Method ProcessOrphanTx

src/net_processing.cpp:2330–2397

* Reconsider orphan transactions after a parent has been accepted to the mempool. * * @param[in,out] orphan_work_set The set of orphan transactions to reconsider. Generally only one * orphan will be reconsidered on each call of this function. This set * may be added to if accepting an orphan causes its children to be *

 *                                  reconsidered.
 */
void PeerManagerImpl::ProcessOrphanTx(std::set<uint256>& orphan_work_set)
{
    AssertLockHeld(cs_main);
    AssertLockHeld(g_cs_orphans);

    while (!orphan_work_set.empty()) {
        const uint256 orphanHash = *orphan_work_set.begin();
        orphan_work_set.erase(orphan_work_set.begin());

        const auto [porphanTx, from_peer] = m_orphanage.GetTx(orphanHash);
        if (porphanTx == nullptr) continue;

        const MempoolAcceptResult result = m_chainman.ProcessTransaction(porphanTx);
        const TxValidationState& state = result.m_state;

        if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
            LogPrint(BCLog::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
            _RelayTransaction(orphanHash, porphanTx->GetWitnessHash());
            m_orphanage.AddChildrenToWorkSet(*porphanTx, orphan_work_set);
            m_orphanage.EraseTx(orphanHash);
            for (const CTransactionRef& removedTx : result.m_replaced_transactions.value()) {
                AddToCompactExtraTransactions(removedTx);
            }
            break;
        } else if (state.GetResult() != TxValidationResult::TX_MISSING_INPUTS) {
            if (state.IsInvalid()) {
                LogPrint(BCLog::MEMPOOL, "   invalid orphan tx %s from peer=%d. %s\n",
                    orphanHash.ToString(),
                    from_peer,
                    state.ToString());
            }
            // Has inputs but not accepted to mempool
            // Probably non-standard or insufficient fee
            LogPrint(BCLog::MEMPOOL, "   removed orphan tx %s\n", orphanHash.ToString());
            if (state.GetResult() != TxValidationResult::TX_WITNESS_STRIPPED) {
                // We can add the wtxid of this transaction to our reject filter.
                // Do not add txids of witness transactions or witness-stripped
                // transactions to the filter, as they can have been malleated;
                // adding such txids to the reject filter would potentially
                // interfere with relay of valid transactions from peers that
                // do not support wtxid-based relay. See
                // https://github.com/bitcoin/bitcoin/issues/8279 for details.
                // We can remove this restriction (and always add wtxids to
                // the filter even for witness stripped transactions) once
                // wtxid-based relay is broadly deployed.
                // See also comments in https://github.com/bitcoin/bitcoin/pull/18044#discussion_r443419034
                // for concerns around weakening security of unupgraded nodes
                // if we start doing this too early.
                m_recent_rejects.insert(porphanTx->GetWitnessHash());
                // If the transaction failed for TX_INPUTS_NOT_STANDARD,
                // then we know that the witness was irrelevant to the policy
                // failure, since this check depends only on the txid
                // (the scriptPubKey being spent is covered by the txid).
                // Add the txid to the reject filter to prevent repeated
                // processing of this transaction in the event that child
                // transactions are later received (resulting in
                // parent-fetching by txid via the orphan-handling logic).
                if (state.GetResult() == TxValidationResult::TX_INPUTS_NOT_STANDARD && porphanTx->GetWitnessHash() != porphanTx->GetHash()) {