#!/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. # # Ad hoc name server # use IO::File; use IO::Socket; use Net::DNS; use Net::DNS::Packet; # 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 $localport = int($ENV{'PORT'}); if (!$localport) { $localport = 5300; } my $server_addr = "10.53.0.3"; 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 => $localport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 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 handleQuery { my $buf = shift; my $packet; if ($Net::DNS::VERSION > 0.68) { $packet = new Net::DNS::Packet(\$buf, 0); $@ and die $@; } else { my $err; ($packet, $err) = new Net::DNS::Packet(\$buf, 0); $err and die $err; } print "REQUEST:\n"; $packet->print; $packet->header->qr(1); $packet->header->aa(1); my @questions = $packet->question; my $qname = $questions[0]->qname; my $qtype = $questions[0]->qtype; if ($qname eq "example.net" && $qtype eq "NS") { $packet->push("answer", new Net::DNS::RR($qname . " 300 NS ns.example.net")); $packet->push("additional", new Net::DNS::RR("ns.example.net 300 A 10.53.0.3")); } elsif ($qname eq "ns.example.net") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 10.53.0.3")); } elsif ($qname eq "nodata.example.net") { # Do not add a SOA RRset. } elsif ($qname eq "nxdomain.example.net") { # Do not add a SOA RRset. $packet->header->rcode(NXDOMAIN); } elsif ($qname eq "www.example.net") { # Data for address/alias filtering. if ($qtype eq "A") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 192.0.2.1")); } elsif ($qtype eq "AAAA") { $packet->push("answer", new Net::DNS::RR($qname . " 300 AAAA 2001:db8:beef::1")); } } elsif ($qname eq "badcname.example.net") { $packet->push("answer", new Net::DNS::RR($qname . " 300 CNAME badcname.example.org")); } elsif (($qname eq "baddname.example.net" || $qname eq "gooddname.example.net") && $qtype eq "NS") { $packet->push("authority", new Net::DNS::RR("example.net IN SOA (1 2 3 4 5)")) } elsif ($qname eq "foo.baddname.example.net") { $packet->push("answer", new Net::DNS::RR("baddname.example.net" . " 300 DNAME baddname.example.org")); } elsif ($qname eq "foo.gooddname.example.net") { $packet->push("answer", new Net::DNS::RR("gooddname.example.net" . " 300 DNAME gooddname.example.org")); } elsif ($qname eq "goodcname.example.net") { $packet->push("answer", new Net::DNS::RR($qname . " 300 CNAME goodcname.example.org")); } elsif ($qname =~ /^nodata\.example\.net$/i) { $packet->header->aa(1); } elsif ($qname =~ /^nxdomain\.example\.net$/i) { $packet->header->aa(1); $packet->header->rcode(NXDOMAIN); } elsif ($qname eq "large-referral.example.net") { for (my $i = 1; $i < 1000; $i++) { $packet->push("authority", new Net::DNS::RR("large-referral.example.net 300 NS ns" . $i . ".fake.redirect.com")); } # No glue records } elsif ($qname eq "foo.bar.sub.tld1") { $packet->push("answer", new Net::DNS::RR("$qname 300 TXT baz")); } elsif ($qname eq "cname.sub.example.org") { $packet->push("answer", new Net::DNS::RR($qname . " 300 CNAME ok.sub.example.org")); } elsif ($qname eq "ok.sub.example.org") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 192.0.2.1")); } elsif ($qname eq "www.dname.sub.example.org") { $packet->push("answer", new Net::DNS::RR("dname.sub.example.org" . " 300 DNAME ok.sub.example.org")); } elsif ($qname eq "www.ok.sub.example.org") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 192.0.2.1")); } elsif ($qname eq "foo.glue-in-answer.example.org") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 192.0.2.1")); } elsif ($qname eq "ns.example.net") { $packet->push("answer", new Net::DNS::RR($qname . " 300 A 10.53.0.3")); } else { $packet->push("answer", new Net::DNS::RR("www.example.com 300 A 1.2.3.4")); } print "RESPONSE:\n"; $packet->print; return $packet->data; } # 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 $result = handleQuery($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 $result = handleQuery($buf); $len = length($result); $conn->syswrite(pack("n", $len), 2); $n = $conn->syswrite($result, $len); print " Sent: $n chars via TCP\n"; } $conn->close; } }