/* * Copyright (c) 2000, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.jndi.dns; import java.io.IOException;import java.net.DatagramSocket;import java.net.DatagramPacket;import java.net.InetAddress;import java.net.Socket;import javax.naming.*; import java.util.Collections;import java.util.Map;import java.util.HashMap;import java.util.Set;import java.util.HashSet; // Some of this code began life as part of sun.javaos.net.DnsClient// originally by sritchie@eng 1/96. It was first hacked up for JNDI// use by caveh@eng 6/97. /** * The DnsClient class performs DNS client operations in support of DnsContext. * */ public class DnsClient { // DNS packet header field offsets private static final int IDENT_OFFSET = 0; private static final int FLAGS_OFFSET = 2; private static final int NUMQ_OFFSET = 4; private static final int NUMANS_OFFSET = 6; private static final int NUMAUTH_OFFSET = 8; private static final int NUMADD_OFFSET = 10; private static final int DNS_HDR_SIZE = 12; // DNS response codes private static final int NO_ERROR = 0; private static final int FORMAT_ERROR = 1; private static final int SERVER_FAILURE = 2; private static final int NAME_ERROR = 3; private static final int NOT_IMPL = 4; private static final int REFUSED = 5; private static final String[] rcodeDescription = { "No error", "DNS format error", "DNS server failure", "DNS name not found", "DNS operation not supported", "DNS service refused" }; private static final int DEFAULT_PORT = 53; private InetAddress[] servers; private int[] serverPorts; private int timeout; // initial timeout on UDP queries in ms private int retries; // number of UDP retries private DatagramSocket udpSocket; // Requests sent private Set<Integer> reqs; // Responses received private Map<Integer, byte[]> resps; //------------------------------------------------------------------------- /* * Each server is of the form "server[:port]". IPv6 literal host names * include delimiting brackets. * "timeout" is the initial timeout interval (in ms) for UDP queries, * and "retries" gives the number of retries per server. */ public DnsClient(String[] servers, int timeout, int retries) throws NamingException { this.timeout = timeout; this.retries = retries; try { udpSocket = new DatagramSocket(); } catch (java.net.SocketException e) { NamingException ne = new ConfigurationException(); ne.setRootCause(e); throw ne; } this.servers = new InetAddress[servers.length]; serverPorts = new int[servers.length]; for (int i = 0; i < servers.length; i++) { // Is optional port given? int colon = servers[i].indexOf(':', servers[i].indexOf(']') + 1); serverPorts[i] = (colon < 0) ? DEFAULT_PORT : Integer.parseInt(servers[i].substring(colon + 1)); String server = (colon < 0) ? servers[i] : servers[i].substring(0, colon); try { this.servers[i] = InetAddress.getByName(server); } catch (java.net.UnknownHostException e) { NamingException ne = new ConfigurationException( "Unknown DNS server: " + server); ne.setRootCause(e); throw ne; } } reqs = Collections.synchronizedSet(new HashSet<Integer>()); resps = Collections.synchronizedMap(new HashMap<Integer, byte[]>()); } protected void finalize() { close(); } // A lock to access the request and response queues in tandem. private Object queuesLock = new Object(); public void close() { udpSocket.close(); synchronized (queuesLock) { reqs.clear(); resps.clear(); } } private int ident = 0; // used to set the msg ID field private Object identLock = new Object(); /* * If recursion is true, recursion is requested on the query. * If auth is true, only authoritative responses are accepted; other * responses throw NameNotFoundException. */ ResourceRecords query(DnsName fqdn, int qclass, int qtype, boolean recursion, boolean auth) throws NamingException { int xid; synchronized (identLock) { ident = 0xFFFF & (ident + 1); xid = ident; } // enqueue the outstanding request