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Do not query all DNS seed at once

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Instead, when necessary, query 3. If that leads to a sufficient number
of connects, stop. If not, query 3 more, and so on.
This commit is contained in:
Pieter Wuille 2019-03-07 15:30:59 -08:00
parent e5fdda68c6
commit 6170ec5d3a
1 changed files with 36 additions and 29 deletions
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41
src/net.cpp
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@ -49,6 +49,9 @@ static_assert(MINIUPNPC_API_VERSION >= 10, "miniUPnPc API version >= 10 assumed"
// Dump addresses to peers.dat every 15 minutes (900s) // Dump addresses to peers.dat every 15 minutes (900s)
static constexpr int DUMP_PEERS_INTERVAL = 15 * 60; 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;
// We add a random period time (0 to 1 seconds) to feeler connections to prevent synchronization. // We add a random period time (0 to 1 seconds) to feeler connections to prevent synchronization.
#define FEELER_SLEEP_WINDOW 1 #define FEELER_SLEEP_WINDOW 1
@ -1508,14 +1511,24 @@ void StopMapPort()
void CConnman::ThreadDNSAddressSeed() void CConnman::ThreadDNSAddressSeed()
{ {
// goal: only query DNS seeds if address need is acute FastRandomContext rng;
std::vector<std::string> seeds = Params().DNSSeeds();
Shuffle(seeds.begin(), seeds.end(), rng);
int seeds_right_now = 0; // Number of seeds left before testing if we have enough connections
int found = 0;
if (gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED)) {
// When -forcednsseed is provided, 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 // Avoiding DNS seeds when we don't need them improves user privacy by
// creating fewer identifying DNS requests, reduces trust by giving seeds // creating fewer identifying DNS requests, reduces trust by giving seeds
// less influence on the network topology, and reduces traffic to the seeds. // less influence on the network topology, and reduces traffic to the seeds.
if ((addrman.size() > 0) && if (addrman.size() > 0 && seeds_right_now == 0) {
(!gArgs.GetBoolArg("-forcednsseed", DEFAULT_FORCEDNSSEED))) { if (!interruptNet.sleep_for(std::chrono::seconds(11))) return;
if (!interruptNet.sleep_for(std::chrono::seconds(11)))
return;
LOCK(cs_vNodes); LOCK(cs_vNodes);
int nRelevant = 0; int nRelevant = 0;
@ -1526,17 +1539,13 @@ void CConnman::ThreadDNSAddressSeed()
LogPrintf("P2P peers available. Skipped DNS seeding.\n"); LogPrintf("P2P peers available. Skipped DNS seeding.\n");
return; return;
} }
seeds_right_now += DNSSEEDS_TO_QUERY_AT_ONCE;
} }
const std::vector<std::string> &vSeeds = Params().DNSSeeds();
int found = 0;
LogPrintf("Loading addresses from DNS seeds (could take a while)\n");
for (const std::string &seed : vSeeds) {
if (interruptNet) { if (interruptNet) {
return; return;
} }
LogPrintf("Loading addresses from DNS seed %s\n", seed);
if (HaveNameProxy()) { if (HaveNameProxy()) {
AddOneShot(seed); AddOneShot(seed);
} else { } else {
@ -1549,13 +1558,11 @@ void CConnman::ThreadDNSAddressSeed()
continue; continue;
} }
unsigned int nMaxIPs = 256; // Limits number of IPs learned from a DNS seed unsigned int nMaxIPs = 256; // Limits number of IPs learned from a DNS seed
if (LookupHost(host.c_str(), vIPs, nMaxIPs, true)) if (LookupHost(host.c_str(), vIPs, nMaxIPs, true)) {
{ for (const CNetAddr& ip : vIPs) {
for (const CNetAddr& ip : vIPs)
{
int nOneDay = 24*3600; int nOneDay = 24*3600;
CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits); CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
addr.nTime = GetTime() - 3*nOneDay - GetRand(4*nOneDay); // use a random age between 3 and 7 days old addr.nTime = GetTime() - 3*nOneDay - rng.randrange(4*nOneDay); // use a random age between 3 and 7 days old
vAdd.push_back(addr); vAdd.push_back(addr);
found++; found++;
} }
@ -1566,8 +1573,8 @@ void CConnman::ThreadDNSAddressSeed()
AddOneShot(seed); AddOneShot(seed);
} }
} }
--seeds_right_now;
} }
LogPrintf("%d addresses found from DNS seeds\n", found); LogPrintf("%d addresses found from DNS seeds\n", found);
} }