Re: Lua bugfixes and a new buffering feature

[Fyodor <fyodor () insecure org>]

On Mon, Jul 02, 2007 at 09:36:05PM +0200, Stoiko Ivanov wrote:
> > I am caching the compiled PCRE regexps into the NSE registry using
> > a fairly straightfoward scheme:
>
> Great! - I'll make sure to update the docs on pcre

Hi Stoiko.  Updating docs is wonderful, particularly with all the
changes NSE has been going through.  But I'm not 100% sold on the idea
of caching compiled regular expressions in the NSE registry as a
general rule.  Before we recommend that, I'd love to see some
empirical data that it makes a material performance difference.

> > Perhaps it would be useful to look for an init function which is called
> > only once per script per nmap invocation and only right before action()
> > is called? Another solution we should consider is passing a table to the
> > action function that scripts can use for cross-invocation persistent data
>
> Actually variables defined (either as local or not) outside of functions in
> a nse-script keep their value during multiple invocations of the script. 
> So if you define an empty table right before the action function and fill
> it during the first run of the action, the data saved in it will be
> still there during the next invocation(s).

That is great to know!  Is this in the docs?  Maybe this would be a
better way to store variables such as compiled PCREs.

> > IMPORTANT NOTE FOR NSE SCRIPT WRITERS: Don't use the function
> > receive_lines() unless you plan on doing your own line parsing.
> > This function WILL RETURN MORE THAN JUST THE FIRST LINE OF DATA
> > IF MORE IS AVAILABLE.
>
> I'll take a look at it - maybe there is an easy way to replace
> receive_lines with your buffer-approach, which seems more flexible anyway.

That could be.  It might even be best to add the feature to nsock
itself.  Or maybe you'll find it more convenient/performant to add it
at another layer.

Cheers,
-F

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