 @@ fn filter_channels<L: Deref>(
 	// the payment value and where we're currently connected to the channel counterparty.
 	// Even if we cannot satisfy both goals, always ensure we include *some* hints, preferring
 	// those which meet at least one criteria.
-	filtered_channels
+	let mut final_channels = filtered_channels
 		.into_iter()
 		.map(|(_, channel)| channel)
 		.filter(|channel| {
@@ -562,7 +564,13 @@ fn filter_channels<L: Deref>(
 			include_channel
 		})
 		.map(route_hint_from_channel)
-		.collect::<Vec<RouteHint>>()
+		// Following LND's lead by taking max 20 hints
+		.take(20)
+		.collect::<Vec<RouteHint>>();
+		
+	// Shuffle selected channels to prevent channel exhaustion
+	final_channels.shuffle(&mut thread_rng());
+	final_channels
 }
 
 impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Payer for ChannelManager<M, T, K, F, L>