stund

#!/bin/bash 
#title          :stund
#description    :Creates a reverse ssh connection using ssh port fowarding
#author         :Sergio Aguilar
#date           :20120731
#version        :0.1.0    
#usage          :./stund
#notes          :       
#bash_version   :4.2.24(1)-release
#============================================================================

NAME="$(basename "$0")"
HOSTNAME=host.example.com
KEY=/path/to/private/sshkey
USER=userlogin

# Connect command with ssh:
# -f don't need a terminal go to background, -N dont execute a remote command.
# -R reverse tunnerl, 222000 is the port to listen on the remote server $HOSTNAME
# 22 is the local port where ssh is listenting to.
SSHCONNECT="ssh -f -g -N -R 22000:localhost:22 -i $KEY $USER@$HOSTNAME"
# Instantiate PID variable
PID=''

# Format functions:
bold=`tput bold`
normal=`tput sgr0`

# Core functions:

#
# Boolean function to check that the tunnel is working:
#
function status {

# Get the PID number; with no echo:
pidnum > /dev/null

if [[  ($PID != '') && ($PID -gt 1) ]]; then
  
  # Look for the PID network connection, verify that the TCP connection state is ESTABLISHED:
  if [ $(lsof -n -i TCP | grep $PID | grep IPv4 | grep ESTABLISHED | grep -c -v 'grep') -eq 1 ]; then
    #echo "ssh running and established"
    return 0
  fi
  
else
  #echo "not running"
  return 1
fi

}

#
# Echos the process pid number, '' when doesn't exist
#
function pidnum {

  PID=$( ps aux | grep "$SSHCONNECT" | grep -v 'grep' | awk '{print $2}' )
  
  #echo "pid=$PID"
  echo $PID
  
}

#
# Starts the Tunnel:
#
function do_start {
  if status ; then
    echo "There is alreday a tunnel"
  else
    echo "Connecting ..."
    $SSHCONNECT
      
    if status; then
      echo "Connection successful"
    else
      echo "ERROR: there was a problem with the ssh connection"
      exit 1
    fi
  fi
}

#
# Stops the Tunnel:
#
function do_stop {
  
  if status; then
    echo "Stoping..."
    kill -9 $PID
  else 
    echo "Nothing to terminate"
    exit 1
  fi
}

#
# Report an overview of the tunnel status:
# pid number, possible connected users, shells, last logins from auth
#
function do_fullstatus {
  
  etime=$(ps -eo pid,etime | grep $PID | awk '{print $2}')
  local_ssh_count=$(netstat -tnp 2> /dev/null | grep $PID | grep 127.0.0.1:22 | wc -l)
  
  echo "${NAME} (pid $PID) tunnel link UP"
  echo "Process elapsed= $etime"
  echo "Currently connected: $local_ssh_count"
  echo "${bold}-Shells:${normal}"
  who -a | grep localhost
  echo "-${bold}Network connections for (pid $PID):${normal}"
  netstat -tnp 2> /dev/null | grep $PID
  echo "-${bold}Last localhost ssh logins from auth.log:${normal}"
  grep "Accepted password for $USER from 127.0.0.1" /var/log/auth.log
  
}

case $1 in
  "start" | "--start")
    do_start
  ;;
    
  "stop" | "--stop")
    do_stop
  ;;
    
  "status" | "--status")
    if status; then
      echo "${NAME} (pid $PID) tunnel link UP"
    else
      echo "${NAME} tunnel link DOWN"
    fi
  ;;
  "pid" | "--pid")
    if status; then
      PID=$(pidnum)
      echo "PID=$PID"
    else
      echo "Error: ${NAME} not running no PID to report"
      exit 1
    fi
  ;;
  
  "restart" | "--restart")
    stop
    start
  ;;
  
  "fullstatus" | "--fullstatus")
    if status; then
      do_fullstatus
    else
      echo "${NAME} tunnel link DOWN"
    fi
  ;;
  *)
    echo "Usage: ${NAME} {start|stop|restart|status|fullstatus}"
  ;;
esac

exit 0