private void CheckRateLimit(MempoolValidationContext context, bool limitFree)
        {
            // TODO: sort this logic
            return;

            // 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 (limitFree && context.ModifiedFees < MinRelayTxFee.GetFee(context.EntrySize))
            {
                var nNow = this.dateTimeProvider.GetTime();

                // Use an exponentially decaying ~10-minute window:
                this.freeLimiter.FreeCount *= Math.Pow(1.0 - 1.0 / 600.0, (double)(nNow - this.freeLimiter.LastTime));
                this.freeLimiter.LastTime   = nNow;
                // -limitfreerelay unit is thousand-bytes-per-minute
                // At default rate it would take over a month to fill 1GB
                if (this.freeLimiter.FreeCount + context.EntrySize >= this.nodeArgs.Mempool.LimitFreeRelay * 10 * 1000)
                {
                    context.State.Fail(new MempoolError(MempoolErrors.RejectInsufficientfee, "rate limited free transaction")).Throw();
                }

                Logging.Logs.Mempool.LogInformation(
                    $"Rate limit dFreeCount: {this.freeLimiter.FreeCount} => {this.freeLimiter.FreeCount + context.EntrySize}");
                this.freeLimiter.FreeCount += context.EntrySize;
            }
        }
        private void CheckAncestors(MempoolValidationContext context)
        {
            // Calculate in-mempool ancestors, up to a limit.
            context.SetAncestors = new TxMempool.SetEntries();
            var    nLimitAncestors      = nodeArgs.Mempool.LimitAncestors;
            var    nLimitAncestorSize   = nodeArgs.Mempool.LimitAncestorSize * 1000;
            var    nLimitDescendants    = nodeArgs.Mempool.LimitDescendants;
            var    nLimitDescendantSize = nodeArgs.Mempool.LimitDescendantSize * 1000;
            string errString;

            if (!this.memPool.CalculateMemPoolAncestors(context.Entry, context.SetAncestors, nLimitAncestors,
                                                        nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, out errString))
            {
                context.State.Fail(MempoolErrors.TooLongMempoolChain, errString).Throw();
            }

            // A transaction that spends outputs that would be replaced by it is invalid. Now
            // that we have the set of all ancestors we can detect this
            // pathological case by making sure setConflicts and setAncestors don't
            // intersect.
            foreach (var ancestorIt in context.SetAncestors)
            {
                var hashAncestor = ancestorIt.TransactionHash;
                if (context.SetConflicts.Contains(hashAncestor))
                {
                    context.State.Fail(MempoolErrors.BadTxnsSpendsConflictingTx,
                                       $"{context.TransactionHash} spends conflicting transaction {hashAncestor}").Throw();
                }
            }
        }
        private void CheckMempoolCoinView(MempoolValidationContext context)
        {
            Guard.Assert(context.View != null);

            context.LockPoints = new LockPoints();

            // do we already have it?
            if (context.View.HaveCoins(context.TransactionHash))
            {
                context.State.Invalid(MempoolErrors.AlreadyKnown).Throw();
            }

            // do all inputs exist?
            // Note that this does not check for the presence of actual outputs (see the next check for that),
            // and only helps with filling in pfMissingInputs (to determine missing vs spent).
            foreach (var txin in context.Transaction.Inputs)
            {
                if (!context.View.HaveCoins(txin.PrevOut.Hash))
                {
                    context.State.MissingInputs = true;
                    context.State.Fail(new MempoolError()).Throw();                     // fMissingInputs and !state.IsInvalid() is used to detect this condition, don't set state.Invalid()
                }
            }

            // are the actual inputs available?
            if (!context.View.HaveInputs(context.Transaction))
            {
                context.State.Invalid(MempoolErrors.BadInputsSpent).Throw();
            }
        }
        /// <summary>
        /// Checks that are done before touching the mem pool.
        /// This checks don't need to run under the mempool scheduler
        /// </summary>
        private void PreMempoolChecks(MempoolValidationContext context)
        {
            // state filled in by CheckTransaction
            this.consensusValidator.CheckTransaction(context.Transaction);

            // Coinbase is only valid in a block, not as a loose transaction
            if (context.Transaction.IsCoinBase)
            {
                context.State.Fail(MempoolErrors.Coinbase).Throw();
            }

