Until now there were quite a few leftovers, and only the coverage
related files in `src/` were cleaned, while the ones in the other dirs
remained. `qa/tmp/` is related to the BitcoinJ tests, and `cache/` is
related to RPC tests.
Transactions are not allowed in the memory pool or selected for inclusion in a block until their lock times exceed chainActive.Tip()->GetMedianTimePast(). However blocks including transactions which are only mature under the old rules are still accepted; this is *not* the soft-fork required to actually rely on the new constraint in production.
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.
Nagle appears to be a significant contributor to latency now that the static
sleeps are gone. Most of our messages are relatively large compared to
IP + TCP so I do not expect this to create enormous overhead.
This may also reduce traffic burstyness somewhat.
Add a comment that explains why the initial "getheader" requests are
made starting from the block preceding the currently best one.
Thanks to sdaftuar for the explanation!
There is no exact science to setting this parameter, but 5000
(just over 1 US cent at the time of writing) is higher than the
cost to relay a transaction around the network (the new benchmark
due to mempool limiting).
After each transaction which is added to mempool, we first call
Expire() to remove old transactions, then throwing away the
lowest-feerate transactions.
After throwing away transactions by feerate, we set the minimum
relay fee to the maximum fee transaction-and-dependant-set we
removed, plus the default minimum relay fee.
After the next block is received, the minimum relay fee is allowed
to decrease exponentially. Its halflife defaults to 12 hours, but
is decreased to 6 hours if the mempool is smaller than half its
maximum size, and 3 hours if the mempool is smaller than a quarter
its maximum size.
The minimum -maxmempool size is 40*-limitdescendantsize, as it is
easy for an attacker to play games with the cheapest
-limitdescendantsize transactions. -maxmempool defaults to 300MB.
This disables high-priority transaction relay when the min relay
fee adjustment is >0 (ie when the mempool is full). When the relay
fee adjustment drops below the default minimum relay fee / 2 it is
set to 0 (re-enabling priority-based free relay).
(note the 9x multiplier on (void*)'s for CTxMemPool::DynamicMemoryUsage
was accidentally introduced in 5add7a7 but should have waited for this
commit which adds the extra index)
To bridge the time until a dynamic method for determining this fee is
merged.
This is especially aimed at the stable releases (0.10, 0.11) because
full mempool limiting, as will be in 0.12, is too invasive and risky to
backport.
Adds an `obfuscate` parameter to `CLevelDBWrapper` and makes use of it
for all new chainstate stores built via `CCoinsViewDB`. Also adds an
`Xor` method to `CDataStream`.
Thanks to @sipa@laanwj@pstratem@dexX7@KyrosKrane@gmaxwell.
This adds SCRIPT_VERIFY_LOW_S to STANDARD_SCRIPT_VERIFY_FLAGS which
will make the node require the canonical 'low-s' encoding for
ECDSA signatures when relaying or mining.
Consensus behavior is unchanged.
The rational is explained in a81cd96805ce6b65cca3a40ebbd3b2eb428abb7b:
Absent this kind of test ECDSA is not a strong signature as given
a valid signature {r, s} both that value and {r, -s mod n} are valid.
These two encodings have different hashes allowing third parties a
vector to change users txids. These attacks are avoided by picking
a particular form as canonical and rejecting the other form(s); in
the of the LOW_S rule, the smaller of the two possible S values is
used.
If widely deployed this change would eliminate the last remaining
known vector for nuisance malleability on boring SIGHASH_ALL
p2pkh transactions. On the down-side it will block most
transactions made by sufficiently out of date software.
Unlike the other avenues to change txids on boring transactions this
one was randomly violated by all deployed bitcoin software prior to
its discovery. So, while other malleability vectors where made
non-standard as soon as they were discovered, this one has remained
permitted. Even BIP62 did not propose applying this rule to
old version transactions, but conforming implementations have become
much more common since BIP62 was initially written.
Bitcoin Core has produced compatible signatures since a28fb70e in
September 2013, but this didn't make it into a release until 0.9
in March 2014; Bitcoinj has done so for a similar span of time.
Bitcoinjs and electrum have been more recently updated.
This does not replace the need for BIP62 or similar, as miners can
still cooperate to break transactions. Nor does it replace the
need for wallet software to handle malleability sanely[1]. This
only eliminates the cheap and irritating DOS attack.
[1] On the Malleability of Bitcoin Transactions
Marcin Andrychowicz, Stefan Dziembowski, Daniel Malinowski, Łukasz Mazurek
http://fc15.ifca.ai/preproceedings/bitcoin/paper_9.pdf
Jonas Schnelli