feat(portforwarding): Allow running script upon port forwarding success

[lavalleeale]

This PR allows an environment variable (VPN_PORT_FORWARDING_STATUS_SCRIPT) to be set that will run a script whenever there is an update to port forwarding status that could be used to sync with other programs that need to know what ports have been forwarded.

EDIT by qdm12:

• Fixes Feature request: Webhook call when forwarded port change #2351
• Partly addresses Feature request: run a script on interface up/down #1785
• May refer to Startup Script PIA with Port Forwarding #616, Gluetun+PIA: anyone have a script to auto-update the forwarded port in qbittorrent? #1555 (more to completed)

[qdm12]

Nice, thank you for this PR 👍

We need to notably:

• change this to a run command (instead of script file)
• make code ready for a down command (later 🙏, if anyone needs such command)
• make a PR to the github wiki to document this (probably in the setup/advance/vpn-port-forwarding document) and mention the command is a single command, which doesn't understand shell specific syntax such as &&, and one should use /bin/sh -c "my shell syntax" to do so if they want (bash isn't installed by default, only sh)

Thanks!

[lavalleeale]

Ok, I believe that I have resolved all the issues with the initial implementation, I am not a huge fan of comma separating the ports, but that is how the current code works to give maximum compatibility

[qdm12]

Nice job! 👍
Just 2 renames to do 😉
And once done I'll handle the using-that-command-package-and-plug-lines-to-the-logger. I just worked on it yesterday so it's still fresh in my mind 😉 !

[qdm12]

FYI I'm working on your branch right now, almost done rebasing+fixing the last feedback I left, so please hold 😉 Thanks!!

[qdm12]

Hi @lavalleeale could you give me (force) push access to your Gluetun branch master? I'm done with the changes, just waiting to force push them there.

[thibautd]

Thanks for working on this, can't wait !

[iceteaSA]

Anything happening here?

[qdm12]

@lavalleeale I still don't have push access to your fork, can you please allow force push access? Otherwise I'll create another PR with another branch, but would like to give you the credits for it ideally!

[lavalleeale]

Done!

[qdm12]

Thanks @lavalleeale
Just waiting for CI to pass, and I'll re-recheck my own still unresolved comments to make I've done them (has been a while already!).

[qdm12]

Merged, thanks! I've tested it locally, it looks like it's working fine.
I also added VPN_PORT_FORWARDING_DOWN_COMMAND in the next commit, which does what its name says.
And also pushed f9bdb21 to support quoting better i.e. echo "hello" would previously be changed to echo "hello which would fail the parsing step, now it's fixed.

[KSmanis]

@qdm12 Thanks for merging! I've already successfully migrated my setup from polling the control server to this hook, but I'd rather not follow the master branch. Any plans on a new release soon?

[thibautd]

For those wanting to use this new feature with Transmission, I wrote a simple Python script to automatically update the Peer Port in Transmission. It's written in Python and uses the uv package manager.

docker-compose.yml

services:
  gluetun:
    build: ./gluetun
    container_name: gluetun
    cap_add:
      - NET_ADMIN
    devices:
      - /dev/net/tun:/dev/net/tun
    environment:
      - Your other env vars here...
      - VPN_PORT_FORWARDING_UP_COMMAND=/bin/uv run --script /transmission-sync.py {{PORTS}}
    restart: unless-stopped
    networks:
      - internal
  transmission:
    image: lscr.io/linuxserver/transmission:latest
    container_name: transmission
    network_mode: "service:gluetun"
    volumes:
      - # Your volumes here
    restart: unless-stopped

I had to create a custom Docker image for gluetun to install Python, uv and my script inside:

gluetun/Dockerfile

FROM qmcgaw/gluetun:latest

RUN apk add --no-cache python3

COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/
COPY transmission-sync.py /

Finally, the Python script wich uses https://pypi.org/project/transmission-rpc/.

gluetun/transmission-sync.py

# /// script
# requires-python = ">=3.12"
# dependencies = [
#     "requests",
#     "transmission-rpc",
# ]
# ///

import sys
import requests
from transmission_rpc import Client

PORTS = [int(p) for p in sys.argv[1].split(",")]

print('Set port: ', PORTS)

CLIENT = Client(host="127.0.0.1", port=9091)
CLIENT.set_session(peer_port=PORTS[0])

print('Done')

I put that here in case it can be useful :-)