1#!/usr/local/bin/python2.7 2 3import os 4import threading 5from addr import * 6from scapy.all import * 7 8class Sniff1(threading.Thread): 9 filter = None 10 captured = None 11 packet = None 12 def __init__(self): 13 # clear packets buffered by scapy bpf 14 sniff(iface=LOCAL_IF, timeout=1) 15 super(Sniff1, self).__init__() 16 def run(self): 17 self.captured = sniff(iface=LOCAL_IF, filter=self.filter, 18 count=1, timeout=3) 19 if self.captured: 20 self.packet = self.captured[0] 21 22e=Ether(src=LOCAL_MAC, dst=REMOTE_MAC) 23ip6=IPv6(src=FAKE_NET_ADDR6, dst=REMOTE_ADDR6) 24tport=os.getpid() & 0xffff 25 26print "Send SYN packet, receive SYN+ACK." 27syn=TCP(sport=tport, dport='chargen', seq=1, flags='S', window=(2**16)-1) 28synack=srp1(e/ip6/syn, iface=LOCAL_IF, timeout=5) 29 30if synack is None: 31 print "ERROR: no SYN+ACK from chargen server received" 32 exit(1) 33 34print "Send ACK packet, receive chargen data." 35ack=TCP(sport=synack.dport, dport=synack.sport, seq=2, flags='A', 36 ack=synack.seq+1, window=(2**16)-1) 37data=srp1(e/ip6/ack, iface=LOCAL_IF, timeout=5) 38 39if data is None: 40 print "ERROR: no data from chargen server received" 41 exit(1) 42 43print "Fill our receive buffer." 44time.sleep(1) 45 46# srp1 cannot be used, TCP data will not match outgoing ICMP6 packet 47sniffer = Sniff1() 48sniffer.filter = \ 49 "ip6 and src %s and tcp port %u and dst %s and tcp port %u" % \ 50 (ip6.dst, syn.dport, ip6.src, syn.sport) 51sniffer.start() 52time.sleep(1) 53 54print "Send ICMP6 packet too big packet with MTU 1300." 55icmp6=ICMPv6PacketTooBig(mtu=1300)/data.payload 56sendp(e/IPv6(src=LOCAL_ADDR6, dst=REMOTE_ADDR6)/icmp6, iface=LOCAL_IF) 57 58print "Path MTU discovery will resend first data with length 1300." 59sniffer.join(timeout=5) 60ans = sniffer.packet 61 62if len(ans) == 0: 63 print "ERROR: no data retransmit from chargen server received" 64 exit(1) 65data=ans[0] 66 67print "Cleanup the other's socket with a reset packet." 68rst=TCP(sport=synack.dport, dport=synack.sport, seq=2, flags='AR', 69 ack=synack.seq+1) 70sendp(e/ip6/rst, iface=LOCAL_IF) 71 72len = data.plen + len(IPv6()) 73print "len=%d" % len 74if len != 1300: 75 print "ERROR: TCP data packet len is %d, expected 1300." % len 76 exit(1) 77 78exit(0) 79