diff options
Diffstat (limited to 'src/wallet/wallet.cpp')
| -rw-r--r-- | src/wallet/wallet.cpp | 53 |
1 files changed, 40 insertions, 13 deletions
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp index 53f39cf8e3..5e9701c71c 100644 --- a/src/wallet/wallet.cpp +++ b/src/wallet/wallet.cpp @@ -2600,8 +2600,12 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT scriptChange = GetScriptForDestination(vchPubKey.GetID()); } + CTxOut change_prototype_txout(0, scriptChange); + size_t change_prototype_size = GetSerializeSize(change_prototype_txout, SER_DISK, 0); nFeeRet = 0; + bool pick_new_inputs = true; + CAmount nValueIn = 0; // Start with no fee and loop until there is enough fee while (true) { @@ -2647,15 +2651,18 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT } // Choose coins to use - CAmount nValueIn = 0; - setCoins.clear(); - if (!SelectCoins(vAvailableCoins, nValueToSelect, setCoins, nValueIn, coinControl)) - { - strFailReason = _("Insufficient funds"); - return false; + if (pick_new_inputs) { + nValueIn = 0; + setCoins.clear(); + if (!SelectCoins(vAvailableCoins, nValueToSelect, setCoins, nValueIn, coinControl)) + { + strFailReason = _("Insufficient funds"); + return false; + } } const CAmount nChange = nValueIn - nValueToSelect; + if (nChange > 0) { // Fill a vout to ourself @@ -2739,16 +2746,30 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT } if (nFeeRet >= nFeeNeeded) { - // Reduce fee to only the needed amount if we have change - // output to increase. This prevents potential overpayment - // in fees if the coins selected to meet nFeeNeeded result - // in a transaction that requires less fee than the prior - // iteration. + // Reduce fee to only the needed amount if possible. This + // prevents potential overpayment in fees if the coins + // selected to meet nFeeNeeded result in a transaction that + // requires less fee than the prior iteration. + // TODO: The case where nSubtractFeeFromAmount > 0 remains // to be addressed because it requires returning the fee to // the payees and not the change output. - // TODO: The case where there is no change output remains - // to be addressed so we avoid creating too small an output. + + // If we have no change and a big enough excess fee, then + // try to construct transaction again only without picking + // new inputs. We now know we only need the smaller fee + // (because of reduced tx size) and so we should add a + // change output. Only try this once. + CAmount fee_needed_for_change = GetMinimumFee(change_prototype_size, currentConfirmationTarget, ::mempool, ::feeEstimator, nullptr, false /* ignoreGlobalPayTxFee */, conservative_estimate); + CAmount minimum_value_for_change = GetDustThreshold(change_prototype_txout, ::dustRelayFee); + CAmount max_excess_fee = fee_needed_for_change + minimum_value_for_change; + if (nFeeRet > nFeeNeeded + max_excess_fee && nChangePosInOut == -1 && nSubtractFeeFromAmount == 0 && pick_new_inputs) { + pick_new_inputs = false; + nFeeRet = nFeeNeeded + fee_needed_for_change; + continue; + } + + // If we have change output already, just increase it if (nFeeRet > nFeeNeeded && nChangePosInOut != -1 && nSubtractFeeFromAmount == 0) { CAmount extraFeePaid = nFeeRet - nFeeNeeded; std::vector<CTxOut>::iterator change_position = txNew.vout.begin()+nChangePosInOut; @@ -2757,6 +2778,12 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT } break; // Done, enough fee included. } + else if (!pick_new_inputs) { + // This shouldn't happen, we should have had enough excess + // fee to pay for the new output and still meet nFeeNeeded + strFailReason = _("Transaction fee and change calculation failed"); + return false; + } // Try to reduce change to include necessary fee if (nChangePosInOut != -1 && nSubtractFeeFromAmount == 0) { |