`/etc/init.d/jenkins.portforwarding` script for SUSE Linux to forward port 80 traffic to the HTTP port for the Jenkins continuous build server

jenkins.portforwarding.sh

#!/bin/sh
#
#     SUSE system statup script for port forwarding port 80 to the port
#     for the Jenkins continuous build server.
#
#     Jenkins normally does not run as root, thus /etc/init.d/jenkins cannot
#     bind to ports < 1024 since SUSE does not support authbind (or similar).
#
#     The MIT License (MIT)
#
#     Copyright (C) 2014 Steve Jansen
#
#     Permission is hereby granted, free of charge, to any person obtaining a copy
#     of this software and associated documentation files (the "Software"), to deal
#     in the Software without restriction, including without limitation the rights
#     to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#     copies of the Software, and to permit persons to whom the Software is
#     furnished to do so, subject to the following conditions:
#
#     The above copyright notice and this permission notice shall be included in
#     all copies or substantial portions of the Software.
#
#     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#     AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#     THE SOFTWARE.
#
### BEGIN INIT INFO
# Provides:          jenkins.portforwarding
# Required-Start:    jenkins
# Should-Start:
# Required-Stop:     jenkins
# Should-Stop:
# Default-Start:     3 5
# Default-Stop:      0 1 2 6
# Short-Description: Port forwarding for Jenkins continuous build server
# Description:       Forward port 80 traffic to the Jenkins continuous build server
### END INIT INFO

# Check for existence of needed config file and read it
JENKINS_CONFIG=/etc/sysconfig/jenkins
JENKINS_FORWARD_PORT=80

test -r "$JENKINS_CONFIG" || { echo "$JENKINS_CONFIG not existing";
  if [ "$1" = "stop" ]; then exit 0;
  else exit 6; fi; }

# Read config
. "$JENKINS_CONFIG"

. /etc/rc.status
rc_reset # Reset status of this service

if [ "$JENKINS_PORT" -eq "$JENKINS_FORWARD_PORT" ]
then
  echo "Jenkins already running on port $JENKINS_FORWARD_PORT, skipping port forwarding"
  rc_exit
fi

readonly iptables_table="-t nat"
readonly base_rule="-p tcp --dport $JENKINS_FORWARD_PORT -j REDIRECT --to-ports $JENKINS_PORT"
readonly external_rule="PREROUTING -p tcp -m tcp --dport $JENKINS_FORWARD_PORT -j REDIRECT --to-ports $JENKINS_PORT"
readonly loopback_rule="OUTPUT -p tcp -m tcp --dport $JENKINS_FORWARD_PORT -j REDIRECT --to-ports $JENKINS_PORT"

check_status ()
{
  iptables-save $iptables_table | grep -- "$external_rule" > /dev/null 2>&1 && iptables-save $iptables_table | grep -- "$loopback_rule" > /dev/null 2>&1
  return $?
}

case "$1" in
  start)
      check_status
      if [ $? -eq 0 ]
      then
        echo "Jenkins port forwarding already forwarding port $JENKINS_FORWARD_PORT to port $JENKINS_PORT"
        rc_exit
      fi

      echo "Starting Jenkins port forwarding"
      echo "Enabling iptables port forwarding from port $JENKINS_FORWARD_PORT to port $JENKINS_PORT"
      iptables $iptables_table -A $external_interface $external_rule && iptables $iptables_table -A $loopback_rule
      result=$?

      if [ $result -eq 0 ]
      then
        rc_status -v
      else
        rc_failed $result
        rc_status -v
      fi
    ;;
  stop)
      check_status
      if [ $? -ne 0 ]
      then
        echo "Jenkins port forwarding already stopped"
        rc_exit
      fi

      echo "Disabling iptables port forwarding from port $JENKINS_FORWARD_PORT to port $JENKINS_PORT"
      iptables $iptables_table -D $external_interface $external_rule && iptables $iptables_table -D $loopback_rule
      result=$?

      if [ $result -eq 0 ]
      then
        rc_status -v
      else
        rc_failed $result
        rc_status -v
      fi
    ;;
  restart)
      $0 stop
      $0 start
      rc_status
    ;;
    status)
      echo "Checking status of iptables port forwarding from port $JENKINS_FORWARD_PORT to port $JENKINS_PORT"
      check_status
      result=$?

      if [ $result -eq 0 ]
      then
        echo "Port forwarding from port $JENKINS_FORWARD_PORT to port $JENKINS_PORT is enabled"
        rc_status -v
      else
        echo "Port forwarding from port $JENKINS_FORWARD_PORT to port $JENKINS_PORT is disabled"
        rc_failed $result
        rc_status -v
      fi
    ;;
  *)
      echo "Usage: $0 {start|stop|status}"
      exit 1
    ;;
esac
rc_exit