CFeeBumper::CFeeBumper(const CWallet *pWallet, const uint256 txidIn, int newConfirmTarget, bool specifiedConfirmTarget, CAmount totalFee, bool newTxReplaceable)
:
txid(std::move(txidIn)),
nOldFee(0),
nNewFee(0)
{
vErrors.clear();
bumpedTxid.SetNull();
AssertLockHeld(pWallet->cs_wallet);
if (!pWallet->mapWallet.count(txid)) {
vErrors.push_back("Invalid or non-wallet transaction id");
currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
return;
}
auto it = pWallet->mapWallet.find(txid);
const CWalletTx& wtx = it->second;
if (!preconditionChecks(pWallet, wtx)) {
return;
}
if (!SignalsOptInRBF(wtx)) {
vErrors.push_back("Transaction is not BIP 125 replaceable");
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
if (wtx.mapValue.count("replaced_by_txid")) {
vErrors.push_back(strprintf("Cannot bump transaction %s which was already bumped by transaction %s", txid.ToString(), wtx.mapValue.at("replaced_by_txid")));
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// check that original tx consists entirely of our inputs
// if not, we can't bump the fee, because the wallet has no way of knowing the value of the other inputs (thus the fee)
if (!pWallet->IsAllFromMe(wtx, ISMINE_SPENDABLE)) {
vErrors.push_back("Transaction contains inputs that don't belong to this wallet");
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// figure out which output was change
// if there was no change output or multiple change outputs, fail
int nOutput = -1;
for (size_t i = 0; i < wtx.tx->vout.size(); ++i) {
if (pWallet->IsChange(wtx.tx->vout[i])) {
if (nOutput != -1) {
vErrors.push_back("Transaction has multiple change outputs");
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
nOutput = i;
}
}
if (nOutput == -1) {
vErrors.push_back("Transaction does not have a change output");
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// Calculate the expected size of the new transaction.
int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
const int64_t maxNewTxSize = CalculateMaximumSignedTxSize(*wtx.tx, pWallet);
if (maxNewTxSize < 0) {
vErrors.push_back("Transaction contains inputs that cannot be signed");
currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
return;
}
// calculate the old fee and fee-rate
nOldFee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
CFeeRate nOldFeeRate(nOldFee, txSize);
CFeeRate nNewFeeRate;
// The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
// future proof against changes to network wide policy for incremental relay
// fee that our node may not be aware of.
CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
if (::incrementalRelayFee > walletIncrementalRelayFee) {
walletIncrementalRelayFee = ::incrementalRelayFee;
}
if (totalFee > 0) {
CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + ::incrementalRelayFee.GetFee(maxNewTxSize);
if (totalFee < minTotalFee) {
vErrors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(::incrementalRelayFee.GetFee(maxNewTxSize))));
currentResult = BumpFeeResult::INVALID_PARAMETER;
return;
}
CAmount requiredFee = CWallet::GetRequiredFee(maxNewTxSize);
if (totalFee < requiredFee) {
vErrors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
FormatMoney(requiredFee)));
currentResult = BumpFeeResult::INVALID_PARAMETER;
return;
}
nNewFee = totalFee;
nNewFeeRate = CFeeRate(totalFee, maxNewTxSize);
} else {
// if user specified a confirm target then don't consider any global payTxFee
if (specifiedConfirmTarget) {
nNewFee = CWallet::GetMinimumFee(maxNewTxSize, newConfirmTarget, mempool, ::feeEstimator, true);
}
// otherwise use the regular wallet logic to select payTxFee or default confirm target
else {
nNewFee = CWallet::GetMinimumFee(maxNewTxSize, newConfirmTarget, mempool, ::feeEstimator);
}
nNewFeeRate = CFeeRate(nNewFee, maxNewTxSize);
// New fee rate must be at least old rate + minimum incremental relay rate
// walletIncrementalRelayFee.GetFeePerK() should be exact, because it's initialized
// in that unit (fee per kb).
// However, nOldFeeRate is a calculated value from the tx fee/size, so
// add 1 satoshi to the result, because it may have been rounded down.
if (nNewFeeRate.GetFeePerK() < nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK()) {
nNewFeeRate = CFeeRate(nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK());
nNewFee = nNewFeeRate.GetFee(maxNewTxSize);
}
}
// Check that in all cases the new fee doesn't violate maxTxFee
if (nNewFee > maxTxFee) {
vErrors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
FormatMoney(nNewFee), FormatMoney(maxTxFee)));
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// check that fee rate is higher than mempool's minimum fee
// (no point in bumping fee if we know that the new tx won't be accepted to the mempool)
// This may occur if the user set TotalFee or paytxfee too low, if fallbackfee is too low, or, perhaps,
// in a rare situation where the mempool minimum fee increased significantly since the fee estimation just a
// moment earlier. In this case, we report an error to the user, who may use totalFee to make an adjustment.
CFeeRate minMempoolFeeRate = mempool.GetMinFee(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
if (nNewFeeRate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
vErrors.push_back(strprintf("New fee rate (%s) is less than the minimum fee rate (%s) to get into the mempool. totalFee value should to be at least %s or settxfee value should be at least %s to add transaction.", FormatMoney(nNewFeeRate.GetFeePerK()), FormatMoney(minMempoolFeeRate.GetFeePerK()), FormatMoney(minMempoolFeeRate.GetFee(maxNewTxSize)), FormatMoney(minMempoolFeeRate.GetFeePerK())));
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// Now modify the output to increase the fee.
// If the output is not large enough to pay the fee, fail.
CAmount nDelta = nNewFee - nOldFee;
assert(nDelta > 0);
mtx = *wtx.tx;
CTxOut* poutput = &(mtx.vout[nOutput]);
if (poutput->nValue < nDelta) {
vErrors.push_back("Change output is too small to bump the fee");
currentResult = BumpFeeResult::WALLET_ERROR;
return;
}
// If the output would become dust, discard it (converting the dust to fee)
poutput->nValue -= nDelta;
if (poutput->nValue <= GetDustThreshold(*poutput, ::dustRelayFee)) {
LogPrint(BCLog::RPC, "Bumping fee and discarding dust output\n");
nNewFee += poutput->nValue;
mtx.vout.erase(mtx.vout.begin() + nOutput);
}
// Mark new tx not replaceable, if requested.
if (!newTxReplaceable) {
for (auto& input : mtx.vin) {
if (input.nSequence < 0xfffffffe) input.nSequence = 0xfffffffe;
}
}
currentResult = BumpFeeResult::OK;
}
bool IsDust(const CTxOut& txout, const CFeeRate& dustRelayFeeIn)
{
return (txout.nValue < GetDustThreshold(txout, dustRelayFeeIn));
}
