transaction.cpp

// Copyright (c) 2010 Satoshi Nakamoto
// Copyright (c) 2009-2018 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 <txmempool.h>
#include <util/validation.h>
#include <validation.h>
#include <validationinterface.h>
#include <node/transaction.h>

#include <future>

TransactionError BroadcastTransaction(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 wallet RPCs.
    // g_connman is assigned both before chain clients and before RPC server is accepting calls,
    // and reset after chain clients and RPC sever are stopped. g_connman should never be null here.
    assert(g_connman);
    std::promise<void> promise;
    uint256 hashTx = tx->GetHash();
    bool callback_set = false;

    { // cs_main scope
    LOCK(cs_main);
    // If the transaction is already confirmed in the chain, don't do anything
    // and return early.
    CCoinsViewCache &view = ::ChainstateActive().CoinsTip();
    for (size_t o = 0; o < tx->vout.size(); o++) {
        const Coin& existingCoin = view.AccessCoin(COutPoint(hashTx, o));
        // IsSpent doesnt mean the coin is spent, it means the output doesnt' exist.
        // So if the output does exist, then this transaction exists in the chain.
        if (!existingCoin.IsSpent()) return TransactionError::ALREADY_IN_CHAIN;
    }
    if (!mempool.exists(hashTx)) {
        // Transaction is not already in the mempool. Submit it.
        CValidationState state;
        bool fMissingInputs;
        if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
                nullptr /* plTxnReplaced */, false /* bypass_limits */, max_tx_fee)) {
            if (state.IsInvalid()) {
                err_string = FormatStateMessage(state);
                return TransactionError::MEMPOOL_REJECTED;
            } else {
                if (fMissingInputs) {
                    return TransactionError::MISSING_INPUTS;
                }
                err_string = FormatStateMessage(state);
                return TransactionError::MEMPOOL_ERROR;
            }
        }

        // Transaction was accepted to the mempool.

        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) {
        // the mempool explicitly keeps track of wallet txns to ensure successful initial broadcast
        mempool.setUnbroadcastTxIDs.insert(hashTx);

        RelayTransaction(hashTx, *g_connman);
    }

    return TransactionError::OK;
}