# forge packets for testing liminix and send them via the qemu udp # multicast socket interface MCAST_GRP = '230.0.0.1' MCAST_PORT = 1235 MULTICAST_TTL = 2 TIMEOUT = 10 # seconds from warnings import filterwarnings filterwarnings("ignore") import random import binascii import socket import time import json from builtins import bytes, bytearray from scapy.all import Ether, IP, UDP, BOOTP, DHCP, sendp, send, raw class JSONEncoderWithBytes(json.JSONEncoder): def default(self, obj): if isinstance(obj, (bytes, bytearray)): return obj.decode('utf-8') return json.JSONEncoder.default(self, obj) def dhcp_option(pkt, label): if pkt.haslayer(DHCP): for i in pkt[DHCP].options: l, v = i if l == label: return v return None def is_dhcp_offer(pkt): val = dhcp_option(pkt, 'message-type') return (val == 2) def mac_to_bytes(mac_addr: str) -> bytes: """ Converts a MAC address string to bytes. """ return int(mac_addr.replace(":", ""), 16).to_bytes(6, "big") client_mac = "01:02:03:04:05:06" discover = ( Ether(dst="ff:ff:ff:ff:ff:ff") / IP(src="0.0.0.0", dst="255.255.255.255") / UDP(sport=68, dport=67) / BOOTP( chaddr=mac_to_bytes(client_mac), xid=random.randint(1, 2**32-1), ) / DHCP(options=[("message-type", "discover"), "end"]) ) payload = raw(discover) sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) sock.settimeout(TIMEOUT) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, MULTICAST_TTL) sock.bind((MCAST_GRP, MCAST_PORT)) host = socket.gethostbyname(socket.gethostname()) sock.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton(host)) sock.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(MCAST_GRP) + socket.inet_aton(host)) endtime = time.time() + TIMEOUT sock.sendto(payload, (MCAST_GRP, MCAST_PORT)) while time.time() < endtime: try: data, addr = sock.recvfrom(1024) except socket.error: print('Exception') else: reply = Ether(data) if is_dhcp_offer(reply): opts = dict([o for o in reply[DHCP].options if type(o) is tuple]) print(json.dumps(opts, cls=JSONEncoderWithBytes)) exit(0) exit(1)