Traceroute a Hetzner Cloud Load Balancer before and after deletion in Go

traceroute.go

package main

import (
	"fmt"
	"net"
	"os"
	"sync/atomic"

	"github.com/aeden/traceroute"
)

// Does not work on macOS (not even with sudo and deactivated firewall), but works nicely from a Hetzner Cloud VM
//
// apt update
// apt upgrade
// apt install golang
// /usr/bin/time -p go run ./traceroute.go
//
// Output if the LB is functional (exits with exit code 0, takes below 2.5 seconds):
//
// traceroute to 65.109.42.205 (65.109.42.205), 64 hops max, 52 byte packets
// 1   _gateway (172.31.1.1)  1.876604ms
// 2   20077.your-cloud.host. (162.55.114.212)  93.587µs
// 3   *
// 4   static.213-239-235-57.clients.your-server.de. (213.239.235.57)  1.152051ms
// 5   core23.fsn1.hetzner.com. (213.239.239.137)  528.986µs
// 6   core5.fra.hetzner.com. (213.239.224.250)  4.963949ms
// 7   core9.fra.hetzner.com. (213.239.252.18)  5.142787ms
// 8   core32.hel1.hetzner.com. (213.239.224.169)  25.059611ms
// 9   spine2.cloud1.hel1.hetzner.com. (88.198.242.250)  25.653479ms
// 10  *
// 11  static.2.131.216.95.clients.your-server.de. (95.216.131.2)  25.191341ms
// 12  static.205.42.109.65.clients.your-server.de. (65.109.42.205)  25.152796ms
//
// Output if the LB was deleted (exits with exit code 1, takes 10 seconds):
//
// traceroute to 65.109.42.205 (65.109.42.205), 16 hops max, 52 byte packets
// 1   _gateway (172.31.1.1)  1.991867ms
// 2   20077.your-cloud.host. (162.55.114.212)  170.878µs
// 3   *
// 4   static.213-239-235-57.clients.your-server.de. (213.239.235.57)  1.095632ms
// 5   core23.fsn1.hetzner.com. (213.239.239.137)  3.375453ms
// 6   core0.fra.hetzner.com. (213.239.252.37)  5.059326ms
// 7   core8.fra.hetzner.com. (213.239.252.9)  5.277316ms
// 8   core31.hel1.hetzner.com. (213.239.224.165)  25.447771ms
// 9   *
// 10  *
// 11  *
// 12  *
// 13  *
// 14  *
// 15  *
// 16  *

func main() {
	options := traceroute.TracerouteOptions{}
	options.SetRetries(1)                             // number of probes per time-to-live
	options.SetMaxHops(16)                            // reduced from traceroute.DEFAULT_MAX_HOPS (64) to exit faster; = max time-to-live, for outgoing probe packets
	options.SetFirstHop(traceroute.DEFAULT_FIRST_HOP) // 1, first used time-to-live

	host := "65.109.42.205"

	ipAddr, err := net.ResolveIPAddr("ip", host)
	if err != nil {
		return
	}

	fmt.Printf("traceroute to %v (%v), %v hops max, %v byte packets\n", host, ipAddr, options.MaxHops(), options.PacketSize())

	var counter uint64

	c := make(chan traceroute.TracerouteHop, 0)
	go func() {
		for {
			hop, ok := <-c
			if !ok {
				fmt.Println()
				return
			}
			atomic.AddUint64(&counter, 1)
			printHop(hop)
		}
	}()

	result, err := traceroute.Traceroute(host, &options, c)
	if err != nil {
		fmt.Printf("Error: %v", err)
	}

	// In result.Hops only the successful hops (the ones not being *) are counted, use the manual counter instead
	// eg for the example above len(result.Hops) would be just 7
	fmt.Println(len(result.Hops))
	fmt.Println(counter)
	if counter > 15 {
		os.Exit(1)
	}
}

func printHop(hop traceroute.TracerouteHop) {
	addr := fmt.Sprintf("%v.%v.%v.%v", hop.Address[0], hop.Address[1], hop.Address[2], hop.Address[3])
	hostOrAddr := addr
	if hop.Host != "" {
		hostOrAddr = hop.Host
	}
	if hop.Success {
		fmt.Printf("%-3d %v (%v)  %v\n", hop.TTL, hostOrAddr, addr, hop.ElapsedTime)
	} else {
		fmt.Printf("%-3d *\n", hop.TTL)
	}
}