Bug#398224: Re: This is a design flaw

[Marc Haber]

severity #398224 wishlist
user exim4 at packages.debian.org
usertags #398224 probably-not-a-bug-in-exim
thanks

On Sun, Nov 12, 2006 at 04:11:04PM +0000, Stephen Gran wrote:
> This one time, at band camp, Andreas Metzler said:
> > I have a couple of questions about this:
> > 
> > How are you going to handle the "greylistd is removed but not purged
> > case"?
> 
> you could test for the presence of the binary in your acl's, but that
> adds yet another stat() to the setup.  I'm not sure how much that
> matters, though.

I think that is the most clear approach. If it happens to frequently,
use a macro or an ACL variable.

> It's messy, but this is a general problem I have some interest in solving.
> There are many add on packages that should be able to be drop in and
> work with the MTAs in Debian, but we can't just munge other package's
> config files, so I am trying to work towards a reasonably clean solution
> to the general problem.

The idea to integrate this into Debian's exim4 packages is the
following:

- drop your config into split config, /etc/exim4/conf.d
- this will directly solve the issue for users of split config (one
  reason why I like split config so much)
- unsplit config users will need to do manual work, this is a feature
  of unsplit config.
  * manually modify /etc/exim4/exim4.conf.template to use greylistd,   _OR_
  * use update-exim4.conf.template to rebuild /etc/exim4/exim4.conf.template
    from split configuration, losing local changes to
    /etc/exim4/exim4.conf.template in the process.

To activate the ACL, I recommend using the
MAIN_ACL_CHECK_(MAIL|RCPT|DATA) macros to point exim4 to the ACLs
delivered by your package and have your ACLs call ours as sub-ACLs.
This Macro could also be the place to decide which ACL to call
depending on greylistd existing or not. The macros are string expanded
before they're used so, something along
${if exists{/usr/bin/greylistd}{acl_greylistd_check_rcpt}{acl_check_rcpt}}
(syntax most definetely wrong, but I hope that the idea comes over)
can be used.

Advantages:
  * (a1) elegant
  * (a2) using the Debian exim way
  * (a3) no work required by the exim4 maintainers *grins*

Disadvantages:
  * (d1) needs manual work for unsplit config users
  * (d2) calls for trouble if more than one package uses this trick
         (resulting in more manual work for the local admin)

Until this has been discussed to an end, I consider this a solution
for the issue at hand and will not do any changes to the exim4 packages.

Post-etch, we might want to review our ACL structure and split the
ACLs along more files to allow third-party packages to add new ACL
stanzas right in the middle of our ACL. I remember that Andreas didn't
like that idea though. It would, however, mitigate (d2).

Comments?

Greetings
Marc

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