Previously Bitcoin would send 1/4 of transactions out to all peers
instantly. This causes high overhead because it makes >80% of
INVs size 1. Doing so harms privacy, because it limits the
amount of source obscurity a transaction can receive.
These randomized broadcasts also disobeyed transaction dependencies
and required use of the orphan pool. Because the orphan pool is
so small this leads to poor propagation for dependent transactions.
When the bypass wasn't in effect, transactions were sent in the
order they were received. This avoided creating orphans but
undermines privacy fairly significantly.
This commit:
Eliminates the bypass. The bypass is replaced by halving the
average delay for outbound peers.
Sorts candidate transactions for INV by their topological
depth then by their feerate (then hash); removing the
information leakage and providing priority service to
higher fee transactions.
Limits the amount of transactions sent in a single INV to
7tx/sec (and twice that for outbound); this limits the
harm of low fee transaction floods, gives faster relay
service to higher fee transactions. The 7 sounds lower
than it really is because received advertisements need
not be sent, and because the aggregate rate is multipled
by the number of peers.
The "feefilter" p2p message is used to inform other nodes of your mempool min fee which is the feerate that any new transaction must meet to be accepted to your mempool. This will allow them to filter invs to you according to this feerate.
This implements caching of ancestor state to each mempool entry, similar to
descendant tracking, but also including caching sigops-with-ancestors (as that
metric will be helpful to future code that implements better transaction
selection in CreatenewBlock).
The work limit served to prevent the descendant walking algorithm from doing
too much work by marking the parent transaction as dirty. However to implement
ancestor tracking, it's not possible to similarly mark those descendant
transactions as dirty without having to calculate them to begin with.
This commit removes the work limit altogether. With appropriate
chain limits (-limitdescendantcount) the concern about doing too much
work inside this function should be mitigated.
SequenceLocks functions are used to evaluate sequence lock times or heights per BIP 68.
The majority of this code is copied from maaku in #6312
Further credit: btcdrak, sipa, NicolasDorier
Redo the feerate index to be based on mining score, rather than fee.
Update mempool_packages.py to test prioritisetransaction's effect on
package scores.
The score index is meant to represent the order of priority for being included in a block for miners. Initially this is set to the transactions modified (by any feeDelta) fee rate. Index improvements and unit tests by sdaftuar.
Store sum of legacy and P2SH sig op counts. This is calculated in AcceptToMemory pool and storing it saves redoing the expensive calculation in block template creation.
Compute the value of inputs that already are in the chain at time of mempool entry and only increase priority due to aging for those inputs. This effectively changes the CTxMemPoolEntry's GetPriority calculation from an upper bound to a lower bound.
These are more useful fee and priority estimation functions. If there is no fee/pri high enough for the target you are aiming for, it will give you the estimate for the lowest target that you can reliably obtain. This is better than defaulting to the minimum. It will also pass back the target for which it returned an answer.
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)
CalculateMemPoolAncestors was always looping over a transaction's inputs
to find in-mempool parents. When adding a new transaction, this is the
correct behavior, but when removing a transaction, we want to use the
ancestor set that would be calculated by walking mapLinks (which should
in general be the same set, except during a reorg when the mempool is
in an inconsistent state, and the mapLinks-based calculation would be the
correct one).
Associate with each CTxMemPoolEntry all the size/fees of descendant
mempool transactions. Sort mempool by max(feerate of entry, feerate
of descendants). Update statistics on-the-fly as transactions enter
or leave the mempool.
Also add ancestor and descendant limiting, so that transactions can
be rejected if the number or size of unconfirmed ancestors exceeds
a target, or if adding a transaction would cause some other mempool
entry to have too many (or too large) a set of unconfirmed in-
mempool descendants.
This class groups transactions that have been confirmed in blocks into buckets, based on either their fee or their priority. Then for each bucket, the class calculates what percentage of the transactions were confirmed within various numbers of blocks. It does this by keeping an exponentially decaying moving history for each bucket and confirm block count of the percentage of transactions in that bucket that were confirmed within that number of blocks.
-Eliminate txs which didn't have all inputs available at entry from fee/pri calcs
-Add dynamic breakpoints and tracking of confirmation delays in mempool transactions
-Remove old CMinerPolicyEstimator and CBlockAverage code
-New smartfees.py
-Pass a flag to the estimation code, using IsInitialBlockDownload as a proxy for when we are still catching up and we shouldn't be counting how many blocks it takes for transactions to be included.
-Add a policyestimator unit test
This fixes a subtle bug involving block re-orgs and non-standard transactions.
Start with a block containing a non-standard transaction, and
one or more transactions spending it in the memory pool.
Then re-org away from that block to another chain that does
not contain the non-standard transaction.
Result before this fix: the dependent transactions get stuck
in the mempool without their parent, putting the mempool
in an inconsistent state.
Tested with a new unit test.
'Sane' was already defined by this code as:
fee.GetFeePerK() > minRelayFee.GetFeePerK() * 10000
But sanity was only enforced for data loaded from disk.
