#!/bin/sh
# $Id: netparams.sh,v 1.2 1998/05/17 03:25:03 ghudson Exp $

# Usage: netparams [-d defaultbits] [-e] [-f file] address ...
#
# Computes the netmask for each address and outputs the netmask,
# network, broadcast address, and gateway address.  Options are:
#
#	-d defaultbits	Give the default number of bits to use if an
#			IP address is not located on the file.  The
#			default is 24.
#
#	-e		Error if an IP address is not located in the
#			file.
#
#	-f file		Give the masks filename to use.  The default
#			is the concatenation of /etc/athena/masks.local
#			(if it exists) and /etc/athena/masks.
#
# The format of each line of the masks file is:
#
#	address		significant-bits	mask-bits	[gateway]
#
# The first <significant-bits> of <address> are compared against the
# given IP address.  If they match, <mask-bits> is the number of bits
# in the netmask, and <gateway> is the gateway address if given.  (If
# gateway is not given, it is assumed to be one greater than the
# network address.) The first match in the file is taken.  Blank lines
# and lines beginning with a '#' are ignored.

# This script may want to run before /usr is mounted on BSD-ish
# systems, so it uses a very limited set of external commands (expr,
# test, echo).  If you want to use a command not in that set, make
# sure it lives in /bin or /sbin in BSD 4.4.

# Regular expression to match things that looklike IP addresss.
ipreg='[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$'

# Usage message
usage="$0 [-f file] [-d defaultbits] [-e] address ..."

# octet <ip address> sets o1..o4 to the octets of the address.
octets() {
	OLDIFS="$IFS"
	IFS=.
	set -- $1
	o1=$1 o2=$2 o3=$3 o4=$4
	IFS="$OLDIFS"
}

# octetbits <n> splits <n> up into four values b1..b4 each between 0
# and 8.  If you want the first n bits of a 32-bit value, then you
# want the first b1..b4 bits of the corresponding octets.
octetbits() {
	case "$1" in
	 0) b1=0; b2=0; b3=0; b4=0 ;;
	 1) b1=1; b2=0; b3=0; b4=0 ;;
	 2) b1=2; b2=0; b3=0; b4=0 ;;
	 3) b1=3; b2=0; b3=0; b4=0 ;;
	 4) b1=4; b2=0; b3=0; b4=0 ;;
	 5) b1=5; b2=0; b3=0; b4=0 ;;
	 6) b1=6; b2=0; b3=0; b4=0 ;;
	 7) b1=7; b2=0; b3=0; b4=0 ;;
	 8) b1=8; b2=0; b3=0; b4=0 ;;
	 9) b1=8; b2=1; b3=0; b4=0 ;;
	10) b1=8; b2=2; b3=0; b4=0 ;;
	11) b1=8; b2=3; b3=0; b4=0 ;;
	12) b1=8; b2=4; b3=0; b4=0 ;;
	13) b1=8; b2=5; b3=0; b4=0 ;;
	14) b1=8; b2=6; b3=0; b4=0 ;;
	15) b1=8; b2=7; b3=0; b4=0 ;;
	16) b1=8; b2=8; b3=0; b4=0 ;;
	17) b1=8; b2=8; b3=1; b4=0 ;;
	18) b1=8; b2=8; b3=2; b4=0 ;;
	19) b1=8; b2=8; b3=3; b4=0 ;;
	20) b1=8; b2=8; b3=4; b4=0 ;;
	21) b1=8; b2=8; b3=5; b4=0 ;;
	22) b1=8; b2=8; b3=6; b4=0 ;;
	23) b1=8; b2=8; b3=7; b4=0 ;;
	24) b1=8; b2=8; b3=8; b4=0 ;;
	25) b1=8; b2=8; b3=8; b4=1 ;;
	26) b1=8; b2=8; b3=8; b4=2 ;;
	27) b1=8; b2=8; b3=8; b4=3 ;;
	28) b1=8; b2=8; b3=8; b4=4 ;;
	29) b1=8; b2=8; b3=8; b4=5 ;;
	30) b1=8; b2=8; b3=8; b4=6 ;;
	31) b1=8; b2=8; b3=8; b4=7 ;;
	32) b1=8; b2=8; b3=8; b4=8 ;;
	esac
}

# mask8 <o> <b> sets a8 to the first <b> bits of <o>.
mask8() {
	case "$2" in
	0) a8=0 ;;
	1) a8=`expr "$1" - "$1" % 128` ;;
	2) a8=`expr "$1" - "$1" % 64` ;;
	3) a8=`expr "$1" - "$1" % 32` ;;
	4) a8=`expr "$1" - "$1" % 16` ;;
	5) a8=`expr "$1" - "$1" % 8` ;;
	6) a8=`expr "$1" - "$1" % 4` ;;
	7) a8=`expr "$1" - "$1" % 2` ;;
	8) a8=$1 ;;
	esac
}