            // TODO: Implement Witness Code
            //// Reject transactions with witness before segregated witness activates (override with -prematurewitness)
            bool witnessEnabled = false;            //IsWitnessEnabled(chainActive.Tip(), Params().GetConsensus());

            //if (!GetBoolArg("-prematurewitness",false) && tx.HasWitness() && !witnessEnabled) {
            //    return state.DoS(0, false, REJECT_NONSTANDARD, "no-witness-yet", true);
            //}

            // Rather not work on nonstandard transactions (unless -testnet/-regtest)
            if (this.nodeArgs.RequireStandard)
            {
                this.CheckStandardTransaction(context, witnessEnabled);
            }

            // Only accept nLockTime-using transactions that can be mined in the next
            // block; we don't want our mempool filled up with transactions that can't
            // be mined yet.
            if (!CheckFinalTransaction(this.chain, this.dateTimeProvider, context.Transaction, PowConsensusValidator.StandardLocktimeVerifyFlags))
            {
                context.State.Fail(MempoolErrors.NonFinal).Throw();
            }
        }
 private void CheckSigOps(MempoolValidationContext context)
 {
     // Check that the transaction doesn't have an excessive number of
     // sigops, making it impossible to mine. Since the coinbase transaction
     // 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 (context.SigOpsCost > this.consensusValidator.ConsensusOptions.MAX_BLOCK_SIGOPS_COST)
     {
         context.State.Fail(MempoolErrors.TooManySigops).Throw();
     }
 }
        private void CreateMempoolEntry(MempoolValidationContext context, long acceptTime)
        {
            // Only accept BIP68 sequence locked transactions that can be mined in the next
            // block; we don't want our mempool filled up with transactions that can't
            // be mined yet.
            // Must keep pool.cs for this unless we change CheckSequenceLocks to take a
            // CoinsViewCache instead of create its own
            if (!CheckSequenceLocks(this.chain.Tip, context, PowConsensusValidator.StandardLocktimeVerifyFlags, context.LockPoints))
            {
                context.State.Fail(MempoolErrors.NonBIP68Final).Throw();
            }

            // Check for non-standard pay-to-script-hash in inputs
            if (this.nodeArgs.RequireStandard && !this.AreInputsStandard(context.Transaction, context.View))
            {
                context.State.Invalid(MempoolErrors.NonstandardInputs).Throw();
            }

            // TODO: Implement Witness Code
            //// Check for non-standard witness in P2WSH
            //if (tx.HasWitness && requireStandard && !IsWitnessStandard(Trx, context.View))
            //	state.Invalid(new MempoolError(MempoolErrors.REJECT_NONSTANDARD, "bad-witness-nonstandard")).Throw();

            context.SigOpsCost = consensusValidator.GetTransactionSigOpCost(context.Transaction, context.View.Set,
                                                                            new ConsensusFlags {
                ScriptFlags = ScriptVerify.Standard
            });

            var nValueIn = context.View.GetValueIn(context.Transaction);

            context.ValueOut = context.Transaction.TotalOut;
            context.Fees     = nValueIn - context.ValueOut;
            // nModifiedFees includes any fee deltas from PrioritiseTransaction
            Money  nModifiedFees = context.Fees;
            double priorityDummy = 0;

            this.memPool.ApplyDeltas(context.TransactionHash, ref priorityDummy, ref nModifiedFees);
            context.ModifiedFees = nModifiedFees;

            Money  inChainInputValue = Money.Zero;
            double dPriority         = context.View.GetPriority(context.Transaction, this.chain.Height, inChainInputValue);

            // Keep track of transactions that spend a coinbase, which we re-scan
            // during reorgs to ensure COINBASE_MATURITY is still met.
            bool spendsCoinbase = context.View.SpendsCoinBase(context.Transaction);

