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LookupServer: Don't cache DNS questions

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We should only cache RRs (which we represent as instances of DNSAnswer), now
which questions generated them.
This commit is contained in:
Sergey Bugaev 2021-02-14 16:20:19 +03:00 • committed by Andreas Kling
parent 80f7489df0
commit 89f718c4c5
2 changed files with 29 additions and 24 deletions
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45
Userland/Services/LookupServer/LookupServer.cpp
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@ -155,21 +155,18 @@ Vector<String> LookupServer::lookup(const DNSName& name, unsigned short record_t
Vector<String> LookupServer::lookup(const DNSName& name, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
{
if (auto it = m_lookup_cache.find(name.as_string()); it != m_lookup_cache.end()) {
auto& cached_lookup = it->value;
if (cached_lookup.question.record_type() == record_type) {
Vector<String> responses;
for (auto& cached_answer : cached_lookup.answers) {
if (auto cached_answers = m_lookup_cache.get(name.as_string()); cached_answers.has_value()) {
Vector<String> responses;
for (auto& answer : cached_answers.value()) {
if (answer.type() == record_type && !answer.has_expired()) {
#if LOOKUPSERVER_DEBUG
dbgln("Cache hit: {} -> {}, expired: {}", name.as_string(), cached_answer.record_data(), cached_answer.has_expired());
dbgln("Cache hit: {} -> {}", name.as_string(), answer.record_data());
#endif
if (!cached_answer.has_expired())
responses.append(cached_answer.record_data());
responses.append(answer.record_data());
}
if (!responses.is_empty())
return responses;
}
m_lookup_cache.remove(it);
if (!responses.is_empty())
return responses;
}
DNSPacket request;
@ -250,21 +247,31 @@ Vector<String> LookupServer::lookup(const DNSName& name, const String& nameserve
}
Vector<String, 8> responses;
Vector<DNSAnswer, 8> cacheable_answers;
for (auto& answer : response.answers()) {
put_in_cache(answer);
if (answer.type() != record_type)
continue;
responses.append(answer.record_data());
if (!answer.has_expired())
cacheable_answers.append(answer);
}
if (!cacheable_answers.is_empty()) {
if (m_lookup_cache.size() >= 256)
m_lookup_cache.remove(m_lookup_cache.begin());
m_lookup_cache.set(name.as_string(), { request.questions()[0], move(cacheable_answers) });
}
return responses;
}
void LookupServer::put_in_cache(const DNSAnswer& answer)
{
if (answer.has_expired())
return;
// Prevent the cache from growing too big.
// TODO: Evict least used entries.
if (m_lookup_cache.size() >= 256)
m_lookup_cache.remove(m_lookup_cache.begin());
auto it = m_lookup_cache.find(answer.name().as_string());
if (it == m_lookup_cache.end())
m_lookup_cache.set(answer.name().as_string(), { answer });
else
it->value.append(answer);
}
}