iximiuz

# python3
import asyncio
import sys

counter = 0

async def run_server(host, port):
  server = await asyncio.start_server(serve_client, host, port)
  await server.serve_forever()

iximiuz

#!/usr/bin/env python3

# Usage: ethsend.py eth0 ff:ff:ff:ff:ff:ff 'Hello everybody!'
#        ethsend.py eth0 06:e5:f0:20:af:7a 'Hello 06:e5:f0:20:af:7a!'
#
# Note: CAP_NET_RAW capability is required to use SOCK_RAW

import fcntl
import socket
import struct

iximiuz

#!/usr/bin/env bash

set -xeuo pipefail

create_bridge() {
    local nsname="$1"
    local ifname="$2"

    echo "Creating bridge ${nsname}/${ifname}"

iximiuz

{"time": "2023-12-11T00:00:01.123Z", "method": "GET", "path": "/foo/bar", "status_code": 200, "content_length": 423}
{"time": "2023-12-11T00:01:01.123Z", "method": "POST", "path": "/foo/bar", "status_code": 200, "content_length": 553}
{"time": "2023-12-11T00:02:01.123Z", "method": "GET", "path": "/foo/baz", "status_code": 200, "content_length": 345}
{"time": "2023-12-11T00:03:01.123Z", "method": "GET", "path": "/foo/baz", "status_code": 401, "content_length": 235}

iximiuz

Description

As everybody knows, execve() system call replaces a calling process image with a new process image. At the same time the file descriptors table remains the same.

The idea of this example is to show how launched via execve() processes can access file descriptors from their parent.

The parent process creates 4 pipes (unidirectional data flows) for stdin/stdout streams of its two children. Then the parent forks itself twice to spawn its children. Each child process binds corresponding pipes to its stdin & stdout and then runs child executable via execl(). To simplify the example, child processes also explicitly shares their stdin file descriptors between each other via command line argument. In the end parent is able to read from children stdouts and write to their stdins, while children are able to write to sibling's stdins (see the schema below).

iximiuz

# syntax=docker/dockerfile:1
FROM ubuntu:22.04

ENV DEBIAN_FRONTEND=noninteractive
ENV TZ=UTC

RUN <<EOF
set -eu

apt-get update

iximiuz

#!/usr/bin/env bash

set -euo pipefail

create_bridge() {
    local nsname="$1"
    local ifname="$2"

    echo "Creating bridge ${nsname}/${ifname}"

iximiuz

const http = require('http');

const log = console.log;
console.log = (...args) => {
  log.apply(console, [new Date().toISOString()].concat(args));
};

const port = process.argv[2];
const server = http.createServer((req, res) => {
  console.log('Incoming request');

iximiuz

#!/usr/bin/env bash

set -euo pipefail

create_bridge() {
    local nsname="$1"
    local ifname="$2"

    echo "Creating bridge ${nsname}/${ifname}"

iximiuz

#!/usr/bin/env python3

import json
import sys

for line in sys.stdin:
    ds = eval(line)
    print(json.dumps(ds))