/*
* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.dns.client;
import jdk.dns.client.ex.DnsResolverException;
import jdk.dns.client.internal.DnsName;
import jdk.dns.client.internal.HostsFileResolver;
import jdk.dns.client.internal.Resolver;
import jdk.dns.client.internal.ResourceClassType;
import jdk.dns.client.internal.ResourceRecord;
import jdk.dns.client.internal.ResourceRecords;
import jdk.dns.conf.DnsResolverConfiguration;
import sun.net.util.IPAddressUtil;
import java.net.InetAddress;
import java.net.ProtocolFamily;
import java.net.UnknownHostException;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
public class NetworkNamesResolver {
private final AddressFamily addressFamily;
public static NetworkNamesResolver open() throws UnknownHostException {
return new NetworkNamesResolver(AddressFamily.ANY);
}
public static NetworkNamesResolver open(ProtocolFamily protocolFamily) throws UnknownHostException {
return new NetworkNamesResolver(AddressFamily.fromProtocolFamily(protocolFamily));
}
private NetworkNamesResolver(AddressFamily addressFamily) throws UnknownHostException {
this.addressFamily = addressFamily;
this.dnsResolver = new Resolver(dnsResolverConfiguration.nameservers(), 1000, 4);
}
/**
* Lookup the IP address of a host.
* The family of required address needed can be specified with {@code addressFamily} parameter.
*
* @param hostname the specified host name
* @return first IP address that matches requested {@code addressFamily}
* @throws UnknownHostException if no IP address found for the specified host name and the specified address family
*/
public InetAddress lookupHostAddr(String hostname) throws UnknownHostException {
// First try hosts file
// TODO: Add nsswitch.conf to select proper order
try {
return hostsFileResolver.getHostAddress(hostname, addressFamily);
} catch (UnknownHostException uhe) {
if (DEBUG) {
System.err.printf("Hosts file doesn't know '%s' host with '%s' address family%n",
hostname, addressFamily.toString());
}
}
// If no luck - try to ask name servers
try {
var results = lookup(hostname, addressFamily, true, true, 0);
if (results.isEmpty()) {
throw new UnknownHostException(hostname);
}
return results.get(0);
} catch (DnsResolverException e) {
UnknownHostException uhe = new UnknownHostException(hostname);
uhe.initCause(e);
throw uhe;
}
}
/**
* <p>Lookup a host mapping by name. Retrieve the IP addresses
* associated with a host.
*
* @param hostname the specified hostname
* @return array of IP addresses for the requested host
* @throws UnknownHostException if no IP address for the {@code hostname} could be found
*/
public List<InetAddress> lookupAllHostAddr(String hostname) throws UnknownHostException {
// First try hosts file
// TODO: Add nsswitch.conf ReloadTracker and parser to select proper order
try {
return List.of(hostsFileResolver.getHostAddress(hostname));
} catch (UnknownHostException uhe) {
if (DEBUG) {
System.err.printf("Resolver API: Hosts file doesn't know '%s' host%n", hostname);
}
}
try {
var results = lookup(hostname, AddressFamily.ANY, false, true, 0);
if (results.isEmpty()) {
throw new UnknownHostException(hostname + " unknown host name");
}
return results;
} catch (DnsResolverException e) {
UnknownHostException uhe = new UnknownHostException(hostname);
uhe.initCause(e);
throw uhe;
}
}
/**
* Lookup the host name corresponding to the IP address provided.
