Re: Grammar Requires Backtracking

On 17/Apr/10 21:50, William Ahern wrote:
> Is anyone else bothered by the fact that the grammar requires backtracking?
> Specifically, because a domain-spec can include forward slashes, and because
> some of the terms allow cidr masks after a domain-spec, you have to support
> backtracking.
>
> Frankly I'm not sure I want to bother supporting this. I use Ragel to parse
> the policies, which is a pure regular langage parser generator. I could use
> Ragel's scanner feature, or just hack the support, but as a general rule I
> don't like backtracking grammars for untrusted input.
>
> Perhaps it would have been wise to have included a %-encoded forward-slash,
> as was done for spaces.
>
> Anybody open to such an amendment?

A rewriting of the spec has been due since a couple of years ago. 
Until we start that, we can presumably use 
http://www.openspf.org/Community/SPFv3 to annotate various issues 
(even if we won't eventually bump the version number.)

I've added a skeletal page in 
http://www.openspf.org/Community/SPFv3-Grammar . Please feel free to 
amend/complete it as appropriate.

> I gratuitously wrote an RFC 1035 master file parser and composer in C (w/
> Ragel), and am of course parsing the YAML tests from C (w/ libyaml). So if
> anybody was waiting for the ability to generate zone files from the test
> suite, it's all but done--rfc4408-tests.c in my regress/ directory already
> spits out the zones files, the code would just need to be tweaked to output
> them in a more useful manner than as part of the debug output for failed
> tests.

How would that work for running the test suite, given that you need 
different zones --with conflicting names-- for different tests?