host statement scope rules (ISC DHCP 3.0.5b1)
Sten Carlsen
sten at s-carlsen.dk
Mon Jul 31 23:09:35 UTC 2006
You just hit the point I try to make. I still have not seen anything
close to a crystal clear definition for what it means to place the host
statement in different places in the file.
IF there is an unclear point about precedence, like mentioned, I think
at least a warning to that effect is appropriate. For longer term, I
think this really needs to be sorted out so it really IS crystal clear.
Simon Hobson wrote:
> David W. Hankins wrote:
>
>
>> The subnet {} clause is implicitly also a group {} clause. So all
>> host statements within the subnet {} clause share a group that is
>> anchored at the subnet's curly braces. The same is true of the
>> shared-network {} clause, it is also implicitly a group {}.
>>
>>
>> What's left for this thread is to decide consensus about how best
>> to illustrate these two pieces of information to novice users.
>>
>> Currently, 3.1.0 as it exists on our release branch will produce
>> a single-line warning (no matter how many host records you have)
>> with the following text:
>>
>> log_error("WARNING: Host declarations are "
>> "global. They are not limited to "
>> "the scope you declared them in.");
>>
>> There aren't enough cycles between now and 3.1.0's release to
>> add an option to remove this warning, as has been requested.
>>
>> Our options for 3.1.0's schedule are to go ahead as it is, to
>> reword it, or to remove this 'feature' entirely.
>>
>> Please provide some feedback on what you'd like to see in 3.1.0.
>>
>
> Is there any real reason to need the inheritance of putting a host
> declaration within a subnet ? I guess it comes down to, will the host
> inherit anything that it wouldn't have inherited anyway by virtue of
> being 'put there' as the server allocates it to a subnet for lease
> allocation purposes ?
>
> I believe the answer is no to both of these (unless someone knows
> differently), and if that is the case then I suggest keeping the
> warning as-is. Perhaps it might be worth a couple of lines in the man
> page along the lines of :
>
> "Whilst host statements may be placed within a subnet or
> shared-network declaration, this was not an intentional capability
> and its use is deprecated."
>
>
> Also, if the host inherits something from one subnet (by the host
> declaration being within it), and a different value for the same
> option when the server puts a client in a different subnet, which
> takes precedence ? It strikes me that having a host that can be given
> options relevant for a different subnet is a tad dangerous - I wonder
> if it's been responsible for some of the "the client got the wrong
> value" queries on the list ?
>
> Simon
>
>
--
Best regards
Sten Carlsen
No improvements come from shouting:
"MALE BOVINE MANURE!!!"
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