#! /bin/sh
# #############################################################################

       NAME_="killppp"
       HTML_="stop ppp modem connection"
    PURPOSE_="kill ppp pid after n time of no traffic"
   SYNOPSIS_="$NAME_ [-hl] <pid> <n>s|m|h|d"
   REQUIRES_="standard GNU commands, /proc fs"
    VERSION_="1.0"
       DATE_="2004-07-20; last update: 2005-02-28"
     AUTHOR_="Dawid Michalczyk <dm@eonworks.com>"
        URL_="www.comp.eonworks.com"
   CATEGORY_="net"
   PLATFORM_="Linux"
      SHELL_="bash"
 DISTRIBUTE_="yes"

# #############################################################################
# This program is distributed under the terms of the GNU General Public License

usage () {

echo >&2 "$NAME_ $VERSION_ - $PURPOSE_
Usage: $SYNOPSIS_
Requires: $REQUIRES_
Options:
     <pid>, process ID 
     <n>s|m|h|d, n seconds|minutes|hours|days of no traffic
     -h, usage and options (this help)
     -m, manual
     -l, see this script"
exit 1
}

manual() { echo >&2 "

NAME

    $NAME_ $VERSION_ - $PURPOSE_

SYNOPSIS

    $SYNOPSIS_

DESCRIPTION

    $NAME_ is a shell script that kills the ppp process after
    specified time of no traffic. This is especially useful
    for dial-up users who pay per time-unit of being connected.
    The typical use for it, is to start a large download along
    with $NAME_ and go away. The script will shut down ppp
    after the downloading is done. Thus saving unnecessary
    cost of unused network connectivity.

    Depending on how your linux is configured you may need to
    be root to have the right to kill a ppp process and it may
    have to be the ppp daemon (pppd).

    To find the pid of your ppp process type: ps aux | grep ppp

    How this script works? Once activated, $NAME_ checks every
    minute for network traffic on the ppp0 device. As long as
    data is passing through, $NAME_ does nothing. Upon no 
    traffic $NAME_ starts counting time until it reaches the
    specified time and kills the ppp process.

EXAMPLES

    $NAME_ 8249 5m

    This will kill the process 8249 after 5 minutes of no
    traffic.

AUTHOR

    $AUTHOR_ Suggestions and bug reports are welcome.
    For updates and more scripts visit $URL_

"; }


# enabling extended globbing
shopt -s extglob

# ppp interface
ppp_link=ppp0

# local funcs
bytes_count() {

    while read line;do

        if [[ $line == ${ppp_link}:* ]];then
             [[ $1 == r ]] && { set -- ${line#*:}; echo $1; }
             [[ $1 == t ]] && { set -- ${line#*:}; echo $9; }
        fi

    done < /proc/net/dev
}

check_pid() {

    kill -0 $1 &>/dev/null # using bash kill built in
    [ $? = 0 ] && return 0 || return 1

}

time_validateSleepArg() {

    case $1 in
        +([0-9])[smhd] ) return 0 ;;
        *) return 1 ;;
    esac
}

# option handling and execution
case $1 in
    -h) usage ;;
    -l) more $0; exit 1 ;;
    -m) manual | more; exit 1 ;;
    +([0-9])) # arg1 can only be an integer

        # sleep arg check
        time_validateSleepArg $2
        [ $? = 0 ] || { echo >&2 second argument invalid, type $NAME_ -h for help; exit 1; }

        check_pid $1 ; [ $? != 0 ] && { echo >&2 pid $1 does not exits; exit 1; }

        received=$(bytes_count r)
        transmit=$(bytes_count t)

        while kill -0 $1 &>/dev/null ;do

            sleep 60s # time interval for how often to check the /proc/net/dev
            nreceived=$(bytes_count r)
            ntransmit=$(bytes_count t)

            if [[ $nreceived == $received ]] && (( $ntransmit == $transmit));then

                sleep $2 # time to sleep before checking again
                nreceived=$(bytes_count r)
                ntransmit=$(bytes_count t)

                if [[ $nreceived == $received ]] && (( $ntransmit == $transmit));then
                    kill -15 $1; check_pid; [ $? == 1 ] && exit 0
                    kill  -3 $1; check_pid; [ $? == 1 ] && exit 0
                    kill  -9 $1; check_pid; [ $? == 1 ] && exit 0
                    echo process can not be killed, possibly due to lack of ownership rights
                    exit 1
                fi

            fi

        done ;;

    *) echo invalid or missing argument, type $NAME_ -h for help ; exit 1 ;;

esac