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Minimal DNS library for java and android systems
/*
* Copyright 2015-2016 the original author or authors
*
* This software is licensed under the Apache License, Version 2.0,
* the GNU Lesser General Public License version 2 or later ("LGPL")
* and the WTFPL.
* You may choose either license to govern your use of this software only
* upon the condition that you accept all of the terms of either
* the Apache License 2.0, the LGPL 2.1+ or the WTFPL.
*/
package de.measite.minidns;
import de.measite.minidns.Record.CLASS;
import de.measite.minidns.Record.TYPE;
import de.measite.minidns.cache.LRUCache;
import de.measite.minidns.record.A;
import de.measite.minidns.record.AAAA;
import de.measite.minidns.record.Data;
import de.measite.minidns.record.NS;
import de.measite.minidns.source.DNSDataSource;
import de.measite.minidns.source.NetworkDataSource;
import java.io.IOException;
import java.net.InetAddress;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Collections;
import java.util.HashSet;
import java.util.Random;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* A minimal DNS client for SRV/A/AAAA/NS and CNAME lookups, with IDN support.
* This circumvents the missing javax.naming package on android.
*/
public abstract class AbstractDNSClient {
protected static final LRUCache DEFAULT_CACHE = new LRUCache(1024);
protected static final Logger LOGGER = Logger.getLogger(AbstractDNSClient.class.getName());
/**
* The internal random class for sequence generation.
*/
protected final Random random;
protected final Random insecureRandom = new Random();
/**
* The internal DNS cache.
*/
protected final DNSCache cache;
protected DNSDataSource dataSource = new NetworkDataSource();
public enum IpVersionSetting {
v4only,
v6only,
v4v6,
v6v4,
;
}
protected static IpVersionSetting ipVersionSetting = IpVersionSetting.v4v6;
public static void setPreferedIpVersion(IpVersionSetting preferedIpVersion) {
if (preferedIpVersion == null) {
throw new IllegalArgumentException();
}
AbstractDNSClient.ipVersionSetting = preferedIpVersion;
}
/**
* Create a new DNS client with the given DNS cache.
*
* @param cache The backend DNS cache.
*/
protected AbstractDNSClient(DNSCache cache) {
Random random;
try {
random = SecureRandom.getInstance("SHA1PRNG");
} catch (NoSuchAlgorithmException e1) {
random = new SecureRandom();
}
this.random = random;
this.cache = cache;
}
/**
* Create a new DNS client using the global default cache.
*/
protected AbstractDNSClient() {
this(DEFAULT_CACHE);
}
/**
* Query the system nameservers for a single entry of any class.
*
* This can be used to determine the name server version, if name
* is version.bind, type is TYPE.TXT and clazz is CLASS.CH.
*
* @param name The DNS name to request.
* @param type The DNS type to request (SRV, A, AAAA, ...).
* @param clazz The class of the request (usually IN for Internet).
* @return The response (or null on timeout/error).
* @throws IOException if an IO error occurs.
*/
public final DNSMessage query(String name, TYPE type, CLASS clazz) throws IOException {
Question q = new Question(name, type, clazz);
return query(q);
}
/**
* Query the system nameservers for a single entry of the class IN
* (which is used for MX, SRV, A, AAAA and most other RRs).
*
* @param name The DNS name to request.
* @param type The DNS type to request (SRV, A, AAAA, ...).
* @return The response (or null on timeout/error).
* @throws IOException if an IO error occurs.
*/
public final DNSMessage query(DNSName name, TYPE type) throws IOException {
Question q = new Question(name, type, CLASS.IN);
return query(q);
}
/**
* Query the system nameservers for a single entry of the class IN
* (which is used for MX, SRV, A, AAAA and most other RRs).
*
* @param name The DNS name to request.
* @param type The DNS type to request (SRV, A, AAAA, ...).
* @return The response (or null on timeout/error).
* @throws IOException if an IO error occurs.
*/
public final DNSMessage query(CharSequence name, TYPE type) throws IOException {
Question q = new Question(name, type, CLASS.IN);
return query(q);
}
public DNSMessage query(Question q) throws IOException {
DNSMessage.Builder query = buildMessage(q);
return query(query);
}
/**
* Send a query request to the DNS system.
*
* @param query The query to send to the server.
* @return The response (or null).
* @throws IOException if an IO error occurs.
*/
protected abstract DNSMessage query(DNSMessage.Builder query) throws IOException;
public final DNSMessage query(Question q, InetAddress server, int port) throws IOException {
DNSMessage query = getQueryFor(q);
return query(query, server, port);
}
public final DNSMessage query(DNSMessage requestMessage, InetAddress address, int port) throws IOException {
// See if we have the answer to this question already cached
DNSMessage responseMessage = (cache == null) ? null : cache.get(requestMessage);
if (responseMessage != null) {
return responseMessage;
}
final Question q = requestMessage.getQuestion();
final Level TRACE_LOG_LEVEL = Level.FINE;
LOGGER.log(TRACE_LOG_LEVEL, "Asking {0} on {1} for {2} with:\n{3}", new Object[] { address, port, q, requestMessage });
try {
responseMessage = dataSource.query(requestMessage, address, port);
} catch (IOException e) {
LOGGER.log(TRACE_LOG_LEVEL, "IOException {0} on {1} while resolving {2}: {3}", new Object[] { address, port, q, e});
throw e;
}
if (responseMessage != null) {
LOGGER.log(TRACE_LOG_LEVEL, "Response from {0} on {1} for {2}:\n{3}", new Object[] { address, port, q, responseMessage });
} else {
// TODO When should this ever happen?
