Re: [Exim] dnslists modification

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Author: Philip Hazel
Date:  
To: Wakko Warner
CC: exim-users
Old-Topics: Re: [Exim] dnslists modification (2nd time)
Subject: Re: [Exim] dnslists modification
On Thu, 29 May 2003, Wakko Warner wrote:

> I thought about this, but the list checking isn't in the same manner that
> exim normally checks lists for which is why I did it this way. Normal exim
> lists also accept *, which this does not.
>
> I spoke to Philip in private email and I belive he prefered != (I originally
> had =! since it was just a tad easier to code for). He also agrees with me
> that this isn't a list in the normal exim sense as well.


Yes indeed. I feel that if people see

dnslists = a.b.c = ! 127.0.0.1, 127.0.0.2

they will interpret that as being like all the other Exim lists. That is
why I suggested using != instead. Of course, the above example is
nonsense if interpreted as a "normal" Exim list because the address
127.0.0.2 matches the first item - so it can never match the second.

Negation in normal lists is useful only when the item that follow are
wildcarded in some way so that the negated item is an exception to the
wildcarding.

Somebody did mention the possibility of wildcarding, didn't they?
Specifically, along the lines of

dnelists = a.b.c = 127.0.0.0/29

I'm not entirely sure that CIDR addressing would turn out to be all that
useful here.

Current conclusion: If I implement the current != code, it provides a
useful facility that people want. Furthermore, it does not lock out an
extension in the future in which the list itself is interpreted in a
more flexible way.

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book