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