#!/usr/local/bin/python2.7
# check wether path mtu to dst is 1300

import os
from addr import *
from scapy.all import *

dstaddr=sys.argv[1]
eid=os.getpid() & 0xffff
hdr=IP(flags="DF", src=SRC_OUT, dst=dstaddr)/ICMP(type='echo-request', id=eid)
payload="a" * (1400 - len(str(hdr)))
ip=hdr/payload
eth=Ether(src=SRC_MAC, dst=PF_MAC)/ip
a=srp1(eth, iface=SRC_IF, timeout=2)

if a is None:
	print "no packet sniffed"
	exit(2)
if a and a.payload.payload.type==3 and a.payload.payload.code==4:
	mtu=a.payload.payload.nexthopmtu
	print "mtu=%d" % (mtu)
	if mtu == 1300:
		exit(0)
	print "MTU!=1300"
	exit(1)
print "MTU=UNKNOWN"
exit(2)