[30635] in North American Network Operators' Group
RE: lame delegations
daemon@ATHENA.MIT.EDU (Greg A. Woods)
Mon Aug 21 13:34:03 2000
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From: woods@weird.com (Greg A. Woods)
To: Karyn Ulriksen <kulriksen@publichost.com>
Cc: nanog@merit.edu (North America Network Operators Group Mailing List)
In-Reply-To: <0127E258EE29D3118A0F00609765B44847CB35@dhcp-gateway.sitestream.net>
Reply-To: woods@weird.com (Greg A. Woods)
Message-Id: <20000821173155.6E0FC8A@proven.weird.com>
Date: Mon, 21 Aug 2000 13:31:55 -0400 (EDT)
Errors-To: owner-nanog-outgoing@merit.edu
[ 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 <gwoods@acm.org> <robohack!woods>
Planix, Inc. <woods@planix.com>; Secrets of the Weird <woods@weird.com>
