Java example source code file (DnsContext.java)
The DnsContext.java Java example source code/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* 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.
*
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package com.sun.jndi.dns;
import java.util.Enumeration;
import java.util.Hashtable;
import javax.naming.*;
import javax.naming.directory.*;
import javax.naming.spi.DirectoryManager;
import com.sun.jndi.toolkit.ctx.*;
/**
* A DnsContext is a directory context representing a DNS node.
*
* @author Scott Seligman
*/
public class DnsContext extends ComponentDirContext {
DnsName domain; // fully-qualified domain name of this context,
// with a root (empty) label at position 0
Hashtable<Object,Object> environment;
private boolean envShared; // true if environment is possibly shared
// and so must be copied on write
private boolean parentIsDns; // was this DnsContext created by
// another? see composeName()
private String[] servers;
private Resolver resolver;
private boolean authoritative; // must all responses be authoritative?
private boolean recursion; // request recursion on queries?
private int timeout; // initial timeout on UDP queries in ms
private int retries; // number of UDP retries
static final NameParser nameParser = new DnsNameParser();
// Timeouts for UDP queries use exponential backoff: each retry
// is for twice as long as the last. The following constants set
// the defaults for the initial timeout (in ms) and the number of
// retries, and name the environment properties used to override
// these defaults.
private static final int DEFAULT_INIT_TIMEOUT = 1000;
private static final int DEFAULT_RETRIES = 4;
private static final String INIT_TIMEOUT =
"com.sun.jndi.dns.timeout.initial";
private static final String RETRIES = "com.sun.jndi.dns.timeout.retries";
// The resource record type and class to use for lookups, and the
// property used to modify them
private CT lookupCT;
private static final String LOOKUP_ATTR = "com.sun.jndi.dns.lookup.attr";
// Property used to disallow recursion on queries
private static final String RECURSION = "com.sun.jndi.dns.recursion";
// ANY == ResourceRecord.QCLASS_STAR == ResourceRecord.QTYPE_STAR
private static final int ANY = ResourceRecord.QTYPE_STAR;
// The zone tree used for list operations
private static final ZoneNode zoneTree = new ZoneNode(null);
/**
* Returns a DNS context for a given domain and servers.
* Each server is of the form "server[:port]".
* IPv6 literal host names include delimiting brackets.
* There must be at least one server.
* The environment must not be null; it is cloned before being stored.
*/
@SuppressWarnings("unchecked")
public DnsContext(String domain, String[] servers, Hashtable<?,?> environment)
throws NamingException {
this.domain = new DnsName(domain.endsWith(".")
? domain
: domain + ".");
this.servers = (servers == null) ? null : servers.clone();
this.environment = (Hashtable<Object,Object>) environment.clone();
envShared = false;
parentIsDns = false;
resolver = null;
initFromEnvironment();
}
/*
* Returns a clone of a DNS context, just like DnsContext(DnsContext)
* but with a different domain name and with parentIsDns set to true.
*/
DnsContext(DnsContext ctx, DnsName domain) {
this(ctx);
this.domain = domain;
parentIsDns = true;
}
/*
* Returns a clone of a DNS context. The context's modifiable
* private state is independent of the original's (so closing one
* context, for example, won't close the other). The two contexts
* share <tt>environment, but it's copy-on-write so there's
* no conflict.
*/
private DnsContext(DnsContext ctx) {
environment = ctx.environment; // shared environment, copy-on-write
envShared = ctx.envShared = true;
parentIsDns = ctx.parentIsDns;
domain = ctx.domain;
servers = ctx.servers; // shared servers, no write operation
resolver = ctx.resolver;
authoritative = ctx.authoritative;
recursion = ctx.recursion;
timeout = ctx.timeout;
retries = ctx.retries;
lookupCT = ctx.lookupCT;
}
public void close() {
if (resolver != null) {
resolver.close();
resolver = null;
}
}
//---------- Environment operations
/*
* Override default with a noncloning version.