            context.Entry = new TxMempoolEntry(context.Transaction, context.Fees, acceptTime, dPriority, this.chain.Height, inChainInputValue,
                                               spendsCoinbase, context.SigOpsCost, context.LockPoints, this.ConsensusOptions);
            context.EntrySize = (int)context.Entry.GetTxSize();
        }
        // Check for conflicts with in-memory transactions
        private void CheckConflicts(MempoolValidationContext context)
        {
            context.SetConflicts = new List <uint256>();
            foreach (var txin in context.Transaction.Inputs)
            {
                var itConflicting = this.memPool.MapNextTx.Find(f => f.OutPoint == txin.PrevOut);
                if (itConflicting != null)
                {
                    var ptxConflicting = itConflicting.Transaction;
                    if (!context.SetConflicts.Contains(ptxConflicting.GetHash()))
                    {
                        // Allow opt-out of transaction replacement by setting
                        // nSequence >= maxint-1 on all inputs.
                        //
                        // maxint-1 is picked to still allow use of nLockTime by
                        // non-replaceable transactions. All inputs rather than just one
                        // is for the sake of multi-party protocols, where we don't
                        // want a single party to be able to disable replacement.
                        //
                        // The opt-out ignores descendants as anyone relying on
                        // first-seen mempool behavior should be checking all
                        // unconfirmed ancestors anyway; doing otherwise is hopelessly
                        // insecure.
                        bool replacementOptOut = true;
                        if (this.nodeArgs.Mempool.EnableReplacement)
                        {
                            foreach (var txiner in ptxConflicting.Inputs)
                            {
                                if (txiner.Sequence < Sequence.Final - 1)
                                {
                                    replacementOptOut = false;
                                    break;
                                }
                            }
                        }

                        if (replacementOptOut)
                        {
                            context.State.Invalid(MempoolErrors.Conflict).Throw();
                        }

                        context.SetConflicts.Add(ptxConflicting.GetHash());
                    }
                }
            }
        }
        private void CheckAllInputs(MempoolValidationContext context)
        {
            var scriptVerifyFlags = ScriptVerify.Standard;

            if (!this.nodeArgs.RequireStandard)
            {
                // TODO: implement -promiscuousmempoolflags
                // scriptVerifyFlags = GetArg("-promiscuousmempoolflags", scriptVerifyFlags);
            }

            // Check against previous transactions
            // This is done last to help prevent CPU exhaustion denial-of-service attacks.
            PrecomputedTransactionData txdata = new PrecomputedTransactionData(context.Transaction);

            if (!CheckInputs(context, scriptVerifyFlags, txdata))
            {
                // TODO: Implement Witness Code
                //// SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
                //// need to turn both off, and compare against just turning off CLEANSTACK
                //// to see if the failure is specifically due to witness validation.
                //if (!tx.HasWitness() && CheckInputs(Trx, state, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, txdata) &&
                //	!CheckInputs(tx, state, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, txdata))
                //{
                //	// Only the witness is missing, so the transaction itself may be fine.
                //	state.SetCorruptionPossible();
                //}

                context.State.Fail(new MempoolError()).Throw();
            }

            // Check again against just the consensus-critical mandatory script
            // verification flags, in case of bugs in the standard flags that cause
            // transactions to pass as valid when they're actually invalid. For
            // instance the STRICTENC flag was incorrectly allowing certain
            // CHECKSIG NOT scripts to pass, even though they were invalid.
            //
            // There is a similar check in CreateNewBlock() to prevent creating
            // invalid blocks, however allowing such transactions into the mempool
            // can be exploited as a DoS attack.
            if (!CheckInputs(context, ScriptVerify.P2SH, txdata))
            {
                context.State.Fail(new MempoolError(),
                                   $"CheckInputs: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags {context.TransactionHash}").Throw();
            }
        }
        private void CheckFee(MempoolValidationContext context)
        {
            Money mempoolRejectFee = this.memPool.GetMinFee(this.nodeArgs.Mempool.MaxMempool * 1000000).GetFee(context.EntrySize);

            if (mempoolRejectFee > 0 && context.ModifiedFees < mempoolRejectFee)
            {
                context.State.Fail(MempoolErrors.MinFeeNotMet, $" {context.Fees} < {mempoolRejectFee}").Throw();
            }
            else if (nodeArgs.Mempool.RelayPriority && context.ModifiedFees < MinRelayTxFee.GetFee(context.EntrySize) &&
                     !TxMempool.AllowFree(context.Entry.GetPriority(this.chain.Height + 1)))
            {
                // Require that free transactions have sufficient priority to be mined in the next block.
                context.State.Fail(MempoolErrors.InsufficientPriority).Throw();
            }

