Java tutorial
/* * 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: * * 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.vertx.core.dns.impl.netty; import io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider; import io.netty.resolver.dns.DnsServerAddressStream; import io.netty.resolver.dns.DnsServerAddressStreamProvider; import io.netty.resolver.dns.DnsServerAddresses; import io.netty.util.NetUtil; import io.netty.util.internal.SocketUtils; import io.netty.util.internal.UnstableApi; 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.util.internal.ObjectUtil.checkNotNull; import static io.netty.util.internal.StringUtil.indexOfNonWhiteSpace; /** * 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. */ @UnstableApi public final class UnixResolverDnsServerAddressStreamProvider implements DnsServerAddressStreamProvider { private static final InternalLogger logger = InternalLoggerFactory .getInstance(UnixResolverDnsServerAddressStreamProvider.class); 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 DOMAIN_ROW_LABEL = "domain"; private static final String SEARCH_ROW_LABEL = "search"; private static final String PORT_ROW_LABEL = "port"; private static final String NDOTS_LABEL = "ndots:"; static final int DEFAULT_NDOTS = 1; private final DnsServerAddresses defaultNameServerAddresses; private final Map<String, DnsServerAddresses> domainToNameServerStreamMap; private static final Pattern SEARCH_DOMAIN_PATTERN = Pattern.compile("\\s+"); static final int DNS_PORT = 53; /** * Attempt to parse {@code /etc/resolv.conf} and files in the {@code /etc/resolver} directory by default. * A failure to parse will return {@link DefaultDnsServerAddressStreamProvider}. */ static DnsServerAddressStreamProvider parseSilently() { try { UnixResolverDnsServerAddressStreamProvider nameServerCache = new UnixResolverDnsServerAddressStreamProvider( ETC_RESOLV_CONF_FILE, ETC_RESOLVER_DIR); return nameServerCache.mayOverrideNameServers() ? nameServerCache : DefaultDnsServerAddressStreamProvider.INSTANCE; } catch (Exception e) { logger.debug("failed to parse {} and/or {}", ETC_RESOLV_CONF_FILE, ETC_RESOLVER_DIR, e); return DefaultDnsServerAddressStreamProvider.INSTANCE; } } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> which may contain * the default DNS server to use, and also overrides for individual domains. Also parse list of files of the format * <a href=" * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html"> * /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains. * @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>. * @param etcResolverFiles List of files of the format defined in * <a href=" * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html"> * /etc/resolver</a>. * @throws IOException If an error occurs while parsing the input files. */ public UnixResolverDnsServerAddressStreamProvider(File etcResolvConf, File... etcResolverFiles) throws IOException { Map<String, DnsServerAddresses> etcResolvConfMap = parse(checkNotNull(etcResolvConf, "etcResolvConf")); final boolean useEtcResolverFiles = etcResolverFiles != null && etcResolverFiles.length != 0; domainToNameServerStreamMap = useEtcResolverFiles ? parse(etcResolverFiles) : etcResolvConfMap; DnsServerAddresses defaultNameServerAddresses = etcResolvConfMap.get(etcResolvConf.getName()); if (defaultNameServerAddresses == null) { Collection<DnsServerAddresses> values = etcResolvConfMap.values(); if (values.isEmpty()) { throw new IllegalArgumentException(etcResolvConf + " didn't provide any name servers"); } this.defaultNameServerAddresses = values.iterator().next(); } else { this.defaultNameServerAddresses = defaultNameServerAddresses; } if (useEtcResolverFiles) { domainToNameServerStreamMap.putAll(etcResolvConfMap); } } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> which may contain * the default DNS server to use, and also overrides for individual domains. Also parse a directory of the format * <a