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# Copyright (C) 2011 Internet Systems Consortium, Inc. ("ISC")
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# Permission to use, copy, modify, and/or distribute this software for any
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# purpose with or without fee is hereby granted, provided that the above
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# copyright notice and this permission notice appear in all copies.
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# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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# AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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# OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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# PERFORMANCE OF THIS SOFTWARE.
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# $Id: ans.pl,v 1.2.2.4 2011-03-18 04:40:30 each Exp $
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# This is the name server from hell. It provides canned
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# responses based on pattern matching the queries, and
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# can be reprogrammed on-the-fly over a TCP connection.
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# The server listens for control connections on port 5301.
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# A control connection is a TCP stream of lines like
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# There can be any number of patterns, each associated
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# with any number of response RRs. Each pattern is a
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# Perl regular expression.
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# Each incoming query is converted into a string of the form
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# "qname qtype" (the printable query domain name, space,
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# printable query type) and matched against each pattern.
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# The first pattern matching the query is selected, and
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# the RR following the pattern line are sent in the
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# answer section of the response.
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# Each new control connection causes the current set of
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# patterns and responses to be cleared before adding new
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# The server handles UDP and TCP queries. Zone transfer
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# responses work, but must fit in a single 64 k message.
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# Now you can add TSIG, just specify key/key data with:
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# /pattern <key> <key_data>/
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# Note that this data will still be sent with any request for
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# pattern, only this data will be signed. Currently, this is only
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# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early
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local $SIG{PIPE} = 'IGNORE';
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# Flush logged output after every line
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# We default to listening on 10.53.0.2 for historical reasons
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# XXX: we should also be able to specify IPv6
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my $server_addr = "10.53.0.2";
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$server_addr = @ARGV[0];
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# XXX: we should also be able to set the port numbers to listen on.
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my $ctlsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
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LocalPort => 5301, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";
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my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
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LocalPort => 5300, Proto => "udp", Reuse => 1) or die "$!";
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my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
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LocalPort => 5300, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";
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print "listening on $server_addr:5300,5301.\n";
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my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!";
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print $pidf "$$\n" or die "cannot write pid file: $!";
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$pidf->close or die "cannot close pid file: $!";;
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sub rmpid { unlink "ans.pid"; exit 1; };
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$SIG{TERM} = \&rmpid;
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my ($packet, $err) = new Net::DNS::Packet(\$buf, 0);
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$packet->header->qr(1);
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$packet->header->aa(1);
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my @questions = $packet->question;
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my $qname = $questions[0]->qname;
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my $qtype = $questions[0]->qtype;
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# get the existing signature if any, and clear the additional section
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while (my $rr = $packet->pop("additional")) {
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if ($rr->type eq "TSIG") {
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foreach $r (@rules) {
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my $pattern = $r->{pattern};
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my($dbtype, $key_name, $key_data) = split(/ /,$pattern);
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print "[handleUDP] $dbtype, $key_name, $key_data \n";
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if ("$qname $qtype" =~ /$dbtype/) {
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foreach $a (@{$r->{answer}}) {
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$packet->push("answer", $a);
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if(defined($key_name) && defined($key_data)) {
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print " Signing the response with " .
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"$key_name/$key_data\n";
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my $tsig = Net::DNS::RR->
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new("$key_name TSIG $key_data");
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# These kluges are necessary because Net::DNS
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# doesn't know how to sign responses. We
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# clear compnames so that the TSIG key and
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# algorithm name won't be compressed, and
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# add one to arcount because the signing
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# function will attempt to decrement it,
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# which is incorrect in a response. Finally
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# we set request_mac to the previous digest.
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$packet->{"compnames"} = {};
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$packet->{"header"}{"arcount"} += 1;
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if (defined($prev_tsig)) {
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my $rmac = pack('n H*',
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$prev_tsig->mac_size,
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$tsig->{"request_mac"} =
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$packet->sign_tsig($tsig);
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return $packet->data;
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# given a stream of data, reads a DNS-formatted name and returns its
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# total length, thus making it possible to skip past it.
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$label_len = unpack("c", $data);
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$data = substr($data, $label_len + 1);
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$len += $label_len + 1;
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} while ($label_len != 0);
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# given a stream of data, reads a DNS wire-format packet and returns
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# its total length, making it possible to skip past it.
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my ($header, $offset) = Net::DNS::Header->parse(\$data);
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for (1 .. $header->qdcount) {
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($q, $offset) = Net::DNS::Question->parse(\$data, $offset);
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for (1 .. $header->ancount) {
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($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
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for (1 .. $header->nscount) {
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($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
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for (1 .. $header->arcount) {
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($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
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# sign_tcp_continuation:
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# This is a hack to correct the problem that Net::DNS has no idea how
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# to sign multiple-message TCP responses. Several data that are included
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# in the digest when signing a query or the first message of a response are
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# omitted when signing subsequent messages in a TCP stream.
