Sending arbitrary amount to invoice with lncli

[slack-coder]

How should an invoice be paid by lncli with an arbitrary amount?

The invoice below has the amount set to '0', as it should for invoices which accept arbitrary amounts.

lncli   sendpayment --force --pay_req=[PAYMENT_REQUEST] --amt=1000
+------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| HTLC_STATE                                     | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
+------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS @ 1st hop |        0.014 |        6.152 | 1000         | 0   |   811264 | [...] |       |
+------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
Amount + fee:   0 + 0 sat
Payment hash:   [..]
Payment status: FAILED, reason: FAILURE_REASON_INCORRECT_PAYMENT_DETAILS

Alternatively, I tried setting the parameters using values from the decoded invoice, as suggested by sendpayment's '--help', but it returns 'FAILURE_REASON_NO_ROUTE'. Payments work to invoices with the payment amount set.

The LND version is 'v0.17.0-beta'

[bitromortac]

Have you tried setting --pay_addr which you get from the lncli decodeinvoice payment_addr field? Is this a direct payment?

[slack-coder]

Hi @bitromortac, thanks for the response.

Here is a detailed output of the steps I took. The last payment is to a payment request (invoice) with the amount set. What do you mean by 'direct'? There is a single channel between both points, if this is what you meant.

lncli \
  decodepayreq \
  $PAYMENT_REQUEST
# {
#     "destination": "$DESTINATION",
#     "payment_hash": "$PAYMENT_HASH",
#     "num_satoshis": "0",
#     "timestamp": "1696860087",
#     "expiry": "86400",
#     "description": "",
#     "description_hash": "",
#     "fallback_addr": "",
#     "cltv_expiry": "147",
#     "route_hints": [
#         {
#             "hop_hints": [
#                 {
#                     "node_id": "$NODE_ID",
#                     "chan_id": "$CHAN_ID",
#                     "fee_base_msat": 1000,
#                     "fee_proportional_millionths": 1,
#                     "cltv_expiry_delta": 80
#                 }
#             ]
#         }
#     ],
#     "payment_addr": "$PAYMENT_ADDR",
#     "num_msat": "0",
#     "features": {
#         "9": {
#             "name": "tlv-onion",
#             "is_required": false,
#             "is_known": true
#         },
#         "15": {
#             "name": "payment-addr",
#             "is_required": false,
#             "is_known": true
#         },
#         "17": {
#             "name": "multi-path-payments",
#             "is_required": false,
#             "is_known": true
#         },
#         "151": {
#             "name": "unknown",
#             "is_required": false,
#             "is_known": false
#         }
#     }
# }

lncli \
  sendpayment \
      --force \
      --amt=10000 \
      --pay_req=$PAYMENT_REQUEST 
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | IN_FLIGHT  |        0.014 |            - | 10000        | 0   |   811522 | $CHAN_ID |       |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | HTLC_STATE                                     | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
# +------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS @ 1st hop |        0.014 |        6.906 | 10000        | 0   |   811522 | $CHAN_ID |       |
# +------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | HTLC_STATE                                     | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
# +------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS @ 1st hop |        0.014 |        6.906 | 10000        | 0   |   811522 | $CHAN_ID |       |
# +------------------------------------------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: FAILED, reason: FAILURE_REASON_INCORRECT_PAYMENT_DETAILS
# [lncli] FAILED

lncli \
  sendpayment \
      --force \
      --dest=$DESTINATION \
      --amt=10000 \
      --payment_hash=$PAYMENT_HASH \
      --final_cltv_delta=200 \
      --pay_addr=$PAYMENT_ADDR
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+----------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   $PAYMENT_HASH
# Payment status: FAILED, reason: FAILURE_REASON_NO_ROUTE
# [lncli] FAILED

lncli \
  sendpayment \
      --force \
      --pay_req=$PAYMET_REQUEST_WITH_AMOUNT
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# +------------+--------------+--------------+--------------+-----+----------+----------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   [..]
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | IN_FLIGHT  |        0.014 |            - | 10000        | 0   |   811522 | $CHAN_ID |       |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# Amount + fee:   0 + 0 sat
# Payment hash:   [..]
# Payment status: IN_FLIGHT
# �[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# | SUCCEEDED  |        0.014 |        4.150 | 10000        | 0   |   811522 | $CHAN_ID |       |
# +------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
# Amount + fee:   10000 + 0 sat
# Payment hash:   [..]
# Payment status: SUCCEEDED, preimage: [..]

