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LookupServer: Move cache check into the outer lookup() method

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Where it belongs, alongside the /etc/hosts check. The inner lookup() method is
really about talking to a specific DNS server.

Also, don't bail out on a empty name. An empty DNSName is actually '.' — a
single dot — aka the DNS root.
This commit is contained in:
Sergey Bugaev 2021-02-14 16:48:14 +03:00 • committed by Andreas Kling
parent af6aac8c55
commit 3fba6bfb5e
1 changed files with 34 additions and 33 deletions
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67
Userland/Services/LookupServer/LookupServer.cpp
View file

@ -134,6 +134,7 @@ Vector<String> LookupServer::lookup(const DNSName& name, unsigned short record_t
Vector<String> responses; Vector<String> responses;
// First, try local data.
if (auto local_answers = m_etc_hosts.get(name); local_answers.has_value()) { if (auto local_answers = m_etc_hosts.get(name); local_answers.has_value()) {
for (auto& answer : local_answers.value()) { for (auto& answer : local_answers.value()) {
if (answer.type() == record_type) if (answer.type() == record_type)
@ -143,41 +144,10 @@ Vector<String> LookupServer::lookup(const DNSName& name, unsigned short record_t
return responses; return responses;
} }
if (!name.as_string().is_empty()) { // Second, try our cache.
for (auto& nameserver : m_nameservers) {
#if LOOKUPSERVER_DEBUG
dbgln("Doing lookup using nameserver '{}'", nameserver);
#endif
bool did_get_response = false;
int retries = 3;
do {
responses = lookup(name, nameserver, did_get_response, record_type);
if (did_get_response)
break;
} while (--retries);
if (!responses.is_empty()) {
break;
} else {
if (!did_get_response)
dbgln("Never got a response from '{}', trying next nameserver", nameserver);
else
dbgln("Received response from '{}' but no result(s), trying next nameserver", nameserver);
}
}
if (responses.is_empty()) {
fprintf(stderr, "LookupServer: Tried all nameservers but never got a response :(\n");
return {};
}
}
return move(responses);
}
Vector<String> LookupServer::lookup(const DNSName& name, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
{
if (auto cached_answers = m_lookup_cache.get(name); cached_answers.has_value()) { if (auto cached_answers = m_lookup_cache.get(name); cached_answers.has_value()) {
Vector<String> responses;
for (auto& answer : cached_answers.value()) { for (auto& answer : cached_answers.value()) {
// TODO: Actually remove expired answers from the cache.
if (answer.type() == record_type && !answer.has_expired()) { if (answer.type() == record_type && !answer.has_expired()) {
#if LOOKUPSERVER_DEBUG #if LOOKUPSERVER_DEBUG
dbgln("Cache hit: {} -> {}", name.as_string(), answer.record_data()); dbgln("Cache hit: {} -> {}", name.as_string(), answer.record_data());
@ -189,6 +159,37 @@ Vector<String> LookupServer::lookup(const DNSName& name, const String& nameserve
return responses; return responses;
} }
// Third, ask the upstream nameservers.
for (auto& nameserver : m_nameservers) {
#if LOOKUPSERVER_DEBUG
dbgln("Doing lookup using nameserver '{}'", nameserver);
#endif
bool did_get_response = false;
int retries = 3;
do {
responses = lookup(name, nameserver, did_get_response, record_type);
if (did_get_response)
break;
} while (--retries);
if (!responses.is_empty()) {
break;
} else {
if (!did_get_response)
dbgln("Never got a response from '{}', trying next nameserver", nameserver);
else
dbgln("Received response from '{}' but no result(s), trying next nameserver", nameserver);
}
}
if (responses.is_empty()) {
fprintf(stderr, "LookupServer: Tried all nameservers but never got a response :(\n");
return {};
}
return move(responses);
}
Vector<String> LookupServer::lookup(const DNSName& name, const String& nameserver, bool& did_get_response, unsigned short record_type, ShouldRandomizeCase should_randomize_case)
{
DNSPacket request; DNSPacket request;
request.set_is_query(); request.set_is_query();
request.set_id(arc4random_uniform(UINT16_MAX)); request.set_id(arc4random_uniform(UINT16_MAX));