UnixResolverDnsServerAddressStreamProvider.java — netty Source File

Source Code

/*
 * Copyright 2017 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:
 *
 *   https://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.NetUtil;
import io.netty.util.internal.SocketUtils;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

import static io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider.DNS_PORT;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.StringUtil.indexOfNonWhiteSpace;
import static io.netty.util.internal.StringUtil.indexOfWhiteSpace;

/**
 * Able to parse files such as <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and
 * <a href="https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
 * /etc/resolver</a> to respect the system default domain servers.
 */
public final class UnixResolverDnsServerAddressStreamProvider implements DnsServerAddressStreamProvider {
    private static final InternalLogger logger =
            InternalLoggerFactory.getInstance(UnixResolverDnsServerAddressStreamProvider.class);

    private static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");
    private static final String RES_OPTIONS = System.getenv("RES_OPTIONS");

    private static final String ETC_RESOLV_CONF_FILE = "/etc/resolv.conf";
    private static final String ETC_RESOLVER_DIR = "/etc/resolver";
    private static final String NAMESERVER_ROW_LABEL = "nameserver";
    private static final String SORTLIST_ROW_LABEL = "sortlist";
    private static final String OPTIONS_ROW_LABEL = "options ";
    private static final String OPTIONS_ROTATE_FLAG = "rotate";
    private static final String DOMAIN_ROW_LABEL = "domain";
    private static final String SEARCH_ROW_LABEL = "search";
// ... (351 more lines)