href=" * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html"> * /etc/resolver</a> which may contain multiple files to override the name servers used for multimple domains. * @param etcResolvConf <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>. * @param etcResolverDir Directory containing files of the format defined in * <a href=" * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html"> * /etc/resolver</a>. * @throws IOException If an error occurs while parsing the input files. */ public UnixResolverDnsServerAddressStreamProvider(String etcResolvConf, String etcResolverDir) throws IOException { this(etcResolvConf == null ? null : new File(etcResolvConf), etcResolverDir == null ? null : new File(etcResolverDir).listFiles()); } @Override public DnsServerAddressStream nameServerAddressStream(String hostname) { for (;;) { int i = hostname.indexOf('.', 1); if (i < 0 || i == hostname.length() - 1) { return defaultNameServerAddresses.stream(); } DnsServerAddresses addresses = domainToNameServerStreamMap.get(hostname); if (addresses != null) { return addresses.stream(); } hostname = hostname.substring(i + 1); } } private boolean mayOverrideNameServers() { return !domainToNameServerStreamMap.isEmpty() || defaultNameServerAddresses.stream().next() != null; } private static Map<String, DnsServerAddresses> parse(File... etcResolverFiles) throws IOException { Map<String, DnsServerAddresses> domainToNameServerStreamMap = new HashMap<String, DnsServerAddresses>( etcResolverFiles.length << 1); for (File etcResolverFile : etcResolverFiles) { if (!etcResolverFile.isFile()) { continue; } FileReader fr = new FileReader(etcResolverFile); BufferedReader br = null; try { br = new BufferedReader(fr); List<InetSocketAddress> addresses = new ArrayList<InetSocketAddress>(2); String domainName = etcResolverFile.getName(); int port = DNS_PORT; String line; while ((line = br.readLine()) != null) { line = line.trim(); char c; if (line.isEmpty() || (c = line.charAt(0)) == '#' || c == ';') { continue; } if (line.startsWith(NAMESERVER_ROW_LABEL)) { int i = indexOfNonWhiteSpace(line, NAMESERVER_ROW_LABEL.length()); if (i < 0) { throw new IllegalArgumentException("error parsing label " + NAMESERVER_ROW_LABEL + " in file " + etcResolverFile + ". value: " + line); } String maybeIP = line.substring(i); // There may be a port appended onto the IP address so we attempt to extract it. if (!NetUtil.isValidIpV4Address(maybeIP) && !NetUtil.isValidIpV6Address(maybeIP)) { i = maybeIP.lastIndexOf('.'); if (i + 1 >= maybeIP.length()) { throw new IllegalArgumentException("error parsing label " + NAMESERVER_ROW_LABEL + " in file " + etcResolverFile + ". invalid IP value: " + line); } port = Integer.parseInt(maybeIP.substring(i + 1)); maybeIP = maybeIP.substring(0, i); } addresses.add(SocketUtils.socketAddress(maybeIP, port)); } else if (line.startsWith(DOMAIN_ROW_LABEL)) { int i = indexOfNonWhiteSpace(line, DOMAIN_ROW_LABEL.length()); if (i < 0) { throw new IllegalArgumentException("error parsing label " + DOMAIN_ROW_LABEL + " in file " + etcResolverFile + " value: " + line); } domainName = line.substring(i); if (!addresses.isEmpty()) { putIfAbsent(domainToNameServerStreamMap, domainName, addresses); } addresses = new ArrayList<InetSocketAddress>(2); } else if (line.startsWith(PORT_ROW_LABEL)) { int i = indexOfNonWhiteSpace(line, PORT_ROW_LABEL.length()); if (i < 0) { throw new IllegalArgumentException("error parsing label " + PORT_ROW_LABEL + " in file " + etcResolverFile + " value: " + line); } port = Integer.parseInt(line.substring(i)); } else if (line.startsWith(SORTLIST_ROW_LABEL)) { logger.info("row type {} not supported. ignoring line: {}", SORTLIST_ROW_LABEL, line); } } if (!addresses.isEmpty()) { putIfAbsent(domainToNameServerStreamMap, domainName, addresses); } } finally { if (br == null) { fr.close(); } else { br.close(); } } } return domainToNameServerStreamMap; } private static void putIfAbsent(Map<String, DnsServerAddresses> domainToNameServerStreamMap, String