Re: [Exim] convert4r3, host_reject and +allow_unknown

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Autor: Philip Hazel
Datum:  
To: Jeffrey Goldberg
CC: exim-users
Betreff: Re: [Exim] convert4r3, host_reject and +allow_unknown
On Wed, 19 Jan 2000, Jeffrey Goldberg wrote:

> host_reject_recipients = "! 138.250.0.0/16 : \
>         +allow_unknown:\
>                 partial-lsearch;TABLES/hosts_reject : TABLES/nets_reject"


<snip>

> Moving the +allow_unknown to before the old net_reject_except info
> fixed the problem


I'm surprised! That should make no difference. Are you sure the DNS
didn't get fixed?

The best solution is

 host_reject_recipients = "! 138.250.0.0/16 : \
         TABLES/nets_reject : \
         +allow_unknown: \
         partial-lsearch;TABLES/hosts_reject"


Because it then does all the IP address checking first, and if it finds
its answer there, it never needs to do a host lookup at all. I have
notes in the manual to add words pointing out that it is always best to
put IP number checks first in lists if possible, before any names, to
avoid unnecessary DNS lookups.

> but it might be worth trying to add still more smarts to the convert4r3
> script, to try to get an +allow_unknown before any net specifications.


(1) Putting +allow_unknown before any IP address specifications won't
have any a effect, since it applies only to the looking up of host names
from the IP address, and Exim doesn't need to do that to check against
IP address list.

(2) 3.00 was released back in May. I can't remember much of what it was
like before any more, and I'm afraid my time is hard pressed at the
moment that I don't judge it worth putting any effort into convert4r3.
Of course, if anybody else wants to be clever....

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