Merge #11742: rpc: Add testmempoolaccept

b55555d rpc: Add testmempoolaccept (MarcoFalke)

Pull request description:

  To check if a single raw transaction makes it into the current transaction pool, one had to call `sendrawtransaction`. However, on success, this adds the transaction to the mempool with no easy way to undo.

  The call `testmempoolaccept` is introduced to provide a way to solely check the result without changing the mempool state.

Tree-SHA512: 5afd9311190135cee8fc1f229c7d39bf893f1028f29e28d34f70df820198ff97b4bf86b41cbbd6e6c36a5c30073cefa92d541c74a4939c7a2a6fa283dfd41b63

6 files changed, 99 insertions, 9 deletions

diff --git a/src/rpc/client.cpp b/src/rpc/client.cpp
index e12685da65..01f932dbb4 100644
--- a/src/rpc/client.cpp
+++ b/src/rpc/client.cpp
@@ -103,6 +103,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "signrawtransactionwithkey", 2, "prevtxs" },
     { "signrawtransactionwithwallet", 1, "prevtxs" },
     { "sendrawtransaction", 1, "allowhighfees" },
+    { "testmempoolaccept", 0, "rawtxs" },
+    { "testmempoolaccept", 1, "allowhighfees" },
     { "combinerawtransaction", 0, "txs" },
     { "fundrawtransaction", 1, "options" },
     { "fundrawtransaction", 2, "iswitness" },
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 77040f75fd..9d7aa58894 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1134,6 +1134,87 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
     return hashTx.GetHex();
 }
 
+UniValue testmempoolaccept(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2) {
+        throw std::runtime_error(
+            // clang-format off
+            "testmempoolaccept [\"rawtxs\"] ( allowhighfees )\n"
+            "\nReturns if raw transaction (serialized, hex-encoded) would be accepted by mempool.\n"
+            "\nThis checks if the transaction violates the consensus or policy rules.\n"
+            "\nSee sendrawtransaction call.\n"
+            "\nArguments:\n"
+            "1. [\"rawtxs\"]       (array, required) An array of hex strings of raw transactions.\n"
+            "                                        Length must be one for now.\n"
+            "2. allowhighfees    (boolean, optional, default=false) Allow high fees\n"
+            "\nResult:\n"
+            "[                   (array) The result of the mempool acceptance test for each raw transaction in the input array.\n"
+            "                            Length is exactly one for now.\n"
+            " {\n"
+            "  \"txid\"           (string) The transaction hash in hex\n"
+            "  \"allowed\"        (boolean) If the mempool allows this tx to be inserted\n"
+            "  \"reject-reason\"  (string) Rejection string (only present when 'allowed' is false)\n"
+            " }\n"
+            "]\n"
+            "\nExamples:\n"
+            "\nCreate a transaction\n"
+            + HelpExampleCli("createrawtransaction", "\"[{\\\"txid\\\" : \\\"mytxid\\\",\\\"vout\\\":0}]\" \"{\\\"myaddress\\\":0.01}\"") +
+            "Sign the transaction, and get back the hex\n"
+            + HelpExampleCli("signrawtransaction", "\"myhex\"") +
+            "\nTest acceptance of the transaction (signed hex)\n"
+            + HelpExampleCli("testmempoolaccept", "\"signedhex\"") +
+            "\nAs a json rpc call\n"
+            + HelpExampleRpc("testmempoolaccept", "[\"signedhex\"]")
+            // clang-format on
+            );
+    }
+
+    ObserveSafeMode();
+
+    RPCTypeCheck(request.params, {UniValue::VARR, UniValue::VBOOL});
+    if (request.params[0].get_array().size() != 1) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Array must contain exactly one raw transaction for now");
+    }
+
+    CMutableTransaction mtx;
+    if (!DecodeHexTx(mtx, request.params[0].get_array()[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    }
+    CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
+    const uint256& tx_hash = tx->GetHash();
+
+    CAmount max_raw_tx_fee = ::maxTxFee;
+    if (!request.params[1].isNull() && request.params[1].get_bool()) {
+        max_raw_tx_fee = 0;
+    }
+
+    UniValue result(UniValue::VARR);
+    UniValue result_0(UniValue::VOBJ);
+    result_0.pushKV("txid", tx_hash.GetHex());
+
+    CValidationState state;
+    bool missing_inputs;
+    bool test_accept_res;
+    {
+        LOCK(cs_main);
+        test_accept_res = AcceptToMemoryPool(mempool, state, std::move(tx), &missing_inputs,
+            nullptr /* plTxnReplaced */, false /* bypass_limits */, max_raw_tx_fee, /* test_accpet */ true);
+    }
+    result_0.pushKV("allowed", test_accept_res);
+    if (!test_accept_res) {
+        if (state.IsInvalid()) {
+            result_0.pushKV("reject-reason", strprintf("%i: %s", state.GetRejectCode(), state.GetRejectReason()));
+        } else if (missing_inputs) {
+            result_0.pushKV("reject-reason", "missing-inputs");
+        } else {
+            result_0.pushKV("reject-reason", state.GetRejectReason());
+        }
+    }
+
+    result.push_back(std::move(result_0));
+    return result;
+}
+
 static const CRPCCommand commands[] =
 { //  category              name                            actor (function)            argNames
   //  --------------------- ------------------------        -----------------------     ----------
@@ -1145,6 +1226,7 @@ static const CRPCCommand commands[] =
     { "rawtransactions",    "combinerawtransaction",        &combinerawtransaction,     {"txs"} },
     { "rawtransactions",    "signrawtransaction",           &signrawtransaction,        {"hexstring","prevtxs","privkeys","sighashtype"} }, /* uses wallet if enabled */
     { "rawtransactions",    "signrawtransactionwithkey",    &signrawtransactionwithkey, {"hexstring","privkeys","prevtxs","sighashtype"} },
+    { "rawtransactions",    "testmempoolaccept",            &testmempoolaccept,         {"rawtxs","allowhighfees"} },
 
