001/** 002 * 003 * Copyright 2013-2017 Florian Schmaus 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.jivesoftware.smack.util.dns; 018 019import java.net.InetAddress; 020import java.net.UnknownHostException; 021import java.util.Arrays; 022import java.util.List; 023import java.util.logging.Logger; 024 025import org.jivesoftware.smack.ConnectionConfiguration.DnssecMode; 026 027/** 028 * Implementations of this interface define a class that is capable of resolving DNS addresses. 029 * 030 */ 031public abstract class DNSResolver { 032 033 protected static final Logger LOGGER = Logger.getLogger(DNSResolver.class.getName()); 034 035 private final boolean supportsDnssec; 036 037 protected DNSResolver(boolean supportsDnssec) { 038 this.supportsDnssec = supportsDnssec; 039 } 040 041 /** 042 * Gets a list of service records for the specified service. 043 * @param name The symbolic name of the service. 044 * @return The list of SRV records mapped to the service name. 045 */ 046 public final List<SRVRecord> lookupSRVRecords(String name, List<HostAddress> failedAddresses, DnssecMode dnssecMode) { 047 checkIfDnssecRequestedAndSupported(dnssecMode); 048 return lookupSRVRecords0(name, failedAddresses, dnssecMode); 049 } 050 051 protected abstract List<SRVRecord> lookupSRVRecords0(String name, List<HostAddress> failedAddresses, DnssecMode dnssecMode); 052 053 public final HostAddress lookupHostAddress(String name, int port, List<HostAddress> failedAddresses, DnssecMode dnssecMode) { 054 checkIfDnssecRequestedAndSupported(dnssecMode); 055 List<InetAddress> inetAddresses = lookupHostAddress0(name, failedAddresses, dnssecMode); 056 if (inetAddresses == null || inetAddresses.isEmpty()) { 057 return null; 058 } 059 return new HostAddress(name, port, inetAddresses); 060 } 061 062 /** 063 * Lookup the IP addresses of a given host name. Returns <code>null</code> if there was an error, in which the error 064 * reason will be added in form of a <code>HostAddress</code> to <code>failedAddresses</code>. Returns a empty list 065 * in case the DNS name exists but has no associated A or AAAA resource records. Otherwise, if the resolution was 066 * successful <em>and</em> there is at least one A or AAAA resource record, then a non-empty list will be returned. 067 * <p> 068 * Concrete DNS resolver implementations are free to overwrite this, but have to stick to the interface contract. 069 * </p> 070 * 071 * @param name the DNS name to lookup 072 * @param failedAddresses a list with the failed addresses 073 * @param dnssecMode the selected DNSSEC mode 074 * @return A list, either empty or non-empty, or <code>null</code> 075 */ 076 protected List<InetAddress> lookupHostAddress0(String name, List<HostAddress> failedAddresses, DnssecMode dnssecMode) { 077 // Default implementation of a DNS name lookup for A/AAAA records. It is assumed that this method does never 078 // support DNSSEC. Subclasses are free to override this method. 079 if (dnssecMode != DnssecMode.disabled) { 080 throw new UnsupportedOperationException("This resolver does not support DNSSEC"); 081 } 082 083 InetAddress[] inetAddressArray; 084 try { 085 inetAddressArray = InetAddress.getAllByName(name); 086 } catch (UnknownHostException e) { 087 failedAddresses.add(new HostAddress(name, e)); 088 return null; 089 } 090 091 return Arrays.asList(inetAddressArray); 092 } 093 094 private final void checkIfDnssecRequestedAndSupported(DnssecMode dnssecMode) { 095 if (dnssecMode != DnssecMode.disabled && !supportsDnssec) { 096 throw new UnsupportedOperationException("This resolver does not support DNSSEC"); 097 } 098 } 099}