pydhcp/dhcp_client.py

#! /usr/bin/env python
from dhcp_packet import *
import socket
import random
from type_hwmac import *
import pcap
import dpkt
import binascii
import time

class DhcpClient:
  def send_packet(self, mac, iface, xid):
    dhcp = DhcpPacket()
    dhcp.SetOption('op', [1]);
    dhcp.SetOption('htype', [1]);
    dhcp.SetOption('hlen', [6]);
    dhcp.SetOption('xid', xid);
    dhcp.SetOption('chaddr', hwmac(mac).list());
    dhcp.SetOption('dhcp_message_type', [1]);
    dhcp.SetOption('parameter_request_list', [12]);

    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
    s.setsockopt(socket.SOL_SOCKET, 25, iface + '\0')
    s.bind(('', 68))
    s.sendto(dhcp.EncodePacket(), ('255.255.255.255', 67))
    s.close()


  def get_offer(self, mac, iface, timeout = 10):
    pc = pcap.pcap(name=iface)
    pc.setfilter('udp and udp src port 67 and udp dst port 68')
    xid = [random.randrange(255), random.randrange(255),
        random.randrange(255), random.randrange(255)]
    self.send_packet(mac, iface, xid)
    pc.setnonblock()
    start = time.time()
    while True:
        try:
            for pkt in pc.readpkts():
                eth = dpkt.ethernet.Ethernet(pkt[1])
                dh = DhcpPacket()
                dh.DecodePacket(eth.data.data.data)
                if (dh.GetOption('xid') == xid and
                    dh.GetOption('op') == [2] and
                    dh.GetOption('dhcp_message_type') == [2]):
                    return dh
        except:
            pass
        time.sleep(0.5)
        if time.time() - start >= timeout:
            return None