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# Net::DNS::Packet->sign_tsig() has the ability to use a custom signing
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# function (specified by calling Packet->sign_func()). We use this
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# function as the signing function for TCP continuations, and it removes
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# the unwanted data from the digest before calling the default sign_hmac
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sub sign_tcp_continuation {
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my ($key, $data) = @_;
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# copy out first two bytes: size of the previous MAC
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my $rmacsize = unpack("n", $data);
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$data = substr($data, 2);
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# copy out previous MAC
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my $rmac = substr($data, 0, $rmacsize);
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$data = substr($data, $rmacsize);
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# try parsing out the packet information
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my $plen = packetlen($data);
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my $pdata = substr($data, 0, $plen);
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$data = substr($data, $plen);
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# remove the keyname, ttl, class, and algorithm name
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$data = substr($data, namelen($data));
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$data = substr($data, 6);
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$data = substr($data, namelen($data));
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# preserve the TSIG data
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my $tdata = substr($data, 0, 8);
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# prepare a new digest and sign with it
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$data = pack("n", $rmacsize) . $rmac . $pdata . $tdata;
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return Net::DNS::RR::TSIG::sign_hmac($key, $data);
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my ($packet, $err) = new Net::DNS::Packet(\$buf, 0);
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$packet->header->qr(1);
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$packet->header->aa(1);
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my @questions = $packet->question;
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my $qname = $questions[0]->qname;
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my $qtype = $questions[0]->qtype;
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# get the existing signature if any, and clear the additional section
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while (my $rr = $packet->pop("additional")) {
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if ($rr->type eq "TSIG") {
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foreach $r (@rules) {
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my $pattern = $r->{pattern};
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my($dbtype, $key_name, $key_data) = split(/ /,$pattern);
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print "[handleTCP] $dbtype, $key_name, $key_data \n";
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if ("$qname $qtype" =~ /$dbtype/) {
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foreach $a (@{$r->{answer}}) {
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$packet->push("answer", $a);
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if(defined($key_name) && defined($key_data)) {
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print " Signing the data with " .
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"$key_name/$key_data\n";
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my $tsig = Net::DNS::RR->
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new("$key_name TSIG $key_data");
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# These kluges are necessary because Net::DNS
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# doesn't know how to sign responses. We
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# clear compnames so that the TSIG key and
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# algorithm name won't be compressed, and
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# add one to arcount because the signing
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# function will attempt to decrement it,
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# which is incorrect in a response. Finally
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# we set request_mac to the previous digest.
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$packet->{"compnames"} = {};
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$packet->{"header"}{"arcount"} += 1;
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if (defined($prev_tsig)) {
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my $rmac = pack('n H*',
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$prev_tsig->mac_size,
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$tsig->{"request_mac"} =
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$tsig->sign_func($signer) if defined($signer);
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$packet->sign_tsig($tsig);
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$signer = \&sign_tcp_continuation;
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Net::DNS::Packet->new(\($packet->data));
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$prev_tsig = $copy->pop("additional");
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push(@results,$packet->data);
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$packet = new Net::DNS::Packet(\$buf, 0);
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$packet->header->qr(1);
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$packet->header->aa(1);
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print " A total of $count_these patterns matched\n";
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vec($rin, fileno($ctlsock), 1) = 1;
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vec($rin, fileno($tcpsock), 1) = 1;
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vec($rin, fileno($udpsock), 1) = 1;
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select($rout = $rin, undef, undef, undef);
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if (vec($rout, fileno($ctlsock), 1)) {
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my $conn = $ctlsock->accept;
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while (my $line = $conn->getline) {
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if ($line =~ m!^/(.*)/$!) {
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$rule = { pattern => $1, answer => [] };
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push(@{$rule->{answer}},
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new Net::DNS::RR($line));
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#print Dumper(@rules);
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#print "+=+=+ $rules[0]->{'pattern'}\n";
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#print "+=+=+ $rules[0]->{'answer'}->[0]->{'rname'}\n";
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#print "+=+=+ $rules[0]->{'answer'}->[0]\n";
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} elsif (vec($rout, fileno($udpsock), 1)) {
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printf "UDP request\n";
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$udpsock->recv($buf, 512);
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my $result = handleUDP($buf);
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my $num_chars = $udpsock->send($result);
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print " Sent $num_chars bytes via UDP\n";
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} elsif (vec($rout, fileno($tcpsock), 1)) {
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my $conn = $tcpsock->accept;
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my $n = $conn->sysread($lenbuf, 2);
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my $len = unpack("n", $lenbuf);
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$n = $conn->sysread($buf, $len);
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last unless $n == $len;
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print "TCP request\n";
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my $result = handleTCP($buf);
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foreach my $response (@$result) {
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$len = length($response);
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$n = $conn->syswrite(pack("n", $len), 2);
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$n = $conn->syswrite($response, $len);
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print " Sent: $n chars via TCP\n";
added
removed
bin/tests/system/ans.pl
