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/fees.h"
   9 #include "wallet/wallet.h"
  10 #include "policy/fees.h"
  11 #include "policy/policy.h"
  12 #include "policy/rbf.h"
  13 #include "validation.h" //for mempool access
  14 #include "txmempool.h"
  15 #include "utilmoneystr.h"
  16 #include "util.h"
  17 #include "net.h"
  18
  19 // Calculate the size of the transaction assuming all signatures are max size
  20 // Use DummySignatureCreator, which inserts 72 byte signatures everywhere.
  21 // TODO: re-use this in CWallet::CreateTransaction (right now
  22 // CreateTransaction uses the constructed dummy-signed tx to do a priority
  23 // calculation, but we should be able to refactor after priority is removed).
  24 // NOTE: this requires that all inputs must be in mapWallet (eg the tx should
  25 // be IsAllFromMe).
  26 int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *pWallet)
  27 {
  28     CMutableTransaction txNew(tx);
  29     std::vector<CInputCoin> vCoins;
  30     // Look up the inputs.  We should have already checked that this transaction
  31     // IsAllFromMe(ISMINE_SPENDABLE), so every input should already be in our
  32     // wallet, with a valid index into the vout array.
  33     for (auto& input : tx.vin) {
  34         const auto mi = pWallet->mapWallet.find(input.prevout.hash);
  35         assert(mi != pWallet->mapWallet.end() && input.prevout.n < mi->second.tx->vout.size());
  36         vCoins.emplace_back(CInputCoin(&(mi->second), input.prevout.n));
  37     }
  38     if (!pWallet->DummySignTx(txNew, vCoins)) {
  39         // This should never happen, because IsAllFromMe(ISMINE_SPENDABLE)
  40         // implies that we can sign for every input.
  41         return -1;
  42     }
  43     return GetVirtualTransactionSize(txNew);
  44 }
  45
  46 bool CFeeBumper::preconditionChecks(const CWallet *pWallet, const CWalletTx& wtx) {
  47     if (pWallet->HasWalletSpend(wtx.GetHash())) {
  48         vErrors.push_back("Transaction has descendants in the wallet");
  49         currentResult = BumpFeeResult::INVALID_PARAMETER;
  50         return false;
  51     }
  52
  53     {
  54         LOCK(mempool.cs);
  55         auto it_mp = mempool.mapTx.find(wtx.GetHash());
  56         if (it_mp != mempool.mapTx.end() && it_mp->GetCountWithDescendants() > 1) {
  57             vErrors.push_back("Transaction has descendants in the mempool");
  58             currentResult = BumpFeeResult::INVALID_PARAMETER;
  59             return false;
  60         }
  61     }
  62
  63     if (wtx.GetDepthInMainChain() != 0) {
  64         vErrors.push_back("Transaction has been mined, or is conflicted with a mined transaction");
  65         currentResult = BumpFeeResult::WALLET_ERROR;
  66         return false;
  67     }
  68     return true;
  69 }
  70
  71 CFeeBumper::CFeeBumper(const CWallet *pWallet, const uint256 txidIn, const CCoinControl& coin_control, CAmount totalFee)
  72     :
  73     txid(std::move(txidIn)),
  74     nOldFee(0),
  75     nNewFee(0)
  76 {
  77     vErrors.clear();
  78     bumpedTxid.SetNull();
  79     AssertLockHeld(pWallet->cs_wallet);
  80     auto it = pWallet->mapWallet.find(txid);
  81     if (it == pWallet->mapWallet.end()) {
  82         vErrors.push_back("Invalid or non-wallet transaction id");
  83         currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
  84         return;
  85     }
  86     const CWalletTx& wtx = it->second;
  87
  88     if (!preconditionChecks(pWallet, wtx)) {
  89         return;
  90     }
  91
  92     if (!SignalsOptInRBF(wtx)) {
  93         vErrors.push_back("Transaction is not BIP 125 replaceable");
  94         currentResult = BumpFeeResult::WALLET_ERROR;
  95         return;
  96     }
  97
  98     if (wtx.mapValue.count("replaced_by_txid")) {
  99         vErrors.push_back(strprintf("Cannot bump transaction %s which was already bumped by transaction %s", txid.ToString(), wtx.mapValue.at("replaced_by_txid")));
 100         currentResult = BumpFeeResult::WALLET_ERROR;
 101         return;
 102     }
 103
 104     // check that original tx consists entirely of our inputs
 105     // 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)
 106     if (!pWallet->IsAllFromMe(wtx, ISMINE_SPENDABLE)) {
 107         vErrors.push_back("Transaction contains inputs that don't belong to this wallet");
 108         currentResult = BumpFeeResult::WALLET_ERROR;
 109         return;
 110     }
 111
 112     // figure out which output was change
 113     // if there was no change output or multiple change outputs, fail
 114     int nOutput = -1;
 115     for (size_t i = 0; i < wtx.tx->vout.size(); ++i) {
 116         if (pWallet->IsChange(wtx.tx->vout[i])) {
 117             if (nOutput != -1) {
 118                 vErrors.push_back("Transaction has multiple change outputs");
 119                 currentResult = BumpFeeResult::WALLET_ERROR;
 120                 return;
 121             }
 122             nOutput = i;
 123         }
 124     }
 125     if (nOutput == -1) {
 126         vErrors.push_back("Transaction does not have a change output");
 127         currentResult = BumpFeeResult::WALLET_ERROR;
 128         return;
 129     }
 130
 131     // Calculate the expected size of the new transaction.
