1#!/usr/local/bin/python2.7 2# check wether path mtu to dst is 1300 3 4import os 5from addr import * 6from scapy.all import * 7 8dstaddr=sys.argv[1] 9pid=os.getpid() & 0xffff 10hdr=IP(flags="DF", src=SRC_OUT, dst=dstaddr)/ICMP(id=pid) 11payload="a" * (1400 - len(str(hdr))) 12ip=hdr/payload 13eth=Ether(src=SRC_MAC, dst=PF_MAC)/ip 14a=srp1(eth, iface=SRC_IF, timeout=2) 15 16if a and a.payload.payload.type==3 and a.payload.payload.code==4: 17 mtu=a.payload.payload.nexthopmtu 18 print "mtu=%d" % (mtu) 19 if mtu == 1300: 20 exit(0) 21 print "MTU!=1300" 22 exit(1) 23print "MTU=UNKNOWN" 24exit(2) 25