No longer allow "free" transactions

Remove -limitfreerelay and always enforce minRelayTxFee in the mempool (except from disconnected blocks)

Remove -relaypriority, the option was only used for the ability to allow free transactions to be relayed regardless of their priority.  Both notions no longer apply.

8 files changed, 9 insertions, 50 deletions

diff --git a/src/init.cpp b/src/init.cpp
index c6026646d0..3276ec9f13 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -444,8 +444,6 @@ std::string HelpMessage(HelpMessageMode mode)
     {
         strUsage += HelpMessageOpt("-logtimemicros", strprintf("Add microsecond precision to debug timestamps (default: %u)", DEFAULT_LOGTIMEMICROS));
         strUsage += HelpMessageOpt("-mocktime=<n>", "Replace actual time with <n> seconds since epoch (default: 0)");
-        strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default: %u)", DEFAULT_LIMITFREERELAY));
-        strUsage += HelpMessageOpt("-relaypriority", strprintf("Require high priority for relaying free or low-fee transactions (default: %u)", DEFAULT_RELAYPRIORITY));
         strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> MiB (default: %u)", DEFAULT_MAX_SIG_CACHE_SIZE));
         strUsage += HelpMessageOpt("-maxtipage=<n>", strprintf("Maximum tip age in seconds to consider node in initial block download (default: %u)", DEFAULT_MAX_TIP_AGE));
     }
@@ -975,7 +973,7 @@ bool AppInitParameterInteraction()
     if (nConnectTimeout <= 0)
         nConnectTimeout = DEFAULT_CONNECT_TIMEOUT;
 
-    // Fee-per-kilobyte amount considered the same as "free"
+    // Fee-per-kilobyte amount required for mempool acceptance and relay
     // If you are mining, be careful setting this:
     // if you set it to zero then
     // a transaction spammer can cheaply fill blocks using
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 3ec1a1c27d..71a0a1de22 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -1853,7 +1853,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                             LogPrint("mempool", "   invalid orphan tx %s\n", orphanHash.ToString());
                         }
                         // Has inputs but not accepted to mempool
-                        // Probably non-standard or insufficient fee/priority
+                        // Probably non-standard or insufficient fee
                         LogPrint("mempool", "   removed orphan tx %s\n", orphanHash.ToString());
                         vEraseQueue.push_back(orphanHash);
                         if (!orphanTx.HasWitness() && !stateDummy.CorruptionPossible()) {
@@ -3249,9 +3249,8 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 static CFeeRate default_feerate(DEFAULT_MIN_RELAY_TX_FEE);
                 static FeeFilterRounder filterRounder(default_feerate);
                 CAmount filterToSend = filterRounder.round(currentFilter);
-                // If we don't allow free transactions, then we always have a fee filter of at least minRelayTxFee
-                if (GetArg("-limitfreerelay", DEFAULT_LIMITFREERELAY) <= 0)
-                    filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
+                // We always have a fee filter of at least minRelayTxFee
+                filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
                 if (filterToSend != pto->lastSentFeeFilter) {
                     connman.PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
                     pto->lastSentFeeFilter = filterToSend;
diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index 140cb4840b..3045fa2b53 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -61,7 +61,7 @@ UniValue getinfo(const JSONRPCRequest& request)
             "  \"keypoolsize\": xxxx,        (numeric) how many new keys are pre-generated\n"
             "  \"unlocked_until\": ttt,      (numeric) the timestamp in seconds since epoch (midnight Jan 1 1970 GMT) that the wallet is unlocked for transfers, or 0 if the wallet is locked\n"
             "  \"paytxfee\": x.xxxx,         (numeric) the transaction fee set in " + CURRENCY_UNIT + "/kB\n"
-            "  \"relayfee\": x.xxxx,         (numeric) minimum relay fee for non-free transactions in " + CURRENCY_UNIT + "/kB\n"
+            "  \"relayfee\": x.xxxx,         (numeric) minimum relay fee for transactions in " + CURRENCY_UNIT + "/kB\n"
             "  \"errors\": \"...\"           (string) any error messages\n"
             "}\n"
             "\nExamples:\n"
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index f590db5efa..a7169749c3 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -417,7 +417,7 @@ UniValue getnetworkinfo(const JSONRPCRequest& request)
             "  }\n"
             "  ,...\n"
             "  ],\n"
-            "  \"relayfee\": x.xxxxxxxx,                (numeric) minimum relay fee for non-free transactions in " + CURRENCY_UNIT + "/kB\n"
+            "  \"relayfee\": x.xxxxxxxx,                (numeric) minimum relay fee for transactions in " + CURRENCY_UNIT + "/kB\n"
             "  \"incrementalfee\": x.xxxxxxxx,          (numeric) minimum fee increment for mempool limiting or BIP 125 replacement in " + CURRENCY_UNIT + "/kB\n"
             "  \"localaddresses\": [                    (array) list of local addresses\n"
             "  {\n"
diff --git a/src/txmempool.h b/src/txmempool.h
index 4af85195c8..9af65bd077 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -30,18 +30,6 @@
 class CAutoFile;
 class CBlockIndex;
 
