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我想使用原始套接字发送带有欺骗 IP 的数据包。我找到了以下 python 代码，因为我是原始套接字的新手，我在 Ubuntu 上尝试过。

有没有办法将数据包从本地网络发送到外部网络？如果我在 LAN 内运行代码，则代码可以成功运行，但是当我尝试将数据包发送到 LAN 外部的服务器时，它永远不会到达目的地。我检查了路由器的首选项，但它没有针对传出 IP 流量的过滤器。

谁能帮助我，因为我不知道出了什么问题。

# some imports
import socket, sys, subprocess, shlex
from struct import *

# checksum functions needed for calculation checksum
def checksum(msg):
    s = 0

    # loop taking 2 characters at a time
    for i in range(0, len(msg), 2):
        w = ord(msg[i]) + (ord(msg[i+1]) << 8 )
        s = s + w

    s = (s>>16) + (s & 0xffff);
    s = s + (s >> 16);

    #complement and mask to 4 byte short
    s = ~s & 0xffff

    return s

#create a raw socket
try:    
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
    print 'all fine'
except socket.error , msg:
    print 'Socket could not be created. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
    sys.exit()

# tell kernel not to put in headers, since we are providing it, when using IPPROTO_RAW this is not necessary
# s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

# now start constructing the packet
packet = '';

source_ip = '195.251.xxx.xxx'
dest_ip = '85.64.xxx.xxx' # or socket.gethostbyname('www.google.com')

# ip header fields
ip_ihl = 5
ip_ver = 4
ip_tos = 0
ip_tot_len = 0  # kernel will fill the correct total length
ip_id = 54321   #Id of this packet
ip_frag_off = 0
ip_ttl = 255
ip_proto = socket.IPPROTO_TCP
ip_check = 0    # kernel will fill the correct checksum
ip_saddr = socket.inet_aton(source_ip)   #Spoof the source ip address if you want to
ip_daddr = socket.inet_aton(dest_ip)

ip_ihl_ver = (ip_ver << 4) + ip_ihl

# the ! in the pack format string means network order
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)

# tcp header fields
tcp_source = 1234   # source port
tcp_dest = 80   # destination port
tcp_seq = 454
tcp_ack_seq = 0
tcp_doff = 5    #4 bit field, size of tcp header, 5 * 4 = 20 bytes
#tcp flags
tcp_fin = 0
tcp_syn = 1
tcp_rst = 0
tcp_psh = 0
tcp_ack = 0
tcp_urg = 0
tcp_window = socket.htons (5840)    #   maximum allowed window size
tcp_check = 0
tcp_urg_ptr = 0

tcp_offset_res = (tcp_doff << 4) + 0
tcp_flags = tcp_fin + (tcp_syn << 1) + (tcp_rst << 2) + (tcp_psh <<3) + (tcp_ack << 4) + (tcp_urg << 5)

# the ! in the pack format string means network order
tcp_header = pack('!HHLLBBHHH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags,  tcp_window, tcp_check, tcp_urg_ptr)

user_data = 'Hello, how are you'

# pseudo header fields
source_address = socket.inet_aton(source_ip)
dest_address = socket.inet_aton(dest_ip)
placeholder = 0
protocol = socket.IPPROTO_TCP
tcp_length = len(tcp_header) + len(user_data)

psh = pack('!4s4sBBH' , source_address , dest_address , placeholder , protocol , tcp_length);
psh = psh + tcp_header + user_data;

tcp_check = checksum(psh)
#print tcp_checksum

# make the tcp header again and fill the correct checksum - remember checksum is NOT in network byte order
tcp_header = pack('!HHLLBBH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags,  tcp_window) + pack('H' , tcp_check) + pack('!H' , tcp_urg_ptr)

# final full packet - syn packets dont have any data
packet = ip_header + tcp_header + user_data

#Send the packet finally - the port specified has no effect
s.sendto(packet, (dest_ip , tcp_dest ))    # put this in a loop if you want to flood the target
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