1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.hc.client5.http;
28
29 import java.net.IDN;
30 import java.net.InetAddress;
31 import java.net.UnknownHostException;
32
33 import org.apache.hc.core5.util.TextUtils;
34
35 /**
36 * DNS resolver that uses the default OS implementation for resolving host names.
37 *
38 * @since 4.2
39 */
40 public class SystemDefaultDnsResolver implements DnsResolver {
41
42 /**
43 * Default instance of {@link SystemDefaultDnsResolver}.
44 */
45 public static final SystemDefaultDnsResolver INSTANCE = new SystemDefaultDnsResolver();
46
47 @Override
48 public InetAddress[] resolve(final String host) throws UnknownHostException {
49 try {
50 String normalizedHost;
51 if (TextUtils.isAllASCII(host)) {
52 normalizedHost = host;
53 } else {
54 try {
55 normalizedHost = IDN.toASCII(host);
56 } catch (final IllegalArgumentException e) {
57 normalizedHost = host; // Fall back to original hostname
58 }
59 }
60 // Try resolving using the default resolver
61 return InetAddress.getAllByName(normalizedHost);
62 } catch (final UnknownHostException e) {
63 // If default resolver fails, try stripping the IPv6 zone ID and resolving again
64 String strippedHost = null;
65 if (host.charAt(0) == '[') {
66 final int i = host.lastIndexOf('%');
67 if (i != -1) {
68 strippedHost = host.substring(0, i) + "]";
69 }
70 }
71 if (strippedHost != null) {
72 return InetAddress.getAllByName(strippedHost);
73 }
74 throw e;
75 }
76 }
77
78 @Override
79 public String resolveCanonicalHostname(final String host) throws UnknownHostException {
80 if (host == null) {
81 return null;
82 }
83 final InetAddress in = InetAddress.getByName(host);
84 final String canonicalServer = in.getCanonicalHostName();
85 if (in.getHostAddress().contentEquals(canonicalServer)) {
86 return host;
87 }
88 return canonicalServer;
89 }
90 }