Path: utzoo!dciem!nrcaer!cognos!dgbt!andrew
From: andrew@dgbt.uucp (Andrew Patrick)
Newsgroups: can.uucp
Subject: Re: .ca domain weirdness with pathalias and smail
Message-ID: <977@dgbt.uucp>
Date: 16 Dec 88 16:10:04 GMT
Article-I.D.: dgbt.977
References: <314@ontenv.UUCP>
Reply-To: andrew@dgbt.UUCP (Andrew Patrick)
Followup-To: can.uucp
Distribution: can
Organization: The Communications Research Centre Ottawa, CANADA
Lines: 58
Summary: problems not as bad as you suggest.

In article <314@ontenv.UUCP> soley@ontenv.UUCP (Norman S. Soley) writes:
...
>Th[a]t is unless you are using smail 2.5. Seems the resolution algorithm
>is a little botched so that user@subdomain.ca will always resolve to 
>hop1!hop2!hop3!user because it matches the .subdomain.ca line in the
>path file first. Presto! all mail to any .ca site fails. 
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The situation is not quite as bad as you suggest.  Let's look at a
concrete example.  Suppose you wanted to get mail to
'user@vaxr.uwo.ca' (one of the internal machines at the University of
Western Ontario).  The site 'julian' is the authority for the
'.uwo.ca' domain.  From here, the pathalias outputs look like this:

|.uwo.ca	bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!%s
|uwo.ca	bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!uwo.ca!%s

Now looking at the way Smail 2.5 parses the addresses
'user@vaxr.uwo.ca':

|resolve: parse address 'user@vaxr.uwo.ca' = 'user' @ 'vaxr.uwo.ca' (DOMAIN)
|getpath: looking for '.vaxr.uwo.ca'
|getpath: looking for 'vaxr.uwo.ca'
|getpath: looking for '.uwo.ca'
|route:  'vaxr.uwo.ca' (uwo.ca) = 'bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!%s' (199)
|resolve: parse route 'bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!vaxr.uwo.ca!user' = 'bnr-vpa!utgpu!ai.toronto.edu!julian!vaxr.uwo.ca!user' @ 'bnr-rsc' (UUCP)
|resolve 'user@vaxr.uwo.ca' = 'bnr-vpa!utgpu!ai.toronto.edu!julian!vaxr.uwo.ca!user' @ 'bnr-rsc' (UUCP)
|bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!vaxr.uwo.ca!user

Thus, Smail will route the mail to 'vaxr.uwo.ca' correctly.  Thus, all
mail to any .ca site does NOT fail.

The weirdness comes in when Smail parses the address 'user@uwo.ca':

|resolve: parse address 'user@uwo.ca' = 'user' @ 'uwo.ca' (DOMAIN)
|getpath: looking for '.uwo.ca'
|route:  'uwo.ca' (uwo.ca) = 'bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!%s' (199)
|resolve: parse route 'bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!user' = 'bnr-vpa!utgpu!ai.toronto.edu!julian!user' @ 'bnr-rsc' (UUCP)
|resolve 'user@uwo.ca' = 'bnr-vpa!utgpu!ai.toronto.edu!julian!user' @ 'bnr-rsc' (UUCP)
|bnr-rsc!bnr-vpa!utgpu!ai.toronto.edu!julian!user

Instead of sending mail to 'julian!uwo.ca!user' as the pathalias
output would suggest, Smail sends it to 'julian!user'.  Unless julian
= uwo.ca (and this is not declared in the maps), this routing will
cause a problem.

Thus, Smail will get mail to a machine within a .ca domain, but it may
not get mail to the domain gateway.

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Andrew Patrick, Ph.D.         Communications Research Centre
  (613) 990-4675              Dept. of Communications, Canada

andrew@crcmar.UUCP            ...utzoo!bnr-vpa!bnr-rsc!crcmar!andrew
BITNET: andrew@doccrc         INTERNET: andrew@dgbt.crc.dnd.ca 
N.B. We are changing from crcmar.UUCP to dgbt.UUCP, but the maps have
yet to be updated.
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