StaticAddr: Withdraw arbitrary amounts

cmd/loop/staticaddr.go

@@ -148,7 +148,7 @@ 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 			Usage: "the optional address that the withdrawn " +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",
@@ -159,6 +159,12 @@ 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+				"withdrawn from the selected deposits.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,
 }
@@ -198,8 +204,8 @@ 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")
 	}
 
 	resp, err := client.WithdrawDeposits(ctxb,
@@ -208,6 +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

@@ -1541,7 +1541,7 @@ 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.proto

@@ -1623,6 +1623,15 @@ 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+    The amount in satoshis that should be withdrawn from the selected deposits.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 back to the static address. The fees for
+    the transaction are taken from the change output. If the change is below
+    the dust limit, there won't be a change output and the dust goes towards
+    fees.
+    */
+    int64 amount = 5;
 }
 
 message WithdrawDepositsResponse {