*/
protected Hashtable<?,?> p_getEnvironment() {
return environment;
}
public Hashtable<?,?> getEnvironment() throws NamingException {
return (Hashtable<?,?>) environment.clone();
}
@SuppressWarnings("unchecked")
public Object addToEnvironment(String propName, Object propVal)
throws NamingException {
if (propName.equals(LOOKUP_ATTR)) {
lookupCT = getLookupCT((String) propVal);
} else if (propName.equals(Context.AUTHORITATIVE)) {
authoritative = "true".equalsIgnoreCase((String) propVal);
} else if (propName.equals(RECURSION)) {
recursion = "true".equalsIgnoreCase((String) propVal);
} else if (propName.equals(INIT_TIMEOUT)) {
int val = Integer.parseInt((String) propVal);
if (timeout != val) {
timeout = val;
resolver = null;
}
} else if (propName.equals(RETRIES)) {
int val = Integer.parseInt((String) propVal);
if (retries != val) {
retries = val;
resolver = null;
}
}
if (!envShared) {
return environment.put(propName, propVal);
} else if (environment.get(propName) != propVal) {
// copy on write
environment = (Hashtable<Object,Object>) environment.clone();
envShared = false;
return environment.put(propName, propVal);
} else {
return propVal;
}
}
@SuppressWarnings("unchecked")
public Object removeFromEnvironment(String propName)
throws NamingException {
if (propName.equals(LOOKUP_ATTR)) {
lookupCT = getLookupCT(null);
} else if (propName.equals(Context.AUTHORITATIVE)) {
authoritative = false;
} else if (propName.equals(RECURSION)) {
recursion = true;
} else if (propName.equals(INIT_TIMEOUT)) {
if (timeout != DEFAULT_INIT_TIMEOUT) {
timeout = DEFAULT_INIT_TIMEOUT;
resolver = null;
}
} else if (propName.equals(RETRIES)) {
if (retries != DEFAULT_RETRIES) {
retries = DEFAULT_RETRIES;
resolver = null;
}
}
if (!envShared) {
return environment.remove(propName);
} else if (environment.get(propName) != null) {
// copy-on-write
environment = (Hashtable<Object,Object>) environment.clone();
envShared = false;
return environment.remove(propName);
} else {
return null;
}
}
/*
* Update PROVIDER_URL property. Call this only when environment
* is not being shared.
*/
void setProviderUrl(String url) {
// assert !envShared;
environment.put(Context.PROVIDER_URL, url);
}
/*
* Read environment properties and set parameters.
*/
private void initFromEnvironment()
throws InvalidAttributeIdentifierException {
lookupCT = getLookupCT((String) environment.get(LOOKUP_ATTR));
authoritative = "true".equalsIgnoreCase((String)
environment.get(Context.AUTHORITATIVE));
String val = (String) environment.get(RECURSION);
recursion = ((val == null) ||
"true".equalsIgnoreCase(val));
val = (String) environment.get(INIT_TIMEOUT);
timeout = (val == null)
? DEFAULT_INIT_TIMEOUT
: Integer.parseInt(val);
val = (String) environment.get(RETRIES);
retries = (val == null)
? DEFAULT_RETRIES
: Integer.parseInt(val);
}
private CT getLookupCT(String attrId)
throws InvalidAttributeIdentifierException {
return (attrId == null)
? new CT(ResourceRecord.CLASS_INTERNET, ResourceRecord.TYPE_TXT)
: fromAttrId(attrId);
}
//---------- Naming operations
public Object c_lookup(Name name, Continuation cont)
throws NamingException {
cont.setSuccess();
if (name.isEmpty()) {
DnsContext ctx = new DnsContext(this);
ctx.resolver = new Resolver(servers, timeout, retries);
// clone for parallelism
return ctx;
}
try {
DnsName fqdn = fullyQualify(name);
ResourceRecords rrs =
getResolver().query(fqdn, lookupCT.rrclass, lookupCT.rrtype,
recursion, authoritative);
Attributes attrs = rrsToAttrs(rrs, null);
DnsContext ctx = new DnsContext(this, fqdn);
return DirectoryManager.getObjectInstance(ctx, name, this,
environment, attrs);
} catch (NamingException e) {
cont.setError(this, name);
throw cont.fillInException(e);
} catch (Exception e) {
cont.setError(this, name);
NamingException ne = new NamingException(
"Problem generating object using object factory");
ne.setRootCause(e);
throw cont.fillInException(ne);
}
}
public Object c_lookupLink(Name name, Continuation cont)
throws NamingException {
return c_lookup(name, cont);
}
public NamingEnumeration<NameClassPair> c_list(Name name, Continuation cont)
