#!/usr/bin/env perl
#
# Copyright (C) 2014  Internet Systems Consortium, Inc. ("ISC")
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
# OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

use strict;
use warnings;

use IO::File;
use Getopt::Long;
use Net::DNS::Nameserver;

my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!";
print $pidf "$$\n" or die "cannot write pid file: $!";
$pidf->close or die "cannot close pid file: $!";
sub rmpid { unlink "ans.pid"; exit 1; };

$SIG{INT} = \&rmpid;
$SIG{TERM} = \&rmpid;

my $count = 0;
my $send_response = 0;

my $localaddr = "10.53.0.4";
my $localport = 5300;
my $verbose = 0;

sub reply_handler {
    my ($qname, $qclass, $qtype, $peerhost, $query, $conn) = @_;
    my ($rcode, @ans, @auth, @add);

    print ("request: $qname/$qtype\n");
    STDOUT->flush();

    $count += 1;

    if ($qname eq "count" ) {
        if ($qtype eq "TXT") {
            my ($ttl, $rdata) = (0, "$count");
            my $rr = new Net::DNS::RR("$qname $ttl $qclass $qtype $rdata");
            push @ans, $rr;
            print ("\tcount: $count\n");
        }
        $rcode = "NOERROR";
    } elsif ($qname eq "reset" ) {
        $count = 0;
        $send_response = 0;
        $rcode = "NOERROR";
    } elsif ($qname eq "direct.example.net" ) {
        if ($qtype eq "A") {
            my ($ttl, $rdata) = (3600, $localaddr);
            my $rr = new Net::DNS::RR("$qname $ttl $qclass $qtype $rdata");
            push @ans, $rr;
        }
        $rcode = "NOERROR";
    } elsif( $qname =~ /^ns1\.(\d+)\.example\.net$/ ) {
        my $next = ($1 + 1) * 16;
        for (my $i = 1; $i < 16; $i++) {
            my $s = $next + $i;
            my $rr = new Net::DNS::RR("$1.example.net 86400 $qclass NS ns1.$s.example.net");
            push @auth, $rr;
            $rr = new Net::DNS::RR("ns1.$s.example.net 86400 $qclass A 10.53.0.7");
            push @add, $rr;
        }
        $rcode = "NOERROR";
    } else {
        $rcode = "NXDOMAIN";
    }

    # mark the answer as authoritive (by setting the 'aa' flag
    return ($rcode, \@ans, \@auth, \@add, { aa => 1 });
}

GetOptions(
    'port=i' => \$localport,
    'verbose!' => \$verbose,
);

my $ns = Net::DNS::Nameserver->new(
    LocalAddr => $localaddr,
    LocalPort => $localport,
    ReplyHandler => \&reply_handler,
    Verbose => $verbose,
);

$ns->main_loop;