DDNS and Hidden Master == Brain-Damaged

John Hascall john at iastate.edu
Wed Jan 26 20:03:23 UTC 2005

> John Hascall <john at iastate.edu> writes:
> > > because that's what RFC 2136 says to do.
> > yes, but you wrote RFC2136, so that doesn't answer *why*.

> i'm sure that's in the archives somewhere.  (while i was the main author
> and editor of this document, it was a community effort and many voices
> were heard during its preparation.)

> > What is GAINED by looking through the NS records to see if the SOA.MNAME
> > is listed there?  At best it seems to catch the case where some doofus
> > puts nonsense in for the MNAME and the resolver just happens to luckily
> > choose the real master from among the NS records.  And, of course, this
> > means only intermittent success if there are more than 3 NS addresses.

> i believe the original proposal was to always use the MNAME as the target
> of update transactions, but a number of voices spoke against that on the
> basis that MNAME was usually trash and that there had never been any kind
> of protocol requirement that it not be trash and attempting to redefine
> it as non-trash would break a number of dns-management applications.  so
> we said "very well, let's do update forwarding amongst published servers,
> since published servers already have to know who the master server is",
> but then a number of people said "but that's silly, if the MNAME isn't
> trash, we should use it."  the definition of "MNAME isn't trash" turned
> out to be "MNAME matches one of the NSDNAMEs".

So it was as I feared.  The awesome design by committee approach
results in a perfectly sane and useful technique (hidden master)
losing while supporting brain-damage (oh, our fabulous wizz-bang
dns-management application didn't know what that field was about
so we put crap in it, please wipe our butts for us).  Swell.

> > > res_findzonecut() is only called if your nsupdate doesn't specify a
> > > server.  therefore if you have specific knowledge of what server ought
> > > to be receiving the update, you should share that knowledge and avoid
> > > res_findzonecut() all together.

> > And how do I make ISC DHCP do that?
> use a non-trash MNAME in the dns view seen by your dhcp server and clients.

It is "non-trash" by any sane definition.

Thanks for your prompt, if depressing, answers.


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