#!/sbin/runscript
# 2010-08-11 <pille@struction.de>
#
# exchange default route to route through a tunneled gateway.
# preferably used in combination with an existing OpenVPN tunnel.
# this may be used as an init script.
#
# it modifies your default route to go through $GW_INTERNAL_IP.
# beforehand it creates a more preferred host route to $GW_EXTERNAL_IP, 
# which is your tunnel server (e.g. OpenVPN) to keep routing tunnel packets up.
#
# keep in mind that your client still uses your DNS settings, 
# so edit /etc/resolv.conf and use a non link local name server, 
# if you want DNS traffic to go through your tunnel, too.
#
# DEPENDS basename ip awk
#
# TODO: call "ip route" less often -> cache stuff
# NOTE: return codes of "ip route" not checked to allow soft failures
# NOTE: it's somehow dirty to actually not start any daemon and faking it via mark_service_{started,stopped}
# NOTE: will work only with exactly one default route given


SELF=`basename $1`

[ -f "/etc/conf.d/${SELF}" ] && . "/etc/conf.d/${SELF}"

depend() {
  use net
  after bootmisc
}

start() {
    ebegin "Starting ${SELF}"

    # get original default gateway.
    # this fails, if more that one exists. (yes, there are reasons for multiple default gateways!)
    DEFAULT_GW=`ip route |awk '$1~/default/ && $2~/via/ {print $3}'`
    DEFAULT_GW_METRIC=`ip route |awk '$1~/default/ && $2~/via/ && $6~/metric/ {print $7}'`

    [ "${DEFAULT_GW}" == "" ] && eend 1 "ERROR: could not get original default gateway!"


    einfo "adding host route to tunnel gateway [${GW_EXTERNAL_IP}] via original default gateway [${DEFAULT_GW}]..."
    ip route add "${GW_EXTERNAL_IP}" via "${DEFAULT_GW}"

    # original default gateway has standard or no metric? remove and save to restore later.
    if [ "${DEFAULT_GW_METRIC}" == "" -o "X${DEFAULT_GW_METRIC}" == "X0" ]; then
	RESTORE_DEFAULT_GW=`ip route |awk '$1~/default/ && $2~/via/ {print $0}'`
	einfo "removing original default gateway [${DEFAULT_GW}]..."
	ip route del default via "${DEFAULT_GW}"
    else
	einfo "not touching original default gateway, which has low priority metric!"
    fi


    einfo "adding new default route via tunnel [${GW_INTERNAL_IP}]..."
    ip route add default via ${GW_INTERNAL_IP}
    eend $?
    mark_service_started "${SELF}"
}

stop() {
    ebegin "Stopping ${SELF}"

    einfo "getting original default gateway from direct host route"
    DEFAULT_GW=`ip route |awk "\\$1~/${GW_EXTERNAL_IP}/ && \\$2~/via/ {print \\$3}"`
    [ "${DEFAULT_GW}" == "" ] && ewarn "WARNING: could not get original default gateway!"

    einfo "removing default gateway [${GW_INTERNAL_IP}]..."
    ip route del default via ${GW_INTERNAL_IP}

    ip route |grep "^default via " >/dev/null
    # restore original default gw, if nessessary
    if [ $? != 0 ]; then
	einfo "restoring original default gateway [${DEFAULT_GW}]..."
	ip route add default via ${DEFAULT_GW}
    fi

    einfo "removing route to tunnel gateway [${GW_EXTERNAL_IP}] via original default gateway [${DEFAULT_GW}]..."
    ip route del "${GW_EXTERNAL_IP}" via "${DEFAULT_GW}"
    eend $?
    mark_service_stopped "${SELF}"
}