rpc: add fee rate arg for finalize and send calls

Author: jharveyb

rpcserver.go

@@ -42,6 +42,7 @@ import (
 	"github.com/lightninglabs/taproot-assets/universe"
 	"github.com/lightningnetwork/lnd/build"
 	"github.com/lightningnetwork/lnd/keychain"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/signal"
 	"google.golang.org/grpc"
 )
@@ -443,12 +444,39 @@ func (r *rpcServer) MintAsset(ctx context.Context,
 	}
 }
 
+// checkFeeRateSanity ensures that the provided fee rate is above the same
+// minimum fee used as a floor in the fee estimator.
+func checkFeeRateSanity(rpcFeeRate uint32) (*chainfee.SatPerKWeight, error) {
+	var feeRate *chainfee.SatPerKWeight
+	switch {
+	// No manual fee rate was set, which is the default.
+	case rpcFeeRate == 0:
+
+	// A manual fee was set but is below a reasonable floor.
+	case rpcFeeRate < uint32(chainfee.FeePerKwFloor):
+		return nil, fmt.Errorf("manual fee rate %d below floor of %d",
+			rpcFeeRate, uint32(chainfee.FeePerKwFloor))
+
+	default:
+		// Set the fee rate for this transaction.
+		manualFeeRate := chainfee.SatPerKWeight(rpcFeeRate)
+		feeRate = &manualFeeRate
+	}
+
+	return feeRate, nil
+}
+
 // FinalizeBatch attempts to finalize the current pending batch.
 func (r *rpcServer) FinalizeBatch(_ context.Context,
 	req *mintrpc.FinalizeBatchRequest) (*mintrpc.FinalizeBatchResponse,
 	error) {
 
-	batch, err := r.cfg.AssetMinter.FinalizeBatch()
+	feeRate, err := checkFeeRateSanity(req.FeeRate)
+	if err != nil {
+		return nil, err
+	}
+
+	batch, err := r.cfg.AssetMinter.FinalizeBatch(feeRate)
 	if err != nil {
 		return nil, fmt.Errorf("unable to finalize batch: %w", err)
 	}
@@ -1961,8 +1989,13 @@ func (r *rpcServer) SendAsset(_ context.Context,
 		}
 	}
 
+	feeRate, err := checkFeeRateSanity(req.FeeRate)
+	if err != nil {
+		return nil, err
+	}
+
 	resp, err := r.cfg.ChainPorter.RequestShipment(
-		tapfreighter.NewAddressParcel(tapAddrs...),
+		tapfreighter.NewAddressParcel(feeRate, tapAddrs...),
 	)
 	if err != nil {
 		return nil, err

taprpc/mintrpc/mint.pb.go

@@ -128,6 +128,9 @@ message FinalizeBatchRequest {
     possibly printed on the command line in the case of a very large batch.
     */
     bool short_response = 1;
+
+    // The optional fee rate to use for the minting transaction, in sat/kw.
+    uint32 fee_rate = 2;
 }
 
 message FinalizeBatchResponse {

taprpc/mintrpc/mint.proto

@@ -191,6 +191,11 @@
         "short_response": {
           "type": "boolean",
           "description": "If true, then the assets currently in the batch won't be returned in the\nresponse. This is mainly to avoid a lot of data being transmitted and\npossibly printed on the command line in the case of a very large batch."
+        },
+        "fee_rate": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The optional fee rate to use for the minting transaction, in sat/kw."
         }
       }
     },