Method ThreadDNSAddressSeed

src/net.cpp:2284–2422

}

void CConnman::ThreadDNSAddressSeed()
{
    int outbound_connection_count = 0;

    if (!gArgs.GetArgs("-seednode").empty()) {
        auto start = NodeClock::now();
        constexpr std::chrono::seconds SEEDNODE_TIMEOUT = 30s;
        LogInfo("-seednode enabled. Trying the provided seeds for %d seconds before defaulting to the dnsseeds.\n", SEEDNODE_TIMEOUT.count());
        while (!m_interrupt_net->interrupted()) {
            if (!m_interrupt_net->sleep_for(500ms)) {
                return;
            }

            // Abort if we have spent enough time without reaching our target.
            // Giving seed nodes 30 seconds so this does not become a race against fixedseeds (which triggers after 1 min)
            if (NodeClock::now() > start + SEEDNODE_TIMEOUT) {
                LogInfo("Couldn't connect to enough peers via seed nodes. Handing fetch logic to the DNS seeds.\n");
                break;
            }

            outbound_connection_count = GetFullOutboundConnCount();
            if (outbound_connection_count >= SEED_OUTBOUND_CONNECTION_THRESHOLD) {
                LogInfo("P2P peers available. Finished fetching data from seed nodes.\n");
                break;
            }
        }
    }

    FastRandomContext rng;
    std::vector<std::string> seeds = m_params.DNSSeeds();
    std::shuffle(seeds.begin(), seeds.end(), rng);
    int seeds_right_now = 0; // Number of seeds left before testing if we have enough connections

    if (gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED)) {
        // When -forcednsseed is provided, query all.
        seeds_right_now = seeds.size();
    } else if (addrman.get().Size() == 0) {
        // If we have no known peers, query all.
        // This will occur on the first run, or if peers.dat has been
        // deleted.
        seeds_right_now = seeds.size();
    }

    // Proceed with dnsseeds if seednodes hasn't reached the target or if forcednsseed is set
    if (outbound_connection_count < SEED_OUTBOUND_CONNECTION_THRESHOLD || seeds_right_now) {
        // goal: only query DNS seed if address need is acute
        // * If we have a reasonable number of peers in addrman, spend
        //   some time trying them first. This improves user privacy by
        //   creating fewer identifying DNS requests, reduces trust by
        //   giving seeds less influence on the network topology, and
        //   reduces traffic to the seeds.
        // * When querying DNS seeds query a few at once, this ensures
        //   that we don't give DNS seeds the ability to eclipse nodes
        //   that query them.
        // * If we continue having problems, eventually query all the
        //   DNS seeds, and if that fails too, also try the fixed seeds.
        //   (done in ThreadOpenConnections)
        int found = 0;