reqs.add(xid); Packet pkt = makeQueryPacket(fqdn, xid, qclass, qtype, recursion); Exception caughtException = null; boolean[] doNotRetry = new boolean[servers.length]; // // The UDP retry strategy is to try the 1st server, and then // each server in order. If no answer, double the timeout // and try each server again. // for (int retry = 0; retry < retries; retry++) { // Try each name server. for (int i = 0; i < servers.length; i++) { if (doNotRetry[i]) { continue; } // send the request packet and wait for a response. try { if (debug) { dprint("SEND ID (" + (retry + 1) + "): " + xid); } byte[] msg = null; msg = doUdpQuery(pkt, servers[i], serverPorts[i], retry, xid); // // If the matching response is not got within the // given timeout, check if the response was enqueued // by some other thread, if not proceed with the next // server or retry. // if (msg == null) { if (resps.size() > 0) { msg = lookupResponse(xid); } if (msg == null) { // try next server or retry continue; } } Header hdr = new Header(msg, msg.length); if (auth && !hdr.authoritative) { caughtException = new NameNotFoundException( "DNS response not authoritative"); doNotRetry[i] = true; continue; } if (hdr.truncated) { // message is truncated -- try TCP // Try each server, starting with the one that just // provided the truncated message. for (int j = 0; j < servers.length; j++) { int ij = (i + j) % servers.length; if (doNotRetry[ij]) { continue; } try { Tcp tcp = new Tcp(servers[ij], serverPorts[ij]); byte[] msg2; try { msg2 = doTcpQuery(tcp, pkt); } finally { tcp.close(); } Header hdr2 = new Header(msg2, msg2.length); if (hdr2.query) { throw new CommunicationException( "DNS error: expecting response"); } checkResponseCode(hdr2); if (!auth || hdr2.authoritative) { // Got a valid response hdr = hdr2; msg = msg2; break; } else { doNotRetry[ij] = true; } } catch (Exception e) { // Try next server, or use UDP response } } // servers } return new ResourceRecords(msg, msg.length, hdr, false); } catch (IOException e) { if (debug) { dprint("Caught IOException:" + e); } if (caughtException == null) { caughtException = e; } // Use reflection to allow pre-1.4 compilation. // This won't be needed much longer. if (e.getClass().getName().equals( "java.net.PortUnreachableException")) { doNotRetry[i] = true; } } catch (NameNotFoundException e) { throw e; } catch (CommunicationException e) { if (caughtException == null) { caughtException = e; } } catch (NamingException e) { if (caughtException == null) { caughtException = e; } doNotRetry[i] = true; } } // servers } // retries reqs.remove(xid); if (caughtException instanceof NamingException) { throw (NamingException) caughtException; } // A network timeout or other error occurred. NamingException ne = new CommunicationException("DNS error"); ne.setRootCause(caughtException); throw ne; } ResourceRecords queryZone(DnsName zone, int qclass, boolean recursion) throws NamingException { int xid; synchronized (identLock) { ident = 0xFFFF & (ident + 1); xid = ident; } Packet pkt = makeQueryPacket(zone, xid, qclass, ResourceRecord.QTYPE_AXFR, recursion); Exception caughtException = null; // Try each name server. for (int i = 0; i < servers.length; i++) { try { Tcp tcp = new Tcp(servers[i], serverPorts[i]); byte[] msg; try { msg = doTcpQuery(tcp, pkt); Header hdr = new Header(msg, msg.length); // Check only rcode as per // draft-ietf-dnsext-axfr-clarify-04 checkResponseCode(hdr); ResourceRecords rrs = new ResourceRecords(msg, msg.length, hdr, true); if (rrs.getFirstAnsType() != ResourceRecord.TYPE_SOA) { throw new CommunicationException( "DNS error: zone xfer doesn't begin with SOA"); } if (rrs.answer.size() == 1 || rrs.getLastAnsType() != ResourceRecord.TYPE_SOA) { // The response is split into multiple DNS messages. do { msg = continueTcpQuery(tcp); if (msg == null) { throw new CommunicationException( "DNS error: incomplete zone