#!/bin/sh

# Login Info
PPTP_USER=<vpn_user_name>
PPTP_PASSWORD=<vpn_password>

# PPTP Server Info
PPTP_DOMAIN=<vpn_domain>
PPTP_SERVER=<vpn_server_name_or_ip>
PPPD_OPTIONS=
DEF_GATEWAY=No
ADD_SUBNETS=<vpn_extra_subnets_space_delimited> # for example, "192.168.100.0 192.168.101.0"
                        # this is needed if you're not using default gateway from VPN network,
                        # and your VPN network has multiple subnets.
UNIT=5 # anything but 0

# Do not change anything below unless you know what you're doing...

SCRIPTS_PATH=/tmp/ppp/ppp${UNIT}
FIRE_PATH=/tmp/config
DNSMASQ_CUSTOM=/etc/dnsmasq.custom
TMPF=/tmp/$(date '+%y%d%m%H%M%S')

_up()
{
    echo "IP-UP"

    if [ x$IFNAME == x ]; then
        return 0
    fi

    echo $IFNAME > $SCRIPTS_PATH/link

    ifconfig $IFNAME arp multicast up

    nvram set ppp${UNIT}_get_ip=$IPLOCAL
    nvram set ppp${UNIT}_gateway=$IPREMOTE

    echo "rebind-domain-ok=$PPTP_DOMAIN" > $TMPF
    echo "server=/$PPTP_SERVER/#" >> $TMPF
    [ -n $DNS1 ] && echo "server=/$PPTP_DOMAIN/$DNS1" >> $TMPF

    # configure routes via remote gateway
    if [ x$IPREMOTE != x ]; then

        # delete existing routes
        route del default   dev $IFNAME
        route del $IPREMOTE dev $IFNAME

        # add routes to the gateway and to itself
        route add $IPREMOTE metric 0 dev $IFNAME
        route add $IPLOCAL  metric 0 dev $IFNAME

        # add routes to DNS servers
        [ -n $DNS1 ] && route add $DNS1 gw $IPREMOTE metric 0 dev $IFNAME
        [ -n $DNS2 ] && route add $DNS2 gw $IPREMOTE metric 0 dev $IFNAME

        # add route to the gateway subnet
        route add -net ${IPREMOTE%'.'*}.0 gw $IPREMOTE netmask 255.255.255.0 metric 0 dev $IFNAME

        # default gateway
        metric=1
        if [ "$DEF_GATEWAY" == "Yes" ]; then
            metric=0
        fi
        route add default gw $IPREMOTE metric $metric dev $IFNAME

        # add routes to additional subnets if any
        for subnet in $ADD_SUBNETS
        do
            route add -net $subnet gw $IPREMOTE netmask 255.255.255.0 metric 0 dev $IFNAME
        done

        # remove route to the gateway - no longer needed
        route del $IPREMOTE dev $IFNAME
    fi

    # firewall script
    mkdir -p $FIRE_PATH
    echo '#!/bin/sh
    if [ -f /var/run/ppp'$UNIT'.pid ] && [ -n $(cat /var/run/ppp'$UNIT'.pid) ]; then
    iptables -t nat -A PREROUTING -i '$IFNAME' -d '$(nvram get lan_ipaddr)'/'$(nvram get lan_netmask)' -j DROP
    iptables -t nat -A POSTROUTING -o '$IFNAME' -j MASQUERADE
    iptables -A FORWARD -i '$IFNAME' -j wanin
    iptables -A FORWARD -o '$IFNAME' -j wanout
    iptables -A FORWARD -i '$IFNAME' -j upnp
    fi
    ' > "$FIRE_PATH/ppp$UNIT.fire"
    chmod +x "$FIRE_PATH/ppp$UNIT.fire"

    mv -f $TMPF $DNSMASQ_CUSTOM
    service routing restart
    service dnsmasq restart
    service firewall restart
}

_down()
{
    echo "IP-DOWN"

    nvram unset ppp${UNIT}_get_ip
    nvram unset ppp${UNIT}_gateway

    rm -f $FIRE_PATH/ppp$UNIT.fire
    rm -f $SCRIPTS_PATH/link
    echo "" > $DNSMASQ_CUSTOM

    service routing restart
    service dnsmasq restart
    service firewall restart
}

_stop()
{
    echo "Stopping pppd$UNIT..."

    killall ppp$UNIT-up
    killall ppp$UNIT-down
    [ -f /var/run/ppp$UNIT.pid ] && kill $(cat /var/run/ppp$UNIT.pid)
}

_write_config()
{
    mkdir -p $SCRIPTS_PATH

    [ -x "$SCRIPTS_PATH/ppp$UNIT-up" ] || echo '#!/bin/sh
'$0' up' > "$SCRIPTS_PATH/ppp$UNIT-up"
    chmod +x "$SCRIPTS_PATH/ppp$UNIT-up"

    [ -x "$SCRIPTS_PATH/ppp$UNIT-down" ] || echo '#!/bin/sh
'$0' down' > "$SCRIPTS_PATH/ppp$UNIT-down"
    chmod +x "$SCRIPTS_PATH/ppp$UNIT-down"

    echo "  unit $UNIT
    usepeerdns
    plugin pptp.so
    pptp_server $PPTP_SERVER
    user '$PPTP_USER'
    password '$PPTP_PASSWORD'
    default-asyncmap
    nopcomp
    noaccomp
    novj
    nobsdcomp
    nodeflate
    noauth
    refuse-eap
    maxfail 0
    ip-up-script '$SCRIPTS_PATH/ppp$UNIT-up'
    ip-down-script '$SCRIPTS_PATH/ppp$UNIT-down'
    lcp-echo-interval 15
    lcp-echo-failure 6
    lcp-echo-adaptive
    persist
    holdoff 20
    nomppe-stateful
    mtu 1400" > "$SCRIPTS_PATH/options"
}

_start()
{
    echo "Starting pppd$UNIT..."

    pppd file "$SCRIPTS_PATH/options"
}


case $1 in
    start)
        _stop
        sleep 2
        _write_config
        _start
        ;;
    stop)
        _stop
        ;;
    up)
        _up
        ;;
    down)
        _down
        ;;
    config)
        _write_config
        ;;
  *)
        echo "usage: $0 (start|stop|up|down|config)"
        exit 1
esac

exit $?