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Re: Zenmap Crashing and CPU Utilisation hangs at 50%
From: David Fifield <david () bamsoftware com>
Date: Mon, 17 Jan 2011 12:31:13 -0800

On Mon, Jan 17, 2011 at 02:11:11PM +0000, Ray Middleton wrote:
Hi David,

Thanks for the response.

No the problem does not happen when switching to the topology tab, I never
get that far with the scans.  It is just on the main results window.

I've included the output.xml file and also an screenshot so you can see what
is happening from a graphical standpoint as well as the xml.

I forgot to add in my initial email that this is on Windows 7 pro 64bit.
Once manually closing out the application after it becomes unresponsive the
windows error is "NMAP front end results viewer is not responding".

I bet I know what's going on. I see that the output (the normal text
output, not the XML) is pretty long. Zenmap's live display of Nmap
output is really inefficient: it monitors the output file for any
changes, and when it changes, it re-reads the entire file from the
beginning, doing syntax highlighting and everything. When even one new
line is appended, it starts all over again. It's O(n^2) in the size of
the output.

Clearly Zenmap should only read the new lines and remember what it has
already done instead. I'll make a TODO note about this.

I don't have a good workaround to suggest other than running the command
in a terminal. (You can copy and paste the command line from Zenmap, add
a -oX option to save the output, and then open the XML file in Zenmap
later.) Another thing you might try is changing this setting to False in

enable_highlight = True

I don't know how much the highlighting contributes to the inefficiency,
but it might be enough to allow your scan to finish.

David Fifield
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