Refresh fee estimates during initialization

Startup separately awaited fee estimates and backend capability checks
before initializing wallets. These checks must complete before replay
can construct claim transactions using the fee estimator.

Move the checks into wallet initialization while preserving their
ordering. Run fee refresh and required 0FC validation concurrently,
then synchronize chain state only after both succeed.

Co-Authored-By: HAL 9000

Author: tnull

src/chain/mod.rs

@@ -312,8 +312,17 @@ impl ChainSource {
 	pub(crate) async fn initialize_wallets(
 		&self, stop_sync_receiver: tokio::sync::watch::Receiver<()>, onchain_wallet: Arc<Wallet>,
 		channel_manager: Arc<ChannelManager>, chain_monitor: Arc<ChainMonitor>,
-		output_sweeper: Arc<Sweeper>,
+		output_sweeper: Arc<Sweeper>, zero_fee_commitments_support_required: bool,
 	) -> Result<(), Error> {
+		// Replay can broadcast claims, so refresh fees and validate the backend before syncing.
+		// TODO: drop 0FC chain source validation when support is ubiquitous.
+		tokio::try_join!(
+			self.update_fee_rate_estimates(),
+			self.validate_zero_fee_commitments_support_if_required(
+				zero_fee_commitments_support_required
+			)
+		)?;
+
 		#[cfg(not(feature = "chain-bitcoind"))]
 		let _ = (stop_sync_receiver, onchain_wallet);
 		match &self.kind {

src/lib.rs

@@ -354,21 +354,6 @@ impl Node {
 			|| monitor_owns_any_0fc_channels
 			|| self.config.anchor_channels_config.enable_zero_fee_commitments;
 
-		// Block to ensure we update our fee rate cache once on startup.
-		// Also take this opportunity to make sure our chain source supports 0FC channels
-		// if they are enabled.
-		//
-		// TODO: drop 0FC chain source validation when support is ubiquitous
-		let chain_source = Arc::clone(&self.chain_source);
-		self.runtime.block_on(async move {
-			tokio::try_join!(
-				chain_source.update_fee_rate_estimates(),
-				chain_source.validate_zero_fee_commitments_support_if_required(
-					zero_fee_commitments_support_required
-				)
-			)
-		})?;
-
 		// Synchronize Lightning chain state before peers or event processing can act on stale
 		// confirmations. Each restored ChannelMonitor may have been persisted at a different tip.
 		self.runtime.block_on(self.chain_source.initialize_wallets(
@@ -377,6 +362,7 @@ impl Node {
 			Arc::clone(&self.channel_manager),
 			Arc::clone(&self.chain_monitor),
 			Arc::clone(&self.output_sweeper),
+			zero_fee_commitments_support_required,
 		))?;
 
 		// Spawn background task continuously syncing onchain, lightning, and fee rate cache.