            if (context.State.AbsurdFee > 0 && context.Fees > context.State.AbsurdFee)
            {
                context.State.Invalid(MempoolErrors.AbsurdlyHighFee, $"{context.Fees} > {context.State.AbsurdFee}").Throw();
            }
        }
        // Check if transaction will be BIP 68 final in the next block to be created.
        // Simulates calling SequenceLocks() with data from the tip of the current active chain.
        // Optionally stores in LockPoints the resulting height and time calculated and the hash
        // of the block needed for calculation or skips the calculation and uses the LockPoints
        // passed in for evaluation.
        // The LockPoints should not be considered valid if CheckSequenceLocks returns false.
        // See consensus/consensus.h for flag definitions.
        public static bool CheckSequenceLocks(ChainedBlock tip, MempoolValidationContext context, Transaction.LockTimeFlags flags, LockPoints lp = null,
                                              bool useExistingLockPoints = false)
        {
            var dummyBlock = new Block {
                Header = { HashPrevBlock = tip.HashBlock }
            };
            ChainedBlock index = new ChainedBlock(dummyBlock.Header, dummyBlock.GetHash(), tip);

            // CheckSequenceLocks() uses chainActive.Height()+1 to evaluate
            // height based locks because when SequenceLocks() is called within
            // ConnectBlock(), the height of the block *being*
            // evaluated is what is used.
            // Thus if we want to know if a transaction can be part of the
            // *next* block, we need to use one more than chainActive.Height()

            SequenceLock lockPair;

            if (useExistingLockPoints)
            {
                Guard.Assert(lp != null);
                lockPair = new SequenceLock(lp.Height, lp.Time);
            }
            else
            {
                // pcoinsTip contains the UTXO set for chainActive.Tip()
                List <int> prevheights = new List <int>();
                foreach (var txin in context.Transaction.Inputs)
                {
                    var coins = context.View.GetCoins(txin.PrevOut.Hash);
                    if (coins == null)
                    {
                        return(false);
                    }

                    if (coins.Height == TxMempool.MempoolHeight)
                    {
                        // Assume all mempool transaction confirm in the next block
                        prevheights.Add(tip.Height + 1);
                    }
                    else
                    {
                        prevheights.Add((int)coins.Height);
                    }
                }
                lockPair = context.Transaction.CalculateSequenceLocks(prevheights.ToArray(), index, flags);

                if (lp != null)
                {
                    lp.Height = lockPair.MinHeight;
                    lp.Time   = lockPair.MinTime.ToUnixTimeMilliseconds();
                    // Also store the hash of the block with the highest height of
                    // all the blocks which have sequence locked prevouts.
                    // This hash needs to still be on the chain
                    // for these LockPoint calculations to be valid
                    // Note: It is impossible to correctly calculate a maxInputBlock
                    // if any of the sequence locked inputs depend on unconfirmed txs,
                    // except in the special case where the relative lock time/height
                    // is 0, which is equivalent to no sequence lock. Since we assume
                    // input height of tip+1 for mempool txs and test the resulting
                    // lockPair from CalculateSequenceLocks against tip+1.  We know
                    // EvaluateSequenceLocks will fail if there was a non-zero sequence
                    // lock on a mempool input, so we can use the return value of
                    // CheckSequenceLocks to indicate the LockPoints validity
                    int maxInputHeight = 0;
                    foreach (var height in prevheights)
                    {
                        // Can ignore mempool inputs since we'll fail if they had non-zero locks
                        if (height != tip.Height + 1)
                        {
                            maxInputHeight = Math.Max(maxInputHeight, height);
                        }
                    }

                    lp.MaxInputBlock = tip.GetAncestor(maxInputHeight);
                }
            }

            return(lockPair.Evaluate(index));
        }
        // Check whether all inputs of this transaction are valid (no double spends, scripts & sigs, amounts)
        // This does not modify the UTXO set. If pvChecks is not NULL, script checks are pushed onto it
        // instead of being performed inline.
        private bool CheckInputs(MempoolValidationContext context, ScriptVerify scriptVerify,
                                 PrecomputedTransactionData txData)
        {
            var tx = context.Transaction;

            if (!context.Transaction.IsCoinBase)
            {
                this.consensusValidator.CheckInputs(context.Transaction, context.View.Set, this.chain.Height + 1);

                for (int iInput = 0; iInput < tx.Inputs.Count; iInput++)
                {
                    var input    = tx.Inputs[iInput];
                    int iiIntput = iInput;
                    var txout    = context.View.GetOutputFor(input);

