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Enforce minRelayTxFee on wallet created tx and add a maxtxfee option.

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Previously the minRelayTxFee was only enforced on user specified values.

It was possible for smartfee to produce a fee below minRelayTxFee which
 would just result in the transaction getting stuck because it can't be
 relayed.

This also introduces a maxtxfee option which sets an absolute maximum
 for any fee created by the wallet, with an intention of increasing
 user confidence that the automatic fees won't burn them. This was
 frequently a concern even before smartfees.

If the configured fee policy won't even allow the wallet to meet the relay
 fee the transaction creation may be aborted.
This commit is contained in:
Gregory Maxwell 2014-12-16 01:43:40 -08:00
parent bf4bf40a1c
commit aa279d6131
3 changed files with 49 additions and 20 deletions
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15
src/init.cpp
View file

@ -288,6 +288,7 @@ std::string HelpMessage(HelpMessageMode mode)
strUsage += " -sendfreetransactions " + strprintf(_("Send transactions as zero-fee transactions if possible (default: %u)"), 0) + "\n";
strUsage += " -spendzeroconfchange " + strprintf(_("Spend unconfirmed change when sending transactions (default: %u)"), 1) + "\n";
strUsage += " -txconfirmtarget=<n> " + strprintf(_("If paytxfee is not set, include enough fee so transactions are confirmed on average within n blocks (default: %u)"), 1) + "\n";
strUsage += " -maxtxfee=<amt> " + strprintf(_("Maximum total fees to use in a single wallet transaction, setting too low may abort large transactions (default: %s)"), FormatMoney(maxTxFee)) + "\n";
strUsage += " -upgradewallet " + _("Upgrade wallet to latest format") + " " + _("on startup") + "\n";
strUsage += " -wallet=<file> " + _("Specify wallet file (within data directory)") + " " + strprintf(_("(default: %s)"), "wallet.dat") + "\n";
strUsage += " -walletnotify=<cmd> " + _("Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)") + "\n";
@ -697,6 +698,20 @@ bool AppInit2(boost::thread_group& threadGroup)
mapArgs["-paytxfee"], ::minRelayTxFee.ToString()));
}
}
if (mapArgs.count("-maxtxfee"))
{
CAmount nMaxFee = 0;
if (!ParseMoney(mapArgs["-maxtxfee"], nMaxFee))
return InitError(strprintf(_("Invalid amount for -maxtxfee=<amount>: '%s'"), mapArgs["-maptxfee"]));
if (nMaxFee > nHighTransactionMaxFeeWarning)
InitWarning(_("Warning: -maxtxfee is set very high! Fees this large could be paid on a single transaction."));
maxTxFee = nMaxFee;
if (CFeeRate(maxTxFee, 1000) < ::minRelayTxFee)
{
return InitError(strprintf(_("Invalid amount for -maxtxfee=<amount>: '%s' (must be at least the minrelay fee of %s to prevent stuck transactions)"),
mapArgs["-maxtxfee"], ::minRelayTxFee.ToString()));
}
}
nTxConfirmTarget = GetArg("-txconfirmtarget", 1);
bSpendZeroConfChange = GetArg("-spendzeroconfchange", true);
fSendFreeTransactions = GetArg("-sendfreetransactions", false);

