1#!/usr/local/bin/python2.7
2# end of new fragment overlaps old one
3
4#     |>>>>>----|
5# |--------|
6
7# If the tail of the current framgent overlaps the beginning of an
8# older fragment, cut the older fragment.
9#                         m_adj(after->fe_m, aftercut);
10# The older data becomes more suspect, and we essentially cause it
11# to be dropped in the end, meaning it will come again.
12
13import os
14from addr import *
15from scapy.all import *
16
17dstaddr=sys.argv[1]
18pid=os.getpid()
19payload="ABCDEFGHIJKLOMNO"
20dummy="01234567"
21packet=IP(src=SRC_OUT, dst=dstaddr)/ICMP(id=pid)/payload
22frag0=str(packet)[20:36]
23frag1=dummy+str(packet)[36:44]
24pkt0=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=pid, frag=0, flags='MF')/frag0
25pkt1=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=pid, frag=1)/frag1
26eth=[]
27eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt1)
28eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt0)
29
30if os.fork() == 0:
31	time.sleep(1)
32	sendp(eth, iface=SRC_IF)
33	os._exit(0)
34
35ans=sniff(iface=SRC_IF, timeout=3, filter=
36    "ip and src "+dstaddr+" and dst "+SRC_OUT+" and icmp")
37a=ans[0]
38if a and a.type == ETH_P_IP and \
39    a.payload.proto == 1 and \
40    a.payload.frag == 0 and a.payload.flags == 0 and \
41    icmptypes[a.payload.payload.type] == 'echo-reply':
42	id=a.payload.payload.id
43	print "id=%#x" % (id)
44	if id != pid:
45		print "WRONG ECHO REPLY ID"
46		exit(2)
47	load=a.payload.payload.payload.load
48	print "payload=%s" % (load)
49	if load == payload:
50		exit(0)
51	print "PAYLOAD!=%s" % (payload)
52	exit(1)
53print "NO ECHO REPLY"
54exit(2)
55