                    if (this.consensusValidator.UseConsensusLib)
                    {
                        Script.BitcoinConsensusError error;
                        return(Script.VerifyScriptConsensus(txout.ScriptPubKey, tx, (uint)iiIntput, scriptVerify, out error));
                    }
                    else
                    {
                        var checker = new TransactionChecker(tx, iiIntput, txout.Value, txData);
                        var ctx     = new ScriptEvaluationContext();
                        ctx.ScriptVerify = scriptVerify;
                        if (ctx.VerifyScript(input.ScriptSig, txout.ScriptPubKey, checker))
                        {
                            return(true);
                        }
                        else
                        {
                            //TODO:

                            //if (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS)
                            //{
                            //	// Check whether the failure was caused by a
                            //	// non-mandatory script verification check, such as
                            //	// non-standard DER encodings or non-null dummy
                            //	// arguments; if so, don't trigger DoS protection to
                            //	// avoid splitting the network between upgraded and
                            //	// non-upgraded nodes.
                            //	CScriptCheck check2(*coins, tx, i,
                            //			flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore, &txdata);
                            //	if (check2())
                            //		return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
                            //}
                            //// Failures of other flags indicate a transaction that is
                            //// invalid in new blocks, e.g. a invalid P2SH. We DoS ban
                            //// such nodes as they are not following the protocol. That
                            //// said during an upgrade careful thought should be taken
                            //// as to the correct behavior - we may want to continue
                            //// peering with non-upgraded nodes even after soft-fork
                            //// super-majority signaling has occurred.
                            context.State.Fail(MempoolErrors.MandatoryScriptVerifyFlagFailed, ctx.Error.ToString()).Throw();
                        }
                    }
                }
            }

            return(true);
        }
        private void CheckReplacment(MempoolValidationContext context)
        {
            // Check if it's economically rational to mine this transaction rather
            // than the ones it replaces.
            context.ConflictingFees  = 0;
            context.ConflictingSize  = 0;
            context.ConflictingCount = 0;
            context.AllConflicting   = new TxMempool.SetEntries();

            // If we don't hold the lock allConflicting might be incomplete; the
            // subsequent RemoveStaged() and addUnchecked() calls don't guarantee
            // mempool consistency for us.
            //LOCK(pool.cs);
            if (context.SetConflicts.Any())
            {
                FeeRate              newFeeRate            = new FeeRate(context.ModifiedFees, context.EntrySize);
                List <uint256>       setConflictsParents   = new List <uint256>();
                const int            maxDescendantsToVisit = 100;
                TxMempool.SetEntries setIterConflicting    = new TxMempool.SetEntries();
                foreach (var hashConflicting in context.SetConflicts)
                {
                    var mi = this.memPool.MapTx.TryGet(hashConflicting);
                    if (mi == null)
                    {
                        continue;
                    }

                    // Save these to avoid repeated lookups
                    setIterConflicting.Add(mi);

                    // Don't allow the replacement to reduce the feerate of the
                    // mempool.
                    //
                    // We usually don't want to accept replacements with lower
                    // feerates than what they replaced as that would lower the
                    // feerate of the next block. Requiring that the feerate always
                    // be increased is also an easy-to-reason about way to prevent
                    // DoS attacks via replacements.
                    //
                    // The mining code doesn't (currently) take children into
                    // account (CPFP) so we only consider the feerates of
                    // transactions being directly replaced, not their indirect
                    // descendants. While that does mean high feerate children are
                    // ignored when deciding whether or not to replace, we do
                    // require the replacement to pay more overall fees too,
                    // mitigating most cases.
                    FeeRate oldFeeRate = new FeeRate(mi.ModifiedFee, (int)mi.GetTxSize());
                    if (newFeeRate <= oldFeeRate)
                    {
                        context.State.Fail(MempoolErrors.InsufficientFee,
                                           $"rejecting replacement {context.TransactionHash}; new feerate {newFeeRate} <= old feerate {oldFeeRate}").Throw();
                    }

                    foreach (var txin in mi.Transaction.Inputs)
                    {
                        setConflictsParents.Add(txin.PrevOut.Hash);
                    }

