Net::DN...eserver(3)

📦

version 1.57 · 18 versions

✨ NAME ✨

Net::DNS::Nameserver — DNS server class. This is the Net::DN...eserver(3) page from the User Contributed Perl Documentation collection, and it's here to give your tests a cute little DNS server. 💖

🦋 SYNOPSIS 🦋

use Net::DNS::Nameserver;

my $nameserver = Net::DNS::Nameserver->new(
                LocalAddr       => ['::1', '127.0.0.1'],
                LocalPort       => 15353,
                ZoneFile        => 'filename'
                );

my $nameserver = Net::DNS::Nameserver->new(
                LocalAddr       => '10.1.2.3',
                LocalPort       => 15353,
                ReplyHandler    => \&reply_handler
                );

$nameserver->start_server($timeout);
$nameserver->stop_server;

💖 DESCRIPTION 💖

okay so Net::DNS::Nameserver offers a simple mechanism for instantiation of customised DNS server objects, and those objects are intended to provide test responses to queries emanating from a client resolver. It's giving "tiny fake DNS server for testing" and honestly? Iconic.

⚠️ Important vibe check: It is not, nor will it ever be, a general-purpose DNS nameserver implementation. Periodt.

See the EXAMPLES section below for further details.

🌸 METHODS 🌸

🎀 new 🎀

$nameserver = Net::DNS::Nameserver->new(
                LocalAddr       => ['::1', '127.0.0.1'],
                LocalPort       => 15353,
                ZoneFile        => "filename"
                );

$nameserver = Net::DNS::Nameserver->new(
                LocalAddr       => '10.1.2.3',
                LocalPort       => 15353,
                ReplyHandler    => \&reply_handler,
                Verbose         => 1,
                Truncate        => 0
                );

This instantiates a Net::DNS::Nameserver object. An exception is raised if the object could not be created — no silent fail, bestie.

Each instance is configured using the following optional arguments:

LocalAddr — IP address on which to listen. Defaults to the local loopback address.
LocalPort — Port on which to listen.
ZoneFile — Name of file containing RRs accessed using the internal reply-handling subroutine.
ReplyHandler — Reference to customised reply-handling subroutine.
NotifyHandler — Reference to reply-handling subroutine for queries with opcode NOTIFY (RFC1996).
UpdateHandler — Reference to reply-handling subroutine for queries with opcode UPDATE (RFC2136).
Verbose — Report internal activity. Defaults to 0 (off).
Truncate — Truncates UDP packets that are too big for the reply. Defaults to 1 (on).

The LocalAddr attribute may alternatively be specified as an array of IP addresses to listen to.

The ReplyHandler subroutine is passed the query name, query class, query type, peerhost, query record, and connection descriptor. It must either return the response code and references to the answer, authority, and additional sections of the response, or undef to leave the query unanswered. Common response codes are:

NOERROR — No error
FORMERR — Format error
SERVFAIL — Server failure
NXDOMAIN — Non-existent domain (name doesn't exist)
NOTIMP — Not implemented
REFUSED — Query refused

For advanced usage it may also contain a headermask containing an hashref with the settings for the "aa", "ra", and "ad" header bits. The argument is of the form:

{ad => 1, aa => 0, ra => 1}

EDNS options may be specified in a similar manner using the optionmask:

{$optioncode => $value, $optionname => $value}

See RFC1035 and IANA DNS parameters file for more information:

The nameserver will listen for both UDP and TCP connections. On linux and other Unix-like systems, unprivileged users are denied access to ports below 1024.

UDP reply truncation functionality was introduced in Net::DNS 0.66. The size limit is determined by the EDNS0 size advertised in the query, otherwise 512 is used. If you want to do packet truncation yourself you should set Truncate=>0 and truncate the reply packet in the code of the ReplyHandler.

🚀 start_server 🚀

$ns->start_server( <TIMEOUT_IN_SECONDS> );

Starts a server process for each of the specified UDP and TCP sockets which continuously responds to user connections.

The timeout parameter specifies the time the server is to remain active. If called with no parameter a default timeout of 10 minutes is applied.

