Beware: change in configuration file semantics

[David W. Hankins]

On Wed, Feb 13, 2008 at 12:42:14PM +0000, Niall O'Reilly wrote:
> 	Prior to ISC DHCP v3.1.0, it was possible to declare an option (for  
> example):
> 
>     option tftp-server-address code 150 = ip-address;
> 
> 	and subsequently to refer to that option as follows.
> 
>     host ... {
>         ...
>         option tftp-server-address server.example.net;
>     }

so far as i am aware, this is true of all present and future releases
of ISC DHCP.

>     /etc/dhcpd.conf line 53275: unknown option dhcp.tftp-server-address
>                 option tftp-server-address server.

i am unable to replicate this (using dhcpd -t) with any of the
versions 4.1.0a1, 4.0.1b1-HEAD, 4.0.0, 3.1.1b1-HEAD, or 3.1.0, some of
which have yet to be released.  none complain.

> 	Was this change intended?
> 	If so, is it documented somewhere?
> 	Is the work-around I suggest likely to be safe?

i have a suspicion that you have found a typo in one of your config
files, or an extremely odd bug.


note that it has always been the case that an option foo declared
thus:

	option foo code bar = baz;

is implicitly a member of the DHCPv4 root options space - a DHCPv4
option code and format definition.  this means that the server has
always:

1) substituded dhcp.foo where 'option foo' lacks a dot.

2) installed into the 'dhcp option space' the option declaration for
   any 'foo' which lacks a dot.

so this is not new in any sense of the word between any current and
previous software version - the server has always assumed dhcp. when
it has been omitted, and the statements 'option tftp-server address'
and 'option dhcp.tftp-server-address' are completely equivalent.  i
don't know if the author intended this to save typing or to sound less
redundant (dhcp.dhcp-...) or what.

-- 
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
-- 
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