all withdrawal amount changes

Author: hieblmi

cmd/loop/staticaddr.go

@@ -143,7 +143,7 @@ var withdrawalCommand = cli.Command{
 			Usage: "withdraws all static address deposits.",
 		},
 		cli.StringFlag{
-			Name: "addr",
+			Name: "dest_addr",
 			Usage: "the optional address that the withdrawn " +
 				"funds should be sent to, if let blank the " +
 				"funds will go to lnd's wallet",
@@ -154,6 +154,12 @@ var withdrawalCommand = cli.Command{
 				"sat/vbyte that should be used when crafting " +
 				"the transaction",
 		},
+		cli.IntFlag{
+			Name: "amount",
+			Usage: "the number of satoshis that should be " +
+				"withdrawn from the selected deposits. The " +
+				"change is sent back to the static address",
+		},
 	},
 	Action: withdraw,
 }
@@ -193,8 +199,13 @@ func withdraw(ctx *cli.Context) error {
 		return fmt.Errorf("unknown withdrawal request")
 	}
 
-	if ctx.IsSet("addr") {
-		destAddr = ctx.String("addr")
+	if ctx.IsSet("dest_addr") {
+		destAddr = ctx.String("dest_addr")
+	}
+
+	if ctx.IsSet("change_addr") && !ctx.IsSet("amount") {
+		return errors.New("change address can only be set if an " +
+			"amount is selected")
 	}
 
 	resp, err := client.WithdrawDeposits(ctxb,
@@ -203,6 +214,7 @@ func withdraw(ctx *cli.Context) error {
 			All:         isAllSelected,
 			DestAddr:    destAddr,
 			SatPerVbyte: int64(ctx.Uint64("sat_per_vbyte")),
+			Amount:      ctx.Int64("amount"),
 		})
 	if err != nil {
 		return err

loopd/swapclient_server.go

@@ -1447,7 +1447,7 @@ func (s *swapClientServer) WithdrawDeposits(ctx context.Context,
 	}
 
 	txhash, pkScript, err := s.withdrawalManager.DeliverWithdrawalRequest(
-		ctx, outpoints, req.DestAddr, req.SatPerVbyte,
+		ctx, outpoints, req.DestAddr, req.SatPerVbyte, req.Amount,
 	)
 	if err != nil {
 		return nil, err

looprpc/client.pb.go

@@ -1592,6 +1592,16 @@ message WithdrawDepositsRequest {
     The fee rate in sat/vbyte to use for the withdrawal transaction.
     */
     int64 sat_per_vbyte = 4;
+
+    /*
+    The amount in satoshis that should be withdrawn from the selected deposits.
+    If there is change, it will be sent to the change address, if specified, and
+    to an internal wallet address otherwise. The fees for the transaction are
+    taken out from the change output, and if not fully covered, the rest will be
+    taken from the withdrawn amount. If the change is below the dust amount, it
+    will be added to the miner fee.
+    */
+    int64 amount = 5;
 }
 
 message WithdrawDepositsResponse {

looprpc/client.proto

@@ -75,6 +75,7 @@ type newWithdrawalRequest struct {
 	respChan    chan *newWithdrawalResponse
 	destAddr    string
 	satPerVbyte int64
+	amount      int64
 }
 
 // newWithdrawalResponse is used to return withdrawal info and error to the
@@ -156,10 +157,10 @@ func (m *Manager) Run(ctx context.Context, currentHeight uint32) error {
 					err)
 			}
 
-		case request := <-m.newWithdrawalRequestChan:
+		case req := <-m.newWithdrawalRequestChan:
 			txHash, pkScript, err = m.WithdrawDeposits(
-				ctx, request.outpoints, request.destAddr,
-				request.satPerVbyte,
+				ctx, req.outpoints, req.destAddr,
+				req.satPerVbyte, req.amount,
 			)
 			if err != nil {
 				log.Errorf("Error withdrawing deposits: %v",
@@ -174,7 +175,7 @@ func (m *Manager) Run(ctx context.Context, currentHeight uint32) error {
 				err:                err,
 			}
 			select {
-			case request.respChan <- resp:
+			case req.respChan <- resp:
 
 			case <-ctx.Done():
 				// Notify subroutines that the main loop has
@@ -261,8 +262,8 @@ func (m *Manager) WaitInitComplete() {
 
