Re: A sleep function for NSE

[Ron <ron () skullsecurity net>]

David Fifield wrote:
> Hi all,
>
> One of the Nmap TODO items is a sleep function for NSE. Such a function
> allows rate-limiting traffic for politeness or to avoid triggering some
> filter. The attached stdnse.sleep.diff implements such a function.
>
> Even though sleep is implemented through Lua's C API, I put in in
> stdnse, which is otherwise a pure Lua module. I originally put it in the
> nmap module just because that is already a C module and it was easy to
> implement there. But then I reflected that sleep doesn't fit the
> description of the nmap module: "an interface with Nmap's internal
> functions and data structures." Looking at the other modules I though
> that stdnse was the best fit.
>
> This trick is accomplished by loading sleep into a private stdnse.c
> module. stdnse.lua requires this module, then transfers its contents
> into its own namespace; i.e., stdnse.c.sleep becomes stdnse.sleep. What
> do you think? I think we should group functions by what they do, not by
> what language they happen to be implemented in, whenever possible. The
> person calling stdnse.sleep likely doesn't care if it's written in Lua
> or C.
>
> I attached a patch against sql-injection.nse showing how sleep can be
> made into a rate limiter. The patched script sleeps if necessary between
> page retrievals so that no more than one page per second is requested.
>
> Does someone else have a use for a sleep function? Is the design
> suitable for you?
>
> David Fifield

Hi David,

This is a great idea, and something I was looking for fairly recently. 
There are places in my code that would greatly benefit from a sleep 
function.

I just have on question -- does this implementation of Sleep proper 
yield to other Lua threads (coroutines?) while the sleep is happening, 
or is everything blocked?

Ron

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