Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!milano.sw.mcc.com!weber.sw.mcc.com!knutson
From: knutson@weber.sw.mcc.com (Jim Knutson)
Newsgroups: comp.mail.sendmail
Subject: Sendmail host canonicalization broken?
Message-ID: <3006@weber.sw.mcc.com>
Date: 12 Apr 91 21:38:59 GMT
Organization: MCC, Austin, TX
Lines: 46

I've been trying to trace down a problem I've been having with name
canonicalization using $[ $].  I want to be able to resolve host.sub
into host.sub.top.domain or host into host.top.domain.

For example, my domain is sw.mcc.com.  I want to be to send:

user@act -> user@act.mcc.com
	and
user@bc.cad -> user@bc.cad.mcc.com

The $[$] rewrite won't do this.  This isn't so much of a problem for
mail delivery since the IPC mailer CAN resolve these host names.  The
real problem is that because you CANNOT resolve these in ruleset 0,
your mailer choice (and hence your header rewriting) will be affected.
In this case, these hosts look like external domain hosts (not part of
mcc.com) and the headers are rewritten accordingly.

The reason this is happening is because maphostname() turns off
recursive domain name matching (RES_DNSRCH) before calling
getcanonname().  The reason given for this is as follows:

        /*
        **  Don't do recursive domain searches.  An example why not:
        **  Machine cerl.cecer.army.mil has a UUCP connection to
        **  osiris.cso.uiuc.edu.  Also at UIUC is a machine called
        **  uinova.cerl.uiuc.edu that accepts mail for the its parent domain
        **  cerl.uiuc.edu.  Sending mail to cerl!user with recursion on
        **  will select cerl.uiuc.edu which maps to uinova.cerl.uiuc.edu.
        **  We leave RES_DEFNAMES on so single names in the current domain
        **  still work.
        **
        **  Paul Pomes, CSO, UIUC       17-Oct-88
        */

Now, what I really want to know is whether or not this is a valid
argument.  I think that resolving uucp names into internet names using
the domain name service is wrong.  The latest config files take steps
to avoid doing this.  Even if the uucp name is being resolved, the 
canonical uucp form of host!user is user<@host.uucp> which shouldn't
resolve as described above.  So why not turn it back on and allow mail
addresses to be resolved in a consistent manner with hostname lookups?
-- 
Jim Knutson
knutson@mcc.com
cs.utexas.edu!milano!knutson
Wk: (512) 338-3362