1#!/usr/bin/perl 2# 3# Copyright (C) Internet Systems Consortium, Inc. ("ISC") 4# 5# This Source Code Form is subject to the terms of the Mozilla Public 6# License, v. 2.0. If a copy of the MPL was not distributed with this 7# file, you can obtain one at https://mozilla.org/MPL/2.0/. 8# 9# See the COPYRIGHT file distributed with this work for additional 10# information regarding copyright ownership. 11 12# This is a TCP-only DNS server whose aim is to facilitate testing how dig 13# copes with prematurely closed TCP connections. 14# 15# This server can be configured (through a separate control socket) with a 16# series of responses to send for subsequent incoming TCP DNS queries. Only 17# one query is handled before closing each connection. In order to keep things 18# simple, the server is not equipped with any mechanism for handling malformed 19# queries. 20# 21# Available response types are defined in the %response_types hash in the 22# getAnswerSection() function below. Each RR returned is generated dynamically 23# based on the QNAME found in the incoming query. 24 25use IO::File; 26use Net::DNS; 27use Net::DNS::Packet; 28 29use strict; 30 31# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early 32local $SIG{PIPE} = 'IGNORE'; 33 34# Flush logged output after every line 35local $| = 1; 36 37my $server_addr = "10.53.0.5"; 38if (@ARGV > 0) { 39 $server_addr = @ARGV[0]; 40} 41 42my $mainport = int($ENV{'PORT'}); 43if (!$mainport) { $mainport = 5300; } 44my $ctrlport = int($ENV{'EXTRAPORT1'}); 45if (!$ctrlport) { $ctrlport = 5301; } 46 47my $ctlsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 48 LocalPort => $ctrlport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 49 50my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 51 LocalPort => $mainport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 52 53my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!"; 54print $pidf "$$\n" or die "cannot write pid file: $!"; 55$pidf->close or die "cannot close pid file: $!";; 56sub rmpid { unlink "ans.pid"; exit 1; }; 57 58$SIG{INT} = \&rmpid; 59$SIG{TERM} = \&rmpid; 60 61my @response_sequence = ("complete_axfr"); 62my $connection_counter = 0; 63 64# Return the next answer type to send, incrementing the connection counter and 65# making sure the latter does not exceed the size of the array holding the 66# configured response sequence. 67sub getNextResponseType { 68 my $response_type = $response_sequence[$connection_counter]; 69 70 $connection_counter++; 71 $connection_counter %= scalar(@response_sequence); 72 73 return $response_type; 74} 75 76# Return an array of resource records comprising the answer section of a given 77# response type. 78sub getAnswerSection { 79 my ($response_type, $qname) = @_; 80 81 my %response_types = ( 82 no_response => [], 83 84 partial_axfr => [ 85 Net::DNS::RR->new("$qname 300 IN SOA . . 0 0 0 0 300"), 86 Net::DNS::RR->new("$qname NS ."), 87 ], 88 89 complete_axfr => [ 90 Net::DNS::RR->new("$qname 300 IN SOA . . 0 0 0 0 300"), 91 Net::DNS::RR->new("$qname NS ."), 92 Net::DNS::RR->new("$qname 300 IN SOA . . 0 0 0 0 300"), 93 ], 94 ); 95 96 return $response_types{$response_type}; 97} 98 99 100# Generate a Net::DNS::Packet containing the response to send on the current 101# TCP connection. If the answer section of the response is determined to be 102# empty, no data will be sent on the connection at all (immediate EOF). 103sub generateResponse { 104 my ($buf) = @_; 105 my $request; 106 107 if ($Net::DNS::VERSION > 0.68) { 108 $request = new Net::DNS::Packet(\$buf, 0); 109 $@ and die $@; 110 } else { 111 my $err; 112 ($request, $err) = new Net::DNS::Packet(\$buf, 0); 113 $err and die $err; 114 } 115 116 my @questions = $request->question; 117 my $qname = $questions[0]->qname; 118 my $qtype = $questions[0]->qtype; 119 my $qclass = $questions[0]->qclass; 120 my $id = $request->header->id; 121 122 my $packet = new Net::DNS::Packet($qname, $qtype, $qclass); 123 $packet->header->qr(1); 124 $packet->header->aa(1); 125 $packet->header->id($id); 126 127 my $response_type = getNextResponseType(); 128 my $answers = getAnswerSection($response_type, $qname); 129 for my $rr (@$answers) { 130 $packet->push("answer", $rr); 131 } 132 133 print " Sending \"$response_type\" response\n"; 134 135 return $packet->data if @$answers; 136} 137 138my $rin; 139my $rout; 140for (;;) { 141 $rin = ''; 142 vec($rin, fileno($ctlsock), 1) = 1; 143 vec($rin, fileno($tcpsock), 1) = 1; 144 145 select($rout = $rin, undef, undef, undef); 146 147 if (vec($rout, fileno($ctlsock), 1)) { 148 my $conn = $ctlsock->accept; 149 @response_sequence = split(' ', $conn->getline); 150 $connection_counter = 0; 151 print "Response sequence set to: @response_sequence\n"; 152 $conn->close; 153 } elsif (vec($rout, fileno($tcpsock), 1)) { 154 my $buf; 155 my $lenbuf; 156 my $conn = $tcpsock->accept; 157 my $n = $conn->sysread($lenbuf, 2); 158 die unless $n == 2; 159 my $len = unpack("n", $lenbuf); 160 $n = $conn->sysread($buf, $len); 161 die unless $n == $len; 162 print "TCP request\n"; 163 my $response = generateResponse($buf); 164 if ($response) { 165 $len = length($response); 166 $n = $conn->syswrite(pack("n", $len), 2); 167 $n = $conn->syswrite($response, $len); 168 print " Sent: $n chars via TCP\n"; 169 } else { 170 print " No response sent\n"; 171 } 172 $conn->close; 173 } 174} 175