checks if the gateway is not available and switches the active interface in bond

bond_mon.sh

#!/bin/bash
# Checks if the gateway is not available and switches the active interface in bond.
# The script is made for zvirt node, designed for bond management via NetworkManager.
#
# v2024.04.05
#
# Change your "bondname" and add script to crontab like: 
# @reboot root /opt/bond_mon.sh

bondname=bond0
upwait=30
checkinterval=10

# get ip of gateway as testip (can be changed to any IP that can ping)
testip=$(ip -j route show 0.0.0.0/0 dev $bondname | jq -r '.[0].gateway')

echo ==== Monitoring Started. Bond $bondname, test $testip ==== | systemd-cat -t bond_mon

while true
do
  if [ -f /proc/net/bonding/${bondname} ]
  then

    slaves=$(cat /proc/net/bonding/${bondname} | grep "Slave Interface" | cut -d ":" -f 2 | sed 's/\s//')
    activeslave=$(cat /proc/net/bonding/${bondname} | grep "Currently Active Slave" | cut -d ":" -f 2 | sed 's/\s//')

    echo ${bondname} slaves: $slaves | systemd-cat -t bond_mon
    echo ${bondname} active: $activeslave | systemd-cat -t bond_mon

    while ping -c 5 ${testip} > /dev/null 2>&1
    do
      sleep $checkinterval
    done

    slavesX2="$slaves $slaves"
    current_slave_found=0
    for slave in $slavesX2
    do
      if [[ $current_slave_found == 1 ]]
      then
        echo ${bondname} changing slave to: $slave | systemd-cat -t bond_mon
        nmcli dev mod ${bondname} +bond.options "active_slave=${slave}"
        break
      fi
      if [[ $slave == "$activeslave" ]]
      then
        current_slave_found=1
      fi

    done

  fi

  sleep $upwait

done