[squid-users] Squid regex grammar

[Alex Rousskov]

On 10/27/2017 09:43 AM, Yuri wrote:

> So, in each separate case we're should make testcase for EACH regex in
> acl to make sure it will or not will work.
> 
> Generally speaking, with thousands of regular expressions and thousands
> of sites - it sounds pretty dumb, right? Many to many relasions,
> thousands tests etc.

What an admin has to do is onerous, but not as bad as you make it sound:

* A handful of test cases is sufficient to validate whether Squid
instance X supports all extended regular expressions used by its ACLs.
In fact, Squid can be easily modified to run such test cases on startup!

* If you want to test that each of the 10K ACLs matches what you want it
to match, then you have to write a lot more test cases, of course, but
such deployment-specific functionality testing is a completely different
topic out of this thread scope.


> What could be simpler is to clearly document the following: "Never use
> anything other than POSIX Basic in regular expressions because we do not
> guarantee and can not guarantee it will work"?

You are right: Adding the above text to squid.cond.documented is fairly
simple. If Squid actually supports extended regular expressions in some
environments, then such a text will also be a bit misleading/misguiding.
Wiki updates or pull requests improving Squid documentation are always
welcomed!

Personally, I cannot volunteer to add this documentation because I do
not know whether Squid can support extended regular expressions in some
environments, and I do not want to spend time adding potentially
misleading/misguiding documentation.

Long-term, we should introduce a configuration option that specifies the
exact regex flavor an admin wants _and_ forces Squid to quit if that
exact flavor is not supported by the running Squid instance.

Alex.