transfer"); } hdr = new Header(msg, msg.length); checkResponseCode(hdr); rrs.add(msg, msg.length, hdr); } while (rrs.getLastAnsType() != ResourceRecord.TYPE_SOA); } // Delete the duplicate SOA record. rrs.answer.removeElementAt(rrs.answer.size() - 1); return rrs; } finally { tcp.close(); } } catch (IOException e) { caughtException = e; } catch (NameNotFoundException e) { throw e; } catch (NamingException e) { caughtException = e; } } if (caughtException instanceof NamingException) { throw (NamingException) caughtException; } NamingException ne = new CommunicationException( "DNS error during zone transfer"); ne.setRootCause(caughtException); throw ne; } /** * Tries to retreive an UDP packet matching the given xid * received within the timeout. * If a packet with different xid is received, the received packet * is enqueued with the corresponding xid in 'resps'. */ private byte[] doUdpQuery(Packet pkt, InetAddress server, int port, int retry, int xid) throws IOException, NamingException { int minTimeout = 50; // msec after which there are no retries. synchronized (udpSocket) { DatagramPacket opkt = new DatagramPacket( pkt.getData(), pkt.length(), server, port); DatagramPacket ipkt = new DatagramPacket(new byte[8000], 8000); udpSocket.connect(server, port); int pktTimeout = (timeout * (1 << retry)); try { udpSocket.send(opkt); // timeout remaining after successive 'receive()' int timeoutLeft = pktTimeout; int cnt = 0; do { if (debug) { cnt++; dprint("Trying RECEIVE(" + cnt + ") retry(" + (retry + 1) + ") for:" + xid + " sock-timeout:" + timeoutLeft + " ms."); } udpSocket.setSoTimeout(timeoutLeft); long start = System.currentTimeMillis(); udpSocket.receive(ipkt); long end = System.currentTimeMillis(); byte[] data = new byte[ipkt.getLength()]; data = ipkt.getData(); if (isMatchResponse(data, xid)) { return data; } timeoutLeft = pktTimeout - ((int) (end - start)); } while (timeoutLeft > minTimeout); } finally { udpSocket.disconnect(); } return null; // no matching packet received within the timeout } } /* * Sends a TCP query, and returns the first DNS message in the response. */ private byte[] doTcpQuery(Tcp tcp, Packet pkt) throws IOException { int len = pkt.length(); // Send 2-byte message length, then send message. tcp.out.write(len >> 8); tcp.out.write(len); tcp.out.write(pkt.getData(), 0, len); tcp.out.flush(); byte[] msg = continueTcpQuery(tcp); if (msg == null) { throw new IOException("DNS error: no response"); } return msg; } /* * Returns the next DNS message from the TCP socket, or null on EOF. */ private byte[] continueTcpQuery(Tcp tcp) throws IOException { int lenHi = tcp.in.read(); // high-order byte of response length if (lenHi == -1) { return null; // EOF } int lenLo = tcp.in.read(); // low-order byte of response length if (lenLo == -1) { throw new IOException("Corrupted DNS response: bad length"); } int len = (lenHi << 8) | lenLo; byte[] msg = new byte[len]; int pos = 0; // next unfilled position in msg while (len > 0) { int n = tcp.in.read(msg, pos, len); if (n == -1) { throw new IOException( "Corrupted DNS response: too little data"); } len -= n; pos += n; } return msg; } private Packet makeQueryPacket(DnsName fqdn, int xid, int qclass, int qtype, boolean recursion) { int qnameLen = fqdn.getOctets(); int pktLen = DNS_HDR_SIZE + qnameLen + 4; Packet pkt = new Packet(pktLen); short flags = recursion ? Header.RD_BIT : 0; pkt.putShort(xid, IDENT_OFFSET); pkt.putShort(flags, FLAGS_OFFSET); pkt.putShort(1, NUMQ_OFFSET); pkt.putShort(0, NUMANS_OFFSET); pkt.putInt(0, NUMAUTH_OFFSET); makeQueryName(fqdn, pkt, DNS_HDR_SIZE); pkt.putShort(qtype, DNS_HDR_SIZE + qnameLen); pkt.putShort(qclass, DNS_HDR_SIZE + qnameLen + 2); return pkt; } // Builds a query name in pkt according to the RFC spec. private void makeQueryName(DnsName fqdn, Packet pkt, int off) { // Loop through labels, least-significant first.Lines 1–500 of 699. Load more
