Re: RE: rr.com and SPF records

Stuart D. Gathman wrote:
> On Wed, 16 Mar 2005, Radu Hociung wrote:
>
>
> > Do you know of other available optimizers ?
>
> Not any general purpose ones, like you're building.  Rigging the Python spf
> module to build an ip list while evaluating an SPF record was fairly trivial,
> however (and suited my purposes).  Preserving the policy for each part of the
> list will be a little harder.  I am thinking of making this part of the API.
> Another option would be to simplify to A and IP4 mechanisms.
It's pretty easy to come up with an ordered list of ip4 mechanisms with 
the correct prefixes. My compiler does this already also.
The challenges I have found so far are:

1. folding the long resulting record into multiple smaller records
   (<512-bytes - UDP limit)

2. compacting lists of IPs into IP blocks. This requires re-ordering
   of the ip mechanisms. The challenge is to reorder ip addresses with
   different prefixes, ie:

   * "-ip4:1.2.3.100/2 +ip4:1.2.3.0/24" cannot be compacted
   * "+ip4:1.2.3.0/24 -ip4:1.2.3.100/2" can be compacted to
     "+ip4:1.2.3.0/24"
   * "+ip4:1.2.3.0/24 +ptr -ip4:1.2.3.100/2" cannot be compacted
                
3. directives (exp=, etc). Where to put them when includes and
   redirects are involved?

Perhaps I could postpone the implementation of the more complicated
cases like 3.

In anycase, where corner-cases are not handled, the output of the
compiler must be functionally equivalent to the input, but perhaps
less efficient than it is possible. Otherwise, it's a broken compiler
that does more harm than good.

We should start a new thread on optimizations if you'd like to discuss it.

Thanks,
Radu.

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