domainName, List<InetSocketAddress> addresses) { // TODO(scott): sortlist is being ignored. putIfAbsent(domainToNameServerStreamMap, domainName, DnsServerAddresses.sequential(addresses)); } private static void putIfAbsent(Map<String, DnsServerAddresses> domainToNameServerStreamMap, String domainName, DnsServerAddresses addresses) { DnsServerAddresses existingAddresses = domainToNameServerStreamMap.put(domainName, addresses); if (existingAddresses != null) { domainToNameServerStreamMap.put(domainName, existingAddresses); logger.debug("Domain name {} already maps to addresses {} so new addresses {} will be discarded", domainName, existingAddresses, addresses); } } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the * value corresponding to the first ndots in an options configuration. * @return the value corresponding to the first ndots in an options configuration, or {@link #DEFAULT_NDOTS} if not * found. * @throws IOException If a failure occurs parsing the file. */ static int parseEtcResolverFirstNdots() throws IOException { return parseEtcResolverFirstNdots(new File(ETC_RESOLV_CONF_FILE)); } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the * value corresponding to the first ndots in an options configuration. * @param etcResolvConf a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>. * @return the value corresponding to the first ndots in an options configuration, or {@link #DEFAULT_NDOTS} if not * found. * @throws IOException If a failure occurs parsing the file. */ static int parseEtcResolverFirstNdots(File etcResolvConf) throws IOException { FileReader fr = new FileReader(etcResolvConf); BufferedReader br = null; try { br = new BufferedReader(fr); String line; while ((line = br.readLine()) != null) { if (line.startsWith(OPTIONS_ROW_LABEL)) { int i = line.indexOf(NDOTS_LABEL); if (i >= 0) { i += NDOTS_LABEL.length(); final int j = line.indexOf(' ', i); return Integer.parseInt(line.substring(i, j < 0 ? line.length() : j)); } break; } } } finally { if (br == null) { fr.close(); } else { br.close(); } } return DEFAULT_NDOTS; } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the * list of search domains found in it or an empty list if not found. * @return List of search domains. * @throws IOException If a failure occurs parsing the file. */ static List<String> parseEtcResolverSearchDomains() throws IOException { return parseEtcResolverSearchDomains(new File(ETC_RESOLV_CONF_FILE)); } /** * Parse a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a> and return the * list of search domains found in it or an empty list if not found. * @param etcResolvConf a file of the format <a href="https://linux.die.net/man/5/resolver">/etc/resolv.conf</a>. * @return List of search domains. * @throws IOException If a failure occurs parsing the file. */ static List<String> parseEtcResolverSearchDomains(File etcResolvConf) throws IOException { String localDomain = null; List<String> searchDomains = new ArrayList<String>(); FileReader fr = new FileReader(etcResolvConf); BufferedReader br = null; try { br = new BufferedReader(fr); String line; while ((line = br.readLine()) != null) { if (localDomain == null && line.startsWith(DOMAIN_ROW_LABEL)) { int i = indexOfNonWhiteSpace(line, DOMAIN_ROW_LABEL.length()); if (i >= 0) { localDomain = line.substring(i); } } else if (line.startsWith(SEARCH_ROW_LABEL)) { int i = indexOfNonWhiteSpace(line, SEARCH_ROW_LABEL.length()); if (i >= 0) { // May contain more then one entry, either seperated by whitespace or tab. // See https://linux.die.net/man/5/resolver String[] domains = SEARCH_DOMAIN_PATTERN.split(line.substring(i)); Collections.addAll(searchDomains, domains); } } } } finally { if (br == null) { fr.close(); } else { br.close(); } } // return what was on the 'domain' line only if there were no 'search' lines return localDomain != null && searchDomains.isEmpty() ? Collections.singletonList(localDomain) : searchDomains; } }