1#!/usr/local/bin/python2.7
2
3print "fragments of a large packet that has to be refragmented by reflector"
4
5# |--------|
6#          |------------------|
7#                              ...
8#                                 |------------------|
9#                                                    |----|
10
11import os
12from addr import *
13from scapy.all import *
14
15pid=os.getpid()
16eid=pid & 0xffff
17payload=100 * "ABCDEFGHIJKLMNOP"
18packet=IPv6(src=LOCAL_ADDR6, dst=REMOTE_ADDR6)/ \
19    ICMPv6EchoRequest(id=eid, data=payload)
20request_cksum=ICMPv6Unknown(str(packet.payload)).cksum
21print "request cksum=%#x" % (request_cksum)
22frag=[]
23fid=pid & 0xffffffff
24frag.append(IPv6ExtHdrFragment(nh=58, id=fid, m=1)/str(packet)[40:56])
25offset=2
26chunk=4
27while 40+8*(offset+chunk) < len(payload):
28	frag.append(IPv6ExtHdrFragment(nh=58, id=fid, offset=offset, m=1)/
29	    str(packet)[40+(8*offset):40+8*(offset+chunk)])
30	offset+=chunk
31frag.append(IPv6ExtHdrFragment(nh=58, id=fid, offset=offset)/
32    str(packet)[40+(8*offset):])
33eth=[]
34for f in frag:
35	pkt=IPv6(src=LOCAL_ADDR6, dst=REMOTE_ADDR6)/f
36	eth.append(Ether(src=LOCAL_MAC, dst=REMOTE_MAC)/pkt)
37
38if os.fork() == 0:
39	time.sleep(1)
40	sendp(eth, iface=LOCAL_IF)
41	os._exit(0)
42
43ans=sniff(iface=LOCAL_IF, timeout=3, filter=
44    "ip6 and src "+REMOTE_ADDR6+" and dst "+LOCAL_ADDR6+" and proto ipv6-frag")
45for a in ans:
46	if a and a.type == ETH_P_IPV6 and \
47	    ipv6nh[a.payload.nh] == 'Fragment Header' and \
48	    a.payload.payload.offset == 0 and \
49	    ipv6nh[a.payload.payload.nh] == 'ICMPv6' and \
50	    icmp6types[a.payload.payload.payload.type] == 'Echo Reply':
51		id=a.payload.payload.payload.id
52		print "id=%#x" % (id)
53		if id != eid:
54			print "WRONG ECHO REPLY ID"
55			exit(2)
56		reply_cksum=a.payload.payload.payload.cksum
57		print "reply cksum=%#x" % (reply_cksum)
58		# change request checksum incrementaly and check with reply
59		diff_cksum=~(~reply_cksum+~(~request_cksum+~0x8000+0x8100))
60		if diff_cksum & 0xffff != 0xffff and diff_cksum & 0xffff != 0:
61			print "CHECKSUM ERROR diff cksum=%#x" % (diff_cksum)
62			exit(1)
63		exit(0)
64print "NO ECHO REPLY"
65exit(2)
66