LND v0.18.0-beta Release Candidate

[saubyk]

Hey Everyone,

The first release candidate for the upcoming LND v0.18.0 has been published. This is a feature packed release which covers a lot of areas including SQL schema for Invoices, Sweeper overhaul, Route Blinding and Inbound Routing fee to name a few. We do expect a few rounds of RCs to iron out any potential issues found during testing.

The release can be found here:
https://github.com/lightningnetwork/lnd/releases/tag/v0.18.0-beta.rc1

The release notes are available at:
https://github.com/lightningnetwork/lnd/blob/master/docs/release-notes/release-notes-0.18.0.md

Below are some of the release highlights:

SQL Schema store for Invoices

• Relational DB store is now available as an option for the Invoice database
• This feature is exclusively available for users setting up new nodes and should be considered experimental
• Users can set db.use-native-sql=true under the [db] section of the config file to make use of this capability

Sweeper Overhaul

• More Detailed Transaction Information: Users will now have access to more detailed information about their sweep transactions, including the current fee rate used, the budget and the deadline
• Improved Sweeping Process: The process for sweeping transactions is now more sophisticated. Consolidates multiple small outputs leading to better management of funds and more efficient use of network resources
• Enhanced Fee Management: A new fee management system has been introduced that aims to prevent overpayment of fees and supports Replace-By-Fee (RBF) compliant transactions. This could result in cost savings for users as network conditions change
  • The users can now specify a fee budget with the parameter budget (sats) with the bumpfee rpc. This budget provides a ceiling on the amount which can spent as fee for sweeping
  • The fee rate which is specified in the param is the starting fee rate, which is gradually bumped up every block, the sweep transaction remains unconfirmed
• Deadline Awareness: LND will auto fee bump internally depending on the urgency of the HTLCs outputs which must be swept before reaching certain block height
• Immediate Sweep Option: For time-sensitive payments, users can now get their transactions swept immediately by setting an Immediate flag with the bumpfee rpc, providing more control over the timing of their transactions
• Immediate Sweep on Startup: Upon startup, lnd will now perform an immediate sweep of time-sensitive outputs. This ensures that any pending transactions are processed promptly, which can be particularly urgent after a software update or restart
• New config params introduced: Additional config params have been introduced to provide various controls on fee management for sweeping
  • sweeper.nodeadlineconftarget
  • New config group - sweeper.budget
  • Checkout the sample-lnd.conf for more details on these params
• Refer to the readme file for implementation details: https://github.com/lightningnetwork/lnd/blob/master/sweep/README.md

Route Blinding

• Payment pathfinding to blinded routes
• Updated mission control to handle pathfinding errors for blinded routes
• Forwarding of payments to blinded routes

Inbound fee

• Ability to charge a fee on the incoming channel. Currently only a negative fee is enabled which implies an overall discount on the payment. This basically means an optional discount can be applied to route through a certain channel
• Send support which results in pathfinding taking into account inbound fee/discounts of the routers in the payment path
• Users can set the values via new cli arguments inbound_base_fee_msat and inbound_fee_rate_ppm. The values should only be set as zero or -ve

Probing for fee estimation

• EstimateRouteFee rpc has been enhanced to perform payment probing
• The rpc now optionally accepts an invoice from the target node and a probe payment timeout
• Two use cases are covered with the change:
  • Probing to a public destination pubkey specified in the invoice
  • Probing a private invoice destination reachable through public hop hints in the invoice

Watchtower improvements

• Watchtower support for taproot commitments
• Performance improvements to reduce startup time of watchtower client

Other improvements and bug fixes

• Mutual close with pending HTLCs: This change fixed an issue where the channels would get force-closed if a shutdown message is received while HTLCs are in flight on the channel
• Min fee filter for optimal transaction propagation: When computing a minimum fee for transaction construction, LND now takes the bitcoin peers’ feefilter value into account. This ensures high probability of transaction propagation
• Introduction of a fee buffer to handle scenarios where fee rate changes sharply or the case where htlcs are added asynchronously resulting in stuck channels. This also makes LND compliant with BOLT02
• Payment lifecycle has been refactored to address different scenarios which could result in stuck payments. A new payment status StatusInitiated has been added and the status StatusUnknown is now deprecated. The new payment status requires the config flag routerrpc.usestatusinitiated to be set
• Transactions being published onchain will now go through a mempool acceptance check via the testmempoolaccept rpc. If the transaction fails the test broadcast won’t be attempted. This is enabled for bitcoind v22.0.0 and btcd v0.24.1 and above
• Another issue related to LND losing sync while running on a pruned bitcoin node has also been addressed
• Litecoin is no longer a supported chain on LND 🎉

There are a lot of bug fixes and minor changes which can be tracked via the release notes linked above
Reports of issues found during testing will be highly appreciated 🫂

Thanks