Net::DNS(3)

📦
version 1.570.0 · 18 versions
, in opensuse-leap 16.0

💖 Net::DNS(3) 💖

okay bestie, welcome to Net::DNS(3), fresh out of the User Contributed Perl Documentation corner of the universe. this page is giving “Perl talks to DNS and absolutely slays” energy, no cap.

🎀 NAME 🎀

Net::DNS — Perl Interface to the Domain Name System 💅

✨ SYNOPSIS ✨

use Net::DNS;
my $resolver = Net::DNS::Resolver->new(...);
my $response = $resolver->send(...);

🌸 DESCRIPTION 🌸

Net::DNS is a whole collection of Perl modules that act as a Domain Name System (DNS) resolver. It lets you do DNS queries that are way beyond the capabilities of gethostbyname and gethostbyaddr. iconic, honestly.

You should be familiar with the structure of a DNS packet and the zone file presentation format described in RFC1035 — like, know the vibe of the packet, bestie.

🦋 Resolver Objects 🦋

A resolver object is an instance of the Net::DNS::Resolver class. A program can have multiple resolver objects, and each one keeps its own state information — stuff like the nameservers to be queried, whether recursion is desired, etc. main character energy.

🎀 Packet Objects 🎀

Net::DNS::Resolver queries return Net::DNS::Packet objects. A packet object has five sections:

  • header, represented by a Net::DNS::Header object
  • question, a list of no more than one Net::DNS::Question object
  • answer, a list of Net::DNS::RR objects
  • authority, a list of Net::DNS::RR objects
  • additional, a list of Net::DNS::RR objects

💫 Update Objects 💫

Net::DNS::Update is a subclass of Net::DNS::Packet that’s useful for creating dynamic update requests. cute.

⭐ Header Object ⭐

The Net::DNS::Header object mediates access to the header data that resides within the corresponding Net::DNS::Packet. it’s the access hookup, basically.

🌈 Question Object 🌈

The Net::DNS::Question object represents the content of the question section of the DNS packet. periodt.

💜 RR Objects 💜

Net::DNS::RR is the base class for DNS resource record (RR) objects in the answer, authority, and additional sections of a DNS packet.

do not assume that RR objects will be of the type you requested, bestie. the type of an RR object must be checked before calling any methods. that’s the safety check, no cap.

🛠️ METHODS 🛠️

Net::DNS exports methods and auxiliary functions to support DNS updates, zone serial number management, and simple DNS queries. versatile queen.

🏷️ version 🏷️

use Net::DNS;
print Net::DNS->version, "\n";

Returns the version of Net::DNS. slay.

🔍 rr 🔍

# Use a default resolver -- can not get an error string this way.
use Net::DNS;
my @rr = rr("example.com");
my @rr = rr("example.com", "AAAA");
my @rr = rr("example.com", "AAAA", "IN");

# Use your own resolver object.
my $res = Net::DNS::Resolver->new;
my @rr  = rr($res, "example.com" ... );

my ($ptr) = rr("2001:DB8::dead:beef");

The rr() method gives you simple RR lookup for those scenarios where you don’t need the full flexibility of Net::DNS.

It returns a list of Net::DNS::RR objects for the specified name, or an empty list if the query failed or no record was found.

See "EXAMPLES" for more complete examples.

📬 mx 📬

# Use a default resolver -- can not get an error string this way.
use Net::DNS;
my @mx = mx("example.com");

# Use your own resolver object.
my $res = Net::DNS::Resolver->new;
my @mx  = mx($res, "example.com");

Returns a list of Net::DNS::RR::MX objects representing the MX records for the specified name. The list will be sorted by preference. Returns an empty list if the query failed or no MX record was found.

This method does not look up address records; it resolves MX only. iykyk.

💥 Dynamic DNS Update Support 💥

The Net::DNS module provides auxiliary functions which support dynamic DNS update requests.

$update = Net::DNS::Update->new( 'example.com' );

$update->push( prereq => nxrrset('example.com. AAAA') );
$update->push( update => rr_add('example.com. 86400 AAAA 2001:DB8::F00') );

✅ yxrrset ✅

Use this method to add an "RRset exists" prerequisite to a dynamic update packet. There are two forms: value-independent and value-dependent:

# RRset exists (value-independent)
$update->push( pre => yxrrset("host.example.com AAAA") );

Meaning: At least one RR with the specified name and type must exist.

