htlcswitch: update CloseLink to accept ideal fee rate

htlcswitch/switch.go

@@ -75,6 +75,12 @@ type ChanClose struct {
 	// ChanPoint represent the id of the channel which should be closed.
 	ChanPoint *wire.OutPoint
 
+	// TargetFeePerKw is the ideal fee that was specified by the caller.
+	// This value is only utilized if the closure type is CloseRegular.
+	// This will be the starting offered fee when the fee negotiation
+	// process for the cooperative closure transaction kicks off.
+	TargetFeePerKw btcutil.Amount
+
 	// Updates is used by request creator to receive the notifications about
 	// execution of the close channel request.
 	Updates chan *lnrpc.CloseStatusUpdate
@@ -599,19 +605,24 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
 	}
 }
 
-// CloseLink creates and sends the close channel command.
+// CloseLink creates and sends the close channel command to the target link
+// directing the specified closure type. If the closure type if CloseRegular,
+// then the last parameter should be the ideal fee-per-kw that will be used as
+// a starting point for close negotiation.
 func (s *Switch) CloseLink(chanPoint *wire.OutPoint,
-	closeType ChannelCloseType) (chan *lnrpc.CloseStatusUpdate, chan error) {
+	closeType ChannelCloseType,
+	targetFeePerKw btcutil.Amount) (chan *lnrpc.CloseStatusUpdate, chan error) {
 
 	// TODO(roasbeef) abstract out the close updates.
 	updateChan := make(chan *lnrpc.CloseStatusUpdate, 2)
 	errChan := make(chan error, 1)
 
 	command := &ChanClose{
-		CloseType: closeType,
-		ChanPoint: chanPoint,
-		Updates:   updateChan,
-		Err:       errChan,
+		CloseType:      closeType,
+		ChanPoint:      chanPoint,
+		Updates:        updateChan,
+		TargetFeePerKw: targetFeePerKw,
+		Err:            errChan,
 	}
 
 	select {