                    context.ConflictingCount += mi.CountWithDescendants;
                }
                // This potentially overestimates the number of actual descendants
                // but we just want to be conservative to avoid doing too much
                // work.
                if (context.ConflictingCount <= maxDescendantsToVisit)
                {
                    // If not too many to replace, then calculate the set of
                    // transactions that would have to be evicted
                    foreach (var it in setIterConflicting)
                    {
                        this.memPool.CalculateDescendants(it, context.AllConflicting);
                    }
                    foreach (var it in context.AllConflicting)
                    {
                        context.ConflictingFees += it.ModifiedFee;
                        context.ConflictingSize += it.GetTxSize();
                    }
                }
                else
                {
                    context.State.Fail(MempoolErrors.TooManyPotentialReplacements,
                                       $"rejecting replacement {context.TransactionHash}; too many potential replacements ({context.ConflictingCount} > {maxDescendantsToVisit})").Throw();
                }

                for (int j = 0; j < context.Transaction.Inputs.Count; j++)
                {
                    // We don't want to accept replacements that require low
                    // feerate junk to be mined first. Ideally we'd keep track of
                    // the ancestor feerates and make the decision based on that,
                    // but for now requiring all new inputs to be confirmed works.
                    if (!setConflictsParents.Contains(context.Transaction.Inputs[j].PrevOut.Hash))
                    {
                        // Rather than check the UTXO set - potentially expensive -
                        // it's cheaper to just check if the new input refers to a
                        // tx that's in the mempool.
                        if (this.memPool.MapTx.ContainsKey(context.Transaction.Inputs[j].PrevOut.Hash))
                        {
                            context.State.Fail(MempoolErrors.ReplacementAddsUnconfirmed,
                                               $"replacement {context.TransactionHash} adds unconfirmed input, idx {j}").Throw();
                        }
                    }
                }

                // The replacement must pay greater fees than the transactions it
                // replaces - if we did the bandwidth used by those conflicting
                // transactions would not be paid for.
                if (context.ModifiedFees < context.ConflictingFees)
                {
                    context.State.Fail(MempoolErrors.Insufficientfee,
                                       $"rejecting replacement {context.TransactionHash}, less fees than conflicting txs; {context.ModifiedFees} < {context.ConflictingFees}").Throw();
                }

                // Finally in addition to paying more fees than the conflicts the
                // new transaction must pay for its own bandwidth.
                Money nDeltaFees = context.ModifiedFees - context.ConflictingFees;
                if (nDeltaFees < MinRelayTxFee.GetFee(context.EntrySize))
                {
                    context.State.Fail(MempoolErrors.Insufficientfee,
                                       $"rejecting replacement {context.TransactionHash}, not enough additional fees to relay; {nDeltaFees} < {MinRelayTxFee.GetFee(context.EntrySize)}").Throw();
                }
            }
        }
        private void CheckStandardTransaction(MempoolValidationContext context, bool witnessEnabled)
        {
            // TODO: Implement Witness Code

            var tx = context.Transaction;

            if (tx.Version > this.consensusValidator.ConsensusOptions.MAX_STANDARD_VERSION || tx.Version < 1)
            {
                context.State.Fail(MempoolErrors.Version).Throw();
            }

            // Extremely large transactions with lots of inputs can cost the network
            // almost as much to process as they cost the sender in fees, because
            // computing signature hashes is O(ninputs*txsize). Limiting transactions
            // to MAX_STANDARD_TX_WEIGHT mitigates CPU exhaustion attacks.
            var sz = GetTransactionWeight(tx, this.consensusValidator.ConsensusOptions);

            if (sz >= this.consensusValidator.ConsensusOptions.MAX_STANDARD_TX_WEIGHT)
            {
                context.State.Fail(MempoolErrors.TxSize).Throw();
            }

            foreach (var txin in tx.Inputs)
            {
                // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
                // keys (remember the 520 byte limit on redeemScript size). That works
                // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)+3=1627
                // bytes of scriptSig, which we round off to 1650 bytes for some minor
                // future-proofing. That's also enough to spend a 20-of-20
                // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
                // considered standard.
                if (txin.ScriptSig.Length > 1650)
                {
                    context.State.Fail(MempoolErrors.ScriptsigSize).Throw();
                }

                if (!txin.ScriptSig.IsPushOnly)
                {
                    context.State.Fail(MempoolErrors.ScriptsigNotPushonly).Throw();
                }
            }

