Synology router configuration files for adding dynv6.com DDNS provider.

ddns_provider.conf

# add following lines to /etc.defaults/ddns_provider.conf
[dynv6.com]
        modulepath=/usr/syno/bin/ddns/dynv6.php
        queryurl=http://dynv6.com

dynv6.php

#!/usr/bin/php -d open_basedir=/usr/syno/bin/ddns
<?php

$script = (string)$argv[0];
$ret = 'badagent';

if($argc !== 5)
{
  echo $ret;
  syslog(LOG_CRIT, $script.':'.__LINE__.' '.$ret);
  exit();
}

$token = (string)$argv[1];
$hostname = (string)$argv[3];
$ip = (string)$argv[4];

// check the hostname contains '.'
if(strpos($hostname, '.') === false)
{
  echo $ret;
  syslog(LOG_CRIT, $script.':'.__LINE__.' '.$ret);
  exit();
}

// only for IPv4 format
if(!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4))
{
  echo $ret;
  syslog(LOG_CRIT, $script.':'.__LINE__.' '.$ret);
  exit();
}

$url = 'https://dynv6.com/api/update?hostname='.$hostname.'&ipv4='.$ip.'&token='.$token;
// syslog(LOG_CRIT, $script.':'.__LINE__.' REQUEST '.$url);

$req = curl_init();
curl_setopt($req, CURLOPT_URL, $url);
curl_setopt($req, CURLOPT_RETURNTRANSFER, TRUE);
$res = curl_exec($req);
curl_close($req);
// syslog(LOG_CRIT, $script.':'.__LINE__.' RESPONSE '.$res);
switch(trim($res))
{
  case 'addresses updated':
    $ret = 'good';
    break;
  case "addresses unchanged":
    $ret = 'nochg';
    break;
  case 'hostname not found':
    $ret = 'nohost';
    break;
  default:
    $ret = trim($res);
}
echo $ret;
syslog(LOG_CRIT, $script.':'.__LINE__.' '.$ret);

Thanks for this script, but this only updates the IPv4 address, right? I search for a solution that updates the IPv6 address in case my provider changes the prefix (which happens every few weeks).

As I switched to pfSense and RFC 2136 dynamic DNS updates, I don't use that script anymore.

But you might want to try if(!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) in line 27 and $url = 'https://dynv6.com/api/update?hostname='.$hostname.'&ipv6='.$ip.'&token='.$token; in line 34.

You can find the dynv6 update API at https://dynv6.com/docs/apis#update in case you need further modifications of the update URL.

Thanks for the quick reply! Unfortunately, it does not work as the configuration always seems to choose the IPv4 address:

So in this case, it tries to send the 185.68.78.255 (which is probably my unusable DSLite IPv4 address).

So the problem is that the Synolgoy WebUI provides the IPv4 instead of the IPv6 address. Either you can somehow change that in the UI or you get the IPv6 address in the php script similar to the approach here.

Thanks, that could work - the only problem is that I have two IPv6 addresses listed when executing ip addr - one that is labeled as deprecated but is actually the one with the recently provider-updated prefix (which works when directly accessing it), and the other one that is considered active but has actually the old prefix before the new assignment (which no longer works). But I guess that is a different problem...

Yes, seems to be an IPv6 specific assignment topic. As I'm still on IPv4, can't be of any assistance here, sorry.

No worries, your suggestions already helped me a lot, thank you for that!