BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT "Illegal"

[Barry Margolin]

In article <glnemv$10nf$1 at sf1.isc.org>,
 Matus UHLAR - fantomas <uhlar at fantomas.sk> wrote:

> On 27.01.09 08:46, Al Stu wrote:
> > So then you disagree that the following example returns a valid address 
> > record for srv1?
> > 
> > srv1  300 IN A 1.2.3.4
> > mx1   300 IN CNAME srv1.xyz.com.
> > @   300 IN MX 1 mx1.xyz.com.
> > 
> > 1) Select Target Host:
> > The MX query for xyz.com delivers mx1.xyz.com which is a CNAME.
> > 
> > 2) Get Target Host Address:
> > The A query for mx1.xyz.com delivers the address (A) record of 
> > srv1.xyz.com, 1.2.3.4, and also delivers the alias (CNAME) record of 
> > "mx1.xyz.com".
> 
> They are two queries. If mx1 would be an A, it would be returned in the
> first query. Since it's a CNAME, the IP is not returned in the MX query.

So what?  If the IP isn't in the additional section, the client will do 
its own A query.

There's no requirement that the response to the MX record include the A 
record.  It's nice if it does, since it saves a query, but this is just 
an optimization.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***