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#!/usr/bin/perl
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# SPDX-License-Identifier: MPL-2.0
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, you can obtain one at https://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.
use IO::File;
use IO::Socket;
use Data::Dumper;
use Net::DNS;
use Net::DNS::Packet;
use strict;
# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early
local $SIG{PIPE} = 'IGNORE';
# Flush logged output after every line
local $| = 1;
my $server_addr = "10.53.0.8";
my $localport = int($ENV{'PORT'});
if (!$localport) { $localport = 5300; }
my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
LocalPort => $localport, Proto => "udp", Reuse => 1) or die "$!";
my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
LocalPort => $localport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";
print "listening on $server_addr:$localport.\n";
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;
$SIG{TERM} = \&rmpid;
sub handleUDP {
my ($buf) = @_;
my $request;
if ($Net::DNS::VERSION > 0.68) {
$request = new Net::DNS::Packet(\$buf, 0);
$@ and die $@;
} else {
my $err;
($request, $err) = new Net::DNS::Packet(\$buf, 0);
$err and die $err;
}
my @questions = $request->question;
my $qname = $questions[0]->qname;
my $qtype = $questions[0]->qtype;
my $qclass = $questions[0]->qclass;
my $id = $request->header->id;
my $response = new Net::DNS::Packet($qname, $qtype, $qclass);
$response->header->qr(1);
$response->header->aa(1);
$response->header->tc(0);
$response->header->id($id);
# Responses to queries for no-questions/NS and ns.no-questions/A are
# _not_ malformed or truncated.
if ($qname eq "no-questions" && $qtype eq "NS") {
$response->push("answer", new Net::DNS::RR($qname . " 300 NS ns.no-questions"));
$response->push("additional", new Net::DNS::RR("ns.no-questions. 300 A 10.53.0.8"));
return $response->data;
} elsif ($qname eq "ns.no-questions") {
$response->push("answer", new Net::DNS::RR($qname . " 300 A 10.53.0.8"))
if ($qtype eq "A");
return $response->data;
} elsif ($qname =~ /\.formerr-to-all$/) {
$response->header->rcode("FORMERR");
return $response->data;
}
# don't use Net::DNS to construct the header only reply as early
# versions just get it completely wrong.
if ($qname eq "truncated.no-questions") {
# QR, AA, TC
return (pack("nnnnnn", $id, 0x8600, 0, 0, 0, 0));
}
# QR, AA
return (pack("nnnnnn", $id, 0x8400, 0, 0, 0, 0));
}
sub handleTCP {
my ($buf) = @_;
my $request;
if ($Net::DNS::VERSION > 0.68) {
$request = new Net::DNS::Packet(\$buf, 0);
$@ and die $@;
} else {
my $err;
($request, $err) = new Net::DNS::Packet(\$buf, 0);
$err and die $err;
}
my @questions = $request->question;
my $qname = $questions[0]->qname;
my $qtype = $questions[0]->qtype;
my $qclass = $questions[0]->qclass;
my $id = $request->header->id;
my @results = ();
my $response = new Net::DNS::Packet($qname, $qtype, $qclass);
$response->header->qr(1);
$response->header->aa(1);
$response->header->id($id);
$response->push("answer", new Net::DNS::RR("$qname 300 A 1.2.3.4"));
push(@results, $response->data);
return \@results;
}
# Main
my $rin;
my $rout;
for (;;) {
$rin = '';
vec($rin, fileno($tcpsock), 1) = 1;
vec($rin, fileno($udpsock), 1) = 1;
select($rout = $rin, undef, undef, undef);
if (vec($rout, fileno($udpsock), 1)) {
printf "UDP request\n";
my $buf;
$udpsock->recv($buf, 512);
my $result = handleUDP($buf);
my $num_chars = $udpsock->send($result);
print " Sent $num_chars bytes via UDP\n";
} elsif (vec($rout, fileno($tcpsock), 1)) {
my $conn = $tcpsock->accept;
my $buf;
for (;;) {
my $lenbuf;
my $n = $conn->sysread($lenbuf, 2);
last unless $n == 2;
my $len = unpack("n", $lenbuf);
$n = $conn->sysread($buf, $len);
last unless $n == $len;
print "TCP request\n";
my $result = handleTCP($buf);
foreach my $response (@$result) {
$len = length($response);
$n = $conn->syswrite(pack("n", $len), 2);
$n = $conn->syswrite($response, $len);
print " Sent: $n chars via TCP\n";
}
}
$conn->close;
}
}
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