Testing LNDK: Onion Messages (with LDK-Sample) 🧅

[carlaKC]

Testing LNDK locally for development requires a fair amount of setup. This discussion outlines possilbe ways of testing new features locally, with a specific focus on onion messaging related features. Ths guide assumes that you have bitcoind running in regtest mode and have setup LND and LND as described in README.

1. Setup LDK Nodes

Setup two LDK sample nodes, per the installation guide provided.

// Directory and port *MUST* be unique for each node!
cargo run {bitcoin_user}:{bitcoin_password}@{bitcoin_host:port} ~/.ldk 19777 regtest
cargo run {bitcoin_user}:{bitcoin_password}@{bitcoin_host:port} ~/.ldk1 19778 regtest

Each node will startup and log their node id: Local Node ID is {pubkey}.

2. Connect LND to LDK

Connect: LDK -- LND -- LDK1:
lncli connect {node_id_1}@localhost:19777
lncli connect {node_id_2}@localhost:19778

Do not connect the LDK nodes, as they may not choose to forward onion messages through LND if they are directly connected.

3. Send an Onion Message

In the command prompt for LDK, send an onion message with the following command:
sendonionmessage {lnd_pubkey},{ldk_1_pubkey} 513 74657374

Note that the node pubkeys must be comma seprated (with no spaces) and the final value is just a junk hex payload.

You should be able to see logs in LDK's logs (~/.ldk/.ldk/logs/logs.txt) indicating that a message has been received (though it will error, because the payload is junk), and LND will log Custom message received peer={peer} type=513 and Sending <unknown>(type=513) to {peer}.