package Net::DNS::Nameserver;
use Net::DNS;
use IO::Socket;
use IO::Select;
use Carp qw(cluck);
use strict;
use vars qw($VERSION);
$VERSION = (qw$Revision: 1.1 $)[1];
use constant DEFAULT_ADDR => INADDR_ANY;
use constant DEFAULT_PORT => 53;
sub new {
my ($class, %self) = @_;
my $addr = $self{"LocalAddr"} || inet_ntoa(DEFAULT_ADDR);
my $port = $self{"LocalPort"} || DEFAULT_PORT;
if (!$self{"ReplyHandler"} || !ref($self{"ReplyHandler"})) {
cluck "No reply handler!";
return;
}
print "creating TCP socket..." if $self{"Verbose"};
my $sock_tcp = IO::Socket::INET->new(
LocalAddr => $addr,
LocalPort => $port,
Listen => 5,
Proto => "tcp",
Reuse => 1,
);
if (!$sock_tcp) {
cluck "couldn't create TCP socket: $!";
return;
}
print "done.\n" if $self{"Verbose"};
print "creating UDP socket..." if $self{"Verbose"};
my $sock_udp = IO::Socket::INET->new(
LocalAddr => $addr,
LocalPort => $port,
Proto => "udp",
);
if (!$sock_udp) {
cluck "couldn't create UDP socket: $!";
return;
}
print "done.\n" if $self{"Verbose"};
$self{"select"} = IO::Select->new;
$self{"select"}->add($sock_tcp);
$self{"select"}->add($sock_udp);
my $self = bless \%self, $class;
return $self;
}
sub make_reply {
my ($self, $query, $peerhost) = @_;
my $reply;
my $headermask;
if (not $query) {
print "ERROR: invalid packet\n" if $self->{"Verbose"};
$reply = Net::DNS::Packet->new("", "ANY", "ANY");
$reply->header->rcode("FORMERR");
return $reply;
}
if ($query->header->qr()) {
print "ERROR: invalid packet (qr was set, dropping)\n" if $self->{"Verbose"};
return;
}
my $qr = ($query->question)[0];
my $qname = $qr ? $qr->qname : "";
my $qclass = $qr ? $qr->qclass : "ANY";
my $qtype = $qr ? $qr->qtype : "ANY";
$reply = Net::DNS::Packet->new($qname, $qtype, $qclass);
if ($query->header->opcode eq "QUERY") {
if ($query->header->qdcount == 1) {
print "query ", $query->header->id,
": ($qname, $qclass, $qtype)..." if $self->{"Verbose"};
my ($rcode, $ans, $auth, $add);
($rcode, $ans, $auth, $add, $headermask) =
&{$self->{"ReplyHandler"}}($qname, $qclass, $qtype, $peerhost, $query);
print "$rcode\n" if $self->{"Verbose"};
$reply->header->rcode($rcode);
$reply->push("answer", @$ans) if $ans;
$reply->push("authority", @$auth) if $auth;
$reply->push("additional", @$add) if $add;
} else {
print "ERROR: qdcount ", $query->header->qdcount,
"unsupported\n" if $self->{"Verbose"};
$reply->header->rcode("FORMERR");
}
} else {
print "ERROR: opcode ", $query->header->opcode, " unsupported\n"
if $self->{"Verbose"};
$reply->header->rcode("FORMERR");
}
if (!defined ($headermask)) {
$reply->header->ra(1);
$reply->header->ad(0);
} else {
$reply->header->aa(1) if $headermask->{'aa'};
$reply->header->ra(1) if $headermask->{'ra'};
$reply->header->ad(1) if $headermask->{'ad'};
}
$reply->header->qr(1);
$reply->header->cd($query->header->cd);
$reply->header->rd($query->header->rd);
$reply->header->id($query->header->id);
$reply->header->print if $self->{"Verbose"} && defined $headermask;
return $reply;
}
sub tcp_connection {
my ($self, $sock) = @_;
my $peerhost = $sock->peerhost;
print "TCP connection from ", $sock->peerhost, ":", $sock->peerport, "\n"
if $self->{"Verbose"};
while (1) {
my $buf;
print "reading message length..." if $self->{"Verbose"};
$sock->read($buf, 2) or last;
print "done\n" if $self->{"Verbose"};
my ($msglen) = unpack("n", $buf);
print "expecting $msglen bytes..." if $self->{"Verbose"};
$sock->read($buf, $msglen);
print "got ", length($buf), " bytes\n" if $self->{"Verbose"};
my $query = Net::DNS::Packet->new(\$buf);
my $reply = $self->make_reply($query, $peerhost) || last;
my $reply_data = $reply->data;
print "writing response..." if $self->{"Verbose"};
$sock->write(pack("n", length($reply_data)) . $reply_data);
print "done\n" if $self->{"Verbose"};
}
print "closing connection..." if $self->{"Verbose"};
$sock->close;
print "done\n" if $self->{"Verbose"};
}
sub udp_connection {
my ($self, $sock) = @_;
my $buf = "";
my $peer_sockaddr = $sock->recv($buf, &Net::DNS::PACKETSZ);
my ($peerport, $peeraddr) = sockaddr_in($peer_sockaddr);
