From d94eca44f4e59efcfa3f709cfa4696ae8663ea77 Mon Sep 17 00:00:00 2001
From: Elias Rohrer <dev@tnull.de>
Date: Mon, 22 May 2023 12:42:24 +0200
Subject: [PATCH] f Account for nLockTime given in `spend_spendable_outputs`

While we're here we also set the locktime for the funding transaction
---
 src/event.rs  | 14 +++++++++++++-
 src/wallet.rs | 12 +++++++++---
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/event.rs b/src/event.rs
index d02634d9b..c92661af4 100644
--- a/src/event.rs
+++ b/src/event.rs
@@ -22,7 +22,7 @@ use lightning::util::errors::APIError;
 use lightning::util::ser::{Readable, ReadableArgs, Writeable, Writer};
 
 use bitcoin::secp256k1::{PublicKey, Secp256k1};
-use bitcoin::OutPoint;
+use bitcoin::{LockTime, OutPoint, PackedLockTime};
 use rand::{thread_rng, Rng};
 use std::collections::VecDeque;
 use std::ops::Deref;
@@ -292,11 +292,16 @@ where
 				// channel.
 				let confirmation_target = ConfirmationTarget::Normal;
 
+				// We set nLockTime to the current height to discourage fee sniping.
+				let cur_height = self.channel_manager.current_best_block().height();
+				let locktime = LockTime::from_height(cur_height).unwrap_or(LockTime::ZERO);
+
 				// Sign the final funding transaction and broadcast it.
 				match self.wallet.create_funding_transaction(
 					output_script,
 					channel_value_satoshis,
 					confirmation_target,
+					locktime,
 				) {
 					Ok(final_tx) => {
 						// Give the funding transaction back to LDK for opening the channel.
@@ -552,13 +557,20 @@ where
 				let output_descriptors = &outputs.iter().collect::<Vec<_>>();
 				let tx_feerate =
 					self.wallet.get_est_sat_per_1000_weight(ConfirmationTarget::Normal);
+
+				// We set nLockTime to the current height to discourage fee sniping.
+				let cur_height = self.channel_manager.current_best_block().height();
+				let locktime: PackedLockTime =
+					LockTime::from_height(cur_height).map_or(PackedLockTime::ZERO, |l| l.into());
 				let res = self.keys_manager.spend_spendable_outputs(
 					output_descriptors,
 					Vec::new(),
 					destination_address.script_pubkey(),
 					tx_feerate,
+					Some(locktime),
 					&Secp256k1::new(),
 				);
+
 				match res {
 					Ok(spending_tx) => self.wallet.broadcast_transactions(&[&spending_tx]),
 					Err(err) => {
diff --git a/src/wallet.rs b/src/wallet.rs
index d7eb0f3c7..57dd4dc38 100644
--- a/src/wallet.rs
+++ b/src/wallet.rs
@@ -22,7 +22,7 @@ use bitcoin::bech32::u5;
 use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::ecdsa::{RecoverableSignature, Signature};
 use bitcoin::secp256k1::{PublicKey, Scalar, Secp256k1, Signing};
-use bitcoin::{Script, Transaction, TxOut, Txid};
+use bitcoin::{LockTime, PackedLockTime, Script, Transaction, TxOut, Txid};
 
 use std::collections::HashMap;
 use std::sync::{Arc, Condvar, Mutex, RwLock};
@@ -157,13 +157,18 @@ where
 
 	pub(crate) fn create_funding_transaction(
 		&self, output_script: Script, value_sats: u64, confirmation_target: ConfirmationTarget,
+		locktime: LockTime,
 	) -> Result<Transaction, Error> {
 		let fee_rate = self.estimate_fee_rate(confirmation_target);
 
 		let locked_wallet = self.inner.lock().unwrap();
 		let mut tx_builder = locked_wallet.build_tx();
 
-		tx_builder.add_recipient(output_script, value_sats).fee_rate(fee_rate).enable_rbf();
+		tx_builder
+			.add_recipient(output_script, value_sats)
+			.fee_rate(fee_rate)
+			.nlocktime(locktime)
+			.enable_rbf();
 
 		let mut psbt = match tx_builder.finish() {
 			Ok((psbt, _)) => {
@@ -363,7 +368,7 @@ where
 	pub fn spend_spendable_outputs<C: Signing>(
 		&self, descriptors: &[&SpendableOutputDescriptor], outputs: Vec<TxOut>,
 		change_destination_script: Script, feerate_sat_per_1000_weight: u32,
-		secp_ctx: &Secp256k1<C>,
+		locktime: Option<PackedLockTime>, secp_ctx: &Secp256k1<C>,
 	) -> Result<Transaction, ()> {
 		let only_non_static = &descriptors
 			.iter()
@@ -375,6 +380,7 @@ where
 			outputs,
 			change_destination_script,
 			feerate_sat_per_1000_weight,
+			locktime,
 			secp_ctx,
 		)
 	}