<p>You cannot dissociate probing from a legitimate failed payment attempt. If you could, then you could just prevent it in the first place.</p>
<p>To expand a bit more:</p>
<blockquote>
<p>the node for which you don't have the secret key (obviously)?</p>
</blockquote>
<p>There is no secret key. There is a payment preimage, the preimage to the hash used in the forwarded HTLC.</p>
<blockquote>
<p>Is it possible that some of the local fails are probing payments addressed to the node [...]?</p>
</blockquote>
<p>If by &quot;the node&quot; you are referring to your node, no. It would be <code>WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS</code>.</p>
<p>If you are referring to the next node, it might. According to the protocol it must send an <code>incorrect_or_unknown_payment_details</code> error. But you wouldn't be able to tell them if they didn't respect the protocol, and instead sent a <code>temporary_channel_failure</code>.</p>

CC BY-SA 4.0
2022-04-01T12:09:45.443Z
2022-04-01T13:03:42.840Z
2022-04-01T13:03:42.840Z
Antoine Poinsot
<p>I'm currently looking at output from the c-lightning -listforwards command.</p>
<p>A large portion of the payments are classified as local_failed with the failcode &quot;4103 WIRE_TEMPORARY_CHANNEL_FAILURE&quot;.</p>
<p>Is it possible that some of the local fails are probing payments addressed to the node for which you don't have the secret key (obviously)? Or would a &quot;payment&quot; like that not show up in the -listforwards output?</p>

<lightning-network><core-lightning><lightning-routing>
How to identify probing in the c-lightning implementation of the Lightning Network?
Anders Helseth
# How to identify probing in the c-lightning implementation of the Lightning Network?

(Asked by: username_0 on 2022-04-01)

I'm currently looking at output from the c-lightning -listforwards command.

A large portion of the payments are classified as local\_failed with the failcode "4103 WIRE\_TEMPORARY\_CHANNEL\_FAILURE".

Is it possible that some of the local fails are probing payments addressed to the node for which you don't have the secret key (obviously)? Or would a "payment" like that not show up in the -listforwards output?

**Tags:** lightning-network, core-lightning, lightning-routing


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## 1 answers

### Answer by username_1 on 2022-04-01. Score: 3

You cannot dissociate probing from a legitimate failed payment attempt. If you could, then you could just prevent it in the first place.

To expand a bit more:

> the node for which you don't have the secret key (obviously)?

There is no secret key. There is a payment preimage, the preimage to the hash used in the forwarded HTLC.

> Is it possible that some of the local fails are probing payments addressed to the node [...]?

If by "the node" you are referring to your node, no. It would be `WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS`.

If you are referring to the next node, it might. According to the protocol it must send an `incorrect_or_unknown_payment_details` error. But you wouldn't be able to tell them if they didn't respect the protocol, and instead sent a `temporary_channel_failure`.


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