At 09:32 AM 8/6/98 +0100, Philip Hazel wrote:
> Simply removing the caching of the forward lookup is of
>course easy, but will change Exim's behaviour slightly because it will
>then do reverse lookups on the IP address of incoming mail, instead of
>forward lookups on the list of hosts it is trying to match.
if there were an option to turn off the forward lookup cache, that'd
probably be sufficent to make me happy.
> Obviously I
>could re-jig the code to do forward lookups at the time it is doing the
>checking, but I am a bit hesitant because there may be a lot of them.
it seems to me that if we are doing these particular forward lookups
repeatedly, but always on the same addresses, they'll come out of the DNS
cache -- so there isn't really a problem here. we're just taking the
caching out of exim, and moving to a system that already exists and is
dedicated to doing exactly this for us.
so:
1) remove the caching from exim
2) fix it so that it does the 6 forward lookup trick upon failure of
reverse lookup
3) add a passage to the manual recommending that anyone running a heavily
loaded mail host install a copy of ISC Bind Version 8.1.2 as a caching
nameserver, either on the same host or on a host which is nearby with a
fast connection between the two.
(for those who haven't fooled with it yet, bind 8.x.x is a major rewrite of
the old bind 4.x.x series, cleaning up a lot of issues and eliminating a
lot of unnecessary forks. upgrading to 8.1.2 is _highly_ recommended. see
http://www.isc.org/)
richard
--
Richard Welty
NeWorks Networking, Inc. 518-244-9675
rwelty@??? http://www.neworks.net/
--
*** Exim information can be found at
http://www.exim.org/ ***
