tapchannel: utilize new outpointToTxIndex map in NotifyBroadcast

In this commit, we update the logic of `notifyBroadcast` to use the new
`outpointToTxIndex` map. We'll use this to make sure that the vOut has
the correct anchor output index, as the sweeper applies a sorting
routine before broadcast.

Otherwise, we'll have invalid inclusion proofs.

Author: Roasbeef

server.go

@@ -1170,5 +1170,5 @@ func (s *Server) NotifyBroadcast(req *sweep.BumpRequest,
 		return err
 	}
 
-	return s.cfg.AuxSweeper.NotifyBroadcast(req, tx, fee)
+	return s.cfg.AuxSweeper.NotifyBroadcast(req, tx, fee, outpointToTxIndex)
 }

tapchannel/aux_sweeper.go

@@ -76,6 +76,11 @@ type broadcastReq struct {
 	// fee is the fee that was used for the transaction.
 	fee btcutil.Amount
 
+	// outpointToTxIndex maps a spent outpoint to the tx index on the sweep
+	// transaction of the corresponding output. This is only needed to make
+	// sure we make proofs properly for the pre-signed HTLC transactions.
+	outpointToTxIndex map[wire.OutPoint]int
+
 	// resp is the error result of the broadcast.
 	resp chan error
 }
@@ -2226,7 +2231,8 @@ func sweepExclusionProofGen(sweepInternalKey keychain.KeyDescriptor,
 // registerAndBroadcastSweep finalizes a sweep attempt by generating a
 // transition proof for it, then registering the sweep with the porter.
 func (a *AuxSweeper) registerAndBroadcastSweep(req *sweep.BumpRequest,
-	sweepTx *wire.MsgTx, fee btcutil.Amount) error {
+	sweepTx *wire.MsgTx, fee btcutil.Amount,
+	outpointToTxIndex map[wire.OutPoint]int) error {
 
 	// TODO(roasbeef): need to handle replacement -- will porter just
 	// upsert in place?
@@ -2302,6 +2308,27 @@ func (a *AuxSweeper) registerAndBroadcastSweep(req *sweep.BumpRequest,
 		}
 	}
 
+	// For pre-signed HTLC txns we'll need to make sure we update the output
+	// index in the vPkt. As the ordering is only determined at broadcast
+	// time.
+	if outpointToTxIndex != nil {
+		for _, sweepPkt := range vPkts.allVpktsWithInput() {
+			op := sweepPkt.btcInput.OutPoint()
+			finalOutputIndex, ok := outpointToTxIndex[op]
+			if !ok {
+				continue
+			}
+
+			for _, vPkt := range sweepPkt.vPkts {
+				for _, vOut := range vPkt.Outputs {
+					vOut.AnchorOutputIndex = uint32(
+						finalOutputIndex,
+					)
+				}
+			}
+		}
+	}
+
 	// If we have second level vPkts, then we'll need to sign them here, as
 	// now we know the input we're spending which was set above.
 	for _, sweepSet := range vPkts.secondLevel {
@@ -2400,6 +2427,7 @@ func (a *AuxSweeper) contractResolver() {
 		case req := <-a.broadcastReqs:
 			req.resp <- a.registerAndBroadcastSweep(
 				req.req, req.tx, req.fee,
+				req.outpointToTxIndex,
 			)
 
 		case <-a.quit:
@@ -2487,13 +2515,15 @@ func (a *AuxSweeper) ExtraBudgetForInputs(
 // NotifyBroadcast is used to notify external callers of the broadcast of a
 // sweep transaction, generated by the passed BumpRequest.
 func (a *AuxSweeper) NotifyBroadcast(req *sweep.BumpRequest,
-	tx *wire.MsgTx, fee btcutil.Amount) error {
+	tx *wire.MsgTx, fee btcutil.Amount,
+	outpointToTxIndex map[wire.OutPoint]int) error {
 
 	auxReq := &broadcastReq{
-		req:  req,
-		tx:   tx,
-		fee:  fee,
-		resp: make(chan error, 1),
+		req:               req,
+		tx:                tx,
+		fee:               fee,
+		outpointToTxIndex: outpointToTxIndex,
+		resp:              make(chan error, 1),
 	}
 
 	if !fn.SendOrQuit(a.broadcastReqs, auxReq, a.quit) {