Ethereal-users: Re: [Ethereal-users] erroneous decoding of dynamic DNS packets in ethereal?

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Thu, 11 Nov 2004 04:22:54 -0800
Stefan Puiu wrote:


I'm using ethereal as a debugging tool and have found something which
looks like a bug in the way it decodes dynamic DNS packets. What
caught my eye is that I needed to check if some DDNS packets I was
sending were correctly formatted, and they would show up with a
mention of "malformed packet" in Ethereal, leading me to believe that
I was doing something wrong in my app. On the other hand, output for
DDNS packets is also lacking - you can't tell the opcode for
prerequisistes (YXRRSET, NXRRSET, YXDOMAIN etc.)
At least according to RFC 2136, those are response codes, not opcodes, and are set only in replies, not requests. What RFC specifies them as being present in requests? 


or updates
(ADD/DELETE), so you most likely have to guess what type the update
packet is (I think the YXRRSET preset has the class set to 'any',
while NXRRSET has the class set as 'none', but I wouldn't swear by
that).


According to RFC 2136:

   3.4.2.6 - Table Of Metavalues Used In Update Section

   CLASS    TYPE     RDATA    Meaning
   ---------------------------------------------------------
   ANY      ANY      empty    Delete all RRsets from a name
   ANY      rrset    empty    Delete an RRset
   NONE     rrset    rr       Delete an RR from an RRset
   zone     rrset    rr       Add to an RRset