/* * Copyright (c) 2000, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.jndi.dns; import java.io.IOException; import java.net.DatagramSocket; import java.net.DatagramPacket; import java.net.InetAddress; import java.net.Socket; import javax.naming.*; import java.util.Collections; import java.util.Map; import java.util.HashMap; import java.util.Set; import java.util.HashSet; // Some of this code began life as part of sun.javaos.net.DnsClient // originally by sritchie@eng 1/96. It was first hacked up for JNDI // use by caveh@eng 6/97. /** * The DnsClient class performs DNS client operations in support of DnsContext. * */ public class DnsClient { // DNS packet header field offsets private static final int IDENT_OFFSET = 0; private static final int FLAGS_OFFSET = 2; private static final int NUMQ_OFFSET = 4; private static final int NUMANS_OFFSET = 6; private static final int NUMAUTH_OFFSET = 8; private static final int NUMADD_OFFSET = 10; private static final int DNS_HDR_SIZE = 12; // DNS response codes private static final int NO_ERROR = 0; private static final int FORMAT_ERROR = 1; private static final int SERVER_FAILURE = 2; private static final int NAME_ERROR = 3; private static final int NOT_IMPL = 4; private static final int REFUSED = 5; private static final String[] rcodeDescription = { "No error", "DNS format error", "DNS server failure", "DNS name not found", "DNS operation not supported", "DNS service refused" }; private static final int DEFAULT_PORT = 53; private InetAddress[] servers; private int[] serverPorts; private int timeout; // initial timeout on UDP queries in ms private int retries; // number of UDP retries private DatagramSocket udpSocket; // Requests sent private Set<Integer> reqs; // Responses received private Map<Integer, byte[]> resps; //------------------------------------------------------------------------- /* * Each server is of the form "server[:port]". IPv6 literal host names * include delimiting brackets. * "timeout" is the initial timeout interval (in ms) for UDP queries, * and "retries" gives the number of retries per server. */ public DnsClient(String[] servers, int timeout, int retries) throws NamingException { this.timeout = timeout; this.retries = retries; try { udpSocket = new DatagramSocket(); } catch (java.net.SocketException e) { NamingException ne = new ConfigurationException(); ne.setRootCause(e); throw ne; } this.servers = new InetAddress[servers.length]; serverPorts = new int[servers.length]; for (int i = 0; i < servers.length; i++) { // Is optional port given? int colon = servers[i].indexOf(':', servers[i].indexOf(']') + 1); serverPorts[i] = (colon < 0) ? DEFAULT_PORT : Integer.parseInt(servers[i].substring(colon + 1)); String server = (colon < 0) ? servers[i] : servers[i].substring(0, colon); try { this.servers[i] = InetAddress.getByName(server); } catch (java.net.UnknownHostException e) { NamingException ne = new ConfigurationException( "Unknown DNS server: " + server); ne.setRootCause(e); throw ne; } } reqs = Collections.synchronizedSet(new HashSet<Integer>()); resps = Collections.synchronizedMap(new HashMap<Integer, byte[]>()); } protected void finalize() { close(); } // A lock to access the request and response queues in tandem. private Object queuesLock = new Object(); public void close() { udpSocket.close(); synchronized (queuesLock) { reqs.clear(); resps.clear(); } } private int ident = 0; // used to set the msg ID field private Object identLock = new Object(); /* * If recursion is true, recursion is requested on the query. * If auth is true, only authoritative responses are accepted; other * responses throw NameNotFoundException. */ ResourceRecords query(DnsName fqdn, int qclass, int qtype, boolean recursion, boolean auth) throws NamingException { int xid; synchronized (identLock) { ident = 0xFFFF & (ident + 1); xid = ident; } // enqueue the outstanding