my $peerhost = inet_ntoa($peeraddr);
print "UDP connection from $peerhost:$peerport\n" if $self->{"Verbose"};
my $query = Net::DNS::Packet->new(\$buf);
my $reply = $self->make_reply($query, $peerhost) || return;
my $reply_data = $reply->data;
print "writing response..." if $self->{"Verbose"};
$sock->send($reply_data) or die "send: $!";
print "done\n" if $self->{"Verbose"};
}
sub main_loop {
my $self = shift;
local $| = 1;
while (1) {
print "waiting for connections..." if $self->{"Verbose"};
my @ready = $self->{"select"}->can_read;
foreach my $sock (@ready) {
my $proto = getprotobynumber($sock->protocol);
if (!$proto) {
print "ERROR: connection with unknown protocol\n"
if $self->{"Verbose"};
} elsif (lc($proto) eq "tcp") {
my $client = $sock->accept;
$self->tcp_connection($client);
} elsif (lc($proto) eq "udp") {
$self->udp_connection($sock);
} else {
print "ERROR: connection with unsupported protocol $proto\n"
if $self->{"Verbose"};
}
}
}
}
1;
__END__
=head1 NAME
Net::DNS::Nameserver - DNS server class
=head1 SYNOPSIS
C<use Net::DNS::Nameserver;>
=head1 DESCRIPTION
Instances of the C<Net::DNS::Nameserver> class represent simple DNS server
objects. See L</EXAMPLE> for an example.
=head1 METHODS
=head2 new
my $ns = Net::DNS::Nameserver->new(
LocalAddr => "10.1.2.3",
LocalPort => "5353",
ReplyHandler => \&reply_handler,
Verbose => 1
);
Creates a nameserver object. Attributes are:
LocalAddr IP address on which to listen. Defaults to INADDR_ANY.
LocalPort Port on which to listen. Defaults to 53.
ReplyHandler Reference to reply-handling subroutine. Required.
Verbose Print info about received queries. Defaults to 0 (off).
The ReplyHandler subroutine is passed the query name, query class,
query type and optionally an argument containing header bit settings
(see below). It must return the response code and references to the
answer, authority, and additional sections of the response. 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 there is an optional argument containing an
hashref with the settings for the C<aa>, C<ra>, and C<ad>
header bits. The argument is of the form
C<< { ad => 1, aa => 0, ra => 1 } >>.
See RFC 1035 and the IANA dns-parameters file for more information:
ftp://ftp.rfc-editor.org/in-notes/rfc1035.txt
http://www.isi.edu/in-notes/iana/assignments/dns-parameters
The nameserver will listen for both UDP and TCP connections. On
Unix-like systems, the program will probably have to run as root
to listen on the default port, 53. A non-privileged user should
be able to listen on ports 1024 and higher.
Returns a Net::DNS::Nameserver object, or undef if the object
couldn't be created.
See L</EXAMPLE> for an example.
=head2 main_loop
$ns->main_loop;
Start accepting queries.
=head1 EXAMPLE
The following example will listen on port 5353 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 $peerhost variable catches the IP address of the peer host, so that
additional filtering on its basis may be applied.
#!/usr/bin/perl
use Net::DNS;
use strict;
use warnings;
sub reply_handler {
my ($qname, $qclass, $qtype, $peerhost) = @_;
my ($rcode, @ans, @auth, @add);
if ($qtype eq "A") {
my ($ttl, $rdata) = (3600, "10.1.2.3");
push @ans, Net::DNS::RR->new("$qname $ttl $qclass $qtype $rdata");
$rcode = "NOERROR";
} else {
$rcode = "NXDOMAIN";
}
# mark the answer as authoritive (by setting the 'aa' flag
return ($rcode, \@ans, \@auth, \@add, { aa => 1 });
}
my $ns = Net::DNS::Nameserver->new(
LocalPort => 5353,
ReplyHandler => \&reply_handler,
Verbose => 1,
) || die "couldn't create nameserver object\n";
$ns->main_loop;
=head1 BUGS
Net::DNS::Nameserver objects can handle only one query at a time.
=head1 COPYRIGHT
Copyright (c) 1997-2002 Michael Fuhr.
Portions Copyright (c) 2002-2003 Chris Reinhardt.
All rights reserved. This program is free software; you may redistribute
it and/or modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<perl(1)>, L<Net::DNS>, L<Net::DNS::Resolver>, L<Net::DNS::Packet>,
L<Net::DNS::Update>, L<Net::DNS::Header>, L<Net::DNS::Question>,
L<Net::DNS::RR>, RFC 1035
=cut