#!/bin/bash
#
#!F:holdconnections
#
#!P:/usr/local/sbin
#
#!D:Holds selected connections after a dial-on-demand ISDN connection
#!D: to prevent hangup during ssh or telnet sessions
#!D: normally started by /etc/ppp/ip-up
#!D: Gets masqueraded connections from netstat, looks for selected destination
#!D:  ports and send a ping to the destination ip address
#
#!C:Copyright 1999 by Peter Bieringer <pb@bieringer.de>
#
#!V:Version 1.01 1999-04-28

# Changes to
#  1.01: first published release


# Here define delay of check and ping, should be lower than hangup-timeout
CKECKDELAY=10 # seconds

# Check whether Dial-Up-Interface is online
checkonline()
{
    echo -n "Check Dial-Up-Status:"
    if imontty | grep -q -i "out"; then
	# Online
	echo " online"
	return 0
    else
	# Offline
	echo " offline"
	return 1
    fi
}


# Check for established connections,
#  test against selected ports and 
#  send a ping to destination
check4connection()
{
    # get all connections with netstat
    netstat -M -n | grep ^tcp | while read proto expire srcip dstip srcprt dummy dstprt dummy; do
    echo " Get: $srcip:$srcprt / $dstip:$dstprt"

        # Test for ssh or telnet
        if [ "$dstprt" = "22" -o "$dstprt" = "23" ]; then
	    echo " Selected: $srcip:$srcprt / $dstip:$dstprt"
	    ping -n -c 1 $dstip >/dev/null
	fi
    done
}



# Start
echo "Start: $0"

while checkonline; do
    echo " Check"
    check4connection
    sleep $CKECKDELAY
done