request reqs.add(xid); Packet pkt = makeQueryPacket(fqdn, xid, qclass, qtype, recursion); Exception caughtException = null; boolean[] doNotRetry = new boolean[servers.length]; // // The UDP retry strategy is to try the 1st server, and then // each server in order. If no answer, double the timeout // and try each server again. // for (int retry = 0; retry < retries; retry++) { // Try each name server. for (int i = 0; i < servers.length; i++) { if (doNotRetry[i]) { continue; } // send the request packet and wait for a response. try { if (debug) { dprint("SEND ID (" + (retry + 1) + "): " + xid); } byte[] msg = null; msg = doUdpQuery(pkt, servers[i], serverPorts[i], retry, xid); // // If the matching response is not got within the // given timeout, check if the response was enqueued // by some other thread, if not proceed with the next // server or retry. // if (msg == null) { if (resps.size() > 0) { msg = lookupResponse(xid); } if (msg == null) { // try next server or retry continue; } } Header hdr = new Header(msg, msg.length); if (auth && !hdr.authoritative) { caughtException = new NameNotFoundException( "DNS response not authoritative"); doNotRetry[i] = true; continue; } if (hdr.truncated) { // message is truncated -- try TCP // Try each server, starting with the one that just // provided the truncated message. for (int j = 0; j < servers.length; j++) { int ij = (i + j) % servers.length; if (doNotRetry[ij]) { continue; } try { Tcp tcp = new Tcp(servers[ij], serverPorts[ij]); byte[] msg2; try { msg2 = doTcpQuery(tcp, pkt); } finally { tcp.close(); } Header hdr2 = new Header(msg2, msg2.length); if (hdr2.query) { throw new CommunicationException( "DNS error: expecting response"); } checkResponseCode(hdr2); if (!auth || hdr2.authoritative) { // Got a valid response hdr = hdr2; msg = msg2; break; } else { doNotRetry[ij] = true; } } catch (Exception e) { // Try next server, or use UDP response } } // servers } return new ResourceRecords(msg, msg.length, hdr, false); } catch (IOException e) { if (debug) { dprint("Caught IOException:" + e); } if (caughtException == null) { caughtException = e; } // Use reflection to allow pre-1.4 compilation. // This won't be needed much longer. if (e.getClass().getName().equals( "java.net.PortUnreachableException")) { doNotRetry[i] = true; } } catch (NameNotFoundException e) { throw e; } catch (CommunicationException e) { if (caughtException == null) { caughtException = e; } } catch (NamingException e) { if (caughtException == null) { caughtException = e; } doNotRetry[i] = true; } } // servers } // retries reqs.remove(xid); if (caughtException instanceof NamingException) { throw (NamingException) caughtException; } // A network timeout or other error occurred. NamingException ne = new CommunicationException("DNS error"); ne.setRootCause(caughtException); throw ne; } ResourceRecords queryZone(DnsName zone, int qclass, boolean recursion) throws NamingException { int xid; synchronized (identLock) { ident = 0xFFFF & (ident + 1); xid = ident; } Packet pkt = makeQueryPacket(zone, xid, qclass, ResourceRecord.QTYPE_AXFR, recursion); Exception caughtException = null; // Try each name server. for (int i = 0; i < servers.length; i++) { try { Tcp tcp = new Tcp(servers[i], serverPorts[i]); byte[] msg; try { msg = doTcpQuery(tcp, pkt); Header hdr = new Header(msg, msg.length); // Check only rcode as per // draft-ietf-dnsext-axfr-clarify-04 checkResponseCode(hdr); ResourceRecords rrs = new ResourceRecords(msg, msg.length, hdr, true); if (rrs.getFirstAnsType() != ResourceRecord.TYPE_SOA) { throw new CommunicationException( "DNS error: zone xfer doesn't begin with SOA"); } if (rrs.answer.size() == 1 || rrs.getLastAnsType() != ResourceRecord.TYPE_SOA) { // The response is split into multiple DNS messages. do { msg = continueTcpQuery(tcp); if (msg == null) { throw new CommunicationException( "DNS error: