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Re: Needless DNS queries

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On 07/06/2022 17:53, Greg Wooledge wrote:
> On Tue, Jun 07, 2022 at 11:22:34AM -0400, Dan Ritter wrote:
>> search		Search list for host-name lookup.  By default, the search
>>   [...]
>> 	This may be changed by listing the desired domain search
>> path following the search keyword with spaces or tabs separating the
>> names.  Resolver queries having fewer than ndots dots (default is
>> 1) in them will be attempted using each component of the search path in
>> turn until a match is found.
> I've read this paragraph a few times, and as far as I can tell, it's
> simply wrong.
>
> If you go down farther in the page and look at:
>
>                ndots:n
>                       Sets a threshold for the number of dots which must appear
>                       in a name given to res_query(3) (see resolver(3))  before
>                       an  initial absolute query will be made.  The default for
>                       n is 1, meaning that if there are any dots in a name, the
>                       name  will  be tried first as an absolute name before any
>                       search list elements are appended to it.  The  value  for
>                       this option is silently capped to 15.
>
> This one says that it simply determines whether the name will be tried
> as is *before* appending the search domain(s) to it, or whether it just
> skips straight to appending the search domains.
>
> My experience, and the OP's experience, suggests that the description in
> the ndots paragraph is correct, and the description in the search paragraph
> is not.
>
> To the best of my knowledge, there isn't any setting to *prevent* the
> appending of search domains to a name, no matter how many dots you put
> in the name.
I've wondered about that in the past. Is this maybe a bug in the 
application, then (I admit that it'll be a widespread bug if so). To my 
knowledge, DNS domains support "relative" names (e.g. "www.example.com") 
as well as "absolute" names (e.g. "www.example.com." - with the trailing 
dot). Should applications be querying for hostnames with the trailing 
dot and, if so, would that prevent the resolver from trying to append 
the search domains?

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Needless DNS queries Dieter Rohlfing <dr-erc@gmx.net> - 2022-06-07 17:10 +0200
  Re: Needless DNS queries David Wright <deblis@lionunicorn.co.uk> - 2022-06-07 17:30 +0200
  Re: Needless DNS queries Dan Ritter <dsr@randomstring.org> - 2022-06-07 17:40 +0200
    Re: Needless DNS queries Tim Woodall <debianuser@woodall.me.uk> - 2022-06-07 18:10 +0200
    Re: Needless DNS queries Greg Wooledge <greg@wooledge.org> - 2022-06-07 19:00 +0200
      Re: Needless DNS queries Darac Marjal <mailinglist@darac.org.uk> - 2022-06-07 19:40 +0200
        Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 00:10 +0200
      Re: Needless DNS queries Tim Woodall <debianuser@woodall.me.uk> - 2022-06-08 00:20 +0200
        Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 03:00 +0200
          Re: Needless DNS queries Greg Wooledge <greg@wooledge.org> - 2022-06-08 03:10 +0200
            Re: Needless DNS queries Lee <ler762@gmail.com> - 2022-06-08 07:30 +0200
  Re: Needless DNS queries Dieter Rohlfing <dr-erc@gmx.net> - 2022-06-14 15:10 +0200

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