370 lines
18 KiB
Java
370 lines
18 KiB
Java
/*
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* Copyright 2017 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.NetUtil;
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import io.netty.util.internal.SocketUtils;
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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.io.BufferedReader;
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import java.io.File;
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import java.io.FileReader;
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import java.io.IOException;
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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.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.regex.Pattern;
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import static io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider.DNS_PORT;
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import static io.netty.util.internal.StringUtil.indexOfNonWhiteSpace;
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import static io.netty.util.internal.StringUtil.indexOfWhiteSpace;
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import static java.util.Objects.requireNonNull;
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/**
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* Able to parse files such as <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and
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* <a href="https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
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* /etc/resolver</a> to respect the system default domain servers.
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*/
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public final class UnixResolverDnsServerAddressStreamProvider implements DnsServerAddressStreamProvider {
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private static final InternalLogger logger =
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InternalLoggerFactory.getInstance(UnixResolverDnsServerAddressStreamProvider.class);
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private static final String ETC_RESOLV_CONF_FILE = "/etc/resolv.conf";
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private static final String ETC_RESOLVER_DIR = "/etc/resolver";
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private static final String NAMESERVER_ROW_LABEL = "nameserver";
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private static final String SORTLIST_ROW_LABEL = "sortlist";
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private static final String OPTIONS_ROW_LABEL = "options";
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private static final String DOMAIN_ROW_LABEL = "domain";
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private static final String SEARCH_ROW_LABEL = "search";
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private static final String PORT_ROW_LABEL = "port";
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private static final String NDOTS_LABEL = "ndots:";
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static final int DEFAULT_NDOTS = 1;
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private final DnsServerAddresses defaultNameServerAddresses;
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private final Map<String, DnsServerAddresses> domainToNameServerStreamMap;
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private static final Pattern SEARCH_DOMAIN_PATTERN = Pattern.compile("\\s+");
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/**
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* Attempt to parse {@code /etc/resolv.conf} and files in the {@code /etc/resolver} directory by default.
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* A failure to parse will return {@link DefaultDnsServerAddressStreamProvider}.
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*/
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static DnsServerAddressStreamProvider parseSilently() {
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try {
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UnixResolverDnsServerAddressStreamProvider nameServerCache =
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new UnixResolverDnsServerAddressStreamProvider(ETC_RESOLV_CONF_FILE, ETC_RESOLVER_DIR);
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return nameServerCache.mayOverrideNameServers() ? nameServerCache
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: DefaultDnsServerAddressStreamProvider.INSTANCE;
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} catch (Exception e) {
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if (logger.isDebugEnabled()) {
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logger.debug("failed to parse {} and/or {}", ETC_RESOLV_CONF_FILE, ETC_RESOLVER_DIR, e);
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}
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return DefaultDnsServerAddressStreamProvider.INSTANCE;
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}
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> which may contain
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* the default DNS server to use, and also overrides for individual domains. Also parse list of files of the format
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* <a href="
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* https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
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* /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains.
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* @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
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* @param etcResolverFiles List of files of the format defined in
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* <a href="
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* https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
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* /etc/resolver</a>.
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* @throws IOException If an error occurs while parsing the input files.
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*/
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public UnixResolverDnsServerAddressStreamProvider(File etcResolvConf, File... etcResolverFiles) throws IOException {
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Map<String, DnsServerAddresses> etcResolvConfMap = parse(requireNonNull(etcResolvConf, "etcResolvConf"));
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final boolean useEtcResolverFiles = etcResolverFiles != null && etcResolverFiles.length != 0;
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domainToNameServerStreamMap = useEtcResolverFiles ? parse(etcResolverFiles) : etcResolvConfMap;
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DnsServerAddresses defaultNameServerAddresses = etcResolvConfMap.get(etcResolvConf.getName());
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if (defaultNameServerAddresses == null) {
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Collection<DnsServerAddresses> values = etcResolvConfMap.values();
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if (values.isEmpty()) {
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throw new IllegalArgumentException(etcResolvConf + " didn't provide any name servers");
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}
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this.defaultNameServerAddresses = values.iterator().next();
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} else {
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this.defaultNameServerAddresses = defaultNameServerAddresses;
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}
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if (useEtcResolverFiles) {
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domainToNameServerStreamMap.putAll(etcResolvConfMap);
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}
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> which may contain
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* the default DNS server to use, and also overrides for individual domains. Also parse a directory of the format
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* <a href="
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* https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
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* /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains.
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* @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
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* @param etcResolverDir Directory containing files of the format defined in
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* <a href="
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* https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html">
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* /etc/resolver</a>.
