[dns-operations] forward compression pointers?

[Robert Edmonds]

are there any DNS responders that generate forward compression pointers,
or DNS initiators that reject them?

i note RFC 5625 section 6.3 which could be construed to imply that forward
pointers may be dropped, since forward pointers "might cause a parsing loop":

   Examples of malformed packets that MAY be dropped include:

   o  invalid compression pointers (i.e., those that point outside of
      the current packet or that might cause a parsing loop)

but 5625 is BCP, not standards track.  c.f.,

    http://blacka.com/david/2008/03/09/internet-draft-ideas-dns-related/

    Idea #3: DNS Name Compression Standards 

    A draft mandating the DNS name compression only be done in one
    direction. Virtually all (or perhaps even actually all)
    implementations have DNS compression pointers only pointing to
    earlier in the message. This draft would propose that
    forward-pointing compression pointers should be treated as format
    errors. This would accomplish two things:

        1. Simplify what implementers need to support when parsing
        messages, and

        2. outlaw any possibility of having to deal with a compression
        pointer loop. 

    And, in the process, effectively codify standard practice.

-- 
Robert Edmonds
edmonds at isc.org