On Sat, 24 Apr 2004, Mark wrote:
Why use expand_regex.pl at all? Instead of taking "/\d00\dhosting/", and expand it into 100 potential domain names, why not simply accept a query like:
9001hosting.com.be.surbl.orgAnd, internally, do the regex "/\d00\dhosting/" on it? (and all BigEvil regexes, for that matter). And return 127.0.0.2 on a match.
Ultimately, using expand_regex.pl, imho, is utterly self-defeating -- without stretching the imagination too much, even. If only I change the above regex to:
/\d+00\d+hosting/We're already looking at trillions of permutations!
It seems to me be.surbl.org should not do an internal database query on single domain names, but instead do a BigEvil regex (like SA does). At least, that is what I thought it would do; and how I had hoped it would have been.
Because the DNS system is designed to work with static lists of data, not regex patterns.
Theoretically you could design a DNS server front-end on a regex engine that would take fixed DNS queries and do regex matches. However the DNS zone-transfer mechanism is designed to deal with fixed data-sets, not regexes. Again you could take the standard DNS TXT record and overload them with special 'magic' tags to indicate that their data are regex patterns and then design a special DNS server front-end that would take those special zones and convert them into food for the regex engine back-end, but that would take special coding... Anyway you cut it, you've already blown out the possibility of using the standard DNS packages and moved into the custom coding land.
Another detail, is that the DNS system is heavily based upon the concept of cacheing. Currently there's no meaningful way to cache a regex, only the results of every lookup permutation. That would impose an unrealistic demand on the down-stream DNS servers (remember those trillions of permutations!), or demand a query all the way back to the authoritative servers on every lookup (IE do not permit any caching) which would be a killer for them in bandwidth and CPU load.
Another detail, you're adding to the CPU load on the "regex-ifed" DNS servers. Doing a regex match is more CPU intensive than a database lookup on a fixed data set. When you have the potential of thousands or millions of clients beating upon a handfull of DNS servers, the CPU load considerations become critical.
Might as well stick with BigEvil.cf and the rsync distribution scripts that have been developed by various people in SA land. (IE use already tried and tested means for those that want this kind of functionality).