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// Copyright (c) 2016-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <policy/rbf.h>
#include <policy/settings.h>
#include <tinyformat.h>
#include <util/moneystr.h>
#include <util/rbf.h>
RBFTransactionState IsRBFOptIn(const CTransaction& tx, const CTxMemPool& pool)
{
AssertLockHeld(pool.cs);
CTxMemPool::setEntries setAncestors;
// First check the transaction itself.
if (SignalsOptInRBF(tx)) {
return RBFTransactionState::REPLACEABLE_BIP125;
}
// If this transaction is not in our mempool, then we can't be sure
// we will know about all its inputs.
if (!pool.exists(tx.GetHash())) {
return RBFTransactionState::UNKNOWN;
}
// If all the inputs have nSequence >= maxint-1, it still might be
// signaled for RBF if any unconfirmed parents have signaled.
uint64_t noLimit = std::numeric_limits<uint64_t>::max();
std::string dummy;
CTxMemPoolEntry entry = *pool.mapTx.find(tx.GetHash());
pool.CalculateMemPoolAncestors(entry, setAncestors, noLimit, noLimit, noLimit, noLimit, dummy, false);
for (CTxMemPool::txiter it : setAncestors) {
if (SignalsOptInRBF(it->GetTx())) {
return RBFTransactionState::REPLACEABLE_BIP125;
}
}
return RBFTransactionState::FINAL;
}
RBFTransactionState IsRBFOptInEmptyMempool(const CTransaction& tx)
{
// If we don't have a local mempool we can only check the transaction itself.
return SignalsOptInRBF(tx) ? RBFTransactionState::REPLACEABLE_BIP125 : RBFTransactionState::UNKNOWN;
}
std::optional<std::string> GetEntriesForConflicts(const CTransaction& tx,
CTxMemPool& m_pool,
const CTxMemPool::setEntries& setIterConflicting,
CTxMemPool::setEntries& allConflicting)
{
AssertLockHeld(m_pool.cs);
const uint256 hash = tx.GetHash();
uint64_t nConflictingCount = 0;
for (const auto& mi : setIterConflicting) {
nConflictingCount += mi->GetCountWithDescendants();
// This potentially overestimates the number of actual descendants
// but we just want to be conservative to avoid doing too much
// work.
if (nConflictingCount > MAX_BIP125_REPLACEMENT_CANDIDATES) {
return strprintf("rejecting replacement %s; too many potential replacements (%d > %d)\n",
hash.ToString(),
nConflictingCount,
MAX_BIP125_REPLACEMENT_CANDIDATES);
}
}
// If not too many to replace, then calculate the set of
// transactions that would have to be evicted
for (CTxMemPool::txiter it : setIterConflicting) {
m_pool.CalculateDescendants(it, allConflicting);
}
return std::nullopt;
}
std::optional<std::string> HasNoNewUnconfirmed(const CTransaction& tx,
const CTxMemPool& m_pool,
const CTxMemPool::setEntries& setIterConflicting)
{
AssertLockHeld(m_pool.cs);
std::set<uint256> setConflictsParents;
for (const auto& mi : setIterConflicting) {
for (const CTxIn &txin : mi->GetTx().vin)
{
setConflictsParents.insert(txin.prevout.hash);
}
}
for (unsigned int j = 0; j < tx.vin.size(); j++)
{
// We don't want to accept replacements that require low
// feerate junk to be mined first. Ideally we'd keep track of
// the ancestor feerates and make the decision based on that,
// but for now requiring all new inputs to be confirmed works.
//
// Note that if you relax this to make RBF a little more useful,
// this may break the CalculateMempoolAncestors RBF relaxation,
// above. See the comment above the first CalculateMempoolAncestors
// call for more info.
if (!setConflictsParents.count(tx.vin[j].prevout.hash))
{
// Rather than check the UTXO set - potentially expensive -
// it's cheaper to just check if the new input refers to a
// tx that's in the mempool.
if (m_pool.exists(tx.vin[j].prevout.hash)) {
return strprintf("replacement %s adds unconfirmed input, idx %d",
tx.GetHash().ToString(), j);
}
}
}
return std::nullopt;
}
std::optional<std::string> EntriesAndTxidsDisjoint(const CTxMemPool::setEntries& setAncestors,
const std::set<uint256>& setConflicts,
const uint256& txid)
{
for (CTxMemPool::txiter ancestorIt : setAncestors)
{
const uint256 &hashAncestor = ancestorIt->GetTx().GetHash();
if (setConflicts.count(hashAncestor))
{
return strprintf("%s spends conflicting transaction %s",
txid.ToString(),
hashAncestor.ToString());
}
}
return std::nullopt;
}
std::optional<std::string> PaysMoreThanConflicts(const CTxMemPool::setEntries& setIterConflicting,
CFeeRate newFeeRate,
const uint256& hash)
{
for (const auto& mi : setIterConflicting) {
// Don't allow the replacement to reduce the feerate of the
// mempool.
//
// We usually don't want to accept replacements with lower
// feerates than what they replaced as that would lower the
// feerate of the next block. Requiring that the feerate always
// be increased is also an easy-to-reason about way to prevent
// DoS attacks via replacements.
//
// We only consider the feerates of transactions being directly
// replaced, not their indirect descendants. While that does
// mean high feerate children are ignored when deciding whether
// or not to replace, we do require the replacement to pay more
// overall fees too, mitigating most cases.
CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
if (newFeeRate <= oldFeeRate)
{
return strprintf("rejecting replacement %s; new feerate %s <= old feerate %s",
hash.ToString(),
newFeeRate.ToString(),
oldFeeRate.ToString());
}
}
return std::nullopt;
}
std::optional<std::string> PaysForRBF(CAmount nConflictingFees,
CAmount nModifiedFees,
size_t nSize,
const uint256& hash)
{
// The replacement must pay greater fees than the transactions it
// replaces - if we did the bandwidth used by those conflicting
// transactions would not be paid for.
if (nModifiedFees < nConflictingFees)
{
return strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees));
}
// Finally in addition to paying more fees than the conflicts the
// new transaction must pay for its own bandwidth.
CAmount nDeltaFees = nModifiedFees - nConflictingFees;
if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
{
return strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
hash.ToString(),
FormatMoney(nDeltaFees),
FormatMoney(::incrementalRelayFee.GetFee(nSize)));
}
return std::nullopt;
}
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