            int dataOut = 0;

            foreach (var txout in tx.Outputs)
            {
                var script = StandardScripts.GetTemplateFromScriptPubKey(txout.ScriptPubKey);
                if (script == null)                 //!::IsStandard(txout.scriptPubKey, whichType, witnessEnabled))
                {
                    context.State.Fail(MempoolErrors.Scriptpubkey).Throw();
                }

                if (script.Type == TxOutType.TX_NULL_DATA)
                {
                    dataOut++;
                }
                // TODO: fIsBareMultisigStd
                //else if ((script == PayToMultiSigTemplate.Instance))  (!fIsBareMultisigStd))
                //{
                //	context.State.Fail(new MempoolError(MempoolErrors.RejectNonstandard, "bare-multisig")).Throw();
                //}
                else if (txout.IsDust(MinRelayTxFee))
                {
                    context.State.Fail(MempoolErrors.Dust).Throw();
                }
            }

            // only one OP_RETURN txout is permitted
            if (dataOut > 1)
            {
                context.State.Fail(MempoolErrors.MultiOpReturn).Throw();
            }
        }
        private async Task AcceptToMemoryPoolWorker(MempoolValidationState state, Transaction tx, List <uint256> vHashTxnToUncache)
        {
            var context = new MempoolValidationContext(tx, state);

            this.PreMempoolChecks(context);

            // create the MemPoolCoinView and load relevant utxoset
            context.View = new MempoolCoinView(this.coinView, this.memPool, this.mempoolScheduler, this);
            await context.View.LoadView(context.Transaction).ConfigureAwait(false);

            // adding to the mem pool can only be done sequentially
            // use the sequential scheduler for that.
            await this.mempoolScheduler.WriteAsync(() =>
            {
                // is it already in the memory pool?
                if (this.memPool.Exists(context.TransactionHash))
                {
                    state.Invalid(MempoolErrors.InPool).Throw();
                }

                // Check for conflicts with in-memory transactions
                this.CheckConflicts(context);

                this.CheckMempoolCoinView(context);

                this.CreateMempoolEntry(context, state.AcceptTime);
                this.CheckSigOps(context);
                this.CheckFee(context);

                this.CheckRateLimit(context, state.LimitFree);

                this.CheckAncestors(context);
                this.CheckReplacment(context);
                this.CheckAllInputs(context);

                // Remove conflicting transactions from the mempool
                foreach (var it in context.AllConflicting)
                {
                    Logging.Logs.Mempool.LogInformation(
                        $"replacing tx {it.TransactionHash} with {context.TransactionHash} for {context.ModifiedFees - context.ConflictingFees} BTC additional fees, {context.EntrySize - context.ConflictingSize} delta bytes");
                }

                this.memPool.RemoveStaged(context.AllConflicting, false);

                // This transaction should only count for fee estimation if
                // the node is not behind and it is not dependent on any other
                // transactions in the mempool
                bool validForFeeEstimation = IsCurrentForFeeEstimation() && this.memPool.HasNoInputsOf(tx);

                // Store transaction in memory
                this.memPool.AddUnchecked(context.TransactionHash, context.Entry, context.SetAncestors, validForFeeEstimation);

                // trim mempool and check if tx was trimmed
                if (!state.OverrideMempoolLimit)
                {
                    LimitMempoolSize(this.nodeArgs.Mempool.MaxMempool * 1000000, this.nodeArgs.Mempool.MempoolExpiry * 60 * 60);

                    if (!this.memPool.Exists(context.TransactionHash))
                    {
                        state.Fail(MempoolErrors.Full).Throw();
                    }
                }

                // do this here inside the exclusive scheduler for better accuracy
                // and to avoid springing more concurrent tasks later
                state.MempoolSize        = this.memPool.Size;
                state.MempoolDynamicSize = this.memPool.DynamicMemoryUsage();

                this.PerformanceCounter.SetMempoolSize(state.MempoolSize);
                this.PerformanceCounter.SetMempoolDynamicSize(state.MempoolDynamicSize);
                this.PerformanceCounter.AddHitCount(1);
            });

            //	GetMainSignals().SyncTransaction(tx, NULL, CMainSignals::SYNC_TRANSACTION_NOT_IN_BLOCK);
        }