/*
* 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.HashMap;
import java.util.List;
import java.util.Map;
import static io.netty.resolver.dns.DefaultDnsServerAddressStreamProvider.DNS_PORT;
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 NAMESERVER_ROW_LABEL = "nameserver";
private static final String SORTLIST_ROW_LABEL = "sortlist";
private static final String DOMAIN_ROW_LABEL = "domain";
private static final String PORT_ROW_LABEL = "port";
private final DnsServerAddresses defaultNameServerAddresses;
private final Map<String, DnsServerAddresses> domainToNameServerStreamMap;
/**
* 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}.
*/
public static DnsServerAddressStreamProvider parseSilently() {
try {
UnixResolverDnsServerAddressStreamProvider nameServerCache =
new UnixResolverDnsServerAddressStreamProvider("/etc/resolv.conf", "/etc/resolver");
return nameServerCache.mayOverrideNameServers() ? nameServerCache
: DefaultDnsServerAddressStreamProvider.INSTANCE;
} catch (Exception e) {
logger.debug("failed to parse /etc/resolv.conf and/or /etc/resolver", 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 {
if (etcResolvConf == null && (etcResolverFiles == null || etcResolverFiles.length == 0)) {
throw new IllegalArgumentException("no files to parse");
}
if (etcResolverFiles != null) {
domainToNameServerStreamMap = parse(etcResolverFiles);
if (etcResolvConf != null) {
Map<String, DnsServerAddresses> etcResolvConfMap = parse(etcResolvConf);
defaultNameServerAddresses = etcResolvConfMap.remove(etcResolvConf.getName());
domainToNameServerStreamMap.putAll(etcResolvConfMap);
} else {
defaultNameServerAddresses = null;
}
} else {
domainToNameServerStreamMap = parse(etcResolvConf);
defaultNameServerAddresses = domainToNameServerStreamMap.remove(etcResolvConf.getName());
}
}
/**
* 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 != null ? defaultNameServerAddresses.stream() : null;
}
DnsServerAddresses addresses = domainToNameServerStreamMap.get(hostname);
if (addresses != null) {
return addresses.stream();
}
hostname = hostname.substring(i + 1);
}
}
boolean mayOverrideNameServers() {
return !domainToNameServerStreamMap.isEmpty() ||
defaultNameServerAddresses != null && 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(new InetSocketAddress(SocketUtils.addressByName(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 != null && !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 != null && !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.shuffled(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);
}
}
}