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* @throws IOException If an error occurs while parsing the input files.
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*/
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public UnixResolverDnsServerAddressStreamProvider(String etcResolvConf, String etcResolverDir) throws IOException {
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this(etcResolvConf == null ? null : new File(etcResolvConf),
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etcResolverDir == null ? null : new File(etcResolverDir).listFiles());
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}
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@Override
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public DnsServerAddressStream nameServerAddressStream(String hostname) {
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for (;;) {
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int i = hostname.indexOf('.', 1);
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if (i < 0 || i == hostname.length() - 1) {
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return defaultNameServerAddresses.stream();
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}
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DnsServerAddresses addresses = domainToNameServerStreamMap.get(hostname);
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if (addresses != null) {
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return addresses.stream();
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}
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hostname = hostname.substring(i + 1);
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}
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}
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private boolean mayOverrideNameServers() {
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return !domainToNameServerStreamMap.isEmpty() || defaultNameServerAddresses.stream().next() != null;
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}
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private static Map<String, DnsServerAddresses> parse(File... etcResolverFiles) throws IOException {
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Map<String, DnsServerAddresses> domainToNameServerStreamMap =
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new HashMap<>(etcResolverFiles.length << 1);
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for (File etcResolverFile : etcResolverFiles) {
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if (!etcResolverFile.isFile()) {
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continue;
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}
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FileReader fr = new FileReader(etcResolverFile);
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BufferedReader br = null;
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try {
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br = new BufferedReader(fr);
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List<InetSocketAddress> addresses = new ArrayList<>(2);
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String domainName = etcResolverFile.getName();
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int port = DNS_PORT;
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String line;
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while ((line = br.readLine()) != null) {
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line = line.trim();
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try {
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char c;
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if (line.isEmpty() || (c = line.charAt(0)) == '#' || c == ';') {
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continue;
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}
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if (line.startsWith(NAMESERVER_ROW_LABEL)) {
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int i = indexOfNonWhiteSpace(line, NAMESERVER_ROW_LABEL.length());
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if (i < 0) {
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throw new IllegalArgumentException("error parsing label " + NAMESERVER_ROW_LABEL +
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" in file " + etcResolverFile + ". value: " + line);
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}
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String maybeIP;
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int x = indexOfWhiteSpace(line, i);
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if (x == -1) {
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maybeIP = line.substring(i);
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} else {
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// ignore comments
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int idx = indexOfNonWhiteSpace(line, x);
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if (idx == -1 || line.charAt(idx) != '#') {
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throw new IllegalArgumentException("error parsing label " + NAMESERVER_ROW_LABEL +
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" in file " + etcResolverFile + ". value: " + line);
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}
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maybeIP = line.substring(i, x);
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}
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// There may be a port appended onto the IP address so we attempt to extract it.
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if (!NetUtil.isValidIpV4Address(maybeIP) && !NetUtil.isValidIpV6Address(maybeIP)) {
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i = maybeIP.lastIndexOf('.');
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if (i + 1 >= maybeIP.length()) {
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throw new IllegalArgumentException("error parsing label " + NAMESERVER_ROW_LABEL +
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" in file " + etcResolverFile + ". invalid IP value: " + line);
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}
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port = Integer.parseInt(maybeIP.substring(i + 1));
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maybeIP = maybeIP.substring(0, i);
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}
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addresses.add(SocketUtils.socketAddress(maybeIP, port));
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} else if (line.startsWith(DOMAIN_ROW_LABEL)) {
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int i = indexOfNonWhiteSpace(line, DOMAIN_ROW_LABEL.length());
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if (i < 0) {
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throw new IllegalArgumentException("error parsing label " + DOMAIN_ROW_LABEL +
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" in file " + etcResolverFile + " value: " + line);
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}
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domainName = line.substring(i);
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if (!addresses.isEmpty()) {
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putIfAbsent(domainToNameServerStreamMap, domainName, addresses);
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}
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addresses = new ArrayList<>(2);
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} else if (line.startsWith(PORT_ROW_LABEL)) {
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int i = indexOfNonWhiteSpace(line, PORT_ROW_LABEL.length());
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if (i < 0) {
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throw new IllegalArgumentException("error parsing label " + PORT_ROW_LABEL +
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" in file " + etcResolverFile + " value: " + line);
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}
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port = Integer.parseInt(line.substring(i));
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} else if (line.startsWith(SORTLIST_ROW_LABEL)) {
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logger.info("row type {} not supported. Ignoring line: {}", SORTLIST_ROW_LABEL, line);
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}
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} catch (IllegalArgumentException e) {
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logger.warn("Could not parse entry. Ignoring line: {}", line, e);
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}
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}
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if (!addresses.isEmpty()) {
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putIfAbsent(domainToNameServerStreamMap, domainName, addresses);
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}
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} finally {
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if (br == null) {
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fr.close();
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} else {
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br.close();
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}
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}
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}
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return domainToNameServerStreamMap;
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}
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private static void putIfAbsent(Map<String, DnsServerAddresses> domainToNameServerStreamMap,
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String domainName,
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List<InetSocketAddress> addresses) {
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// TODO(scott): sortlist is being ignored.
