It worked for the checksum.
Only thing that i am still confused with is the part where sequence numbers are concerned. In the tcpdump o/p I still see seq as 0 over multiple packets.
Regards
On 9/27/05, Kent Johnson <[EMAIL PROTECTED]> wrote:
the taloner wrote:
> Hi list,
>
> I was just playing around with one of the examples given in Python
> cook-book. This examples show you how to send data using ICMP packets.
> http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/439224
>
> While running the script I encountered a problem which was with the
> statement
>
> icmp.set_icmp_cksum(0)
>
> The error encountered was
>
> Traceback (most recent call last):
> File "icmpdata.py", line 38, in ?
> icmp.set_icmp_chksum(0)
> AttributeError: ICMP instance has no attribute 'set_icmp_chksum'
This recipe uses a package called impacket which is available from
http://oss.coresecurity.com/projects/impacket.html
Looking at the implementation of ICMP in the latest release of ImpactPacket.py, the correct spelling of the method is 'set_icmp_cksum'
Kent
>
>
> So I did the next logical thing, commented the line in code (which
> appears twice). Script ran smoothly and I captured the traffic using
> tcpdump.
> When the script sends first 54 bytes everything is good. When I send a
> longer data string, and the script is forced to split the data over
> multiple packets I start fasing a problem with checksum.
That shouldn't be too surprising if you commented out the line that sets the checksum!
>
> 17:36:36.198543 IP (tos 0x0, ttl 255, id 16951, offset 0, flags [none],
> length: 82) 192.168.3.37 <http://192.168.3.37> > 192.168.3.36
> <http://192.168.3.36>: icmp 62: echo reply seq 0
> 0x0000: 0002 3fb9 17fe 000c 299c e8a5 0800 4500 ..?.....).....E.
> 0x0010: 0052 4237 0000 ff01 f1d9 c0a8 0325 c0a8 .RB7.........%..
> 0x0020: 0324 0000 bab9 0001 0000 6161 6161 6161 .$........aaaaaa
> 0x0030: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
> 0x0040: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
> 0x0050: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
> 17:36:37.198470 IP (tos 0x0, ttl 255, id 16952, offset 0, flags [none],
> length: 82) 192.168.3.37 <http://192.168.3.37 > > 192.168.3.36
> <http://192.168.3.36>: icmp 62: echo reply seq 0 (wrong icmp cksum bab9
> (->bab8)!)
> 0x0000: 0002 3fb9 17fe 000c 299c e8a5 0800 4500 ..?.....).....E.
> 0x0010: 0052 4238 0000 ff01 f1d8 c0a8 0325 c0a8 .RB8.........%..
> 0x0020: 0324 0000 bab9 0002 0000 6161 6161 6161 .$........aaaaaa
> 0x0030: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
> 0x0040: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
> 0x0050: 6161 6161 6161 6161 6161 6161 6161 6161 aaaaaaaaaaaaaaaa
>
> Also as you can see that seq is not increasing as ideally it should have
> been as directed by this line:
>
> seq_id = seq_id + 1
>
> Can someone give some light on these issues?
>
> Thanks
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
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> http://mail.python.org/mailman/listinfo/tutor
_______________________________________________
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http://mail.python.org/mailman/listinfo/tutor
_______________________________________________ Tutor maillist - [email protected] http://mail.python.org/mailman/listinfo/tutor