 132     int64_t txSize = GetVirtualTransactionSize(*(wtx.tx));
 133     const int64_t maxNewTxSize = CalculateMaximumSignedTxSize(*wtx.tx, pWallet);
 134     if (maxNewTxSize < 0) {
 135         vErrors.push_back("Transaction contains inputs that cannot be signed");
 136         currentResult = BumpFeeResult::INVALID_ADDRESS_OR_KEY;
 137         return;
 138     }
 139
 140     // calculate the old fee and fee-rate
 141     nOldFee = wtx.GetDebit(ISMINE_SPENDABLE) - wtx.tx->GetValueOut();
 142     CFeeRate nOldFeeRate(nOldFee, txSize);
 143     CFeeRate nNewFeeRate;
 144     // The wallet uses a conservative WALLET_INCREMENTAL_RELAY_FEE value to
 145     // future proof against changes to network wide policy for incremental relay
 146     // fee that our node may not be aware of.
 147     CFeeRate walletIncrementalRelayFee = CFeeRate(WALLET_INCREMENTAL_RELAY_FEE);
 148     if (::incrementalRelayFee > walletIncrementalRelayFee) {
 149         walletIncrementalRelayFee = ::incrementalRelayFee;
 150     }
 151
 152     if (totalFee > 0) {
 153         CAmount minTotalFee = nOldFeeRate.GetFee(maxNewTxSize) + ::incrementalRelayFee.GetFee(maxNewTxSize);
 154         if (totalFee < minTotalFee) {
 155             vErrors.push_back(strprintf("Insufficient totalFee, must be at least %s (oldFee %s + incrementalFee %s)",
 156                                                                 FormatMoney(minTotalFee), FormatMoney(nOldFeeRate.GetFee(maxNewTxSize)), FormatMoney(::incrementalRelayFee.GetFee(maxNewTxSize))));
 157             currentResult = BumpFeeResult::INVALID_PARAMETER;
 158             return;
 159         }
 160         CAmount requiredFee = GetRequiredFee(maxNewTxSize);
 161         if (totalFee < requiredFee) {
 162             vErrors.push_back(strprintf("Insufficient totalFee (cannot be less than required fee %s)",
 163                                                                 FormatMoney(requiredFee)));
 164             currentResult = BumpFeeResult::INVALID_PARAMETER;
 165             return;
 166         }
 167         nNewFee = totalFee;
 168         nNewFeeRate = CFeeRate(totalFee, maxNewTxSize);
 169     } else {
 170         nNewFee = GetMinimumFee(maxNewTxSize, coin_control, mempool, ::feeEstimator, nullptr /* FeeCalculation */);
 171         nNewFeeRate = CFeeRate(nNewFee, maxNewTxSize);
 172
 173         // New fee rate must be at least old rate + minimum incremental relay rate
 174         // walletIncrementalRelayFee.GetFeePerK() should be exact, because it's initialized
 175         // in that unit (fee per kb).
 176         // However, nOldFeeRate is a calculated value from the tx fee/size, so
 177         // add 1 satoshi to the result, because it may have been rounded down.
 178         if (nNewFeeRate.GetFeePerK() < nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK()) {
 179             nNewFeeRate = CFeeRate(nOldFeeRate.GetFeePerK() + 1 + walletIncrementalRelayFee.GetFeePerK());
 180             nNewFee = nNewFeeRate.GetFee(maxNewTxSize);
 181         }
 182     }
 183
 184     // Check that in all cases the new fee doesn't violate maxTxFee
 185      if (nNewFee > maxTxFee) {
 186          vErrors.push_back(strprintf("Specified or calculated fee %s is too high (cannot be higher than maxTxFee %s)",
 187                                FormatMoney(nNewFee), FormatMoney(maxTxFee)));
 188          currentResult = BumpFeeResult::WALLET_ERROR;
 189          return;
 190      }
 191
 192     // check that fee rate is higher than mempool's minimum fee
 193     // (no point in bumping fee if we know that the new tx won't be accepted to the mempool)
 194     // This may occur if the user set TotalFee or paytxfee too low, if fallbackfee is too low, or, perhaps,
 195     // in a rare situation where the mempool minimum fee increased significantly since the fee estimation just a
 196     // moment earlier. In this case, we report an error to the user, who may use totalFee to make an adjustment.
