We should not proceed syncing headers from peers when the local system clock is incorrectly set.
A node with a system clock set too far back will typically fail early during startup when the chainstate detects the tip to be too far in the future. This means that in practice we don't expect the failure to ever happen in net_processing.cpp.
An exception is thrown from HeadersSyncState() in order to only compute the error condition once. An alternative would be to compute it a second time in TryLowWorkHeadersSync() to guard against calling HeadersSyncState(), and have an assert inside HeadersSyncState(). We shut down the process so possible resource leaks due to the exception should not be an issue, although none have been spotted. Throwing an exception also keeps the unit test straightforward.
Co-authored-by: Lőrinc <pap.lorinc@gmail.com>
chain_start can never be null, so it's better to pass it as a reference
rather than a raw pointer
Also slightly reformat HeaderSyncState constructor to make clang-format
happy
Lastly, remove `const` from `chain_start` declaration in
headers_sync_chainwork_tests, to work aroud a false-positive
dangling-reference warning in gcc 13.0
Co-Authored-By: maflcko <6399679+maflcko@users.noreply.github.com>
Move calculated constants from the top of src/headerssync.cpp into src/kernel/chainparams.cpp.
Instead of being hardcoded to mainnet parameters, HeadersSyncState can now vary depending on chain or test. (This means we can reset TARGET_BLOCKS back to the nice round number of 15'000).
Signet and testnets got new HeadersSyncParams constants through temporarily altering headerssync-params.py with corresponding GENESIS_TIME and MINCHAINWORK_HEADERS (based off defaultAssumeValid block height comments, corresponding to nMinimumChainWork). Regtest doesn't have a default assume valid block height, so the values are copied from Testnet 4. Since the constants only affect memory usage, and have very low impact unless dealing with a largely malicious chain, it's not that critical to keep updating them for non-mainnet chains.
GENESIS_TIMEs (UTC):
Testnet3: 1296688602 = datetime(2011, 2, 2)
Testnet4: 1714777860 = datetime(2024, 5, 3)
Signet: 1598918400 = datetime(2020, 9, 1)
These remaining miscellaneous changes were identified by commenting out
the `operator const uint256&` conversion and the `Compare(const uint256&)`
method from `transaction_identifier.h`.
We don't add or maintain these, and they are of little value, as
well as having the effect of polluting diffs.
They are also wrong, i.e DEFAULT_SCRIPTCHECK_THREADS is not in
validation.h.
Avoid permanently storing headers from a peer, unless the headers are part of a
chain with sufficiently high work. This prevents memory attacks using low-work
headers.
Designed and co-authored with Pieter Wuille.