# RRset exists (value-dependent)
$update->push( pre => yxrrset("host.example.com AAAA 2001:DB8::1") );

Meaning: At least one RR with the specified name and type must exist and must have matching data.

Returns a Net::DNS::RR object or undef if the object could not be created.

❌ nxrrset ❌

Use this method to add an "RRset does not exist" prerequisite to a dynamic update packet.

$update->push( pre => nxrrset("host.example.com AAAA") );

Meaning: No RRs with the specified name and type can exist.

Returns a Net::DNS::RR object or undef if the object could not be created.

🧸 yxdomain 🧸

Use this method to add a "name is in use" prerequisite to a dynamic update packet.

$update->push( pre => yxdomain("host.example.com") );

Meaning: At least one RR with the specified name must exist.

Returns a Net::DNS::RR object or undef if the object could not be created.

🫥 nxdomain 🫥

Use this method to add a "name is not in use" prerequisite to a dynamic update packet.

$update->push( pre => nxdomain("host.example.com") );

Meaning: No RR with the specified name can exist.

Returns a Net::DNS::RR object or undef if the object could not be created.

➕ rr_add ➕

Use this method to add RRs to a zone.

$update->push( update => rr_add("host.example.com AAAA 2001:DB8::c001:a1e") );

Meaning: Add this RR to the zone.

RR objects created by this method should be added to the "update" section of a dynamic update packet. The TTL defaults to 86400 seconds (24 hours) if not specified.

Returns a Net::DNS::RR object or undef if the object could not be created.

➖ rr_del ➖

Use this method to delete RRs from a zone. There are three forms: delete all RRsets, delete an RRset, and delete a specific RR.

# Delete all RRsets.
$update->push( update => rr_del("host.example.com") );

Meaning: Delete all RRs having the specified name.

# Delete an RRset.
$update->push( update => rr_del("host.example.com AAAA") );

Meaning: Delete all RRs having the specified name and type.

# Delete a specific RR.
$update->push( update => rr_del("host.example.com AAAA 2001:DB8::dead:beef") );

Meaning: Delete the RR which matches the specified argument.

RR objects created by this method should be added to the "update" section of a dynamic update packet.

Returns a Net::DNS::RR object or undef if the object could not be created.

🌟 Zone Serial Number Management 🌟

The Net::DNS module provides auxiliary functions which support policy-driven zone serial numbering regimes. fancy.

$soa->serial(SEQUENTIAL);
$soa->serial(YYYMMDDxx);

🔢 SEQUENTIAL 🔢

$successor = $soa->serial( SEQUENTIAL );

The existing serial number is incremented modulo 2**32. math queen.

⏰ UNIXTIME ⏰

$successor = $soa->serial( UNIXTIME );

The Unix time scale will be used as the basis for zone serial numbering. The serial number will be incremented if the time elapsed since the previous update is less than one second.

📅 YYYYMMDDxx 📅

$successor = $soa->serial( YYYYMMDDxx );

The 32 bit value returned by the auxiliary YYYYMMDDxx() function will be used as the base for the date-coded zone serial number. Serial number increments must be limited to 100 per day for the date information to remain useful.

🧚 Sorting of RR arrays 🧚

rrsort() provides functionality to help you sort RR arrays. In most cases this will give you the result that you expect, but you can specify your own sorting method by using the "Net::DNS::RR::FOO->set_rrsort_func()" class method. See Net::DNS::RR for details.

🗂️ rrsort 🗂️

use Net::DNS;
my @sorted = rrsort( $rrtype, $attribute, @rr_array );

rrsort() selects all RRs from the input array that are of the type defined by the first argument. Those RRs are sorted based on the attribute that is specified as second argument.

There are a number of RRs for which the sorting function is defined in the code.

For instance:

my @prioritysorted = rrsort( "SRV", "priority", @rr_array );

returns the SRV records sorted from lowest to highest priority and for equal priorities from highest to lowest weight. obsessed.

If the function does not exist then a numerical sort on the attribute value is performed.

my @portsorted = rrsort( "SRV", "port", @rr_array );

If the attribute is not defined then either the default_sort() function or "canonical sorting" (as defined by DNSSEC) will be used.

rrsort() returns a sorted array containing only elements of the specified RR type. Any other RR types are silently discarded.

rrsort() returns an empty list when arguments are incorrect.

