给一个NFQUEUE的发包示例

下面是一个基于Python的NFQUEUE的发包示例：

import socket
from struct import pack

# 构造IP头部
def make_ip_header(src_ip, dst_ip):
    ip_ver = 4
    ip_ihl = 5
    ip_tos = 0
    ip_tot_len = 40
    ip_id = 54321
    ip_frag_off = 0
    ip_ttl = 255
    ip_proto = socket.IPPROTO_TCP
    ip_check = 0
    ip_saddr = socket.inet_aton(src_ip)
    ip_daddr = socket.inet_aton(dst_ip)
    ip_ihl_ver = (ip_ver << 4) + ip_ihl
    ip_header = pack('!BBHHHBBH4s4s', ip_ihl_ver, ip_tos, ip_tot_len, ip_id,
                     ip_frag_off, ip_ttl, ip_proto, ip_check, ip_saddr, ip_daddr)
    return ip_header

# 构造TCP头部
def make_tcp_header(src_port, dst_port):
    tcp_seq = 0
    tcp_ack_seq = 0
    tcp_doff = 5
    tcp_flags = 0x02
    tcp_window = socket.htons(5840)
    tcp_check = 0
    tcp_urg_ptr = 0
    tcp_offset_res = (tcp_doff << 4) + 0
    tcp_header = pack('!HHLLBBHHH', src_port, dst_port, tcp_seq, tcp_ack_seq,
                      tcp_offset_res, tcp_flags, tcp_window, tcp_check, tcp_urg_ptr)
    return tcp_header

# 构造TCP数据
def make_tcp_data():
    data = b'Hello, World!'
    return data

# 发送数据包
def send_packet(src_ip, dst_ip, src_port, dst_port):
    # 构造IP头部
    ip_header = make_ip_header(src_ip, dst_ip)

    # 构造TCP头部
    tcp_header = make_tcp_header(src_port, dst_port)

    # 构造TCP数据
    tcp_data = make_tcp_data()

    # 计算TCP校验和
    pseudo_header = pack('!4s4sBBH', socket.inet_aton(src_ip),
                         socket.inet_aton(dst_ip), 0, socket.IPPROTO_TCP, len(tcp_header) + len(tcp_data))
    pseudo_header = pseudo_header + tcp_header + tcp_data
    tcp_check = checksum(pseudo_header)

    # 构造TCP头部（包含校验和）
    tcp_header = pack('!HHLLBBH', src_port, dst_port, 0, 0, (5 << 4) + 0x02, tcp_check, tcp_header[6])

    # 构造TCP数据包
    packet = ip_header + tcp_header + tcp_data

    # 创建一个原始套接字
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)

    # 发送数据包
    s.sendto(packet, (dst_ip, 0))

# 计算校验和
def checksum(data):
    if len(data) % 2:
        data = data + b'\x00'
    words = [int.from_bytes(data[i:i + 2], 'big') for i in range(0, len(data), 2)]
    chksum = sum(words)
    while chksum >> 16:
        chksum = (chksum >> 16) + (chksum & 0xffff)
    chksum = ~chksum & 0xffff
    return chksum

# 发送数据包
send_packet('192.168.1.100', '192.168.1.1', 8888, 80)

该示例可以构造一个TCP数据包并发送到目标IP地址和端口号。您可以根据需要修改源IP地址、目标IP地址、源端口号和目标端口号。