funding: add NotifyShimCreated callback

We'll add a channel acceptor in the next commit that verifies self chan
amounts for incoming channels. We need to notify that acceptor about new
funding shims that we register when receiving new order matches.
Otherwise the acceptor won't be aware of the bids and their current
pending channel ID.

funding/manager.go

@@ -105,6 +105,11 @@ type Manager struct {
 	// BatchStepTimeout is the timeout the manager uses when executing a
 	// single batch step.
 	BatchStepTimeout time.Duration
+
+	// NotifyShimCreated is a function that should be called whenever a
+	// funding shim is created for a bid order where we expect an incoming
+	// channel at any moment.
+	NotifyShimCreated func(ourBid *order.Bid, pendingChanID [32]byte)
 }
 
 // deriveFundingShim generates the proper funding shim that should be used by
@@ -112,7 +117,7 @@ type Manager struct {
 // funding transaction.
 func (m *Manager) deriveFundingShim(ourOrder order.Order,
 	matchedOrder *order.MatchedOrder,
-	batchTx *wire.MsgTx) (*lnrpc.FundingShim, error) {
+	batchTx *wire.MsgTx) (*lnrpc.FundingShim, [32]byte, error) {
 
 	log.Infof("Registering funding shim for Order(type=%v, amt=%v, "+
 		"nonce=%v", ourOrder.Type(),
@@ -154,14 +159,14 @@ func (m *Manager) deriveFundingShim(ourOrder order.Order,
 		ctxb, &ourKeyLocator,
 	)
 	if err != nil {
-		return nil, err
+		return nil, [32]byte{}, err
 	}
 	_, fundingOutput, err := input.GenFundingPkScript(
 		ourMultiSigKey.PubKey.SerializeCompressed(),
 		matchedOrder.MultiSigKey[:], int64(chanSize),
 	)
 	if err != nil {
-		return nil, err
+		return nil, [32]byte{}, err
 	}
 
 	// Now that we have the funding script, we'll find the output index
@@ -201,18 +206,20 @@ func (m *Manager) deriveFundingShim(ourOrder order.Order,
 		Shim: &lnrpc.FundingShim_ChanPointShim{
 			ChanPointShim: chanPointShim,
 		},
-	}, nil
+	}, pendingChanID, nil
 }
 
 // registerFundingShim is used when we're on the taker (our bid was executed)
 // side of a new matched order. To prepare ourselves for their incoming funding
 // request, we'll register a shim with all the expected parameters.
-func (m *Manager) registerFundingShim(ourOrder order.Order,
+func (m *Manager) registerFundingShim(ourBid *order.Bid,
 	matchedOrder *order.MatchedOrder, batchTx *wire.MsgTx) error {
 
 	ctxb := context.Background()
 
-	fundingShim, err := m.deriveFundingShim(ourOrder, matchedOrder, batchTx)
+	fundingShim, pendingChanID, err := m.deriveFundingShim(
+		ourBid, matchedOrder, batchTx,
+	)
 	if err != nil {
 		return err
 	}
@@ -227,6 +234,13 @@ func (m *Manager) registerFundingShim(ourOrder order.Order,
 		return fmt.Errorf("unable to register funding shim: %v", err)
 	}
 
+	// In case there is a self chan balance involved, we need our channel
+	// acceptor to be aware of the incoming order so it can verify the push
+	// amount accordingly.
+	if m.NotifyShimCreated != nil {
+		m.NotifyShimCreated(ourBid, pendingChanID)
+	}
+
 	return nil
 }
 
@@ -344,7 +358,8 @@ func (m *Manager) PrepChannelFunding(batch *order.Batch,
 			// phase w/o any issues and accept the incoming channel
 			// from the asker.
 			err := m.registerFundingShim(
-				ourOrder, matchedOrder, batch.BatchTX,
+				ourOrder.(*order.Bid), matchedOrder,
+				batch.BatchTX,
 			)
 			if err != nil {
 				return fmt.Errorf("unable to register funding "+
@@ -415,7 +430,7 @@ func (m *Manager) BatchChannelSetup(batch *order.Batch,
 		// order, and complete the funding flow for each one in which
 		// our order was the ask.
 		for _, matchedOrder := range matchedOrders {
-			fundingShim, err := m.deriveFundingShim(
+			fundingShim, _, err := m.deriveFundingShim(
 				ourOrder, matchedOrder, batch.BatchTX,
 			)
 			if err != nil {