用python编程实现对DHCP客户端和服务器的模拟
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用python编写两个代码，用于模拟DHCP协议的动态分配IP的过程，因为之前遇到一个课程实现，不下心选择了DHCP这个题目，网上能找到的资料不多，为此自己研究一晚上，写了这个不全但是还能勉强糊弄过得去的代码，因为第二天就要验收，所以没来得及做更多优化，也没有做窗口，反正能过就行。本文仅模拟客户端第一次请求，即客户端发送discover广播报文，服务器响应offer报文，客户端发送request报文，服务器响应ACK确认报文。客户端代码可复制多份，形成多客户端，复制后的每个客户端的mac地址记得改一下，不改也能运行。代码中存在一些多余冗余，主要是本人调式用的，后续IP地址租用等等自己改代码，这里只模拟了四个报文，服务器一直监听端口，对响应报文给予响应，但是没有对request的IP地址进行验证，需要的同学自己该代码。通过抓包软件可以抓到DHCP报文，这里用到python第三方库scapy，和Pycharm软件，自己去下载，服务器单独运行在一个pycharm项目，客户端单独运行pycharm项目。需要用窗口显示的可以自己弄一个显示窗口，运行结果如下：
服务器端：
客户端10：
客户端20：
服务器代码：
from scapy.all import *
import random
import time
from scapy.layers.dhcp import DHCP, BOOTP
from scapy.layers.inet import IP, UDP
from scapy.layers.l2 import Ether
def build_dns_option(dns_servers):
"""
手动构建 DNS 服务器 DHCP 选项的字节串
"""
option_code = 6 # domain_name_server 的 DHCP 选项代码
option_data = b''.join([socket.inet_aton(server) for server in dns_servers.split(',')])
option_length = len(option_data) + 1 # 长度包括选项代码本身
return bytes([option_code]) + bytes([option_length]) + option_data
def respond_to_dhcp_discover(pkt):
if DHCP in pkt and pkt[DHCP].options[0][1] == 1:
client_mac = pkt[Ether].src
print(f"\n发现discover请求,mac地址为：{client_mac}")
client_ip = "192.168.1." + str(random.randint(100, 200)) #随机分配ip给客户端
global clien_t_ip #定义全局变量存client的ip
clien_t_ip = client_ip
dns_option = build_dns_option("8.8.8.8,8.8.4.4") #构建 DNS 服务器 DHCP 选项的字节串
dhcp_offer = Ether(src=get_if_hwaddr(conf.iface), dst=client_mac) / \
IP(src="192.168.1.1", dst="255.255.255.255") / \
UDP(sport=67, dport=68) / \
BOOTP(op=2, chaddr=client_mac, yiaddr=client_ip) / \
DHCP(options=[
("message-type", "offer"),
("server_id", "192.168.1.1"),
("lease_time", 43200),
("subnet_mask", "255.255.255.0"),
("router", "192.168.1.1"),
(b'\x06' + bytes([len(dns_option)]) + dns_option), # 添加 DNS 服务器选项
("end")
])
sendp(dhcp_offer, verbose=0)
print(f"发送DHCP Offer给:客户端mac: {client_mac} 随机分配客户端IP为： {client_ip}")
print(" 为DHCP 客户端可以提供 IP 地址中……")
def respond_to_dhcp_request(pkt):
if DHCP in pkt and pkt[DHCP].options[0][1] == 3:
print("发现request请求报文")
requested_ip = pkt[DHCP].options[2][1] #
client_mac = pkt[Ether].src
print(f"对方mac地址为：{client_mac}")
server_id = pkt[DHCP].options[2][1]
# print(f"requested_ip{requested_ip}\n")
print(f"确认是本服务器id：{server_id}")
if server_id == "192.168.1.1":
dns_option = build_dns_option("8.8.8.8,8.8.4.4") # 构建 DNS 服务器 DHCP 选项的字节串
# print("22222222222")
dhcp_ack = Ether(src=get_if_hwaddr(conf.iface), dst=client_mac) / \
IP(src="192.168.1.1", dst="255.255.255.255") / \
UDP(sport=67, dport=68) / \
BOOTP(op=2, chaddr=client_mac, yiaddr=clien_t_ip) / \
DHCP(options=[
("message-type", "ack"),
