#!/bin/ksh
# @(#) newswarn.ksh 1.1 94/11/19
# 94/09/18 john h. dubois iii (john@armory.com)
# 94/11/06 Removed c option; now no g opt means check-only.
# 94/11/19 Explicitely state if noone is using the news server.

# Output of command 'sockinfo -st':
# tcp        0      0  192.122.209.42.4724    192.122.209.39.119     CLOSE_WAIT
#    PID 24777: trn
# user bdp on tty /dev/ttyp50

# Usage: FindPortUsers <ip-address> <port-number>
# Output is lines of the form:
# <user> <tty>
# Line are also written to stderr with the form:
# User <user> on tty <tty> is running <ps-name> (pid <process-id>).

# Output of sockinfo has the format:
# line describing a socket used by a process
# ....
# name and pid of the process using the above sockets
# user and controlling tty for the above process
# Example:
#Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)
#tcp        0      0  192.122.209.42.4669    129.24.12.18.7326      ESTABLISHED
#   PID 3362: icb 
#user turtle on tty /dev/ttyp25
#tcp        0      0  192.122.209.42.80      192.122.209.42.4667    TIME_WAIT
#tcp        0      0  192.122.209.42.4666    198.7.0.2.25           TIME_WAIT
#tcp        0   1219  192.122.209.42.20      141.222.1.3.1081       FIN_WAIT_1
#tcp        0      0  192.122.209.42.21      141.222.1.3.1080       ESTABLISHED
#   PID 3061: Mosaic 
#user zap on tty /dev/ttyp21
#tcp        0      0  127.0.0.1.6001         127.0.0.1.4592         ESTABLISHED
# Returns 1 if no users are using the specified ip-address/port-number,
# 0 if any are.
function FindPortUsers {
    sockinfo -st | gawk -v ip="$1" -v Port="$2" '
    BEGIN {
	# Escape dots in IP address so that it can be used as a regex,
	# so that a port number of .* will have the right effect
	gsub(/\./,"\\.",ip)
	FoundUser = 0
    }

    # Find processes connected to a particular port on the news server.
    $1 == "tcp" {
        if ($5 ~ "^" ip "\\." Port "$")
	    PortUser = 1
	next
    }
    $1 == "PID" {
	pid = $2
	gsub(":","",pid)
	procname = $3
	next
    }
    $1 == "user" {
	tty = substr($5,6)
	if (pid == "") {
	    print "User line found before process line... ignoring!" \
	    > "/dev/stderr"
	}
	else if (PortUser && tty != "socksys") {	# Just ignore socksys
	    user = $2
	    printf "User %s on %s is running %s (pid %d).\n",
	    user,tty,procname,pid > "/dev/stderr"
	    if (pid !~ "^[0-9]+$")
		print "Strange pid... ignoring!" > "/dev/stderr"
	    else if (user !~ "^[a-z][a-z0-9]+$")
		print "Strange user name... ignoring!" > "/dev/stderr"
	    else if (tty !~ "^tty")
		print "Strange tty name... ignoring!" > "/dev/stderr"
	    else {
		printf "%s %s\n",user,tty
		FoundUser = 1
	    }
	    PortUser = 0
	}
	pid = ""
    }
    END {
	exit !FoundUser
    }
    '
}

ln_name=${0##*/}
Usage="Usage: $ln_name [-h] [-g<grace-period>] [-s<news-server>] [-p<port>]"
ServerFiles="/usr/lib/news/server /usr/lib/news/rn/server"
typeset -i Grace=-1
Port=119

while getopts :hcg:s:p: opt; do
    case $opt in
    h)
	echo \
"$ln_name: Warn users of impending shutdown of the news server.
$ln_name finds all users who are using the system's news server, reports on
them, and optionally warns them that the news server is about to be shut down. 
Users are repeatedly warned at one minute intervals until the grace period has
expired.  Before each warning, the users still using the news server are
reported on, so that it can easily be determined when all users have finished.
A final warning of immediate shutdown is issued at 0 minutes; a grace period of
0 can be used to give only this warning.  No action is taken when the grace
period expires (the news server must be shut down manually).
$ln_name determines who is using the news server by searching for processes
that have connections to the NNTP port on the news server used by the local
system.  To determine the name of the news server used by the local system,
$ln_name first checks the environment variable NNTPSERVER, and then checks in
order the files /usr/lib/news/server and /usr/lib/news/rn/server.  The first
value found is used.
$Usage
Options:
-g<grace-period>: Set the grace period to <grace-period> minutes, and warn
    users.  Without this option, $ln_name will report once on who is using the
    news server, but will not issue any warnings.
-h: Print this help.
-p<port>: Check for connections to the news server on the given port, instead
    of the default port of $Port (NNTP service).  <port> can be a regular
    expression in the style of egrep(C).  If a port number of 0 is given, 
    it is translated to \".*\", so users with processes connected to the news
    server on any port are warned.  <port> must be a decimal integer.
-s<news-server>: Set news server by name or IP number."
	exit 0
	;;
    p)  
	Port=$OPTARG
	;;
    s)  NNTPSERVER=$OPTARG;;
    g)
	if [[ "$OPTARG" != [1-9]*([0-9]) ]]; then
	    print -u2 "Bad number of minutes: $OPTARG.  Aborting."
	    exit 1
	fi
	Grace=$OPTARG
	;;
    +?)
	print -u2 "$ln_name: options should not be preceded by a '+'."
	exit 1
	;;
    ?) 
	print -u2 "$ln_name: $OPTARG: bad option.  Use -h for help."
	exit 1
	;;
    esac
done
 
# remove args that were options
let OPTIND=OPTIND-1
shift $OPTIND

if [ $# -gt 0 ]; then
    print -u2 "$Usage\nUse -h for help."
    exit
fi

if [ -z "$NNTPSERVER" ]; then
    for file in $ServerFiles; do
	read NNTPSERVER 2>/dev/null < $file && break
    done
fi

if [ -z "$NNTPSERVER" ]; then
    print -u2 "Could not determine news server name."
    exit 1
fi

# Get the ip address of the news server so that sockinfo doesn't have to
# look up the names of all ip connections
if [[ "$NNTPSERVER" = +([0-9])+(.+([0-9])) ]]; then
    ip=$NNTPSERVER
else
    dig +pfset=0x2020 "$NNTPSERVER" | while read name t ip; do
	# Ignore CNAMEs and such.  dig will automatically look up the A
	# record for the name the CNAME points to.
	[ "$t" = A ] && break
    done
    if [[ "$ip" != +([0-9])+(.+([0-9])) ]]; then
	print -u2 "Could not get IP address for news server $NNTPSERVER."
	exit 1
    fi
fi

[ "$Port" = 0 ] && Port=".*"

if [ Grace -eq -1 ]; then
    FindPortUsers "$ip" "$Port" > /dev/null || 
    print "Noone is using the news server."
    exit 0
fi

Prefix="Warning: the news server"

while [ Grace -ge 0 ]; do

    case $Grace in
    0) message="$Prefix is being shut down NOW!";;
    1) message="$Prefix will be shut down in 1 minute.";;
    *) message="$Prefix will be shut down in $Grace minutes.";;
    esac
    print "Sending message: $message"

    FoundUser=false
    FindPortUsers "$ip" "$Port" | while read user tty; do
	# Discard error output from write to avoid warnings re 
	# "you have your terminal set to mesg -n"
	echo "\r$message\r" | write $user $tty 2>/dev/null
	FoundUser=true
    done

    $FoundUser || print "No users are using the news server."

    let Grace-=1
    if [ Grace -gt 0 ]; then
	echo "****"
	sleep 60
    fi
done