logging sometimes fails

[David W. Hankins]

On Wed, Aug 23, 2006 at 04:00:05PM -0400, Randy Grimshaw wrote:
> As it is sometimes useful for debugging, I have been logging the dhcp
> fingerprint of the systems on our network.
> But have noticed that some systems such as Macintosh OSX are curiously
> absent... the log() seems to be failing.
> 
> on commit {
>   log(info,
>     concat("Fingerprint:\t",
>       binary-to-ascii(16, 8, ":", substring(hardware, 1, 6)),
>       "\t",
>       binary-to-ascii(10, 8, "-", option dhcp-parameter-request-list),
>       "\t",
>       option vendor-class-identifier
>     )
>   );
> }
> 
> I woudn't post this to the list yet because such a failure could reveal
> other exposures.... but I am curious.
> have you seen anything like this elsewhere?

concat() returns a null value if any of its arguments are null (not
present, or of zero length).

I suspect the vendor-class-identifier is not present on the clients
that are not logging in your case.

Consider:

	pick-first-value(option vendor-class-identifier, "<none>")

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David W. Hankins	"If you don't do it right the first time,
Software Engineer		you'll just have to do it again."
Internet Systems Consortium, Inc.	-- Jack T. Hankins