Restore original bytespersigop as bytespersigopstrict

Plus a bugfix to accurately count sigops for this purpose

src/init.cpp

@@ -473,6 +473,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-dustrelayfee=<amt>", strprintf("Fee rate (in %s/kB) used to defined dust, the value of an output such that it will cost more than its value in fees at this fee rate to spend it. (default: %s)", CURRENCY_UNIT, FormatMoney(DUST_RELAY_TX_FEE)));
     }
     strUsage += HelpMessageOpt("-bytespersigop", strprintf(_("Equivalent bytes per sigop in transactions for relay and mining (default: %u)"), DEFAULT_BYTES_PER_SIGOP));
+    strUsage += HelpMessageOpt("-bytespersigopstrict", strprintf(_("Minimum bytes per sigop in transactions we relay and mine (default: %u)"), DEFAULT_BYTES_PER_SIGOP_STRICT));
     strUsage += HelpMessageOpt("-datacarrier", strprintf(_("Relay and mine data carrier transactions (default: %u)"), DEFAULT_ACCEPT_DATACARRIER));
     strUsage += HelpMessageOpt("-datacarriersize", strprintf(_("Maximum size of data in data carrier transactions we relay and mine (default: %u)"), MAX_OP_RETURN_RELAY));
     strUsage += HelpMessageOpt("-mempoolreplacement", strprintf(_("Enable transaction replacement in the memory pool (default: %u)"), DEFAULT_ENABLE_REPLACEMENT));

src/policy/policy.cpp

@@ -7,6 +7,7 @@
 
 #include <policy/policy.h>
 
+#include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <validation.h>
 #include <coins.h>
@@ -291,6 +292,7 @@ bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs,
 CFeeRate incrementalRelayFee = CFeeRate(DEFAULT_INCREMENTAL_RELAY_FEE);
 CFeeRate dustRelayFee = CFeeRate(DUST_RELAY_TX_FEE);
 unsigned int nBytesPerSigOp = DEFAULT_BYTES_PER_SIGOP;
+unsigned int nBytesPerSigOpStrict = DEFAULT_BYTES_PER_SIGOP_STRICT;
 
 int64_t GetVirtualTransactionSize(int64_t nWeight, int64_t nSigOpCost)
 {
@@ -301,3 +303,32 @@ int64_t GetVirtualTransactionSize(const CTransaction& tx, int64_t nSigOpCost)
 {
     return GetVirtualTransactionSize(GetTransactionWeight(tx), nSigOpCost);
 }
+
+int64_t GetAccurateTransactionSigOpCost(const CTransaction& tx, const CCoinsViewCache& inputs, int flags)
+{
+    if (tx.IsCoinBase()) {
+        return 0;
+    }
+
+    unsigned int nSigOps = 0;
+    for (const auto& txin : tx.vin) {
+        nSigOps += txin.scriptSig.GetSigOpCount(false);
+    }
+
+    if (flags & SCRIPT_VERIFY_P2SH) {
+        nSigOps += GetP2SHSigOpCount(tx, inputs);
+    }
+
+    nSigOps *= WITNESS_SCALE_FACTOR;
+
+    if (flags & SCRIPT_VERIFY_WITNESS) {
+        for (const auto& txin : tx.vin) {
+            const Coin& coin = inputs.AccessCoin(txin.prevout);
+            assert(!coin.IsSpent());
+            const CTxOut &prevout = coin.out;
+            nSigOps += CountWitnessSigOps(txin.scriptSig, prevout.scriptPubKey, &txin.scriptWitness, flags);
+        }
+    }
+
+    return nSigOps;
+}

src/policy/policy.h

@@ -33,6 +33,8 @@ static const unsigned int DEFAULT_MAX_MEMPOOL_SIZE = 300;
 static const unsigned int DEFAULT_INCREMENTAL_RELAY_FEE = 1000;
 /** Default for -bytespersigop */
 static const unsigned int DEFAULT_BYTES_PER_SIGOP = 20;
+/** Default for -bytespersigopstrict */
+static const unsigned int DEFAULT_BYTES_PER_SIGOP_STRICT = 20;
 /** The maximum number of witness stack items in a standard P2WSH script */
 static const unsigned int MAX_STANDARD_P2WSH_STACK_ITEMS = 100;
 /** The maximum size of each witness stack item in a standard P2WSH script */
@@ -108,9 +110,15 @@ bool IsWitnessStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs,
 extern CFeeRate incrementalRelayFee;
 extern CFeeRate dustRelayFee;
 extern unsigned int nBytesPerSigOp;
+extern unsigned int nBytesPerSigOpStrict;
 
 /** Compute the virtual transaction size (weight reinterpreted as bytes). */
 int64_t GetVirtualTransactionSize(int64_t nWeight, int64_t nSigOpCost);
 int64_t GetVirtualTransactionSize(const CTransaction& tx, int64_t nSigOpCost = 0);
 
+/** Compute accurate total signature operation cost of a transaction.
+ *  Not consensus-critical, since legacy sigops counting is always used in the protocol.
+ */
+int64_t GetAccurateTransactionSigOpCost(const CTransaction&, const CCoinsViewCache& inputs, int flags);
+
 #endif // BITCOIN_POLICY_POLICY_H

src/validation.cpp

@@ -738,9 +738,12 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         // itself can contain sigops MAX_STANDARD_TX_SIGOPS is less than
         // MAX_BLOCK_SIGOPS; we still consider this an invalid rather than
         // merely non-standard transaction.
-        if (nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST)
+        // To avoid rejecting low-sigop bare-multisig transactions, the sigops
+        // are counted a second time more accurately.
+        if ((nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST) || (nBytesPerSigOpStrict && GetAccurateTransactionSigOpCost(tx, view, STANDARD_SCRIPT_VERIFY_FLAGS) > nSize * WITNESS_SCALE_FACTOR / nBytesPerSigOpStrict)) {
             MaybeRejectDbg(REJECT_NONSTANDARD, "bad-txns-too-many-sigops", false,
                 strprintf("%d", nSigOpsCost));
+        }
 
         poolMinFeeRate = pool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
         CAmount mempoolRejectFee = poolMinFeeRate.GetFee(nSize);