Track historical SCIDs from previous funding

When a splice is locked, the SCID from the previous funding transaction
needs to be remembered so that pending HTLCs can be handled properly.
Additionally, when they need to be cleaned up once they should no longer
be used. Track these SCIDs as splices are locked and clean any up as
blocks are connected.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -2233,6 +2233,10 @@ pub(super) struct ChannelContext<SP: Deref> where SP::Target: SignerProvider {
 	// blinded paths instead of simple scid+node_id aliases.
 	outbound_scid_alias: u64,
 
+	/// Short channel ids used by any prior FundingScope. These are maintained such that
+	/// ChannelManager can look up the channel for any pending HTLCs.
+	pub historical_scids: Vec<u64>,
+
 	// We track whether we already emitted a `ChannelPending` event.
 	channel_pending_event_emitted: bool,
 
@@ -3045,6 +3049,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
 
 			latest_inbound_scid_alias: None,
 			outbound_scid_alias: 0,
+			historical_scids: Vec::new(),
 
 			channel_pending_event_emitted: false,
 			funding_tx_broadcast_safe_event_emitted: false,
@@ -3281,6 +3286,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
 
 			latest_inbound_scid_alias: None,
 			outbound_scid_alias,
+			historical_scids: Vec::new(),
 
 			channel_pending_event_emitted: false,
 			funding_tx_broadcast_safe_event_emitted: false,
@@ -5301,6 +5307,9 @@ pub(super) struct FundedChannel<SP: Deref> where SP::Target: SignerProvider {
 #[cfg(splicing)]
 macro_rules! promote_splice_funding {
 	($self: expr, $funding: expr) => {
+		if let Some(scid) = $self.funding.short_channel_id {
+			$self.context.historical_scids.push(scid);
+		}
 		core::mem::swap(&mut $self.funding, $funding);
 		$self.pending_splice = None;
 		$self.pending_funding.clear();
@@ -11264,6 +11273,7 @@ impl<SP: Deref> Writeable for FundedChannel<SP> where SP::Target: SignerProvider
 			(54, self.pending_funding, optional_vec), // Added in 0.2
 			(55, removed_htlc_failure_attribution_data, optional_vec), // Added in 0.2
 			(57, holding_cell_failure_attribution_data, optional_vec), // Added in 0.2
+			(58, self.context.historical_scids, optional_vec), // Added in 0.2
 		});
 
 		Ok(())
@@ -11579,6 +11589,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, &'c Channel
 		let mut is_manual_broadcast = None;
 
 		let mut pending_funding = Some(Vec::new());
+		let mut historical_scids = Some(Vec::new());
 
 		read_tlv_fields!(reader, {
 			(0, announcement_sigs, option),
@@ -11618,6 +11629,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, &'c Channel
 			(54, pending_funding, optional_vec), // Added in 0.2
 			(55, removed_htlc_failure_attribution_data, optional_vec),
 			(57, holding_cell_failure_attribution_data, optional_vec),
+			(58, historical_scids, optional_vec), // Added in 0.2
 		});
 
 		let holder_signer = signer_provider.derive_channel_signer(channel_keys_id);
@@ -11894,6 +11906,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, &'c Channel
 				latest_inbound_scid_alias,
 				// Later in the ChannelManager deserialization phase we scan for channels and assign scid aliases if its missing
 				outbound_scid_alias,
+				historical_scids: historical_scids.unwrap(),
 
 				funding_tx_broadcast_safe_event_emitted: funding_tx_broadcast_safe_event_emitted.unwrap_or(false),
 				channel_pending_event_emitted: channel_pending_event_emitted.unwrap_or(true),

lightning/src/ln/channelmanager.rs

@@ -82,7 +82,7 @@ use crate::sign::{EntropySource, NodeSigner, Recipient, SignerProvider};
 use crate::sign::ecdsa::EcdsaChannelSigner;
 use crate::util::config::{ChannelConfig, ChannelConfigUpdate, ChannelConfigOverrides, UserConfig};
 use crate::util::wakers::{Future, Notifier};
-use crate::util::scid_utils::fake_scid;
+use crate::util::scid_utils::{block_from_scid, fake_scid};
 use crate::util::string::UntrustedString;
 use crate::util::ser::{BigSize, FixedLengthReader, LengthReadable, Readable, ReadableArgs, MaybeReadable, Writeable, Writer, VecWriter};
 use crate::util::logger::{Level, Logger, WithContext};
@@ -3068,6 +3068,9 @@ macro_rules! locked_close_channel {
 			debug_assert!(alias_removed);
 		}
 		short_to_chan_info.remove(&$channel_context.outbound_scid_alias());
+		for scid in &$channel_context.historical_scids {
+			short_to_chan_info.remove(scid);
+		}
 	}}
 }
 
@@ -11686,6 +11689,17 @@ where
 					channel.check_for_stale_feerate(&logger, feerate)?;
 				}
 			}
+
+			// Remove any scids used by old splice funding transactions
+			let mut short_to_chan_info = self.short_to_chan_info.write().unwrap();
+			channel.context.historical_scids.retain(|scid| {
+				let retain_scid = block_from_scid(*scid) + 12 > height;
+				if !retain_scid {
+					short_to_chan_info.remove(scid);
+				}
+				retain_scid
+			});
+
 			channel.best_block_updated(height, header.time, self.chain_hash, &self.node_signer, &self.default_configuration, &&WithChannelContext::from(&self.logger, &channel.context, None))
 		});
 
@@ -13976,6 +13990,11 @@ where
 					if let Some(short_channel_id) = channel.funding.get_short_channel_id() {
 						short_to_chan_info.insert(short_channel_id, (channel.context.get_counterparty_node_id(), channel.context.channel_id()));
 					}
+
+					for short_channel_id in &channel.context.historical_scids {
+						short_to_chan_info.insert(*short_channel_id, (channel.context.get_counterparty_node_id(), channel.context.channel_id()));
+					}
+
 					per_peer_state.entry(channel.context.get_counterparty_node_id())
 						.or_insert_with(|| Mutex::new(empty_peer_state()))
 						.get_mut().unwrap()