tapchannel: check custom records contain assets

Currently (*AuxTrafficShaper).ProduceHtlcExtraData exits early if the
htlcCustomRecords are empty. However, we need to cater for the case when
htlc custom records exist from other contexts (such as endorsement
signaling) and so we change this check to be more strict and to check
that the records dont contain any asset records.

Author: ellemouton

rfqmsg/records.go

@@ -237,6 +237,18 @@ func HasAssetHTLCCustomRecords(records lnwire.CustomRecords) bool {
 	return false
 }
 
+// HasAssetHTLCEntries returns true if the given blob contains the custom
+// records that we'd expect an asset HTLC to carry. If the blob is not a valid
+// custom records blob, this function will return false.
+func HasAssetHTLCEntries(blob tlv.Blob) bool {
+	customRecords, err := lnwire.ParseCustomRecords(blob)
+	if err != nil {
+		return false
+	}
+
+	return HasAssetHTLCCustomRecords(customRecords)
+}
+
 // AssetBalance is a record that represents the amount of an asset that is
 // being transferred or is available to be spent.
 type AssetBalance struct {

tapchannel/aux_traffic_shaper.go

@@ -82,6 +82,7 @@ func (s *AuxTrafficShaper) ShouldHandleTraffic(_ lnwire.ShortChannelID,
 	// If there is no auxiliary blob in the channel, it's not a custom
 	// channel, and we don't need to handle it.
 	if fundingBlob.IsNone() {
+		log.Tracef("No aux funding blob set, not handling traffic")
 		return false, nil
 	}
 
@@ -113,6 +114,8 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	// bandwidth from a taproot asset perspective. We return the link
 	// bandwidth as a fallback.
 	if commitmentBlob.IsNone() || htlcBlob.IsNone() {
+		log.Tracef("No commitment or HTLC blob set, returning link "+
+			"bandwidth %v", linkBandwidth)
 		return linkBandwidth, nil
 	}
 
@@ -122,6 +125,16 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	// Sometimes the blob is set but actually empty, in which case we also
 	// don't have any information about the channel.
 	if len(commitmentBytes) == 0 || len(htlcBytes) == 0 {
+		log.Tracef("Empty commitment or HTLC blob, returning link "+
+			"bandwidth %v", linkBandwidth)
+		return linkBandwidth, nil
+	}
+
+	// If there are no asset HTLC custom records, we don't need to do
+	// anything as this is a regular payment.
+	if !rfqmsg.HasAssetHTLCEntries(htlcBytes) {
+		log.Tracef("No asset HTLC custom records, returning link "+
+			"bandwidth %v", linkBandwidth)
 		return linkBandwidth, nil
 	}
 
@@ -174,6 +187,9 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 		// it goes below the reserve, we report zero bandwidth as we
 		// cannot push the HTLC amount.
 		if linkBandwidth < htlcAmt {
+			log.Tracef("Link bandwidth %v smaller than HTLC "+
+				"amount %d, returning 0 as we'd dip below "+
+				"reserver otherwise", linkBandwidth, htlcAmt)
 			return 0, nil
 		}
 
@@ -189,6 +205,8 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	// If the HTLC doesn't have an asset amount and RFQ ID, it's incomplete,
 	// and we cannot determine what channel to use.
 	if htlc.RfqID.ValOpt().IsNone() {
+		log.Tracef("No RFQ ID in HTLC, cannot determine matching " +
+			"outgoing channel")
 		return 0, nil
 	}
 
@@ -228,6 +246,9 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	// to check if the link bandwidth can afford sending a non-dust htlc to
 	// the other side.
 	if linkBandwidth < minHtlcAmt {
+		log.Tracef("Link bandwidth %v smaller than HTLC min amount "+
+			"%d, returning 0 as we'd dip below reserver otherwise",
+			linkBandwidth, minHtlcAmt)
 		return 0, nil
 	}
 
@@ -243,7 +264,9 @@ func (s *AuxTrafficShaper) ProduceHtlcExtraData(totalAmount lnwire.MilliSatoshi,
 	htlcCustomRecords lnwire.CustomRecords) (lnwire.MilliSatoshi,
 	lnwire.CustomRecords, error) {
 
-	if len(htlcCustomRecords) == 0 {
+	if !rfqmsg.HasAssetHTLCCustomRecords(htlcCustomRecords) {
+		log.Tracef("No asset HTLC custom records, not producing " +
+			"extra data")
 		return totalAmount, nil, nil
 	}
 
@@ -258,6 +281,8 @@ func (s *AuxTrafficShaper) ProduceHtlcExtraData(totalAmount lnwire.MilliSatoshi,
 	// keysend payment and don't need to do anything. We even return the
 	// original on-chain amount as we don't want to change it.
 	if htlc.Amounts.Val.Sum() > 0 {
+		log.Tracef("Already have asset amount (sum %d) in HTLC, not "+
+			"producing extra data", htlc.Amounts.Val.Sum())
 		return totalAmount, htlcCustomRecords, nil
 	}