packet.php

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<?php
/*
 *  License Information:
 *
 *    Net_DNS:  A resolver library for PHP
 *    Copyright (c) 2002-2003 Eric Kilfoil [e-mail]
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation; either
 *    version 2.1 of the License, or (at your option) any later version.
 *
 *    This library 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
 *    Lesser General Public License for more details.
 *
 *    You should have received a copy of the GNU Lesser General Public
 *    License along with this library; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/* Net_DNS_Packet object definition {{{ */
/**
 * A object represation of a DNS packet (RFC1035)
 *
 * This object is used to manage a DNS packet.  It contains methods for
 * DNS packet compression as defined in RFC1035, as well as parsing  a DNS
 * packet response from a DNS server, or building a DNS packet from  the
 * instance variables contained in the class.
 *
 * @package Net_DNS
 */
class Net_DNS_Packet
{
    /* class variable definitions {{{ */
    /**
     * debugging flag
     *
     * If set to TRUE (non-zero), debugging code will be displayed as the
     * packet is parsed.
     *
     * @var boolean $debug
     * @access  public
     */
    var $debug;
    /**
     * A packet Header object.
     *
     * An object of type Net_DNS_Header which contains the header
     * information  of the packet.
     *
     * @var object Net_DNS_Header $header
     * @access  public
     */
    var $header;
    /**
     * A hash of compressed labels
     *
     * A list of all labels which have been compressed in the DNS packet
     * and  the location offset of the label within the packet.
     *
     * @var array   $compnames
     */
    var $compnames;
    /**
     * The origin of the packet, if the packet is a server response.
     *
     * This contains a string containing the IP address of the name server
     * from which the answer was given.
     *
     * @var string  $answerfrom
     * @access  public
     */
    var $answerfrom;
    /**
     * The size of the answer packet, if the packet is a server response.
     *
     * This contains a integer containing the size of the DNS packet the
     * server responded with if this packet was received by a DNS server
     * using the query() method.
     *
     * @var string  $answersize
     * @access  public
     */
    var $answersize;
    /**
     * An array of Net_DNS_Question objects
     *
     * Contains all of the questions within the packet.  Each question is
     * stored as an object of type Net_DNS_Question.
     *
     * @var array   $question
     * @access  public
     */
    var $question;
    /**
     * An array of Net_DNS_RR ANSWER objects
     *
     * Contains all of the answer RRs within the packet.  Each answer is
     * stored as an object of type Net_DNS_RR.
     *
     * @var array   $answer
     * @access  public
     */
    var $answer;
    /**
     * An array of Net_DNS_RR AUTHORITY objects
     *
     * Contains all of the authority RRs within the packet.  Each authority is
     * stored as an object of type Net_DNS_RR.
     *
     * @var array   $authority
     * @access  public
     */
    var $authority;
    /**
     * An array of Net_DNS_RR ADDITIONAL objects
     *
     * Contains all of the additional RRs within the packet.  Each additional is
     * stored as an object of type Net_DNS_RR.
     *
     * @var array   $additional
     * @access  public
     */
    var $additional;

    /* }}} */
    /* class constructor - Net_DNS_Packet($debug = FALSE) {{{ */
    /*
     * unfortunately (or fortunately), we can't follow the same
     * silly method for determining if name is a hostname or a packet
     * stream in PHP, since there is no ref() function.  So we're going
     * to define a new method called parse to deal with this
     * circumstance and another method called buildQuestion to build a question.
     * I like it better that way anyway.
     */
    /**
     * Initalizes a Net_DNS_Packet object
     *
     * @param boolean $debug Turns debugging on or off
     */
    function Net_DNS_Packet($debug = FALSE)
    {
        $this->debug = $debug;
        $this->compnames = array();
    }

    /* }}} */
    /* Net_DNS_Packet::buildQuestion($name, $type = "A", $class = "IN") {{{ */
    /**
     * Adds a DNS question to the DNS packet
     *
     * @param   string $name    The name of the record to query
     * @param   string $type    The type of record to query
     * @param   string $class   The class of record to query
     * @see Net_DNS::typesbyname(), Net_DNS::classesbyname()
     */
    function buildQuestion($name, $type = 'A', $class = 'IN')
    {
        $this->header = new Net_DNS_Header();
        $this->header->qdcount = 1;
        $this->question[0] = new Net_DNS_Question($name, $type, $class);
        $this->answer = NULL;
        $this->authority = NULL;
        $this->additional = NULL;
        if ($this->debug) {
            $this->display();
        }
    }