throws NamingException {
cont.setSuccess();
try {
DnsName fqdn = fullyQualify(name);
NameNode nnode = getNameNode(fqdn);
DnsContext ctx = new DnsContext(this, fqdn);
return new NameClassPairEnumeration(ctx, nnode.getChildren());
} catch (NamingException e) {
cont.setError(this, name);
throw cont.fillInException(e);
}
}
public NamingEnumeration<Binding> c_listBindings(Name name, Continuation cont)
throws NamingException {
cont.setSuccess();
try {
DnsName fqdn = fullyQualify(name);
NameNode nnode = getNameNode(fqdn);
DnsContext ctx = new DnsContext(this, fqdn);
return new BindingEnumeration(ctx, nnode.getChildren());
} catch (NamingException e) {
cont.setError(this, name);
throw cont.fillInException(e);
}
}
public void c_bind(Name name, Object obj, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_rebind(Name name, Object obj, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_unbind(Name name, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_rename(Name oldname, Name newname, Continuation cont)
throws NamingException {
cont.setError(this, oldname);
throw cont.fillInException(
new OperationNotSupportedException());
}
public Context c_createSubcontext(Name name, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_destroySubcontext(Name name, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public NameParser c_getNameParser(Name name, Continuation cont)
throws NamingException {
cont.setSuccess();
return nameParser;
}
//---------- Directory operations
public void c_bind(Name name,
Object obj,
Attributes attrs,
Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_rebind(Name name,
Object obj,
Attributes attrs,
Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public DirContext c_createSubcontext(Name name,
Attributes attrs,
Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public Attributes c_getAttributes(Name name,
String[] attrIds,
Continuation cont)
throws NamingException {
cont.setSuccess();
try {
DnsName fqdn = fullyQualify(name);
CT[] cts = attrIdsToClassesAndTypes(attrIds);
CT ct = getClassAndTypeToQuery(cts);
ResourceRecords rrs =
getResolver().query(fqdn, ct.rrclass, ct.rrtype,
recursion, authoritative);
return rrsToAttrs(rrs, cts);
} catch (NamingException e) {
cont.setError(this, name);
throw cont.fillInException(e);
}
}
public void c_modifyAttributes(Name name,
int mod_op,
Attributes attrs,
Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public void c_modifyAttributes(Name name,
ModificationItem[] mods,
Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public NamingEnumeration<SearchResult> c_search(Name name,
Attributes matchingAttributes,
String[] attributesToReturn,
Continuation cont)
throws NamingException {
throw new OperationNotSupportedException();
}
public NamingEnumeration<SearchResult> c_search(Name name,
String filter,
SearchControls cons,
Continuation cont)
throws NamingException {
throw new OperationNotSupportedException();
}
public NamingEnumeration<SearchResult> c_search(Name name,
String filterExpr,
Object[] filterArgs,
SearchControls cons,
Continuation cont)
throws NamingException {
throw new OperationNotSupportedException();
}
public DirContext c_getSchema(Name name, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
public DirContext c_getSchemaClassDefinition(Name name, Continuation cont)
throws NamingException {
cont.setError(this, name);
throw cont.fillInException(
new OperationNotSupportedException());
}
//---------- Name-related operations
public String getNameInNamespace() {
return domain.toString();
}
public Name composeName(Name name, Name prefix) throws NamingException {
Name result;
// Any name that's not a CompositeName is assumed to be a DNS
// compound name. Convert each to a DnsName for syntax checking.
if (!(prefix instanceof DnsName || prefix instanceof CompositeName)) {
prefix = (new DnsName()).addAll(prefix);
}
if (!(name instanceof DnsName || name instanceof CompositeName)) {
name = (new DnsName()).addAll(name);
}
// Each of prefix and name is now either a DnsName or a CompositeName.
