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.\" ========================================================================
.\"
.IX Title "Net::DNS::Nameserver 3"
.TH Net::DNS::Nameserver 3 "2022-12-30" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Net::DNS::Nameserver \- DNS server class
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Net::DNS::Nameserver;
\&
\&    my $nameserver = Net::DNS::Nameserver\->new(
\&        LocalAddr       => [\*(Aq::1\*(Aq , \*(Aq127.0.0.1\*(Aq],
\&        ZoneFile        => "filename"
\&        );
\&
\&    my $nameserver = Net::DNS::Nameserver\->new(
\&        LocalAddr       => \*(Aq10.1.2.3\*(Aq,
\&        LocalPort       => 5353,
\&        ReplyHandler    => \e&reply_handler
\&    );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Net::DNS::Nameserver offers a simple mechanism for instantiation of
customised \s-1DNS\s0 server objects intended to provide test responses to
queries emanating from a client resolver.
.PP
It is not, nor will it ever be, a general-purpose \s-1DNS\s0 nameserver
implementation.
.PP
See \*(L"\s-1EXAMPLE\*(R"\s0 for an example.
.SH "METHODS"
.IX Header "METHODS"
.SS "new"
.IX Subsection "new"
.Vb 4
\&    $nameserver = Net::DNS::Nameserver\->new(
\&        LocalAddr       => [\*(Aq::1\*(Aq , \*(Aq127.0.0.1\*(Aq],
\&        ZoneFile        => "filename"
\&        );
\&
\&    $nameserver = Net::DNS::Nameserver\->new(
\&        LocalAddr       => \*(Aq10.1.2.3\*(Aq,
\&        LocalPort       => 5353,
\&        ReplyHandler    => \e&reply_handler,
\&        Verbose         => 1,
\&        Truncate        => 0
\&    );
.Ve
.PP
Returns a Net::DNS::Nameserver object, or undef if the object
could not be created.
.PP
Each instance is configured using the following optional arguments:
.PP
.Vb 10
\&    LocalAddr           IP address on which to listen   Defaults to loopback address
\&    LocalPort           Port on which to listen         Defaults to 5353
\&    ZoneFile            Name of file containing RRs
\&                        accessed using the default
\&                        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)
\&    IdleTimeout         TCP clients are disconnected
\&                        if they are idle longer than
\&                        this duration                   Defaults to 120 (secs)
.Ve
.PP
The LocalAddr attribute may alternatively be specified as a list of \s-1IP\s0
addresses to listen to.
If the IO::Socket::IP library package is available on the system
this may also include IPv6 addresses.
.PP
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:
.PP
.Vb 6
\&    NOERROR     No error
\&    FORMERR     Format error
\&    SERVFAIL    Server failure
\&    NXDOMAIN    Non\-existent domain (name doesn\*(Aqt exist)
\&    NOTIMP      Not implemented
\&    REFUSED     Query refused
.Ve
.PP
For advanced usage it may also contain a headermask containing an
hashref with the settings for the \f(CW\*(C`aa\*(C'\fR, \f(CW\*(C`ra\*(C'\fR, and \f(CW\*(C`ad\*(C'\fR
header bits. The argument is of the form
\&\f(CW\*(C`{ ad => 1, aa => 0, ra => 1 }\*(C'\fR.
.PP
\&\s-1EDNS\s0 options may be specified in a similar manner using optionmask
\&\f(CW\*(C`{ $optioncode => $value, $optionname => $value }\*(C'\fR.
.PP
See \s-1RFC 1035\s0 and the \s-1IANA\s0 dns-parameters file for more information:
.PP
.Vb 2
\&  ftp://ftp.rfc\-editor.org/in\-notes/rfc1035.txt
\&  http://www.isi.edu/in\-notes/iana/assignments/dns\-parameters
.Ve
.PP
The nameserver will listen for both \s-1UDP\s0 and \s-1TCP\s0 connections.
On Unix-like systems, unprivileged users are denied access to ports below 1024.
.PP
\&\s-1UDP\s0 reply truncation functionality was introduced in \s-1VERSION 830.\s0
The size limit is determined by the \s-1EDNS0\s0 size advertised in the query,
otherwise 512 is used.
If you want to do packet truncation yourself you should set \f(CW\*(C`Truncate\*(C'\fR
to 0 and truncate the reply packet in the code of the ReplyHandler.
.PP
See \*(L"\s-1EXAMPLE\*(R"\s0 for an example.
.SS "main_loop"
.IX Subsection "main_loop"
.Vb 1
\&    $ns\->main_loop;
.Ve
.PP
Start accepting queries. Calling main_loop never returns.
