ChannelMonitor: track user-processed payment claims

When an Event::PaymentClaimed is processed by the user, we need to track that
so we don't keep regenerating the event redundantly on startup. Here we add a
map to claims in this state, similar to the existing htlcs_resolved_to_user map.

Note that this map will only be updated for closed channels -- if the channel
is open, the inbound payment is pruned automatically when the HTLC is no longer
present in any unrevoked commitment transaction, which stops the redundant
event regeneration.

Upcoming commits will add the actual tracking that uses this map, as well
as generating the relevant monitor update to trigger this tracking

Author: valentinewallace

lightning/src/chain/channelmonitor.rs

@@ -1357,6 +1357,10 @@ pub(crate) struct ChannelMonitorImpl<Signer: EcdsaChannelSigner> {
 	/// this and we'll store the set of fully resolved payments here.
 	htlcs_resolved_to_user: HashSet<SentHTLCId>,
 
+	/// The set of inbound payments for which the user has processed an [`Event::PaymentClaimed`].
+	/// This is used to avoid regenerating the event redundantly on restart for closed channels.
+	inbound_payments_claimed: HashSet<PaymentHash>,
+
 	/// The set of `SpendableOutput` events which we have already passed upstream to be claimed.
 	/// These are tracked explicitly to ensure that we don't generate the same events redundantly
 	/// if users duplicatively confirm old transactions. Specifically for transactions claiming a
@@ -1770,6 +1774,7 @@ pub(crate) fn write_chanmon_internal<Signer: EcdsaChannelSigner, W: Writer>(
 		(34, channel_monitor.alternative_funding_confirmed, option),
 		(35, channel_monitor.is_manual_broadcast, required),
 		(37, channel_monitor.funding_seen_onchain, required),
+		(39, channel_monitor.inbound_payments_claimed, required),
 	});
 
 	Ok(())
@@ -1969,6 +1974,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 			confirmed_commitment_tx_counterparty_output: None,
 			htlcs_resolved_on_chain: Vec::new(),
 			htlcs_resolved_to_user: new_hash_set(),
+			inbound_payments_claimed: new_hash_set(),
 			spendable_txids_confirmed: Vec::new(),
 
 			best_block,
@@ -6523,6 +6529,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 		let mut funding_spend_confirmed = None;
 		let mut htlcs_resolved_on_chain = Some(Vec::new());
 		let mut htlcs_resolved_to_user = Some(new_hash_set());
+		let mut inbound_payments_claimed = Some(new_hash_set());
 		let mut funding_spend_seen = Some(false);
 		let mut counterparty_node_id = None;
 		let mut confirmed_commitment_tx_counterparty_output = None;
@@ -6562,6 +6569,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 			(34, alternative_funding_confirmed, option),
 			(35, is_manual_broadcast, (default_value, false)),
 			(37, funding_seen_onchain, (default_value, true)),
+			(39, inbound_payments_claimed, option),
 		});
 		// Note that `payment_preimages_with_info` was added (and is always written) in LDK 0.1, so
 		// we can use it to determine if this monitor was last written by LDK 0.1 or later.
@@ -6727,6 +6735,7 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 			confirmed_commitment_tx_counterparty_output,
 			htlcs_resolved_on_chain: htlcs_resolved_on_chain.unwrap(),
 			htlcs_resolved_to_user: htlcs_resolved_to_user.unwrap(),
+			inbound_payments_claimed: inbound_payments_claimed.unwrap(),
 			spendable_txids_confirmed: spendable_txids_confirmed.unwrap(),
 
 			best_block,