xd- with C/DNAME (was: Re: The Two Lookups Approach (was Re: Parsing the issuesand finding a middle ground -- another attempt))

[Patrik Fältström]

On 16 mar 2009, at 21.22, Erik van der Poel wrote:

> I couldn't get Ethereal on Windows to save as text, so I tried the
> "dig" command on Linux, and got the same result as Ethereal did:
>
> ;; QUESTION SECTION:
> ;www.xn--kxadbfj6eq.gr.   IN  A
>
> ;; ANSWER SECTION:
> xn--kxadbfj6eq.gr.  300 IN  DNAME xn--mxaaehw9bq.gr.
> www.xn--kxadbfj6eq.gr.  0 IN  CNAME www.xn--mxaaehw9bq.gr.
> www.xn--mxaaehw9bq.gr.  300 IN  A 67.15.125.21
>
> According to Ethereal on Windows, the above info was all in one
> packet. Is the above packet unusual? Illegal?

It is more complicated than this.

Clients that do support the EDNS0 extension of DNS is among other  
things supposed to also understand DNAME. As EDNS0 is also requirement  
for DNSSEC, DNSSEC and DNAME will always be supported both of them.  
This in turn imply that if you issue a query with EDNS0 extension,  
then the synthezised CNAME is not needed.

So, "just" issuing DNAME queries with dig is not really optimal, if  
you do not know your dig in great detail, as it would simulate an old  
dns resolver.

    Patrik

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