Merge pull request #3883 from dgenr8/first_double_spend

Relay and alert user to double spends

contrib/debian/manpages/bitcoin-qt.1

@@ -139,6 +139,9 @@ Execute command when the best block changes (%s in cmd is replaced by block hash
 \fB\-walletnotify=\fR<cmd>
 Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)
 .TP
+\fB\-respendnotify=\fR<cmd>
+Execute command when a network tx respends wallet tx input (%s=respend TxID, %t=wallet TxID)
+.TP
 \fB\-alertnotify=\fR<cmd>
 Execute command when a relevant alert is received (%s in cmd is replaced by message)
 .TP

doc/release-notes.md

@@ -19,3 +19,49 @@ estimate.
 Statistics used to estimate fees and priorities are saved in the
 data directory in the 'fee_estimates.dat' file just before
 program shutdown, and are read in at startup.
+
+Double-Spend Relay and Alerts
+=============================
+VERY IMPORTANT: *It has never been safe, and remains unsafe, to rely*
+*on unconfirmed transactions.*
+
+Relay
+-----
+When an attempt is seen on the network to spend the same unspent funds
+more than once, it is no longer ignored.  Instead, it is broadcast, to
+serve as an alert.  This broadcast is subject to protections against
+denial-of-service attacks.
+
+Wallets and other bitcoin services should alert their users to
+double-spends that affect them.  Merchants and other users may have
+enough time to withhold goods or services when payment becomes
+uncertain, until confirmation.
+
+Bitcoin Core Wallet Alerts
+--------------------------
+The Bitcoin Core wallet now makes respend attempts visible in several
+ways.
+
+If you are online, and a respend affecting one of your wallet
+transactions is seen, a notification is immediately issued to the
+command registered with `-respendnotify=<cmd>`.  Additionally, if
+using the GUI:
+ - An alert box is immediately displayed.
+ - The affected wallet transaction is highlighted in red until it is
+   confirmed (and it may never be confirmed).
+
+A `respendsobserved` array is added to `gettransaction`, `listtransactions`,
+and `listsinceblock` RPC results.
+
+Warning
+-------
+*If you rely on an unconfirmed transaction, these change do VERY*
+*LITTLE to protect you from a malicious double-spend, because:*
+
+ - You may learn about the respend too late to avoid doing whatever
+   you were being paid for
+ - Using other relay rules, a double-spender can craft his crime to
+   resist broadcast
+ - Miners can choose which conflicting spend to confirm, and some
+   miners may not confirm the first acceptable spend they see
+

src/bloom.cpp

@@ -94,6 +94,13 @@ bool CBloomFilter::contains(const uint256& hash) const
     return contains(data);
 }
 
+void CBloomFilter::clear()
+{
+    vData.assign(vData.size(),0);
+    isFull = false;
+    isEmpty = true;
+}
+
 bool CBloomFilter::IsWithinSizeConstraints() const
 {
     return vData.size() <= MAX_BLOOM_FILTER_SIZE && nHashFuncs <= MAX_HASH_FUNCS;

src/bloom.h

@@ -78,6 +78,8 @@ public:
     bool contains(const COutPoint& outpoint) const;
     bool contains(const uint256& hash) const;
 
+    void clear();
+
     // True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
     // (catch a filter which was just deserialized which was too big)
     bool IsWithinSizeConstraints() const;

src/core.cpp

@@ -119,6 +119,22 @@ CTransaction& CTransaction::operator=(const CTransaction &tx) {
     return *this;
 }
 
+bool CTransaction::IsEquivalentTo(const CTransaction& tx) const
+{
+    if (nVersion   != tx.nVersion   ||
+        nLockTime  != tx.nLockTime  ||
+        vin.size() != tx.vin.size() ||
+        vout       != tx.vout)
+        return false;
+    for (unsigned int i = 0; i < vin.size(); i++)
+    {
+        if (vin[i].nSequence != tx.vin[i].nSequence ||
+            vin[i].prevout   != tx.vin[i].prevout)
+            return false;
+    }
+    return true;
+}
+
 int64_t CTransaction::GetValueOut() const
 {
     int64_t nValueOut = 0;

