Determine protonvpn port via gluetun and update qbittorrent

update_qbit_port.sh

#!/bin/sh
# Determine protonvpn port via gluetun and update qbittorrent
#
# Add the following to sudo crontab -e to run every 5 minutes
# */5 * * * * /bin/sh /path/to/update_qbit_port.sh
# For synology users, run the script as root via the task scheduler every 5 minutes.

QBITTORRENT_USER=            # qbittorrent username
QBITTORRENT_PASS=            # qbittorrent password
QBITTORRENT_PORT=
QBITTORRENT_SERVER=localhost # usually localhost if running all containers on the same machine

GLUETUN_SERVER=localhost     # usually localhost if running all containers on the same machine
GLUETUN_PORT=

VPN_CT_NAME=gluetun

timestamp() {
    date '+%Y-%m-%d %H:%M:%S'
}

findconfiguredport() {
    curl -s --header "Referer: http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}" --cookie "$1" "http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}/api/v2/app/preferences" | jq -r '.listen_port'
}

findactiveport() {
    curl -s "http://${GLUETUN_SERVER}:${GLUETUN_PORT}/v1/openvpn/portforwarded" | jq -r '.port'
}

getpublicip() {
    curl -s "http://${GLUETUN_SERVER}:${GLUETUN_PORT}/v1/publicip/ip" | jq -r '.public_ip'
}

qbt_login() {
    qbt_sid=$(curl -s -i --header "Referer: http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}" --data "username=${QBITTORRENT_USER}" --data-urlencode "password=${QBITTORRENT_PASS}" "http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}/api/v2/auth/login" | awk -F'SID=|;' '/set-cookie: SID/{print $2}')
    return $?
}

qbt_changeport() {
    curl -s -i --header "Referer: http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}" --cookie "$1" --data-urlencode "json={\"listen_port\":$2,\"random_port\":false,\"upnp\":false}" "http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}/api/v2/app/setPreferences" >/dev/null 2>&1
    return $?
}

qbt_checksid() {
    if curl -s --header "Referer: http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}" --cookie "${qbt_sid}" "http://${QBITTORRENT_SERVER}:${QBITTORRENT_PORT}/api/v2/app/version" | grep -qi forbidden; then
        return 1
    else
        return 0
    fi
}

qbt_isreachable() {
    nc -vw 5 ${QBITTORRENT_SERVER} ${QBITTORRENT_PORT} &>/dev/null 2>&1
}

check_vpn_ct_health() {
    while true;
    do
        response_code=$(curl -s -X GET -w "%{http_code}\n" "http://${GLUETUN_SERVER}:${GLUETUN_PORT}/v1/openvpn/portforwarded" -o /dev/null)
        if [ $response_code -ne 200 ]; then
            echo "$(timestamp) | VPN container ${VPN_CT_NAME} not answering..."
            sleep 10 
        else
            echo "$(timestamp) | VPN container ${VPN_CT_NAME} in healthy state!"
            break
        fi
    done
}

get_portmap() {
    res=0
    public_ip=$(getpublicip)
    echo "Debug--this is public_ip: $public_ip"
    qbt_login
    echo "Debug--this is qbt_sid: $qbt_sid"
    if ! qbt_checksid; then
        echo "$(timestamp) | qBittorrent Cookie invalid, getting new SessionID"
        if ! qbt_login; then
            echo "$(timestamp) | Failed getting new SessionID from qBittorrent"
              return 1
        fi
    else
        echo "$(timestamp) | qBittorrent SessionID Ok!"
    fi

    configured_port=$(findconfiguredport "${qbt_sid}")
    active_port=$(findactiveport)

    echo "$(timestamp) | Public IP: ${public_ip}"
    echo "$(timestamp) | Configured Port: ${configured_port}"
    echo "$(timestamp) | Active Port: ${active_port}"

    if [ "${configured_port}" != "${active_port}" ]; then
        if qbt_changeport "${qbt_sid}" ${active_port}; then
            echo "$(timestamp) | Port Changed to: $(findconfiguredport ${qbt_sid})"
        else
            echo "$(timestamp) | Port Change failed."
            res=1
        fi
    else
        echo "$(timestamp) | Port OK (Act: ${active_port} Cfg: ${configured_port})"
    fi

    return $res
}

public_ip=
configured_port=
active_port=
qbt_sid=

# Wait for a healthy state on the VPN container
sleep 20 
check_vpn_ct_health

# check and possibly update the port
get_portmap

exit $?

Re-written for use in an Alpine-based container. A suitable service block/stanza in a docker compose file would look like the following:

port-updater:
    container_name: port-updater
    depends_on:
      - gluetun
      - qbittorrent-nox
    build:
      dockerfile_inline: |
        FROM alpine:latest
        RUN apk add --no-cache curl jq
        COPY --chmod=755 update_qbit_port.sh /bin/update_qbit_port.sh
        CMD update_qbit_port.sh
    network_mode: service:gluetun

Note the network_mode. It allows us to use localhost as the host in requests to both the gluetun and qbittorrent-nox only if the qbittorrent-nox container is also using service:gluetun for its network.