/*
* Finds the zone of a given domain name. The method is to look
* for the first SOA record on the path from the given domain to
* the root. This search may be partially bypassed if the zone's
* SOA record is received in the authority section of a response.
* If recursion is true, recursion is requested on any queries.
*/
DnsName findZoneName(DnsName fqdn, int rrclass, boolean recursion) throws NamingException {
fqdn = (DnsName) fqdn.clone();
while (fqdn.size() > 1) { // while below root
ResourceRecords rrs = null;
try {
rrs = query(fqdn, rrclass, ResourceRecord.TYPE_SOA, recursion, false);
} catch (NameNotFoundException e) {
throw e;
} catch (NamingException e) {
// Ignore error and keep searching up the tree.
}
if (rrs != null) {
if (rrs.answer.size() > 0) { // found zone's SOA
return fqdn;
}
// Look for an SOA record giving the zone's top node.
for (int i = 0; i < rrs.authority.size(); i++) {
ResourceRecord rr = (ResourceRecord) rrs.authority.elementAt(i);
if (rr.getType() == ResourceRecord.TYPE_SOA) {
DnsName zone = rr.getName();
if (fqdn.endsWith(zone)) {
return zone;
}
}
}
}
fqdn.remove(fqdn.size() - 1); // one step rootward
}
return fqdn; // no SOA found below root, so
// return root
}
/*
* Finds a zone's SOA record. Returns null if no SOA is found (in
* which case "zone" is not actually a zone).
* If recursion is true, recursion is requested on the query.
*/
ResourceRecord findSoa(DnsName zone, int rrclass, boolean recursion) throws NamingException {
ResourceRecords rrs = query(zone, rrclass, ResourceRecord.TYPE_SOA, recursion, false);
for (int i = 0; i < rrs.answer.size(); i++) {
ResourceRecord rr = (ResourceRecord) rrs.answer.elementAt(i);
if (rr.getType() == ResourceRecord.TYPE_SOA) {
return rr;
}
}
return null;
}
/*
* Finds the name servers of a zone. <tt>zone</tt> is a fully-qualified
* domain name at the top of a zone.
* If recursion is true, recursion is requested on the query.
*/
private String[] findNameServers(DnsName zone, boolean recursion) throws NamingException {
// %%% As an optimization, could look in authority section of
// findZoneName() response first.
ResourceRecords rrs =
query(zone, ResourceRecord.CLASS_INTERNET, ResourceRecord.TYPE_NS, recursion, false);
String[] ns = new String[rrs.answer.size()];
for (int i = 0; i < ns.length; i++) {
ResourceRecord rr = (ResourceRecord) rrs.answer.elementAt(i);
if (rr.getType() != ResourceRecord.TYPE_NS) {
throw new CommunicationException("Corrupted DNS message");
}
ns[i] = (String) rr.getRdata();
// Server name will be passed to InetAddress.getByName(), which
// may not be able to handle a trailing dot.
// assert ns[i].endsWith(".");
ns[i] = ns[i].substring(0, ns[i].length() - 1);
}
return ns;
}