src/core.h

@@ -256,6 +256,9 @@ public:
         return hash;
     }
 
+    // True if only scriptSigs are different
+    bool IsEquivalentTo(const CTransaction& tx) const;
+
     // Return sum of txouts.
     int64_t GetValueOut() const;
     // GetValueIn() is a method on CCoinsViewCache, because

src/init.cpp

@@ -260,6 +260,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += "  -upgradewallet         " + _("Upgrade wallet to latest format") + " " + _("on startup") + "\n";
     strUsage += "  -wallet=<file>         " + _("Specify wallet file (within data directory)") + " " + _("(default: wallet.dat)") + "\n";
     strUsage += "  -walletnotify=<cmd>    " + _("Execute command when a wallet transaction changes (%s in cmd is replaced by TxID)") + "\n";
+    strUsage += "  -respendnotify=<cmd>   " + _("Execute command when a network tx respends wallet tx input (%s=respend TxID, %t=wallet TxID)") + "\n";
     strUsage += "  -zapwallettxes=<mode>  " + _("Delete all wallet transactions and only recover those part of the blockchain through -rescan on startup") + "\n";
     strUsage += "                         " + _("(default: 1, 1 = keep tx meta data e.g. account owner and payment request information, 2 = drop tx meta data)") + "\n";
 #endif
@@ -1175,6 +1176,7 @@ bool AppInit2(boost::thread_group& threadGroup)
     LogPrintf("mapAddressBook.size() = %u\n",  pwalletMain ? pwalletMain->mapAddressBook.size() : 0);
 #endif
 
+    RegisterInternalSignals();
     StartNode(threadGroup);
     if (fServer)
         StartRPCThreads();

src/main.cpp

@@ -7,6 +7,7 @@
 
 #include "addrman.h"
 #include "alert.h"
+#include "bloom.h"
 #include "chainparams.h"
 #include "checkpoints.h"
 #include "checkqueue.h"
@@ -124,6 +125,10 @@ namespace {
 
 } // anon namespace
 
+// Forward reference functions defined here:
+static const unsigned int MAX_DOUBLESPEND_BLOOM = 1000;
+static void RelayDoubleSpend(const COutPoint& outPoint, const CTransaction& doubleSpend, bool fInBlock, CBloomFilter& filter);
+
 //////////////////////////////////////////////////////////////////////////////
 //
 // dispatching functions
@@ -146,10 +151,25 @@ struct CMainSignals {
     boost::signals2::signal<void (const uint256 &)> Inventory;
     // Tells listeners to broadcast their data.
     boost::signals2::signal<void ()> Broadcast;
+    // Notifies listeners of detection of a double-spent transaction. Arguments are outpoint that is
+    // double-spent, first transaction seen, double-spend transaction, and whether the second double-spend
+    // transaction was first seen in a block.
+    // Note: only notifies if the previous transaction is in the memory pool; if previous transction was in a block,
+    // then the double-spend simply fails when we try to lookup the inputs in the current UTXO set.
+    boost::signals2::signal<void (const COutPoint&, const CTransaction&, bool)> DetectedDoubleSpend;
 } g_signals;
 
 } // anon namespace
 
+void RegisterInternalSignals() {
+    static CBloomFilter doubleSpendFilter;
+    seed_insecure_rand();
+    doubleSpendFilter = CBloomFilter(MAX_DOUBLESPEND_BLOOM, 0.01, insecure_rand(), BLOOM_UPDATE_NONE);
+
+    g_signals.DetectedDoubleSpend.connect(boost::bind(RelayDoubleSpend, _1, _2, _3, doubleSpendFilter));
+}
+
+
 void RegisterWallet(CWalletInterface* pwalletIn) {
     g_signals.SyncTransaction.connect(boost::bind(&CWalletInterface::SyncTransaction, pwalletIn, _1, _2));
     g_signals.EraseTransaction.connect(boost::bind(&CWalletInterface::EraseFromWallet, pwalletIn, _1));
@@ -872,6 +892,21 @@ int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree,
     return nMinFee;
 }
 
