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#!/usr/local/bin/python3
# new fragment completely overlaps old one
# |----|
# |XXXX|
# |------------|
# If an existing fragment is completely overlapped by the current
# one, drop the older fragment.
# TAILQ_REMOVE(&frag->fr_queue, after, fr_next);
# Smaller older fragments might not have been nearer, and might be
# trying to overwrite a very small part of the full packet.
import os
import threading
from addr import *
from scapy.all import *
class Sniff1(threading.Thread):
filter = None
captured = None
packet = None
def run(self):
self.captured = sniff(iface=SRC_IF, filter=self.filter,
count=1, timeout=3)
if self.captured:
self.packet = self.captured[0]
dstaddr=sys.argv[1]
pid=os.getpid()
eid=pid & 0xffff
payload=b"ABCDEFGHIJKLOMNOQRSTUVWX"
dummy=b"01234567"
packet=IP(src=SRC_OUT, dst=dstaddr)/ICMP(type='echo-request', id=eid)/payload
fid=pid & 0xffff
frag0=bytes(packet)[20:28]
frag1=dummy
frag2=bytes(packet)[28:52]
pkt0=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=0, flags='MF')/frag0
pkt1=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=2, flags='MF')/frag1
pkt2=IP(src=SRC_OUT, dst=dstaddr, proto=1, id=fid, frag=1)/frag2
eth=[]
eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt0)
eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt1)
eth.append(Ether(src=SRC_MAC, dst=PF_MAC)/pkt2)
sniffer = Sniff1();
sniffer.filter = "ip and src %s and dst %s and icmp" % (dstaddr, SRC_OUT)
sniffer.start()
time.sleep(1)
sendp(eth, iface=SRC_IF)
sniffer.join(timeout=5)
a = sniffer.packet
if a and a.type == ETH_P_IP and \
a.payload.proto == 1 and \
a.payload.frag == 0 and a.payload.flags == 0 and \
icmptypes[a.payload.payload.type] == 'echo-reply':
id=a.payload.payload.id
print("id=%#x" % (id))
if id != eid:
print("WRONG ECHO REPLY ID")
exit(2)
load=a.payload.payload.payload.load
print("payload=%s" % (load))
if load == payload:
exit(0)
print("PAYLOAD!=%s" % (payload))
exit(1)
print("NO ECHO REPLY")
exit(2)
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