TUN/TAP in python

main.py

import os
from fcntl import ioctl
import struct
import time
import random
from threading import Thread

from pyroute2 import IPRoute
from pypacker.layer3.ip import IP
from pypacker.layer3.ip6 import IP6
from pypacker.layer3.icmp import ICMP


TUNSETIFF = 0x400454ca
IFF_TUN   = 0x0001
IFF_TAP   = 0x0002
IFF_NO_PI = 0x1000


def main():
    fid = os.open("/dev/net/tun", os.O_RDWR)
    ioctl(fid, TUNSETIFF, struct.pack("16sH", b"tun0", IFF_TUN | IFF_NO_PI))
    set_addr('tun0', '10.0.0.1')

    read_thread = Thread(target=read_input, args=(fid,))
    read_thread.start()

    req_nr = 1
    req_id = random.randint(1, 65000)
    while True:
        icmp_req = IP(src_s="10.0.0.4", dst_s="8.8.8.8", p=1) +\
            ICMP(type=8) +\
            ICMP.Echo(id=req_id, seq=req_nr, body_bytes=b"test")
        os.write(fid, icmp_req.bin())
        time.sleep(1)
        req_nr += 1


def read_input(fid) -> None:
    while True:
        data = os.read(fid, 1500)
        parse_packet(data)


def parse_packet(data: bytes):
    try:
        packet = IP(data)
    except:
        packet = IP6(data)
    print(packet)
    print()


def set_addr(dev: str, addr: str) -> None:
    ip = IPRoute()
    idx = ip.link_lookup(ifname=dev)[0]
    ip.addr('add', index=idx, address=addr, prefixlen=24)
    ip.link('set', index=idx, state='up')
    ip.close()


main()

requirements.txt

NetLink==0.1
pypacker==4.0
pyroute2==0.4.19

setup_nat.sh

#!/bin/bash

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -P FORWARD ACCEPT
iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -j MASQUERADE