From d0a7765c685aa03df31de34a798c1bf1dece5fa6 Mon Sep 17 00:00:00 2001
From: ziggie <ziggie1984@protonmail.com>
Date: Wed, 24 Jul 2024 14:51:13 +0200
Subject: [PATCH] rpcserver: include fee calc. for psbt flow.

Include the fee calculaltion for the psbt flow. Moreover include
fee rate testing in the itest environment.
---
 itest/lnd_funding_test.go | 16 ++++++++++++++--
 rpcserver.go              | 36 +++++++++++++++---------------------
 2 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/itest/lnd_funding_test.go b/itest/lnd_funding_test.go
index 8f43620ee..6e2f0070c 100644
--- a/itest/lnd_funding_test.go
+++ b/itest/lnd_funding_test.go
@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
 	"github.com/lightningnetwork/lnd/lntest"
 	"github.com/lightningnetwork/lnd/lntest/node"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/stretchr/testify/require"
 )
@@ -968,11 +969,16 @@ func testBatchChanFunding(ht *lntest.HarnessTest) {
 	ht.EnsureConnected(alice, dave)
 	ht.EnsureConnected(alice, eve)
 
+	expectedFeeRate := chainfee.SatPerKWeight(2500)
+
+	// We verify that the channel opening uses the correct fee rate.
+	ht.SetFeeEstimateWithConf(expectedFeeRate, 3)
+
 	// Let's create our batch TX request. This first one should fail as we
 	// open a channel to Carol that is too small for her min chan size.
 	batchReq := &lnrpc.BatchOpenChannelRequest{
-		SatPerVbyte: 12,
-		MinConfs:    1,
+		TargetConf: 3,
+		MinConfs:   1,
 		Channels: []*lnrpc.BatchOpenChannel{{
 			NodePubkey:         bob.PubKey[:],
 			LocalFundingAmount: 100_000,
@@ -1069,6 +1075,12 @@ func testBatchChanFunding(ht *lntest.HarnessTest) {
 	rawTx := ht.GetRawTransaction(txHash)
 	require.Len(ht, rawTx.MsgTx().TxOut, 5)
 
+	// Check the fee rate of the batch-opening transaction. We expect slight
+	// inaccuracies because of the DER signature fee estimation.
+	openingFeeRate := ht.CalculateTxFeeRate(rawTx.MsgTx())
+	require.InEpsilonf(ht, uint64(expectedFeeRate), uint64(openingFeeRate),
+		0.01, "want %v, got %v", expectedFeeRate, openingFeeRate)
+
 	// For calculating the change output index we use the formula for the
 	// sum of consecutive of integers (n(n+1)/2). All the channel point
 	// indexes are known, so we just calculate the difference to get the
diff --git a/rpcserver.go b/rpcserver.go
index 465035ea5..8415eb338 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -2158,30 +2158,24 @@ func (r *rpcServer) parseOpenChannelReq(in *lnrpc.OpenChannelRequest,
 		return nil, fmt.Errorf("cannot open channel to self")
 	}
 
-	var feeRate chainfee.SatPerKWeight
+	// NOTE: We also need to do the fee rate calculation for the psbt
+	// funding flow because the `batchfund` depends on it.
+	targetConf := maybeUseDefaultConf(
+		in.SatPerByte, in.SatPerVbyte, uint32(in.TargetConf),
+	)
 
-	// Skip estimating fee rate for PSBT funding.
-	if in.FundingShim == nil || in.FundingShim.GetPsbtShim() == nil {
-		// Keep the old behavior prior to 0.18.0 - when the user
-		// doesn't set fee rate or conf target, the default conf target
-		// of 6 is used.
-		targetConf := maybeUseDefaultConf(
-			in.SatPerByte, in.SatPerVbyte, uint32(in.TargetConf),
-		)
-
-		// Calculate an appropriate fee rate for this transaction.
-		feeRate, err = lnrpc.CalculateFeeRate(
-			uint64(in.SatPerByte), in.SatPerVbyte,
-			targetConf, r.server.cc.FeeEstimator,
-		)
-		if err != nil {
-			return nil, err
-		}
-
-		rpcsLog.Debugf("[openchannel]: using fee of %v sat/kw for "+
-			"funding tx", int64(feeRate))
+	// Calculate an appropriate fee rate for this transaction.
+	feeRate, err := lnrpc.CalculateFeeRate(
+		uint64(in.SatPerByte), in.SatPerVbyte,
+		targetConf, r.server.cc.FeeEstimator,
+	)
+	if err != nil {
+		return nil, err
 	}
 
+	rpcsLog.Debugf("[openchannel]: using fee of %v sat/kw for "+
+		"funding tx", int64(feeRate))
+
 	script, err := chancloser.ParseUpfrontShutdownAddress(
 		in.CloseAddress, r.cfg.ActiveNetParams.Params,
 	)