src/wallet/feebumper.cpp

   1 // Copyright (c) 2017 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include "consensus/validation.h"
   6 #include "wallet/coincontrol.h"
   7 #include "wallet/feebumper.h"
   8 #include "wallet/wallet.h"
   9 #include "policy/fees.h"
  10 #include "policy/policy.h"
  11 #include "policy/rbf.h"
  12 #include "validation.h" //for mempool access
  13 #include "txmempool.h"
  14 #include "utilmoneystr.h"
  15 #include "util.h"
  16 #include "net.h"
  17
  18 // Calculate the size of the transaction assuming all signatures are max size
  19 // Use DummySignatureCreator, which inserts 72 byte signatures everywhere.
  20 // TODO: re-use this in CWallet::CreateTransaction (right now
  21 // CreateTransaction uses the constructed dummy-signed tx to do a priority
  22 // calculation, but we should be able to refactor after priority is removed).
  23 // NOTE: this requires that all inputs must be in mapWallet (eg the tx should
  24 // be IsAllFromMe).
  25 int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *pWallet)
  26 {
  27     CMutableTransaction txNew(tx);
  28     std::vector<CInputCoin> vCoins;
  29     // Look up the inputs.  We should have already checked that this transaction
  30     // IsAllFromMe(ISMINE_SPENDABLE), so every input should already be in our
  31     // wallet, with a valid index into the vout array.
  32     for (auto& input : tx.vin) {
  33         const auto mi = pWallet->mapWallet.find(input.prevout.hash);
  34         assert(mi != pWallet->mapWallet.end() && input.prevout.n < mi->second.tx->vout.size());
  35         vCoins.emplace_back(CInputCoin(&(mi->second), input.prevout.n));
  36     }
  37     if (!pWallet->DummySignTx(txNew, vCoins)) {
  38         // This should never happen, because IsAllFromMe(ISMINE_SPENDABLE)
  39         // implies that we can sign for every input.
  40         return -1;
  41     }
  42     return GetVirtualTransactionSize(txNew);
  43 }
  44
  45 bool CFeeBumper::preconditionChecks(const CWallet *pWallet, const CWalletTx& wtx) {
  46     if (pWallet->HasWalletSpend(wtx.GetHash())) {
  47         vErrors.push_back("Transaction has descendants in the wallet");
  48         currentResult = BumpFeeResult::INVALID_PARAMETER;
  49         return false;
  50     }
  51
  52     {
  53         LOCK(mempool.cs);
  54         auto it_mp = mempool.mapTx.find(wtx.GetHash());
  55         if (it_mp != mempool.mapTx.end() && it_mp->GetCountWithDescendants() > 1) {
  56             vErrors.push_back("Transaction has descendants in the mempool");
  57             currentResult = BumpFeeResult::INVALID_PARAMETER;
  58             return false;
  59         }
  60     }
  61
  62     if (wtx.GetDepthInMainChain() != 0) {
  63         vErrors.push_back("Transaction has been mined, or is conflicted with a mined transaction");
  64         currentResult = BumpFeeResult::WALLET_ERROR;
  65         return false;
  66     }
  67     return true;
  68 }
  69
  70 CFeeBumper::CFeeBumper(const CWallet *pWallet, const uint256 txidIn, const CCoinControl& coin_control, CAmount totalFee)
  71     :
  72     txid(std::move(txidIn)),
  73     nOldFee(0),
  74     nNewFee(0)
  75 {
  76     vErrors.clear();
  77     bumpedTxid.SetNull();
  78     AssertLockHeld(pWallet->cs_wallet);
  79     if (!pWallet->mapWallet.count(txid)) {
  80         vErrors.push_back("Invalid or non-wallet transaction id");
  81         currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
  82         return;
  83     }
  84     auto it = pWallet->mapWallet.find(txid);
  85     const CWalletTx& wtx = it->second;
  86
  87     if (!preconditionChecks(pWallet, wtx)) {
  88         return;
  89     }
  90
  91     if (!SignalsOptInRBF(wtx)) {
  92         vErrors.push_back("Transaction is not BIP 125 replaceable");
  93         currentResult = BumpFeeResult::WALLET_ERROR;
  94         return;
  95     }
  96
  97     if (wtx.mapValue.count("replaced_by_txid")) {
  98         vErrors.push_back(strprintf("Cannot bump transaction %s which was already bumped by transaction %s", txid.ToString(), wtx.mapValue.at("replaced_by_txid")));
  99         currentResult = BumpFeeResult::WALLET_ERROR;
 100         return;
 101     }
 102
 103     // check that original tx consists entirely of our inputs
 104     // 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)
 105     if (!pWallet->IsAllFromMe(wtx, ISMINE_SPENDABLE)) {
 106         vErrors.push_back("Transaction contains inputs that don't belong to this wallet");
 107         currentResult = BumpFeeResult::WALLET_ERROR;
 108         return;
 109     }
 110
 111     // figure out which output was change
 112     // if there was no change output or multiple change outputs, fail
 113     int nOutput = -1;
 114     for (size_t i = 0; i < wtx.tx->vout.size(); ++i) {
 115         if (pWallet->IsChange(wtx.tx->vout[i])) {
 116             if (nOutput != -1) {
 117                 vErrors.push_back("Transaction has multiple change outputs");
 118                 currentResult = BumpFeeResult::WALLET_ERROR;
 119                 return;
 120             }
 121             nOutput = i;
 122         }
 123     }
 124     if (nOutput == -1) {
 125         vErrors.push_back("Transaction does not have a change output");
 126         currentResult = BumpFeeResult::WALLET_ERROR;
 127         return;
 128     }
 129
 130     // Calculate the expected size of the new transaction.
