Re: [Exim] Exim 4 proposal and chains

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Author: Philip Hazel
Date:  
To: Paul Crowley
CC: exim-users
Subject: Re: [Exim] Exim 4 proposal and chains
On 9 Oct 2001, Paul Crowley wrote:

> I've often wished Exim supported the creation of arbitrary "chains" of
> routers, the way the "ipchains" Linux firewalls of the 2.2 era allows
> chains of firewall rules. You could add a special router that
> directed a message to a router chain. Then you could have a single
> rule at the start of your "entry chain" which checked the domain of a
> message against local_domains, and sent it off to an appropriate chain
> if so.


Exim 4 doesn't have local_domains, but I take it you mean "some list of
local domains". But what you have suggested just reimplements the
initial global/local split which I'm getting away from.

> This makes it very straightforward to replicate the behaviour
> of Exim 3 in a flexible way that adds a great deal of power to message
> handling.


It isn't hard to replicate the default configuration behaviour of Exim
3. The first router checks for local domains, and if not, does a DNS
lookup and fails if it finds nothing. The remaining routers behave like
Exim 3 directors.

> Am I making any sense? Is it too late to propose a change of this
> magnitude?


Yes. Yes.

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.