("server_id", server_id),
("lease_time", 43200),
("subnet_mask", "255.255.255.0"),
("router", "192.168.1.1"),
(b'\x06' + bytes([len(dns_option)]) + dns_option), # 手动添加 DNS 服务器选项
("end")
])
# print("33333333333")
sendp(dhcp_ack, verbose=0)
print(f"发送DHCP ACK 确认 to {client_mac} for IP {clien_t_ip}")
print("分配IP成功！\n\n")
# 监听并同时响应DISCOVER和REQUEST报文
while(1):
filter_str = "udp and (port 67 or port 68)"
sniff(prn=lambda x: respond_to_dhcp_discover(x) or respond_to_dhcp_request(x),
filter=filter_str, store=0, iface="WLAN") #WLAN是网卡
客户端10代码：
from scapy.all import *
import random
import time
import binascii
from scapy.layers.dhcp import BOOTP, DHCP
from scapy.layers.inet import IP, UDP
from scapy.layers.l2 import Ether
def send_dhcp_discover(interface="WLAN"):
"""
发送DHCP DISCOVER报文
"""
# 使用 binascii.hexlify 转换MAC地址字符串为原始字节
mac_bytes = binascii.unhexlify("00:11:22:33:44:55".replace(':', ''))#这里修改客户端mac地址
#global clien_t_mac #定义全局变量用来存client_mac地址
#clien_t_mac = mac_bytes
#print(f"本地客户端mac为：{mac_bytes}")
dhcp_discover = Ether(src=mac_bytes, 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_bytes) \
/ DHCP(options=[("message-type", "discover"), ("end")])
sendp(dhcp_discover, iface=interface, verbose=0)
print("客户端已发送discover广播请求：src=\"0.0.0.0\", dst=\"255.255.255.255\"")
def respond_to_dhcp_offer(pkt):
"""
响应接收到的DHCP OFFER报文
"""
if DHCP in pkt and pkt[DHCP].options[0][1] == 2: # 检查是否为DHCP OFFER报文
server_id = pkt[DHCP].options[1][1] # 服务器ID
offered_ip = pkt[BOOTP].yiaddr # 提供的IP地址
client_mac = pkt[Ether].src # 客户端MAC地址
print(f"确认与本机mac地址相同：{client_mac}")
print(f"客户端接收到offer响应报文:服务器ID:{server_id} offer提供的ip:{offered_ip}")
# 使用正确的方法处理MAC地址
mac_bytes = binascii.unhexlify("00:11:22:33:44:55".replace(':', ''))
# 构造DHCP REQUEST报文
dhcp_request = Ether(src=mac_bytes, 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_bytes, yiaddr=offered_ip) / \
DHCP(options=[
("message-type", "request"),
("requested_addr", offered_ip),
("server_id", server_id),
("end")
])
sendp(dhcp_request, verbose=0) #发送DHCP REQUEST报文
print(f"向服务器发送广播(request)请求ip地址： {offered_ip} 服务器ip: {server_id}")
def ack_ack(pkt):
if DHCP in pkt and pkt[DHCP].options[0][1] == 5:
client_ip = pkt[BOOTP].yiaddr # 分配给客户端的IP地址
subnet_mask = next((opt[1] for opt in pkt[DHCP].options if opt[0] == 'subnet_mask'), None) # 子网掩码
router_ip = next((opt[1] for opt in pkt[DHCP].options if opt[0] == 'router'), None) # 默认网关
dns_servers = [opt[1] for opt in pkt[DHCP].options if opt[0] == 6] # DNS服务器列表
print(f"客户端接收到DHCP ACK包：")
print(f" - 分配的IP地址: {client_ip}")
if subnet_mask:
print(f" - 子网掩码: {subnet_mask}")
if router_ip:
print(f" - 默认网关: {router_ip}")
filter_str = "udp and (port 67 or port 68)" # 设置过滤器，只捕获DHCP流量