✨ EXAMPLES ✨

These quick examples show off a few Net::DNS features. For way more, check the docs for the individual modules plus the demo scripts that ship with the distribution. They're giving extended-example energy.

Want dynamic updates? Net::DNS::Update has an example, bestie.

🔎 Look up host addresses.

This one runs a search for AAAA and prints the address when the RR can do it:

use Net::DNS;
my $res   = Net::DNS::Resolver->new;
my $reply = $res->search( "www.example.com", "AAAA" );
die "query failed: ", $res->errorstring unless $reply;

foreach my $rr ( $reply->answer ) {
        print $rr->address, "\n" if $rr->can("address");
}

🧚 Find the nameservers for a domain.

Query for NS, then print each nsdname:

use Net::DNS;
my $res   = Net::DNS::Resolver->new;
my $reply = $res->query( "example.com", "NS");
die "query failed: ", $res->errorstring unless $reply;

foreach $rr ( grep {$_->type eq "NS"} $reply->answer ) {
        print $rr->nsdname, "\n";
}

💌 Find the MX records for a domain.

Grab the MX records with mx(), then print preference and exchange with a tab between them:

use Net::DNS;
my $name = "example.com";
my $res  = Net::DNS::Resolver->new;
my @mx   = mx( $res, $name );

foreach $rr (@mx) {
        print $rr->preference, "\t", $rr->exchange, "\n";
}

Query for SOA and let each answer RR print itself:

use Net::DNS;
my $res   = Net::DNS::Resolver->new;
my $reply = $res->query( "example.com", "SOA" );
die "query failed: ", $res->errorstring unless $reply;

foreach my $rr ( $reply->answer ) {
        $rr->print;
}

🦋 Perform a zone transfer and print all the records.

Set nameservers and tcp_timeout, call axfr, warn if there's an errorstring, then print every record:

use Net::DNS;
my $res  = Net::DNS::Resolver->new(
        nameservers => ["a.iana-servers.net", "b.iana-servers.net"],
        tcp_timeout => 20
        );

my @zone = $res->axfr("example.com");
warn $res->errorstring if $res->errorstring;

foreach $rr (@zone) {
        $rr->print;
}

🌸 Perform a background query and print the reply.

This sets udp_timeout(10) and tcp_timeout(20), sends with bgsend, polls bgbusy, reads with bgread, and prints the packet:

use Net::DNS;
my $res    = Net::DNS::Resolver->new;
$res->udp_timeout(10);
$res->tcp_timeout(20);
my $socket = $res->bgsend( "www.example.com", "AAAA" );

while ( $res->bgbusy($socket) ) {
        # do some work here whilst awaiting the response
        # ...and some more here
}

my $packet = $res->bgread($socket);
die "query failed: ", $res->errorstring unless $packet;

$packet->print;

🐛 BUGS 🐛

Okay, the BUGS section is short and brutally honest: Net::DNS is slow.

For other items to be fixed, or if you discover a bug in this distribution, please use the CPAN bug reporting system. That's the move, fr fr.

  • Copyright (c)1997-2000 Michael Fuhr.
  • Portions Copyright (c)2002,2003 Chris Reinhardt.
  • Portions Copyright (c)2005 Olaf Kolkman (RIPE NCC)
  • Portions Copyright (c)2006 Olaf Kolkman (NLnet Labs)
  • Portions Copyright (c)2014 Dick Franks

All rights reserved.

📜 LICENSE 📜

Legal time, bestie — here's the full license text:

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the original copyright notices appear in all copies and that both copyright notice and this permission notice appear in supporting documentation, and that the name of the author not be used in advertising or publicity pertaining to distribution of the software without specific prior written permission.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

👑 AUTHOR INFORMATION 👑

  • Net::DNS is maintained at NLnet Labs (www.nlnetlabs.nl) by Willem Toorop and Dick Franks.
  • Between 2005 and 2012 Net::DNS was maintained by Olaf Kolkman.
  • Between 2002 and 2004 Net::DNS was maintained by Chris Reinhardt.
  • Net::DNS was created in 1997 by Michael Fuhr.

🌈 SEE ALSO 🌈

Go read these, iykyk:

perl Net::DNS::Resolver Net::DNS::Question Net::DNS::RR Net::DNS::Packet
Net::DNS::Update RFC1035 <https://iana.org/go/rfc1035>

That's the whole Net::DNS(3) page, bestie — source/version perl v5.42.0, date 2026-09-02. Mwah 💋

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