Invoice transaction expiration time does not take effect

[yanwankun]

I found a problem here. We were paying an invoice generated by someone else. After the invoice expired without success, we thought the payment would not be successful, but the transaction was successful in the end. Does anyone know why this is?

invoice info

{
  "destination": "026165850492521f4ac8abd9bd8088123446d126f648ca35e60f88177dc149ceb2",
  "payment_hash": "09f45f34e4692100c38bc00184da8f448e35fe8f88a168a54a27fb3dc4bd664b",
  "num_satoshis": "2000000",
  "timestamp": "1696654904",
  "expiry": "3600",
  "description": "Send to L-BTC address",
  "description_hash": "",
  "fallback_addr": "",
  "cltv_expiry": "180",
  "route_hints": [
    
  ],
  "payment_addr": "CfVrqc8lIa9buQSwowwZLWH3Y6k8NwLoXJBvwHQUuY8=",
  "num_msat": "2000000000",
  "features": {
    "9": {
      "name": "tlv-onion",
      "is_required": false,
      "is_known": true
    },
    "14": {
      "name": "payment-addr",
      "is_required": true,
      "is_known": true
    },
    "17": {
      "name": "multi-path-payments",
      "is_required": false,
      "is_known": true
    }
  }
}

Transaction success information is as follows

{
  "payment_hash": "09f45f34e4692100c38bc00184da8f448e35fe8f88a168a54a27fb3dc4bd664b",
  "value": "2000000",
  "creation_date": "1696655051",
  "fee": "1000",
  "payment_preimage": "1d44c8edbd00aedb779dd2c9caa3bfd77094b918e0306224d19c5b8b19724832",
  "value_sat": "2000000",
  "value_msat": "2000000000",
  "payment_request": "lnbc20m1pjjpe3cpp5p8697d8ydysspsutcqqcfk50gj8rtl503zsk3f22ylanm39ave9sdpz2djkuepqw3hjqnpdgf2yxgrpv3j8yetnwvcqz95xqrrsssp5p86kh2w0y5s67kaeqjc2xrqe94slwcaf8sms96zujphuqaq5hx8s9qyyssqevv0j7k5s72xfk9yjwuw6l896hqf75jf9ln203wchz86408f2qt32neh6waet2fmdp5nlj28h6mmwakn66ueznc767uk730wdqht8dcpda7t8z",
  "status": "SUCCEEDED",
  "fee_sat": "1000",
  "fee_msat": "1000000",
  "creation_time_ns": "1696655051898952423",
  "htlcs": [
    {
      "attempt_id": "12175",
      "status": "SUCCEEDED",
      "route": {
        "total_time_lock": 811222,
        "total_fees": "1000",
        "total_amt": "2001000",
        "hops": [
          {
            "chan_id": "880249217993867265",
            "chan_capacity": "50000000",
            "amt_to_forward": "2000000",
            "fee": "1000",
            "expiry": 811182,
            "amt_to_forward_msat": "2000000000",
            "fee_msat": "1000000",
            "pub_key": "0294ac3e099def03c12a37e30fe5364b1223fd60069869142ef96580c8439c2e0a",
            "tlv_payload": true,
            "mpp_record": null,
            "amp_record": null,
            "custom_records": {
              
            },
            "metadata": ""
          },
          {
            "chan_id": "814320301900496896",
            "chan_capacity": "100000000",
            "amt_to_forward": "2000000",
            "fee": "0",
            "expiry": 811182,
            "amt_to_forward_msat": "2000000000",
            "fee_msat": "0",
            "pub_key": "026165850492521f4ac8abd9bd8088123446d126f648ca35e60f88177dc149ceb2",
            "tlv_payload": true,
            "mpp_record": {
              "payment_addr": "CfVrqc8lIa9buQSwowwZLWH3Y6k8NwLoXJBvwHQUuY8=",
              "total_amt_msat": "2000000000"
            },
            "amp_record": null,
            "custom_records": {
              
            },
            "metadata": ""
          }
        ],
        "total_fees_msat": "1000000",
        "total_amt_msat": "2001000000"
      },
      "attempt_time_ns": "1696655052108802132",
      "resolve_time_ns": "1696661193610594176",
      "failure": null,
      "preimage": "HUTI7b0Artt3ndLJyqO/13CUuRjgMGIk0ZxbixlySDI="
    }
  ],
  "payment_index": "3078",
  "failure_reason": "FAILURE_REASON_NONE"
}

attemp time 1696655052 2023-10-07 05:04:12
resolve time 1696661193 2023-10-07 06:46:33

This time must be 3600 seconds too long, but it still worked.

[hieblmi]

As I read the BOLT 11 spec it is compliant if the expiry is ignored by the payee: https://github.com/lightning/bolts/blob/master/11-payment-encoding.md#payer--payee-requirements

[yanwankun]

After receiving the ticket, we only made one payment request through /v2/router/send. We thought that without subsequent processing, it would not be successful after the expiration time, but after the expiration time, it was still successful. , and it took so long, it was already more than an hour, almost two hours, and another one was close to 10 hours. I don’t know why this happened. And I don’t know when we will know that this payment request will definitely not be successful.

[hieblmi]

It could be that the payment was accepted within the expiry period on the invoice, but then the payment settlement was delayed because the HTLC was "stuck". In this scenario you either have to wait till the payment is settled/cancelled or until the HTLC times out(worst-case).

[yanwankun]

When you talk about the HTLC expiration time, do you mean the expiration time here? But because the transaction has not been confirmed, I don’t know which channel this transaction will use. In fact, the expiration time of all channels is the same, right?