#! /bin/sh

# mtrchk - Distinquish few possible states of hosts
# Copyright (C) 2010 Matous J. Fialka [ http://mjf.cz/ ]
# Released under the terms of The MIT License

# USAGE
#	mtrchk [ LASTHOP1 LASTHOP2 ... LASTHOPN ] [ < FILENAME ]
#
# ENVIRONMENT
#
#	MTRCHK_RETRIES	Number of retries performed (default: 1)
#
# INPUT
#	Input either host name or either IPv4 or IPv6 address
#	or list of addresses on every line.  Comments start with
#	the number sign.
#
# OUTPUT
#	The output is generated in the following form:
#
# 	<line>	:= <mark> ' ' <host> [ ' ' <path> ] ;
#	<path>	:= <host> [ ' ' <path> ] ;
#
#	Status	<mark>	Description
#	-------	-------	----------------------------------------
#	0	+	Routed AND alive (ICMP replies)
#	1	-	Routed BUT NOT alive (no ICMP reply)
#	2	@	Routed BUT cycled (redirect loop)
#	3	!	POSSIBLY NOT routed (if last hops given)
#	4	#	NOT found (no such host in DNS)
#	--------------------------------------------------------
#
# EXIT CODES
#
#	Program exits with either status obtained from the last
#	check proceeded or with 127 in case bad option was given
#	or dependency checking failed.

MTRCHK_RETRIES=${MTRCHK_RETRIES-1}

for DEPENDENCY in which test mtr grep sed awk sort
do
	if ! which "$DEPENDENCY" &>/dev/null
	then
		echo "Error: missing program $DEPENDENCY" 1>&2
		exit 1
	fi
done

if ! which [ &>/dev/null
then
	echo "Error: there is no [ link to program test" 1>&2
	exit 127
fi

IP4="\(25[0-5]\|2[0-4][0-9]\|1[0-9]\{2\}\|[1-9]\?[0-9]\)"
IP4="$IP4\(\.$IP4\)\{3\}"

H="[0-9A-Fa-f]\{1,4\}"
IP6="\("
IP6="$IP6\(\($H:\)\{7\}\($H\|:\)\)\|"
IP6="$IP6\(\($H:\)\{6\}\(:$H\|$IP4\|:\)\)\|"
IP6="$IP6\(\($H:\)\{5\}\(\(\(:$H\)\{1,2\}\)\|:$IP4\|:\)\)\|"
IP6="$IP6\(\($H:\)\{4\}\(\(\(:$H\)\{1,3\}\)\|\(\(:$H\)\?:$IP4\)\|:\)\)\|"
IP6="$IP6\(\($H:\)\{3\}\(\(\(:$H\)\{1,4\}\)\|\(\(:$H\)\{0,2\}:$IP4\)\|:\)\)\|"
IP6="$IP6\(\($H:\)\{2\}\(\(\(:$H\)\{1,5\}\)\|\(\(:$H\)\{0,3\}:$IP4\)\|:\)\)\|"
IP6="$IP6\(\($H:\)\{1\}\(\(\(:$H\)\{1,6\}\)\|\(\(:$H\)\{0,4\}:$IP4\)\|:\)\)\|"
IP6="$IP6\(:\(\(\(:$H\)\{1,7\}\)\|\(\(:$H\)\{0,5\}:$IP4\)\|:\)\)"
IP6="$IP6\)"
IP6="$IP6\(%.\+\)\?"

HN="[0-9A-Za-z]\([-0-9A-Za-z]*[0-9A-Za-z]\)\?"
DN="\(\($HN\.\)*[A-Za-z][A-Za-z]\{1,3\}\|$HN\)"

while [ -n "$1" ]
do
	if echo $1 | grep "^\($IP4\|$IP6\|$DN\)$" >/dev/null
	then
		LASTHOPS="$LASTHOPS $1"
	else
		echo "Bad option: ill-formed last-hop $1" 1>&2
		exit 127
	fi
	shift
done

cycled()
{
	while [ -n "$1" ]
	do
		CURRENT=$1
		shift
		for ITEM in $@
		do
			if [ "$CURRENT" = "$ITEM" ]
			then
				return 0
			fi
		done
	done
	return 1
}

lasthop()
{
	ITEM=$1
	while [ -n "$1" ]
	do
		shift
		if [ "$1" = "$ITEM" ]
		then
			return 0
		fi
	done
	return 1
}

STATUS=0

set -f 2>/dev/null

while read HOSTS
do
	for HOST in `echo "$HOSTS" | sed 's/#.*$//'`
	do
		SAVEDHOST=$HOST
		if ! echo $HOST | grep "^\($IP4\|$IP6\)$" >/dev/null
		then
			if ! echo $HOST | grep "^\($DN\)$" >/dev/null
			then
				echo "Bad input: invalid host $HOST" 1>&2
				continue
			fi
			REALHOSTS=`host -R$MTRCHK_RETRIES "$HOST" |
				awk '/has[ \t]+([^ \t]*[ \t]+)?address/ {
					print $NF
				}'`
			if [ -z "$REALHOSTS" ]
			then
				STATUS=4
				echo "# $HOST"
				continue
			fi
		else
			REALHOSTS=`echo $HOST | sed 's/%.\+$//'`
		fi
		for HOST in $REALHOSTS
		do
			TRACE=`mtr -pnc$MTRCHK_RETRIES $HOST </dev/tty |
				sort -nuk1 | awk '{ print $2 }'`
			LAST=`echo $TRACE | awk '{ print $NF }'`
			if lasthop $LAST $LASTHOPS
			then
				STATUS=3
				echo -n '! '
			elif cycled $TRACE
			then
				STATUS=2
				echo -n '@ '
			else
				if ! [ "$HOST" = "$LAST" ]
				then
					echo -n '- '
					STATUS=1
				else
					echo -n '+ '
					STATUS=0
				fi
			fi
			echo $SAVEDHOST $HOST $TRACE
		done
	done
done

exit $STATUS