Send TCP RST with checksum

gistfile1.txt

#!/usr/bin/env python3
import socket
from struct import pack
from time import sleep

# 
# |--------------------|--------------------|
# |     SOURCE PORT    |   DESTINATION PORT |
# |--------------------|--------------------|
# |            SEQUENCE NUMBER              |
# |--------------------|--------------------|
# |          ACKNOWLEDGMENT NUMBER          |
# |--------------------|--------------------|
# | DO:4|RSV:3|FLAGSi:9|      WINDOW        |
# |--------------------|--------------------|
# |    Checksum        |    URGENT POINTER  |
# |--------------------|--------------------|
# 
# 

def ip_header(src, dst):
    return pack("!BBHHHBBH4s4s", 69, 0, 0, 1, 0, 64, 6, 0, socket.inet_aton(src), socket.inet_aton(dst))

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

    s = (s>>16) + (s & 0xffff);
    #s = s + (s >> 16);
    #complement and mask to 4 byte short
    s = ~s & 0xffff

    return s

# pack function allows you to pack different values (bytes, shorts, ints, strings ) into bytes
# Format:
# ! - network byte order
# B unsigned char
# H unsigned short
# I unsigned int
# L unsigned long
# Q unsigned long long
# s char[]

my_ip = '10.10.11.157' # change to your ip
target_ip = '10.10.11.65'
# Warning: you need r00t to run this
# Good luck (:
sock = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
sock.setsockopt(socket.SOL_IP, socket.IP_HDRINCL, 1)
ip_hdr = ip_header(my_ip, target_ip)
# source port: 1337,destination port: 7331
# ack: 81321, seq: 321342,no data
# checksum may be correct or incorrect*

# TODO - fix this 2 variables
tcp_hdr = pack("!HHIIBBHHH", 1337, 7331, 321342, 81321, 240, 4, 0, 0, 0)
psh = pack('!4s4sBBH' , socket.inet_aton(my_ip) , socket.inet_aton(target_ip) , 0 , socket.IPPROTO_TCP , len(tcp_hdr))
psh = psh + tcp_hdr
tcp_hdr = pack("!HHIIBBHHH", 1337, 7331, 321342, 81321, 240, 4, 0, checksum(psh), 0)
data = b''


while True:
    sock.sendto(ip_hdr + tcp_hdr + data, (target_ip, 0))
    sleep(1)