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Manual Reference Pages  -  NET::DNS::TOOLKIT::RR::SOA (3)

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Net::DNS::ToolKit::RR::SOA - Resource Record Handler



  DO NOT use Net::DNS::ToolKit::RR::SOA
  DO NOT require Net::DNS::ToolKit::RR::SOA

  Net::DNS::ToolKit::RR::SOA is autoloaded by
  class Net::DNS::ToolKit::RR and its methods
  are instantiated in a special manner.

  use Net::DNS::ToolKit::RR;
  ($get,$put,$parse) = new Net::DNS::ToolKit::RR;

        ) = $get->SOA(\$buffer,$offset);

  Note: the $get->SOA method is normally called
  via:  @stuff = $get->next(\$buffer,$offset);


    = $parse->SOA($name,$type,$class,$ttl,$rdlength,


<B>Net::DNS::ToolKit::RR:SOAB> appends an SOA resource record to a DNS packet under construction, recovers an SOA resource record from a packet being decoded, and converts the numeric/binary portions of the resource record to human readable form.

  Description from RFC1035.txt

  3.2.1. Format

  All RRs have the same top level format shown below:

                                    1  1  1  1  1  1
      0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
    |                      NAME                     |
    |                      TYPE                     |
    |                     CLASS                     |
    |                      TTL                      |
    |                   RDLENGTH                    |
    |                     RDATA                     |

  NAME  an owner name, i.e., the name of the node to which this
        resource record pertains.

  TYPE  two octets containing one of the RR TYPE codes.

  CLASS two octets containing one of the RR CLASS codes.

  TTL   a 32 bit signed integer that specifies the time interval
        that the resource record may be cached before the source
        of the information should again be consulted.  Zero
        values are interpreted to mean that the RR can only be
        used for the transaction in progress, and should not be
        cached.  For example, SOA records are always distributed
        with a zero TTL to prohibit caching.  Zero values can
        also be used for extremely volatile data.

  RDLENGTH an unsigned 16 bit integer that specifies the length
        in octets of the RDATA field.

  RDATA a variable length string of octets that describes the
        resource.  The format of this information varies
        according to the TYPE and CLASS of the resource record.

    3.3.13. SOA RDATA format

    /                     MNAME                     /
    /                                               /
    /                     RNAME                     /
    |                    SERIAL                     |
    |                                               |
    |                    REFRESH                    |
    |                                               |
    |                     RETRY                     |
    |                                               |
    |                    EXPIRE                     |
    |                                               |
    |                    MINIMUM                    |
    |                                               |


    MNAME The <domain-name> of the name server that was
        the original or primary source of data for this

    RNAME A <domain-name> which specifies the mailbox of
        the person responsible for this zone.

    SERIAL The unsigned 32 bit version number of the
        original copy of the zone.  Zone transfers
        preserve this value.  This value wraps and
        should be compared using sequence space

    REFRESH A 32 bit time interval before the zone
        should be refreshed.

    RETRY A 32 bit time interval that should elapse
        before a failed refresh should be retried.

    EXPIRE A 32 bit time value that specifies the upper
        limit on the time interval that can elapse
        before the zone is no longer authoritative.

    MINIMUM The unsigned 32 bit minimum TTL field that
        should be exported with any RR from this zone.

SOA records cause no additional section processing.

All times are in units of seconds.

Most of these fields are pertinent only for name server maintenance operations. However, MINIMUM is used in all query operations that retrieve RRs from a zone. Whenever a RR is sent in a response to a query, the TTL field is set to the maximum of the TTL field from the RR and the MINIMUM field in the appropriate SOA. Thus MINIMUM is a lower bound on the TTL field for all RRs in a zone. Note that this use of MINIMUM should occur when the RRs are copied into the response and not when the zone is loaded from a master file or via a zone transfer. The reason for this provison is to allow future dynamic update facilities to change the SOA RR with known semantics.
o @stuff = $get->SOA(\$buffer,$offset);

  Get the contents of the resource record.

  USE: @stuff = $get->next(\$buffer,$offset);

  where: @stuff = (
  $newoff $name,$type,$class,$ttl,$rdlength,

All except the last five (5) items, <B>B>$mname<B>,$rname,$serial,$refresh,$retry,$expire,$minB>, are provided by the class loader, <B>Net::DNS::ToolKit::RRB>. The code in this method knows how to retrieve <B>B>$mname<B>,$rname,$serial,$refresh,$retry,$expire,$minB>.

  input:        pointer to buffer,
                offset into buffer
  returns:      offset to next resource,
                @common RR elements,
                primary server name,
                zone contact,
                RR serial number,
                REFRESH timer,
                RETRY timer,
                EXPIRE timer,
                MINIMUM ttl

o ($newoff,@dnptrs)=$put->SOA(\$buffer,$offset,\@dnptrs,

Append an SOA record to $buffer.

  where @common = (

The method will insert the $rdlength, $mname, $rname, $serial, $refresh, $retry, $expire, and $min, then return the updated pointer to the array of compressed names

The class loader, <B>Net::DNS::ToolKit::RRB>, inserts the @common elements and returns updated @dnptrs. This module knows how to insert its RDATA and calculate the $rdlength.

  input:        pointer to buffer,
                offset (normally end of buffer),
                pointer to compressed name array,
                @common RR elements,
                primary server name,
                zone contact,
                RR serial number,
                REFRESH timer,
                RETRY timer,
                EXPIRE timer,
                MINIMUM ttl
  output:       offset to next RR,
                new compressed name pointer array,
           or   empty list () on error.

o (@COMMON,$MNAME,$RNAME,$serial,$refresh,$retry,$expire,$min)
        = $parse->A(@common,

Converts binary/numeric field data into human readable form. The common RR elements are supplied by the class loader, <B>Net::DNS::ToolKit::RRB>. For SOA RR’s, this returns $mxdname terminated with ’.’

  input:        primary server name,
                zone contact,
                serial number,
                refresh timer,
                retry timer,
                expire timer,
                minimum ttl
  returns:      SERVER NAME . terminated
                CONTACT NAME . terminated
                serial number,
                refresh timer,
                retry timer,
                expire timer,
                minimum ttl






Michael Robinton <>


    Copyright 2003 - 2011, Michael Robinton <>

Michael Robinton <>

All rights reserved.

This program is free software; you can redistribute it and/or modify it under the terms of either:

  a) the GNU General Public License as published by the Free
  Software Foundation; either version 2, or (at your option) any
  later version, or

  b) the "Artistic License" which comes with this distribution.

This program 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 either the GNU General Public License or the Artistic License for more details.

You should have received a copy of the Artistic License with this distribution, in the file named Artistic. If not, I’ll be glad to provide one.

You should also have received a copy of the GNU General Public License along with this program in the file named Copying. If not, write to the

        Free Software Foundation, Inc.                       
        59 Temple Place, Suite 330
        Boston, MA  02111-1307, USA

or visit their web page on the internet at:

See also:

Net::DNS::Codes(3), Net::DNS::ToolKit(3)
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perl v5.20.3 NET::DNS::TOOLKIT::RR::SOA (3) 2011-11-05

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