49
src/wallet.cpp
View file

@ -26,6 +26,7 @@ using namespace std;
* Settings
*/
CFeeRate payTxFee(DEFAULT_TRANSACTION_FEE);
CAmount maxTxFee = DEFAULT_TRANSACTION_MAXFEE;
unsigned int nTxConfirmTarget = 1;
bool bSpendZeroConfChange = true;
bool fSendFreeTransactions = false;
@ -1499,28 +1500,33 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, CAmount> >& vecSend,
}
dPriority = wtxNew.ComputePriority(dPriority, nBytes);
// Can we complete this as a free transaction?
if (fSendFreeTransactions && nBytes <= MAX_FREE_TRANSACTION_CREATE_SIZE)
{
// Not enough fee: enough priority?
double dPriorityNeeded = mempool.estimatePriority(nTxConfirmTarget);
// Not enough mempool history to estimate: use hard-coded AllowFree.
if (dPriorityNeeded <= 0 && AllowFree(dPriority))
break;
// Small enough, and priority high enough, to send for free
if (dPriorityNeeded > 0 && dPriority >= dPriorityNeeded)
break;
}
CAmount nFeeNeeded = GetMinimumFee(nBytes, nTxConfirmTarget, mempool);
// If we made it here and we aren't even able to meet the relay fee on the next pass, give up
// because we must be at the maximum allowed fee.
if (nFeeNeeded < ::minRelayTxFee.GetFee(nBytes))
{
strFailReason = _("Transaction too large for fee policy");
return false;
}
if (nFeeRet >= nFeeNeeded)
break; // Done, enough fee included.
// Too big to send for free? Include more fee and try again:
if (!fSendFreeTransactions || nBytes > MAX_FREE_TRANSACTION_CREATE_SIZE)
{
nFeeRet = nFeeNeeded;
continue;
}
// Not enough fee: enough priority?
double dPriorityNeeded = mempool.estimatePriority(nTxConfirmTarget);
// Not enough mempool history to estimate: use hard-coded AllowFree.
if (dPriorityNeeded <= 0 && AllowFree(dPriority))
break;
// Small enough, and priority high enough, to send for free
if (dPriorityNeeded > 0 && dPriority >= dPriorityNeeded)
break;
// Include more fee and try again.
nFeeRet = nFeeNeeded;
continue;
@ -1591,9 +1597,6 @@ CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarge
{
// payTxFee is user-set "I want to pay this much"
CAmount nFeeNeeded = payTxFee.GetFee(nTxBytes);
// prevent user from paying a non-sense fee (like 1 satoshi): 0 < fee < minRelayFee
if (nFeeNeeded > 0 && nFeeNeeded < ::minRelayTxFee.GetFee(nTxBytes))
nFeeNeeded = ::minRelayTxFee.GetFee(nTxBytes);
// user selected total at least (default=true)
if (fPayAtLeastCustomFee && nFeeNeeded > 0 && nFeeNeeded < payTxFee.GetFeePerK())
nFeeNeeded = payTxFee.GetFeePerK();
@ -1604,6 +1607,12 @@ CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarge
// back to a hard-coded fee
if (nFeeNeeded == 0)
nFeeNeeded = minTxFee.GetFee(nTxBytes);
// prevent user from paying a non-sense fee (like 1 satoshi): 0 < fee < minRelayFee
if (nFeeNeeded < ::minRelayTxFee.GetFee(nTxBytes))
nFeeNeeded = ::minRelayTxFee.GetFee(nTxBytes);
// But always obey the maximum
if (nFeeNeeded > maxTxFee)
nFeeNeeded = maxTxFee;
return nFeeNeeded;
}

5
src/wallet.h
View file

@ -30,6 +30,7 @@
* Settings
*/
extern CFeeRate payTxFee;
extern CAmount maxTxFee;
extern unsigned int nTxConfirmTarget;
extern bool bSpendZeroConfChange;
extern bool fSendFreeTransactions;
@ -39,6 +40,10 @@ extern bool fPayAtLeastCustomFee;
static const CAmount DEFAULT_TRANSACTION_FEE = 0;
//! -paytxfee will warn if called with a higher fee than this amount (in satoshis) per KB
static const CAmount nHighTransactionFeeWarning = 0.01 * COIN;
//! -maxtxfee default
static const CAmount DEFAULT_TRANSACTION_MAXFEE = 0.1 * COIN;
//! -maxtxfee will warn if called with a higher fee than this amount (in satoshis)
static const CAmount nHighTransactionMaxFeeWarning = 100 * nHighTransactionFeeWarning;
//! Largest (in bytes) free transaction we're willing to create
static const unsigned int MAX_FREE_TRANSACTION_CREATE_SIZE = 1000;