Re: manufacturer information for address-info.nse

[David Fifield <david () bamsoftware com>]

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.

David Fifield
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