transaction.cpp

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// Copyright (c) 2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <consensus/validation.h>
#include <net.h>
#include <net_processing.h>
#include <node/context.h>
#include <validation.h>
#include <validationinterface.h>
#include <node/transaction.h>

#include <future>

static TransactionError HandleATMPError(const TxValidationState& state, std::string& err_string_out)
{
    err_string_out = state.ToString();
    if (state.IsInvalid()) {
        if (state.GetResult() == TxValidationResult::TX_MISSING_INPUTS) {
            return TransactionError::MISSING_INPUTS;
        }
        return TransactionError::MEMPOOL_REJECTED;
    } else {
        return TransactionError::MEMPOOL_ERROR;
    }
}

TransactionError BroadcastTransaction(NodeContext& node, const CTransactionRef tx, std::string& err_string, const CAmount& max_tx_fee, bool relay, bool wait_callback)
{
    // BroadcastTransaction can be called by either sendrawtransaction RPC or the wallet.
    // chainman, mempool and peerman are initialized before the RPC server and wallet are started
    // and reset after the RPC sever and wallet are stopped.
    assert(node.chainman);
    assert(node.mempool);
    assert(node.peerman);

    std::promise<void> promise;
    uint256 txid = tx->GetHash();
    uint256 wtxid = tx->GetWitnessHash();
    bool callback_set = false;

    {
        LOCK(cs_main);

        // If the transaction is already confirmed in the chain, don't do anything
        // and return early.
        CCoinsViewCache &view = node.chainman->ActiveChainstate().CoinsTip();
        for (size_t o = 0; o < tx->vout.size(); o++) {
            const Coin& existingCoin = view.AccessCoin(COutPoint(txid, o));
            // IsSpent doesn't mean the coin is spent, it means the output doesn't exist.
            // So if the output does exist, then this transaction exists in the chain.
            if (!existingCoin.IsSpent()) return TransactionError::ALREADY_IN_CHAIN;
        }

        if (auto mempool_tx = node.mempool->get(txid); mempool_tx) {
            // There's already a transaction in the mempool with this txid. Don't
            // try to submit this transaction to the mempool (since it'll be
            // rejected as a TX_CONFLICT), but do attempt to reannounce the mempool
            // transaction if relay=true.
            //
            // The mempool transaction may have the same or different witness (and
            // wtxid) as this transaction. Use the mempool's wtxid for reannouncement.
            wtxid = mempool_tx->GetWitnessHash();
        } else {
            // Transaction is not already in the mempool.
            if (max_tx_fee > 0) {
                // First, call ATMP with test_accept and check the fee. If ATMP
                // fails here, return error immediately.
                const MempoolAcceptResult result = AcceptToMemoryPool(node.chainman->ActiveChainstate(), *node.mempool, tx, false /* bypass_limits */,
                                                                      true /* test_accept */);
                if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
                    return HandleATMPError(result.m_state, err_string);
                } else if (result.m_base_fees.value() > max_tx_fee) {
                    return TransactionError::MAX_FEE_EXCEEDED;
                }
            }
            // Try to submit the transaction to the mempool.
            const MempoolAcceptResult result = AcceptToMemoryPool(node.chainman->ActiveChainstate(), *node.mempool, tx, false /* bypass_limits */,
                                                                  false /* test_accept */);
            if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
                return HandleATMPError(result.m_state, err_string);
            }

            // Transaction was accepted to the mempool.

            if (relay) {
                // the mempool tracks locally submitted transactions to make a
                // best-effort of initial broadcast
                node.mempool->AddUnbroadcastTx(txid);
            }

            if (wait_callback) {
                // For transactions broadcast from outside the wallet, make sure
                // that the wallet has been notified of the transaction before
                // continuing.
                //
                // This prevents a race where a user might call sendrawtransaction
                // with a transaction to/from their wallet, immediately call some
                // wallet RPC, and get a stale result because callbacks have not
                // yet been processed.
                CallFunctionInValidationInterfaceQueue([&promise] {
                    promise.set_value();
                });
                callback_set = true;
            }
        }
    } // cs_main

    if (callback_set) {
        // Wait until Validation Interface clients have been notified of the
        // transaction entering the mempool.
        promise.get_future().wait();
    }

    if (relay) {
        node.peerman->RelayTransaction(txid, wtxid);
    }

    return TransactionError::OK;
}