1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
#!/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: forces TCP retry
return (pack("nnnnnn", $id, 0x8600, 0, 0, 0, 0));
} elsif ($qname eq "tcpalso.no-questions") {
# QR, REFUSED: forces TCP retry
return (pack("nnnnnn", $id, 0x8205, 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"));
if ($qname eq "tcpalso.no-questions") {
# for this qname we also return a bad reply over TCP
# QR, REFUSED, no question section
push (@results, pack("nnnnnn", $id, 0x8005, 0, 0, 0, 0));
} else {
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;
}
}
|
