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#!/usr/bin/perl -w
#
# Author: Petter Reinholdtsen <pere@hungry.com>
# Date: 2001-11-09
#
# Check /etc/resolv.conf, and make sure the name servers listed are
# working. It will ignore entries with '# NAGIOSIGNORE' at the end.
use Socket;
use vars qw($host $debug $mincount $trycount $testhost $retval $nagiosmsg);
$retval = 0;
$nagiosmsg = "";
$host = '/usr/bin/host';
$debug = 0;
# There should be at least this many servers in the list
$mincount = 1;
# Try to call host this many times before reporting any bugs
$trycount = 3;
# Which DNS name to look up
$testhost = "www.uio.no";
# Stolen from Logwatch.pm
sub canonical_ipv6_address {
my @a = split /:/, shift;
my @b = qw(0 0 0 0 0 0 0 0);
my $i = 0;
# comparison is numeric, so we use hex function
while (defined $a[0] and $a[0] ne '') {$b[$i++] = hex(shift @a);}
@a = reverse @a;
$i = 7;
while (defined $a[0] and $a[0] ne '') {$b[$i--] = hex(shift @a);}
@b;
}
sub error_with_dns {
local ($count, $ip, $error) = @_;
# Count 1 = Error
# Count 2 = Problem
# Count 3-> = Warning
if (1 == $count) {
$retval = 2;
} elsif (2 == $count) {
$retval = 1 unless ($retval > 0);
}
$nagiosmsg .= "<br>" unless ($nagiosmsg =~ /^$/);
$nagiosmsg .= "/etc/resolv.conf: nameserver #$count $ip: $error";
}
# Check if there is a DNS server running on the given IP address
sub test_dns_server {
local ($ip) = @_;
local ($name) = "";
print "Checking $1\n" if $debug;
# there are other module functions that do this more gracefully
# (such as inet_pton), but we can't guarantee that they are available
# in every system, so we use the built-in gethostbyaddr.
if ($ip =~ /^[\d\.]*$/) {
$PackedAddr = pack('C4', split /\./,$ip);
$name = gethostbyaddr($PackedAddr,AF_INET());
} elsif ($ip =~ /^[0-9a-zA-Z:]*/) {
$PackedAddr = pack('n8', canonical_ipv6_address($ip));
$name = gethostbyaddr($PackedAddr, AF_INET6());
}
return "missing in DNS" if ( ! defined $name );
my $try = $trycount;
my $delay = 1; # Exponensial backoff
for ($try = $trycount; $try; --$try) {
print "Running '$host $testhost $ip 2>/dev/null'\n" if $debug;
local $lookup = `$host $testhost $ip 2>/dev/null`;
print "Reply from host (try=$try):\n $lookup\n" if $debug;
if ($lookup =~ /\sA\s+\d/ || $lookup =~ /has address/ ||
$lookup =~ /domain name pointer/ || $lookup =~ /Name: /) {
return undef; # true
}
print "Sleeping $delay\n" if $debug;
sleep $delay;
$delay += $delay;
}
return "no/bad reply from DNS server";
}
sub check_etc_resolv_conf {
open(RESOLV, "< /etc/resolv.conf") || die "Unable to open /etc/resolv.conf";
local $count = 0;
while (<RESOLV>) {
chomp;
if (/# NAGIOSIGNORE$/) { # Skip lines marked to be ignored
$count++ if (m/^nameserver\s+/); # Count ignored nameservers
next;
}
s/\#.+//; # Skip comments
next if (/^\s*$/); # Skip empty lines
if (/^nameserver\s+(\S+)/) {
$count++;
local ($error) = test_dns_server($1);
if ( defined $error ) {
error_with_dns($count, $1, $error);
}
}
}
close(RESOLV);
if ($count < $mincount) {
$retval = 1 unless $retval > 0;
$nagiosmsg .= "<br>" unless ($nagiosmsg =~ /^$/);
$nagiosmsg .= "/etc/resolv.conf: Only $count nameservers in " .
"/etc/resolv.conf (low-limit is $mincount)";
}
}
check_etc_resolv_conf() if ( -f "/etc/resolv.conf" && -x $host );
unless ( -x $host ) {
$nagiosmsg .= "$host is missing or not executable, please fix..";
$retval = 1;
}
if ($nagiosmsg =~ /^$/) {
print "/etc/resolv.conf OK\n";
} else {
print $nagiosmsg . "\n";
}
exit $retval;
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