+// Exponentially limit the rate of nSize flow to nLimit.  nLimit unit is thousands-per-minute.
+bool RateLimitExceeded(double& dCount, int64_t& nLastTime, int64_t nLimit, unsigned int nSize)
+{
+    static CCriticalSection csLimiter;
+    int64_t nNow = GetTime();
+
+    LOCK(csLimiter);
+
+    dCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime));
+    nLastTime = nNow;
+    if (dCount >= nLimit*10*1000)
+        return true;
+    dCount += nSize;
+    return false;
+}
 
 bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                         bool* pfMissingInputs, bool fRejectInsaneFee)
@@ -906,9 +941,10 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     for (unsigned int i = 0; i < tx.vin.size(); i++)
     {
         COutPoint outpoint = tx.vin[i].prevout;
-        if (pool.mapNextTx.count(outpoint))
+        // Does tx conflict with a member of the pool, and is it not equivalent to that member?
+        if (pool.mapNextTx.count(outpoint) && !tx.IsEquivalentTo(*pool.mapNextTx[outpoint].ptx))
         {
-            // Disable replacement feature for now
+            g_signals.DetectedDoubleSpend(outpoint, tx, false);
             return false;
         }
     }
@@ -980,23 +1016,15 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
         // be annoying or make others' transactions take longer to confirm.
         if (fLimitFree && nFees < CTransaction::minRelayTxFee.GetFee(nSize))
         {
-            static CCriticalSection csFreeLimiter;
             static double dFreeCount;
-            static int64_t nLastTime;
-            int64_t nNow = GetTime();
+            static int64_t nLastFreeTime;
+            static int64_t nFreeLimit = GetArg("-limitfreerelay", 15);
 
-            LOCK(csFreeLimiter);
-
-            // Use an exponentially decaying ~10-minute window:
-            dFreeCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime));
-            nLastTime = nNow;
-            // -limitfreerelay unit is thousand-bytes-per-minute
-            // At default rate it would take over a month to fill 1GB
-            if (dFreeCount >= GetArg("-limitfreerelay", 15)*10*1000)
+            if (RateLimitExceeded(dFreeCount, nLastFreeTime, nFreeLimit, nSize))
                 return state.DoS(0, error("AcceptToMemoryPool : free transaction rejected by rate limiter"),
                                  REJECT_INSUFFICIENTFEE, "insufficient priority");
+
             LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
-            dFreeCount += nSize;
         }
 
         if (fRejectInsaneFee && nFees > CTransaction::minRelayTxFee.GetFee(nSize) * 10000)
@@ -1019,6 +1047,48 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     return true;
 }
 
+static void RelayDoubleSpend(const COutPoint& outPoint, const CTransaction& doubleSpend, bool fInBlock, CBloomFilter& filter)
+{
+    // Relaying double-spend attempts to our peers lets them detect when
+    // somebody might be trying to cheat them. However, blindly relaying
+    // every double-spend across the entire network gives attackers
+    // a denial-of-service attack: just generate a stream of double-spends
+    // re-spending the same (limited) set of outpoints owned by the attacker.
+    // So, we use a bloom filter and only relay (at most) the first double
+    // spend for each outpoint. False-positives ("we have already relayed")
+    // are OK, because if the peer doesn't hear about the double-spend
+    // from us they are very likely to hear about it from another peer, since
+    // each peer uses a different, randomized bloom filter.
+
+    if (fInBlock || filter.contains(outPoint)) return;
+
+    // Apply an independent rate limit to double-spend relays
+    static double dRespendCount;
+    static int64_t nLastRespendTime;
+    static int64_t nRespendLimit = GetArg("-limitrespendrelay", 100);
+    unsigned int nSize = ::GetSerializeSize(doubleSpend, SER_NETWORK, PROTOCOL_VERSION);
+
+    if (RateLimitExceeded(dRespendCount, nLastRespendTime, nRespendLimit, nSize))
+    {
+        LogPrint("mempool", "Double-spend relay rejected by rate limiter\n");
+        return;
+    }
+
+    LogPrint("mempool", "Rate limit dRespendCount: %g => %g\n", dRespendCount, dRespendCount+nSize);
+
+    // Clear the filter on average every MAX_DOUBLE_SPEND_BLOOM
+    // insertions
+    if (insecure_rand()%MAX_DOUBLESPEND_BLOOM == 0)
+        filter.clear();
+
+    filter.insert(outPoint);
+
+    RelayTransaction(doubleSpend);
+
+    // Share conflict with wallet
+    g_signals.SyncTransaction(doubleSpend, NULL);
+}
+
 
