| Subject: | rcode not set if lookup fails and rcode=NXDOMAIN or rcode=SERVFAIL |
v5.8.8 built for x86_64-linux-thread-multi
perl-Net-DNS-0.57-1
x86-64 both on Fedora5 and RHEL4.2
Net::DNS does not appear to set the value of ->{header}->{rcode} (or
incidentally ->{header}->{ancount}) unless the query is successful.
Inline is the output of this script with the resolver set to debug
output. You can compare the obviously set rcode values in the header vs
the undefined/empty values in the output. Attached is a script I've
just written with this you can use to verify.
Cheers,
/eli
######### successful query: ############
[estair@adroit bin]$ clear ; ./check_dns_host.pl -q FORWARD -H
google.com -w 100 -c 200 -r 3
;; search(google.com, A, IN)
;; query(google.com, A, IN)
;; setting up an AF_INET() family type UDP socket
;; send_udp(10.65.1.108:53)
;; answer from 10.65.1.108:53 : 76 bytes
;; HEADER SECTION
;; id = 15376
;; qr = 1 opcode = QUERY aa = 0 tc = 0 rd = 0
;; ra = 1 ad = 0 cd = 0 rcode = NOERROR
;; qdcount = 1 ancount = 3 nscount = 0 arcount = 0
;; QUESTION SECTION (1 record)
;; google.com. IN A
;; ANSWER SECTION (3 records)
google.com. 118 IN A 64.233.187.99
google.com. 118 IN A 64.233.167.99
google.com. 118 IN A 72.14.207.99
;; AUTHORITY SECTION (0 records)
;; ADDITIONAL SECTION (0 records)
$query_returncode: NOERROR
$query->{header}->{ancount}: 3
$query->{header}->{rcode}: NOERROR
$query_returncode: NOERROR
DNS OK: ANSWERS=(3) QUERY_RETURNVAL=(64.233.187.99 64.233.167.99
72.14.207.99) ELAPSED=(5 ms) | DurationMS=5
######### failed query: ############
[estair@adroit bin]$ clear ; ./check_dns_host.pl -q FORWARD -H
blah.google.com -w 100 -c 200 -r 3
;; search(blah.google.com, A, IN)
;; query(blah.google.com, A, IN)
;; setting up an AF_INET() family type UDP socket
;; send_udp(10.65.1.108:53)
;; answer from 10.65.1.108:53 : 179 bytes
;; HEADER SECTION
;; id = 4216
;; qr = 1 opcode = QUERY aa = 0 tc = 0 rd = 0
;; ra = 1 ad = 0 cd = 0 rcode = NOERROR
;; qdcount = 1 ancount = 0 nscount = 4 arcount = 4
;; QUESTION SECTION (1 record)
;; blah.google.com. IN A
;; ANSWER SECTION (0 records)
;; AUTHORITY SECTION (4 records)
google.com. 85856 IN NS ns3.google.com.
google.com. 85856 IN NS ns4.google.com.
google.com. 85856 IN NS ns1.google.com.
google.com. 85856 IN NS ns2.google.com.
;; ADDITIONAL SECTION (4 records)
ns3.google.com. 85856 IN A 216.239.36.10
ns4.google.com. 85856 IN A 216.239.38.10
ns1.google.com. 85856 IN A 216.239.32.10
ns2.google.com. 85856 IN A 216.239.34.10
;; search(blah.google.com.lucasfilm.com, A, IN)
;; query(blah.google.com.lucasfilm.com, A, IN)
;; setting up an AF_INET() family type UDP socket
;; send_udp(10.65.1.108:53)
;; answer from 10.65.1.108:53 : 132 bytes
;; HEADER SECTION
;; id = 4217
;; qr = 1 opcode = QUERY aa = 1 tc = 0 rd = 0
;; ra = 1 ad = 0 cd = 0 rcode = NXDOMAIN
;; qdcount = 1 ancount = 0 nscount = 1 arcount = 0
;; QUESTION SECTION (1 record)
;; blah.google.com.lucasfilm.com. IN A
;; ANSWER SECTION (0 records)
;; AUTHORITY SECTION (1 record)
lucasfilm.com. 3600 IN SOA lucas-dc2.lucas.alllucas.com.
hostmaster.lucas.alllucas.com. (
2001401971 ; Serial
900 ; Refresh
600 ; Retry
86400 ; Expire
3600 ) ; Minimum TTL
;; ADDITIONAL SECTION (0 records)
$query_returncode:
$query->{header}->{ancount}:
$query->{header}->{rcode}:
$query_returncode:
DNS : ANSWERS=() QUERY_RETURNVAL=() ELAPSED=(9 ms) | DurationMS=9
| Subject: | check_dns_host.pl |
#!/usr/bin/perl
#FILE: check_dns.pl
#SYNOPSIS: check A/PTR records for a host. Added support for checking matching returnval vs. a string, and #of responses.
