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/*
* 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.netty.resolver.dns;
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.resolver.dns.DefaultDnsServerAddressStreamProvider.DNS_PORT;
import static io.netty.util.internal.ObjectUtil.checkNotNull;
import static io.netty.util.internal.StringUtil.indexOfNonWhiteSpace;
/**
* Able to parse files such as /etc/resolv.conf and
*
* /etc/resolver 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 domainToNameServerStreamMap;
private static final Pattern SEARCH_DOMAIN_PATTERN = Pattern.compile("\\s+");
/**
* 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 /etc/resolv.conf which may contain
* the default DNS server to use, and also overrides for individual domains. Also parse list of files of the format
*
* /etc/resolver which may contain multiple files to override the name servers used for multimple domains.
* @param etcResolvConf /etc/resolv.conf.
* @param etcResolverFiles List of files of the format defined in
*
* /etc/resolver.
* @throws IOException If an error occurs while parsing the input files.
*/
public UnixResolverDnsServerAddressStreamProvider(File etcResolvConf, File... etcResolverFiles) throws IOException {
Map 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 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 /etc/resolv.conf which may contain
* the default DNS server to use, and also overrides for individual domains. Also parse a directory of the format
*
* /etc/resolver which may contain multiple files to override the name servers used for multimple domains.
* @param etcResolvConf /etc/resolv.conf.
* @param etcResolverDir Directory containing files of the format defined in
*
* /etc/resolver.
* @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 parse(File... etcResolverFiles) throws IOException {
Map domainToNameServerStreamMap =
new HashMap(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 addresses = new ArrayList(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(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 domainToNameServerStreamMap,
String domainName,
List addresses) {
// TODO(scott): sortlist is being ignored.
putIfAbsent(domainToNameServerStreamMap, domainName, DnsServerAddresses.sequential(addresses));
}
private static void putIfAbsent(Map 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 /etc/resolv.conf 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 /etc/resolv.conf and return the
* value corresponding to the first ndots in an options configuration.
* @param etcResolvConf a file of the format /etc/resolv.conf.
* @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 /etc/resolv.conf 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 parseEtcResolverSearchDomains() throws IOException {
return parseEtcResolverSearchDomains(new File(ETC_RESOLV_CONF_FILE));
}
/**
* Parse a file of the format /etc/resolv.conf and return the
* list of search domains found in it or an empty list if not found.
* @param etcResolvConf a file of the format /etc/resolv.conf.
* @return List of search domains.
* @throws IOException If a failure occurs parsing the file.
*/
static List parseEtcResolverSearchDomains(File etcResolvConf) throws IOException {
String localDomain = null;
List searchDomains = new ArrayList();
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;
}
}