 int CMerkleTx::GetDepthInMainChainINTERNAL(CBlockIndex* &pindexRet) const
 {

src/main.h

@@ -108,6 +108,9 @@ struct CNodeStateStats;
 
 struct CBlockTemplate;
 
+/** Set up internal signal handlers **/
+void RegisterInternalSignals();
+
 /** Register a wallet to receive updates from core */
 void RegisterWallet(CWalletInterface* pwalletIn);
 /** Unregister a wallet from core */

src/qt/guiconstants.h

@@ -23,6 +23,10 @@ static const int STATUSBAR_ICONSIZE = 16;
 #define COLOR_NEGATIVE QColor(255, 0, 0)
 /* Transaction list -- bare address (without label) */
 #define COLOR_BAREADDRESS QColor(140, 140, 140)
+/* Transaction list -- has conflicting transactions */
+#define COLOR_HASCONFLICTING Qt::white;
+/* Transaction list -- has conflicting transactions - background */
+#define COLOR_HASCONFLICTING_BG QColor(192, 0, 0)
 
 /* Tooltips longer than this (in characters) are converted into rich text,
    so that they can be word-wrapped.

src/qt/transactionfilterproxy.cpp

@@ -24,7 +24,7 @@ TransactionFilterProxy::TransactionFilterProxy(QObject *parent) :
     typeFilter(ALL_TYPES),
     minAmount(0),
     limitRows(-1),
-    showInactive(true)
+    showInactive(false)
 {
 }
 
@@ -39,7 +39,7 @@ bool TransactionFilterProxy::filterAcceptsRow(int sourceRow, const QModelIndex &
     qint64 amount = llabs(index.data(TransactionTableModel::AmountRole).toLongLong());
     int status = index.data(TransactionTableModel::StatusRole).toInt();
 
-    if(!showInactive && status == TransactionStatus::Conflicted)
+    if(!showInactive && status == TransactionStatus::Conflicted && type == TransactionRecord::Other)
         return false;
     if(!(TYPE(type) & typeFilter))
         return false;

src/qt/transactionrecord.cpp

@@ -170,6 +170,8 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
     status.depth = wtx.GetDepthInMainChain();
     status.cur_num_blocks = chainActive.Height();
 
+    status.hasConflicting = false;
+
     if (!IsFinalTx(wtx, chainActive.Height() + 1))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
@@ -213,6 +215,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
         if (status.depth < 0)
         {
             status.status = TransactionStatus::Conflicted;
+            status.hasConflicting = !(wtx.GetConflicts(false).empty());
         }
         else if (GetAdjustedTime() - wtx.nTimeReceived > 2 * 60 && wtx.GetRequestCount() == 0)
         {
@@ -221,6 +224,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
         else if (status.depth == 0)
         {
             status.status = TransactionStatus::Unconfirmed;
+            status.hasConflicting = !(wtx.GetConflicts(false).empty());
         }
         else if (status.depth < RecommendedNumConfirmations)
         {
@@ -231,13 +235,13 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
             status.status = TransactionStatus::Confirmed;
         }
     }
-
 }
 
-bool TransactionRecord::statusUpdateNeeded()
+bool TransactionRecord::statusUpdateNeeded(int64_t nConflictsReceived)
 {
     AssertLockHeld(cs_main);
-    return status.cur_num_blocks != chainActive.Height();
+    return (status.cur_num_blocks != chainActive.Height() ||
+            status.cur_num_conflicts != nConflictsReceived);
 }
 
