On Wednesday 06 August 2008 09:37:25 Zbigniew Szalbot wrote:
> Since I can hardly be called an admin, I looked for advice how to get a
> stack trace. I only found advice about getting TCP dump:
>
> tcpdump -i lo -n -p -w /tmp/dkim.dump port 4445

The tcpdump is good to have too, don't forget the option: -s 0

> If this would not be what you are looking for, could you kindly suggest
> how to get the stack trace or coredump? I'd really like to help supply
> the data that might help solve the problem.

Like the following message:



Date: Mon, 19 May 2008 09:14:57 -0700 (PDT)
From: "Murray S. Kucherawy" <[EMAIL PROTECTED]>
Subject: Re: [dkim-milter-discuss] can't parse From: header / restart

On Mon, 19 May 2008, Zbigniew Szalbot wrote:
> It appears there is none at the moment. How can I configure dkim-filter 
> to leave core dumps? man dkim-filter yields nothing.

You don't really configure the filter itself to do that.  Instead, you 
have to create an environment in which the kernel will do so when the 
process does something illegal.

Among other things:

- don't use "-u" or "UserID", as many modern kernels consider it a 
security risk to leave a core as a user other than the one which started 
the process; if you have to change user for the process, use "su"

- if you must use "-u" or "UserID", make use of whichever kernel options 
you need to override the above security issue; how you do this depends on 
which kernel you're using

- make sure you start the filter with a current working directory in which 
it has permissions to create a file

- ensure there are no process limits against core dumps in effect; how you 
do this depends on which shell you're using

If none of these seem to work, check your kernel logs for a crash report 
about dkim-filter.  These may not be in your mail log.

Finally, you could try running the filter in the foreground (i.e. don't 
use Background or AutoRestart) and wait for it to crash.  If an assertion 
failure occurs, at least it will tell you which line of which file 
produced the error.

Good luck...

-MSK




or:



Date: Mon, 14 Jul 2008 12:06:00 -0700 (PDT)
From: "Murray S. Kucherawy" <[EMAIL PROTECTED]>
Subject: Re: [dkim-milter-discuss] dkim-filter dies periodically

On Fri, 11 Jul 2008, [EMAIL PROTECTED] wrote:
> I just upgraded on of our MXs, and now I'm having a problem where 
> dkim-filter periodically dies.  Doesn't dump core, doesn't log SEGV, 
> nothing.

SM suggested compiling with "-g" and running the filter that way, 
hopefully producing a coredump.  Remember that these days you need to 
satisfy certain system requirements to get coredumps:

- process has to have write permission to its current working directory

- process to have no coredump size limit imposed (set this with the shell)

- process must not have changed its userid (i.e. don't use "-u" on the 
command line or "UserID" in the configuration file), OR you must have 
configured your system to dump cores anyway

You can also capture the message which caused it to die by running your 
sendmail MTA with the flag "-d71.100".  When the filter crashes, any 
message(s) in progress will be quarantined and you can get them out of the 
queue manually.  If the message doesn't reveal anything sensitive, you can 
(at your discretion of course) submit it as data about the problem.

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