Revert "Relay double-spends, subject to anti-DOS"

This reverts commit d640a3ceab.

src/core.cpp

@@ -124,22 +124,6 @@ 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

@@ -255,9 +255,6 @@ 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

@@ -1229,7 +1229,6 @@ 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

@@ -7,7 +7,6 @@
 
 #include "addrman.h"
 #include "alert.h"
-#include "bloom.h"
 #include "chainparams.h"
 #include "checkpoints.h"
 #include "checkqueue.h"
@@ -126,10 +125,6 @@ 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
@@ -152,25 +147,10 @@ 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));
@@ -890,22 +870,6 @@ int64_t GetMinRelayFee(const CTransaction& tx, unsigned int nBytes, bool fAllowF
     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);
-
-    // Use an exponentially decaying ~10-minute window:
-    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)
@@ -940,10 +904,9 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
     for (unsigned int i = 0; i < tx.vin.size(); i++)
     {
         COutPoint outpoint = tx.vin[i].prevout;
-        // Does tx conflict with a member of the pool, and is it not equivalent to that member?
+        if (pool.mapNextTx.count(outpoint))
-        if (pool.mapNextTx.count(outpoint) && !tx.IsEquivalentTo(*pool.mapNextTx[outpoint].ptx))
         {
-            g_signals.DetectedDoubleSpend(outpoint, tx, false);
+            // Disable replacement feature for now
             return false;
         }
     }
@@ -1015,15 +978,23 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
         // be annoying or make others' transactions take longer to confirm.
         if (fLimitFree && nFees < ::minRelayTxFee.GetFee(nSize))
         {
+            static CCriticalSection csFreeLimiter;
             static double dFreeCount;
-            static int64_t nLastFreeTime;
+            static int64_t nLastTime;
-            static int64_t nFreeLimit = GetArg("-limitfreerelay", 15);
+            int64_t nNow = GetTime();
 
-		if (RateLimitExceeded(dFreeCount, nLastFreeTime, nFreeLimit, nSize))
+            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)
                 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 > ::minRelayTxFee.GetFee(nSize) * 10000)
@@ -1046,49 +1017,6 @@ 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

@@ -112,9 +112,6 @@ 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/txmempool.cpp

@@ -420,6 +420,7 @@ 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);