Method AcceptPackage

src/validation.cpp:1344–1447

}

PackageMempoolAcceptResult MemPoolAccept::AcceptPackage(const Package& package, ATMPArgs& args)
{
    AssertLockHeld(cs_main);
    PackageValidationState package_state;

    // Check that the package is well-formed. If it isn't, we won't try to validate any of the
    // transactions and thus won't return any MempoolAcceptResults, just a package-wide error.

    // Context-free package checks.
    if (!CheckPackage(package, package_state)) return PackageMempoolAcceptResult(package_state, {});

    // All transactions in the package must be a parent of the last transaction. This is just an
    // opportunity for us to fail fast on a context-free check without taking the mempool lock.
    if (!IsChildWithParents(package)) {
        package_state.Invalid(PackageValidationResult::PCKG_POLICY, "package-not-child-with-parents");
        return PackageMempoolAcceptResult(package_state, {});
    }

    // IsChildWithParents() guarantees the package is > 1 transactions.
    assert(package.size() > 1);
    // The package must be 1 child with all of its unconfirmed parents. The package is expected to
    // be sorted, so the last transaction is the child.
    const auto& child = package.back();
    std::unordered_set<uint256, SaltedTxidHasher> unconfirmed_parent_txids;
    std::transform(package.cbegin(), package.cend() - 1,
                   std::inserter(unconfirmed_parent_txids, unconfirmed_parent_txids.end()),
                   [](const auto& tx) { return tx->GetHash(); });

    // All child inputs must refer to a preceding package transaction or a confirmed UTXO. The only
    // way to verify this is to look up the child's inputs in our current coins view (not including
    // mempool), and enforce that all parents not present in the package be available at chain tip.
    // Since this check can bring new coins into the coins cache, keep track of these coins and
    // uncache them if we don't end up submitting this package to the mempool.
    const CCoinsViewCache& coins_tip_cache = m_active_chainstate.CoinsTip();
    for (const auto& input : child->vin) {
        if (!coins_tip_cache.HaveCoinInCache(input.prevout)) {
            args.m_coins_to_uncache.push_back(input.prevout);
        }
    }
    // Using the MemPoolAccept m_view cache allows us to look up these same coins faster later.
    // This should be connecting directly to CoinsTip, not to m_viewmempool, because we specifically
    // require inputs to be confirmed if they aren't in the package.
    m_view.SetBackend(m_active_chainstate.CoinsTip());
    const auto package_or_confirmed = [this, &unconfirmed_parent_txids](const auto& input) {
         return unconfirmed_parent_txids.count(input.prevout.hash) > 0 || m_view.HaveCoin(input.prevout);
    };
    if (!std::all_of(child->vin.cbegin(), child->vin.cend(), package_or_confirmed)) {
        package_state.Invalid(PackageValidationResult::PCKG_POLICY, "package-not-child-with-unconfirmed-parents");
        return PackageMempoolAcceptResult(package_state, {});
    }
    // Protect against bugs where we pull more inputs from disk that miss being added to
    // coins_to_uncache. The backend will be connected again when needed in PreChecks.
    m_view.SetBackend(m_dummy);

    LOCK(m_pool.cs);
    std::map<const uint256, const MempoolAcceptResult> results;
    // Node operators are free to set their mempool policies however they please, nodes may receive
    // transactions in different orders, and malicious counterparties may try to take advantage of