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Re: [NSE] Draft - targets-sniffer.nse
From: David Fifield <david () bamsoftware com>
Date: Fri, 1 Apr 2011 01:20:05 -0700

On Mon, Mar 28, 2011 at 06:41:43PM +0100, Nick Nikolaou wrote:

Not exactly, at least not if timeout stands for "total execution
time". In case the timeout is set to 4sec for instance, and if the
script receives a packet after 3.90 sec, it will start a loop for
another 4 seconds. Maybe it is an intended behavior but I think that
most users will expect the script to sniff for the exact duration they
supplied. You could update the timeout at each iteration to have a
finer control of the execution time.


You are right, I meant to set the socket timeout as a constant (example 1-2
seconds) and that way depending on the frequency of packets it would always
timeout within 1 or 2 seconds. Your way makes more sense since it would
allow the script to sniff for the exact time specified and there's no reason
for all the extra receive calls.

 Cool! Unless I am missing a reason not to do so, you could even move
the last call into the prerule function

Done.

Finally, I would also suggest to use stdnse.get_script_args() instead
of reading arguments from the registry. This could be combined with
the addition of a default value for the timeout.

Good idea, thanks.

I made all the changes.
Thanks again for your help.

Hello Nick. The script is looking pretty good! I need you to make some
more changes before it is ready to add.

You need to fix the indentation! It's too hard to read and review right
now. The indentation is a mix of spaces and tabs. It looks better if I
turn on two-space tab stops, but it's still not quite right. Please
change it to use spaces throughout using whatever indentation level you
prefer. This is important because if you don't do this, someone else
will have to before the script can be added.

The script needs to print out its IP addresses, whether newtargets is
set or not. I think that running without newtargets is a more important
use case. If I run the script now, I get this after 10 seconds:
        NSE: ERROR: to add targets run with --script-args 'newtargets'
        NSE: Finished 'targets-sniffer' (thread: 0x91ca2f0).
Instead, it should print a list of targets it should add. See the use of
target.ALLOW_NEW_TARGETS in other scripts for how to check if you're
allowed to call target.add.

Don't use nmap.is_privileged; instead try to open the interface and show
an error if it fails.

Add a targets-sniffer.iface script argument to allow controlling the
interface independently from -e. It should default to -e if the script
argument is not given. For example, "targets-sniffer.iface=eth0".

David Fifield
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