diff --git a/src/net.cpp b/src/net.cpp index 18fe95e675..4eb26b095e 100644 --- a/src/net.cpp +++ b/src/net.cpp @@ -51,6 +51,12 @@ static constexpr int DUMP_PEERS_INTERVAL = 15 * 60; /** Number of DNS seeds to query when the number of connections is low. */ static constexpr int DNSSEEDS_TO_QUERY_AT_ONCE = 3; +/** How long to delay before querying DNS seeds + */ +static constexpr std::chrono::seconds DNSSEEDS_DELAY_FEW_PEERS{11}; // 11sec +static constexpr std::chrono::seconds DNSSEEDS_DELAY_MANY_PEERS{300}; // 5min +static constexpr int DNSSEEDS_DELAY_PEER_THRESHOLD = 1000; // "many" vs "few" peers -- you should only get this many if you've been on the live network + // We add a random period time (0 to 1 seconds) to feeler connections to prevent synchronization. #define FEELER_SLEEP_WINDOW 1 @@ -1573,31 +1579,61 @@ void CConnman::ThreadDNSAddressSeed() if (gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED)) { // When -forcednsseed is provided, query all. seeds_right_now = seeds.size(); + } else if (addrman.size() == 0) { + // If we have no known peers, query all. + seeds_right_now = seeds.size(); } - for (const std::string& seed : seeds) { - // goal: only query DNS seed if address need is acute - // Avoiding DNS seeds when we don't need them 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. - if (addrman.size() > 0 && seeds_right_now == 0) { - if (!interruptNet.sleep_for(std::chrono::seconds(11))) return; + // 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) + const std::chrono::seconds seeds_wait_time = (addrman.size() >= DNSSEEDS_DELAY_PEER_THRESHOLD ? DNSSEEDS_DELAY_MANY_PEERS : DNSSEEDS_DELAY_FEW_PEERS); - LOCK(cs_vNodes); - int nRelevant = 0; - for (const CNode* pnode : vNodes) { - nRelevant += pnode->fSuccessfullyConnected && !pnode->fFeeler && !pnode->fOneShot && !pnode->m_manual_connection && !pnode->fInbound; - } - if (nRelevant >= 2) { - LogPrintf("P2P peers available. Skipped DNS seeding.\n"); - return; - } + for (const std::string& seed : seeds) { + if (seeds_right_now == 0) { seeds_right_now += DNSSEEDS_TO_QUERY_AT_ONCE; + + if (addrman.size() > 0) { + LogPrintf("Waiting %d seconds before querying DNS seeds.\n", seeds_wait_time.count()); + std::chrono::seconds to_wait = seeds_wait_time; + while (to_wait.count() > 0) { + std::chrono::seconds w = std::min(DNSSEEDS_DELAY_FEW_PEERS, to_wait); + if (!interruptNet.sleep_for(w)) return; + to_wait -= w; + + int nRelevant = 0; + { + LOCK(cs_vNodes); + for (const CNode* pnode : vNodes) { + nRelevant += pnode->fSuccessfullyConnected && !pnode->fFeeler && !pnode->fOneShot && !pnode->m_manual_connection && !pnode->fInbound; + } + } + if (nRelevant >= 2) { + if (found > 0) { + LogPrintf("%d addresses found from DNS seeds\n", found); + LogPrintf("P2P peers available. Finished DNS seeding.\n"); + } else { + LogPrintf("P2P peers available. Skipped DNS seeding.\n"); + } + return; + } + } + } } if (interruptNet) { return; } + LogPrintf("Loading addresses from DNS seed %s\n", seed); if (HaveNameProxy()) { AddOneShot(seed);