[Dnsmasq-discuss] Try next forward servers after NXDOMAIN

[richardvoigt at gmail.com]

On Sun, Apr 19, 2009 at 2:29 AM, Petteri Heinonen <
petteri.j.heinonen at kolumbus.fi> wrote:

> Hello list users. I have currently experiencing a seemingly simple DNS
> related problem, but I haven't been able to find a decent solution for it.
> Here is the setup:
>
> - Our organization has the primary master DNS, which does not serve dynamic
> DNS updates however. Only static entries there.
> - In one of our departments (the one I happen to be administrator of) hosts
> would need to use dynamic DNS updates however.
> - The domain (lets call that ourdomain.com) would need to be same
> everywhere, so I cannot use for example subdomain.ourdomain.com.
>
> Now I haven't found a way to create a zone in Bind9 which would first try
> to resolve names locally, and if not found locally, would then forward the
> query to primary master DNS server. If that would be possible, I could
> configure that local Bind server to catch the DNS update requests, and keep
> local repository of those. Then, when a query for such a dynamically updated
> hostname arrives, Bind could find that locally and give a proper response.
> And, still forward queries for which the local entry is not found, to the
> primary server. But, that kind of "hybrid" master+forward zone type does not
> exist in Bind.
>
> When I found dnsmasq, I thought that it could be a help: I can define
> several forwarding servers for a single domain there. But, it seems that
> upon receiving a first NXDOMAIN from any of the forward servers, this
> NXDOMAIN is immediately replied to the client. What I would need, is that
> upon receiving a NXDOMAIN from a server, the next server in the list would
> be tried. And if the last server in the list would also give NXDOMAIN, only
> after that NXDOMAIN would be returned to client also.


This behavior should never be default, and probably should not even be
available on the default upstream server list (it would totally break any
sort of redundancy, to wait for the slowest server).  But for individual
domains maybe it isn't so bad.

Simon, would you consider an overlay-server configuration option that treats
NXDOMAIN replies in this way, for explicitly listed domains only?


>
>
> For me it seems that there is no such functionality in dnsmasq currently. I
> took a look at the source code, and it doesn't look overly complex. However,
> my C skills are not that good, so I probably cannot make this kind of change
> all by myself. That's where I'm asking help; is there anyone on the list who
> would have examined the dnsmasq source and could possibly give some advice
> what would need to be changed in order to achieve the functionality
> described above? Any help would be greatly appreciated.
>
> Regards, Petteri Heinonen
>
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