[Twisted-Python] Handeling unresolved DNS queries?

Jesper Taxbøl jesper at taxboel.dk
Thu Oct 22 10:46:31 EDT 2009

Hi Jean-Paul,

Thanx for your nice reply. My problem seems to be that I dont get any calls
to writemessage when the domain is a bogus one?


2009/10/22 <exarkun at twistedmatrix.com>

> On 20 Oct, 07:50 pm, jesper at taxboel.dk wrote:
> >Hi Guys,
> >
> >Im playing with a dns-cache script, that overrides DNS requests for
> >certain
> >IP addresses.
> >
> >I would like to add functionality, so unresolved requests are sent to a
> >spicific IP. How do I go about doing that?
> >
> >Is there a negative answer in the (udp) DNS protocol or am I forced to
> >use a
> >timeout.
> You've overridden writeMessage to inspect messages for answers and
> rewrite them if necessary.  You can recognize error responses by looking
> at the rCode attribute of the message object itself.  This will take on
> a value like dns.OK, dns.EFORMAT, dns.ESERVER, dns.ENAME, dns.ENOTIMP,
> or dns.EREFUSED.  You can handle these errors by making a request of
> another domain, although since writeMessage is a very low-level API in
> the process and not really intended to be overridden, I'm not sure how
> you'll insert the responses you get from these new requests into the
> original request/response process.
> Jean-Paul
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