Testing LNDK: Onion Messages (with CLN) 🧅

[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 CLN Nodes

Run two CLN nodes (see Getting Started guide) in developer mode (./configure --enable-developer). The bare minimum command set you can work with is:

./lightningd/lightningd --network=regtest --bitcoin-rpcuser={user} --bitcoin-rpcpassword=lightning --bitcoin-rpcconnect=localhost --bitcoin-rpcport={bitcoin_port} --log-level=debug --experimental-offers --dev-fast-gossip
// The following *MUST* be unique for each node
  --lightning-dir=~/.lightning
  --addr=localhost:19976
  --grpc-port=19971

Note: --dev-fast-gossip and --experimental-offers are important.

You can create the following aliases for convenience:
alias cl="./cli/lightning-cli --network=regtest --lightning-dir=~/.lightning"
alias cl1="./cli/lightning-cli --network=regtest --lightning-dir=~/.lightning1"

2. Open public channels between CL -- LND and CL1 -- LND, for each CL node:

cl getinfo -> provides pubkey in id and host/port in address
lncli openchannel --node_key={id} --connect=locahost:{port} --local_amt=20000

Remember to mine 6 blocks to confirm channel!

To verify that the channels are open:

• CLN: cl listincoming
• LND: lncli listchannels

3. Fetch an offer invoice to test Onion Messaging

• Create offer: cl offer 100 test -> bolt12: lno...
• Fetch invoice: cl1 fetchinvoice lno....

This should send an onion message from CL1 --> LND --> CL to fetch the invoice, then a return onion message from CL --> LND --> CL1 to return it.

You should be able to see logs in LNDK indicating that a message has been forwarded, and LND will log Custom message received peer={peer} type=513 and Sending <unknown>(type=513) to {peer}.

[orbitalturtle]

Super helpful guide. I've been exploring a bit how to get the first chunk of the directions up and running in Polar (https://lightningpolar.com/), to make it a bit easier to set up a testing environment. If anyone finds this useful... Feel free to use the following zip in Polar to auto-set up a bitcoind backend with some blocks mined and two CLN nodes:

onion-message-testing.polar.zip

In Polar just click "import network" and drag the above zip file inside, and start the network. (This feature is like my favorite thing ever as of... today)

Couldn't get the custom version of lnd node that we need for this project running in Polar for some reason, but maybe I'll do some debugging and add that in later. For now for the lnd node -- hook up the lnd node you run above to the bitcoind

[carlaKC]

In Polar just click "import network" and drag the above zip file inside, and start the network. (This feature is like my favorite thing ever as of... today)

🔥 very cool!

Couldn't get the custom version of lnd node that we need for this project running in Polar for some reason

iirc, polar needs some customization for the docker file for each LN node, so maybe that's the issue?

[orbitalturtle]

iirc, polar needs some customization for the docker file for each LN node, so maybe that's the issue?

Oh cool thanks! Didn't see that, that definitely might be the problem