plugins/paytest

Paytest Plugin

• Protocol

A plugin to benchmark the performance of the pay plugin. It can generate mock invoices for remote nodes, and it can hold on to incoming test multi-part payments as if they were real payments.

🚧 This plugin is intended for LN developers. Use it at your own risk 👷

The plugin consists of three parts:

• testinvoice: An RPC method to generate a fake invoice which forces any payer to go through a specific node as penultimate hop in the route. That node can then decode the onion and pretend it is the real destination. The invoice is valid, however the payment_hash has no known preimage and can therefore not be settled.
• An htlc_accepted hook that intercepts any HTLC resulting from a remote testpay call, decodes the payload and pretends to be the recipient, exercising the MPP aggregation logic.
• testpay: A wrapper RPC method that takes generates a testinvoice and calls pay on it, triggering the benchmarking. Upon receiving the result it re-interprets it according to what we expect to happen

Protocol

The protocol consists of a couple of conventions in order to correctly test the pay process.

The sender always creates a test invoice, with a payment_hash that it knows has no known preimage, and destined for a non-existent node_id, but which includes a route-hint from the real destination to the fake destination. The route-hint MUST use the short channel ID 1x1x1 for the channel, as this is how the recipient identifies that this is a test-payment. In addition the other parameters in the route hint SHOULD use minimal values in order not to interfere with the testing (CLTV delta 9, base fee 1, proportional fee 1).

Since we are creating fake invoices for nodes that do not exist, and with a payment_hash that the destination cannot settle we re-interpret the following failure codes:

• 16399 / 0x400f (incorrect_or_unknown_payment_details) is considered to be a successful payment attempt, i.e., the destination understood that this is a test payment, has held onto incoming parts for up to 60 seconds, allowing them to accumulate, and ultimately all parts reached the destination.
• 23 / 0x0017 (mpp_timeout) is considered a failed payment attempt, i.e., the destination understood this is a test payment, has helpd on to incoming parts for 60 seconds, but ultimately failed to accumulate all parts of the payment.
• 16394 / 0x400a (unknown_next_peer) signifies that the destination did not understand the protocol, and the test failed. This is the default behavior that nodes implement if this plugin is not active.