I'm not so sure about this patch - it would mean that navigating down the named.conf parse tree and back up it wouldn't return to the same object.

In worst case it must be rewritten. I tested it fast and it doesn't break anything, but something can count on this bug to work. This circular reference must be fixed, because leaked memory is huge ( around 12MB per domain restore ). In my opinion it doesn't rely on that mistake.

EDIT: Inner key 'values' in 'parent' is still a reference.

When you say "domain restore", are you talking about Virtualmin backups and restores?

Yes

Ok, what confuses me is that this patch doesn't seem related to any code that is invoked as part of the backup or restore process - if there is a memory leak, it should happen any time DNS records are listed or edited by Virtualmin.

Ok, you can try it too. It's a problem on long running operations ( like the restore ). Ops like list/edit are living short time.

I wasn't able to re-produce this - how large is the named.conf file on your system?

1663 records, 258K
To reproduce this you must restore 2+ domains with DNS opt enabled

So you have 1663 domains hosted by Virtualmin with DNS enabled? That's .... quite a lot.

But I'm still having trouble re-producing this issue, or seeing where the memory leak could be coming from. Even though the parsed named.conf structure has a loop, this on it's own shouldn't cause a leak unless it is serialized - which doesn't happen anywhere in the backup / restore code.