From: Matt Corallo <git@bluematt.me>
Date: Sat, 26 Jun 2021 17:21:33 +0000 (+0000)
Subject: Use a reasonable target fee when opening channels
X-Git-Url: http://git.bitcoin.ninja/index.cgi?p=ldk-sample;a=commitdiff_plain;h=5acf6fb775b9fdbf617b64060004d5a9895e56df

Use a reasonable target fee when opening channels

Bitcoin Core defaults to conservative fee estimation, which often
results in significant overtargeting on weekends. We also disable
RBF, here, though, with a comment describing how clients should
handle funding RBF.
---

diff --git a/src/bitcoind_client.rs b/src/bitcoind_client.rs
index 90552d9..fd21b59 100644
--- a/src/bitcoind_client.rs
+++ b/src/bitcoind_client.rs
@@ -187,7 +187,19 @@ impl BitcoindClient {
 		let mut rpc = self.bitcoind_rpc_client.lock().await;
 
 		let raw_tx_json = serde_json::json!(raw_tx.0);
-		rpc.call_method("fundrawtransaction", &[raw_tx_json]).await.unwrap()
+		let options = serde_json::json!({
+			// LDK gives us feerates in satoshis per KW but Bitcoin Core here expects fees
+			// denominated in satoshis per vB. First we need to multiply by 4 to convert weight
+			// units to virtual bytes, then divide by 1000 to convert KvB to vB.
+			"fee_rate": self.get_est_sat_per_1000_weight(ConfirmationTarget::Normal) as f64 / 250.0,
+			// While users could "cancel" a channel open by RBF-bumping and paying back to
+			// themselves, we don't allow it here as its easy to have users accidentally RBF bump
+			// and pay to the channel funding address, which results in loss of funds. Real
+			// LDK-based applications should enable RBF bumping and RBF bump either to a local
+			// change address or to a new channel output negotiated with the same node.
+			"replaceable": false,
+		});
+		rpc.call_method("fundrawtransaction", &[raw_tx_json, options]).await.unwrap()
 	}
 
 	pub async fn send_raw_transaction(&self, raw_tx: RawTx) {