Add manual-funding broadcast tracking to ChannelMonitor

Adds `is_manual_broadcast` and `funding_seen_onchain` flags to track whether the channel uses manual funding broadcasts and whether we've seen the funding tx confirm. This enables deferring holder commitment broadcasts until after the funding tx is actually broadcast. For example, in LSPS2 with client_trusts_lsp=true, the LSP may defer broadcasting the funding tx until the client claims an HTLC, so we need to avoid broadcasting commitments that reference outputs that don't exist yet.

Author: martinsaposnic

lightning/src/chain/channelmonitor.rs

@@ -1202,6 +1202,19 @@ pub(crate) struct ChannelMonitorImpl<Signer: EcdsaChannelSigner> {
 funding: FundingScope,
 pending_funding: Vec<FundingScope>,
 
+/// True if this channel was configured for manual funding broadcasts. Monitors written by
+/// versions prior to LDK 0.2 load with `false` until a new update persists it.
+is_manual_broadcast: bool,
+/// True once we've observed either funding transaction on-chain. Older monitors prior to LDK 0.2
+/// assume this is `true` when absent during upgrade so holder broadcasts aren't gated unexpectedly.
+/// In manual-broadcast channels we also use this to trigger deferred holder
+/// broadcasts once the funding transaction finally appears on-chain.
+///
+/// Note: This tracks whether the funding transaction was ever broadcast, not whether it is
+/// currently confirmed. It is never reset, even if the funding transaction is unconfirmed due
+/// to a reorg.
+funding_seen_onchain: bool,
+
 latest_update_id: u64,
 commitment_transaction_number_obscure_factor: u64,
 
@@ -1740,6 +1753,8 @@ pub(crate) fn write_chanmon_internal<Signer: EcdsaChannelSigner, W: Writer>(
 (32, channel_monitor.pending_funding, optional_vec),
 (33, channel_monitor.htlcs_resolved_to_user, required),
 (34, channel_monitor.alternative_funding_confirmed, option),
+(35, channel_monitor.is_manual_broadcast, required),
+(37, channel_monitor.funding_seen_onchain, required),
 });
 
 Ok(())
@@ -1868,6 +1883,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 commitment_transaction_number_obscure_factor: u64,
 initial_holder_commitment_tx: HolderCommitmentTransaction, best_block: BestBlock,
 counterparty_node_id: PublicKey, channel_id: ChannelId,
+is_manual_broadcast: bool,
 ) -> ChannelMonitor<Signer> {
 
 assert!(commitment_transaction_number_obscure_factor <= (1 << 48));
@@ -1914,6 +1930,9 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 },
 pending_funding: vec![],
 
+is_manual_broadcast,
+funding_seen_onchain: false,
+
 latest_update_id: 0,
 commitment_transaction_number_obscure_factor,
 
@@ -6562,6 +6581,8 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 let mut channel_parameters = None;
 let mut pending_funding = None;
 let mut alternative_funding_confirmed = None;
+let mut is_manual_broadcast = RequiredWrapper(None);
+let mut funding_seen_onchain = RequiredWrapper(None);
 read_tlv_fields!(reader, {
 (1, funding_spend_confirmed, option),
 (3, htlcs_resolved_on_chain, optional_vec),
@@ -6582,6 +6603,8 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 (32, pending_funding, optional_vec),
 (33, htlcs_resolved_to_user, option),
 (34, alternative_funding_confirmed, option),
+(35, is_manual_broadcast, (default_value, false)),
+(37, funding_seen_onchain, (default_value, true)),
 });
 // 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.
@@ -6695,6 +6718,10 @@ impl<'a, 'b, ES: EntropySource, SP: SignerProvider> ReadableArgs<(&'a ES, &'b SP
 prev_holder_commitment_tx,
 },
 pending_funding: pending_funding.unwrap_or(vec![]),
+is_manual_broadcast: is_manual_broadcast.0.unwrap(),
+// Older monitors prior to LDK 0.2 assume this is `true` when absent
+// during upgrade so holder broadcasts aren't gated unexpectedly.
+funding_seen_onchain: funding_seen_onchain.0.unwrap(),
 
 latest_update_id,
 commitment_transaction_number_obscure_factor,

lightning/src/ln/channel.rs

@@ -3196,6 +3196,7 @@ where
 funding.get_holder_selected_contest_delay(), &context.destination_script,
 &funding.channel_transaction_parameters, funding.is_outbound(), obscure_factor,
 holder_commitment_tx, best_block, context.counterparty_node_id, context.channel_id(),
+context.is_manual_broadcast,
 );
 channel_monitor.provide_initial_counterparty_commitment_tx(
 counterparty_initial_commitment_tx.clone(),