This week’s newsletter announces a new testing tool for Bitcoin Core and briefly describes a DLC-based loan contract. Also included are our regular sections summarizing a Bitcoin Core PR Review Club, announcing new releases and release candidates, and describing notable changes to popular Bitcoin infrastructure software.

News

  • ● Mutation testing for Bitcoin Core: Bruno Garcia posted to Delving Bitcoin to announce a tool that would automatically modify (mutate) code changed in a PR or commit to determine whether the mutations cause existing tests to fail. Anytime random changes to code don’t produce a failure, it indicates that test coverage may be incomplete. Garcia’s automatic mutation tool ignores code comments and other lines of code that wouldn’t be expected to produce changes.

  • ● DLC-based loan contract execution: Shehzan Maredia posted to Delving Bitcoin to announce Lava Loans, a loan contract that uses DLC oracles for price discovery of bitcoin-collateralized loans. For example, Alice offers Bob $100,000 USD if Bob keeps at least 2x $100,000 in BTC in a deposit address. Oracles trusted by both Alice and Bob periodically publish signatures committing to the current BTC/USD price. If Bob’s BTC collateral drops below the agreed-upon amount, Alice can seize $100,000 USD worth of his BTC at the highest oracle-signed amount. Alternatively, Bob can provide proof onchain that he repaid the loan (in the form of a hash preimage revealed by Alice) to receive back his collateral. Other resolutions of the contract are available if the parties fail to cooperate or one party becomes unresponsive. As with any DLC, the price oracles are prevented from learning the contract details or even that their price information is being used in a contract.

Bitcoin Core PR Review Club

In this monthly section, we summarize a recent Bitcoin Core PR Review Club meeting.

Testing Bitcoin Core 28.0 Release Candidates was a review club meeting that did not review a particular PR, but rather was a group testing effort.

Before each major Bitcoin Core release, extensive testing by the community is considered essential. For this reason, a volunteer writes a testing guide for a release candidate so that as many people as possible can productively test without having to independently ascertain what’s new or changed in the release, and reinvent the various setup steps to test these features or changes.

Testing can be difficult because when one encounters unexpected behavior, it’s often unclear if it’s due to an actual bug or if the tester is making a mistake. It wastes developers’ time to report bugs to them that aren’t real bugs. To mitigate these problems and promote testing efforts, a Review Club meeting is held for a particular release candidate, in this instance, 28.0rc1.

The 28.0 release candidate testing guide was written by rkrux, who also hosted the review club meeting.

Attendees were also encouraged to get testing ideas by reading the 28.0 release notes.

This review club covered the introduction of testnet4 (Bitcoin Core #29775), TRUC (v3) transactions (Bitcoin Core #28948), package RBF (Bitcoin Core #28984) and conflicting mempool transactions (Bitcoin Core #27307). Other topics in the guide, but not covered in the meeting include mempoolfullrbf by default (Bitcoin Core #30493), PayToAnchor spending (Bitcoin Core #30352), and a new dumptxoutset format (Bitcoin Core #29612).

Releases and release candidates

New releases and release candidates for popular Bitcoin infrastructure projects. Please consider upgrading to new releases or helping to test release candidates.

  • ● LND v0.18.3-beta is a minor bug fix release of this popular LN node implementation.

  • ● BDK 1.0.0-beta.2 is a release candidate for this library for building wallets and other Bitcoin-enabled applications. The original bdk Rust crate has been renamed to bdk_wallet and lower layer modules have been extracted into their own crates, including bdk_chain, bdk_electrum, bdk_esplora, and bdk_bitcoind_rpc. The bdk_wallet crate “is the first version to offer a stable 1.0.0 API.”

  • ● Bitcoin Core 28.0rc1 is a release candidate for the next major version of the predominant full node implementation. A testing guide is available.

Notable code and documentation changes

Notable recent changes in Bitcoin Core, Core Lightning, Eclair, LDK, LND, libsecp256k1, Hardware Wallet Interface (HWI), Rust Bitcoin, BTCPay Server, BDK, Bitcoin Improvement Proposals (BIPs), Lightning BOLTs, Lightning BLIPs, Bitcoin Inquisition, and BINANAs.

Note: the commits to Bitcoin Core mentioned below apply to its master development branch, so those changes will likely not be released until about six months after the release of the upcoming version 28.

  • ● Bitcoin Core #30509 adds an -ipcbind option to bitcoin-node to allow other processes to connect to and control the node via a unix socket. In combination with the upcoming PR Bitcoin Core #30510, this will allow an external Stratum v2 mining service to create, manage, and submit block templates. This is part of the Bitcoin Core multiprocess project. See Newsletters #99 and #147.

  • ● Bitcoin Core #29605 changes peer discovery to prioritize peers from the local address manager over fetching from seed nodes, to reduce the influence of the latter on peer selection and reduce unnecessary information sharing. By default, seed nodes are a backup in case all DNS seeds are unreachable (which is very uncommon on mainnet); however users of test networks or customized nodes may manually add seed nodes to find similarly configured nodes. Before this PR, adding a seed node would result in it being queried for new addresses almost every time the node was started, potentially allowing it to influence peer selection and to only recommend peers that shared data with it. With this PR, only when the address manager is empty, or after a period of unsuccessful address attempts, will seed nodes be added to the address fetch queue in random order. See Newsletter #301 for more on seed nodes.