// If we have two DnsNames, simply join them together.
if ((prefix instanceof DnsName) && (name instanceof DnsName)) {
result = (DnsName) (prefix.clone());
result.addAll(name);
return new CompositeName().add(result.toString());
}
// Wrap compound names in composite names.
Name prefixC = (prefix instanceof CompositeName)
? prefix
: new CompositeName().add(prefix.toString());
Name nameC = (name instanceof CompositeName)
? name
: new CompositeName().add(name.toString());
int prefixLast = prefixC.size() - 1;
// Let toolkit do the work at namespace boundaries.
if (nameC.isEmpty() || nameC.get(0).equals("") ||
prefixC.isEmpty() || prefixC.get(prefixLast).equals("")) {
return super.composeName(nameC, prefixC);
}
result = (prefix == prefixC)
? (CompositeName) prefixC.clone()
: prefixC; // prefixC is already a clone
result.addAll(nameC);
if (parentIsDns) {
DnsName dnsComp = (prefix instanceof DnsName)
? (DnsName) prefix.clone()
: new DnsName(prefixC.get(prefixLast));
dnsComp.addAll((name instanceof DnsName)
? name
: new DnsName(nameC.get(0)));
result.remove(prefixLast + 1);
result.remove(prefixLast);
result.add(prefixLast, dnsComp.toString());
}
return result;
}
//---------- Helper methods
/*
* Resolver is not created until needed, to allow time for updates
* to the environment.
*/
private synchronized Resolver getResolver() throws NamingException {
if (resolver == null) {
resolver = new Resolver(servers, timeout, retries);
}
return resolver;
}
/*
* Returns the fully-qualified domain name of a name given
* relative to this context. Result includes a root label (an
* empty component at position 0).
*/
DnsName fullyQualify(Name name) throws NamingException {
if (name.isEmpty()) {
return domain;
}
DnsName dnsName = (name instanceof CompositeName)
? new DnsName(name.get(0)) // parse name
: (DnsName) (new DnsName()).addAll(name); // clone & check syntax
if (dnsName.hasRootLabel()) {
// Be overly generous and allow root label if we're in root domain.
if (domain.size() == 1) {
return dnsName;
} else {
throw new InvalidNameException(
"DNS name " + dnsName + " not relative to " + domain);
}
}
return (DnsName) dnsName.addAll(0, domain);
}
/*
* Converts resource records to an attribute set. Only resource
* records in the answer section are used, and only those that
* match the classes and types in cts (see classAndTypeMatch()
* for matching rules).
*/
private static Attributes rrsToAttrs(ResourceRecords rrs, CT[] cts) {
BasicAttributes attrs = new BasicAttributes(true);
for (int i = 0; i < rrs.answer.size(); i++) {
ResourceRecord rr = rrs.answer.elementAt(i);
int rrtype = rr.getType();
int rrclass = rr.getRrclass();
if (!classAndTypeMatch(rrclass, rrtype, cts)) {
continue;
}
String attrId = toAttrId(rrclass, rrtype);
Attribute attr = attrs.get(attrId);
if (attr == null) {
attr = new BasicAttribute(attrId);
attrs.put(attr);
}
attr.add(rr.getRdata());
}
return attrs;
}
/*
* Returns true if rrclass and rrtype match some element of cts.
* A match occurs if corresponding classes and types are equal,
* or if the array value is ANY. If cts is null, then any class
* and type match.
*/
private static boolean classAndTypeMatch(int rrclass, int rrtype,
CT[] cts) {
if (cts == null) {
return true;
}
for (int i = 0; i < cts.length; i++) {
CT ct = cts[i];
boolean classMatch = (ct.rrclass == ANY) ||
(ct.rrclass == rrclass);
boolean typeMatch = (ct.rrtype == ANY) ||
(ct.rrtype == rrtype);
if (classMatch && typeMatch) {
return true;
}
}
return false;
}
/*
* Returns the attribute ID for a resource record given its class
* and type. If the record is in the internet class, the
* corresponding attribute ID is the record's type name (or the
* integer type value if the name is not known). If the record is
* not in the internet class, the class name (or integer class
* value) is prepended to the attribute ID, separated by a space.
*
* A class or type value of ANY represents an indeterminate class
* or type, and is represented within the attribute ID by "*".
