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