 // WithdrawDeposits starts a deposits withdrawal flow.
 func (m *Manager) WithdrawDeposits(ctx context.Context,
-	outpoints []wire.OutPoint, destAddr string, satPerVbyte int64) (string,
-	string, error) {
+	outpoints []wire.OutPoint, destAddr string, satPerVbyte int64,
+	amount int64) (string, string, error) {
 
 	if len(outpoints) == 0 {
 		return "", "", fmt.Errorf("no outpoints selected to " +
@@ -272,7 +273,8 @@ func (m *Manager) WithdrawDeposits(ctx context.Context,
 	// Ensure that the deposits are in a state in which they can be
 	// withdrawn.
 	deposits, allActive := m.cfg.DepositManager.AllOutpointsActiveDeposits(
-		outpoints, deposit.Deposited)
+		outpoints, deposit.Deposited,
+	)
 
 	if !allActive {
 		return "", "", ErrWithdrawingInactiveDeposits
@@ -302,8 +304,27 @@ func (m *Manager) WithdrawDeposits(ctx context.Context,
 		}
 	}
 
+	if amount > 0 {
+		// Check that the amount is within the range of the deposits.
+		totalValue := withdrawalValue(m.toPrevOuts(deposits, nil))
+		if amount > int64(totalValue) {
+			return "", "", fmt.Errorf("amount to withdraw is " +
+				"greater than the total value of the " +
+				"deposits selected")
+		}
+
+		// We'll hint the user if the remaining amount is below the dust
+		// limit and hence will go towards miner fees.
+		dustLimit := lnwallet.DustLimitForSize(input.P2TRSize)
+		if totalValue-btcutil.Amount(amount) < dustLimit {
+			log.Warnf("The remaining amount after withdrawal is "+
+				"below the dust limit of %v and will go "+
+				"towards miner fees", dustLimit)
+		}
+	}
+
 	finalizedTx, err := m.createFinalizedWithdrawalTx(
-		ctx, deposits, withdrawalAddress, satPerVbyte,
+		ctx, deposits, withdrawalAddress, satPerVbyte, amount,
 	)
 	if err != nil {
 		return "", "", err
@@ -355,7 +376,7 @@ func (m *Manager) WithdrawDeposits(ctx context.Context,
 
 func (m *Manager) createFinalizedWithdrawalTx(ctx context.Context,
 	deposits []*deposit.Deposit, withdrawalAddress btcutil.Address,
-	satPerVbyte int64) (*wire.MsgTx, error) {
+	satPerVbyte int64, amount int64) (*wire.MsgTx, error) {
 
 	// Create a musig2 session for each deposit.
 	withdrawalSessions, clientNonces, err := m.createMusig2Sessions(
@@ -387,6 +408,7 @@ func (m *Manager) createFinalizedWithdrawalTx(ctx context.Context,
 			ClientNonces:    clientNonces,
 			ClientSweepAddr: withdrawalAddress.String(),
 			TxFeeRate:       uint64(withdrawalSweepFeeRate),
+			Amount:          amount,
 		},
 	)
 	if err != nil {
@@ -814,13 +836,14 @@ func (m *Manager) republishWithdrawals(ctx context.Context) error {
 // DeliverWithdrawalRequest forwards a withdrawal request to the manager main
 // loop.
 func (m *Manager) DeliverWithdrawalRequest(ctx context.Context,
-	outpoints []wire.OutPoint, destAddr string, satPerVbyte int64) (string,
-	string, error) {
+	outpoints []wire.OutPoint, destAddr string, satPerVbyte int64,
+	amount int64) (string, string, error) {
 
 	request := newWithdrawalRequest{
 		outpoints:   outpoints,
 		destAddr:    destAddr,
 		satPerVbyte: satPerVbyte,
+		amount:      amount,
 		respChan:    make(chan *newWithdrawalResponse),
 	}