Re: [Observium] dns_get_record or why PHP sucks

1 Apr 2015

      Hi,
thanks for the info.
I think this applies only to systems where IPv6 stack fully disabled.
We have many systems where IPv6 is not used and all hostnames anyway
resolved.
But I'm a little fixed the code to avoid this situation in r6357.
On 01.04.2015 20:08, Sir l33tname wrote:
...
Hey,
I guess I have found a bug. In ./includes/common.inc.php on the function
gethostbynamel6.
The problem is this one:
*query the A record:*
var_dump(dns_get_record($host, DNS_A));
array(1) {
  [0]=>
  array(5) {
    ["host"]=>
    string(14) "host.name.tdl"
    ["class"]=>
    string(2) "IN"
    ["ttl"]=>
    int(0)
    ["type"]=>
    string(1) "A"
    ["ip"]=>
    string(12) "192.168.17.2"
  }
}
*query the AAAA record:*
var_dump(dns_get_record($host, DNS_AAAA));
PHP Warning:dns_get_record():DNS Queryfailed infile.php on line 4 bool(false)
*query both together*
var_dump(dns_get_record($host, DNS_A + DNS_AAAA));
PHP Warning:dns_get_record():DNS Queryfailed infile.php on line 4 bool(false)
As you can see if the DNS server doesn't have a AAAA record it fails,
this cause for me the error that I couldn't add a new device to the
observium.
I build a prototype code which could be a solution for this problem but
since I'm not a good php programmer I'm sure there is a smarter way for
this.
$A_record = dns_get_record($host, DNS_A);
$AAAA_record = dns_get_record($host, DNS_AAAA);
if($A_record != false && $AAAA_record != false)
{
    $record = array_merge($A_record, $AAAA_record);
}
else if($A_record == false)
{
    $record = $AAAA_record;   
}
else if($AAAA_record == false)
{
    $record = $A_record;   
}
else
{
    #show some error   
}
Since I did all the research it should be fairly easy to fix this, so I
hope someone will do it. If you need anything more to fix it please ask.
A few things I noticed in the debugging process and totally unrelated to
the problem:

the name gethostbyname6 is a bit confusing since it does both I would

rename it to gethostbyname

same goes for $try_a I personally would pick a more descriptive name
"Could not resolve $host" in ./includes/functions.inc.php and

./includes/functions.inc_d.php, since It took me some time to figure out
what this means
   I would add something like "Could not resolve $host with your DNS or
your Hosts file"
But all in all it's a nice code base for a php project, well done!
For the case I'm wrong please tell me why.
l33tname

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Mike Stupalov
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