Note that this is a pretty expansive definition of 'sane': A 10 BTC
fee is still passes the test if its on a 100kb transaction.
This prevents a single insane fee on the network from making us reject
our stored fee data at start. We still may reject valid saved fee
state if minRelayFee is changed between executions.
This also reduces the risk and limits the damage from a cascading
failure where one party pays a bunch of insane fees which cases
others to pay insane fees.
7c70438 Get rid of the dummy CCoinsViewCache constructor arg (Pieter Wuille)
ed27e53 Add coins_tests with a large randomized CCoinViewCache test. (Pieter Wuille)
058b08c Do not keep fully spent but unwritten CCoins entries cached. (Pieter Wuille)
c9d1a81 Get rid of CCoinsView's SetCoins and SetBestBlock. (Pieter Wuille)
f28aec0 Use ModifyCoins instead of mutable GetCoins. (Pieter Wuille)
The efficient version of CCoinsViewCache::GetCoins only works for known-to-exist
cache entries, requiring a separate HaveCoins call beforehand. This is
inefficient as both perform a hashtable lookup.
Replace the non-mutable GetCoins with AccessCoins, which returns a potentially-NULL
pointer. This also decreases the overloading of GetCoins.
Also replace some copying (inefficient) GetCoins calls with equivalent AccessCoins,
decreasing the copying.
ad49c25 Split up util.cpp/h (Wladimir J. van der Laan)
f841aa2 Move `COIN` and `CENT` to core.h (Wladimir J. van der Laan)
6e5fd00 Move `*Version()` functions to version.h/cpp (Wladimir J. van der Laan)
b4aa769 Move `S_I*` constants and `MSG_NOSIGNAL` to compat.h (Wladimir J. van der Laan)
af8297c Move functions in wallet.h to implementation file (Wladimir J. van der Laan)
651480c move functions in main and net to implementation files (Wladimir J. van der Laan)
610a8c0 Move SetThreadPriority implementation to util.cpp instead of the header (Wladimir J. van der Laan)
f780e65 Remove unused function `ByteReverse` from util.h (Wladimir J. van der Laan)
121d6ad Remove unused `alignup` function from util.h (Wladimir J. van der Laan)
d1e26d4 Move CMedianFilter to timedata.cpp (Wladimir J. van der Laan)
Split up util.cpp/h into:
- string utilities (hex, base32, base64): no internal dependencies, no dependency on boost (apart from foreach)
- money utilities (parsesmoney, formatmoney)
- time utilities (gettime*, sleep, format date):
- and the rest (logging, argument parsing, config file parsing)
The latter is basically the environment and OS handling,
and is stripped of all utility functions, so we may want to
rename it to something else than util.cpp/h for clarity (Matt suggested
osinterface).
Breaks dependency of sha256.cpp on all the things pulled in by util.
Allows network wallets and other clients to see transactions that respend
a prevout already spent in an unconfirmed transaction in this node's mempool.
Knowledge of an attempted double-spend is of interest to recipients of the
first spend. In some cases, it will allow these recipients to withhold
goods or services upon being alerted of a double-spend that deprives them
of payment.
As before, respends are not added to the mempool.
Anti-Denial-of-Service-Attack provisions:
- Use a bloom filter to relay only one respend per mempool prevout
- Rate-limit respend relays to a default of 100 thousand bytes/minute
- Define tx2.IsEquivalentTo(tx1): equality when scriptSigs are not considered
- Do not relay these equivalent transactions
Remove an unused variable declaration in txmempool.cpp.
New RPC methods: return an estimate of the fee (or priority) a
transaction needs to be likely to confirm in a given number of
blocks.
Mike Hearn created the first version of this method for estimating fees.
It works as follows:
For transactions that took 1 to N (I picked N=25) blocks to confirm,
keep N buckets with at most 100 entries in each recording the
fees-per-kilobyte paid by those transactions.
(separate buckets are kept for transactions that confirmed because
they are high-priority)
The buckets are filled as blocks are found, and are saved/restored
in a new fee_estiamtes.dat file in the data directory.
A few variations on Mike's initial scheme:
To estimate the fee needed for a transaction to confirm in X buckets,
all of the samples in all of the buckets are used and a median of
all of the data is used to make the estimate. For example, imagine
25 buckets each containing the full 100 entries. Those 2,500 samples
are sorted, and the estimate of the fee needed to confirm in the very
next block is the 50'th-highest-fee-entry in that sorted list; the
estimate of the fee needed to confirm in the next two blocks is the
150'th-highest-fee-entry, etc.
That algorithm has the nice property that estimates of how much fee
you need to pay to get confirmed in block N will always be greater
than or equal to the estimate for block N+1. It would clearly be wrong
to say "pay 11 uBTC and you'll get confirmed in 3 blocks, but pay
12 uBTC and it will take LONGER".
A single block will not contribute more than 10 entries to any one
bucket, so a single miner and a large block cannot overwhelm
the estimates.
