Merge pull request #5535

1c52aad Require sufficent priority for relay of free transactions (Pieter Wuille)

2 files changed, 7 insertions, 1 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 1b0c909b96..03d67f0aa3 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -323,6 +323,7 @@ std::string HelpMessage(HelpMessageMode mode)
     if (GetBoolArg("-help-debug", false))
     {
         strUsage += "  -limitfreerelay=<n>    " + strprintf(_("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default:%u)"), 15) + "\n";
+        strUsage += "  -relaypriority         " + strprintf(_("Require high priority for relaying free or low-fee transactions (default:%u)"), 1) + "\n";
         strUsage += "  -maxsigcachesize=<n>   " + strprintf(_("Limit size of signature cache to <n> entries (default: %u)"), 50000) + "\n";
     }
     strUsage += "  -minrelaytxfee=<amt>   " + strprintf(_("Fees (in BTC/Kb) smaller than this are considered zero fee for relaying (default: %s)"), FormatMoney(::minRelayTxFee.GetFeePerK())) + "\n";
diff --git a/src/main.cpp b/src/main.cpp
index 0067e9a2b2..fa2b561489 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1030,6 +1030,11 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
                                       hash.ToString(), nFees, txMinFee),
                              REJECT_INSUFFICIENTFEE, "insufficient fee");
 
+        // 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.
@@ -1049,7 +1054,7 @@ 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;
         }