1#!/usr/local/bin/python3
2
3print("udp fragments splitted after udp header")
4
5# |----|
6#      |--------|
7
8import os
9from addr import *
10from scapy.all import *
11
12pid=os.getpid()
13uport=pid & 0xffff
14# inetd ignores UDP packets from privileged port or nfs
15if uport < 1024 or uport == 2049:
16	uport+=1024
17payload=b"ABCDEFGHIJKLMNOP"
18packet=IP(src=LOCAL_ADDR, dst=REMOTE_ADDR)/ \
19    UDP(sport=uport, dport=7)/payload
20frag=[]
21fid=pid & 0xffff
22frag.append(IP(src=LOCAL_ADDR, dst=REMOTE_ADDR, proto=17, id=fid,
23    flags='MF')/bytes(packet)[20:28])
24frag.append(IP(src=LOCAL_ADDR, dst=REMOTE_ADDR, proto=17, id=fid,
25    frag=1)/bytes(packet)[28:44])
26eth=[]
27for f in frag:
28	eth.append(Ether(src=LOCAL_MAC, dst=REMOTE_MAC)/f)
29
30if os.fork() == 0:
31	time.sleep(1)
32	sendp(eth, iface=LOCAL_IF)
33	os._exit(0)
34
35ans=sniff(iface=LOCAL_IF, timeout=3, filter=
36    "ip and src "+REMOTE_ADDR+" and dst "+LOCAL_ADDR+" and udp")
37for a in ans:
38	if a and a.type == ETH_P_IP and \
39	    a.payload.proto == 17 and \
40	    a.payload.frag == 0 and a.payload.flags == 0 and \
41	    a.payload.payload.sport == 7:
42		port=a.payload.payload.dport
43		print("port=%d" % (port))
44		if port != uport:
45			print("WRONG UDP ECHO REPLY PORT")
46			exit(2)
47		data=a.payload.payload.payload.load
48		print("payload=%s" % (data))
49		if data == payload:
50			exit(0)
51		print("PAYLOAD!=%s" % (payload))
52		exit(1)
53print("NO UDP ECHO REPLY")
54exit(2)
55