Scapy sniff() in a class that subclassess threading.Thread()

Question

I've got a strange issue with the Scapy sniff() function.

This is how my class is looking:

    from scapy.all import *
import sys
import datetime
import Queue
from threading import Thread

class packet_sniffer(Thread):
  def __init__(self,pass_queue):
    super(packet_sniffer,self).__init__()
    print 'Packet sniffer started'
    self.queue=pass_queue
    self.device_dict={}
    self.not_an_ap={}


  def PacketHandler(self,pkt):
    if pkt.haslayer(Dot11):
      sig_str = -(256-ord(pkt.notdecoded[-4:-3]))
      mac_addr=""
      ssid=""
      try:
        mac_addr=pkt.addr2
        ssid=pkt.info
      except:
        return
      if self.device_dict.has_key(pkt.addr2) and pkt.info!=self.device_dict[pkt.addr2]:
        output= "DIS MAC:%s RSSI:%s " %(pkt.addr2,sig_str)
        print output
        self.device_dict.pop(pkt.addr2)
        self.not_an_ap[pkt.addr2]=pkt.info
        self.queue.put(output)
      elif pkt.info=="" or pkt.info=="Broadcast":
        output= "DIS MAC:%s RSSI:%s " %(pkt.addr2,sig_str)
        print output
        self.queue.put(output)
      else:
        pot_mac=self.not_an_ap.get(pkt.addr2)
        if pot_mac == None:
          self.device_dict[pkt.addr2]=pkt.info

    def run(self):
      sniff(iface="mon.wlan0",prn=self.PacketHandler)

This code doesn't work when I call it from my Thread manager class:

EDIT: When I say it doesn't work, I mean that the sniff is either not operational or isn't calling PacketHandler. No error messages are outputted, and the rest of the program continues as normal

currentQueue=Queue()

#object setup
print'Initialising sniffer'
packet_sniffer_instance=packet_sniffer(currentQueue)
packet_sniffer_instance.daemon=True
packet_sniffer_instance.start()
time.sleep(1)

print'Finished initialising sniffer'

I included the sleep function after looking at this post: Scapy fails to sniff

However, when I move my sniff call to the __init__() function, it works, but then no subsequent threads can be called due to the packet_sniffer class being infinitely stuck in the __init__() function.

I'm fairly new programmer when it comes to python (not a new programmer overall, i have lots of experience), so I'm probably doing something really basic wrong.

TIA

James.

Answer 1

It seems that simply rearranging the class so that the run method came just under the __init__() method fixed the issue. I also stopped using the thread class and used the multiprocess class, which builds on the Thread class but allows greater concurrency.

The final class looks like this:

from scapy.all import *
import sys
import datetime
import Queue
from multiprocessing import Process

class packet_sniffer(Process):
  def __init__(self,pass_queue):
    super(packet_sniffer,self).__init__()
    print 'Packet sniffer started'
    #self.target=self.monitor()
    self.queue=pass_queue
    self.device_dict={}
    self.not_an_ap={}
    print 'END'

  def run(self):
    sniff(iface="en1",prn=self.PacketHandler)

  def PacketHandler(self,pkt):
    if(pkt.haslayer(ARP)):
      print pkt.src
    if pkt.haslayer(Dot11):
      sig_str = -(256-ord(pkt.notdecoded[-4:-3]))
      mac_addr=""
      ssid=""
      try:
        mac_addr=pkt.addr2
        ssid=pkt.info
      except:
        return
      if self.device_dict.has_key(pkt.addr2) and pkt.info!=self.device_dict[pkt.addr2]:
        output= "DIS MAC:%s RSSI:%s " %(pkt.addr2,sig_str)
        print output
        self.device_dict.pop(pkt.addr2)
        self.not_an_ap[pkt.addr2]=pkt.info
        self.queue.put(output)
      elif pkt.info=="" or pkt.info=="Broadcast":
        output= "DIS MAC:%s RSSI:%s " %(pkt.addr2,sig_str)
        print output
        self.queue.put(output)
      else:
        pot_mac=self.not_an_ap.get(pkt.addr2)
        if pot_mac == None:
          self.device_dict[pkt.addr2]=pkt.info

I'm not entirely sure why the arrangement of the methods makes a difference in this instance.