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putIfAbsent(domainToNameServerStreamMap, domainName, DnsServerAddresses.sequential(addresses));
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}
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private static void putIfAbsent(Map<String, DnsServerAddresses> domainToNameServerStreamMap,
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String domainName,
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DnsServerAddresses addresses) {
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DnsServerAddresses existingAddresses = domainToNameServerStreamMap.put(domainName, addresses);
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if (existingAddresses != null) {
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domainToNameServerStreamMap.put(domainName, existingAddresses);
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if (logger.isDebugEnabled()) {
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logger.debug("Domain name {} already maps to addresses {} so new addresses {} will be discarded",
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domainName, existingAddresses, addresses);
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}
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}
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the
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* value corresponding to the first ndots in an options configuration.
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* @return the value corresponding to the first ndots in an options configuration, or {@link #DEFAULT_NDOTS} if not
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* found.
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* @throws IOException If a failure occurs parsing the file.
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*/
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static int parseEtcResolverFirstNdots() throws IOException {
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return parseEtcResolverFirstNdots(new File(ETC_RESOLV_CONF_FILE));
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the
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* value corresponding to the first ndots in an options configuration.
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* @param etcResolvConf a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
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* @return the value corresponding to the first ndots in an options configuration, or {@link #DEFAULT_NDOTS} if not
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* found.
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* @throws IOException If a failure occurs parsing the file.
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*/
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static int parseEtcResolverFirstNdots(File etcResolvConf) throws IOException {
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FileReader fr = new FileReader(etcResolvConf);
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BufferedReader br = null;
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try {
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br = new BufferedReader(fr);
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String line;
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while ((line = br.readLine()) != null) {
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if (line.startsWith(OPTIONS_ROW_LABEL)) {
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int i = line.indexOf(NDOTS_LABEL);
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if (i >= 0) {
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i += NDOTS_LABEL.length();
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final int j = line.indexOf(' ', i);
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return Integer.parseInt(line.substring(i, j < 0 ? line.length() : j));
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}
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break;
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}
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}
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} finally {
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if (br == null) {
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fr.close();
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} else {
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br.close();
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}
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}
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return DEFAULT_NDOTS;
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the
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* list of search domains found in it or an empty list if not found.
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* @return List of search domains.
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* @throws IOException If a failure occurs parsing the file.
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*/
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static List<String> parseEtcResolverSearchDomains() throws IOException {
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return parseEtcResolverSearchDomains(new File(ETC_RESOLV_CONF_FILE));
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}
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/**
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* Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the
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* list of search domains found in it or an empty list if not found.
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* @param etcResolvConf a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>.
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* @return List of search domains.
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* @throws IOException If a failure occurs parsing the file.
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*/
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static List<String> parseEtcResolverSearchDomains(File etcResolvConf) throws IOException {
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String localDomain = null;
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List<String> searchDomains = new ArrayList<>();
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FileReader fr = new FileReader(etcResolvConf);
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BufferedReader br = null;
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try {
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br = new BufferedReader(fr);
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String line;
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while ((line = br.readLine()) != null) {
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if (localDomain == null && line.startsWith(DOMAIN_ROW_LABEL)) {
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int i = indexOfNonWhiteSpace(line, DOMAIN_ROW_LABEL.length());
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if (i >= 0) {
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localDomain = line.substring(i);
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}
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} else if (line.startsWith(SEARCH_ROW_LABEL)) {
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int i = indexOfNonWhiteSpace(line, SEARCH_ROW_LABEL.length());
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if (i >= 0) {
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// May contain more then one entry, either seperated by whitespace or tab.
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// See https://linux.die.net/man/5/resolver
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String[] domains = SEARCH_DOMAIN_PATTERN.split(line.substring(i));
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Collections.addAll(searchDomains, domains);
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}
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}
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}
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} finally {
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if (br == null) {
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fr.close();
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} else {
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br.close();
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}
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}
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// return what was on the 'domain' line only if there were no 'search' lines
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return localDomain != null && searchDomains.isEmpty()
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? Collections.singletonList(localDomain)
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: searchDomains;
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}
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}
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