Require sufficent priority for relay of free transactions

Rebased-From: 1c52aad540ec1370db60fd68fc3485413e3cb8e1
Github-Pull: #5535

1 files changed, 7 insertions, 2 deletions

diff --git a/src/main.cpp b/src/main.cpp
index c40a5e1672..cf2d07604f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1022,7 +1022,12 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
                                       hash.ToString(), nFees, txMinFee),
                              REJECT_INSUFFICIENTFEE, "insufficient fee");
 
-        // Continuously rate-limit free (really, very-low-fee)transactions
+        // Require that free transactions have sufficient priority to be mined in the next block.
+        if (GetBoolArg("-relaypriority", true) && nFees < ::minRelayTxFee.GetFee(nSize) && !AllowFree(view.GetPriority(tx, chainActive.Height() + 1))) {
+            return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "insufficient priority");
+        }
+
+        // Continuously rate-limit free (really, very-low-fee) transactions
         // This mitigates 'penny-flooding' -- sending thousands of free transactions just to
         // be annoying or make others' transactions take longer to confirm.
         if (fLimitFree && nFees < ::minRelayTxFee.GetFee(nSize))
@@ -1041,7 +1046,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
             // 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");
+                                 REJECT_INSUFFICIENTFEE, "rate limited free transaction");
             LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
             dFreeCount += nSize;
         }