Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!uwm.edu!bionet!arisia!roo!zany.EuroPARC.Xerox.COM!lovstran
From: Lovstrand.EuroPARC@Xerox.COM (Lennart Lovstrand)
Newsgroups: comp.mail.sendmail
Subject: Re: The algorithm for rewriting rules
Message-ID: <423@roo.UUCP>
Date: 6 Jun 90 15:53:58 GMT
References: <1990May31.152505.28721@sun.soe.clarkson.edu> <1990Jun5.173609.15672@fts1.uucp>
Sender: news@parc.xerox.com
Organization: Rank Xerox EuroPARC, Cambridge, UK.
Lines: 85

In article <1990Jun5.173609.15672@fts1.uucp> michael@fts1.uucp (Michael
Richardson) writes:
>   My experience with ruleset 3 is that an address like:
> 
>    Joe Blow <jb@foo.bar.com>
> 
>    is turned into:
>    jb<@foo.bar.com>
> 
>    In the case of the To:/From: addresses, obviously we want to 
> keep the "comment" [striping out () comments and replacing them
> is fairly easy] intact, while still rewriting the address portion.
> This is confounded by the existance of multiple addresses.

Don't worry, the comment part of each header address is extracted by
crackaddr() {in headers.c} and then tucked away in the the header structure.

Both header and envelope addresses are independently parsed by prescan()
{in parseaddr.c}, which removes comments but retains angle brackets.  This
is then rewritten by a sequence of calls to rewrite().  The headers are
finally recomposed by splicing the rewritten address back in to its comment
context.

Or in other words (pictures, diagrams, whatever):

#
#  From chapter 42 of:
#  "Sendmail and other mysteries explained in twenty minutes or less"
#
#  Section 11: How addresses /really/ are parsed.
#
#  ENVELOPE ADDRESSES
#  Called from parseaddr() with the raw envelope address as supplied on the
#  command line or given in the SMTP MAIL FROM:/RCPT TO: command.
#
   "bar.baz.org!foo"
=> prescan() =>
   "bar" "." "baz" "." "org" "!" "foo"
=> rewrite(3, 0) =>
   $# "tcp" $@ "baz" "." org" $: "foo" "@" "bar" "." "baz" "." "org"
=> buildaddr() -> rewrite(2, [mailer specific if IDA], 4) =>
   "foo" "@" "bar" "." "baz" "." "org"
=> cataddr() =>
   "foo@bar.baz.org"
#
#  HEADER ADDRESSES
#  Called from putheader() -> commaize() -> remotename() with the value of
#  header fields such as From:, To:, Resent-Reply-To:, etc.
#
  "Jan Foo <foo@bar.baz.org> (SysOp)"
=> crackaddr() =>
  "Jan Foo <$g> (SysOp)"
#
# Note the use of the $g macro
#
# And at the same time (well, almost):
#
  "Jan Foo <foo@bar.baz.org> (SysOp)"
=> prescan() =>
  "<foo@bar.baz.org>"
=> rewrite(3, 1/2 [or 5/6 if IDA], [mailer specific if IDA], 4) =>
  "foo" "@" "bar" "." "baz" "." "org"
=> cataddr() =>
  "foo@bar.baz.org"
#
# Finally, with both results above:
#
=> expand() =>
  "Jan Foo <foo@bar.baz.org> (SysOp)"
#
# And we're back to what we started from, voila!
#

Of course, the addresses would change rather substantially if the source and
destination mailers were on two completely different networks, but I think
you get the gist.  Exactly what you see as the result of rewrite(3, 0) is
also up to grabs: standard UCB sendmail will enclose the immediate
destination address in angle brackets; IDA sendmail will append a dot after
the atsign and make sure that there is nothing after the domain.

--
--Lennart <Lovstrand.EuroPARC@Xerox.COM>		R   _A _  N_   K
Rank Xerox EuroPARC, 61 Regent St			\/ |_ |_) | | \/
Cambridge, CB2 1AB, United Kingdom			/\ |_ | \ |_| /\
QOTW: "Missing keyboard; hit F1 to continue."   	E u r o  P A R C