Tag Archives: netdns2

Net_DNS2 v1.4.1 – CSYNC and DNS-Based Service Discovery Support

I’ve released version 1.4.1 of the PEAR Net_DNS2 library- you can install it now through the command line PEAR installer:

pear install Net_DNS2

Or, you can also add it to your project using composer.

Version 1.4.1

  • increased the default DNSSEC payload size value to 4000 bytes per RFC 4035 section 4.1; this is still configurable.
  • fixed a bug where I was still using the DNS_MAX_UDP_SIZE default (512 bytes) for all requests, event DNSSEC, where I should have been using the dnssec_payload_size config value.
  • removed the limitation that PTR records had to look like IP addresses; you can add other things to PTR records, like service discovery objects- RFC 6763.
  • dropped support for using the Sockets library on Windows. There have been too many inconsistencies between versions of Windows; we’ll just default to use the Streams library.
  • fixed the Net_DNS2_RR_PTR class so we can pass ptrdname’s with spaces in them so that we can support DNS-Based Service Discovery (RFC 6763).
  • added support for the CSYNC resource record – see RFC 7477.

Net_DNS2 Moved to GitHub

I’ve never been a bit fan of git- I’ve got used to using SVN over the years, and never saw a compelling reason to change- until now- that Google is shutting down the Google Code service- so I’m forced to move.

Luckily I can still keep using SVN with GitHub- I can put off actually using git for the foreseeable future!

The new Net_DNS2 repository is officially moved to GitHub:

https://github.com/mikepultz/netdns2

DNS in PHP: How to Use the Net_DNS2 Library

The PEAR Net_DNS2 DNS resolver library has been around for a while now- I originally wrote it in late 2010, with the latest release just a few months ago.

Net_DNS2, much like its predecessor Net_DNS, is a native DNS resolver/updater- which means it does not use system commands and is not a language binding on top of a C library, but instead, uses UDP/TCP sockets to communicate directly with DNS servers to retrieve the requested information.

Net_DNS2 will use the name servers specified in your resolv.conf file (for *nix users), or you can specify which name severs to use directly in the config.

Simple Lookup Example

This example uses the Google public DNS servers, to look up the A records for google.com:

$r = new Net_DNS2_Resolver(array('nameservers' => array('8.8.8.8')));    

try
{
    $result = $r->query('google.com', 'A');     

    foreach($result->answer as $record)
    {
        echo $record->address, "\n";
    }

} catch(Net_DNS2_Exception $e)  
{
    echo "::query() failed: ", $e->getMessage(), "\n";    
}

The result is:

66.185.85.45
66.185.85.34
66.185.85.59
66.185.85.30
66.185.85.54
66.185.85.35
66.185.85.39
66.185.85.55
66.185.85.49
66.185.85.25
66.185.85.40
66.185.85.24
66.185.85.44
66.185.85.29
66.185.85.20
66.185.85.50

Net_DNS2 currently supports 58 different resource record types, including all the resource records required for DNSSEC, and some resource records that have only been defined a few months ago, like the OPENPGPKEY record.

Here is an example looking up the MX records (for mail delivery) for gmail.com:

$r = new Net_DNS2_Resolver(array('nameservers' => array('8.8.8.8')));
try
{
    $result = $r->query('gmail.com', 'MX');

    foreach($result->answer as $record)
    {
        printf("preference=%2d, host=%s\n", $record->preference, $record->exchange);
    }

} catch(Net_DNS2_Exception $e)
{
    echo "::query() failed: ", $e->getMessage(), "\n";
}

The result is:

preference=40, host=alt4.gmail-smtp-in.l.google.com
preference=20, host=alt2.gmail-smtp-in.l.google.com
preference= 5, host=gmail-smtp-in.l.google.com
preference=30, host=alt3.gmail-smtp-in.l.google.com
preference=10, host=alt1.gmail-smtp-in.l.google.com

Simple Update Example

Net_DNS2 can also be used to make dynamic DNS updates. This example updates the MX record for the domain “example.com”. For updates, the DNS server you want to specify is the authoritative DNS server for the domain, and not simply a resolver:

$u = new Net_DNS2_Updater('example.com', array('nameservers' => array('192.168.0.1')));

try  
{
    //    
    // create a new MX RR object to add to the example.com zone    
    //    
    $mx = Net_DNS2_RR::fromString('example.com MX 10 mail.google.com');         

    //    
    // add the record    
    //    
    $u->add($mx);    

    //    
    // add a TSIG RR to authenticate the request 
    //    
    $u->signTSIG('my-key', '9dnf93asdf39fs');    

    //    
    // execute the request    
    //    
    $u->update();    

} catch(Net_DNS2_Exception $e)  
{
        echo "::update() failed: ", $e->getMessage(), "\n";
}

Net_DNS2 supports authentication via TSIG or SIG(0) (current supports RSA keys only); this is often required for sending DNS updates (as in the example above), or for making full zone-transfer requests, like this:

$r = new Net_DNS2_Resolver(array('nameservers' => array('8.8.8.8')));

//
// sign with TSIG to authenticate the zone transfer
//
$r->signTSIG('mykey', '9dnf93asdf39fs');

try
{
    $result = $r->query('example.com', 'AXFR');

    foreach($result->answer as $record)
    {
        echo $record;
    }

} catch(Net_DNS2_Exception $e)
{
    echo "::query() failed: ", $e->getMessage(), "\n";
}

Net_DNS2 is available as a PEAR module, or via Packagist; you can also find out more on the Net_DNS2 website.