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RE: lame delegations

  • From: Greg A. Woods
  • Date: Mon Aug 21 13:36:06 2000

[ On Monday, August 21, 2000 at 09:16:53 (-0700), Karyn Ulriksen wrote: ]
> Subject: RE: lame delegations
>
> > Unless I misunderstand what you mean, my version of BIND (8.2.2p3)
> > doesn't do that.
> > 
> > 	$ host -a 2.254.92.204.in-addr.arpa 
> > 	2.254.92.204.in-addr.arpa       PTR     most.weird.com
> > 	2.254.92.204.in-addr.arpa       PTR     mail.weird.com
> 
> Interesting.  I actually haven't tried this since BIND 4.  It made sense
> that it wouldn't so I assumed it shouldn't and further assumed that in BIND
> 8 that it didn't as well.  (Sorry about that last sentence!)  Anyways, I
> think you catch up with me in your next paragraph here ...

I don't remember ever having trouble with multiple PTRs in later
versions of BIND-4 either (I do remember that 4.9.7 in particular works
OK....)  I doubt I ever tried it on 4.8.3 though.....

> So does the reverse resolve work correctly with the two PTR responses for
> most resolvers?

I found this tidbit in my archive of the bind-workers mailing list from
back in June of 1996:

	As it stands, BIND allows an IP address to have multiple PTR
	records, but gethostbyaddr() only returns the first.

and this "reply" to a proposal to "fix" this issue:

	have you looked at the 4.9.3 or 4.9.4 version of the
	res/gethnamadr.c file, paying special attention to the
	MULTI_PTRS_ARE_ALIASES preprocessor symbol and its default
	value?

That setting is of course:

	#define MULTI_PTRS_ARE_ALIASES 1        /* XXX - experimental */

And according to my CVS repository that code's been in BIND's resolver
since before 28-Sep-94, i.e. BIND-4.9.3-BETA-9 has it but it was not in
4.9.2-940221.

I.e. Yes, most existing resolvers based on the BIND code will correctly
return multiple PTRs in responses as aliases in the returned "struct
hostent".  I have no knowledge of the behaviour of any "third party"
resolvers in this scenario though.  Obviously it's not too hard for
anyone with such a resolver, and a tool such as "host" or "nslookup"
that can be linked against that resolver, to test it though....

-- 
							Greg A. Woods

+1 416 218-0098      VE3TCP      <[email protected]>      <robohack!woods>
Planix, Inc. <[email protected]>; Secrets of the Weird <[email protected]>