tiny_dhcp.py

tiny_dhcp.py

from threading import Thread
from scapy.layers.inet import Ether, IP, UDP
from scapy.layers.dhcp import DHCP, BOOTP
from scapy.config import conf
from scapy.arch import get_if_raw_hwaddr, get_if_hwaddr
from scapy.sendrecv import sniff, sendp
import queue
import time
BOOTREPLY = 2
def dhcp_reqresp(interface="wwan0", timeout=5):
    q = queue.Queue()

    conf.checkIPaddr=False
    BOOTREPLY = 2

    _, rawmacaddress = get_if_raw_hwaddr(interface)
    macaddress= get_if_hwaddr(interface)

    def listen():
        sniff(filter="udp and (port 67 or port 68)", prn=lambda pkt: q.put(pkt), store=0, count=2, timeout=timeout, iface=interface)

    def start_listener():
        thread = Thread(target=listen)
        thread.start()
        return thread

    listener_thread = start_listener()
    time.sleep(1.0)
    discover = Ether(dst='ff:ff:ff:ff:ff:ff', src=macaddress, type=0x0800) / IP(src='0.0.0.0', dst='255.255.255.255') / UDP(dport=67,sport=68) / BOOTP(op=1, chaddr=rawmacaddress) / DHCP(options=[('message-type','discover'), ('end')])
    sendp(discover, iface=interface, verbose=False)
    try:
        req = q.get(timeout=timeout//2)
        rsp = q.get(timeout=timeout//2)
    except queue.Empty:
        return None
    if rsp[BOOTP]:
        if rsp[BOOTP].op == BOOTREPLY:
            client = rsp[BOOTP].yiaddr
            server = rsp[BOOTP].siaddr
            return rsp, client, server
    rsp.display()

if __name__ == "__main__":
    import sys
    results = dhcp_reqresp(interface=sys.argv[1])
    if results and len(results) == 3:
        results[0].display()
        print(results[1], results[2])