 QString TransactionRecord::getTxID() const

src/qt/transactionrecord.h

@@ -19,9 +19,17 @@ class TransactionStatus
 {
 public:
     TransactionStatus():
-        countsForBalance(false), sortKey(""),
-        matures_in(0), status(Offline), depth(0), open_for(0), cur_num_blocks(-1)
-    { }
+        countsForBalance(false),
+        sortKey(""),
+        matures_in(0),
+        status(Offline),
+        hasConflicting(false),
+        depth(0),
+        open_for(0),
+        cur_num_blocks(-1),
+        cur_num_conflicts(-1)
+    {
+    }
 
     enum Status {
         Confirmed,          /**< Have 6 or more confirmations (normal tx) or fully mature (mined tx) **/
@@ -51,6 +59,10 @@ public:
     /** @name Reported status
        @{*/
     Status status;
+
+    // Has conflicting transactions spending same prevout
+    bool hasConflicting;
+
     qint64 depth;
     qint64 open_for; /**< Timestamp if status==OpenUntilDate, otherwise number
                       of additional blocks that need to be mined before
@@ -59,6 +71,10 @@ public:
 
     /** Current number of blocks (to know whether cached status is still valid) */
     int cur_num_blocks;
+
+    /** Number of conflicts received into wallet as of last status update */
+    int64_t cur_num_conflicts;
+
 };
 
 /** UI model for a transaction. A core transaction can be represented by multiple UI transactions if it has
@@ -133,7 +149,7 @@ public:
 
     /** Return whether a status update is needed.
      */
-    bool statusUpdateNeeded();
+    bool statusUpdateNeeded(int64_t nConflictsReceived);
 };
 
 #endif // TRANSACTIONRECORD_H

src/qt/transactiontablemodel.cpp

@@ -168,8 +168,7 @@ public:
                 parent->endRemoveRows();
                 break;
             case CT_UPDATED:
-                // Miscellaneous updates -- nothing to do, status update will take care of this, and is only computed for
-                // visible transactions.
+                emit parent->dataChanged(parent->index(lowerIndex, parent->Status), parent->index(upperIndex-1, parent->Amount));
                 break;
             }
         }
@@ -190,20 +189,21 @@ public:
             // stuck if the core is holding the locks for a longer time - for
             // example, during a wallet rescan.
             //
-            // If a status update is needed (blocks came in since last check),
+            // If a status update is needed (blocks or conflicts came in since last check),
             // update the status of this transaction from the wallet. Otherwise,
             // simply re-use the cached status.
             TRY_LOCK(cs_main, lockMain);
             if(lockMain)
             {
                 TRY_LOCK(wallet->cs_wallet, lockWallet);
-                if(lockWallet && rec->statusUpdateNeeded())
+                if(lockWallet && rec->statusUpdateNeeded(wallet->nConflictsReceived))
                 {
                     std::map<uint256, CWalletTx>::iterator mi = wallet->mapWallet.find(rec->hash);
 
                     if(mi != wallet->mapWallet.end())
                     {
                         rec->updateStatus(mi->second);
+                        rec->status.cur_num_conflicts = wallet->nConflictsReceived;
                     }
                 }
             }
@@ -363,6 +363,8 @@ QString TransactionTableModel::formatTxType(const TransactionRecord *wtx) const
         return tr("Payment to yourself");
     case TransactionRecord::Generated:
         return tr("Mined");
+    case TransactionRecord::Other:
+        return tr("Other");
     default:
         return QString();
     }
@@ -535,7 +537,13 @@ QVariant TransactionTableModel::data(const QModelIndex &index, int role) const
         return formatTooltip(rec);
     case Qt::TextAlignmentRole:
         return column_alignments[index.column()];
+    case Qt::BackgroundColorRole:
+        if (rec->status.hasConflicting)
+            return COLOR_HASCONFLICTING_BG;
+        break;
     case Qt::ForegroundRole:
+        if (rec->status.hasConflicting)
+            return COLOR_HASCONFLICTING;
         // Non-confirmed (but not immature) as transactions are grey
         if(!rec->status.countsForBalance && rec->status.status != TransactionStatus::Immature)
         {

src/qt/walletmodel.cpp

@@ -138,6 +138,14 @@ void WalletModel::checkBalanceChanged()
 
