Traceroute

A (partial) Traceroute re-implementation in Elixir.

Simply start the project with iex -S mix and run a trace:

iex> Traceroute.run("google.com", protocol: :udp, ip_protocol: :ipv4, probes: 3)
1  --redacted-- (--redacted--) 11.235ms  6.939ms  9.518ms
2  192.0.0.1 (192.0.0.1) 11.847ms  12.264ms  13.771ms
3  --redacted-- (--redacted--) 12.738ms  12.677ms  13.035ms
4  fra1901aihb001.versatel.de (62.214.42.58) 14.249ms  16.758ms
   89.246.109.249 (89.246.109.249) 21.941ms
5  72.14.217.70 (72.14.217.70) 21.549ms  20.049ms
6  192.178.109.235 (192.178.109.235) 46.902ms  18.17ms  30.988ms
7  142.250.225.76 (142.250.225.76) 98.751ms
   142.251.64.184 (142.251.64.184) 107.648ms
   142.251.241.75 (142.251.241.75) 18.124ms
8  lcfraa-bt-in-f14.1e100.net (142.251.140.174) 16.132ms  16.391ms

For comparison, here's the output from traceroute:

$ traceroute -P udp -w 1 google.com
traceroute to google.com (142.251.140.174), 64 hops max, 40 byte packets
 1  --redacted-- (--redacted--)  3.647 ms  3.184 ms  2.751 ms
 2  192.0.0.1 (192.0.0.1)  8.222 ms  8.685 ms  8.126 ms
 3  --redacted-- (--redacted--)  10.286 ms  9.180 ms  8.877 ms
 4  fra1901aihb001.versatel.de (62.214.42.58)  14.209 ms
    89.246.109.249 (89.246.109.249)  15.354 ms  15.556 ms
 5  72.14.217.70 (72.14.217.70)  16.226 ms *  18.405 ms
 6  192.178.109.153 (192.178.109.153)  17.366 ms *
    192.178.109.235 (192.178.109.235)  19.176 ms
 7  142.251.241.75 (142.251.241.75)  17.459 ms  16.791 ms
    142.251.241.77 (142.251.241.77)  15.151 ms
 8  142.251.241.75 (142.251.241.75)  15.695 ms  16.032 ms  18.588 ms
 9  lcfraa-bt-in-f14.1e100.net (142.251.140.174)  14.811 ms
    108.170.236.249 (108.170.236.249)  17.687 ms *

Features

Sends probes as ICMP, UDP, and TCP packets
Supports IPv4 and IPv6 (use ip_protocol: :ipv6)
Sends multiple probes in parallel with request staggering
Automatically resolves hostnames for each hop's IP address
Returns all the data in a structured format

Configurable Options

protocol - Choose between :icmp, :udp, or :tcp (default: :udp)
ip_protocol - Choose between :ipv4 or :ipv6 (default: :ipv4)
max_hops - Maximum number of hops before aborting (default: 20)
max_retries - Retry count per hop before moving on (default: 3)
timeout - Response timeout in seconds (default: 1)
probes - Number of parallel probes per TTL (default: 3)
print_output - Toggle console output (default: true)

Caveats and Considerations

This library is untested on Windows. Please report any issues for investigation.
You may need to run as sudo depending on your OS. MacOS can run ICMP, UDP, and TCP without root for IPv4, but IPv6 requires root permissions for ICMP packets. Linux always requires root permissions because we need to run one raw socket for sending and receiving the ICMP packets. Generally, if you get :eperm errors, use sudo.
Running many parallel probes can cause performance issues since each ICMP socket receives (but filters) all ICMP replies. Contact me if this affects you. I have a potential fix which is not yet implemented.

Testing `IPv6` using WireGuard

Not every routers have IPv6-support, so if you run a traceroute with ip_protocol: :ipv6 and receive the {:error, :ehostunreach} error, try the following:

Install wireguard (e.g. brew install wireguard-tools)
Sign up for an IPv6 Tunnel (e.g. route64.org)
Create a Tunnelbroker by going to:
1. IPv6 Tunnelbroker
2. Add Tunnelbroker (under List tunnelbrokers)
3. Select a region close to you. Select Wireguard.
4. Add your home IP (as shown on e.g. ip.me) into Remote Endpoint
5. Click Create Tunnelbroker
Navigate back to List Tunnelbroker and click on the Example Config action button next to your newly created tunnelbroker.
Copy the config (starting with [Interface]) to a local w0.conf file.
Enable WireGuard through wg-quick up w0.conf
Now, you should be able to run traceroutes through IPv6!
To disable WireGuard again, run wg-quick down w0.conf

Useful `traceroute` commands to run comparisons

IPv4

# Use 1s timeout and the ICMP protocol
traceroute -w 1 -P ICMP fly.io
# Use 1s timeout and the UDP protocol
traceroute -w 1 -P UDP fly.io
# Use 1s timeout and the TCP protocol
# First try without `sudo` but you most likely need elevated permissions
sudo traceroute -w 1 -P tcp google.com

IPv6

# Use 1s timout and the ICMP protocol
traceroute6 -I -w 1 google.com
# Use 1s timeout and the UDP protocol
traceroute6 -U -w 1 google.com
# Use 1s timeout and the TCP protocol (might need sudo permissions)
traceroute6 -T -w 1 google.com

TODOs

[ ] Support incrementing UDP ports with every probe/retry

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