 131     int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
 132     const int64_t maxNewTxSize = CalculateMaximumSignedTxSize(*wtx.tx, pWallet);
 133     if (maxNewTxSize < 0) {
 134         vErrors.push_back("Transaction contains inputs that cannot be signed");
 135         currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
 136         return;
 137     }
 138
 139     // calculate the old fee and fee-rate
 140     nOldFee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
 141     CFeeRate nOldFeeRate(nOldFee, txSize);
 142     CFeeRate nNewFeeRate;
 143     // The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
 144     // future proof against changes to network wide policy for incremental relay
 145     // fee that our node may not be aware of.
 146     CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
 147     if (::incrementalRelayFee > walletIncrementalRelayFee) {
 148         walletIncrementalRelayFee = ::incrementalRelayFee;
 149     }
 150
 151     if (totalFee > 0) {
 152         CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + ::incrementalRelayFee.GetFee(maxNewTxSize);
 153         if (totalFee < minTotalFee) {
 154             vErrors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
 155                                                                 FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(::incrementalRelayFee.GetFee(maxNewTxSize))));
 156             currentResult = BumpFeeResult::INVALID_PARAMETER;
 157             return;
 158         }
 159         CAmount requiredFee = CWallet::GetRequiredFee(maxNewTxSize);
 160         if (totalFee < requiredFee) {
 161             vErrors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
 162                                                                 FormatMoney(requiredFee)));
 163             currentResult = BumpFeeResult::INVALID_PARAMETER;
 164             return;
 165         }
 166         nNewFee = totalFee;
 167         nNewFeeRate = CFeeRate(totalFee, maxNewTxSize);
 168     } else {
 169         nNewFee = CWallet::GetMinimumFee(maxNewTxSize, coin_control, mempool, ::feeEstimator, nullptr /* FeeCalculation */);
 170         nNewFeeRate = CFeeRate(nNewFee, maxNewTxSize);
 171
 172         // New fee rate must be at least old rate + minimum incremental relay rate
 173         // walletIncrementalRelayFee.GetFeePerK() should be exact, because it's initialized
 174         // in that unit (fee per kb).
 175         // However, nOldFeeRate is a calculated value from the tx fee/size, so
 176         // add 1 satoshi to the result, because it may have been rounded down.
 177         if (nNewFeeRate.GetFeePerK() < nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK()) {
 178             nNewFeeRate = CFeeRate(nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK());
 179             nNewFee = nNewFeeRate.GetFee(maxNewTxSize);
 180         }
 181     }
 182
 183     // Check that in all cases the new fee doesn't violate maxTxFee
 184      if (nNewFee > maxTxFee) {
 185          vErrors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
 186                                FormatMoney(nNewFee), FormatMoney(maxTxFee)));
 187          currentResult = BumpFeeResult::WALLET_ERROR;
 188          return;
 189      }
 190
 191     // check that fee rate is higher than mempool's minimum fee
 192     // (no point in bumping fee if we know that the new tx won't be accepted to the mempool)
 193     // This may occur if the user set TotalFee or paytxfee too low, if fallbackfee is too low, or, perhaps,
 194     // in a rare situation where the mempool minimum fee increased significantly since the fee estimation just a
 195     // moment earlier. In this case, we report an error to the user, who may use totalFee to make an adjustment.