 void WalletModel::updateTransaction(const QString &hash, int status)
 {
+    if (status == CT_GOT_CONFLICT)
+    {
+        emit message(tr("Conflict Received"),
+                     tr("WARNING: Transaction may never be confirmed. Its input was seen being spent by another transaction on the network. Wait for confirmation!"),
+                     CClientUIInterface::MSG_WARNING);
+        return;
+    }
+
     if(transactionTableModel)
         transactionTableModel->updateTransaction(hash, status);
 

src/rpcwallet.cpp

@@ -58,6 +58,10 @@ void WalletTxToJSON(const CWalletTx& wtx, Object& entry)
     BOOST_FOREACH(const uint256& conflict, wtx.GetConflicts())
         conflicts.push_back(conflict.GetHex());
     entry.push_back(Pair("walletconflicts", conflicts));
+    Array respends;
+    BOOST_FOREACH(const uint256& respend, wtx.GetConflicts(false))
+        respends.push_back(respend.GetHex());
+    entry.push_back(Pair("respendsobserved", respends));
     entry.push_back(Pair("time", wtx.GetTxTime()));
     entry.push_back(Pair("timereceived", (int64_t)wtx.nTimeReceived));
     BOOST_FOREACH(const PAIRTYPE(string,string)& item, wtx.mapValue)
@@ -1211,6 +1215,12 @@ Value listtransactions(const Array& params, bool fHelp)
             "    \"blockindex\": n,          (numeric) The block index containing the transaction. Available for 'send' and 'receive'\n"
             "                                          category of transactions.\n"
             "    \"txid\": \"transactionid\", (string) The transaction id. Available for 'send' and 'receive' category of transactions.\n"
+            "    \"walletconflicts\" : [\n"
+            "        \"conflictid\",  (string) Ids of transactions, including equivalent clones, that re-spend a txid input.\n"
+            "    ],\n"
+            "    \"respendsobserved\" : [\n"
+            "        \"respendid\",  (string) Ids of transactions, NOT equivalent clones, that re-spend a txid input. \"Double-spends.\"\n"
+            "    ],\n"
             "    \"time\": xxx,              (numeric) The transaction time in seconds since epoch (midnight Jan 1 1970 GMT).\n"
             "    \"timereceived\": xxx,      (numeric) The time received in seconds since epoch (midnight Jan 1 1970 GMT). Available \n"
             "                                          for 'send' and 'receive' category of transactions.\n"
@@ -1376,6 +1386,12 @@ Value listsinceblock(const Array& params, bool fHelp)
             "    \"blockindex\": n,          (numeric) The block index containing the transaction. Available for 'send' and 'receive' category of transactions.\n"
             "    \"blocktime\": xxx,         (numeric) The block time in seconds since epoch (1 Jan 1970 GMT).\n"
             "    \"txid\": \"transactionid\",  (string) The transaction id. Available for 'send' and 'receive' category of transactions.\n"
+            "    \"walletconflicts\" : [\n"
+            "        \"conflictid\",  (string) Ids of transactions, including equivalent clones, that re-spend a txid input.\n"
+            "    ],\n"
+            "    \"respendsobserved\" : [\n"
+            "        \"respendid\",  (string) Ids of transactions, NOT equivalent clones, that re-spend a txid input. \"Double-spends.\"\n"
+            "    ],\n"
             "    \"time\": xxx,              (numeric) The transaction time in seconds since epoch (Jan 1 1970 GMT).\n"
             "    \"timereceived\": xxx,      (numeric) The time received in seconds since epoch (Jan 1 1970 GMT). Available for 'send' and 'receive' category of transactions.\n"
             "    \"comment\": \"...\",       (string) If a comment is associated with the transaction.\n"
@@ -1448,6 +1464,12 @@ Value gettransaction(const Array& params, bool fHelp)
             "  \"blockindex\" : xx,       (numeric) The block index\n"
             "  \"blocktime\" : ttt,       (numeric) The time in seconds since epoch (1 Jan 1970 GMT)\n"
             "  \"txid\" : \"transactionid\",   (string) The transaction id.\n"
+            "  \"walletconflicts\" : [\n"
+            "      \"conflictid\",  (string) Ids of transactions, including equivalent clones, that re-spend a txid input.\n"
+            "  ],\n"
+            "  \"respendsobserved\" : [\n"
+            "      \"respendid\",  (string) Ids of transactions, NOT equivalent clones, that re-spend a txid input. \"Double-spends.\"\n"
+            "  ],\n"
             "  \"time\" : ttt,            (numeric) The transaction time in seconds since epoch (1 Jan 1970 GMT)\n"
             "  \"timereceived\" : ttt,    (numeric) The time received in seconds since epoch (1 Jan 1970 GMT)\n"
             "  \"details\" : [\n"

