From cd0e15fd73d9f6e8a4b30aa8e469c71462373758 Mon Sep 17 00:00:00 2001 From: Olaoluwa Osuntokun Date: Tue, 7 May 2024 21:31:41 -0700 Subject: [PATCH] htlcswitch: allow custom HTLCs to bypass the amt to fwrd check As this is a exit hop HTLC, we'll rely on the decision from the invoice registry to decide if we should continue or not. --- htlcswitch/link.go | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/htlcswitch/link.go b/htlcswitch/link.go index 18952b31f..0c01cd0eb 100644 --- a/htlcswitch/link.go +++ b/htlcswitch/link.go @@ -3566,13 +3566,20 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor, return nil } - // As we're the exit hop, we'll double check the hop-payload included in - // the HTLC to ensure that it was crafted correctly by the sender and - // is compatible with the HTLC we were extended. - if pd.Amount < fwdInfo.AmountToForward { + // As we're the exit hop, we'll double check the hop-payload included + // in the HTLC to ensure that it was crafted correctly by the sender + // and is compatible with the HTLC we were extended. + // + // For a special case, if the fwdInfo doesn't have any blinded path + // information, and the incoming HTLC had special extra data, then + // we'll skip this amount check. + hasBlindedPath := fwdInfo.NextBlinding.IsSome() + customHTLC := pd.CustomRecords.IsSome() && !hasBlindedPath + log.Infof("custom_htlc_bypass=%v", customHTLC) + if !customHTLC && pd.Amount < fwdInfo.AmountToForward { l.log.Errorf("onion payload of incoming htlc(%x) has "+ "incompatible value: expected <=%v, got %v", pd.RHash, - pd.Amount, fwdInfo.AmountToForward) + fwdInfo.AmountToForward, pd.Amount) failure := NewLinkError( lnwire.NewFinalIncorrectHtlcAmount(pd.Amount),