*
* @param address the specified IP address
* @return {@code String} representing the host name
* @throws UnknownHostException if no host found for the specified IP address
*/
public String getHostByAddr(InetAddress address) throws UnknownHostException {
var results = getAllHostsByAddr(address);
return results.get(0);
}
/**
* Lookup all known host names which correspond to the IP address provided
*
* @param address the specified IP address
* @return array of {@code String} representing the host names
* @throws UnknownHostException if no host found for the specified IP address
*/
public List<String> getAllHostsByAddr(InetAddress address) throws UnknownHostException {
// First try hosts file
// TODO: Add nsswitch.conf to select proper order
try {
return List.of(hostsFileResolver.getByAddress(address));
} catch (UnknownHostException uhe) {
if (DEBUG) {
System.err.printf("Resolver API: No host in hosts file with %s address%n", address);
}
}
try {
var literalIP = addressToLiteralIP(address);
var family = AddressFamily.fromInetAddress(address);
var results = rlookup(literalIP, family);
if (results.isEmpty()) {
throw new UnknownHostException();
}
// remove trailing dot
return results.stream()
.map(host -> host.endsWith(".") ? host.substring(0, host.length() - 1) : host)
.collect(Collectors.toList());
} catch (DnsResolverException dre) {
UnknownHostException uhe = new UnknownHostException();
uhe.initCause(dre);
throw uhe;
}
}
private Set<String> prepareDomainsSearchList() {
var domainsToSearch = new LinkedHashSet<String>();
var domain = dnsResolverConfiguration.domain();
// First will try the domain
if (!domain.isBlank()) {
domainsToSearch.add(domain);
}
// Then will iterate over search list
domainsToSearch.addAll(dnsResolverConfiguration.searchlist());
if (DEBUG) {
System.out.printf("Domains search list:%s%n", domainsToSearch);
}
return domainsToSearch;
}
private List<InetAddress> lookup(String host, AddressFamily addressFamily, boolean oneIsEnough, boolean checkDomains, int depth) throws UnknownHostException, DnsResolverException {
if (DEBUG) {
System.out.printf("Resolver API: internal lookup call - %s%n", host);
}
// Will remain the same during DNS queries execution
ResourceClassType ct = ResourceClassType.fromAddressFamily(addressFamily);
ResourceRecords rrs = null;
// First try to get the resource records with the requested DNS host name if it is FQDN
if (host.contains(".")) {
rrs = execAddrResolutionQuery(new DnsName(host), ct);
}
// Non-FQDN or not known host address and domains still can be checked
if ((rrs == null || rrs.answer.isEmpty()) && checkDomains) {
for (String domain : prepareDomainsSearchList()) {
String hostWithSuffix = host + "." + domain;
if (DEBUG) {
System.err.printf("Resolver API: Trying to lookup:'%s'%n", hostWithSuffix);
}
rrs = execAddrResolutionQuery(new DnsName(hostWithSuffix), ct);
if (rrs != null && !rrs.answer.isEmpty()) {
if (DEBUG) {
System.err.printf("Resolver API: Found host in '%s' domain%n", domain);
}
break;
}
}
}
// If no answers then host is not known in registered domain
if (rrs == null || rrs.answer.isEmpty()) {
throw new UnknownHostException(host);
}
// Parse answers
List<InetAddress> results = new ArrayList<>();
for (int i = 0; i < rrs.answer.size(); i++) {
ResourceRecord rr = rrs.answer.elementAt(i);
int answerType = rr.getType();
String recordData = rr.getRdata().toString();
if (DEBUG) {
System.err.printf("Resolver API: Got %s type: %s%n", ResourceRecord.getTypeName(rr.getType()), rr.getRdata());
}
if (answerType == ResourceRecord.TYPE_CNAME) {
// We've got CNAME entry - issue another request to resolve the canonical host name
if (depth > MAX_CNAME_RESOLUTION_DEPTH) {
throw new UnknownHostException(host);
}
List<InetAddress> cnameResults = lookup(recordData, addressFamily, oneIsEnough, false, depth + 1);
if (oneIsEnough) {
return cnameResults;
} else {
results.addAll(cnameResults);
}
} else {
byte[] addrBytes;
if (answerType == ResourceRecord.TYPE_A && (addressFamily == AddressFamily.IPv4 || addressFamily == AddressFamily.ANY)) {
addrBytes = IPAddressUtil.textToNumericFormatV4(recordData);
if (addrBytes == null) {
if (DEBUG) {
System.err.println("Incorrect A resource record answer");
}
return Collections.emptyList();
}
} else if (answerType == ResourceRecord.TYPE_AAAA && (addressFamily == AddressFamily.IPv6 || addressFamily == AddressFamily.ANY)) {
addrBytes = IPAddressUtil.textToNumericFormatV6(recordData);
if (addrBytes == null) {
if (DEBUG) {
System.err.println("Incorrect AAAA resource record answer");
}
return Collections.emptyList();
}
} else {
continue;
}
// IPAddressUtil.textToNumeric can return null
if (addrBytes == null) {
throw new RuntimeException("Internal error");
}
InetAddress address = InetAddress.getByAddress(host, addrBytes);
results.add(address);
if (oneIsEnough) {
break;
}
}
}
return results;
}
// Can return null if query failed
private ResourceRecords execAddrResolutionQuery(DnsName name, ResourceClassType ct) {
// Not supporting authoritative requests [for now?]