     { "blockchain",         "gettxoutproof",                &gettxoutproof,             {"txids", "blockhash"} },
     { "blockchain",         "verifytxoutproof",             &verifytxoutproof,          {"proof"} },
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index cc639288d3..d03429ca81 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -447,7 +447,7 @@ void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason)
 // Also assumes that if an entry is in setDescendants already, then all
 // in-mempool descendants of it are already in setDescendants as well, so that we
 // can save time by not iterating over those entries.
-void CTxMemPool::CalculateDescendants(txiter entryit, setEntries &setDescendants)
+void CTxMemPool::CalculateDescendants(txiter entryit, setEntries& setDescendants) const
 {
     setEntries stage;
     if (setDescendants.count(entryit) == 0) {
diff --git a/src/txmempool.h b/src/txmempool.h
index 699f6b554b..a1cde6f779 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -600,7 +600,7 @@ public:
     /** Populate setDescendants with all in-mempool descendants of hash.
      *  Assumes that setDescendants includes all in-mempool descendants of anything
      *  already in it.  */
-    void CalculateDescendants(txiter it, setEntries &setDescendants);
+    void CalculateDescendants(txiter it, setEntries& setDescendants) const;
 
     /** The minimum fee to get into the mempool, which may itself not be enough
       *  for larger-sized transactions.
diff --git a/src/validation.cpp b/src/validation.cpp
index 77764ff923..df8729e382 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -543,7 +543,7 @@ static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, CValidationSt
 
 static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool& pool, CValidationState& state, const CTransactionRef& ptx,
                               bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
-                              bool bypass_limits, const CAmount& nAbsurdFee, std::vector<COutPoint>& coins_to_uncache)
+                              bool bypass_limits, const CAmount& nAbsurdFee, std::vector<COutPoint>& coins_to_uncache, bool test_accept)
 {
     const CTransaction& tx = *ptx;
     const uint256 hash = tx.GetHash();
@@ -935,6 +935,11 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
             }
         }
 
+        if (test_accept) {
+            // Tx was accepted, but not added
+            return true;
+        }
+
         // Remove conflicting transactions from the mempool
         for (const CTxMemPool::txiter it : allConflicting)
         {
@@ -974,10 +979,10 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
 /** (try to) add transaction to memory pool with a specified acceptance time **/
 static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPool& pool, CValidationState &state, const CTransactionRef &tx,
                         bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
-                        bool bypass_limits, const CAmount nAbsurdFee)
+                        bool bypass_limits, const CAmount nAbsurdFee, bool test_accept)
 {
     std::vector<COutPoint> coins_to_uncache;
-    bool res = AcceptToMemoryPoolWorker(chainparams, pool, state, tx, pfMissingInputs, nAcceptTime, plTxnReplaced, bypass_limits, nAbsurdFee, coins_to_uncache);
+    bool res = AcceptToMemoryPoolWorker(chainparams, pool, state, tx, pfMissingInputs, nAcceptTime, plTxnReplaced, bypass_limits, nAbsurdFee, coins_to_uncache, test_accept);
     if (!res) {
         for (const COutPoint& hashTx : coins_to_uncache)
             pcoinsTip->Uncache(hashTx);
@@ -990,10 +995,10 @@ static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPo
 
 bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransactionRef &tx,
                         bool* pfMissingInputs, std::list<CTransactionRef>* plTxnReplaced,
-                        bool bypass_limits, const CAmount nAbsurdFee)
+                        bool bypass_limits, const CAmount nAbsurdFee, bool test_accept)
 {
     const CChainParams& chainparams = Params();
-    return AcceptToMemoryPoolWithTime(chainparams, pool, state, tx, pfMissingInputs, GetTime(), plTxnReplaced, bypass_limits, nAbsurdFee);
+    return AcceptToMemoryPoolWithTime(chainparams, pool, state, tx, pfMissingInputs, GetTime(), plTxnReplaced, bypass_limits, nAbsurdFee, test_accept);
 }
 
 /**
@@ -4640,7 +4645,8 @@ bool LoadMempool(void)
             if (nTime + nExpiryTimeout > nNow) {
                 LOCK(cs_main);
                 AcceptToMemoryPoolWithTime(chainparams, mempool, state, tx, nullptr /* pfMissingInputs */, nTime,
-                                           nullptr /* plTxnReplaced */, false /* bypass_limits */, 0 /* nAbsurdFee */);
+                                           nullptr /* plTxnReplaced */, false /* bypass_limits */, 0 /* nAbsurdFee */,
+                                           false /* test_accept */);
                 if (state.IsValid()) {
                     ++count;
                 } else {
diff --git a/src/validation.h b/src/validation.h
index 4031989f00..95c31bf0fc 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -308,7 +308,7 @@ void PruneBlockFilesManual(int nManualPruneHeight);
  * plTxnReplaced will be appended to with all transactions replaced from mempool **/
 bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransactionRef &tx,
                         bool* pfMissingInputs, std::list<CTransactionRef>* plTxnReplaced,
-                        bool bypass_limits, const CAmount nAbsurdFee);
+                        bool bypass_limits, const CAmount nAbsurdFee, bool test_accept=false);
 
 /** Convert CValidationState to a human-readable message for logging */
 std::string FormatStateMessage(const CValidationState &state);