 197     CFeeRate minMempoolFeeRate = mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
 198     if (nNewFeeRate.GetFeePerK() < minMempoolFeeRate.GetFeePerK()) {
 199         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())));
 200         currentResult = BumpFeeResult::WALLET_ERROR;
 201         return;
 202     }
 203
 204     // Now modify the output to increase the fee.
 205     // If the output is not large enough to pay the fee, fail.
 206     CAmount nDelta = nNewFee - nOldFee;
 207     assert(nDelta > 0);
 208     mtx =  *wtx.tx;
 209     CTxOut* poutput = &(mtx.vout[nOutput]);
 210     if (poutput->nValue < nDelta) {
 211         vErrors.push_back("Change output is too small to bump the fee");
 212         currentResult = BumpFeeResult::WALLET_ERROR;
 213         return;
 214     }
 215
 216     // If the output would become dust, discard it (converting the dust to fee)
 217     poutput->nValue -= nDelta;
 218     if (poutput->nValue <= GetDustThreshold(*poutput, ::dustRelayFee)) {
 219         LogPrint(BCLog::RPC, "Bumping fee and discarding dust output\n");
 220         nNewFee += poutput->nValue;
 221         mtx.vout.erase(mtx.vout.begin() + nOutput);
 222     }
 223
 224     // Mark new tx not replaceable, if requested.
 225     if (!coin_control.signalRbf) {
 226         for (auto& input : mtx.vin) {
 227             if (input.nSequence < 0xfffffffe) input.nSequence = 0xfffffffe;
 228         }
 229     }
 230
 231     currentResult = BumpFeeResult::OK;
 232 }
 233
 234 bool CFeeBumper::signTransaction(CWallet *pWallet)
 235 {
 236      return pWallet->SignTransaction(mtx);
 237 }
 238
 239 bool CFeeBumper::commit(CWallet *pWallet)
 240 {
 241     AssertLockHeld(pWallet->cs_wallet);
 242     if (!vErrors.empty() || currentResult != BumpFeeResult::OK) {
 243         return false;
 244     }
 245     auto it = txid.IsNull() ? pWallet->mapWallet.end() : pWallet->mapWallet.find(txid);
 246     if (it == pWallet->mapWallet.end()) {
 247         vErrors.push_back("Invalid or non-wallet transaction id");
 248         currentResult = BumpFeeResult::MISC_ERROR;
 249         return false;
 250     }
 251     CWalletTx& oldWtx = it->second;
 252
 253     // make sure the transaction still has no descendants and hasn't been mined in the meantime
 254     if (!preconditionChecks(pWallet, oldWtx)) {
 255         return false;
 256     }
 257
 258     CWalletTx wtxBumped(pWallet, MakeTransactionRef(std::move(mtx)));
 259     // commit/broadcast the tx
 260     CReserveKey reservekey(pWallet);
 261     wtxBumped.mapValue = oldWtx.mapValue;
 262     wtxBumped.mapValue["replaces_txid"] = oldWtx.GetHash().ToString();
 263     wtxBumped.vOrderForm = oldWtx.vOrderForm;
 264     wtxBumped.strFromAccount = oldWtx.strFromAccount;
 265     wtxBumped.fTimeReceivedIsTxTime = true;
 266     wtxBumped.fFromMe = true;
 267     CValidationState state;
 268     if (!pWallet->CommitTransaction(wtxBumped, reservekey, g_connman.get(), state)) {
 269         // NOTE: CommitTransaction never returns false, so this should never happen.
 270         vErrors.push_back(strprintf("Error: The transaction was rejected! Reason given: %s", state.GetRejectReason()));
 271         return false;
 272     }
 273
 274     bumpedTxid = wtxBumped.GetHash();
 275     if (state.IsInvalid()) {
 276         // This can happen if the mempool rejected the transaction.  Report
 277         // what happened in the "errors" response.
 278         vErrors.push_back(strprintf("Error: The transaction was rejected: %s", FormatStateMessage(state)));
 279     }
 280
 281     // mark the original tx as bumped
 282     if (!pWallet->MarkReplaced(oldWtx.GetHash(), wtxBumped.GetHash())) {
 283         // TODO: see if JSON-RPC has a standard way of returning a response
 284         // along with an exception. It would be good to return information about
 285         // wtxBumped to the caller even if marking the original transaction
 286         // replaced does not succeed for some reason.
 287         vErrors.push_back("Error: Created new bumpfee transaction but could not mark the original transaction as replaced.");
 288     }
 289     return true;
 290 }
 291