# fill8 <o> <b> sets a8 to <o> with the last 8-<b> bits set to 1.
fill8() {
	case "$2" in
	0) a8=255 ;;
	1) a8=`expr "$1" - "$1" % 128 + 127` ;;
	2) a8=`expr "$1" - "$1" % 64 + 63` ;;
	3) a8=`expr "$1" - "$1" % 32 + 31` ;;
	4) a8=`expr "$1" - "$1" % 16 + 15` ;;
	5) a8=`expr "$1" - "$1" % 8 + 7` ;;
	6) a8=`expr "$1" - "$1" % 4 + 3` ;;
	7) a8=`expr "$1" - "$1" % 2 + 1` ;;
	8) a8=$1 ;;
	esac
}

# mask <ip address> <n> sets a to the first <n> bits of <ip address>.
# If a third parameter is given, add 1 to the last octet (to get the
# gateway address).
mask() {
	a=""
	octets "$1"
	octetbits "$2"
	mask8 "$o1" "$b1"
	a=$a8
	mask8 "$o2" "$b2"
	a=$a.$a8
	mask8 "$o3" "$b3"
	a=$a.$a8
	mask8 "$o4" "$b4"
	if [ -n "$3" ]; then
		a8=`expr "$a8" + 1`
	fi
	a=$a.$a8
}

# fill <ip address> <n> sets a to <ip address> with the last 32-<n> bits
# set to 1.
fill() {
	a=""
	octets "$1"
	octetbits "$2"
	fill8 "$o1" "$b1"
	a=$a8
	fill8 "$o2" "$b2"
	a=$a.$a8
	fill8 "$o3" "$b3"
	a=$a.$a8
	fill8 "$o4" "$b4"
	a=$a.$a8
}

# getnetmask <ip address> <file> sets maskbits to the number of netmask
# bits for <ip address> according to <file>.  Also sets gateway to the
# gateway field on the matching line, if one was specified.
getnetmask() {
	exec < $2
	maskbits=""
	while read addr sigbits mbits gw; do
		# Ignore blank lines and comments.
		if [ -z "$addr" -o `expr "$addr" : '#'` -ne 0 ]; then
			continue
		fi

		# Make sure the line is in the proper form.
		if [ `expr "$addr" : "$ipreg"` -eq 0 \
		     -o `expr "$sigbits" : '[0-9][0-9]*$'` -eq 0 \
		     -o `expr "$mbits" : '[0-9][0-9]*$'` -eq 0 ]; then
			echo "Bad line in $2: $addr $sigbits $mbits $gw" 1>&2
			exit 1
		fi
		if [ -n "$gw" -a `expr "$gw" : "$ipreg"` -eq 0 ]; then
			echo "Bad gateway in $2: $gw" 1>&2
			exit 1
		fi

		mask "$1" "$sigbits"
		if [ "$a" = "$addr" ]; then
			maskbits=$mbits
			gateway=$gw
			break
		fi
	done
}

# Process arguments.
defaultbits=24
errornf=false
maskfile=""
while getopts d:ef: opt; do
	case "$opt" in
	d)
		defaultbits=$OPTARG
		;;
	e)
		errornf=true
		;;
	f)
		maskfile=$OPTARG
		;;
	\?)
		echo "$usage"
		exit 1
		;;
	esac
done
shift `expr $OPTIND - 1`

# Make sure we have some addresses.
if [ $# -eq 0 ]; then
	echo "Usage: $0 ip-address ..." 1>&2
	exit 1
fi

# Make sure our addresses are in something like the proper format.
for ip in "$@"; do
	if [ `expr "$ip" : "$ipreg"` -eq 0 ]; then
		echo "Bad address: $ip" 1>&2
		echo "Usage: $0 ip-address ..." 1>&2
		exit 1
	fi
done

for ip in "$@"; do
	if [ -n "$maskfile" ]; then
		getnetmask "$ip" "$maskfile"
	elif [ -f /etc/athena/masks.local ]; then
		getnetmask "$ip" /etc/athena/masks.local
		if [ -z "$maskbits" ]; then
			getnetmask "$ip" /etc/athena/masks
		fi
	else
		getnetmask "$ip" /etc/athena/masks
	fi
	if [ -z "$maskbits" ]; then
		# Error out if we were told to, or guess.
		if [ "$errornf" = true ]; then
			echo "$ip not matched." 1>&2
			exit 1
		fi
		maskbits=$defaultbits
	fi

	mask 255.255.255.255 "$maskbits"
	netmask=$a
	mask "$ip" "$maskbits"
	network=$a
	fill "$ip" "$maskbits"
	broadcast=$a
	if [ -z "$gateway" ]; then
		mask "$ip" "$maskbits" 1
		gateway=$a
	fi

	echo "$netmask $network $broadcast $gateway $maskbits"
done