 196     CFeeRate minMempoolFeeRate = mempool.GetMinFee(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
 197     if (nNewFeeRate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
 198         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())));
 199         currentResult = BumpFeeResult::WALLET_ERROR;
 200         return;
 201     }
 202
 203     // Now modify the output to increase the fee.
 204     // If the output is not large enough to pay the fee, fail.
 205     CAmount nDelta = nNewFee - nOldFee;
 206     assert(nDelta > 0);
 207     mtx =  *wtx.tx;
 208     CTxOut* poutput = &(mtx.vout[nOutput]);
 209     if (poutput->nValue < nDelta) {
 210         vErrors.push_back("Change output is too small to bump the fee");
 211         currentResult = BumpFeeResult::WALLET_ERROR;
 212         return;
 213     }
 214
 215     // If the output would become dust, discard it (converting the dust to fee)
 216     poutput->nValue -= nDelta;
 217     if (poutput->nValue <= GetDustThreshold(*poutput, ::dustRelayFee)) {
 218         LogPrint(BCLog::RPC, "Bumping fee and discarding dust output\n");
 219         nNewFee += poutput->nValue;
 220         mtx.vout.erase(mtx.vout.begin() + nOutput);
 221     }
 222
 223     // Mark new tx not replaceable, if requested.
 224     if (!coin_control.signalRbf) {
 225         for (auto& input : mtx.vin) {
 226             if (input.nSequence < 0xfffffffe) input.nSequence = 0xfffffffe;
 227         }
 228     }
 229
 230     currentResult = BumpFeeResult::OK;
 231 }
 232
 233 bool CFeeBumper::signTransaction(CWallet *pWallet)
 234 {
 235      return pWallet->SignTransaction(mtx);
 236 }
 237
 238 bool CFeeBumper::commit(CWallet *pWallet)
 239 {
 240     AssertLockHeld(pWallet->cs_wallet);
 241     if (!vErrors.empty() || currentResult != BumpFeeResult::OK) {
 242         return false;
 243     }
 244     if (txid.IsNull() || !pWallet->mapWallet.count(txid)) {
 245         vErrors.push_back("Invalid or non-wallet transaction id");
 246         currentResult = BumpFeeResult::MISC_ERROR;
 247         return false;
 248     }
 249     CWalletTx& oldWtx = pWallet->mapWallet[txid];
 250
 251     // make sure the transaction still has no descendants and hasn't been mined in the meantime
 252     if (!preconditionChecks(pWallet, oldWtx)) {
 253         return false;
 254     }
 255
 256     CWalletTx wtxBumped(pWallet, MakeTransactionRef(std::move(mtx)));
 257     // commit/broadcast the tx
 258     CReserveKey reservekey(pWallet);
 259     wtxBumped.mapValue = oldWtx.mapValue;
 260     wtxBumped.mapValue["replaces_txid"] = oldWtx.GetHash().ToString();
 261     wtxBumped.vOrderForm = oldWtx.vOrderForm;
 262     wtxBumped.strFromAccount = oldWtx.strFromAccount;
 263     wtxBumped.fTimeReceivedIsTxTime = true;
 264     wtxBumped.fFromMe = true;
 265     CValidationState state;
 266     if (!pWallet->CommitTransaction(wtxBumped, reservekey, g_connman.get(), state)) {
 267         // NOTE: CommitTransaction never returns false, so this should never happen.
 268         vErrors.push_back(strprintf("Error: The transaction was rejected! Reason given: %s", state.GetRejectReason()));
 269         return false;
 270     }
 271
 272     bumpedTxid = wtxBumped.GetHash();
 273     if (state.IsInvalid()) {
 274         // This can happen if the mempool rejected the transaction.  Report
 275         // what happened in the "errors" response.
 276         vErrors.push_back(strprintf("Error: The transaction was rejected: %s", FormatStateMessage(state)));
 277     }
 278
 279     // mark the original tx as bumped
 280     if (!pWallet->MarkReplaced(oldWtx.GetHash(), wtxBumped.GetHash())) {
 281         // TODO: see if JSON-RPC has a standard way of returning a response
 282         // along with an exception. It would be good to return information about
 283         // wtxBumped to the caller even if marking the original transaction
 284         // replaced does not succeed for some reason.
 285         vErrors.push_back("Error: Created new bumpfee transaction but could not mark the original transaction as replaced.");
 286     }
 287     return true;
 288 }
 289