Re: manufacturer information for address-info.nse

[Vasiliy Kulikov <segoon () openwall com>]

On Sat, Sep 24, 2011 at 09:21 -0700, David Fifield wrote:
> On Sat, Sep 24, 2011 at 05:00:10PM +0400, Vasiliy Kulikov wrote:
> > Hi,
> >
> > On Sat, Sep 24, 2011 at 15:34 +0300, Toni Ruottu wrote:
> > > +local function get_manuf(mac)
> > > + if not nmap.registry.mac then
> > ...
> > > +         nmap.registry.mac.prefixes = try(datafiles.parse_mac_prefixes())
> > > + end
> >
> > FWIW, while this is not a big deal for this specific usage, but there is
> > a race condition as nmap.registry is a global variable.  If two parallel
> > invocations of the script simultaneously test nmap.registry.mac they
> > both recalc and set mac.prefixes variable.  For this usage it's harmless
> > as Lua has a garbage collector and recalc doesn't do anything significant.
>
> No, that's not how parallelism works in NSE. See
> http://www.lua.org/manual/5.1/manual.html#2.11. It's not possible for
> two scripts to access this value simultaneously because only one script
> runs at a time.

Ah, so all NSE scripts are run as coroutines, which run not in parallel
unless yield is called, even if run against different target hosts?  I
didn't know that, thank you for the information!

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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