* IBD check uses minimumchain work instead of checkpoints.
This introduces a 'minimum chain work' chainparam which is intended
to be the known amount of work in the chain for the network at the
time of software release. If you don't have this much work, you're
not yet caught up.
This is used instead of the count of blocks test from checkpoints.
This criteria is trivial to keep updated as there is no element of
subjectivity, trust, or position dependence to it. It is also a more
reliable metric of sync status than a block count.
* Remove GetTotalBlocksEstimate and checkpoint tests that test nothing.
GetTotalBlocksEstimate is no longer used and it was the only thing
the checkpoint tests were testing.
Since checkpoints are on their way out it makes more sense to remove
the test file than to cook up a new pointless test.
# Conflicts:
# src/Makefile.test.include
# src/test/Checkpoints_tests.cpp
* IsInitialBlockDownload no longer uses header-only timestamps.
This avoids a corner case (mostly visible on testnet) where bogus
headers can keep nodes in IsInitialBlockDownload.
* Delay parallel block download until chain has sufficient work
nMinimumChainWork is an anti-DoS threshold; wait until we have a proposed
tip with more work than that before downloading blocks towards that tip.
* Add timeout for headers sync
At startup, we choose one peer to serve us the headers chain, until
our best header is close to caught up. Disconnect this peer if more
than 15 minutes + 1ms/expected_header passes and our best header
is still more than 1 day away from current time.
* Introduce assumevalid setting to skip presumed valid scripts.
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.
* Add consensusParams to FindNextBlocksToDownload
* Adjust check in headers timeout logic to align with 144 blocks in Dash
* Remove orphan state wipe from UnloadBlockIndex.
As orphan state is now "network state", like in
d6ea737be1,
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.
* Move network-msg-processing code out of main to its own file
* Rename the remaining main.{h,cpp} to validation.{h,cpp}
