nano /etc/systemd/network/eth0.network
[Match]
Name=eth0
[Network]
DHCP=yes
DNSSEC=no
[DHCP]
# Use same IP by forcing to use MAC address for clientID
ClientIdentifier=mac
# https://github.com/pikvm/pikvm/issues/583
RouteMetric=20nano /etc/systemd/network/wlan0.network
[Match]
Name=wlan0
[Network]
DHCP=yes
DNSSEC=no
[DHCP]
ClientIdentifier=mac
RouteMetric=999wpa_passphrase 'HOTSPOT_ID' 'HOTSPOT_PASSWORD' > /etc/wpa_supplicant/wpa_supplicant-wlan0.conf
systemctl enable wpa_supplicant@wlan0.service
nano /usr/local/bin/failover.sh
#!/bin/bash
# failover.sh
# v2.1 2022-01-26
# * fixed hardcoded interface and incorrect 0/1 values
# v2.0 2022-01-16
# Alex Alexander <alex.alexander@gmail.com>
# Your main internet interface
IF_MAIN="eth0"
# The interface you want to enable if IF_MAIN is not working
IF_FAILOVER="wlan0"
# the metric to set the FAILOVER to when disabled
METRIC_FAILOVER_OFF="999"
# the metric to set the FAILOVER to when ENABLED
METRIC_FAILOVER_ACTIVE="10"
# this number of pings has to fail for us to change state
FAILOVER_PING_THRESHOLD=2
# the hosts we ping to figure out if internet is alive.
# order matters, so we check two separate providers to make sure it's not the other end
HOSTS_TO_PING=(
"1.1.1.1"
"8.8.8.8"
"1.0.0.1"
"8.8.4.4"
)
# how long to waiting when testing main interface
PING_WAIT_MAIN=2
# how long to waiting when testing failover interface
PING_WAIT_FAILOVER=5
PING_LOOPS=1
# how often should we check
CHECK_MAIN_INTERVAL=10
# check whether IF_FAILOVER is working every X seconds
CHECK_FAILOVER_INTERVAL=600
# also check on start
CHECK_FAILOVER_COUNTER=${CHECK_FAILOVER_INTERVAL}
# my failover if is a little unstable, so when checking if it is working, we check twice
CHECK_FAILOVER_THRESHOLD=1
CHECK_FAILOVER_ROUTE=0
CHECK_FAILOVER_PING=0
DEBUG=false
if [[ "$1" == "-d" ]]; then
DEBUG=true
fi
# did we fail because the route was missing?
FAILOVER_DUE_TO_MISSING_ROUTE=false
LAST_STATE=
FAILOVER=false
PINGS_FAILED=0
PINGS_PASSED=0
# We use this method to update some external service.
function update_ha() {
echo "New State: ${@}"
#
# echo "Sending state to Home Assistant: ${@}"
# curl --header "Content-Type: application/json" \
# --request POST -o /dev/null -s \
# --data "{\"state\": \"${@^}\"}" \
# http://<some-host>/api/webhook/failover-status >/dev/null
LAST_STATE="${@}"
}
# This function knows how to check if pings work over an interface.
# It exports results to PINGS_PASSED and PINGS_FAILED
function check_pings() {
IF_TYPE=${1} # MAIN, FAILOVER
IF_NAME="IF_${IF_TYPE}"
IF=${!IF_NAME}
if [[ -z ${IF} ]]; then
echo "[EEE] Could not deduct IF from ${IF_TYPE}"
exit 1
fi
PING_WAIT_NAME="PING_WAIT_${IF_TYPE}"
PING_WAIT=${!PING_WAIT_NAME}
PINGS_FAILED=0
PINGS_PASSED=0
for ip in "${HOSTS_TO_PING[@]}"; do
ping -c ${PING_LOOPS} -W ${PING_WAIT} -I ${IF} "${ip}" 2>&1 >/dev/null
PING_RESULT=$?
if [[ ${PING_RESULT} -eq 0 ]]; then
PINGS_PASSED=$(( PINGS_PASSED + 1 ))
PINGS_FAILED=0
if [[ "${FAILOVER}" == true ]] || [[ "${DEBUG}" == true ]]; then
echo "[I] (failover: ${FAILOVER}) CHECKING ${IF_TYPE} IF: Ping to ${ip}/${IF} succeeded!"
fi
else
PINGS_PASSED=0
PINGS_FAILED=$(( PINGS_FAILED + 1 ))
echo "[E] (failover: ${FAILOVER}) CHECKING ${IF_TYPE} IF: Ping to ${ip}/${IF} FAILED"
fi
[[ ${PINGS_PASSED} -ge ${FAILOVER_PING_THRESHOLD} ]] && break
[[ ${PINGS_FAILED} -ge ${FAILOVER_PING_THRESHOLD} ]] && break
done
}
# Our main check function
function check() {
# first, check if our main interface route even exists
# if not, we can't really do anything, but we can update our state
if ! ip route list | grep default | grep -q ${IF_MAIN}; then
if [[ "${FAILOVER_DUE_TO_MISSING_ROUTE}" == false ]]; then
echo "[E] Could not find route for main interface (${IF_MAIN})"
FAILOVER_DUE_TO_MISSING_ROUTE=true
update_ha "Active (no route)"
fi
return
fi
# then, check if our failover interface route even exists
# we can't failover if there's no failover route ;)
# this is cheap, so we do it every time
if ! ip route list | grep default | grep -q ${IF_FAILOVER}; then
if [[ ${CHECK_FAILOVER_ROUTE} -lt ${CHECK_FAILOVER_THRESHOLD} ]]; then
echo "[W] Could not find route for failover interface, will retry (${IF_FAILOVER})"
CHECK_FAILOVER_ROUTE=$(( CHECK_FAILOVER_ROUTE + 1 ))
return
fi
echo "[E] Could not find route for failover interface (${IF_FAILOVER})"
update_ha "Unavailable (no route)"
return
fi
CHECK_FAILOVER_ROUTE=0
CHECK_FAILOVER_COUNTER=$(( CHECK_FAILOVER_COUNTER + CHECK_MAIN_INTERVAL ))
