diff -aur dnsjava-1.2.3/org/xbill/DNS/Zone.java dnsjava-devel/org/xbill/DNS/Zone.java
--- dnsjava-1.2.3/org/xbill/DNS/Zone.java	Wed Mar 14 20:49:55 2001
+++ dnsjava-devel/org/xbill/DNS/Zone.java	Mon Feb 11 23:31:13 2002
@@ -15,6 +15,14 @@
 
 public class Zone extends NameSet {
 
+    private static final int FIRSTSOA = 0;
+    private static final int SECONDSOA = 1;
+    private static final int ADD = 2;
+    private static final int DEL = 3;
+    private static final int LASTSOA = 4;
+    private static final int DONE = 5;
+    private static final int AXFR = 6;
+
 class AXFREnumeration implements Enumeration {
 	private Enumeration znames;
 	private Name currentName;
@@ -173,6 +181,11 @@
 	Record rec = Record.newRecord(zone, Type.AXFR, dclass);
 	Message query = Message.newQuery(rec);
 	Message response = res.send(query);
+
+	if (response.getHeader().getRcode() != Rcode.NOERROR) {
+	    // XXX uh, oh.  we fux0red up. return an error!
+	}
+
 	Record [] recs = response.getSectionArray(Section.ANSWER);
 	for (int i = 0; i < recs.length; i++) {
 		if (!recs[i].getName().subdomain(origin)) {
@@ -191,6 +204,114 @@
 	validate();
 }
 
+    /** Perform an IXFR (if possible) to update the zone. 
+      @return false if unsuccessful, true if updated. 
+      non-success may be because unsupported! */
+    public boolean updateZone(String remote, Cache cache)
+	throws IOException
+    {
+	Resolver res = new SimpleResolver(remote);
+	Record rec = Record.newRecord(origin, Type.IXFR, dclass);
+	Message query = Message.newQuery(rec);
+        query.addRecord(getSOA(), Section.AUTHORITY);
+	Message response = res.send(query);
+
+	if (response.getHeader().getRcode() == Rcode.NOTIMPL) {
+		// IXFR not supported.  try again as an AXFR.
+        	rec = Record.newRecord(origin, Type.AXFR, dclass);
+        	query = Message.newQuery(rec);
+        	response = res.send(query);
+	}
+
+	if (response.getHeader().getRcode() != Rcode.NOERROR)
+	    return false; // uh, oh.  we fux0red up. return an error!
+
+	// XXX what about other errors? permission, etc?
+
+	Record [] recs = response.getSectionArray(Section.ANSWER);
+
+	// check for UDP overflow.
+        if ((response.getHeader().getFlag(Flags.TC) == true) || 
+	    ((recs.length == 1) && (recs[0].getType() == Type.SOA))) {
+	    SOARecord r = (SOARecord) recs[0];
+	    return (r.getSerial() <= getSOA().getSerial());
+	    // if >, then it needs updating. otherwise we're okay.
+	}
+
+	SOARecord oldSOA = getSOA();
+	SOARecord newSOA = null;
+	
+	int state = FIRSTSOA;
+
+	// we're getting a successful IXFR! 
+	for (int i = 0; i < recs.length; i++) {
+	    if (!recs[i].getName().subdomain(origin)) {
+		if (Options.check("verbose"))
+		    System.err.println(recs[i].getName() +
+				       "is not in zone " + origin);
+		continue;
+	    }
+	    
+	    // now for the state machine.
+	    switch(state) {
+	    case FIRSTSOA: {
+		newSOA = (SOARecord) recs[i];
+		state = SECONDSOA;
+		break;
+	    }
+	    case SECONDSOA: {
+		Record r = recs[i];
+		if (! (r instanceof SOARecord)) {
+		    clear();
+		    addRecord(r);
+		    state = AXFR;
+		} else {
+		    state = DEL;
+		    deleteRecord(r);
+		}
+	    }
+	    case DEL: {
+		Record r = recs[i];
+		if (r instanceof SOARecord) {
+		    state = ADD;
+		    addRecord(r);
+		} else {
+		    deleteRecord(r);
+		}
+	    }
+	    case ADD: {
+		Record r = recs[i];
+		if (r instanceof SOARecord) {
+		    SOARecord x = (SOARecord) r;
+		    if (x.getSerial() == newSOA.getSerial()) {
+			addRecord(r);
+			state = DONE;
+		    } else {
+			state = DEL;
+			deleteRecord(r);
+		    }
+		} else {
+		    addRecord(r);
+		}
+	    }
+	    case AXFR: {
+		Record r = recs[i];
+		addRecord(r);
+	    }
+	    case DONE: {
+		// XXX wtF?  nothing should get here.
+	    }
+	    } // end switch 
+	}
+	if (cache != null) {
+		recs = response.getSectionArray(Section.ADDITIONAL);
+		for (int i = 0; i < recs.length; i++)
+			cache.addRecord(recs[i], Credibility.ZONE_GLUE, recs);
+	}
+	validate();
+	return true;
+}
+
 /** Returns the Zone's origin */
 public Name
 getOrigin() {
@@ -326,6 +447,22 @@
 	rrset.addRR(r);
 }
 
+/**
+ * Deletes a record from the Zone
+ * @param r The record to be deleted
+ * @see Record
+ */ 
+public void 
+deleteRecord(Record r) {
+	Name name = r.getName();
+	short type = r.getRRsetType();
+	RRset rrset = (RRset) findExactSet (name, type);
+	if (rrset == null)
+	        return;
+	else
+	        rrset.deleteRR(r);
+}
+
 public Enumeration
 AXFR() {
 	return new AXFREnumeration();