[slack-coder]

Sure, to be clear this is a new payment with the amount set.

I have control over the LND node. The channel is directly between it and an electrum bitcoin client.

• lnd version v0.17.0 built using `go install ./cmd/...'
• electrum version 4.4.6

{
    "destination": "$DESTINATION",
    "payment_hash": "$PAYMENT_HASH",
    "num_satoshis": "10000",
    "timestamp": "1696962075",
    "expiry": "86400",
    "description": "",
    "description_hash": "",
    "fallback_addr": "",
    "cltv_expiry": "147",
    "route_hints": [
        {
            "hop_hints": [
                {
                    "node_id": "$NODE_ID",
                    "chan_id": "$CHAN_ID",
                    "fee_base_msat": 1000,
                    "fee_proportional_millionths": 1,
                    "cltv_expiry_delta": 80
                }
            ]
        }
    ],
    "payment_addr": "$PAYMENT_ADDR",
    "num_msat": "10000000",
    "features": {
        "9": {
            "name": "tlv-onion",
            "is_required": false,
            "is_known": true
        },
        "15": {
            "name": "payment-addr",
            "is_required": false,
            "is_known": true
        },
        "17": {
            "name": "multi-path-payments",
            "is_required": false,
            "is_known": true
        },
        "151": {
            "name": "unknown",
            "is_required": false,
            "is_known": false
        }
    }
}

+------------+--------------+--------------+--------------+-----+----------+----------+-------+
| HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
+------------+--------------+--------------+--------------+-----+----------+----------+-------+
+------------+--------------+--------------+--------------+-----+----------+----------+-------+
Amount + fee:   0 + 0 sat
Payment hash:   $PAYMENT_HASH
Payment status: IN_FLIGHT
�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| IN_FLIGHT  |        0.014 |            - | 10000        | 0   |   811722 | $CHAN_ID |       |
+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
Amount + fee:   0 + 0 sat
Payment hash:   $PAYMENT_HASH
Payment status: IN_FLIGHT
�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K�[1A�[2K+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT           | ROUTE |
+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
| SUCCEEDED  |        0.014 |        2.502 | 10000        | 0   |   811722 | $CHAN_ID |       |
+------------+--------------+--------------+--------------+-----+----------+--------------------+-------+
Amount + fee:   10000 + 0 sat
Payment hash:   $PAYMENT_HASH
Payment status: SUCCEEDED, preimage: [..]

[slack-coder]

Hi @bitromortac, is there any more information which would help? This should theoretically work right?

[bitromortac]

It may be an interoperability issue, I will try to reproduce this.

[bitromortac]

I could reproduce your case, the issue is that electrum refuses to accept payments to invoices with zero amounts, I think. It sends back FAILURE_REASON_INCORRECT_PAYMENT_DETAILS with the following electrum log lines:

3773.04 | I | P/lnpeer.Peer.[LNWallet, 02a5a03c88-01b209dd] | maybe_fulfill_htlc. will FAIL HTLC: chan 150x1x1. total_msat=100000 too different from invoice_msat=0. htlc=UpdateAddHtlc(amount_msat=100000, payment_hash=ca2257e09340560844d26772724ecdc612559fd24182426bc0f0dd1493745fd6, cltv_expiry=302, timestamp=1698071485, htlc_id=3). onion_payload={'amt_to_forward': {'amt_to_forward': 100000}, 'outgoing_cltv_value': {'outgoing_cltv_value': 302}, 'payment_data': {'payment_secret': b"\xc6\xf3\x93\x84f\x8c'J\xa1\x12\x94\x18\x84\x02y\xdeW\x7f\x93:- \x96\x88\x11\xf4{\xd8\x8d\t;\xa9", 'total_msat': 100000}}

The relevant part is total_msat=100000 too different from invoice_msat=0, which comes from here: https://github.com/spesmilo/electrum/blob/eb676b3dc1fe6f14cdd845c16ef1bf8fa2d1d725/electrum/lnpeer.py#L1985. The problem here is that in the invoice object the amount is not None but zero, which then triggers that line. On the other hand I could pay from lnd to lnd with a zero-amount invoice.

Edit: opened an issue on the electrum repo: spesmilo/electrum#8658

[slack-coder]

Much appreciated @bitromortac, thanks for the help.