Net::DNS::Packet • man page

Net::DNS::Packet (3)

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========================================================================

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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 Net::DNS::Packet object which is suitable for making a

DNS

query for the specified information. The type and class may 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 );        # debug

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 enables 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 during transmission.

data

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

Returns the packet data in binary format, suitable for sending as a query or update request to a nameserver.

Truncation may be specified using a non-zero optional size argument.

header

    $header = $packet->header;

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

EDNS
extended header

    $edns    = $packet->edns;
    $version = $edns->version;
    $size    = $edns->size;

Auxiliary 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

DNS

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

address from which this packet was received. 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 are not already present in the same section.

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' );

Removes a single

from the specified section of the packet.

sign_tsig

    $query = Net::DNS::Packet->new( 'www.example.com', 'A' );

    $query->sign_tsig(
                'Khmac-sha512.example.+165+01018.private',
                fudge => 60
                );

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

    $reply->verify( $query ) || die $reply->verifyerr;

Attaches a

TSIG

resource record object, which will be used to sign the packet (see

RFC 2845

The

TSIG

record can be customised by optional additional arguments to sign_tsig() or by calling the appropriate Net::DNS::RR::TSIG methods.

If you wish to create a

TSIG

record using a non-standard algorithm, you will have to create it yourself. In all cases, the

TSIG

name must uniquely identify the key shared between the parties, and the algorithm name must identify the signing function to be used with the specified key.

    $tsig = Net::DNS::RR->new(
                name            => 'tsig.example',
                type            => 'TSIG',
                algorithm       => 'custom-algorithm',
                key             => '<base64 key text>',
                sig_function    => sub {
                                          my ($key, $data) = @_;
                                                ...
                                        }
                );

    $query->sign_tsig( $tsig );

The historical simplified syntax is still available, but additional options can not be specified.

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

The response to an inbound request is signed by presenting the request in place of the key parameter.

    $response = $request->reply;
    $response->sign_tsig( $request, @options );

Multi-packet transactions are signed by chaining the sign_tsig() calls together as follows:

    $opaque  =  $packet1->sign_tsig( 'Kexample.+165+13281.private' );
    $opaque  =  $packet2->sign_tsig( $opaque );
                $packet3->sign_tsig( $opaque );

The opaque intermediate object references returned during multi-packet signing are not intended to be accessed by the end-user application. Any such access is expressly forbidden.

Note that a

TSIG

record is added to every packet; this implementation does not support the suppressed signature scheme described in

RFC2845.

verify and verifyerr

    $packet->verify()           || die $packet->verifyerr;
    $reply->verify( $query )    || die $reply->verifyerr;

Verify

TSIG

signature of packet or reply to the corresponding query.

    $opaque  =  $packet1->verify( $query ) || die $packet1->verifyerr;
    $opaque  =  $packet2->verify( $opaque );
    $verifed =  $packet3->verify( $opaque ) || die $packet3->verifyerr;

The opaque intermediate object references returned during multi-packet verify() will be undefined (Boolean false) if verification fails. Access to the object itself, if it exists, is expressly forbidden. Testing at every stage may be omitted, which results in a

BADSIG

error on the final packet in the absence of more specific information.

sign_sig0

SIG0

support is provided through the Net::DNS::RR::SIG class. This class is not integrated into Net::DNS but resides in the Net::DNS::SEC distribution available from

CPAN.

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

Execution will be terminated if Net::DNS::RR::SIG is not available.

verify
SIG0

    $packet->verify( $keyrr )           || die $packet->verifyerr;
    $packet->verify( [$keyrr, ...] )    || die $packet->verifyerr;

Verify

SIG0

packet signature against one or more specified

KEY

RRs.

truncate

The truncate method takes a maximum length as argument and then tries to truncate the packet and set the

bit according to the rules of

RFC2181

Section 9.

The minimum maximum length that is honoured is 512 octets.

COPYRIGHT

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

Net::DNS::Packet • man page

Net::DNS::Packet • man page

Net::DNS::Packet (3)

Leading comments

NAME

SYNOPSIS

DESCRIPTION

METHODS

new

data

header

EDNS
extended header

reply

question, zone

answer, pre, prerequisite

authority, update

additional

print

string

answerfrom

answersize

push

unique_push

pop

sign_tsig

verify and verifyerr

sign_sig0

verify
SIG0

truncate

COPYRIGHT

SEE ALSO

Man Section

extra • Version

extra • Source

extra • Book

Net::DNS::Packet • man page

Net::DNS::Packet • man page

Net::DNS::Packet (3)

Leading comments

NAME

SYNOPSIS

DESCRIPTION

METHODS

new

data

header

EDNS extended header

reply

question, zone

answer, pre, prerequisite

authority, update

additional

print

string

answerfrom

answersize

push

unique_push

pop

sign_tsig

verify and verifyerr

sign_sig0

verify SIG0

truncate

COPYRIGHT

SEE ALSO

Man Section

extra • Version

extra • Source

extra • Book

EDNS
extended header

verify
SIG0