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net: Decrease nMaxIPs when learning from DNS seeds

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Limit number of IPs learned from a single DNS seed to 32, to prevent the results from
one DNS seed from dominating AddrMan. Note that the number of results from a UDP DNS query is
bounded to 33 already, but it is possible for it to use TCP where a potentially enormous
number of results can be returned.

Closes #16070.
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laanwj committed 2024-04-11 14:43:30 +02:00
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commit f2e3662e57
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src/net.cpp
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@@ -2256,7 +2256,11 @@ void CConnman::ThreadDNSAddressSeed()
if (!resolveSource.SetInternal(host)) { if (!resolveSource.SetInternal(host)) {
continue; continue;
} }
unsigned int nMaxIPs = 256; // Limits number of IPs learned from a DNS seed // Limit number of IPs learned from a single DNS seed. This limit exists to prevent the results from
// one DNS seed from dominating AddrMan. Note that the number of results from a UDP DNS query is
// bounded to 33 already, but it is possible for it to use TCP where a larger number of results can be
// returned.
unsigned int nMaxIPs = 32;
const auto addresses{LookupHost(host, nMaxIPs, true)}; const auto addresses{LookupHost(host, nMaxIPs, true)};
if (!addresses.empty()) { if (!addresses.empty()) {
for (const CNetAddr& ip : addresses) { for (const CNetAddr& ip : addresses) {