#!/bin/bash
######################################################################
#
#  hexroute - Convert human readable routes to dhcpd static route info
#             for Windows(r) clients
#
#  Copyright (c) 2005-2015 Karl McMurdo
#
#  Freely distributable, but please keep header intact
#
#  Update: May 10, 2015 Change Max Quad to 255
#
######################################################################

# Validate and split an IP address into components
# Args: $1 - IP address, $2 - Array name to store components
function split_ipaddr() {
    # Validate basic format
    if [ ${1:-X} = X ] || [ "${1}" != ${1//[^.0-9]/} ] || [ "${1//[0-9]/}" != "..." ]; then
        return 1
    fi
    
    local rval=0
    local t
    local -a T=([1]="" [2]="" [3]="" [4]="")
    
    # Split the IP address
    T[1]=${1%%.*}
    T[2]=${1#*.}; T[2]=${T[2]%%.*}
    T[3]=${1#*.*.}; T[3]=${T[3]%%.*}
    T[4]=${1#*.*.*.}
    
    # Validate each octet
    [ ${T[1]} = 0 ] && rval=1
    
    for t in 1 2 3 4; do
        [ ${T[${t}]:-999} -gt 255 ] && rval=1
        eval "${2}[${t}]=${T[${t}]}"
    done
    
    return ${rval}
}

# Constants and configuration
VERSION="1.0"
AUTHOR="Karl McMurdo"
YEAR="2015"

# Usage and help messages
USAGE='echo -e "Usage: ${0//*\/} [-v|-h] target/bits [gw] gateway [target/bits [gw] gateway ...]\n\n\tie: ${0} 172.16.0.0/16 gw 192.168.1.1\n" && exit 1'
INFO="HexRoute ${VERSION}    Copyright (c) ${YEAR} ${AUTHOR}

Converts human readable route information to a dhcpd hex string

	-v	Once prints full dhcpd.conf line for route(s)
		Twice also prints option definiton lines for dhcpd.conf
	-h	Prints this message
"

# DHCP configuration strings
DHCPHDR="# New Option Type for Windows Client Static Routes
option new-static-routes code 249 = string;"
DHCPS="option new-static-routes "
DHCPE=";"

# Error messages
BADTARG='echo -e "Invalid target network: ${1}" && exit 2'
BADBITS='echo -e "Invalid Network bit value: ${1}" && exit 3'
BADGW='echo -e "Invalid Gateway: ${2}" && exit 4'

# Default settings
VERBOSE=false
EXTRAVERBOSE=false

# Process command line options
while [ "${1:0:1}" = "-" ]; do
    case "${1}" in
        "-v")
            $VERBOSE && EXTRAVERBOSE=true
            VERBOSE=true
            ;;
        "-h")
            echo "${INFO}"
            eval "${USAGE}"
            ;;
        *)
            eval "${USAGE}"
            ;;
    esac
    shift
done

# Check if we have enough arguments
[ ${#} -lt 2 ] && eval "${USAGE}"
OUT=""

# Process routes
while [ ${#} -ge 2 ]; do
    # Parse target network
    split_ipaddr ${1/\/*/} TARG || eval "${BADTARG}"
    BITS=${1/*\//}
    shift
    
    # Validate bits
    if [ ${BITS:-X} = X ] || [ "${BITS}" != ${BITS//[^0-9]/} ]; then
        eval "${BADBITS}"
    fi
    
    if [ ${BITS} -gt 32 ] || [ ${BITS} -lt 1 ]; then
        eval "${BADBITS}"
    fi
    
    # Handle optional "gw" keyword
    [ ${1:-X} = gw ] && shift
    
    # Parse gateway
    split_ipaddr ${1:-X} GW || eval "${BADGW}"
    shift
    
    # Build output in hex format
    OUT=${OUT}$( printf ":%02x:%02x" ${BITS} ${TARG[1]} )
    [ ${BITS} -gt 8 ]  && OUT=${OUT}$( printf ":%02x" ${TARG[2]} )
    [ ${BITS} -gt 16 ] && OUT=${OUT}$( printf ":%02x" ${TARG[3]} )
    [ ${BITS} -gt 24 ] && OUT=${OUT}$( printf ":%02x" ${TARG[4]} )
    OUT=${OUT}$( printf ":%02x:%02x:%02x:%02x" ${GW[@]} )
done

# Output results
$EXTRAVERBOSE && echo "${DHCPHDR}"
if $VERBOSE; then
    echo ${DHCPS}${OUT/:/}${DHCPE}
else
    echo ${OUT/:/}
fi