#use strict;
#use warnings;
use Net::DNS;
use Getopt::Long;
use Pod::Usage;
use Time::HiRes qw( usleep ualarm gettimeofday tv_interval );
### Define ARGV options:
my ($host,$match,$server,$timeout,$wlevel,$clevel,$retvalnum,$query_type);
GetOptions(
"H=s" => \$host,
"m=s" => \$match,
"s=s" => \$server,
"q=s" => \$query_type,
"t=i" => \$timeout,
"r=i" => \$retvalnum,
"w=i" => \$wlevel,
"c=i" => \$clevel
);
if(!$timeout){$timeout=10};
alarm($timeout);
$SIG{ALRM} = sub {print "$0 timed out.\n"; exit 2;};
if(!$host || !$wlevel || !$clevel){
pod2usage("$0: fixme");
exit 3;
}
if($wlevel>=$clevel){
pod2usage("$0: fixme");
exit 3; # Nagios: unknown
}
######################################################################################
### START code:
######################################################################################
### define program vars:
my ($header,$exitstate,@retval,$checkfailed);
# Initialize the DNS Resolver package and start timer:
my $res = Net::DNS::Resolver->new(
recurse => 0,
debug => 1,
);
my ($t0, $t1);
$t0 = [gettimeofday];
### define program flow:
&query_run;
&query_lint;
&query_compile;
&eval;
######################################################################################
### Execute defined query:
# Perform the lookup, and set status values:
sub query_run {
$query = $res->search("$host");
# Calculate time elapsed for lookup:
$t1 = [gettimeofday];
$elapsed = int (1000 * tv_interval ( $t0, $t1));
$query_returncode = ($query->{header}->{rcode});
$query_count = ($query->{header}->{ancount});
} #/sub query_run
sub query_compile {
# Populate comparison array based on query type:
if ($query_type eq "FORWARD") { # A queries:
foreach my $rr ($query->answer) {
next unless $rr->type eq "A";
my $ip = $rr->address;
push (@retval, $ip);
}
} #/if ($query_type eq "FORWARD")
if ($query_type eq "REVERSE") { # PTR queries:
foreach my $rr ($query->answer) {
next unless $rr->type eq "PTR";
my $hostname = $rr->ptrdname;
push (@retval, $hostname);
}
} #/if ($query_type eq "REVERSE")
} #/sub query_compile
sub query_lint {
print "\$query_returncode: $query_returncode \n";
unless ($query_returncode) {
print "\$query->{header}->{ancount}: $query->{header}->{ancount} \n";
print "\$query->{header}->{rcode}: $query->{header}->{rcode} \n";
$querycheck = "FAILED";
&exit;
}
print "\$query->{header}->{ancount}: $query->{header}->{ancount} \n";
print "\$query->{header}->{rcode}: $query->{header}->{rcode} \n";
}
######################################################################################
### FUNCTION: eval
### Check for failure conditions:
sub eval {
# Query failed:
if ($query_returncode ne "NOERROR") {
$exitstate = "CRITICAL";
&exit;
}
# warn timeout threshhold exceeded:
if ($elapsed > $wlevel) {
$exitstate = "WARNING";
&exit;
}
# crit timeout threshhold exceeded:
if ($elapsed > $clevel) {
$exitstate = "CRITICAL";
&exit;
}
# num query returns out of specified bounds:
if ($retvalnum) {
($retvalnum != $query_count) && ($exitstate = "CRITICAL");
if ($exitstate) {
$checkfailed = qq{"RETVAL:$retvalnum" != "QUERYCOUNT:$query_count"};
&exit;
}
}
# query return does not match specified string:
if ($match) {
foreach my $value (@retval) {
($match eq $value) || ($exitstate = "CRITICAL");
}
if ($exitstate) {
$checkfailed = qq{"MATCH:$match" != "RETVAL:@retval"};
&exit;
}
}
# Yay! all seems OK...
$query_returncode eq "NOERROR" && ($exitstate = "OK");
&exit;
}
######################################################################################
### FUNCTION: exit
sub exit {
print "\$query_returncode: $query_returncode \n";
# Query failures:
if ($queryfailed) {
die "QUERY FAILED";
}
# check failures:
if ($checkfailed) {
print "EXITING ERROR \n";
$output = "DNS $exitstate=($checkfailed) QUERYRETURNCODE=($query_returncode) ANSWERS=($query_count) QUERY_RETURNVAL=(@retval) ELAPSED=(${elapsed} ms) | DurationMS=$elapsed";
} else {
# print "EXITING NOERROR \n";
$output = "DNS $exitstate: ANSWERS=($query_count) QUERY_RETURNVAL=(@retval) ELAPSED=(${elapsed} ms) | DurationMS=$elapsed";
$checkfailed = "";
}
print "$output \n";
exit 2 if(!$query_returncode); # Nagios: Critical
exit 2 if($elapsed>$clevel); # Nagios: Critical
exit 2 if($query_count != $retvalnum); # Nagios: Critical
exit 2 if(!$checkfailed eq ""); # Nagios: Critical
exit 1 if($elapsed>$wlevel); # Nagios: Warning
exit 0; # Nagios: OK
}
### perldoc:
=head1 NAME
check_dns.pl - DNS-Query and Statistics
=head1 SYNOPSIS
check_dns.pl -H host -s server -w wlevel -c clevel [-t timeout]
host: The host to be resolved
server: The DNS-server to ask
timeout: Timeout in seconds
wlevel: Warning treshhold (milliseconds)
clevel: Critical treshhold (milliseconds)
=head1 DESCRIPTION
This asks a server to resolve a host. It returns OK if the process was
successfull and took less than wlevel milliseconds.
It returns a warning if it took less than clevel milliseconds.
Everything else returns critical. (Also, if it takes longer than timeout.)
=head1 PROBLEMS
This contains a hardcoded perl lib directory. Might wanna change this if
running on a machine with only one perl distribution.
Not too reliable timing functions, I suppose.
=head1 AUTHOR
Copyright (c) 2003 Hannes Schulz <mail@hannes-schulz.de>
=cut
#</perldoc>