incomplete zone transfer"); } hdr = new Header(msg, msg.length); checkResponseCode(hdr); rrs.add(msg, msg.length, hdr); } while (rrs.getLastAnsType() != ResourceRecord.TYPE_SOA); } // Delete the duplicate SOA record. rrs.answer.removeElementAt(rrs.answer.size() - 1); return rrs; } finally { tcp.close(); } } catch (IOException e) { caughtException = e; } catch (NameNotFoundException e) { throw e; } catch (NamingException e) { caughtException = e; } } if (caughtException instanceof NamingException) { throw (NamingException) caughtException; } NamingException ne = new CommunicationException( "DNS error during zone transfer"); ne.setRootCause(caughtException); throw ne; } /** * Tries to retreive an UDP packet matching the given xid * received within the timeout. * If a packet with different xid is received, the received packet * is enqueued with the corresponding xid in 'resps'. */ private byte[] doUdpQuery(Packet pkt, InetAddress server, int port, int retry, int xid) throws IOException, NamingException { int minTimeout = 50; // msec after which there are no retries. synchronized (udpSocket) { DatagramPacket opkt = new DatagramPacket( pkt.getData(), pkt.length(), server, port); DatagramPacket ipkt = new DatagramPacket(new byte[8000], 8000); udpSocket.connect(server, port); int pktTimeout = (timeout * (1 << retry)); try { udpSocket.send(opkt); // timeout remaining after successive 'receive()' int timeoutLeft = pktTimeout; int cnt = 0; do { if (debug) { cnt++; dprint("Trying RECEIVE(" + cnt + ") retry(" + (retry + 1) + ") for:" + xid + " sock-timeout:" + timeoutLeft + " ms."); } udpSocket.setSoTimeout(timeoutLeft); long start = System.currentTimeMillis(); udpSocket.receive(ipkt); long end = System.currentTimeMillis(); byte[] data = new byte[ipkt.getLength()]; data = ipkt.getData(); if (isMatchResponse(data, xid)) { return data; } timeoutLeft = pktTimeout - ((int) (end - start)); } while (timeoutLeft > minTimeout); } finally { udpSocket.disconnect(); } return null; // no matching packet received within the timeout } } /* * Sends a TCP query, and returns the first DNS message in the response. */ private byte[] doTcpQuery(Tcp tcp, Packet pkt) throws IOException { int len = pkt.length(); // Send 2-byte message length, then send message. tcp.out.write(len >> 8); tcp.out.write(len); tcp.out.write(pkt.getData(), 0, len); tcp.out.flush(); byte[] msg = continueTcpQuery(tcp); if (msg == null) { throw new IOException("DNS error: no response"); } return msg; } /* * Returns the next DNS message from the TCP socket, or null on EOF. */ private byte[] continueTcpQuery(Tcp tcp) throws IOException { int lenHi = tcp.in.read(); // high-order byte of response length if (lenHi == -1) { return null; // EOF } int lenLo = tcp.in.read(); // low-order byte of response length if (lenLo == -1) { throw new IOException("Corrupted DNS response: bad length"); } int len = (lenHi << 8) | lenLo; byte[] msg = new byte[len]; int pos = 0; // next unfilled position in msg while (len > 0) { int n = tcp.in.read(msg, pos, len); if (n == -1) { throw new IOException( "Corrupted DNS response: too little data"); } len -= n; pos += n; } return msg; } private Packet makeQueryPacket(DnsName fqdn, int xid, int qclass, int qtype, boolean recursion) { int qnameLen = fqdn.getOctets(); int pktLen = DNS_HDR_SIZE + qnameLen + 4; Packet pkt = new Packet(pktLen); short flags = recursion ? Header.RD_BIT : 0; pkt.putShort(xid, IDENT_OFFSET); pkt.putShort(flags, FLAGS_OFFSET); pkt.putShort(1, NUMQ_OFFSET); pkt.putShort(0, NUMANS_OFFSET); pkt.putInt(0, NUMAUTH_OFFSET); makeQueryName(fqdn, pkt, DNS_HDR_SIZE); pkt.putShort(qtype, DNS_HDR_SIZE + qnameLen); pkt.putShort(qclass, DNS_HDR_SIZE + qnameLen + 2); return pkt; } // Builds a query name in pkt according to the RFC spec. private void makeQueryName(DnsName fqdn, Packet pkt, int off) { // Loop through labels, least-significant first.