multi: replace DefaultDustLimit with script-specific DustLimitForSize

This commit updates call-sites to use the proper dust limits for
various script types. This also updates the default dust limit used
in the funding flow to be 354 satoshis instead of 573 satoshis.

sweep/txgenerator.go

@@ -10,6 +10,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 )
 
@@ -37,8 +38,8 @@ type inputSet []input.Input
 // inputs are skipped. No input sets with a total value after fees below the
 // dust limit are returned.
 func generateInputPartitionings(sweepableInputs []txInput,
-	relayFeePerKW, feePerKW chainfee.SatPerKWeight,
-	maxInputsPerTx int, wallet Wallet) ([]inputSet, error) {
+	feePerKW chainfee.SatPerKWeight, maxInputsPerTx int,
+	wallet Wallet) ([]inputSet, error) {
 
 	// Sort input by yield. We will start constructing input sets starting
 	// with the highest yield inputs. This is to prevent the construction
@@ -85,9 +86,7 @@ func generateInputPartitionings(sweepableInputs []txInput,
 		// Start building a set of positive-yield tx inputs under the
 		// condition that the tx will be published with the specified
 		// fee rate.
-		txInputs := newTxInputSet(
-			wallet, feePerKW, relayFeePerKW, maxInputsPerTx,
-		)
+		txInputs := newTxInputSet(wallet, feePerKW, maxInputsPerTx)
 
 		// From the set of sweepable inputs, keep adding inputs to the
 		// input set until the tx output value no longer goes up or the
@@ -111,10 +110,12 @@ func generateInputPartitionings(sweepableInputs []txInput,
 		// continuing with the remaining inputs will only lead to sets
 		// with an even lower output value.
 		if !txInputs.enoughInput() {
+			// The change output is always a p2wpkh here.
+			dl := lnwallet.DustLimitForSize(input.P2WPKHSize)
 			log.Debugf("Set value %v (r=%v, c=%v) below dust "+
 				"limit of %v", txInputs.totalOutput(),
 				txInputs.requiredOutput, txInputs.changeOutput,
-				txInputs.dustLimit)
+				dl)
 			return sets, nil
 		}
 
@@ -135,8 +136,8 @@ func generateInputPartitionings(sweepableInputs []txInput,
 // sending any leftover change to the change script.
 func createSweepTx(inputs []input.Input, outputs []*wire.TxOut,
 	changePkScript []byte, currentBlockHeight uint32,
-	feePerKw chainfee.SatPerKWeight, dustLimit btcutil.Amount,
-	signer input.Signer) (*wire.MsgTx, error) {
+	feePerKw chainfee.SatPerKWeight, signer input.Signer) (*wire.MsgTx,
+	error) {
 
 	inputs, estimator := getWeightEstimate(inputs, outputs, feePerKw)
 	txFee := estimator.fee()
@@ -227,16 +228,20 @@ func createSweepTx(inputs []input.Input, outputs []*wire.TxOut,
 	// sweep tx has a change output.
 	changeAmt := totalInput - requiredOutput - txFee
 
+	// We'll calculate the dust limit for the given changePkScript since it
+	// is variable.
+	changeLimit := lnwallet.DustLimitForSize(len(changePkScript))
+
 	// The txn will sweep the amount after fees to the pkscript generated
 	// above.
-	if changeAmt >= dustLimit {
+	if changeAmt >= changeLimit {
 		sweepTx.AddTxOut(&wire.TxOut{
 			PkScript: changePkScript,
 			Value:    int64(changeAmt),
 		})
 	} else {
 		log.Infof("Change amt %v below dustlimit %v, not adding "+
-			"change output", changeAmt, dustLimit)
+			"change output", changeAmt, changeLimit)
 	}
 
 	// We'll default to using the current block height as locktime, if none