Implement anti-fee sniping on funding tx

I.e., set `nLockTime` to current block height

Author: tnull

src/event.rs

@@ -297,6 +297,7 @@ 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);
 
@@ -574,6 +575,7 @@ where
 					Some(locktime),
 					&Secp256k1::new(),
 				);
+
 				match res {
 					Ok(spending_tx) => self.wallet.broadcast_transactions(&[&spending_tx]),
 					Err(err) => {

src/wallet.rs

@@ -24,7 +24,7 @@ use bitcoin::bech32::u5;
 use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::ecdsa::{RecoverableSignature, Signature};
 use bitcoin::secp256k1::{PublicKey, Scalar, Secp256k1, Signing};
-use bitcoin::{PackedLockTime, LockTime, Script, Transaction, TxOut, Txid};
+use bitcoin::{LockTime, PackedLockTime, Script, Transaction, TxOut, Txid};
 
 use std::collections::HashMap;
 use std::sync::{Arc, Condvar, Mutex, RwLock};
@@ -158,14 +158,19 @@ where
 	}
 
 	pub(crate) fn create_funding_transaction(
-		&self, output_script: Script, value_sats: u64, confirmation_target: ConfirmationTarget, locktime: LockTime,
+		&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).nlocktime(locktime).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, _)) => {