Net::DNS::Nameserver3pm

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
                        );

Instantiates a Net::DNS::Nameserver object. An exception is raised if the object could not be created.

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:

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.

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