functions_net_dns2.php

<?php
/********************************* NET_DNS2 RELATED QUERIES IN FUNCTION FORM ****************************************/

require_once 'NET/DNS2.php';

/* Return DNS suffix with dot */
function suffix_dot($suffix)
{
    //Make sure hostname is not empty
    if($suffix != "")
    {
        $correct_suffixes="";
        //Explode DNS suffixes
        $suffix_array = explode(',', $suffix);

        // Loop thru array to make sure every suffix has a leading DOT
        foreach ($suffix_array as $ss)
        {
            //Trim whitespace before suffix
            $ss=ltrim($ss);
            //Check if suffix has leading DOT
            $suffix_dot = substr_compare($ss, ".", 0, 1);
            //Add DOT when necessary
            if ($suffix_dot != 0 )
            {
                $correct_suffixes .= ".".$ss.",";
            }
            else
            {
                $correct_suffixes .= $ss.",";
            }
        }
        //Trim whitespaces and unnecessary comma at the end
        $correct_suffixes=rtrim($correct_suffixes, ",");
        $correct_suffixes=trim($correct_suffixes);

        return $correct_suffixes;
    }
}

/* Return DNS server list without unnecessary spaces and commas */
function format_dns_server_list($dns_servers)
{
    //Make sure dns server list is not empty
    if($dns_servers != "")
    {
        $correct_dns_servers="";
        //Explode DNS servers
        $dns_servers_array = explode(',', $dns_servers);

        // Loop thru array to make sure every suffix has a leading DOT
        foreach ($dns_servers_array as $dss)
        {
            //Trim whitespace before suffix
            $dss=ltrim($dss);
            //Add to list of correctly formatted dns servers
            $correct_dns_servers .= $dss.",";
        }
        //Trim whitespaces and unnecessary comma at the end
        $correct_dns_servers=rtrim($correct_dns_servers, ",");
        $correct_dns_servers=trim($correct_dns_servers);

        return $correct_dns_servers;
    }
}

/* Return IPv4 addresses for hostname of item */
function getipv4fromdns($hostname)
{
    //Make sure hostname is not empty
    if($hostname != "")
    {
        //Get DNS Servers
        $dns_servers = dns_servers();

        //Get DNS suffixes
        $suffix = dns_suffix();

        //Make sure DNS server list and suffix list are not empty
        if(!empty($dns_servers))
        {
            if(!empty($suffix))
            {
                //Explode DNS suffixes
                $suffix_array = explode(',', $suffix);

                //Build array for hostnames with every suffix and without suffix
                foreach ($suffix_array as $suffix)
                {
                    $hostname_array .= $hostname.$suffix.",";
                }
            }
            $hostname_array .= $hostname;

            //Explode DNS Servers
            $dns_servers_array = explode(',', $dns_servers);

            //NET DNS2 Resolver with 1 second timeout (default = 5)
            $r = new Net_DNS2_Resolver(array('nameservers' => $dns_servers_array));
            $r->timeout = "1";

            //Loop thru array to make sure every hostname+suffix combination from the array is checked against every DNS Server until (hopefully) a valid response was received
            $success=false;
            $hostname_array = explode(',', $hostname_array);
            foreach ($hostname_array as $hostname)
            {
                //Try DNS query and catch exceptions from NET_DNS2
                $ipv4 = "";
                try {
                    $result = $r->query($hostname);
                    $success=true;
                    break;
                }
                catch (Net_DNS2_Exception $e) {
                    $ipv4[0] = "DNS Verification failed! Error: ".$e->getMessage();
                }
            }
            // Loop thru result array to get IP Addresses from result when DNS query succeded
            if($success)
            {
                foreach ($result->answer as $rr)
                {
                    if (($rr->type == 'A') && ($r->isIPv4($rr->address)))
                    {
                        $ipv4 = $rr->address.",".$ipv4;
                    }
                }

                //Trim whitespaces and commas
                $ipv4 = trim($ipv4);
                $ipv4 = rtrim($ipv4,",");

                //Sort IP Addresses
                $ipv4_array = explode(',', $ipv4);
                natsort($ipv4_array);
                $ipv4 = implode(', ', $ipv4_array);

                //Trim whitespaces and commas again
                $ipv4 = trim($ipv4);
                $ipv4 = rtrim($ipv4,",");
            }
            else
            {
                $ipv4[0] = "Error! Hostname is empty, unreadable or unresolveable!";
                //Give back an error due to hostname error
            }
        }
        else
        {
            $ipv4[0] = "Error! No DNS Servers specified under settings!";
            //Give back an error due to missing dns server setting
        }
    }
    else
    {
        $ipv4[0] = "Error! Hostname is empty, unreadable or unresolveable!";
        //Give back an error due to hostname error
    }

    return $ipv4;
}