I'm sorry guys but I have no idea how to submit a patch the correct way and not the time at the moment to learn. However, if there's any interest the diff below will update the DNS record for both the A and the AAAA record if a v6 address is found on the selected interface. I hope it's of use to somebody!
1670,1671c1670
< $wanipv6 = get_interface_ipv6($dnsupdate['interface']);
< if ($wanip || $wanipv6) {
---
> if ($wanip) {
1711c1710
<
---
>
1716,1727c1715,1716
<
< if ($wanip) {
< /* IPv4 specific */
< $upinst .= "update delete {$dnsupdate['host']} A\n";
< $upinst .= "update add {$dnsupdate['host']} {$dnsupdate['ttl']} A {$wanip}\n";
< }
<
< if ($wanipv6) {
< /* IPv6 specific*/
< $upinst .= "update delete {$dnsupdate['host']} AAAA\n";
< $upinst .= "update add {$dnsupdate['host']} {$dnsupdate['ttl']} AAAA {$wanipv6}\n";
< }
---
> $upinst .= "update delete {$dnsupdate['host']} A\n";
> $upinst .= "update add {$dnsupdate['host']} {$dnsupdate['ttl']} A {$wanip}\n";
1742d1730
<