From 275814cc1db90b72b2f44272f33cd1346395231a Mon Sep 17 00:00:00 2001
From: Antoine Riard <ariard@student.42.fr>
Date: Mon, 23 Mar 2020 22:17:46 -0400
Subject: [PATCH] Cache remote HTLC inside OnchainTxHandler::RemoteTxCache

As we can't predict if any and which revoked commitment tx is
going to appear onchain we have by design to cache all htlc information
to regenerate htlc script if needed.
---
 lightning/src/ln/channelmonitor.rs |  9 +++++++-
 lightning/src/ln/onchaintx.rs      | 33 ++++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/lightning/src/ln/channelmonitor.rs b/lightning/src/ln/channelmonitor.rs
index 6f00392c2..19db34a70 100644
--- a/lightning/src/ln/channelmonitor.rs
+++ b/lightning/src/ln/channelmonitor.rs
@@ -1193,7 +1193,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		log_trace!(logger, "New potential remote commitment transaction: {}", encode::serialize_hex(unsigned_commitment_tx));
 		self.prev_remote_commitment_txid = self.current_remote_commitment_txid.take();
 		self.current_remote_commitment_txid = Some(new_txid);
-		self.remote_claimable_outpoints.insert(new_txid, htlc_outputs);
+		self.remote_claimable_outpoints.insert(new_txid, htlc_outputs.clone());
 		self.current_remote_commitment_number = commitment_number;
 		//TODO: Merge this into the other per-remote-transaction output storage stuff
 		match self.their_cur_revocation_points {
@@ -1214,6 +1214,13 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 				self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
 			}
 		}
+		let mut htlcs = Vec::with_capacity(htlc_outputs.len());
+		for htlc in htlc_outputs {
+			if htlc.0.transaction_output_index.is_some() {
+				htlcs.push(htlc.0);
+			}
+		}
+		self.onchain_tx_handler.provide_latest_remote_tx(new_txid, htlcs);
 	}
 
 	/// Informs this monitor of the latest local (ie broadcastable) commitment transaction. The
diff --git a/lightning/src/ln/onchaintx.rs b/lightning/src/ln/onchaintx.rs
index eb30f155c..7e84132e4 100644
--- a/lightning/src/ln/onchaintx.rs
+++ b/lightning/src/ln/onchaintx.rs
@@ -17,7 +17,7 @@ use bitcoin::secp256k1::key::PublicKey;
 use ln::msgs::DecodeError;
 use ln::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER, InputMaterial, ClaimRequest};
 use ln::channelmanager::PaymentPreimage;
-use ln::chan_utils::{HTLCType, LocalCommitmentTransaction};
+use ln::chan_utils::{HTLCType, LocalCommitmentTransaction, HTLCOutputInCommitment};
 use chain::chaininterface::{FeeEstimator, BroadcasterInterface, ConfirmationTarget, MIN_RELAY_FEE_SAT_PER_1000_WEIGHT};
 use chain::keysinterface::ChannelKeys;
 use util::logger::Logger;
@@ -52,7 +52,8 @@ enum OnchainEvent {
 /// remote outputs, either justice or preimage/timeout transactions.
 struct RemoteTxCache {
 	remote_delayed_payment_base_key: PublicKey,
-	remote_htlc_base_key: PublicKey
+	remote_htlc_base_key: PublicKey,
+	per_htlc: HashMap<Sha256dHash, Vec<(HTLCOutputInCommitment)>>
 }
 
 /// Higher-level cache structure needed to re-generate bumped claim txn if needed
@@ -251,6 +252,14 @@ impl<ChanSigner: ChannelKeys + Writeable> OnchainTxHandler<ChanSigner> {
 
 		self.remote_tx_cache.remote_delayed_payment_base_key.write(writer)?;
 		self.remote_tx_cache.remote_htlc_base_key.write(writer)?;
+		writer.write_all(&byte_utils::be64_to_array(self.remote_tx_cache.per_htlc.len() as u64))?;
+		for (ref txid, ref htlcs) in self.remote_tx_cache.per_htlc.iter() {
+			writer.write_all(&txid[..])?;
+			writer.write_all(&byte_utils::be64_to_array(htlcs.len() as u64))?;
+			for &ref htlc in htlcs.iter() {
+				htlc.write(writer)?;
+			}
+		}
 		self.remote_csv.write(writer)?;
 
 		self.key_storage.write(writer)?;
@@ -304,9 +313,24 @@ impl<ChanSigner: ChannelKeys + Readable> Readable for OnchainTxHandler<ChanSigne
 		let remote_tx_cache = {
 			let remote_delayed_payment_base_key = Readable::read(reader)?;
 			let remote_htlc_base_key = Readable::read(reader)?;
+			let per_htlc_len: u64 = Readable::read(reader)?;
+			let mut per_htlc = HashMap::with_capacity(cmp::min(per_htlc_len as usize, MAX_ALLOC_SIZE / 64));
+			for _  in 0..per_htlc_len {
+				let txid: Sha256dHash = Readable::read(reader)?;
+				let htlcs_count: u64 = Readable::read(reader)?;
+				let mut htlcs = Vec::with_capacity(cmp::min(htlcs_count as usize, MAX_ALLOC_SIZE / 32));
+				for _ in 0..htlcs_count {
+					let htlc = Readable::read(reader)?;
+					htlcs.push(htlc);
+				}
+				if let Some(_) = per_htlc.insert(txid, htlcs) {
+					return Err(DecodeError::InvalidValue);
+				}
+			}
 			RemoteTxCache {
 				remote_delayed_payment_base_key,
 				remote_htlc_base_key,
+				per_htlc,
 			}
 		};
 		let remote_csv = Readable::read(reader)?;
@@ -382,6 +406,7 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 		let remote_tx_cache = RemoteTxCache {
 			remote_delayed_payment_base_key,
 			remote_htlc_base_key,
+			per_htlc: HashMap::new(),
 		};
 
 		OnchainTxHandler {
@@ -902,6 +927,10 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
 		}
 	}
 
+	pub(super) fn provide_latest_remote_tx(&mut self, commitment_txid: Sha256dHash, htlcs: Vec<HTLCOutputInCommitment>) {
+		self.remote_tx_cache.per_htlc.insert(commitment_txid, htlcs);
+	}
+
 	#[cfg(test)]
 	pub(super) fn get_fully_signed_copy_local_tx(&mut self, funding_redeemscript: &Script) -> Option<Transaction> {
 		if let Some(ref mut local_commitment) = self.local_commitment {
-- 
2.39.5