-inline double AllowFreeThreshold()
-{
-    return COIN * 144 / 250;
-}
-
-inline bool AllowFree(double dPriority)
-{
-    // Large (in bytes) low-priority (new, small-coin) transactions
-    // need a fee.
-    return dPriority > AllowFreeThreshold();
-}
-
 /** Fake height value used in CCoins to signify they are only in the memory pool (since 0.8) */
 static const unsigned int MEMPOOL_HEIGHT = 0x7FFFFFFF;
 
diff --git a/src/validation.cpp b/src/validation.cpp
index e84b1a7281..a21dc25a55 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -753,32 +753,11 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         CAmount mempoolRejectFee = pool.GetMinFee(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFee(nSize);
         if (mempoolRejectFee > 0 && nModifiedFees < mempoolRejectFee) {
             return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met", false, strprintf("%d < %d", nFees, mempoolRejectFee));
-        } else if (GetBoolArg("-relaypriority", DEFAULT_RELAYPRIORITY) && nModifiedFees < ::minRelayTxFee.GetFee(nSize) && !AllowFree(entry.GetPriority(chainActive.Height() + 1))) {
-            // Require that free transactions have sufficient priority to be mined in the next block.
-            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 && nModifiedFees < ::minRelayTxFee.GetFee(nSize))
-        {
-            static CCriticalSection csFreeLimiter;
-            static double dFreeCount;
-            static int64_t nLastTime;
-            int64_t nNow = GetTime();
-
-            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 + nSize >= GetArg("-limitfreerelay", DEFAULT_LIMITFREERELAY) * 10 * 1000)
-                return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "rate limited free transaction");
-            LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
-            dFreeCount += nSize;
+        // No transactions are allowed below minRelayTxFee except from disconnected blocks
+        if (fLimitFree && nModifiedFees < ::minRelayTxFee.GetFee(nSize)) {
+            return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "min relay fee not met");
         }
 
         if (nAbsurdFee && nFees > nAbsurdFee)
diff --git a/src/validation.h b/src/validation.h
index 9c606f2419..43f0dbae34 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -122,8 +122,6 @@ static const int64_t BLOCK_DOWNLOAD_TIMEOUT_BASE = 1000000;
 /** Additional block download timeout per parallel downloading peer (i.e. 5 min) */
 static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;
 
-static const unsigned int DEFAULT_LIMITFREERELAY = 0;
-static const bool DEFAULT_RELAYPRIORITY = true;
 static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
 /** Maximum age of our tip in seconds for us to be considered current for fee estimation */
 static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index cf3c6ee121..ba16cdf267 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3842,9 +3842,6 @@ bool CWallet::ParameterInteraction()
     bSpendZeroConfChange = GetBoolArg("-spendzeroconfchange", DEFAULT_SPEND_ZEROCONF_CHANGE);
     fWalletRbf = GetBoolArg("-walletrbf", DEFAULT_WALLET_RBF);
 
-    if (GetBoolArg("-sendfreetransactions", false))
-        InitWarning("The argument -sendfreetransactions is no longer supported.");
-
     return true;
 }