<nLockTime> CHECKLOCKTIMEVERIFY -> <nLockTime>
Fails if tx.nLockTime < nLockTime, allowing the funds in a txout to be
locked until some block height or block time in the future is reached.
Only the logic and unittests are implemented; this commit does not have
any actual soft-fork logic in it.
Thanks to Pieter Wuille for rebase.
Credit goes to Gregory Maxwell for the suggestion of comparing the
argument against the transaction nLockTime rather than the current
time/blockheight directly.
The lock-time code currently uses CBlock::nTime as the cutoff point for time based locked transactions. This has the unfortunate outcome of creating a perverse incentive for miners to lie about the time of a block in order to collect more fees by including transactions that by wall clock determination have not yet matured. By using CBlockIndex::GetMedianTimePast from the prior block instead, the self-interested miner no longer gains from generating blocks with fraudulent timestamps. Users can compensate for this change by simply adding an hour (3600 seconds) to their time-based lock times.
If enforced, this would be a soft-fork change. This commit only adds the functionality on an unexecuted code path, without changing the behaviour of Bitcoin Core.
In summary, the sequence number of each input in a transaction is used to store an inverted relative locktime: a delta value which is added to the height or time of the block which included the output being spent to generate a per-input lock time from the sequence number. If enforced, this would make transaction replacement possible as replacing an input with a higher sequence number (lower relative lock time) would allow the new transaction to make it on the chain sooner.
This commit does not implement the transaction replacement logic. Nor does this commit make the relative lock time rules as consensus or policy rules. It merely adds new, but disabled functionality and unit tests for that functionality.
Instead of checking if the transaction is in a category of cases to return true and failing otherwise, we return false if the tx is a failure case and otherwise return true. This removes an early-exit opportunity which will no longer be possible once sequence numbers are re-enabled, but has no change in behaviour.
Some tests in CheckBlockIndex require chainActive.Tip(), but when reindexing, chainActive has not been set on the first call to CheckBlockIndex.
reindex.py starts a node, mines 3 blocks, stops, and reindexes with CheckBlockIndex enabled.
Rebased-From: 0421c18f3a
Github-Pull: #6012
This adds a -checkblockindex (defaulting to true for regtest), which occasionally
does a full consistency check for mapBlockIndex, setBlockIndexCandidates, chainActive, and
mapBlocksUnlinked.
When re-indexing, there are a few cases where garbage data may be skipped in
the block files. In these cases, the indices are correctly written to the index
db, however the pointer to the next position for writing in the current block
file is calculated by adding the sizes of the valid blocks found.
As a result, when the re-index is finished, the index db is correct for all
existing blocks, but the next block will be written to an incorrect offset,
likely overwriting existing blocks.
Rather than using the sum of all valid blocks to determine the next write
position, use the end of the last block written to the file. Don't assume that
the current block is the last one in the file, since they may be read
out-of-order.
Rebased-From: bb6acff079
Github-Pull: #5864
The only time when a client sends a "getaddr" message is when he
esatblishes an Outbound connection (see ProcessMessage() in
src/main.cpp). Another bitcoin client is expected to receive a
"getaddr" message only on Inbound connection. Ignoring "gettaddr"
requests on Outbound connections can resolve potential privacy issues
(and as was said such request normally do not happen anyway).
Rebased-From: dca799e1db
Github-Pull: #5442
With headers-first we can compare against the best header timestamp, rather
than using checkpoints which require code updates to maintain.
Rebased-From: 85da07a5a0
Github-Pull: #5820
Normally bitcoin core does not display any network originated strings without
sanitizing or hex encoding. This wasn't done for strcommand in many places.
This could be used to play havoc with a terminal displaying the logs,
especially with printtoconsole in use.
Thanks to Evil-Knievel for reporting this issue.
Conflicts:
src/main.cpp
This harmonizes the block fetch timeout with the existing ping timeout
and eliminates a guaranteed eventual failure from congestion collapse
for a network operating right at its limit.
It's unlikely that we wouldn't suffer other failures if we were really
anywhere near the network's limit, and a complete avoidance of congestion
collapse risk requires (I think) an exponential back-off. So this isn't
a major concern, but I think it's also useful for reducing the complexity
of understanding out timeouts.
Github-Pull: #5647
Rebased-From: 3ff735c99a
This will disconnect peers that do not transfer a block in 10 minutes, plus
5 minutes for every previously queued block with validated headers
(accomodating downstream bandwidth down to a few kilobytes per second - below
that the node would have trouble staying synchronized anyway).
Github-Pull: #5608
Rebased-From: 916130348c
With the splashscreen being able to be closed it is possible to
shutdown during the lengthy verifyDB method. (Takes about a minute
on my machine). This change allows us to shutdown much sooner.
Github-Pull: #5557
Rebased-From: 70477a0bdf
Don't allow immediate inv driven block downloads if
a peer already has MAX_BLOCKS_IN_TRANSIT_PER_PEER
active downloads. Prevents bogus inv spam from
blowing up block transfer tracking data structures.
Rebased-From: c90770430d
Github-Pull: #5507
Previously transactions were only tested again the
STANDARD_SCRIPT_VERIFY_FLAGS prior to mempool acceptance, so any bugs in
those flags that allowed actually-invalid transactions to pass would
result in allowing invalid transactions into the mempool. Fortunately
there is a second check in CreateNewBlock() that would prevent those
transactions from being mined, resulting in an invalid block, however
this could still be exploited as a DoS attack.
Rebased-From: 7c041b3b91
This still leaves transactions in mempool that are potentially
invalid if the maturity period has been reorged out of, but at
least they're not missing inputs entirely.
9ec75c5 Add a locking mechanism to IsInitialBlockDownload to ensure it never goes from false to true. (Ruben Dario Ponticelli)
a2d0fc6 Fix IsInitialBlockDownload which was broken by headers first. (Ruben Dario Ponticelli)
There are 3 pieces of data that are maintained on disk. The actual block
and undo data, the block index (which can refer to positions on disk),
and the chainstate (which refers to the best block hash).
Earlier, there was no guarantee that blocks were written to disk before
block index entries referring to them were written. This commit introduces
dirty flags for block index data, and delays writing entries until the actual
block data is flushed.
With this stricter ordering in writes, it is now safe to not always flush
after every block, so there is no need for the IsInitialBlockDownload()
check there - instead we just write whenever enough time has passed or
the cache size grows too large. Also updating the wallet's best known block
is delayed until this is done, otherwise the wallet may end up referring to an
unknown block.
In addition, only do a write inside the block processing loop if necessary
(because of cache size exceeded). Otherwise, move the writing to a point
after processing is done, after relaying.
Like in a real world situation, a safe mode test should also be visible in the
UI. A test of safe mode is furthermore mostly relevant for developers, so it
should not be overwritten by a warning about a pre-release test build.
