package Net::DNS::Nameserver; # # $Id: Nameserver.pm 388 2005-06-22 10:06:05Z olaf $ # BEGIN { eval { require bytes; } } use Net::DNS; use IO::Socket; use IO::Socket::INET; use IO::Select; use Carp qw(cluck); use strict; use vars qw($VERSION $has_inet6 @DEFAULT_ADDR $DEFAULT_PORT ); $VERSION = (qw$LastChangedRevision: 388 $)[1]; #@DEFAULT_ADDR is set in the BEGIN block $DEFAULT_PORT=53; BEGIN { my $force_inet4_only=0; if ($force_inet4_only){ $has_inet6=0; }elsif ( eval {require Socket6;} && # INET6 more recent than 2.01 will not work; sorry. eval {require IO::Socket::INET6; IO::Socket::INET6->VERSION("2.00");}) { import Socket6; $has_inet6=1; no strict 'subs'; @DEFAULT_ADDR= ( 0 ); }else{ $has_inet6=0; @DEFAULT_ADDR= ( INADDR_ANY ); } } #------------------------------------------------------------------------------ #------------------------------------------------------------------------------ # Constructor. #------------------------------------------------------------------------------ sub new { my ($class, %self) = @_; if (!$self{"ReplyHandler"} || !ref($self{"ReplyHandler"})) { cluck "No reply handler!"; return; } my $addr; my $port; # make sure we have an array. $self{"LocalAddr"}= \@DEFAULT_ADDR unless defined $self{"LocalAddr"}; $self{"LocalAddr"}= [ $self{"LocalAddr"} ] unless (ref($self{"LocalAddr"})eq "ARRAY"); my @localaddresses = @{$self{"LocalAddr"}}; my @sock_tcp; # All the TCP sockets we will listen to. my @sock_udp; # All the UDP sockets we will listen to. foreach my $localaddress (@localaddresses){ print "Dealing with $localaddress...\n" if $self{"Verbose"}; my $sock_tcp ; if ($has_inet6){ $addr = $localaddress; $port = $self{"LocalPort"} || $DEFAULT_PORT; #-------------------------------------------------------------------------- # Create the IPv4/IPv6 ONLY TCP socket. #-------------------------------------------------------------------------- print "creating TCP socket for $localaddress" if $self{"Verbose"}; $sock_tcp = IO::Socket::INET6->new( LocalAddr => $addr, LocalPort => $port, Listen => 5, Proto => "tcp", Reuse => 1, ); if (! $sock_tcp) { cluck "couldn't create TCP socket: $!"; return; } push @sock_tcp, $sock_tcp; print "done.\n" if $self{"Verbose"}; }else{ $addr = $localaddress || inet_ntoa($DEFAULT_ADDR[0]); $port = $self{"LocalPort"} || $DEFAULT_PORT; #-------------------------------------------------------------------------- # Create the IPv4 ONLY TCP socket. #-------------------------------------------------------------------------- print "creating TCP socket for $localaddress" if $self{"Verbose"}; $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; } push @sock_tcp, $sock_tcp; print "done.\n" if $self{"Verbose"}; } #-------------------------------------------------------------------------- # Create the UDP Socket. #-------------------------------------------------------------------------- print "creating UDP socket..." if $self{"Verbose"}; my $sock_udp; if ($has_inet6){ $sock_udp = IO::Socket::INET6->new( LocalAddr => $addr, LocalPort => $port, Proto => "udp", ); }else{ $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"}; push @sock_udp, $sock_udp; } #-------------------------------------------------------------------------- # Create the Select object. #-------------------------------------------------------------------------- $self{"select"} = IO::Select->new; foreach my $sock_tcp (@sock_tcp){ $self{"select"}->add($sock_tcp); } foreach my $sock_udp (@sock_udp){ $self{"select"}->add($sock_udp); } #-------------------------------------------------------------------------- # Return the object. #-------------------------------------------------------------------------- my $self = bless \%self, $class; return $self; } #------------------------------------------------------------------------------ # make_reply - Make a reply packet. #------------------------------------------------------------------------------ sub make_reply { my ($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 $reply; } #------------------------------------------------------------------------------ # tcp_connection - Handle a TCP connection. #------------------------------------------------------------------------------ sub tcp_connection { my ($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 $self->{"Verbose"}; } #------------------------------------------------------------------------------ # udp_connection - Handle a UDP connection. #------------------------------------------------------------------------------ sub udp_connection { my ($self, $sock) = @_; my $buf = ""; my ($peerhost,$peerport); $sock->recv($buf, &Net::DNS::PACKETSZ); print "UDP connection from ", $sock->peerhost, ":", $sock->peerport, "\n" if $self->{"Verbose"}; 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"}; } #------------------------------------------------------------------------------ # main_loop - Main nameserver loop. #------------------------------------------------------------------------------ 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 =head1 DESCRIPTION Instances of the C class represent simple DNS server objects. See L 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 ); my $ns = Net::DNS::Nameserver->new( LocalAddr => ['::1' , '127.0.0.1' ], 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 LocalAddr attribute may alternatively be specified as a list of IP addresses to liten to. If IO::Socket::INET6 and Socket6 are available on the system you can also list IPv6 addresses and the default is '0' (listen on all interfaces on IPv6 and IPv4); 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, C, and C 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 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) 2002-2004 Chris Reinhardt. Portions Copyright (c) 2005 O.M, Kolkman, RIPE NCC. 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, L, L, L, L, L, L, L, RFC 1035 =cut