Re: Issue: Add a new QTYPE

["D. J. Bernstein" <djb@cr.yp.to>]

> QTYPE=* is a debugging tool only.

QTYPE=* can be used to check for CNAME records. RFC 1034 prohibits
non-CNAME records at a name that has a CNAME record, so if QTYPE=*
returns any non-CNAME records then there are no CNAME records.

This is widely used in Internet mail: clients check for CNAME records
and use them to rewrite SMTP MAIL/RCPT commands. Clients that fail to do
this are in violation of RFC 1123.

(In theory, QTYPE=CNAME would also work. In practice, QTYPE=CNAME
triggers an old BIND bug---see http://cr.yp.to/im/cname.html---so
QTYPE=* is the de-facto standard solution.)

All of this is changing. We mail implementors have agreed that this SMTP
rewriting is a bad thing; meanwhile, many DNS proposals violate the RFC
1034 non-CNAME prohibition. So a three-step transition is in progress:

   (1) mail administrators will stop relying on SMTP rewriting; and then
   (2) clients will stop looking specially for CNAME records; and then
   (3) the RFC 1034 non-CNAME prohibition can be safely violated.

In the meantime, however, the statement that ``QTYPE=* is a debugging
tool only'' is simply wrong.

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago

--
to unsubscribe send a message to namedroppers-request@ops.ietf.org with
the word 'unsubscribe' in a single line as the message text body.
archive: <http://ops.ietf.org/lists/namedroppers/>