.SS "loop_once"
.IX Subsection "loop_once"
.Vb 1
\&    $ns\->loop_once( [TIMEOUT_IN_SECONDS] );
.Ve
.PP
Start accepting queries, but returns. If called without a parameter, the
call will not return until a request has been received (and replied to).
Otherwise, the parameter specifies the maximum time to wait for a request.
A zero timeout forces an immediate return if there is nothing to do.
.PP
Handling a request and replying obviously depends on the speed of
ReplyHandler. Assuming a fast ReplyHandler, loop_once should spend just a
fraction of a second, if called with a timeout value of 0.0 seconds. One
exception is when an \s-1AXFR\s0 has requested a huge amount of data that the \s-1OS\s0
is not ready to receive in full. In that case, it will remain in a loop
(while servicing new requests) until the reply has been sent.
.PP
In case loop_once accepted a \s-1TCP\s0 connection it will immediately check if
there is data to be read from the socket. If not it will return and you
will have to call \fBloop_once()\fR again to check if there is any data waiting
on the socket to be processed. In most cases you will have to count on
calling \*(L"loop_once\*(R" twice.
.PP
A code fragment like:
.PP
.Vb 4
\&    $ns\->loop_once(10);
\&    while( $ns\->get_open_tcp() ){
\&        $ns\->loop_once(0);
\&    }
.Ve
.PP
Would wait for 10 seconds for the initial connection and would then
process all \s-1TCP\s0 sockets until none is left.
.SS "get_open_tcp"
.IX Subsection "get_open_tcp"
In scalar context returns the number of \s-1TCP\s0 connections for which state
is maintained. In array context it returns IO::Socket objects, these could
be useful for troubleshooting but be careful using them.
.SH "EXAMPLE"
.IX Header "EXAMPLE"
The following example will listen on port 5353 and respond to all queries
for A records with the \s-1IP\s0 address 10.1.2.3.	 All other queries will be
answered with \s-1NXDOMAIN.\s0	 Authority and additional sections are left empty.
The \f(CW$peerhost\fR variable catches the \s-1IP\s0 address of the peer host, so that
additional filtering on its basis may be applied.
.PP
.Vb 1
\&    #!/usr/bin/perl
\&
\&    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} . "\en";
\&        $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 \*(Aqaa\*(Aq flag)
\&        my $headermask = {aa => 1};
\&
\&        # specify EDNS options  { option => value }
\&        my $optionmask = {};
\&
\&        return ( $rcode, \e@ans, \e@auth, \e@add, $headermask, $optionmask );
\&    }
\&
\&
\&    my $ns = Net::DNS::Nameserver\->new(
\&        LocalPort    => 5353,
\&        ReplyHandler => \e&reply_handler,
\&        Verbose      => 1
\&        ) || die "couldn\*(Aqt create nameserver object\en";
\&
\&
\&    $ns\->main_loop;
.Ve
.SH "BUGS"
.IX Header "BUGS"
Limitations in perl make it impossible to guarantee that replies to
\&\s-1UDP\s0 queries from Net::DNS::Nameserver are sent from the IP-address
to which the query was directed.  This is a problem for machines with
multiple IP-addresses and causes violation of \s-1RFC2181\s0 section 4.
Thus a \s-1UDP\s0 socket created listening to \s-1INADDR_ANY\s0 (all available
IP-addresses) will reply not necessarily with the source address being
the one to which the request was sent, but rather with the address that
the operating system chooses. This is also often called \*(L"the closest
address\*(R". This should really only be a problem on a server which has
more than one IP-address (besides localhost \- any experience with IPv6
complications here, would be nice). If this is a problem for you, a
work-around would be to not listen to \s-1INADDR_ANY\s0 but to specify each
address that you want this module to listen on. A separate set of
sockets will then be created for each IP-address.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (c)2000 Michael Fuhr.
.PP
Portions Copyright (c)2002\-2004 Chris Reinhardt.
.PP
Portions Copyright (c)2005 Robert Martin-Legene.
.PP
Portions Copyright (c)2005\-2009 O.M, Kolkman, \s-1RIPE NCC.\s0
.PP
Portions Copyright (c)2017 Dick Franks.
.PP
All rights reserved.
.SH "LICENSE"
.IX Header "LICENSE"
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.
.PP
\&\s-1THE SOFTWARE IS PROVIDED \*(L"AS IS\*(R", 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.\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
perl, Net::DNS, Net::DNS::Resolver, Net::DNS::Packet,
Net::DNS::Update, Net::DNS::Header, Net::DNS::Question,
Net::DNS::RR, \s-1RFC 1035\s0