Prefactor: Make monior archival delay a pub const

.. previously we just used the 4032 magic number, here we put it in a
`pub const` that is reusable elsewhere.

Author: tnull

lightning/src/chain/channelmonitor.rs

@@ -256,6 +256,10 @@ pub(crate) const LATENCY_GRACE_PERIOD_BLOCKS: u32 = 3;
 // solved by a previous claim tx. What we want to avoid is reorg evicting our claim tx and us not
 // keep bumping another claim tx to solve the outpoint.
 pub const ANTI_REORG_DELAY: u32 = 6;
+/// Number of blocks we wait before assuming a [`ChannelMonitor`] to be fully resolved and
+/// considering it be safely archived.
+// 4032 blocks are roughly four weeks
+pub const ARCHIVAL_DELAY_BLOCKS: u32 = 4032;
 /// Number of blocks before confirmation at which we fail back an un-relayed HTLC or at which we
 /// refuse to accept a new HTLC.
 ///
@@ -2015,10 +2019,11 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 	///
 	/// This function returns a tuple of two booleans, the first indicating whether the monitor is
 	/// fully resolved, and the second whether the monitor needs persistence to ensure it is
-	/// reliably marked as resolved within 4032 blocks.
+	/// reliably marked as resolved within [`ARCHIVAL_DELAY_BLOCKS`] blocks.
 	///
-	/// The first boolean is true only if [`Self::get_claimable_balances`] has been empty for at least
-	/// 4032 blocks as an additional protection against any bugs resulting in spuriously empty balance sets.
+	/// The first boolean is true only if [`Self::get_claimable_balances`] has been empty for at
+	/// least [`ARCHIVAL_DELAY_BLOCKS`] blocks as an additional protection against any bugs
+	/// resulting in spuriously empty balance sets.
 	pub fn check_and_update_full_resolution_status<L: Logger>(&self, logger: &L) -> (bool, bool) {
 		let mut is_all_funds_claimed = self.get_claimable_balances().is_empty();
 		let current_height = self.current_best_block().height;
@@ -2034,11 +2039,10 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 		// once processed, implies the preimage exists in the corresponding inbound channel.
 		let preimages_not_needed_elsewhere = inner.pending_monitor_events.is_empty();
 
-		const BLOCKS_THRESHOLD: u32 = 4032; // ~four weeks
 		match (inner.balances_empty_height, is_all_funds_claimed, preimages_not_needed_elsewhere) {
 			(Some(balances_empty_height), true, true) => {
 				// Claimed all funds, check if reached the blocks threshold.
-				(current_height >= balances_empty_height + BLOCKS_THRESHOLD, false)
+				(current_height >= balances_empty_height + ARCHIVAL_DELAY_BLOCKS, false)
 			},
 			(Some(_), false, _)|(Some(_), _, false) => {
 				// previously assumed we claimed all funds, but we have new funds to claim or
@@ -2058,7 +2062,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 				// None. It is set to the current block height.
 				log_debug!(logger,
 					"ChannelMonitor funded at {} is now fully resolved. It will become archivable in {} blocks",
-					inner.get_funding_txo().0, BLOCKS_THRESHOLD);
+					inner.get_funding_txo().0, ARCHIVAL_DELAY_BLOCKS);
 				inner.balances_empty_height = Some(current_height);
 				(false, true)
 			},

lightning/src/ln/monitor_tests.rs

@@ -10,7 +10,7 @@
 //! Further functional tests which test blockchain reorganizations.
 
 use crate::sign::{ecdsa::EcdsaChannelSigner, OutputSpender, SpendableOutputDescriptor};
-use crate::chain::channelmonitor::{ANTI_REORG_DELAY, LATENCY_GRACE_PERIOD_BLOCKS, Balance, BalanceSource, ChannelMonitorUpdateStep};
+use crate::chain::channelmonitor::{ANTI_REORG_DELAY, ARCHIVAL_DELAY_BLOCKS,LATENCY_GRACE_PERIOD_BLOCKS, Balance, BalanceSource, ChannelMonitorUpdateStep};
 use crate::chain::transaction::OutPoint;
 use crate::chain::chaininterface::{ConfirmationTarget, LowerBoundedFeeEstimator, compute_feerate_sat_per_1000_weight};
 use crate::events::bump_transaction::{BumpTransactionEvent, WalletSource};
@@ -246,31 +246,31 @@ fn archive_fully_resolved_monitors() {
 
 	// At this point, both nodes have no more `Balance`s, but nodes[0]'s `ChannelMonitor` still
 	// hasn't had the `MonitorEvent` that contains the preimage claimed by the `ChannelManager`.
-	// Thus, calling `archive_fully_resolved_channel_monitors` and waiting 4032 blocks will not
-	// result in the `ChannelMonitor` being archived.
+	// Thus, calling `archive_fully_resolved_channel_monitors` and waiting `ARCHIVAL_DELAY_BLOCKS`
+	// blocks will not result in the `ChannelMonitor` being archived.
 	nodes[0].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[0].chain_monitor.chain_monitor.list_monitors().len(), 1);
-	connect_blocks(&nodes[0], 4032);
+	connect_blocks(&nodes[0], ARCHIVAL_DELAY_BLOCKS);
 	nodes[0].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[0].chain_monitor.chain_monitor.list_monitors().len(), 1);
 
-	// ...however, nodes[1]'s `ChannelMonitor` is ready to be archived, and will be in exactly 4032
-	// blocks.
+	// ...however, nodes[1]'s `ChannelMonitor` is ready to be archived, and will be in exactly
+	// `ARCHIVAL_DELAY_BLOCKS` blocks.
 	nodes[1].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[1].chain_monitor.chain_monitor.list_monitors().len(), 1);
-	connect_blocks(&nodes[1], 4031);
+	connect_blocks(&nodes[1], ARCHIVAL_DELAY_BLOCKS - 1);
 	nodes[1].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[1].chain_monitor.chain_monitor.list_monitors().len(), 1);
 	connect_blocks(&nodes[1], 1);
 	nodes[1].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[1].chain_monitor.chain_monitor.list_monitors().len(), 0);
 
 	// Finally, we process the pending `MonitorEvent` from nodes[0], allowing the `ChannelMonitor`
-	// to be archived 4032 blocks later.
+	// to be archived `ARCHIVAL_DELAY_BLOCKS` blocks later.
 	expect_payment_sent(&nodes[0], payment_preimage, None, true, false);
 	nodes[0].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[0].chain_monitor.chain_monitor.list_monitors().len(), 1);
-	connect_blocks(&nodes[0], 4031);
+	connect_blocks(&nodes[0], ARCHIVAL_DELAY_BLOCKS - 1);
 	nodes[0].chain_monitor.chain_monitor.archive_fully_resolved_channel_monitors();
 	assert_eq!(nodes[0].chain_monitor.chain_monitor.list_monitors().len(), 1);
 	connect_blocks(&nodes[0], 1);