use Net::DNS::Nameserver;
my $nameserver = new Net::DNS::Nameserver(
LocalAddr => ['::1' , '127.0.0.1'],
ZoneFile => "filename"
);
my $nameserver = new Net::DNS::Nameserver(
LocalAddr => '10.1.2.3',
LocalPort => 5353,
ReplyHandler => \&reply_handler
);
It is not, nor will it ever be, a general-purpose DNS nameserver implementation.
See ``EXAMPLE'' for an example.
$nameserver = new Net::DNS::Nameserver(
LocalAddr => ['::1' , '127.0.0.1'],
ZoneFile => "filename"
);
$nameserver = new Net::DNS::Nameserver(
LocalAddr => '10.1.2.3',
LocalPort => 5353,
ReplyHandler => \&reply_handler,
Verbose => 1,
Truncate => 0
);
Returns a Net::DNS::Nameserver object, or undef 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 loopback address
LocalPort Port on which to listen Defaults to 53
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)
The LocalAddr attribute may alternatively be specified as a list of IP addresses to listen to. If the IO::Socket::IP library package is available on the system this may also include IPv6 addresses.
The ReplyHandler subroutine is passed the query name, query class, query type and optionally an argument containing the peerhost, the incoming query, and the name of the incoming socket (sockethost). 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 optionmask "{ $optioncode => $value, $optionname => $value }".
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.
UDP reply truncation functionality was introduced in VERSION 830. 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" to 0 and truncate the reply packet in the code of the ReplyHandler.
See ``EXAMPLE'' for an example.
$ns->main_loop;
Start accepting queries. Calling main_loop never returns.
$ns->loop_once( [TIMEOUT_IN_SECONDS] );
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.
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 AXFR has requested a huge amount of data that the OS 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.
In case loop_once accepted a TCP 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 loop_once() 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 ``loop_once'' twice.
A code fragment like:
$ns->loop_once(10);
while( $ns->get_open_tcp() ){
$ns->loop_once(0);
}
Would wait for 10 seconds for the initial connection and would then process all TCP sockets until none is left.
#!/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} . "\n";
$query->print;
if ( $qtype eq "A" && $qname eq "foo.example.com" ) {
my ( $ttl, $rdata ) = ( 3600, "10.1.2.3" );
my $rr = new Net::DNS::RR("$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 = new Net::DNS::Nameserver(
LocalPort => 5353,
ReplyHandler => \&reply_handler,
Verbose => 1
) || die "couldn't create nameserver object\n";
$ns->main_loop;
Portions Copyright (c)2002-2004 Chris Reinhardt.
Portions Copyright (c)2005 Robert Martin-Legene.
Portions Copyright (c)2005-2009 O.M, Kolkman, RIPE NCC.
Portions Copyright (c)2017 Dick Franks.
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.