Bitcoin Core 0.15.1 Released

Overview

• Notable changes
  • Network fork safety enhancements
  • RPC changes
  • Miner block size limiting deprecated
  • GUI settings backed up on reset
  • Duplicate wallets disallowed
  • Debug -minimumchainwork argument added
• Conclusion
• Hashes for verification

We are pleased to announce the release of Bitcoin Core 0.15.1.

This release focuses on the safety of the P2P network as a precaution against potential future network forks, as well as bringing bug fixes, optimisations and improvements to the 0.15.x series.

Notable changes

Network fork safety enhancements

A number of changes to the way Bitcoin Core deals with peer connections and invalid blocks have been made, as a safety precaution against blockchain forks and misbehaving peers.

• Unrequested blocks with less work than the minimum-chain-work are now no longer processed even if they have more work than the tip (a potential issue during IBD where the tip may have low-work). This prevents peers wasting the resources of a node.

• Peers which provide a chain with less work than the minimum-chain-work during IBD will now be disconnected.

• For a given outbound peer, we now check whether their best known block has at least as much work as our tip. If it doesn’t, and if we still haven’t heard about a block with sufficient work after a 20 minute timeout, then we send a single getheaders message, and wait 2 more minutes. If after two minutes their best known block has insufficient work, we disconnect that peer. We protect 4 of our outbound peers from being disconnected by this logic to prevent excessive network topology changes as a result of this algorithm, while still ensuring that we have a reasonable number of nodes not known to be on bogus chains.

• Outbound (non-manual) peers that serve us block headers that are already known to be invalid (other than compact block announcements, because BIP 152 explicitly permits nodes to relay compact blocks before fully validating them) will now be disconnected.

• If the chain tip has not been advanced for over 30 minutes, we now assume the tip may be stale and will try to connect to an additional outbound peer. A periodic check ensures that if this extra peer connection is in use, we will disconnect the peer that least recently announced a new block.

• The set of all known invalid-themselves blocks (i.e. blocks which we attempted to connect but which were found to be invalid) are now tracked and used to check if new headers build on an invalid chain. This ensures that everything that descends from an invalid block is marked as such.

RPC changes

• The currentblocksize value in getmininginfo has been removed.

• dumpwallet no longer allows overwriting files. This is a security measure as well as prevents dangerous user mistakes.

• backupwallet will now fail when attempting to backup to source file, rather than destroying the wallet.

• listsinceblock will now throw an error if an unknown blockhash argument value is passed, instead of returning a list of all wallet transactions since the genesis block. The behaviour is unchanged when an empty string is provided.

Miner block size limiting deprecated

Though blockmaxweight has been preferred for limiting the size of blocks returned by getblocktemplate since 0.13.0, blockmaxsize remained as an option for those who wished to limit their block size directly. Using this option resulted in a few UI issues as well as non-optimal fee selection and ever-so-slightly worse performance, and has thus now been deprecated. Further, the blockmaxsize option is now used only to calculate an implied blockmaxweight, instead of limiting block size directly. Any miners who wish to limit their blocks by size, instead of by weight, will have to do so manually by removing transactions from their block template directly.

GUI settings backed up on reset

The GUI settings will now be written to guisettings.ini.bak in the data directory before wiping them when the -resetguisettings argument is used. This can be used to retroactively troubleshoot issues due to the GUI settings.

Duplicate wallets disallowed

Previously, it was possible to open the same wallet twice by manually copying the wallet file, causing issues when both were opened simultaneously. It is no longer possible to open copies of the same wallet.

Debug -minimumchainwork argument added

A hidden debug argument -minimumchainwork has been added to allow a custom minimum work value to be used when validating a chain.

Conclusion

Please see the release notes for details. To download, please visit the download page.

If have any questions, please stop by either our IRC or Slack chatrooms and we’ll do our best to help you.

Hashes for verification

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Bitcoin Core