#!/bin/sh
# /usr/local/sbin/internet	20030524	NHA
# Run this in the background to monitor the state of our internet connection.
# It automatically re-schedules itself periodically, even
# across system restarts.   Invoked with option -1, there is no re-scheduling.
# We assume that the link is up initially.
# Records internet downtime to $LOGFILE and to syslog.
# $TMPFILE always has the most recent interesting info, and $TMPFILE.bak
# has a record of the latest downtime info.
# NOTE that it would be possible to use "mtr --report --report-cycles 2" instead
# of ping.  This works with most every host.  The output can be discarded
# because the exit status says it all.
# NOTE that netstream.ch can also be pinged, but we don't use that because
# it doesn't really prove that we can reach the outside world.
# NOTE to check that this is properly scheduled, use the 'atq' command.
# NOTE polling interval can now be dynamic, based on the number of sites reached

typeset -r UP_INTERVAL=5	#how often to poll, in minutes, when link is up
typeset -r DOWN_INTERVAL=10	#how often to poll, in seconds, when link down
typeset -r NOT_ENOUGH_SITES=3	#complain unless more than this many sites rspnd
typeset -r LOGFILE=/var/log/internet.log
typeset -r TMPFILE=/var/tmp/internet.tmp
typeset -r SITES="netstream.ch www.bzonline.ch www.ldlc.com mauto.com serverbeach.com www.debian.org
zoneedit.com ns1.granitecanyon.com"
typeset -i OKcount



test 1 -le ${DEBUG:=0}  &&  logger -p user.info -t internet "$0 starting with debug level $DEBUG"
test 1 -le $DEBUG  &&  echo $(date '+%Y%m%d %H%M%S') " $0 starting with debug level $DEBUG" | tee -a
$LOGFILE
missing=''
OKcount=0
date >$TMPFILE
for site in $SITES ;do
    test 3 -le $DEBUG  &&  echo "internet: Pinging $site (OKcount = $OKcount)"
    if ping -c2 $site >>$TMPFILE 2>&1  &&  ((OKcount += 1)) ;then
	test 4 -le $DEBUG  &&  echo internet: OK response from $site
    else
	test 1 -le $DEBUG  &&  echo internet: No response from $site
	#logger -p user.notice -t internet " No response from $site"
	if expr $site :  '.*\..*\..*' >/dev/null ;then
	    site=${site#*.}
	fi
	missing="$missing ${site%.*}"
    fi
    # stop polling as soon as more than $NOT_ENOUGH_SITES sites are reached
    # note that has an influence on polling interval under dynamic polling
    if test $NOT_ENOUGH_SITES -lt $OKcount ;then
	break
    fi
done
date >>$TMPFILE
test 2 -le $DEBUG  &&  echo internet: final OKcount = $OKcount


if test 0 -eq $OKcount ;then
    logger -p user.err -t internet " internet connection down since $(head -1 $TMPFILE)"
    echo $(date '+%Y%m%d %H%M%S') " internet connection down since $(head -1 $TMPFILE)" >>$LOGFILE
    ##Note that this next line will disappear
    ##when we are connect to the internet over ethernet instead of over wireless
    #/sbin/iwpriv eth1 card_reset		#maybe the wireless is hosed
    while sleep $DOWN_INTERVAL ;do
	date >>$TMPFILE
	for site in $SITES ;do
	    test 3 -le $DEBUG  &&  echo internet: Pinging $site
	    ping -c2 $site >>$TMPFILE 2>&1  &&  ((OKcount += 1))
	done
	if test 0 -ne $OKcount ;then
	    mmss="$(expr $SECONDS / 60):$(expr $SECONDS % 60)"
	    logger -p user.err -t internet " internet connection up after $mmss"
	    echo $(date '+%Y%m%d %H%M%S') " internet connection up after $mmss" >>$LOGFILE
	    mv $TMPFILE $TMPFILE.bak		#a record of the last downtime
	    break
	fi
    done

elif test $OKcount -le $NOT_ENOUGH_SITES ;then

    #echo $(date '+%Y%m%d %H%M%S') " only $OKcount sites responded" >>$LOGFILE
    logger -p user.warning -t internet " only $OKcount sites responded"

else
    if test 2 -le $DEBUG ;then
	echo $(date '+%Y%m%d %H%M%S') " $OKcount sites responded" >>$LOGFILE
    fi
    if test -n "$missing" ;then
	logger -p user.notice -t internet "No response from $missing"
    fi
fi


if test '-1' != "$1" ;then			#option -1 inhibits re-schedule
    # schedule next invocation
    #NOTE that $0 will normally be sh, not the name of the shell script to run
    at -f /usr/local/sbin/internet now + $UP_INTERVAL minutes 2>/dev/null
    ##make the polling interval dynamic
    #at -f /usr/local/sbin/internet now + $OKcount minutes 2>/dev/null
fi