watch.py

diffmks = 0.1 * 10**6
for i in range(20):
  p=sniff(count=1, lfilter=lambda x: x.haslayer(ICMP));
  r=IP(dst=p[0][IP].src)/ICMP(type="echo-reply", code=p[0][ICMP].code, id=p[0][ICMP].id, seq=p[0][ICMP].seq)/p[0].load;
  sec, mks =  unpack('QQ', r.load[0:16]);     
  mks += diffmks;     
  load = pack('QQ', sec, mks) + r.load[16:];     
  r.load = load;     
  send(r, loop=0);