1#!/usr/local/bin/python3
2# new fragment completely overlaps old one
3
4# |----|
5#          |XXXX|
6#      |------------|
7
8# If an existing fragment is completely overlapped by the current
9# one, drop the older fragment.
10#                 TAILQ_REMOVE(&frag->fr_queue, after, fr_next);
11# Smaller older fragments might not have been nearer, and might be
12# trying to overwrite a very small part of the full packet.
13
14import os
15import threading
16from addr import *
17from scapy.all import *
18
19class Sniff1(threading.Thread):
20	filter = None
21	captured = None
22	packet = None
23	def run(self):
24		self.captured = sniff(iface=SRC_IF, filter=self.filter,
25		    count=1, timeout=3)
26		if self.captured:
27			self.packet = self.captured[0]
28
29dstaddr=sys.argv[1]
30pid=os.getpid()
31eid=pid & 0xffff
32payload=b"ABCDEFGHIJKLOMNOQRSTUVWX"
33dummy=b"01234567"
34packet=IP(src=SRC_OUT, dst=dstaddr)/ICMP(type='echo-request', id=eid)/payload
35fid=pid & 0xffff
36frag0=bytes(packet)[20:28]
37frag1=dummy
38frag2=bytes(packet)[28:52]
39pkt0=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=0, flags='MF')/frag0
40pkt1=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=2, flags='MF')/frag1
41pkt2=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=1)/frag2
42eth=[]
43eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt0)
44eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt1)
45eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt2)
46
47sniffer = Sniff1();
48sniffer.filter = "ip and src %s and dst %s and icmp" % (dstaddr, SRC_OUT)
49sniffer.start()
50time.sleep(1)
51sendp(eth, iface=SRC_IF)
52sniffer.join(timeout=5)
53a = sniffer.packet
54
55if a and a.type == ETH_P_IP and \
56    a.payload.proto == 1 and \
57    a.payload.frag == 0 and a.payload.flags == 0 and \
58    icmptypes[a.payload.payload.type] == 'echo-reply':
59	id=a.payload.payload.id
60	print("id=%#x" % (id))
61	if id != eid:
62		print("WRONG ECHO REPLY ID")
63		exit(2)
64	load=a.payload.payload.payload.load
65	print("payload=%s" % (load))
66	if load == payload:
67		exit(0)
68	print("PAYLOAD!=%s" % (payload))
69	exit(1)
70print("NO ECHO REPLY")
71exit(2)
72