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-rw-r--r--src/core.cpp16
-rw-r--r--src/core.h3
-rw-r--r--src/init.cpp1
-rw-r--r--src/main.cpp100
-rw-r--r--src/main.h3
-rw-r--r--src/txmempool.cpp1
6 files changed, 109 insertions, 15 deletions
diff --git a/src/core.cpp b/src/core.cpp
index 6c5ee1c0f8..ca28624529 100644
--- a/src/core.cpp
+++ b/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;
diff --git a/src/core.h b/src/core.h
index 27fda95552..8606831575 100644
--- a/src/core.h
+++ b/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
diff --git a/src/init.cpp b/src/init.cpp
index c7170b0f2d..bd732753e4 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1175,6 +1175,7 @@ bool AppInit2(boost::thread_group& threadGroup)
LogPrintf("mapAddressBook.size() = %u\n", pwalletMain ? pwalletMain->mapAddressBook.size() : 0);
#endif
+ RegisterInternalSignals();
StartNode(threadGroup);
if (fServer)
StartRPCThreads();
diff --git a/src/main.cpp b/src/main.cpp
index d86fd3a24d..48237c1b54 100644
--- a/src/main.cpp
+++ b/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"
@@ -122,6 +123,10 @@ namespace {
map<uint256, pair<NodeId, list<uint256>::iterator> > mapBlocksToDownload;
}
+// 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
@@ -143,9 +148,24 @@ 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;
}
+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));
@@ -824,6 +844,22 @@ 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);
+
+ // 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)
@@ -858,9 +894,10 @@ 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;
}
}
@@ -932,23 +969,15 @@ 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();
-
- LOCK(csFreeLimiter);
+ static int64_t nLastFreeTime;
+ static int64_t nFreeLimit = GetArg("-limitfreerelay", 15);
- // 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)
@@ -971,6 +1000,49 @@ 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
{
diff --git a/src/main.h b/src/main.h
index 0332db2163..c7f3dc4388 100644
--- a/src/main.h
+++ b/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 */
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 52f82ef040..97a426dd35 100644
--- a/src/txmempool.cpp
+++ b/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);