Re: ping sweep and threads

On Tue, Sep 27, 2011 at 2:11 PM, Panagiotis Atmatzidis
<[e-mail]> wrote:

> I'm looking for a quick to scan the local network (/24). I choose to use =
'net-ping' gem, since I'm working under Ruby 1.9 and 'ping' is not availabl=
e by default.
> I use the 'external' ping because it's way faster but still very slow. It=
 takes like 2 minutes to 'ping' 254 addresses with a 2 hosts 'up'. So I dec=
ided to make it a bit faster by using threads. Since I have no prior experi=
ence with Threads, I've read a couple of articles about ruby threads and he=
re is the code that I came up with:
>
> ------------------------
> require 'net/ping'
>
> network =3D '192.168.1.'
> list =3D []
> host_up =3D []
> host_down =3D []
> x =3D 1
> while x < 255
> =A0ip =3D network + x.to_s
> =A0list.push(ip)
> =A0x +=3D 1
> end
> list.each { |x|
> =A0t =3D Thread.new {
> =A0 =A0pt =3D Net::Ping::External.new(x)
> =A0 =A0if pt.ping
> =A0 =A0 =A0host_up.push(x)
> =A0 =A0else
> =A0 =A0 =A0host_down.push(x)

You need to properly synchronize since host_up and host_down are
shared between threads.  But in your case you can get rid of them
completely and just output x if pt.ping returns true.

> =A0 =A0end
> =A0}
> }
>
> puts host_up
> -------------------------
>
> First thing, do I use Threads the right way?

You should at least wait for all threads to finish (i.e. by joining).

threads =3D list.map { |x|
 Thread.new {
  # ...
 }
}

threads.each {|th| th.join}


> Second, Trying to find out whats going on from 'lsof -i', I counted 155 s=
imultaneous connections but not more. It should be 254 in theory?

Maybe some ulimit getting in the way.  Try

$ ulimit -a

You should probably also do this at the top to see errors:

Thread.abort_on_exception =3D true

> Third, do you think that is there any faster way in scanning weather a ho=
st is up or not? I understand that this is a more general question, but too=
ls like 'ettercap' scan a /24 network in less than 10 seconds on the same m=
achine same network, which makes me thing that I'm doing something wrong. I=
'm not experienced programmer, neither experienced with computer networks a=
t that level, like Alor and Naga (author's of ettercap) but then again, why=
 the difference is so big? :-/

Threads should be OK.  What Ruby version are you using?

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/