#!/bin/sh
#
#	Description:	IPsrcaddr - Preferred source address modification
#
#	Author:			John Sutton <john@scl.co.uk>
#	Support:		linux-ha@muc.de
#	License:		GNU General Public License (GPL)
#	Copyright:		SCL Internet
#
#	Based on the IPaddr script.
#
#	This script manages the preferred source address associated with
#	packets which originate on the localhost and are routed through the
#	default route.  By default, i.e. without the use of this script or
#	similar, these packets will carry the IP of the primary i.e. the
#	non-aliased interface.  This can be a nuisance if you need to ensure
#	that such packets carry the same IP irrespective of which host in
#	a redundant cluster they actually originate from.
#
#	It can add a preferred source address, or remove one.
#
#	usage: IPsrcaddr ip-address {start|stop|status|monitor}
#
#	The "start" arg adds a preferred source address.
#
#	Surprisingly, the "stop" arg removes it.	:-)
#
#	NOTES:
#
#	1) There must be one and not more than 1 default route!  Mainly because
#	I can't see why you should have more than one.  And if there is more
#	than one, we would have to box clever to find out which one is to be
#	modified, or we would have to pass its identity as an argument.
#
#	2) The script depends on Alexey Kuznetsov's ip utility from the
#	iproute aka iproute2 package.
#
#	3) No checking is done to see if the passed in IP address can
#	reasonably be associated with the interface on which the default
#	route exists.  So unless you want to deliberately spoof your source IP,
#	check it!  Normally, I would expect that your haresources looks
#	something like:
#
#		nodename ip1 ip2 ... ipN IPsrcaddr::ipX
#
#	where ipX is one of the ip1 to ipN.
#

prefix=/usr
exec_prefix=/usr
. /etc/ha.d/shellfuncs

IPROUTE=/sbin/ip
USAGE="usage: $0 ip-address {start|stop|status|monitor}";

  CMDSHOW="$IPROUTE route show   to exact 0/0"
CMDCHANGE="$IPROUTE route change to "

usage() {
	echo $USAGE >&2
}

errorexit() {
	ha_log "ERROR: $*"
	exit 1
}

#
#	We can distinguish 3 cases: no preferred source address, a
#	preferred source address exists which matches that specified, and one
#	exists but doesn't match that specified.  srca_read() returns 1,0,2
#	respectively.
#
#	The output of route show is something along the lines of:
#
#		default via X.X.X.X dev eth1 src Y.Y.Y.Y
#
#	where the src clause "src Y.Y.Y.Y" may or may not be present

WS="[`echo -en ' \t'`]"
OCTET="[0-9]\{1,3\}"
IPADDR="\($OCTET\.\)\{3\}$OCTET"
SRCCLAUSE="src$WS$WS*\($IPADDR\)"
MATCHROUTE="\(.*${WS}\)\($SRCCLAUSE\)\($WS.*\|$\)"

srca_read() {
	# Capture the default route - doublequotes prevent word splitting...
	DEFROUTE="`$CMDSHOW`" || errorexit "command '$CMDSHOW' failed"

	# ... so we can make sure there is only 1 default route
	[ 1 -eq `echo "$DEFROUTE" | wc -l` ] || \
		errorexit "more than 1 default route exists"

	# But there might still be no default route
	[ -z "$DEFROUTE" ] && errorexit "no default route exists"

	# Sed out the source ip address if it exists
	SRCIP=`echo $DEFROUTE | sed -n "s/$MATCHROUTE/\3/p"`

	# and what remains after stripping out the source ip address clause
	ROUTE_WO_SRC=`echo $DEFROUTE | sed "s/$MATCHROUTE/\1\5/"`

	[ -z "$SRCIP" ] && return 1
	[ $SRCIP = $1 ] && return 0
	return 2
}

#
#	Add (or change if it already exists) the preferred source address
#	The exit code should conform to LSB exit codes.
#

srca_start() {
	srca_read $1

	$CMDCHANGE $ROUTE_WO_SRC src $1 || \
		errorexit "command '$CMDCHANGE $ROUTE_WO_SRC src $1' failed"
}

#
#	Remove (if it exists) the preferred source address.
#	If one exists but it's not the same as the one specified, that's
#	an error.  Maybe that's the wrong behaviour because if this fails
#	then when IPaddr releases the associated interface (if there is one)
#	your default route will also get dropped ;-(
#	The exit code should conform to LSB exit codes.
#

srca_stop() {
	srca_read $1

	[ $? = 2 ] && errorexit "addresses don't match"

	$CMDCHANGE $ROUTE_WO_SRC || \
		errorexit "command '$CMDCHANGE $ROUTE_WO_SRC' failed"
}

#
#	The only difference between status and monitor is that the latter
#	returns an appropriate exit code whereas status always returns 0.
#	The return code should conform to LSB exit codes.
#

srca_status() {
	srca_read $1

	case $? in
		0)	echo "OK"
			return 0;;

		1)	echo "No preferred source address defined"
			return 3;;

		2)	echo "Preferred source address has incorrect value"
			return 4;;
	esac
}

srca_monitor() {
	srca_status $1
}

#
#	Add or remove the preferred source IP address to be used for packets
#	originating on the localhost and leaving via the default route.
#

if
	[ $# -ne 2 ]
then
	usage
	exit 1
fi

case $2 in
	start)		srca_start $1;;
	stop)		srca_stop $1;;
	status)		srca_status $1;;
	monitor)	srca_monitor $1;;
	*)			usage
				exit 1
				;;
esac
#
# Version 0.3  2002/11/04 17:00:00 John Sutton <john@scl.co.uk>
# Name changed from IPsrcroute to IPsrcaddr and now reports errors
# using ha_log rather than on stderr.
#
# Version 0.2  2002/11/02 17:00:00 John Sutton <john@scl.co.uk>
# Changed status output to "OK" to satisfy ResourceManager's
# we_own_resource() function.
#
# Version 0.1  2002/11/01 17:00:00 John Sutton <john@scl.co.uk>
# First effort but does the job?
#