* For example, the attribute ID "IN *" represents
* any type in the internet class, and "* NS" represents an NS
* record of any class.
*/
private static String toAttrId(int rrclass, int rrtype) {
String attrId = ResourceRecord.getTypeName(rrtype);
if (rrclass != ResourceRecord.CLASS_INTERNET) {
attrId = ResourceRecord.getRrclassName(rrclass) + " " + attrId;
}
return attrId;
}
/*
* Returns the class and type values corresponding to an attribute
* ID. An indeterminate class or type is represented by ANY. See
* toAttrId() for the format of attribute IDs.
*
* @throws InvalidAttributeIdentifierException
* if class or type is unknown
*/
private static CT fromAttrId(String attrId)
throws InvalidAttributeIdentifierException {
if (attrId.equals("")) {
throw new InvalidAttributeIdentifierException(
"Attribute ID cannot be empty");
}
int rrclass;
int rrtype;
int space = attrId.indexOf(' ');
// class
if (space < 0) {
rrclass = ResourceRecord.CLASS_INTERNET;
} else {
String className = attrId.substring(0, space);
rrclass = ResourceRecord.getRrclass(className);
if (rrclass < 0) {
throw new InvalidAttributeIdentifierException(
"Unknown resource record class '" + className + '\'');
}
}
// type
String typeName = attrId.substring(space + 1);
rrtype = ResourceRecord.getType(typeName);
if (rrtype < 0) {
throw new InvalidAttributeIdentifierException(
"Unknown resource record type '" + typeName + '\'');
}
return new CT(rrclass, rrtype);
}
/*
* Returns an array of the classes and types corresponding to a
* set of attribute IDs. See toAttrId() for the format of
* attribute IDs, and classAndTypeMatch() for the format of the
* array returned.
*/
private static CT[] attrIdsToClassesAndTypes(String[] attrIds)
throws InvalidAttributeIdentifierException {
if (attrIds == null) {
return null;
}
CT[] cts = new CT[attrIds.length];
for (int i = 0; i < attrIds.length; i++) {
cts[i] = fromAttrId(attrIds[i]);
}
return cts;
}
/*
* Returns the most restrictive resource record class and type
* that may be used to query for records matching cts.
* See classAndTypeMatch() for matching rules.
*/
private static CT getClassAndTypeToQuery(CT[] cts) {
int rrclass;
int rrtype;
if (cts == null) {
// Query all records.
rrclass = ANY;
rrtype = ANY;
} else if (cts.length == 0) {
// No records are requested, but we need to ask for something.
rrclass = ResourceRecord.CLASS_INTERNET;
rrtype = ANY;
} else {
rrclass = cts[0].rrclass;
rrtype = cts[0].rrtype;
for (int i = 1; i < cts.length; i++) {
if (rrclass != cts[i].rrclass) {
rrclass = ANY;
}
if (rrtype != cts[i].rrtype) {
rrtype = ANY;
}
}
}
return new CT(rrclass, rrtype);
}
//---------- Support for list operations
/*
* Synchronization notes:
*
* Any access to zoneTree that walks the tree, whether it modifies
* the tree or not, is synchronized on zoneTree.
* [%%% Note: a read/write lock would allow increased concurrency.]
* The depth of a ZoneNode can thereafter be accessed without
* further synchronization. Access to other fields and methods
* should be synchronized on the node itself.
*
* A zone's contents is a NameNode tree that, once created, is never
* modified. The only synchronization needed is to ensure that it
* gets flushed into shared memory after being created, which is
* accomplished by ZoneNode.populate(). The contents are accessed
* via a soft reference, so a ZoneNode may be seen to be populated
* one moment and unpopulated the next.
*/
/*
* Returns the node in the zone tree corresponding to a
* fully-qualified domain name. If the desired portion of the
* tree has not yet been populated or has been outdated, a zone
* transfer is done to populate the tree.
*/
private NameNode getNameNode(DnsName fqdn) throws NamingException {
dprint("getNameNode(" + fqdn + ")");
// Find deepest related zone in zone tree.
