[Dnsmasq-discuss] DNAME or domain to domain transltion?

[Simon Kelley]

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You're right that there's no ability to do this in dnsmasq. The
synth-domain stuff is not really applicable, since it generates
records locally, rather than using data from an upstream server.

Your description implies that you want to modify the DNS as seen by
clients of dnsmasq - ie that it does a transformation of the data
being returned by the authoritative servers for a domain. That's not
what DNAME does, from a quick reading if the relevant RFC, DNAME
processing is not transparent to the stub resolver.

Implementing the sort of translation you want in dnsmasq would be more
difficult than you might expect. The normal process is that dnsmasq
forwards a DNS query, and then only retains a very small, fixed size
data structure whilst it awaits the reply. It doesn't, for instance
keep the original query. That makes applying the transformation to the
reply impossible. Keeping more information can be done (it's done for
DNSSEC processing, for instance) but you start to lose the attributes
of small, and fixed, memory usage, which makes dnsmasq attractive in
its niche.

TL;DR. What you're asking for isn't DNAME. It could be done, but not
simply and there would be tradeoffs. It's not clear if it would be
generally useful enough to make people want to pay the costs.

Cheers,

Simon.






On 17/03/15 01:33, Adrian Lewis wrote:
> Would it be fair to assume that there is no trick to this and if
> so, is there any interest in a feature request for supporting DNAME
> records? Unfortunately I'm simply a (very grateful) freeloader with
> no programming skills whatsoever. I have no idea whether
> implementing this would be something really simple or the
> opposite.
> 
> Many thanks,
> 
> Adrian
> 
> -----Original Message----- From: Adrian Lewis
> [mailto:adrian at alsiconsulting.co.uk] Sent: 11 March 2015 19:06 To:
> 'dnsmasq-discuss at lists.thekelleys.org.uk' Subject: DNAME or domain
> to domain transltion?
> 
> Hi,
> 
> I've tried to find this out through reading and googling and I
> can't find any obvious solution so I was hoping someone might know
> a trick that would help me. I'm trying to do some sort of domain to
> domain translation so that when a query for the a record of
> host1.firstdomain.tld is received, dnsmasq does a lookup for
> host1.seconddomain.tld and returns the IP as if the client had
> asked for host1.seconddomain.tld.
> 
> For an individual host this is much the same as a CNAME record but
> I need to be able to specify the hostname dynamically so that 
> %anything%.firstdomain.tld is a CNAME for
> %anything%.seconddomain.tld. Wildcards don't help either as this is
> not a case of %anything%.firstdomain.tld being a CNAME for 
> specifichost.seconddomain.tld.
> 
>> From what I gather, this is what a DNAME record will do although
>> support
> for this type of record seems a little scarce and dnsmasq doesn't
> support these directly. The purpose is not nefarious and it is all
> being done for internal to internal translation. I've not gone into
> why I need this in any great detail but it's nothing dodgy.
> 
> The --synth-domain feature suggests that there is some sort of
> engine to create dynamic replies based on the query but I need the
> equivalent of: --synth-domain=firstdomain.tld,seconddomain.tld
> 
> Can anyone help?
> 
> TIA,
> 
> Adrian
> 
> _______________________________________________ Dnsmasq-discuss
> mailing list Dnsmasq-discuss at lists.thekelleys.org.uk 
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 
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