在python中使用原始套接字发送IP数据包

Question

To summarize my problems:
I have 2 problems:

1. I can't send IP_PACKET variable
2. How do I set the flag in IP packet? (for send)

This is my code:

#! /usr/bin/python
import socket
import struct
import sys


def Create_SOCKET():
        global ST
        try:
                ST = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
        except socket.error as MSG:
                print "[ERROR] Socket creation error:\n", MSG
                sys.exit()


def IP_HEADER(Source_IP, Destination_IP):
        global IP_PACKET

        #Variable validation
        IP_VER = 4
        IP_IHL = 5
        IP_TOS = 0
        IP_TOL = 60
        IP_IDT = 54331
        IP_FLG = 2 # 0x02 DF
        IP_FOS = 0
        IP_TTL = 64
        IP_PROTO = socket.IPPROTO_TCP
        IP_CHECKSUM = 0

        IP_IHL_VER = (IP_VER << 4) + IP_IHL

        SRC_IP = socket.inet_aton(Source_IP)
        DST_IP = socket.inet_aton(Destination_IP)

        IP_PACKET = struct.pack("!BBHHHBBH4s4s", IP_IHL_VER, IP_TOS, IP_TOL, IP_IDT, IP_FOS, IP_TTL, IP_PROTO, IP_CHECKSUM, SRC_IP, DST_IP)



        def Send_PACKET(IFACE):
                try:
                        Create_SOCKET()
                        ST.bind((IFACE, 0))
                        ST.send(IP_PACKET)
                        print "[SUCESS] Packet was sent."
                except socket.error as MSG:
                        print "[ERROR] Packet can't send:\n", MSG
                        sys.exit()


IP_HEADER(sys.argv[1], sys.argv[2])
Send_PACKET(sys.argv[3])

Python version: 2.7
Operation system: Ubuntu 16.04
Thank you for helping me.

Answer 1

Your scoping is wrong, the function is defined inside some other function so it is only locally available:

def f1():
    pass

def f2():
    def f3():
        pass 
    f3() # works, local scope visible

f1() # works
f2() # works
try:    
    f3() # does not work, is not known, only inde f2()'s scope known
except NameError as ne:
    print(ne)

Output:

name 'f3' is not defined

To fix your structure, make IP_HEADER(Source_IP, Destination_IP): return the constructed IP_PACKET ,store it into a variable and provide it to Send_PACKET(IFACE,data) - also unindent Send_PACKET(...) :

def IP_HEADER(Source_IP, Destination_IP):
    # your code
    return IP_PACKET

def Send_PACKET(IFACE,data):  # unindent 4 spaces so its in normal scope
    # your code, use data instead of IP_PACKET

data = IP_HEADER(sys.argv[1], sys.argv[2])
Send_PACKET(sys.argv[3], data)

Answer 2

The solution of the first problem is:

global IP_PACKET
IP_PACKET =[]