Add an option to allow users to disable relaying/mining data carrier transactions

src/init.cpp

@@ -309,6 +309,8 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += "  -shrinkdebugfile       " + _("Shrink debug.log file on client startup (default: 1 when no -debug)") + "\n";
     strUsage += "  -testnet               " + _("Use the test network") + "\n";
 
+    strUsage += "\n" + _("Node relay options:") + "\n";
+    strUsage += "  -datacarrier           " + _("Relay and mine data carrier transactions (default: 1)") + "\n";
     strUsage += "\n" + _("Block creation options:") + "\n";
     strUsage += "  -blockminsize=<n>      " + _("Set minimum block size in bytes (default: 0)") + "\n";
     strUsage += "  -blockmaxsize=<n>      " + strprintf(_("Set maximum block size in bytes (default: %d)"), DEFAULT_BLOCK_MAX_SIZE) + "\n";

src/script.cpp

@@ -1208,7 +1208,8 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsi
         mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));
 
         // Empty, provably prunable, data-carrying output
-        mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN << OP_SMALLDATA));
+        if (GetBoolArg("-datacarrier", true))
+            mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN << OP_SMALLDATA));
         mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN));
     }