Different forwarder for certain response ip (result ip )

/dev/rob0 rob0 at gmx.co.uk
Sat Sep 16 14:52:20 UTC 2017

On Sat, Sep 16, 2017 at 03:18:57AM -0700,
   Omid Kosari via bind-users wrote:
> This is my first post to this mailing list .

And it's a classic example of "XY question": "I want to do X, and I 
think Y will do it, so I ask how to do Y, although people more 
familiar with the subject matter think that sounds like a very 
strange thing to do."

> I have a caching bind dns server with forwarders like this .
>     forwarders {
>     };

Later in the thread we discovered that the ISP is redirecting all 
queries on port 53 to their own nameservers which are broken in 
various ways.  I *think* they are hijacking NXDOMAIN responses, 
returning their own ad server IP address for NXDOMAIN queries.  But 
you have failed (or refused) to provide this bit of information.

With redirected queries on port 53 TCP and UDP, the address of the 
forwarder would not matter.  It could be anything, as you showed 
later in the thread.

> I want to use another forwarders if the response of the query is 
> for example

And you munged the ISP's ad server, why, to protect their "privacy"?  
Sadly, this protection possibly harms you, and possibly other users 
who might otherwise be tempted to do business with that ISP.  It 
might make your quest more difficult, because if you had been open 
about who/what you are dealing with, you might have found another 
user who had come up with a different workaround for the problem.

No, this is not possible; named makes a query and cannot be 
configured to redo the query based on its results.  But you might be 
interested in the deny-answer-* features of BIND.  See the "Content 
Filtering" section of ARM chapter 6 for your BIND version.  This 
content filtering would not repeat the queries, however.

See also dnsmasq(8) for a forwarding-only nameserver which 
conditionally can ignore a certain result.  As with named, it won't 
repeat the query, however.

> I've found that rpz-ip is what i want

How so?  Be more specific about the real problem and goal.

> but i was unable to create relation to forwarders .


>        //if response ip or rpz-ip = then
>         forwarders {
> port 443;
> port 443;
>         };

So if you want to use opendns, why not just use those forwarders for 
all queries?  What benefit could there be in querying the ISP 
nameservers first?
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