[Mimedefang] MIMEDefang 2.48 is available

[Paul Murphy]

Chris,

> > 	* embperl.c: Detect if user opens file >descriptors
> inside his/her filter. If so, log a loud >and nasty
> warning that such code should	be >moved to
> filter_initialize.
> 
> Why is it a problem to do this outside of
> filter_initialize?

The design of MIMEDefang is such that you cannot guarantee that the slave which
started processing your message is the same as the slave which finishes the
processing, as each part of the SMTP process could be passed to a different
slave.  If you have enabled checking at all stages, there could be different
slaves for filter_relay, filter_sender, filter_recipient, one filter() per
entity, and then also a filter_end call.  As slaves are reaped when they have
processed a configured number of requests to ensure memory usage is limited,
"your" slave could terminate after the first part of the message, and a
different slave could take over.

If the file descriptor use is completely local to the procedure (i.e. you open a
file, write to it, then close it), then your use is probably safe (subject to
locking & race conditions).  If you open it in filter_sender, then attempt to
read from it in filter_recipient, then you are digging a very large hole for
yourself - in many cases, it will work, especially on lightly loaded systems,
but you will then find it failing with obscure side effects or untraceable
problems when the load rises.

Best Wishes,

Paul.
__________________________________________________
Paul Murphy
Head of Informatics
Ionix Pharmaceuticals Ltd
418 Science Park, Cambridge, CB4 0PA

Tel. 01223 433741
Fax. 01223 433788


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