RPC: rawtransaction: Add RBF support for createrawtransaction

Author: luke-jr

src/rpc/client.cpp

@@ -86,6 +86,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "createrawtransaction", 0, "inputs" },
     { "createrawtransaction", 1, "outputs" },
     { "createrawtransaction", 2, "locktime" },
+    { "createrawtransaction", 3, "optintorbf" },
     { "signrawtransaction", 1, "prevtxs" },
     { "signrawtransaction", 2, "privkeys" },
     { "sendrawtransaction", 1, "allowhighfees" },

src/rpc/rawtransaction.cpp

@@ -289,9 +289,9 @@ UniValue verifytxoutproof(const JSONRPCRequest& request)
 
 UniValue createrawtransaction(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() < 2 || request.params.size() > 3)
+    if (request.fHelp || request.params.size() < 2 || request.params.size() > 4)
         throw std::runtime_error(
-            "createrawtransaction [{\"txid\":\"id\",\"vout\":n},...] {\"address\":amount,\"data\":\"hex\",...} ( locktime )\n"
+            "createrawtransaction [{\"txid\":\"id\",\"vout\":n},...] {\"address\":amount,\"data\":\"hex\",...} ( locktime ) ( optintorbf )\n"
             "\nCreate a transaction spending the given inputs and creating new outputs.\n"
             "Outputs can be addresses or data.\n"
             "Returns hex-encoded raw transaction.\n"
@@ -315,6 +315,7 @@ UniValue createrawtransaction(const JSONRPCRequest& request)
             "      ,...\n"
             "    }\n"
             "3. locktime                  (numeric, optional, default=0) Raw locktime. Non-0 value also locktime-activates inputs\n"
+            "4. optintorbf                (boolean, optional, default=false) Allow this transaction to be replaced by a transaction with higher fees\n"
             "\nResult:\n"
             "\"transaction\"              (string) hex string of the transaction\n"
 
@@ -341,6 +342,8 @@ UniValue createrawtransaction(const JSONRPCRequest& request)
         rawTx.nLockTime = nLockTime;
     }
 
+    bool rbfOptIn = request.params.size() > 3 ? request.params[3].isTrue() : false;
+
     for (unsigned int idx = 0; idx < inputs.size(); idx++) {
         const UniValue& input = inputs[idx];
         const UniValue& o = input.get_obj();
@@ -354,16 +357,26 @@ UniValue createrawtransaction(const JSONRPCRequest& request)
         if (nOutput < 0)
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, vout must be positive");
 
-        uint32_t nSequence = (rawTx.nLockTime ? std::numeric_limits<uint32_t>::max() - 1 : std::numeric_limits<uint32_t>::max());
+        uint32_t nSequence;
+        if (rbfOptIn) {
+            nSequence = std::numeric_limits<uint32_t>::max() - 2;
+        } else if (rawTx.nLockTime) {
+            nSequence = std::numeric_limits<uint32_t>::max() - 1;
+        } else {
+            nSequence = std::numeric_limits<uint32_t>::max();
+        }
 
         // set the sequence number if passed in the parameters object
         const UniValue& sequenceObj = find_value(o, "sequence");
         if (sequenceObj.isNum()) {
             int64_t seqNr64 = sequenceObj.get_int64();
-            if (seqNr64 < 0 || seqNr64 > std::numeric_limits<uint32_t>::max())
+            if (seqNr64 < 0 || seqNr64 > std::numeric_limits<uint32_t>::max()) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, sequence number is out of range");
-            else
+            } else if (seqNr64 <= std::numeric_limits<uint32_t>::max() - 2 && request.params.size() > 3 && request.params[3].isFalse()) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter combination: Sequence number contradicts optintorbf option");
+            } else {
                 nSequence = (uint32_t)seqNr64;
+            }
         }
 
         CTxIn in(COutPoint(txid, nOutput), CScript(), nSequence);