Tests the VPN's status by ssh-ing to an IP address only accessible when the VPN is up and running a basic command. Runs less frequently on success, very frequently on failure.

test-ssh.sh

#!/bin/bash

shellcheck "$0" || exit 1

IP=1.2.3.4 
OUT=test-ssh.log
DELAY_MIN=2
DELAY_MAX=128
DELAY=$DELAY_MIN

truncate -s 0 $OUT

clear

while true; do
    ssh $IP -o ConnectTimeout=1 -o LogLevel=error date > >(tee -a $OUT) 2> >(tee -a $OUT >&2)

    if test $? == 0; then
        DELAY=$(( DELAY * 2 ))
        if (( DELAY > DELAY_MAX )); then
            DELAY=$DELAY_MAX
        fi
        echo -n "✔️  "
    else
        DELAY=$DELAY_MIN
        echo -n "❌  "
    fi

    echo "Sleeping $DELAY seconds... "
    sleep $DELAY
done