Recalculate listeners' best block heights on each retry

Previously, we would calculate each listener's best block height outside
of the `loop`, which will have us retrying `init::synchronize_listeners`
with stale data, potentially leading to panicking as we might try to
connect blocks from the original height to listeners that might have
been advanced by the previous itertation of the `loop` before hitting an
error. Here, we mitigate this by simply retrieving the current best
block height for each listener at the start of each iteration.

src/chain/mod.rs

@@ -281,48 +281,49 @@ impl ChainSource {
 					}
 				}
 
-				let channel_manager_best_block_hash =
-					channel_manager.current_best_block().block_hash;
-				let sweeper_best_block_hash = output_sweeper.current_best_block().block_hash;
-				let onchain_wallet_best_block_hash = onchain_wallet.current_best_block().block_hash;
-
-				let mut chain_listeners = vec![
-					(
-						onchain_wallet_best_block_hash,
-						&**onchain_wallet as &(dyn Listen + Send + Sync),
-					),
-					(
-						channel_manager_best_block_hash,
-						&*channel_manager as &(dyn Listen + Send + Sync),
-					),
-					(sweeper_best_block_hash, &*output_sweeper as &(dyn Listen + Send + Sync)),
-				];
-
-				// TODO: Eventually we might want to see if we can synchronize `ChannelMonitor`s
-				// before giving them to `ChainMonitor` it the first place. However, this isn't
-				// trivial as we load them on initialization (in the `Builder`) and only gain
-				// network access during `start`. For now, we just make sure we get the worst known
-				// block hash and sychronize them via `ChainMonitor`.
-				if let Some(worst_channel_monitor_block_hash) = chain_monitor
-					.list_monitors()
-					.iter()
-					.flat_map(|(txo, _)| chain_monitor.get_monitor(*txo))
-					.map(|m| m.current_best_block())
-					.min_by_key(|b| b.height)
-					.map(|b| b.block_hash)
-				{
-					chain_listeners.push((
-						worst_channel_monitor_block_hash,
-						&*chain_monitor as &(dyn Listen + Send + Sync),
-					));
-				}
-
 				log_info!(
 					logger,
 					"Starting initial synchronization of chain listeners. This might take a while..",
 				);
 
 				loop {
+					let channel_manager_best_block_hash =
+						channel_manager.current_best_block().block_hash;
+					let sweeper_best_block_hash = output_sweeper.current_best_block().block_hash;
+					let onchain_wallet_best_block_hash =
+						onchain_wallet.current_best_block().block_hash;
+
+					let mut chain_listeners = vec![
+						(
+							onchain_wallet_best_block_hash,
+							&**onchain_wallet as &(dyn Listen + Send + Sync),
+						),
+						(
+							channel_manager_best_block_hash,
+							&*channel_manager as &(dyn Listen + Send + Sync),
+						),
+						(sweeper_best_block_hash, &*output_sweeper as &(dyn Listen + Send + Sync)),
+					];
+
+					// TODO: Eventually we might want to see if we can synchronize `ChannelMonitor`s
+					// before giving them to `ChainMonitor` it the first place. However, this isn't
+					// trivial as we load them on initialization (in the `Builder`) and only gain
+					// network access during `start`. For now, we just make sure we get the worst known
+					// block hash and sychronize them via `ChainMonitor`.
+					if let Some(worst_channel_monitor_block_hash) = chain_monitor
+						.list_monitors()
+						.iter()
+						.flat_map(|(txo, _)| chain_monitor.get_monitor(*txo))
+						.map(|m| m.current_best_block())
+						.min_by_key(|b| b.height)
+						.map(|b| b.block_hash)
+					{
+						chain_listeners.push((
+							worst_channel_monitor_block_hash,
+							&*chain_monitor as &(dyn Listen + Send + Sync),
+						));
+					}
+
 					let mut locked_header_cache = header_cache.lock().await;
 					let now = SystemTime::now();
 					match synchronize_listeners(