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-rw-r--r--main.cpp34
1 files changed, 22 insertions, 12 deletions
diff --git a/main.cpp b/main.cpp
index 7ddb24146c..298e76ecce 100644
--- a/main.cpp
+++ b/main.cpp
@@ -742,19 +742,29 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
if (nFees < GetMinFee(1000))
return error("AcceptToMemoryPool() : not enough fees");
- // Limit free transactions per 10 minutes
- if (nFees < CENT && GetBoolArg("-limitfreerelay"))
- {
- static int64 nNextReset;
- static int64 nFreeCount;
- if (GetTime() > nNextReset)
- {
- nNextReset = GetTime() + 10 * 60;
- nFreeCount = 0;
+ // Continuously rate-limit free transactions
+ // This mitigates 'penny-flooding' -- sending thousands of free transactions just to
+ // be annoying or make other's transactions take longer to confirm.
+ if (nFees < CENT)
+ {
+ static CCriticalSection cs;
+ static double dFreeCount;
+ static int64 nLastTime;
+ int64 nNow = GetTime();
+
+ CRITICAL_BLOCK(cs)
+ {
+ // 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 && !IsFromMe())
+ return error("AcceptToMemoryPool() : free transaction rejected by rate limiter");
+ if (fDebug)
+ printf("Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
+ dFreeCount += nSize;
}
- if (nFreeCount > 150000 && !IsFromMe())
- return error("AcceptToMemoryPool() : free transaction rejected by rate limiter");
- nFreeCount += nSize;
}
}