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multi: Fix final hop payload size for blinded rt.

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The final hop size is calculated differently therefore we extract
the logic in its own function and also account for the case where
the final hop might be a blinded hop.
This commit is contained in:
ziggie
2024-02-03 11:59:29 +00:00
parent c1b91fff14
commit ff30ff40bf
3 changed files with 211 additions and 22 deletions
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70
routing/pathfind.go
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@@ -411,6 +411,10 @@ type RestrictParams struct {
// Metadata is additional data that is sent along with the payment to
// the payee.
Metadata []byte
// BlindedPayment is necessary to determine the hop size of the
// last/exit hop.
BlindedPayment *BlindedPayment
}
// PathFindingConfig defines global parameters that control the trade-off in
@@ -635,23 +639,10 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
}
}
// Build a preliminary destination hop structure to obtain the payload
// size.
var mpp *record.MPP
if r.PaymentAddr != nil {
mpp = record.NewMPP(amt, *r.PaymentAddr)
}
finalHop := route.Hop{
AmtToForward: amt,
OutgoingTimeLock: uint32(finalHtlcExpiry),
CustomRecords: r.DestCustomRecords,
LegacyPayload: !features.HasFeature(
lnwire.TLVOnionPayloadOptional,
),
MPP: mpp,
Metadata: r.Metadata,
}
// The payload size of the final hop differ from intermediate hops
// and depends on whether the destination is blinded or not.
lastHopPayloadSize := lastHopPayloadSize(r, finalHtlcExpiry, amt,
!features.HasFeature(lnwire.TLVOnionPayloadOptional))
// We can't always assume that the end destination is publicly
// advertised to the network so we'll manually include the target node.
@@ -669,7 +660,7 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
amountToReceive: amt,
incomingCltv: finalHtlcExpiry,
probability: 1,
routingInfoSize: finalHop.PayloadSize(0),
routingInfoSize: lastHopPayloadSize,
}
// Calculate the absolute cltv limit. Use uint64 to prevent an overflow
@@ -1112,3 +1103,46 @@ func getProbabilityBasedDist(weight int64, probability float64,
return int64(dist)
}
// lastHopPayloadSize calculates the payload size of the final hop in a route.
// It depends on the tlv types which are present and also whether the hop is
// part of a blinded route or not.
func lastHopPayloadSize(r *RestrictParams, finalHtlcExpiry int32,
amount lnwire.MilliSatoshi, legacy bool) uint64 {
if r.BlindedPayment != nil {
blindedPath := r.BlindedPayment.BlindedPath.BlindedHops
blindedPoint := r.BlindedPayment.BlindedPath.BlindingPoint
encryptedData := blindedPath[len(blindedPath)-1].CipherText
finalHop := route.Hop{
AmtToForward: amount,
OutgoingTimeLock: uint32(finalHtlcExpiry),
LegacyPayload: false,
EncryptedData: encryptedData,
}
if len(blindedPath) == 1 {
finalHop.BlindingPoint = blindedPoint
}
// The final hop does not have a short chanID set.
return finalHop.PayloadSize(0)
}
var mpp *record.MPP
if r.PaymentAddr != nil {
mpp = record.NewMPP(amount, *r.PaymentAddr)
}
finalHop := route.Hop{
AmtToForward: amount,
OutgoingTimeLock: uint32(finalHtlcExpiry),
CustomRecords: r.DestCustomRecords,
LegacyPayload: legacy,
MPP: mpp,
Metadata: r.Metadata,
}
// The final hop does not have a short chanID set.
return finalHop.PayloadSize(0)
}