LOGGER.log(Level.SEVERE, "NULL response from " + address + " on " + port + " for " + q);
}
if (responseMessage == null) return null;
if (cache != null && isResponseCacheable(q, responseMessage)) {
cache.put(requestMessage.asNormalizedVersion(), responseMessage);
}
return responseMessage;
}
/**
* Whether a response from the DNS system should be cached or not.
*
* @param q The question the response message should answer.
* @param dnsMessage The response message received using the DNS client.
* @return True, if the response should be cached, false otherwise.
*/
protected boolean isResponseCacheable(Question q, DNSMessage dnsMessage) {
for (Record record : dnsMessage.answerSection) {
if (record.isAnswer(q)) {
return true;
}
}
return false;
}
/**
* Builds a {@link DNSMessage} object carrying the given Question.
*
* @param question {@link Question} to be put in the DNS request.
* @return A {@link DNSMessage} requesting the answer for the given Question.
*/
final DNSMessage.Builder buildMessage(Question question) {
DNSMessage.Builder message = DNSMessage.builder();
message.setQuestion(question);
message.setId(random.nextInt());
message = newQuestion(message);
return message;
}
protected abstract DNSMessage.Builder newQuestion(DNSMessage.Builder questionMessage);
/**
* Query a nameserver for a single entry.
*
* @param name The DNS name to request.
* @param type The DNS type to request (SRV, A, AAAA, ...).
* @param clazz The class of the request (usually IN for Internet).
* @param address The DNS server address.
* @param port The DNS server port.
* @return The response (or null on timeout / failure).
* @throws IOException On IO Errors.
*/
public DNSMessage query(String name, TYPE type, CLASS clazz, InetAddress address, int port)
throws IOException {
Question q = new Question(name, type, clazz);
return query(q, address, port);
}
/**
* Query a nameserver for a single entry.
*
* @param name The DNS name to request.
* @param type The DNS type to request (SRV, A, AAAA, ...).
* @param clazz The class of the request (usually IN for Internet).
* @param address The DNS server host.
* @return The response (or null on timeout / failure).
* @throws IOException On IO Errors.
*/
public DNSMessage query(String name, TYPE type, CLASS clazz, InetAddress address)
throws IOException {
Question q = new Question(name, type, clazz);
return query(q, address);
}
public final DNSMessage query(DNSMessage query, InetAddress host) throws IOException {
return query(query, host, 53);
}
/**
* Query a specific server for one entry.
*
* @param q The question section of the DNS query.
* @param address The dns server address.
* @return The response (or null on timeout/error).
* @throws IOException On IOErrors.
*/
public DNSMessage query(Question q, InetAddress address) throws IOException {
return query(q, address, 53);
}
/**
* Returns the currently used {@link DNSDataSource}. See {@link #setDataSource(DNSDataSource)} for details.
*
* @return The currently used {@link DNSDataSource}
*/
public DNSDataSource getDataSource() {
return dataSource;
}
/**
* Set a {@link DNSDataSource} to be used by the DNSClient.
* The default implementation will direct all queries directly to the Internet.
*
* This can be used to define a non-default handling for outgoing data. This can be useful to redirect the requests
* to a proxy or to modify requests after or responses before they are handled by the DNSClient implementation.
*
* @param dataSource An implementation of DNSDataSource that shall be used.
*/
public void setDataSource(DNSDataSource dataSource) {
if (dataSource == null) {
throw new IllegalArgumentException();
}
this.dataSource = dataSource;
}
/**
* Get the cache used by this DNS client.
*
* @return the cached used by this DNS client or null.
*/
public DNSCache getCache() {
return cache;
}
protected DNSMessage getQueryFor(Question q) {
DNSMessage.Builder messageBuilder = buildMessage(q);
DNSMessage query = messageBuilder.build();
return query;
}
private Set getCachedRecordsFor(DNSName dnsName, TYPE type) {
Question dnsNameNs = new Question(dnsName, type);
DNSMessage queryDnsNameNs = getQueryFor(dnsNameNs);
DNSMessage cachedResult = cache.get(queryDnsNameNs);
if (cachedResult == null)
return Collections.emptySet();
return cachedResult.getAnswersFor(dnsNameNs);
}
public Set getCachedNameserverRecordsFor(DNSName dnsName) {
return getCachedRecordsFor(dnsName, TYPE.NS);
}
public Set getCachedIPv4AddressesFor(DNSName dnsName) {
return getCachedRecordsFor(dnsName, TYPE.A);
}
public Set getCachedIPv6AddressesFor(DNSName dnsName) {
return getCachedRecordsFor(dnsName, TYPE.AAAA);
}
@SuppressWarnings("unchecked")
private Set getCachedIPNameserverAddressesFor(DNSName dnsName, TYPE type) {
Set nsSet = getCachedNameserverRecordsFor(dnsName);
if (nsSet.isEmpty())
return Collections.emptySet();
Set res = new HashSet<>(3 * nsSet.size());
for (NS ns : nsSet) {
Set addresses;
switch (type) {
case A:
addresses = (Set) getCachedIPv4AddressesFor(ns.name);
break;
case AAAA:
addresses = (Set) getCachedIPv6AddressesFor(ns.name);
break;
default:
throw new AssertionError();
}
res.addAll(addresses);
}
return res;
}
public Set getCachedIPv4NameserverAddressesFor(DNSName dnsName) {
return getCachedIPNameserverAddressesFor(dnsName, TYPE.A);
}
public Set getCachedIPv6NameserverAddressesFor(DNSName dnsName) {
return getCachedIPNameserverAddressesFor(dnsName, TYPE.AAAA);
}
}