src/test/bloom_tests.cpp

@@ -45,6 +45,10 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_serialize)
         expected[i] = (char)vch[i];
 
     BOOST_CHECK_EQUAL_COLLECTIONS(stream.begin(), stream.end(), expected.begin(), expected.end());
+
+    BOOST_CHECK_MESSAGE( filter.contains(ParseHex("99108ad8ed9bb6274d3980bab5a85c048f0950c8")), "BloomFilter doesn't contain just-inserted object!");
+    filter.clear();
+    BOOST_CHECK_MESSAGE( !filter.contains(ParseHex("99108ad8ed9bb6274d3980bab5a85c048f0950c8")), "BloomFilter should be empty!");
 }
 
 BOOST_AUTO_TEST_CASE(bloom_create_insert_serialize_with_tweak)

src/txmempool.cpp

@@ -415,7 +415,6 @@ void CTxMemPool::remove(const CTransaction &tx, std::list<CTransaction>& removed
 void CTxMemPool::removeConflicts(const CTransaction &tx, std::list<CTransaction>& removed)
 {
     // Remove transactions which depend on inputs of tx, recursively
-    list<CTransaction> result;
     LOCK(cs);
     BOOST_FOREACH(const CTxIn &txin, tx.vin) {
         std::map<COutPoint, CInPoint>::iterator it = mapNextTx.find(txin.prevout);

src/ui_interface.h

@@ -21,7 +21,8 @@ enum ChangeType
 {
     CT_NEW,
     CT_UPDATED,
-    CT_DELETED
+    CT_DELETED,
+    CT_GOT_CONFLICT
 };
 
 /** Signals for UI communication. */

src/wallet.cpp

@@ -256,7 +256,7 @@ bool CWallet::SetMaxVersion(int nVersion)
     return true;
 }
 
-set<uint256> CWallet::GetConflicts(const uint256& txid) const
+set<uint256> CWallet::GetConflicts(const uint256& txid, bool includeEquivalent) const
 {
     set<uint256> result;
     AssertLockHeld(cs_wallet);
@@ -274,6 +274,7 @@ set<uint256> CWallet::GetConflicts(const uint256& txid) const
             continue;  // No conflict if zero or one spends
         range = mapTxSpends.equal_range(txin.prevout);
         for (TxSpends::const_iterator it = range.first; it != range.second; ++it)
+            if (includeEquivalent || !wtx.IsEquivalentTo(mapWallet.at(it->second)))
                 result.insert(it->second);
     }
     return result;
@@ -303,6 +304,7 @@ void CWallet::SyncMetaData(pair<TxSpends::iterator, TxSpends::iterator> range)
         const uint256& hash = it->second;
         CWalletTx* copyTo = &mapWallet[hash];
         if (copyFrom == copyTo) continue;
+        if (!copyFrom->IsEquivalentTo(*copyTo)) continue;
         copyTo->mapValue = copyFrom->mapValue;
         copyTo->vOrderForm = copyFrom->vOrderForm;
         // fTimeReceivedIsTxTime not copied on purpose
@@ -588,6 +590,28 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFromLoadWallet)
         // Notify UI of new or updated transaction
         NotifyTransactionChanged(this, hash, fInsertedNew ? CT_NEW : CT_UPDATED);
 