    /* }}} */
    /* Net_DNS_Packet::parse($data) {{{ */
    /**
     * Parses a DNS packet returned by a DNS server
     *
     * Parses a complete DNS packet and builds an object hierarchy
     * containing all of the parts of the packet:
     * <ul>
     *   <li>HEADER   
     *   <li>QUESTION   
     *   <li>ANSWER || PREREQUISITE   
     *   <li>ADDITIONAL || UPDATE   
     *   <li>AUTHORITY
     * </ul>
     * 
     * @param string $data  A binary string containing a DNS packet
     * @return boolean TRUE on success, NULL on parser error
     */
    function parse($data)
    {
        if ($this->debug) {
            echo ';; HEADER SECTION' . "\n";
        }

        $this->header = new Net_DNS_Header($data);

        if ($this->debug) {
            $this->header->display();
        }

        /*
         *  Print and parse the QUESTION section of the packet
         */
        if ($this->debug) {
            echo "\n";
            $section = ($this->header->opcode  == 'UPDATE') ? 'ZONE' : 'QUESTION';
            echo ";; $section SECTION (" . $this->header->qdcount . ' record' .
                ($this->header->qdcount == 1 ? '' : 's') . ")\n";
        }

        $offset = 12;

        $this->question = array();
        for ($ctr = 0; $ctr < $this->header->qdcount; $ctr++) {
            list($qobj, $offset) = $this->parse_question($data, $offset);
            if (is_null($qobj)) {
                return(NULL);
            }

            $this->question[count($this->question)] = $qobj;
            if ($this->debug) {
                echo ";;\n;";
                $qobj->display();
            }
        }

        /*
         *  Print and parse the PREREQUISITE or ANSWER  section of the packet
         */
        if ($this->debug) {
            echo "\n";
            $section = ($this->header->opcode == 'UPDATE') ? 'PREREQUISITE' :'ANSWER';
            echo ";; $section SECTION (" .
                $this->header->ancount . ' record' .
                (($this->header->ancount == 1) ? '' : 's') .
                ")\n";
        }

        $this->answer = array();
        for ($ctr = 0; $ctr < $this->header->ancount; $ctr++) {
            list($rrobj, $offset) = $this->parse_rr($data, $offset);

            if (is_null($rrobj)) {
                return(NULL);
            }
            array_push($this->answer, $rrobj);
            if ($this->debug) {
                $rrobj->display();
            }
        }

        /*
         *  Print and parse the UPDATE or AUTHORITY section of the packet
         */
        if ($this->debug) {
            echo "\n";
            $section = ($this->header->opcode == 'UPDATE') ? 'UPDATE' : 'AUTHORITY';
            echo ";; $section SECTION (" .
                $this->header->nscount . ' record' .
                (($this->header->nscount == 1) ? '' : 's') .
                ")\n";
        }

        $this->authority = array();
        for ($ctr = 0; $ctr < $this->header->nscount; $ctr++) {
            list($rrobj, $offset) = $this->parse_rr($data, $offset);

            if (is_null($rrobj)) {
                return(NULL);
            }
            array_push($this->authority, $rrobj);
            if ($this->debug) {
                $rrobj->display();
            }
        }

        /*
         *  Print and parse the ADDITIONAL section of the packet
         */
        if ($this->debug) {
            echo "\n";
            echo ';; ADDITIONAL SECTION (' .
                $this->header->arcount . ' record' .
                (($this->header->arcount == 1) ? '' : 's') .
                ")\n";
        }

        $this->additional = array();
        for ($ctr = 0; $ctr < $this->header->arcount; $ctr++) {
            list($rrobj, $offset) = $this->parse_rr($data, $offset);

            if (is_null($rrobj)) {
                return(NULL);
            }
            array_push($this->additional, $rrobj);
            if ($this->debug) {
                $rrobj->display();
            }
        }

        return(TRUE);
    }

    /* }}} */
    /* Net_DNS_Packet::data() {{{*/
    /**
     * Build a packet from a Packet object hierarchy
     *
     * Builds a valid DNS packet suitable for sending to a DNS server or
     * resolver client containing all of the data in the packet hierarchy.
     *
     * @return string A binary string containing a DNS Packet