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// Copyright 2017 Yahoo Holdings. 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.collect.ImmutableSet;
import com.google.common.net.InetAddresses;
import com.yahoo.log.LogLevel;
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.Optional;
import java.util.Set;
import java.util.logging.Logger;
/**
* 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 {
private static final Logger logger = Logger.getLogger(DnsNameResolver.class.getName());
@Override
public Set<String> getAllByNameOrThrow(String hostname) {
try {
Optional<String> cname = lookupName(hostname, Type.CNAME);
if (cname.isPresent()) {
hostname = cname.get();
}
Optional<String> inet4Address = lookupName(hostname, Type.A);
Optional<String> inet6Address = lookupName(hostname, Type.AAAA);
ImmutableSet.Builder<String> ipAddresses = ImmutableSet.builder();
inet4Address.ifPresent(ipAddresses::add);
inet6Address.ifPresent(ipAddresses::add);
return ipAddresses.build();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
@Override
public Optional<String> getHostname(String ipAddress) {
try {
String hostname = InetAddress.getByName(ipAddress).getHostName();
return InetAddresses.isInetAddress(hostname) ? Optional.empty() : Optional.of(hostname);
} catch (UnknownHostException e) {
// This is not an exceptional state hence the debug level
logger.log(LogLevel.DEBUG, "Unable to resolve ipaddress", e);
}
return Optional.empty();
}
private Optional<String> lookupName(String name, Type type) throws NamingException {
DirContext ctx = new InitialDirContext();
Attributes attributes = ctx.getAttributes("dns:/" + name, new String[]{type.value});
Optional<Attribute> attribute = Optional.ofNullable(attributes.get(type.value));
if (attribute.isPresent()) {
return Optional.ofNullable(attribute.get().get()).map(Object::toString);
}
return Optional.empty();
}
private enum Type {
A("A"),
AAAA("AAAA"),
CNAME("CNAME");
private final String value;
Type(String value) {
this.value = value;
}
}
}
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