try {
ResourceRecords rrs = dnsResolver.query(name, ct.getRecordClass(), ct.getRecordType(),
true, false);
return rrs.hasAddressOrAlias() ? rrs : null;
} catch (DnsResolverException e) {
if (DEBUG) {
System.err.println("Query failed:" + e.getMessage());
e.printStackTrace();
}
return null;
}
}
private List<String> rlookup(String literalIP, AddressFamily family) throws DnsResolverException {
switch (family) {
case IPv4:
return ipv4rlookup(literalIP);
case IPv6:
return ipv6rlookup(literalIP);
default:
throw new RuntimeException("Only IPv4 and IPv6 addresses are supported");
}
}
private List<String> ipv4rlookup(String literalIP) throws DnsResolverException {
var request = literalIP + "IN-ADDR.ARPA.";
var hostNames = new ArrayList<String>();
var name = new DnsName(request);
var rrs = dnsResolver.query(name, ResourceRecord.CLASS_INTERNET,
ResourceRecord.TYPE_PTR, true, false);
for (int i = 0; i < rrs.answer.size(); i++) {
ResourceRecord rr = rrs.answer.elementAt(i);
hostNames.add(rr.getRdata().toString());
}
return hostNames;
}
private List<String> ipv6rlookup(String literalIP) throws DnsResolverException {
List<String> hostNames = new ArrayList<>();
DnsName name = new DnsName(literalIP + "IP6.ARPA.");
ResourceRecords rrs = dnsResolver.query(name, ResourceRecord.CLASS_INTERNET,
ResourceRecord.TYPE_PTR, true, false);
/**
* Because RFC 3152 changed the root domain name for reverse
* lookups from IP6.INT. to IP6.ARPA., we need to check
* both. I.E. first the new one, IP6.ARPA, then if it fails
* the older one, IP6.INT
*/
if (rrs.answer.isEmpty()) {
name = new DnsName(literalIP + "IP6.INT.");
rrs = dnsResolver.query(name, ResourceRecord.CLASS_INTERNET,
ResourceRecord.TYPE_PTR, true, false);
}
for (int i = 0; i < rrs.answer.size(); i++) {
ResourceRecord rr = rrs.answer.elementAt(i);
hostNames.add(rr.getRdata().toString());
}
return hostNames;
}
private static String addressToLiteralIP(InetAddress address) {
byte[] bytes = address.getAddress();
StringBuilder addressBuff = new StringBuilder();
// IPv4 address
if (bytes.length == 4) {
for (int i = bytes.length - 1; i >= 0; i--) {
addressBuff.append(bytes[i] & 0xff);
addressBuff.append(".");
}
// IPv6 address
} else if (bytes.length == 16) {
for (int i = bytes.length - 1; i >= 0; i--) {
addressBuff.append(Integer.toHexString((bytes[i] & 0x0f)));
addressBuff.append(".");
addressBuff.append(Integer.toHexString((bytes[i] & 0xf0) >> 4));
addressBuff.append(".");
}
} else {
return null;
}
return addressBuff.toString();
}
private static DnsResolverConfiguration dnsResolverConfiguration = new DnsResolverConfiguration();
private static HostsFileResolver hostsFileResolver = new HostsFileResolver();
// TODO: Add system property with the sequence of resolution OR nsswitch.conf location to get the order:
// file, name
private final Resolver dnsResolver;
private static final boolean DEBUG = java.security.AccessController.doPrivileged(
(PrivilegedAction<Boolean>) () -> Boolean.getBoolean("jdk.dns.client.debug"));
private static final int MAX_CNAME_RESOLUTION_DEPTH = 4;
}