#!/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_and_quoted>
        # 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()
{
    if [ x$IFNAME == x ]; then
        return 0
    fi

    logger -p 6 -t 'pptp-vpn['$$']' 'PPP link '$IFNAME' is up: server IP '$IPREMOTE', local IP '$IPLOCAL

    echo "IP-UP: " $IFNAME $IPREMOTE $IPLOCAL

    echo $IFNAME > $SCRIPTS_PATH/link

    ifconfig $IFNAME arp multicast up

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

    if [ x$PPTP_DOMAIN != x ]; then
        echo "rebind-domain-ok=$PPTP_DOMAIN" > $TMPF
        [ -n $DNS1 ] && echo "server=/$PPTP_DOMAIN/$DNS1" >> $TMPF
    else
        echo "rebind-domain-ok=$PPTP_SERVER" > $TMPF
    fi
    echo "server=/$PPTP_SERVER/#" >> $TMPF

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

        # reset IP address of the interface for MASQ to flush the conntrack entries
        ifconfig $IFNAME add 0.0.0.0
        ifconfig ppp5 add $IPLOCAL dstaddr $IPREMOTE netmask 255.255.255.255

        # 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

        # setup default gateway
        metric_ppp=1
        metric_wan=0
        if [ "$DEF_GATEWAY" == "Yes" ]; then
            metric_ppp=0
            metric_wan=1
        fi
        # reset the default gateway route via physical interface
        route del default gw $(nvram get wan_gateway) dev $(nvram get wan_ifname)
        route del $(nvram get wan_gateway) dev $(nvram get wan_ifname)
        route add $(nvram get wan_gateway) metric 0 dev $(nvram get wan_ifname)
        route add default gw $(nvram get wan_gateway) metric $metric_wan dev $(nvram get wan_ifname)
        # add PPTP default gateway
        route add default gw $IPREMOTE metric $metric_ppp 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 -d '$IPLOCAL' -j WANPREROUTING
    iptables -t nat -A PREROUTING -i '$IFNAME' -d '$(nvram get lan_ipaddr)'/'$(nvram get lan_netmask)' -j DROP
    iptables -t nat -A POSTROUTING -o '$IFNAME' -j MASQUERADE
    iptables -I INPUT -i br0 -d '$IPLOCAL' -j DROP
    iptables -A FORWARD -i '$IFNAME' -j wanin
    iptables -A FORWARD -o '$IFNAME' -j wanout
    iptables -A FORWARD -i '$IFNAME' -j upnp

    # QoS rules (not needed)
    # iptables -t mangle -A FORWARD -o '$IFNAME' -j QOSO
    # iptables -t mangle -A OUTPUT -o '$IFNAME' -j QOSO
    # iptables -t mangle -A PREROUTING -i '$IFNAME' -j CONNMARK --restore-mark --mask 0xff
    fi
    ' > "$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"

    logger -p 6 -t 'pptp-vpn['$$']' 'PPP link is down, restoring default settings...'

    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

    # restore default WAN gateway with metric 0
    route del default gw $(nvram get wan_gateway) dev $(nvram get wan_ifname)
    route del $(nvram get wan_gateway) dev $(nvram get wan_ifname)
    route add $(nvram get wan_gateway) metric 0 dev $(nvram get wan_ifname)
    route add default gw $(nvram get wan_gateway) metric 0 dev $(nvram get wan_ifname)

    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"
}

_restart()
{
    _stop
    sleep 2
    _write_config
    _start
}

_check_run()
{
    if [ ! -f /proc/$(cat /var/run/ppp$UNIT.pid)/exe ]; then
        echo "pppd not running, restarting..."
        _restart
    else
        ifconfig ppp${UNIT} 2>&1 > /dev/null
        if [ $? -eq 1 ]; then
            echo "pppd$UNIT down, restarting..."
            _restart
        fi
    fi
}

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

exit $?