auto_port_forward.sh

#! /usr/local/bin/bash
# Cronable port forwarding script for PIA/transmission running on
# FreeNAS
#
# Requires bash, jq (JSON parser) and curl
# pkg install jq bash curl
#

# Your PrivateInternetAccess credentials
PIA_USER=username
PIA_PASS=password

get_new_port( ) {
    if ! [ -x $(curl)  ]; then
        echo "Curl not installed/not executable"
        exit 0
    fi
    
    # get the local tunnel ip
    local_ip=$(ifconfig tun0 | grep "inet " | cut -d\  -f2)
    
    #client_id seems to want random data
    client_id=$(head -n 100 /dev/urandom | md5 -r | tr -d " -")
    
    port=$(curl --silent --data "user=$PIA_USER&pass=$PIA_PASS&client_id=$client_id&local_ip=$local_ip" https://www.privateinternetaccess.com/vpninfo/port_forward_assignment | jq .port)
    
    if ! [[ $port =~ ^[0-9]+$ ]]; then
        echo "Garbled data: $port"
        exit 0
    fi
    
    transmission-remote -p $port
}

is_port_forwarded( ) {
    # -pt tests for open port.
    json=$(transmission-remote -pt)
    
    if [[ $json == "Port is open: No" ]]; then
        echo "Closed port detected"
        get_new_port
    elif [[ $json == "Port is open: Yes" ]]; then
        echo "Open port detected"
        exit 1
    else
        echo "Error: transmission said: $json"
        exit 0
    fi
}

re_check_connectivity( ) {
    if nc -zw 1 google.com 80; then
        echo "VPN connection restored."
    else
        echo "Unable to restore VPN connection. Subscription expired? Exiting."
        exit 0
    fi
}

check_for_connectivity( ) {
    if nc -zw 1 google.com 80; then
        echo "VPN connection up."
    else
        echo "VPN connection down. Restarting..."
        service openvpn restart
        re_check_connectivity
    fi
}

check_for_connectivity
is_port_forwarded

exit 1