io.netty.resolver.dns.DnsServerAddresses Maven / Gradle / Ivy
/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.resolver.dns;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.lang.reflect.Method;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
/**
* Provides an infinite sequence of DNS server addresses to {@link DnsNameResolver}.
*/
@SuppressWarnings("IteratorNextCanNotThrowNoSuchElementException")
public abstract class DnsServerAddresses {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(DnsServerAddresses.class);
private static final List DEFAULT_NAME_SERVER_LIST;
private static final InetSocketAddress[] DEFAULT_NAME_SERVER_ARRAY;
private static final DnsServerAddresses DEFAULT_NAME_SERVERS;
static {
final int DNS_PORT = 53;
final List defaultNameServers = new ArrayList(2);
try {
Class configClass = Class.forName("sun.net.dns.ResolverConfiguration");
Method open = configClass.getMethod("open");
Method nameservers = configClass.getMethod("nameservers");
Object instance = open.invoke(null);
@SuppressWarnings("unchecked")
final List list = (List) nameservers.invoke(instance);
for (String a: list) {
if (a != null) {
defaultNameServers.add(new InetSocketAddress(InetAddress.getByName(a), DNS_PORT));
}
}
} catch (Exception ignore) {
// Failed to get the system name server list.
// Will add the default name servers afterwards.
}
if (!defaultNameServers.isEmpty()) {
if (logger.isDebugEnabled()) {
logger.debug(
"Default DNS servers: {} (sun.net.dns.ResolverConfiguration)", defaultNameServers);
}
} else {
Collections.addAll(
defaultNameServers,
new InetSocketAddress("8.8.8.8", DNS_PORT),
new InetSocketAddress("8.8.4.4", DNS_PORT));
if (logger.isWarnEnabled()) {
logger.warn(
"Default DNS servers: {} (Google Public DNS as a fallback)", defaultNameServers);
}
}
DEFAULT_NAME_SERVER_LIST = Collections.unmodifiableList(defaultNameServers);
DEFAULT_NAME_SERVER_ARRAY = defaultNameServers.toArray(new InetSocketAddress[defaultNameServers.size()]);
DEFAULT_NAME_SERVERS = sequential(DEFAULT_NAME_SERVER_ARRAY);
}
/**
* Returns the list of the system DNS server addresses. If it failed to retrieve the list of the system DNS server
* addresses from the environment, it will return {@code "8.8.8.8"} and {@code "8.8.4.4"}, the addresses of the
* Google public DNS servers.
*/
public static List defaultAddressList() {
return DEFAULT_NAME_SERVER_LIST;
}
/**
* Returns the {@link DnsServerAddresses} that yields the system DNS server addresses sequentially. If it failed to
* retrieve the list of the system DNS server addresses from the environment, it will use {@code "8.8.8.8"} and
* {@code "8.8.4.4"}, the addresses of the Google public DNS servers.
*
* This method has the same effect with the following code:
*
* DnsServerAddresses.sequential(DnsServerAddresses.defaultAddressList());
*
*
*/
public static DnsServerAddresses defaultAddresses() {
return DEFAULT_NAME_SERVERS;
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code addresses} sequentially. Once the
* last address is yielded, it will start again from the first address.
*/
public static DnsServerAddresses sequential(Iterable addresses) {
return sequential0(sanitize(addresses));
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code addresses} sequentially. Once the
* last address is yielded, it will start again from the first address.
*/
public static DnsServerAddresses sequential(InetSocketAddress... addresses) {
return sequential0(sanitize(addresses));
}
private static DnsServerAddresses sequential0(final InetSocketAddress... addresses) {
if (addresses.length == 1) {
return singleton(addresses[0]);
}
return new DefaultDnsServerAddresses("sequential", addresses) {
@Override
public DnsServerAddressStream stream() {
return new SequentialDnsServerAddressStream(addresses, 0);
}
};
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code address} in a shuffled order. Once all
* addresses are yielded, the addresses are shuffled again.
*/
public static DnsServerAddresses shuffled(Iterable addresses) {
return shuffled0(sanitize(addresses));
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code addresses} in a shuffled order. Once all
* addresses are yielded, the addresses are shuffled again.
*/
public static DnsServerAddresses shuffled(InetSocketAddress... addresses) {
return shuffled0(sanitize(addresses));
}
private static DnsServerAddresses shuffled0(final InetSocketAddress[] addresses) {
if (addresses.length == 1) {
return singleton(addresses[0]);
}
return new DefaultDnsServerAddresses("shuffled", addresses) {
@Override
public DnsServerAddressStream stream() {
return new ShuffledDnsServerAddressStream(addresses);
}
};
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code addresses} in a rotational sequential
* order. It is similar to {@link #sequential(Iterable)}, but each {@link DnsServerAddressStream} starts from
* a different starting point. For example, the first {@link #stream()} will start from the first address, the
* second one will start from the second address, and so on.
*/
public static DnsServerAddresses rotational(Iterable addresses) {
return rotational0(sanitize(addresses));
}
/**
* Returns the {@link DnsServerAddresses} that yields the specified {@code addresses} in a rotational sequential
* order. It is similar to {@link #sequential(Iterable)}, but each {@link DnsServerAddressStream} starts from
* a different starting point. For example, the first {@link #stream()} will start from the first address, the
* second one will start from the second address, and so on.
*/
public static DnsServerAddresses rotational(InetSocketAddress... addresses) {
return rotational0(sanitize(addresses));
}
private static DnsServerAddresses rotational0(final InetSocketAddress[] addresses) {
if (addresses.length == 1) {
return singleton(addresses[0]);
}
return new RotationalDnsServerAddresses(addresses);
}
/**
* Returns the {@link DnsServerAddresses} that yields only a single {@code address}.
*/
public static DnsServerAddresses singleton(final InetSocketAddress address) {
if (address == null) {
throw new NullPointerException("address");
}
if (address.isUnresolved()) {
throw new IllegalArgumentException("cannot use an unresolved DNS server address: " + address);
}
return new SingletonDnsServerAddresses(address);
}
private static InetSocketAddress[] sanitize(Iterable addresses) {
if (addresses == null) {
throw new NullPointerException("addresses");
}
final List list;
if (addresses instanceof Collection) {
list = new ArrayList(((Collection) addresses).size());
} else {
list = new ArrayList(4);
}
for (InetSocketAddress a : addresses) {
if (a == null) {
break;
}
if (a.isUnresolved()) {
throw new IllegalArgumentException("cannot use an unresolved DNS server address: " + a);
}
list.add(a);
}
if (list.isEmpty()) {
throw new IllegalArgumentException("empty addresses");
}
return list.toArray(new InetSocketAddress[list.size()]);
}
private static InetSocketAddress[] sanitize(InetSocketAddress[] addresses) {
if (addresses == null) {
throw new NullPointerException("addresses");
}
List list = new ArrayList(addresses.length);
for (InetSocketAddress a: addresses) {
if (a == null) {
break;
}
if (a.isUnresolved()) {
throw new IllegalArgumentException("cannot use an unresolved DNS server address: " + a);
}
list.add(a);
}
if (list.isEmpty()) {
return DEFAULT_NAME_SERVER_ARRAY;
}
return list.toArray(new InetSocketAddress[list.size()]);
}
/**
* Starts a new infinite stream of DNS server addresses. This method is invoked by {@link DnsNameResolver} on every
* uncached {@link DnsNameResolver#resolve(SocketAddress)} or {@link DnsNameResolver#resolveAll(SocketAddress)}.
*/
public abstract DnsServerAddressStream stream();
}