Re: printtableSize() causing huge spike in memory usage at end of hostgroup

[David Fifield <david () bamsoftware com>]

On Tue, Mar 17, 2009 at 02:52:37AM +0000, Brandon Enright wrote:
> I've noticed for a while now that during the end of a hostgroup there
> is a huge spike in Nmap's memory usage.  Generally this isn't an issue
> but I have a box that is very pressed for memory and occasionally Nmap
> runs it out right at the end of a huge scan.  Also, it seems that in
> certain cases, NSE output can cause Nmap to waste a ton of memory right
> and the end of the hostgroup.
>
> In troubleshooting the bug Patrick pointed out with
> printtableSize()/printableTable() the issue is obvious.
>
> Nmap calculates the worst-case-scenario of memory usage.
>
> At the cost of a little bit more CPU time, printableTable() can be
> changed to dynamically realloc() memory as needed.  This would
> eliminate the printtableSize() routine altogether.
>
> I'm willing to submit a patch for this but I'd like to hear from
> David/Fyodor/others before I do.

It sounds like the right solution to me. It is reminiscent of
xml_convert, which used to allocate a worst-case six bytes per input
byte, even though the most bytes only take up one bytes of output.

If C++ STL routines make this jobs easier, then use them by all means.
We don't have to be compatible with C in the Nmap codebase.

David Fifield

_______________________________________________
Sent through the nmap-dev mailing list
http://cgi.insecure.org/mailman/listinfo/nmap-dev
Archived at http://SecLists.Org