rpcserver+order: remove funding shim on subsequent prepare

Because we have to always expect an OrderMatchPrepare to be sent
multiple times, we need to make sure we clean up our funding shims from
the previous pending batch.

order/manager.go

@@ -275,13 +275,15 @@ func (m *Manager) OrderMatchValidate(batch *Batch) error {
 	// it in case it ends up being the final version.
 	err := m.batchVerifier.Verify(batch)
 	if err != nil {
+		// This error will lead to us sending an OrderMatchReject
+		// message and canceling all funding shims we might already have
+		// set up.
 		return fmt.Errorf("error validating batch: %v", err)
 	}
 
 	m.pendingBatch = batch
 	atomic.StoreUint32(&m.hasPendingBatch, 1)
 
-	// TODO: cancel funding shim of previous pending batch if not nil
 	return nil
 }
 

rpcserver.go

@@ -753,6 +753,30 @@ func (s *rpcServer) handleServerMessage(rpcMsg *clmrpc.ServerAuctionMessage) err
 		rpcLog.Infof("Received PrepareMsg for batch=%x, num_orders=%v",
 			batch.ID[:], len(batch.MatchedOrders))
 
+		// The prepare message can be sent over and over again if the
+		// batch needs adjustment. Clear all previous shims.
+		if s.orderManager.HasPendingBatch() {
+			pendingBatch := s.orderManager.PendingBatch()
+			err := pendingBatch.CancelPendingFundingShims(
+				s.lndClient,
+				func(o order.Nonce) (order.Order, error) {
+					return s.server.db.GetOrder(o)
+				},
+			)
+			if err != nil {
+				// We can't accept the batch, something went
+				// wrong.
+				rpcLog.Errorf("Error clearing previous batch: "+
+					"%v", err)
+				return s.sendRejectBatch(batch, err)
+			}
+
+			// TODO(guggero): Also abandon any channels that might
+			// still be pending from a previous round of the same
+			// batch or a previous batch that we didn't make it into
+			// the final round.
+		}
+
 		// Do an in-depth verification of the batch.
 		err = s.orderManager.OrderMatchValidate(batch)
 		if err != nil {