send_dhcp_discover() # 先发送一个DHCP DISCOVER报文
#sniff(prn=respond_to_dhcp_offer, filter=filter_str, store=0, iface="WLAN") # 然后开始监听并响应OFFER报文
sniff(prn=lambda x: respond_to_dhcp_offer(x) or ack_ack(x),
filter=filter_str, store=0, iface="WLAN")
客户端20代码：
from scapy.all import *
import random
import time
import binascii
from scapy.layers.dhcp import BOOTP, DHCP
from scapy.layers.inet import IP, UDP
from scapy.layers.l2 import Ether
def send_dhcp_discover(interface="WLAN"):
"""
发送DHCP DISCOVER报文
"""
# 使用 binascii.hexlify 转换MAC地址字符串为原始字节
mac_bytes = binascii.unhexlify("00:11:22:33:44:66".replace(':', ''))
global clien_t_mac #定义全局变量用来存client_mac地址
clien_t_mac = mac_bytes
# print(f"客户端mac为：{clien_t_mac}")
dhcp_discover = Ether(src=mac_bytes, 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_bytes) \
/ DHCP(options=[("message-type", "discover"), ("end")])
sendp(dhcp_discover, iface=interface, verbose=0)
print("客户端已发送discover广播请求：src=\"0.0.0.0\", dst=\"255.255.255.255\"")
def respond_to_dhcp_offer(pkt):
"""
响应接收到的DHCP OFFER报文
"""
if DHCP in pkt and pkt[DHCP].options[0][1] == 2: # 检查是否为DHCP OFFER报文
server_id = pkt[DHCP].options[1][1] # 服务器ID
offered_ip = pkt[BOOTP].yiaddr # 提供的IP地址
client_mac = pkt[Ether].src # 客户端MAC地址
# print(f"确认与本机mac地址相同：{client_mac}")
print(f"客户端接收到offer响应报文:服务器ID:{server_id} offer提供的ip:{offered_ip}")
# 使用正确的方法处理MAC地址
mac_bytes = binascii.unhexlify("00:11:22:33:44:66".replace(':', ''))
# 构造DHCP REQUEST报文
dhcp_request = Ether(src=mac_bytes, 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_bytes, yiaddr=offered_ip) / \
DHCP(options=[
("message-type", "request"),
("requested_addr", offered_ip),
("server_id", server_id),
("end")
])
sendp(dhcp_request, verbose=0) #发送DHCP REQUEST报文
print(f"向服务器发送广播(request)请求ip地址： {offered_ip} 服务器ip: {server_id}")
def ack_ack(pkt):
if DHCP in pkt and pkt[DHCP].options[0][1] == 5:
client_ip = pkt[BOOTP].yiaddr # 分配给客户端的IP地址
subnet_mask = next((opt[1] for opt in pkt[DHCP].options if opt[0] == 'subnet_mask'), None) # 子网掩码
router_ip = next((opt[1] for opt in pkt[DHCP].options if opt[0] == 'router'), None) # 默认网关
dns_servers = [opt[1] for opt in pkt[DHCP].options if opt[0] == 6] # DNS服务器列表
print(f"客户端接收到DHCP ACK包：")
print(f" - 分配的IP地址: {client_ip}")
if subnet_mask:
print(f" - 子网掩码: {subnet_mask}")
if router_ip:
print(f" - 默认网关: {router_ip}")
filter_str = "udp and (port 67 or port 68)" # 设置过滤器，只捕获DHCP流量
send_dhcp_discover() # 先发送一个DHCP DISCOVER报文
#sniff(prn=respond_to_dhcp_offer, filter=filter_str, store=0, iface="WLAN") # 然后开始监听并响应OFFER报文
sniff(prn=lambda x: respond_to_dhcp_offer(x) or ack_ack(x),
filter=filter_str, store=0, iface="WLAN")
备注：大学的同学拿回去记得改一下代码啊！！！
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