ZoneNode znode;
DnsName zone;
synchronized (zoneTree) {
znode = zoneTree.getDeepestPopulated(fqdn);
}
dprint("Deepest related zone in zone tree: " +
((znode != null) ? znode.getLabel() : "[none]"));
NameNode topOfZone;
NameNode nnode;
if (znode != null) {
synchronized (znode) {
topOfZone = znode.getContents();
}
// If fqdn is in znode's zone, is not at a zone cut, and
// is current, we're done.
if (topOfZone != null) {
nnode = topOfZone.get(fqdn, znode.depth() + 1); // +1 for root
if ((nnode != null) && !nnode.isZoneCut()) {
dprint("Found node " + fqdn + " in zone tree");
zone = (DnsName)
fqdn.getPrefix(znode.depth() + 1); // +1 for root
boolean current = isZoneCurrent(znode, zone);
boolean restart = false;
synchronized (znode) {
if (topOfZone != znode.getContents()) {
// Zone was modified while we were examining it.
// All bets are off.
restart = true;
} else if (!current) {
znode.depopulate();
} else {
return nnode; // cache hit!
}
}
dprint("Zone not current; discarding node");
if (restart) {
return getNameNode(fqdn);
}
}
}
}
// Cache miss... do it the expensive way.
dprint("Adding node " + fqdn + " to zone tree");
// Find fqdn's zone and add it to the tree.
zone = getResolver().findZoneName(fqdn, ResourceRecord.CLASS_INTERNET,
recursion);
dprint("Node's zone is " + zone);
synchronized (zoneTree) {
znode = (ZoneNode) zoneTree.add(zone, 1); // "1" to skip root
}
// If znode is now populated we know -- because the first half of
// getNodeName() didn't find it -- that it was populated by another
// thread during this method call. Assume then that it's current.
synchronized (znode) {
topOfZone = znode.isPopulated()
? znode.getContents()
: populateZone(znode, zone);
}
// Desired node should now be in znode's populated zone. Find it.
nnode = topOfZone.get(fqdn, zone.size());
if (nnode == null) {
throw new ConfigurationException(
"DNS error: node not found in its own zone");
}
dprint("Found node in newly-populated zone");
return nnode;
}
/*
* Does a zone transfer to [re]populate a zone in the zone tree.
* Returns the zone's new contents.
*/
private NameNode populateZone(ZoneNode znode, DnsName zone)
throws NamingException {
dprint("Populating zone " + zone);
// assert Thread.holdsLock(znode);
ResourceRecords rrs =
getResolver().queryZone(zone,
ResourceRecord.CLASS_INTERNET, recursion);
dprint("zone xfer complete: " + rrs.answer.size() + " records");
return znode.populate(zone, rrs);
}
/*
* Determine if a ZoneNode's data is current.
* We base this on a comparison between the cached serial
* number and the latest SOA record.
*
* If there is no SOA record, znode is not (or is no longer) a zone:
* depopulate znode and return false.
*
* Since this method may perform a network operation, it is best
* to call it with znode unlocked. Caller must then note that the
* result may be outdated by the time this method returns.
*/
private boolean isZoneCurrent(ZoneNode znode, DnsName zone)
throws NamingException {
// former version: return !znode.isExpired();
if (!znode.isPopulated()) {
return false;
}
ResourceRecord soa =
getResolver().findSoa(zone, ResourceRecord.CLASS_INTERNET,
recursion);
synchronized (znode) {
if (soa == null) {
znode.depopulate();
}
return (znode.isPopulated() &&
znode.compareSerialNumberTo(soa) >= 0);
}
}
//---------- Debugging
private static final boolean debug = false;
private static final void dprint(String msg) {
if (debug) {
System.err.println("** " + msg);
}
}
}
//----------
/*
* A pairing of a resource record class and a resource record type.
* A value of ANY in either field represents an indeterminate value.
*/
class CT {
int rrclass;
int rrtype;
CT(int rrclass, int rrtype) {
this.rrclass = rrclass;
this.rrtype = rrtype;
}
}
//----------
/*
* Common base class for NameClassPairEnumeration and BindingEnumeration.
*/
abstract class BaseNameClassPairEnumeration<T> implements NamingEnumeration
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