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 > > > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