🛑 stop_server 🛑

$ns->stop_server();

Terminates all server processes in an orderly fashion.

🧪 EXAMPLES 🧪

🧸 Example 1: Test script with embedded nameserver 🧸

The following example is a self-contained test script which queries DNS zonefile data served by an embedded Net::DNS::Nameserver instance.

use strict;
use warnings;
use Test::More;

plan skip_all => 'Net::DNS::Nameserver not available'
                unless eval { require Net::DNS::Nameserver }
                and Net::DNS::Nameserver->can('start_server');
plan tests => 2;

my $resolver = Net::DNS::Resolver->new(
                nameserver => ['::1', '127.0.0.1'],
                port       => 15353
                );

my $ns = Net::DNS::Nameserver->new(
                LocalAddr => [$resolver->nameserver],
                LocalPort => $resolver->port,
                Verbose   => 0,
                ZoneFile  => \*DATA
                ) or die "couldn't create nameserver object";

$ns->start_server(10);

my $reply = $resolver->send(qw(example.com SOA));
is( ref($reply), 'Net::DNS::Packet', 'received reply packet' );
my ($rr) = $reply->answer;
is( $rr->type, 'SOA', 'answer contains SOA record' );

$ns->stop_server();

exit;

__DATA__
$ORIGIN example.com.
@       IN SOA  mname rname 2023 2h 1h 2w 1h
www     IN A    93.184.216.34

🦄 Example 2: Free-standing customised DNS nameserver 🦄

The following example will listen on port 15353 and respond to all queries for A records with the IP address 10.1.2.3. All other queries will be answered with NXDOMAIN. Authority and additional sections are left empty. The $peerhost variable catches the IP address of the peer host, so that additional filtering on a per-host basis may be applied.

use strict;
use warnings;
use Net::DNS::Nameserver;

sub reply_handler {
        my ( $qname, $qclass, $qtype, $peerhost, $query, $conn ) = @_;
        my ( $rcode, @ans, @auth, @add );

        print "Received query from $peerhost to " . $conn->{sockhost} . "\n";
        $query->print;

        if ( $qtype eq "A" && $qname eq "foo.example.com" ) {
                my ( $ttl, $rdata ) = ( 3600, "10.1.2.3" );
                my $rr = Net::DNS::RR->new("$qname $ttl $qclass $qtype $rdata");
                push @ans, $rr;
                $rcode = "NOERROR";
        } elsif ( $qname eq "foo.example.com" ) {
                $rcode = "NOERROR";

        } else {
                $rcode = "NXDOMAIN";
        }

        # mark the answer as authoritative (by setting the 'aa' flag)
        my $headermask = {aa => 1};

        # specify EDNS options  { option => value }
        my $optionmask = {};

        return ( $rcode, \@ans, \@auth, \@add, $headermask, $optionmask );
}

my $ns = Net::DNS::Nameserver->new(
                LocalPort    => 15353,
                ReplyHandler => \&reply_handler,
                Verbose      => 1
                ) or die "couldn't create nameserver object";

$ns->start_server(60);

exit;   # leaving nameserver processes running for 60 seconds

💀 BUGS 💀

Limitations in perl make it impossible to guarantee that replies to UDP queries from Net::DNS::Nameserver are sent from the IP-address to which the query was directed, the source address being chosen by the operating system based upon its notion of "closest address". This limitation is mitigated to some extent by creating a separate socket and subprocess for each IP address.

📜 COPYRIGHT 📜

⚖️ LICENSE ⚖️

okay legal besties, this part is staying exact because we do not mess with 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.

👀 SEE ALSO 👀

perl
Net::DNS
Net::DNS::Resolver
Net::DNS::Packet
Net::DNS::Update
Net::DNS::Header
Net::DNS::Question
Net::DNS::RR

okay bestie, that's a wrap — source/version perl v5.42.2, dated 2026-09-01. Go forth and serve DNS like the main character you are. 💅✨🦋

📦 where this page comes from

arch rolling: perl-net-dns 1.57-1 · MIT
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-06: a language model's rewrite of the original, under its terms