#!/bin/sh
# man ip-neighbour:
# STATE := { permanent | noarp | stale | reachable | none | incomplete | delay | probe | failed }
ARPSTATES='(PERMANENT|NOARP|STALE|REACHABLE|NONE|INCOMPLETE|DELAY|PROBE|FAILED)'
CIDRS=
SORT=
ARP=
VERBOSE=
usage() {
    pingsweep="${0##*/}"
    [ "$1" ] && printf '#\n# ERROR: %s\n#\n\n' "$1" >&2
    cat<<EOU
SYNOPSIS:

  $pingsweep [ OPTIONS ]  CIDR1 [ CIDR2 ...  CIDRN ]


CIDR:

  Each CIDR (Classless Inter-Domain Routing address)
  should be in the format   IPv4ADDRESS[/NETMASK]
  where IPv4ADDRESS should be in octet format
  and NETMASK could be specified either as the number of bits
  (a number between 0 and 32) or in octet format.
  If no NETMASK is specified, it is assumed to be /32.

OPTIONS:

  --sort | -s
    sort the output

  --arp | -a
    check arp for local scope if no ping reply

  --verbose | -v
    outputs result for every address checked and if it was
    UP (PING), REACHABLE (ARP) or DOWN 
      (PING implies ARP was never tried, add --arp if on LOCAL subnet)
    whether it's on LOCAL or ROUTED to subnet, or if there is NO-ROUTE to
    it, followed by the route information used trying to reach the address.

EXAMPLES:

  $pingsweep -s 192.168.1.0/27 10.1.0.0/24
    Shows the ip addresses of all hosts replying to ping in the
    provided subnets in a sorted list.

  $pingsweep -v -a 192.168.1.0/24 | grep -E 'REACHABLE|UP'
    Lists the route information for all hosts that either replied to ping
    or are REACHABLE in the arp cache on the local subnet (you need to
    do this from a host in the 192.168.1.0/24 subnet for -a to be useful).
EOU
    [ "$1" ] && exit 1
    exit 0
}
while [ $# -gt 0 ]; do
	case "$1" in
	    --help|-h) usage ;;
	    --sort|-s) SORT=-s ;;
	    --arp|-a) ARP=-a ;;
	    --verbose|-v) VERBOSE=-v ;;
	    *) CIDRS="$CIDRS $1" ;;
	esac
	shift
done
[ $(printf printf) = printf ] || {
    echo "This script requires a POSIX compliant shell (lacking 'printf')!" >&2
    exit 1
}
for x in ipcalc grep cut ip ping sleep column; do
    which $x>/dev/null || {
	printf 'This scripts depends on printf, ipcalc, grep, cut, ip, ping & sleep.\nExecutable "%s" is not found in $PATH ... aborting!\n' $x 1>&2
	exit 1
    }
done

[ "$CIDRS" ] || usage "No CIDR or IP-address specified!"

[ "$SORT" ] && {
    which sort>/dev/null || usage 'Executable "sort" not found in $PATH ... rerun without "--sort" to show unsorted results!'
}

for cidr in $CIDRS; do
    printf %s "$cidr" | grep -qE / || cidr="$cidr/32"
    ipcalc -bn "$cidr" 2>&1 | grep -qE '^Address:\s' || usage "Invalid CIDR: $cidr"
done

isup() {   
    ROUTE=$(ip route get "$1" 2>&1 | grep via | cut -d' ' -f2-)
    if [ "$ROUTE" ]; then
       ROUTE="ROUTED $ROUTE"
       LOCAL=
    else
	ROUTE=$(ip route get "$1" 2>/dev/null | head -1 | cut -d' ' -f2-)
	[ "$ROUTE" ] || {
	    [ "$VERBOSE" ] && printf "%s\tDOWN NO-ROUTE\n" "$1"
	    return
	}
	ROUTE="LOCAL $ROUTE"
	LOCAL=$(ip route get $1 | grep -v via | grep -oE 'dev [^ ]+' | cut -d' ' -f2)
	[ "$LOCAL" ] || printf "WARNING: No interface for LOCAL addr %s!\n" "$1" >&2
    fi
    if ping -q -w2 -c1 "$1" >/dev/null 2>&1; then
	if [ $VERBOSE ]; then printf '%s;UP PING %s\n' "$1" "$ROUTE"
	else printf '%s\n' "$1"; fi
    elif [ "$ARP" ] && [ "$LOCAL" ]; then
	STATE=$(ip neigh get dev $LOCAL $1 2>&1 | grep -oE "$ARPSTATES")
	printf '%s' "$STATE" | grep -qE 'PERMANENT|STALE|NONE|INCOMPLETE|DELAY|PROBE' && {
	    ping -q -w1 -c1 "$1" >/dev/null
	    sleep 1
	    STATE=$(ip neigh get dev $LOCAL $1 2>&1 | grep -oE "$ARPSTATES")
	}
	while printf "%s" "$STATE" | grep -qE 'INCOMPLETE|DELAY|PROBE'; do
	    sleep 0.5
	    STATE=$(ip neigh get dev $LOCAL $1 2>&1 | grep -oE "$ARPSTATES")
	done
	if [ "REACHABLE" = "$STATE" ] && [ $VERBOSE ]; then
	    printf "%s;REACHABLE ARP %s\n" "$1" "$ROUTE"
	elif [ "REACHABLE" = "$STATE" ]; then
	    printf '%s\n' "$1"
	elif [ $VERBOSE ]; then
	    printf "%s;DOWN ARP %s\n" "$1" "$ROUTE"
	fi
    elif [ $VERBOSE ]; then
	[ "$VERBOSE" ] && printf "%s;DOWN PING %s\n" "$1" "$ROUTE"
    fi
}

doit() {
    for cidr in $CIDRS; do
	printf %s "$cidr" | grep -qE / || cidr="$cidr/32"
	IPCALC=$(ipcalc -bn "$cidr" 2>&1)
	BC=$(printf '%s' "$IPCALC" | grep -E '^Broadcast:' | grep -oE '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+')
	if [ -z "$BC" ]; then
	    NW=$(printf '%s' "$IPCALC"  | grep -E '^Address:' | grep -oE '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+')
	    BC=$NW
	else
	    NW=$(printf '%s' "$IPCALC" | grep -E '^Network:' | grep -oE '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+')
	fi
	N1=$(printf '%s' "$NW" | cut -d. -f1)
	N2=$(printf '%s' "$NW" | cut -d. -f2)
	N3=$(printf '%s' "$NW" | cut -d. -f3)
	N4=$(printf '%s' "$NW" | cut -d. -f4)
	[ "$N1.$N2.$N3.$N4" = "$NW" ] || { printf 'INTERNAL ERROR!\n%s\n' "$IPCALC" >&2 ; exit 1 ;}
	while [ "$N1.$N2.$N3.$N4" != "$BC" ]; do
	    isup "$N1.$N2.$N3.$N4" &
	    N4=$(($N4+1))
	    [ $N4 -gt 255 ] && {
		N4=0
		N3=$(($N3+1))
		[ $N3 -gt 255 ] && {
		    N3=0
		    N2=$(($N2+1))
		    [ $N2 -gt 255 ] && {
			N2=0
			N1=$(($N1+1))
			[ $N1 -gt 255 ] && { printf 'INTERNAL ERROR! N1\n' >&2 ; exit 1 ;}
		    }
		}
	    }
	done
	isup "$BC"
    done
}

if [ "$SORT" ]; then
    doit | sort -nt. -k1,1n -k2,2n -k3,3n -k4,4n | column -t -s';'
else
    doit | column -t -s';'
fi