Method MaybeAddOrphanResolutionCandidate

src/node/txdownloadman_impl.cpp:226–262

}

bool TxDownloadManagerImpl::MaybeAddOrphanResolutionCandidate(const std::vector<Txid>& unique_parents, const Wtxid& wtxid, NodeId nodeid, std::chrono::microseconds now)
{
    auto it_peer = m_peer_info.find(nodeid);
    if (it_peer == m_peer_info.end()) return false;
    if (m_orphanage->HaveTxFromPeer(wtxid, nodeid)) return false;

    const auto& peer_entry = m_peer_info.at(nodeid);
    const auto& info = peer_entry.m_connection_info;

    // TODO: add delays and limits based on the amount of orphan resolution we are already doing
    // with this peer, how much they are using the orphanage, etc.
    if (!info.m_relay_permissions) {
        // This mirrors the delaying and dropping behavior in AddTxAnnouncement in order to preserve
        // existing behavior: drop if we are tracking too many invs for this peer already. Each
        // orphan resolution involves at least 1 transaction request which may or may not be
        // currently tracked in m_txrequest, so we include that in the count.
        if (m_txrequest.Count(nodeid) + unique_parents.size() > MAX_PEER_TX_ANNOUNCEMENTS) return false;
    }

    std::chrono::seconds delay{0s};
    if (!info.m_preferred) delay += NONPREF_PEER_TX_DELAY;
    // The orphan wtxid is used, but resolution entails requesting the parents by txid. Sometimes
    // parent and child are announced and thus requested around the same time, and we happen to
    // receive child sooner. Waiting a few seconds may allow us to cancel the orphan resolution
    // request if the parent arrives in that time.
    if (m_num_wtxid_peers > 0) delay += TXID_RELAY_DELAY;
    const bool overloaded = !info.m_relay_permissions && m_txrequest.CountInFlight(nodeid) >= MAX_PEER_TX_REQUEST_IN_FLIGHT;
    if (overloaded) delay += OVERLOADED_PEER_TX_DELAY;

    // Treat finding orphan resolution candidate as equivalent to the peer announcing all missing parents.
    // In the future, orphan resolution may include more explicit steps
    for (const auto& parent_txid : unique_parents) {
        m_txrequest.ReceivedInv(nodeid, parent_txid, info.m_preferred, now + delay);
    }
    LogDebug(BCLog::TXPACKAGES, "added peer=%d as a candidate for resolving orphan %s\n", nodeid, wtxid.ToString());
    return true;
}

std::vector<GenTxid> TxDownloadManagerImpl::GetRequestsToSend(NodeId nodeid, std::chrono::microseconds current_time)
{