#!/bin/sh

# simple shell script for FreeBSD to demote local carp announcements if
# a daemon is not running
#
# crontab:
# * * * * * exec /root/watchdog.sh $NAME_OF_DAEMON
#
# e.g.:
# * * * * * exec /root/watchdog.sh httpd
#
# To prevent carp from taking over during system boot, add this
# to /etc/sysctl.conf:
# net.inet.carp_demotion=150

PATH=/usr/bin:/bin:/usr/sbin:/sbin

DAEMON="$1"
LOCKFLAG="$2"

if [ -z "$DAEMON" ]; then
  echo "usage: watchdog.sh <daemon>" >&2
  exit 1
fi

if [ -z "$LOCKFLAG" ]; then
  exec lockf -ks -t 0 "/var/run/watchdog.$DAEMON.lock" "$0" "$DAEMON" x
  exit 1
fi

OID="net.inet.carp.demotion"

set_demotion () {
  local target

  target=$1
  current=`sysctl -n "$OID"`
  delta=$((target-current))

  if [ $delta -ne 0 ]; then
    sysctl -q "$OID=$delta" | logger -t "watchdog.sh/$DAEMON"
  fi
}

trap 'set_demotion 150; exit' 1 2 3 4 5 6 7 8 10 11 12 13 14 15

while true; do
  target=0
  pgrep -q "$DAEMON" || target=150
  set_demotion $target
  sleep 3
done