htlcswitch: remove aux bandwidth check from canSendHtlc

We remove the aux bandwidth check from the helper canSendHtlc, which was called from CheckHTLCTransit and CheckHTLCForward (both are methods of the htlcswitch). For forwards we now fail at the link level, following the introduction of the AuxHtlcValidator. For payments, we now may fail either at the pathfinding level, or at the link level. The htlcswitch may no longer fail for aux bandwidth checks.

Author: GeorgeTsagk

htlcswitch/link.go

@@ -2605,40 +2605,6 @@ func (l *channelLink) canSendHtlc(policy models.ForwardingPolicy,
 // forwarded.
 availableBandwidth := l.Bandwidth()
 
-auxBandwidth, externalErr := fn.MapOptionZ(
-l.cfg.AuxTrafficShaper,
-func(ts AuxTrafficShaper) fn.Result[OptionalBandwidth] {
-var htlcBlob fn.Option[tlv.Blob]
-blob, err := customRecords.Serialize()
-if err != nil {
-return fn.Err[OptionalBandwidth](
-fmt.Errorf("unable to serialize "+
-"custom records: %w", err))
-}
-
-if len(blob) > 0 {
-htlcBlob = fn.Some(blob)
-}
-
-return l.AuxBandwidth(amt, originalScid, htlcBlob, ts)
-},
-).Unpack()
-if externalErr != nil {
-l.log.Errorf("Unable to determine aux bandwidth: %v",
-externalErr)
-
-return NewLinkError(&lnwire.FailTemporaryNodeFailure{})
-}
-
-if auxBandwidth.IsHandled && auxBandwidth.Bandwidth.IsSome() {
-auxBandwidth.Bandwidth.WhenSome(
-func(bandwidth lnwire.MilliSatoshi) {
-availableBandwidth = bandwidth
-},
-)
-}
-
-// Check to see if there is enough balance in this channel.
 if amt > availableBandwidth {
 l.log.Warnf("insufficient bandwidth to route htlc: %v is "+
 "larger than %v", amt, availableBandwidth)