author | jjg |
Mon, 15 Aug 2011 11:48:20 -0700 | |
changeset 10336 | 0bb1999251f8 |
parent 5506 | 202f599c92aa |
permissions | -rw-r--r-- |
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/* |
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changeset
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* Copyright (c) 2006, 2011, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package sun.security.krb5; |
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import java.util.Arrays; |
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import java.util.Hashtable; |
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import java.util.Random; |
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import java.util.StringTokenizer; |
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import javax.naming.*; |
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import javax.naming.directory.*; |
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import javax.naming.spi.NamingManager; |
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/** |
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* This class discovers the location of Kerberos services by querying DNS, |
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* as defined in RFC 4120. |
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* |
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* @author Seema Malkani |
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* @since 1.7 |
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*/ |
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class KrbServiceLocator { |
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private static final String SRV_RR = "SRV"; |
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private static final String[] SRV_RR_ATTR = new String[] {SRV_RR}; |
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private static final String SRV_TXT = "TXT"; |
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private static final String[] SRV_TXT_ATTR = new String[] {SRV_TXT}; |
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private static final Random random = new Random(); |
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private KrbServiceLocator() { |
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} |
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/** |
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* Locates the KERBEROS service for a given domain. |
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* Queries DNS for a list of KERBEROS Service Text Records (TXT) for a |
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* given domain name. |
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* Information on the mapping of DNS hostnames and domain names |
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* to Kerberos realms is stored using DNS TXT records |
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* |
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* @param domainName A string domain name. |
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* @param environment The possibly null environment of the context. |
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* @return An ordered list of hostports for the Kerberos service or null if |
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* the service has not been located. |
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*/ |
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static String[] getKerberosService(String realmName) { |
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// search realm in SRV TXT records |
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String dnsUrl = "dns:///_kerberos." + realmName; |
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String[] records = null; |
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try { |
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// Create the DNS context using NamingManager rather than using |
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// the initial context constructor. This avoids having the initial |
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// context constructor call itself (when processing the URL |
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// argument in the getAttributes call). |
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0bb1999251f8
7064075: Security libraries don't build with javac -Xlint:all,-deprecation -Werror
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parents:
5506
diff
changeset
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Context ctx = NamingManager.getURLContext("dns", new Hashtable<>(0)); |
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if (!(ctx instanceof DirContext)) { |
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return null; // cannot create a DNS context |
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} |
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Attributes attrs = |
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((DirContext)ctx).getAttributes(dnsUrl, SRV_TXT_ATTR); |
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Attribute attr; |
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if (attrs != null && ((attr = attrs.get(SRV_TXT)) != null)) { |
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int numValues = attr.size(); |
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int numRecords = 0; |
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String[] txtRecords = new String[numValues]; |
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// gather the text records |
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int i = 0; |
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int j = 0; |
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while (i < numValues) { |
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try { |
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txtRecords[j] = (String)attr.get(i); |
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j++; |
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} catch (Exception e) { |
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// ignore bad value |
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} |
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i++; |
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} |
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numRecords = j; |
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// trim |
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if (numRecords < numValues) { |
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String[] trimmed = new String[numRecords]; |
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System.arraycopy(txtRecords, 0, trimmed, 0, numRecords); |
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records = trimmed; |
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} else { |
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records = txtRecords; |
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} |
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} |
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} catch (NamingException e) { |
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// ignore |
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} |
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return records; |
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} |
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/** |
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* Locates the KERBEROS service for a given domain. |
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* Queries DNS for a list of KERBEROS Service Location Records (SRV) for a |
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* given domain name. |
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* |
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* @param domainName A string domain name. |
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* @return An ordered list of hostports for the Kerberos service or null if |
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* the service has not been located. |
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*/ |
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static String[] getKerberosService(String realmName, String protocol) { |
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String dnsUrl = "dns:///_kerberos." + protocol + "." + realmName; |
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String[] hostports = null; |
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try { |
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// Create the DNS context using NamingManager rather than using |
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// the initial context constructor. This avoids having the initial |
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// context constructor call itself (when processing the URL |
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// argument in the getAttributes call). |
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10336
0bb1999251f8
7064075: Security libraries don't build with javac -Xlint:all,-deprecation -Werror
jjg
parents:
5506
diff
changeset
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Context ctx = NamingManager.getURLContext("dns", new Hashtable<>(0)); |
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if (!(ctx instanceof DirContext)) { |
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return null; // cannot create a DNS context |
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} |
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Attributes attrs = |
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((DirContext)ctx).getAttributes(dnsUrl, SRV_RR_ATTR); |
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Attribute attr; |
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if (attrs != null && ((attr = attrs.get(SRV_RR)) != null)) { |
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int numValues = attr.size(); |
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int numRecords = 0; |
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SrvRecord[] srvRecords = new SrvRecord[numValues]; |
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// create the service records |
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int i = 0; |
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int j = 0; |
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while (i < numValues) { |
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try { |
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srvRecords[j] = new SrvRecord((String) attr.get(i)); |
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j++; |
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} catch (Exception e) { |
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// ignore bad value |
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} |
