Net::DNS::Packet(3)

NAME
Net::DNS::Packet - DNS protocol packet

SYNOPSIS
    use Net::DNS::Packet;

    $query = new Net::DNS::Packet('example.com', 'MX', 'IN');

    $reply = $resolver->send($query);

DESCRIPTION
A "Net::DNS::Packet" object represents a DNS protocol packet.

METHODS

  new
    $packet = new Net::DNS::Packet('example.com');
    $packet = new Net::DNS::Packet('example.com', 'MX', 'IN');

    $packet = new Net::DNS::Packet();

If passed a domain, type, and class, "new" creates a packet object appropriate for making a DNS query for the requested information. The type and class can be omitted; they default to A and IN.

If called with an empty argument list, "new" creates an empty packet.

    $packet = new Net::DNS::Packet(\$data);
    $packet = new Net::DNS::Packet(\$data, 1);          # set debugging

If passed a reference to a scalar containing DNS packet data, a new packet object is created by decoding the data. The optional second boolean argument is used to enable debugging output.

Returns undef if unable to create a packet object.

Decoding errors, including data corruption and truncation, are collected in the $@ ($EVAL_ERROR) variable.

    ($packet, $length) = new Net::DNS::Packet(\$data);

If called in array context, returns a packet object and the number of octets successfully decoded.

Note that the number of RRs in each section of the packet may differ from the corresponding header value if the data has been truncated or corrupted.

  data
    $data = $packet->data;
    $data = $packet->data($limit);

Returns the packet data in binary format, suitable for sending to a nameserver.

  header
    $header = $packet->header;

Constructor method which returns a reference to the unique "Net::DNS::Header" object which represents the header section of the packet.

  EDNS extended header
    $edns    = $packet->edns;
    $version = $edns->version;
    $size    = $edns->size;

Auxilliary function edns() provides access to EDNS extensions.

  reply
    $reply = $query->reply( $UDPmax );

Constructor method which returns a new reply packet.

The optional UDPsize argument is the maximum UDP packet size which can be reassembled by the local network stack, and is advertised in response to an EDNS query.

  question, zone
    @question = $packet->question;

Returns a list of "Net::DNS::Question" objects representing the question section of the packet.

In dynamic update packets, this section is known as "zone" and specifies the zone to be updated.

  answer, pre, prerequisite
    @answer = $packet->answer;

Returns a list of "Net::DNS::RR" objects representing the answer section of the packet.

In dynamic update packets, this section is known as "pre" or "prerequisite" and specifies the RRs or RRsets which must or must not preexist.

  authority, update
    @authority = $packet->authority;

Returns a list of "Net::DNS::RR" objects representing the authority section of the packet.

In dynamic update packets, this section is known as "update" and specifies the RRs or RRsets to be added or deleted.

  additional
    @additional = $packet->additional;

Returns a list of "Net::DNS::RR" objects representing the additional section of the packet.

  print
    $packet->print;

Prints the packet data on the standard output in an ASCII format similar to that used in DNS zone files.

  string
    print $packet->string;

Returns a string representation of the packet.

  answerfrom
    print "packet received from ", $packet->answerfrom, "\n";

Returns the IP address from which we received this packet. User-created packets will return undef for this method.

  answersize
    print "packet size: ", $packet->answersize, " bytes\n";

Returns the size of the packet in bytes as it was received from a nameserver. User-created packets will return undef for this method (use "length $packet->data" instead).

  push
    $ancount = $packet->push(prereq => $rr);
    $nscount = $packet->push(update => $rr);
    $arcount = $packet->push(additional => $rr);

    $nscount = $packet->push(update => $rr1, $rr2, $rr3);
    $nscount = $packet->push(update => @rr);

Adds RRs to the specified section of the packet.

Returns the number of resource records in the specified section.

  unique_push
    $ancount = $packet->unique_push(prereq => $rr);
    $nscount = $packet->unique_push(update => $rr);
    $arcount = $packet->unique_push(additional => $rr);

    $nscount = $packet->unique_push(update => $rr1, $rr2, $rr3);
    $nscount = $packet->unique_push(update => @rr);

Adds RRs to the specified section of the packet provided that the RRs do not already exist in the packet.

Returns the number of resource records in the specified section.

  pop
    my $rr = $packet->pop("pre");
    my $rr = $packet->pop("update");
    my $rr = $packet->pop("additional");
    my $rr = $packet->pop("question");

Removes RRs from the specified section of the packet.

  dn_comp
    $compname = $packet->dn_comp("foo.example.com", $offset);

Returns a domain name compressed for a particular packet object, to be stored beginning at the given offset within the packet data. The name will be added to a running list of compressed domain names for future use.

  dn_expand
    use Net::DNS::Packet qw(dn_expand);
    ($name, $nextoffset) = dn_expand(\$data, $offset);

    ($name, $nextoffset) = Net::DNS::Packet::dn_expand(\$data, $offset);

Expands the domain name stored at a particular location in a DNS packet. The first argument is a reference to a scalar containing the packet data. The second argument is the offset within the packet where the (possibly compressed) domain name is stored.

Returns the domain name and the offset of the next location in the packet.

Returns undef if the domain name could not be expanded.

  sign_tsig
    $key_name = "tsig-key";
    $key      = "awwLOtRfpGE+rRKF2+DEiw==";

    $update = Net::DNS::Update->new("example.com");
    $update->push("update", rr_add("foo.example.com A 10.1.2.3"));

    $update->sign_tsig($key_name, $key);

    $response = $res->send($update);

Attaches a TSIG resource record object containing a key, which will be used to sign a packet with a TSIG resource record (see RFC 2845). Uses the following defaults:

    algorithm   = HMAC-MD5.SIG-ALG.REG.INT
    time_signed = current time
    fudge       = 300 seconds

If you wish to customize the TSIG record, you'll have to create it yourself and call the appropriate Net::DNS::RR::TSIG methods. The following example creates a TSIG record and sets the fudge to 60 seconds:

    $key_name = "tsig-key";
    $key      = "awwLOtRfpGE+rRKF2+DEiw==";

    $tsig = Net::DNS::RR->new("$key_name TSIG $key");
    $tsig->fudge(60);

    $query = Net::DNS::Packet->new("www.example.com");
    $query->sign_tsig($tsig);

    $response = $res->send($query);

  sign_sig0
SIG0 support is provided through the Net::DNS::RR::SIG class. This class is not part of the default Net::DNS distribution but resides in the Net::DNS::SEC distribution.

    $update = Net::DNS::Update->new("example.com");
    $update->push("update", rr_add("foo.example.com A 10.1.2.3"));
    $update->sign_sig0("Kexample.com+003+25317.private");

SIG0 support is experimental see Net::DNS::RR::SIG for details.

The method will call "Carp::croak()" if Net::DNS::RR::SIG cannot be found.

  truncate
The truncate method takes a maximum length as argument and then tries to truncate the packet an set the TC bit according to the rules of RFC2181 Section 9.

The minimum maximum length that is honored is 512 octets.

COPYRIGHT
Copyright (c)1997-2002 Michael Fuhr.

Portions Copyright (c)2002-2004 Chris Reinhardt.

Portions Copyright (c)2002-2009 Olaf Kolkman

Portions Copyright (c)2007-2008 Dick Franks

All rights reserved.

This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO
perl, Net::DNS, Net::DNS::Resolver, Net::DNS::Update, Net::DNS::Header, Net::DNS::Question, Net::DNS::RR, RFC 1035 Section 4.1, RFC 2136 Section 2, RFC 2845