Cache remote basepoint in new OnchainTxHandler::RemoteTxCache

Used in next commits to avoid passing script between ChannelMonitor
and OnchainTxHandler. ChannelMonitor duplicata will be removed
in future commits.

Author: Antoine Riard

lightning/src/ln/channelmonitor.rs

@@ -1134,7 +1134,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 			onchain_events_waiting_threshold_conf: HashMap::new(),
 			outputs_to_watch: HashMap::new(),
 
-			onchain_tx_handler: OnchainTxHandler::new(destination_script.clone(), keys, funding_redeemscript, their_to_self_delay, logger.clone()),
+			onchain_tx_handler: OnchainTxHandler::new(destination_script.clone(), keys, funding_redeemscript, their_to_self_delay, their_delayed_payment_base_key.clone(), their_htlc_base_key.clone(), our_to_self_delay, logger.clone()),
 
 			last_block_hash: Default::default(),
 			secp_ctx: Secp256k1::new(),

lightning/src/ln/onchaintx.rs

@@ -11,6 +11,7 @@ use bitcoin::util::bip143;
 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
 
 use secp256k1::{Secp256k1, Signature};
+use secp256k1::key::PublicKey;
 use secp256k1;
 
 use ln::msgs::DecodeError;
@@ -58,6 +59,13 @@ struct HTLCTxCache {
 	per_htlc: HashMap<u32, (HTLCOutputInCommitment, Option<Signature>)>
 }
 
+/// Cache remote basepoint to compute any transaction on
+/// remote outputs, either justice or preimage/timeout transactions.
+struct RemoteTxCache {
+	remote_delayed_payment_base_key: PublicKey,
+	remote_htlc_base_key: PublicKey
+}
+
 /// Higher-level cache structure needed to re-generate bumped claim txn if needed
 #[derive(Clone, PartialEq)]
 pub struct ClaimTxBumpMaterial {
@@ -158,6 +166,8 @@ pub struct OnchainTxHandler<ChanSigner: ChannelKeys> {
 	current_htlc_cache: Option<HTLCTxCache>,
 	prev_htlc_cache: Option<HTLCTxCache>,
 	local_csv: u16,
+	remote_tx_cache: RemoteTxCache,
+	remote_csv: u16,
 
 	key_storage: ChanSigner,
 
@@ -233,6 +243,10 @@ impl<ChanSigner: ChannelKeys + Writeable> OnchainTxHandler<ChanSigner> {
 		}
 		self.local_csv.write(writer)?;
 
+		self.remote_tx_cache.remote_delayed_payment_base_key.write(writer)?;
+		self.remote_tx_cache.remote_htlc_base_key.write(writer)?;
+		self.remote_csv.write(writer)?;
+
 		self.key_storage.write(writer)?;
 
 		writer.write_all(&byte_utils::be64_to_array(self.pending_claim_requests.len() as u64))?;
@@ -319,6 +333,16 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 		};
 		let local_csv = Readable::read(reader)?;
 
+		let remote_tx_cache = {
+			let remote_delayed_payment_base_key = Readable::read(reader)?;
+			let remote_htlc_base_key = Readable::read(reader)?;
+			RemoteTxCache {
+				remote_delayed_payment_base_key,
+				remote_htlc_base_key,
+			}
+		};
+		let remote_csv = Readable::read(reader)?;
+
 		let key_storage = Readable::read(reader)?;
 
 		let pending_claim_requests_len: u64 = Readable::read(reader)?;
@@ -372,6 +396,8 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 			current_htlc_cache,
 			prev_htlc_cache,
 			local_csv,
+			remote_tx_cache,
+			remote_csv,
 			key_storage,
 			claimable_outpoints,
 			pending_claim_requests,
@@ -383,10 +409,15 @@ impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for OnchainTx
 }
 
 impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
-	pub(super) fn new(destination_script: Script, keys: ChanSigner, funding_redeemscript: Script, local_csv: u16, logger: Arc<Logger>) -> Self {
+	pub(super) fn new(destination_script: Script, keys: ChanSigner, funding_redeemscript: Script, local_csv: u16, remote_delayed_payment_base_key: PublicKey, remote_htlc_base_key: PublicKey, remote_csv: u16, logger: Arc<Logger>) -> Self {
 
 		let key_storage = keys;
 
+		let remote_tx_cache = RemoteTxCache {
+			remote_delayed_payment_base_key,
+			remote_htlc_base_key,
+		};
+
 		OnchainTxHandler {
 			destination_script,
 			funding_redeemscript,
@@ -395,6 +426,8 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 			current_htlc_cache: None,
 			prev_htlc_cache: None,
 			local_csv,
+			remote_tx_cache,
+			remote_csv,
 			key_storage,
 			pending_claim_requests: HashMap::new(),
 			claimable_outpoints: HashMap::new(),