[bind10-dev] recursor cache requirements - input required

[Likun Zhang]

> I agree with Shane in that IN is by far the most common class, so storing
an
> additional two bytes per query is just pure overhead.  However, a couple
of
> points occur to me:
> 
> 1) Suppose we get a query containing a class we have not seen before?
> - Do we reject it?
> - Do we handle it but not use a cache? (Will this be possible?)
> 2) Could we have a separate cache for each class?
> - Should we create new caches "on the fly" as new classes are seen?
> - Should be able to configure the classes we support?
> (I prefer the second option - it avoids attacks whereby 64k caches are
created to
> use up resources.)

It's not good to say our recursor only support class IN, I vote for " be
able to configure the classes we support ". 

My suggestion is:
* Reject the query with the class not configured.
* Separate the cache for each class (If the class is not IN, a small cache
size should be set for it).
* Create the cache for each class if there are some hints or zones provided
for that class when recursor is started, or else, romove the class from the
class supported list.

Thanks
Likun