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i++; |
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} |
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numRecords = j; |
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// trim |
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if (numRecords < numValues) { |
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SrvRecord[] trimmed = new SrvRecord[numRecords]; |
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System.arraycopy(srvRecords, 0, trimmed, 0, numRecords); |
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srvRecords = trimmed; |
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} |
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// Sort the service records in ascending order of their |
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// priority value. For records with equal priority, move |
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// those with weight 0 to the top of the list. |
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if (numRecords > 1) { |
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Arrays.sort(srvRecords); |
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} |
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// extract the host and port number from each service record |
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hostports = extractHostports(srvRecords); |
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} |
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} catch (NamingException e) { |
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// e.printStackTrace(); |
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// ignore |
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} |
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return hostports; |
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} |
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/** |
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* Extract hosts and port numbers from a list of SRV records. |
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* An array of hostports is returned or null if none were found. |
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*/ |
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private static String[] extractHostports(SrvRecord[] srvRecords) { |
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String[] hostports = null; |
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int head = 0; |
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int tail = 0; |
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int sublistLength = 0; |
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int k = 0; |
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for (int i = 0; i < srvRecords.length; i++) { |
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if (hostports == null) { |
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hostports = new String[srvRecords.length]; |
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} |
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// find the head and tail of the list of records having the same |
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// priority value. |
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head = i; |
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while (i < srvRecords.length - 1 && |
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srvRecords[i].priority == srvRecords[i + 1].priority) { |
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i++; |
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} |
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tail = i; |
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// select hostports from the sublist |
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sublistLength = (tail - head) + 1; |
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for (int j = 0; j < sublistLength; j++) { |
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hostports[k++] = selectHostport(srvRecords, head, tail); |
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} |
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} |
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return hostports; |
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} |
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/* |
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* Randomly select a service record in the range [head, tail] and return |
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* its hostport value. Follows the algorithm in RFC 2782. |
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*/ |
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private static String selectHostport(SrvRecord[] srvRecords, int head, |
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int tail) { |
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if (head == tail) { |
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return srvRecords[head].hostport; |
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} |
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// compute the running sum for records between head and tail |
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int sum = 0; |
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for (int i = head; i <= tail; i++) { |
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if (srvRecords[i] != null) { |
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sum += srvRecords[i].weight; |
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srvRecords[i].sum = sum; |
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} |
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} |
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String hostport = null; |
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// If all records have zero weight, select first available one; |
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// otherwise, randomly select a record according to its weight |
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int target = (sum == 0 ? 0 : random.nextInt(sum + 1)); |
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for (int i = head; i <= tail; i++) { |
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if (srvRecords[i] != null && srvRecords[i].sum >= target) { |
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hostport = srvRecords[i].hostport; |
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srvRecords[i] = null; // make this record unavailable |
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break; |
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} |
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} |
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return hostport; |
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} |
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/** |
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* This class holds a DNS service (SRV) record. |
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* See http://www.ietf.org/rfc/rfc2782.txt |
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*/ |
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||
10336
0bb1999251f8
7064075: Security libraries don't build with javac -Xlint:all,-deprecation -Werror
jjg
parents:
5506
diff
changeset
|
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static class SrvRecord implements Comparable<SrvRecord> { |
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int priority; |
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int weight; |
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int sum; |
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String hostport; |
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/** |
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* Creates a service record object from a string record. |
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* DNS supplies the string record in the following format: |
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* <pre> |
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* <Priority> " " <Weight> " " <Port> " " <Host> |
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* </pre> |
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*/ |
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SrvRecord(String srvRecord) throws Exception { |
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StringTokenizer tokenizer = new StringTokenizer(srvRecord, " "); |
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String port; |
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if (tokenizer.countTokens() == 4) { |
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priority = Integer.parseInt(tokenizer.nextToken()); |
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weight = Integer.parseInt(tokenizer.nextToken()); |
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port = tokenizer.nextToken(); |
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hostport = tokenizer.nextToken() + ":" + port; |
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} else { |
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throw new IllegalArgumentException(); |
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} |
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} |
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/* |
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* Sort records in ascending order of priority value. For records with |
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* equal priority move those with weight 0 to the top of the list. |
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*/ |
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10336
0bb1999251f8
7064075: Security libraries don't build with javac -Xlint:all,-deprecation -Werror
jjg
parents:
5506
diff
changeset
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public int compareTo(SrvRecord that) { |
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if (priority > that.priority) { |
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return 1; // this > that |
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} else if (priority < that.priority) { |
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return -1; // this < that |
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} else if (weight == 0 && that.weight != 0) { |
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return -1; // this < that |
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} else if (weight != 0 && that.weight == 0) { |
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return 1; // this > that |
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} else { |
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return 0; // this == that |
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} |
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} |
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} |
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} |