Jürgen Dietl juergen.dietl at
Wed Mar 9 08:21:19 UTC 2011


maybe I misunderstood what you want. But if you dont want to solve your
script but just wand to see the results - there is a good program for this
already (but be careful with the settings !!!):


2011/3/9 Alex Bligh <alex at>

> --On 8 March 2011 22:43:20 -0500 Homer Wilson Smith <homer at>
> wrote:
>  The problem is that some student routers only respond to DISCOVER
>> requests with as the from IP.  The perl script below sends
>> the packet with the IP of the sending linux server, and is thus
>> ignored by some student routers, making it harder to track them down.
>>    Is there an easy change to the script below to fix this problem?
> I suspect you will need to use something like Net::RawIP. I think
> IO::Socket::INET always uses the OS to assemble the UDP packets,
> in which case you will never get a source address.
> In C, I use libpcap for this sort of thing as it has a little known
> feature (pcap_sendpacket) where it can send raw packets, as well as
> doing tcpdump packet filtering on receipt. Net::pcap supports
> this with the sendpacket method (I haven't tested it). You
> may find this is the easiest way to do it, particularly as your
> next problem is going to be how to filter responses (the OS won't
> help unless you have a real socket).
> Note you'll have to construct your own IP packets etc either way.
> --
> Alex Bligh
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