Re: [TCLUG:4623] Re: resolver sortlist

[Sandipan Panigrahi <pani@frontiernet.net>]

Isn't the sortlist just for sorting the entries ? From what
I understand it only sorts the entries returned by a gethostbyname()
in the order of the sortlist.

If you change your sortlist to 128.101.230.0/255.255.0.0, 
you will end up with the 128.101.230.70 as the first entry in the
addresses. But you will still have the remaining addresses returned
to it. It does not specify that only the 128.101.230.70 will be 
returned. If you are only using nslookup to test to see if only
one address is returned it could be that nslookup is broke in 
one or the other OS's.  You could try testing by writing script
to do a gethostbyname() and see how many entries are returned in 
each OS and the order in which they are returned.

If I misunderstood your question than my apologies :).
--
sandipan

Mark A. Bentley wrote:
> 
> On Tue, 9 Mar 1999, Dan Mack wrote:
> > "Mark A. Bentley" wrote:
> > > Has anyone been able to get the sortlist option in /etc/resolv.conf to work
> > > as documented in resolver(5) to work with RedHat 5.2?
> > >
> > > It works fine with our Slackware 3.5 (libc5) systems, but so far I've been
> > > unable to get it to work with RedHat 5.2 (glibc2).
> > >
> >
> > This works for us on stock RedHat 5.2:
> >
> >  % uname -a
> >  Linux tigger-e194.cray.com 2.2.0 #1 SMP Tue Jan 26 16:36:48 CST 1999
> > i686 unknown
> >
> >  % cat /etc/resolv.conf
> >  search cray.com sgi.com americas.sgi.com
> >  nameserver a.b.c.d
> >  nameserver x.y.z.a
> >  nameserver l.m.n.o
> >
> >  % ping dist.engr
> >  (tigger-e194) ~ # ping dist.engr
> >  PING dist.engr.sgi.com (192.26.80.118): 56 data bytes
> >  64 bytes from 192.26.80.118: icmp_seq=0 ttl=249 time=61.1 ms
> >  64 bytes from 192.26.80.118: icmp_seq=1 ttl=249 time=58.8 ms
> >
> > so, it used the second item in the search list.  Is this what you mean?
> >
> 
> Not quite...there is actually an option "sortlist".  Here's an example
> from a machine that is on the 128.101.229.0 network:
> 
>         search cs.umn.edu umn.edu
>         nameserver 128.101.229.71
>         sortlist 128.101.229.0/255.255.255.0
> 
> We've just changed augustus and caesar (among others) so that their DNS
> entries have multiple addresses.  See:
> 
> nslookup augustus ...
> 
>      Server:  mail.cs.umn.edu
>      Address:  128.101.229.71
> 
>      Name:    mail.cs.umn.edu
>      Addresses:  128.101.229.71, 128.101.230.70, 160.94.239.171,
>                  128.101.248.7 160.94.27.171, 160.94.8.171, 160.94.148.171,
>                  160.94.149.70, 128.101.224.69 128.101.225.70,
>                  160.94.227.171, 128.101.228.69
>      Aliases:  augustus.cs.umn.edu
> 
> The sortlist option should give preferance to the particular network
> listed.  In the example above the resolver should always return the IP for
> the 229 interface to a machine doing an gethostbyname with the specified
> sortlist.
> 
> This works on SunOS, IRIX, Slackware (libc5-based), and AIX.  But I can't
> get our RedHat 5.2 machines to work.  When a RedHat 5.2 machine does a
> gethostbyname, it will return an IP in round-robin fashion, and ignore the
> sortlist.
> 
> I'm pretty sure it's a glibc2 issue...I've been looking through the source
> to glibc-2.0.6 and I did find the "sortlist" option in resolv/res_init.c so
> I know it is supported...just can't figure out why it's not working...Argh.
> 
> --Mark
> 
> ==========================================================================
> Mark A Bentley                  Email:  bentlema@cs.umn.edu
> Systems Staff, CSci Dept
> University of Minnesota         URL:    http://www.cs.umn.edu/~bentlema/
> 
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