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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.provision.persistence;
import com.google.common.net.InetAddresses;
import javax.naming.NamingException;
import javax.naming.directory.Attribute;
import javax.naming.directory.Attributes;
import javax.naming.directory.DirContext;
import javax.naming.directory.InitialDirContext;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
/**
* Implementation of a name resolver that always uses a DNS server to resolve the given name. The intention is to avoid
* possibly incorrect/incomplete records in /etc/hosts.
*
* @author mpolden
*/
public class DnsNameResolver implements NameResolver {
@Override
public Set<String> resolveAll(String name) {
return resolve(name, RecordType.A, RecordType.AAAA);
}
@Override
public Set<String> resolve(String name, RecordType first, RecordType... rest) {
Set<String> results = new HashSet<>();
for (var type : EnumSet.of(first, rest)) {
try {
results.addAll(lookupName(name, type));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return Collections.unmodifiableSet(results);
}
@Override
public Optional<String> resolveHostname(String ipAddress) {
try {
// TODO(mpolden): Use lookupName instead. IP address must be translated to its reverse
// notation first.
String hostname = InetAddress.getByName(ipAddress).getHostName();
return InetAddresses.isInetAddress(hostname) ? Optional.empty() : Optional.of(hostname);
} catch (UnknownHostException ignored) {
}
return Optional.empty();
}
private Set<String> lookupName(String name, RecordType type) throws NamingException {
DirContext ctx = new InitialDirContext();
Attributes attributes = ctx.getAttributes("dns:/" + name, new String[]{type.value()});
Attribute attribute = attributes.get(type.value());
if (attribute == null) {
return Set.of();
}
Set<String> results = new HashSet<>();
attribute.getAll().asIterator().forEachRemaining(value -> results.add(Objects.toString(value)));
return results;
}
}
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