CHECK_FAILOVER_WAS_DONE=false
# every ~10m, send some pings over the failover interface to make sure it's
# actually working. If it's not, we can't do much to fix it automatically,
# but at least we can send out a notification to investigate, so we are not
# surprised later!
if [[ ${CHECK_FAILOVER_COUNTER} -ge ${CHECK_FAILOVER_INTERVAL} ]]; then
echo "Verifying Failover Internet is reachable"
check_pings FAILOVER
if [[ ${PINGS_FAILED} -ge ${FAILOVER_PING_THRESHOLD} ]]; then
if [[ ${CHECK_FAILOVER_PING} -lt ${CHECK_FAILOVER_THRESHOLD} ]]; then
echo "[W] Failover interface check pings failed, will retry (${IF_FAILOVER})"
CHECK_FAILOVER_PING=$(( CHECK_FAILOVER_PING + 1 ))
return
fi
update_ha "Unavailable (no ping)"
return
else
CHECK_FAILOVER_COUNTER=0
fi
CHECK_FAILOVER_WAS_DONE=true
fi
CHECK_FAILOVER_PING=0
STATE=
METRIC=$(ip route list | grep "^default" | grep "${IF_FAILOVER}" | sed "s:.*metric \([0-9]*\).*:\1:")
[[ ${METRIC} -eq ${METRIC_FAILOVER_OFF} ]] &&
FAILOVER=false || FAILOVER=true
if [[ "${FAILOVER}" == true ]]; then
DEFAULT_GW=$(ip route list | grep "^default" | grep "${IF_MAIN}" | sed "s:.*via \([.0-9]*\).*:\1:")
VIA="via ${DEFAULT_GW}"
else
VIA=""
fi
# we made it here, all routes seem to be present, let's check our main interface
check_pings MAIN
if [[ ${PINGS_FAILED} -lt ${FAILOVER_PING_THRESHOLD} ]]; then
STATE="Ready"
if [[ "${FAILOVER}" == true ]]; then
echo "[CHANGE] Ping through main IF {$IF_MAIN} worked, RESTORING"
# we need to re-write the route so it lowers the metric
FAILOVER_GW=$(ip route list | grep "^default" | grep "${IF_FAILOVER}" | sed "s:.*via \([.0-9]*\).*:\1:")
FAILOVER_GW_IP=$(echo ${FAILOVER_GW} | tr ' ' '\n' | sort -u)
for currentFailoverGW in ${FAILOVER_GW}
do
ip route del default via ${currentFailoverGW}
done
ip route add default via ${FAILOVER_GW_IP} dev ${IF_FAILOVER} metric ${METRIC_FAILOVER_OFF}
FAILOVER_DUE_TO_MISSING_ROUTE=false
fi
if [[ "${FAILOVER_DUE_TO_MISSING_ROUTE}" == true ]]; then
echo "[CHANGE] Main IF ${IF_MAIN} route came back, RESTORING"
FAILOVER_DUE_TO_MISSING_ROUTE=false
fi
else
STATE="Active (no ping)"
if [[ "${FAILOVER}" == true ]]; then
[[ "${DEBUG}" == true ]] &&
echo "(failover: true) Pings failed, but we've already failed over."
else
echo "[CHANGE] At least ${FAILOVER_PING_THRESHOLD} pings failed in a row, FAILING OVER"
# we need to re-write the route so it lowers the metric
FAILOVER_GW=$(ip route list | grep "^default" | grep "${IF_FAILOVER}" | sed "s:.*via \([.0-9]*\).*:\1:")
FAILOVER_GW_IP=$(echo ${FAILOVER_GW} | tr ' ' '\n' | sort -u)
for currentFailoverGW in ${FAILOVER_GW}
do
ip route del default via ${currentFailoverGW}
done
ip route add default via ${FAILOVER_GW_IP} dev ${IF_FAILOVER} metric ${METRIC_FAILOVER_ACTIVE}
fi
fi
if [[ ${STATE} != ${LAST_STATE} ]] || [[ "${CHECK_FAILOVER_WAS_DONE}" == true ]]; then
update_ha "${STATE}"
fi
}
echo "Internet Failover Script"
echo "---"
echo "Main Interface: ${IF_MAIN}"
echo "- Main Check: ${CHECK_MAIN_INTERVAL}s"
echo "Failover Interface: ${IF_FAILOVER}"
echo "- Failover Check: ${CHECK_FAILOVER_INTERVAL}s"
echo "==="
while true; do
check
sleep ${CHECK_MAIN_INTERVAL}
donechmod 750 /usr/local/bin/failover.sh
nano /etc/systemd/system/failover.service
[Unit]
Description=Failover
[Service]
User=root
WorkingDirectory=/usr/local/bin
ExecStart=failover.sh
Restart=always
[Install]
WantedBy=multi-user.target
systemctl enable failover.service
systemctl start failover.service
journalctl -fu failover.service
Alex Alexander alex.alexander@gmail.com
https://www.linuxized.com/2022/01/automatic-internet-failover-to-lte-or-another-interface/