/*
* Copyright (c) 2002, 2010, 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 sun.net.dns;
import java.util.List;
import java.util.LinkedList;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
/*
* An implementation of ResolverConfiguration for Solaris
* and Linux.
*/
public class ResolverConfigurationImpl
extends ResolverConfiguration
{
// Lock helds whilst loading configuration or checking
private static Object lock = new Object();
// Time of last refresh.
private static long lastRefresh = -1;
// Cache timeout (300 seconds) - should be converted into property
// or configured as preference in the future.
private static final int TIMEOUT = 300000;
// Resolver options
private final Options opts;
// Parse /etc/resolv.conf to get the values for a particular
// keyword.
//
private LinkedList<String> resolvconf(String keyword,
int maxperkeyword,
int maxkeywords)
{
LinkedList<String> ll = new LinkedList<>();
try {
BufferedReader in =
new BufferedReader(new FileReader("/etc/resolv.conf"));
String line;
while ((line = in.readLine()) != null) {
int maxvalues = maxperkeyword;
if (line.length() == 0)
continue;
if (line.charAt(0) == '#' || line.charAt(0) == ';')
continue;
if (!line.startsWith(keyword))
continue;
String value = line.substring(keyword.length());
if (value.length() == 0)
continue;
if (value.charAt(0) != ' ' && value.charAt(0) != '\t')
continue;
StringTokenizer st = new StringTokenizer(value, " \t");
while (st.hasMoreTokens()) {
String val = st.nextToken();
if (val.charAt(0) == '#' || val.charAt(0) == ';') {
break;
}
ll.add(val);
if (--maxvalues == 0) {
break;
}
}
if (--maxkeywords == 0) {
break;
}
}
in.close();
} catch (IOException ioe) {
// problem reading value
}
return ll;
}
private LinkedList<String> searchlist;
private LinkedList<String> nameservers;
// Load DNS configuration from OS
private void loadConfig() {
assert Thread.holdsLock(lock);
// check if cached settings have expired.
if (lastRefresh >= 0) {
long currTime = System.currentTimeMillis();
if ((currTime - lastRefresh) < TIMEOUT) {
return;
}
}
// get the name servers from /etc/resolv.conf
nameservers =
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<LinkedList<String>>() {
public LinkedList<String> run() {
// typically MAXNS is 3 but we've picked 5 here
// to allow for additional servers if required.
return resolvconf("nameserver", 1, 5);
} /* run */
});
// get the search list (or domain)
searchlist = getSearchList();
// update the timestamp on the configuration
lastRefresh = System.currentTimeMillis();
}
// obtain search list or local domain
private LinkedList<String> getSearchList() {
LinkedList<String> sl;
// first try the search keyword in /etc/resolv.conf
sl = java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<LinkedList<String>>() {
public LinkedList<String> run() {
LinkedList ll;
// first try search keyword (max 6 domains)
ll = resolvconf("search", 6, 1);
if (ll.size() > 0) {
return ll;
}
return null;
} /* run */
});
if (sl != null) {
return sl;
}
// No search keyword so use local domain
// LOCALDOMAIN has absolute priority on Solaris
String localDomain = localDomain0();
if (localDomain != null && localDomain.length() > 0) {
sl = new LinkedList();
sl.add(localDomain);
return sl;
}
// try domain keyword in /etc/resolv.conf
sl = java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<LinkedList<String>>() {
public LinkedList<String> run() {
LinkedList<String> ll;
ll = resolvconf("domain", 1, 1);
if (ll.size() > 0) {
return ll;
}
return null;
} /* run */
});
if (sl != null) {
return sl;
}
// no local domain so try fallback (RPC) domain or
// hostname
sl = new LinkedList<>();
String domain = fallbackDomain0();
if (domain != null && domain.length() > 0) {
sl.add(domain);
}
return sl;
}
// ----
ResolverConfigurationImpl() {
opts = new OptionsImpl();
}
public List<String> searchlist() {
synchronized (lock) {
loadConfig();
// List is mutable so return a shallow copy
return (List)searchlist.clone();
}
}
public List<String> nameservers() {
synchronized (lock) {
loadConfig();
// List is mutable so return a shallow copy
return (List)nameservers.clone();
}
}
public Options options() {
return opts;
}
// --- Native methods --
static native String localDomain0();
static native String fallbackDomain0();
static {
java.security.AccessController.doPrivileged(
new sun.security.action.LoadLibraryAction("net"));
}
}
/**
* Implementation of {@link ResolverConfiguration.Options}
*/
class OptionsImpl extends ResolverConfiguration.Options {
}