+        // Notifications for existing transactions that now have conflicts with this one
+        if (fInsertedNew)
+        {
+            BOOST_FOREACH(const uint256& conflictHash, wtxIn.GetConflicts(false))
+            {
+                CWalletTx& txConflict = mapWallet[conflictHash];
+                NotifyTransactionChanged(this, conflictHash, CT_UPDATED); //Updates UI table
+                if (IsFromMe(txConflict) || IsMine(txConflict))
+                {
+                    NotifyTransactionChanged(this, conflictHash, CT_GOT_CONFLICT);  //Throws dialog
+                    // external respend notify
+                    std::string strCmd = GetArg("-respendnotify", "");
+                    if (!strCmd.empty())
+                    {
+                        boost::replace_all(strCmd, "%s", wtxIn.GetHash().GetHex());
+                        boost::replace_all(strCmd, "%t", conflictHash.GetHex());
+                        boost::thread t(runCommand, strCmd); // thread runs free
+                    }
+                }
+            }
+        }
+
         // notify an external script when a wallet transaction comes in or is updated
         std::string strCmd = GetArg("-walletnotify", "");
 
@@ -610,7 +634,12 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransaction& tx, const CBlock* pbl
         AssertLockHeld(cs_wallet);
         bool fExisted = mapWallet.count(tx.GetHash());
         if (fExisted && !fUpdate) return false;
-        if (fExisted || IsMine(tx) || IsFromMe(tx))
+
+        bool fIsConflicting = IsConflicting(tx);
+        if (fIsConflicting)
+            nConflictsReceived++;
+
+        if (fExisted || IsMine(tx) || IsFromMe(tx) || fIsConflicting)
         {
             CWalletTx wtx(this,tx);
             // Get merkle branch if transaction was found in a block
@@ -896,7 +925,7 @@ void CWallet::ReacceptWalletTransactions()
 
         int nDepth = wtx.GetDepthInMainChain();
 
-        if (!wtx.IsCoinBase() && nDepth < 0)
+        if (!wtx.IsCoinBase() && nDepth < 0 && (IsMine(wtx) || IsFromMe(wtx)))
         {
             // Try to add to memory pool
             LOCK(mempool.cs);
@@ -916,13 +945,13 @@ void CWalletTx::RelayWalletTransaction()
     }
 }
 
-set<uint256> CWalletTx::GetConflicts() const
+set<uint256> CWalletTx::GetConflicts(bool includeEquivalent) const
 {
     set<uint256> result;
     if (pwallet != NULL)
     {
         uint256 myHash = GetHash();
-        result = pwallet->GetConflicts(myHash);
+        result = pwallet->GetConflicts(myHash, includeEquivalent);
         result.erase(myHash);
     }
     return result;

src/wallet.h

@@ -141,6 +141,9 @@ public:
     MasterKeyMap mapMasterKeys;
     unsigned int nMasterKeyMaxID;
 
+    // Increment to cause UI refresh, similar to new block
+    int64_t nConflictsReceived;
+
     CWallet()
     {
         SetNull();
@@ -163,6 +166,7 @@ public:
         nNextResend = 0;
         nLastResend = 0;
         nTimeFirstKey = 0;
+        nConflictsReceived = 0;
     }
 
     std::map<uint256, CWalletTx> mapWallet;
@@ -305,6 +309,13 @@ public:
     {
         return (GetDebit(tx) > 0);
     }
+    bool IsConflicting(const CTransaction& tx) const
+    {
+  	    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    	    if (mapTxSpends.count(txin.prevout))
+    	        return true;
+   	    return false;
+    }
     int64_t GetDebit(const CTransaction& tx) const
     {
         int64_t nDebit = 0;
@@ -377,7 +388,7 @@ public:
     int GetVersion() { LOCK(cs_wallet); return nWalletVersion; }
 
     // Get wallet transactions that conflict with given transaction (spend same outputs)
-    std::set<uint256> GetConflicts(const uint256& txid) const;
+    std::set<uint256> GetConflicts(const uint256& txid, bool includeEquivalent) const;
 
     /** Address book entry changed.
      * @note called with lock cs_wallet held.
@@ -699,7 +710,7 @@ public:
 
     void RelayWalletTransaction();
 
-    std::set<uint256> GetConflicts() const;
+    std::set<uint256> GetConflicts(bool includeEquivalent=true) const;
 };