This clarifies a bit more the ways in which the new script execution
cache could break consensus in the future if additional data from
the CCoins object were to be used as a part of script execution.
After this change, any such consensus breaks should be very visible
to reviewers, hopefully ensuring no such changes can be made.
Rather than re-add disconnected block transactions back to the mempool
immediately, store them in a separate disconnectpool for later processing,
because we expect most such transactions to reappear in the chain that is
still to be connected (and thus we can avoid the work of reprocessing those
transactions through the mempool altogether).
Mempool persistence was added in
3f78562df5, and is always on. This commit
introduces a command-line parameter -persistmempool, which defaults to
true. When set to false:
- mempool.dat is not loaded when the node starts.
- mempool.dat is not written when the node stops.
Remove -limitfreerelay and always enforce minRelayTxFee in the mempool (except from disconnected blocks)
Remove -relaypriority, the option was only used for the ability to allow free transactions to be relayed regardless of their priority. Both notions no longer apply.
This disentangles the script validation skipping from checkpoints.
A new option is introduced "assumevalid" which specifies a block whos
ancestors we assume all have valid scriptsigs and so we do not check
them when they are also burried under the best header by two weeks
worth of work.
Unlike checkpoints this has no influence on consensus unless you set
it to a block with an invalid history. Because of this it can be
easily be updated without risk of influencing the network consensus.
This results in a massive IBD speedup.
This approach was independently recommended by Peter Todd and Luke-Jr
since POW based signature skipping (see PR#9180) does not have the
verifiable properties of a specific hash and may create bad incentives.
The downside is that, like checkpoints, the defaults bitrot and older
releases will sync slower. On the plus side users can provide their
own value here, and if they set it to something crazy all that will
happen is more time will be spend validating signatures.
Checkblocks and checklevel are also moved to the hidden debug options:
Especially now that checkblocks has a low default there is little need
to change these settings, and users frequently misunderstand them as
influencing security or IBD speed. By hiding them we offset the
space added by this new option.
Make a more conservative notion of whether the node is caught up to the rest of the network and only count transactions as fee estimation data points if the node is caught up.
UnloadBlockIndex is only used during init if we end up reindexing
to clear our block state so that we can start over. However, at
that time no connections have been brought up as CConnman hasn't
been started yet, so all of the network processing state logic is
empty when its called.
Additionally, the initialization of the recentRejects set is moved
to InitPeerLogic.
Matt Corallo