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feat: add routing hints for private nodes in LND #1186

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feat: add routing hints for private nodes in LND #1186

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67 changes: 66 additions & 1 deletion lnclient/lnd/lnd.go
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Original file line number Diff line number Diff line change
Expand Up @@ -468,12 +468,23 @@ func (svc *LNDService) MakeInvoice(ctx context.Context, amount int64, descriptio
}
}

isPrivate := !hasPublicChannels

var hints []*lnrpc.RouteHint
if isPrivate {
hints, err = svc.getRoutingHints(ctx)
if err != nil {
return nil, err
}
}

addInvoiceRequest := &lnrpc.Invoice{
ValueMsat: amount,
Memo: description,
DescriptionHash: descriptionHashBytes,
Expiry: expiry,
Private: !hasPublicChannels, // use private channel hints in the invoice
RouteHints: hints,
Private: isPrivate, // use private channel hints in the invoice
}

resp, err := svc.client.AddInvoice(ctx, addInvoiceRequest)
Expand All @@ -492,6 +503,60 @@ func (svc *LNDService) MakeInvoice(ctx context.Context, amount int64, descriptio
return transaction, nil
}

func (svc *LNDService) getRoutingHints(ctx context.Context) (hints []*lnrpc.RouteHint, err error) {
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Did you take inspiration from anywhere for this code? I think there are quite a few issues here.

Can you please check the LND codebase and some other lightning wallets (e.g. https://github1s.com/ZeusLN/zeus/blob/HEAD/lndmobile/index.ts#L632-L633)

I think there's no limit right now, right? we need to limit it to 3 (the "best" options based on incoming liquidity and fees)

Can you also check if we have 1 peer the route hint is exactly the same as is when not using this code. We need to make very sure we don't break this code otherwise no-one with private channels will be able to receive.

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I'm not sure the above code I linked is used. I've also asked Zeus if they can give us any recommendations.

channelsRes, err := svc.client.ListChannels(ctx, &lnrpc.ListChannelsRequest{
PrivateOnly: true,
})
if err != nil {
return nil, err
}

processedPeers := make(map[string]struct{})
for _, channel := range channelsRes.Channels {
if _, ok := processedPeers[channel.RemotePubkey]; ok {
continue
}

chanInfo, err := svc.client.GetChanInfo(ctx, &lnrpc.ChanInfoRequest{
ChanId: channel.ChanId,
})
if err != nil {
logger.Logger.WithFields(logrus.Fields{
"channel_id": channel.ChanId,
}).WithError(err).Error("Unable to add routing hint")
continue
}

remotePolicy := chanInfo.Node2Policy
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Node2 is not always the counterparty is it?

if remotePolicy == nil {
continue
}

feeBaseMsat := uint32(remotePolicy.FeeBaseMsat)
proportionalFee := uint32(remotePolicy.FeeRateMilliMsat)
cltvExpiryDelta := remotePolicy.TimeLockDelta

logger.Logger.WithFields(logrus.Fields{
"remote_pubkey": channel.RemotePubkey,
}).Info("Adding routing hint")

hint := &lnrpc.RouteHint{
HopHints: []*lnrpc.HopHint{
{
NodeId: channel.RemotePubkey,
ChanId: chanInfo.ChannelId,
FeeBaseMsat: feeBaseMsat,
FeeProportionalMillionths: proportionalFee,
CltvExpiryDelta: cltvExpiryDelta,
},
},
}
hints = append(hints, hint)
processedPeers[channel.RemotePubkey] = struct{}{}
}
return hints, nil
}

func (svc *LNDService) LookupInvoice(ctx context.Context, paymentHash string) (transaction *lnclient.Transaction, err error) {
paymentHashBytes, err := hex.DecodeString(paymentHash)
if err != nil || len(paymentHashBytes) != 32 {
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