merlin-pptp-gw-override.sh

#!/bin/sh
#DEBUG= # uncomment/comment to enable/disable debug mode

#          name: merlin-pptp-gw-override.sh
#       version: 1.0.0, 22-jul-2022, by eibgrad
#       purpose: replace pptp default gateway w/ pptp static routing
#       type(s): init-start
#          href: https://tinyurl.com/2yekbh7e
#  installation:
#    1. enable jffs custom scripts and configs (administration->system)
#    2. ssh to router and copy/paste the following command:
#         curl -kLs bit.ly/merlin-installer|tr -d '\r'|sh -s MLtSBb6E
#    3. modify script w/ your preferred options using nano editor:
#         nano /jffs/scripts/merlin-pptp-gw-override.sh
#    4. reboot

SCRIPTS_DIR='/jffs/scripts'
SCRIPT1="$SCRIPTS_DIR/merlin-pptp-gw-override.sh"
SCRIPT2="$SCRIPTS_DIR/init-start"

mkdir -p $SCRIPTS_DIR

# ---------------------- begin merlin-pptp-gw-override ----------------------- #
cat << 'EOF' > $SCRIPT1
#!/bin/sh
#set -x # comment/uncomment to disable/enable debug mode
{
# ------------------------------ BEGIN OPTIONS ------------------------------- #

# remote ip(s)/network(s) reachable over vpn (space separated)
REMOTE_NET='192.168.2.0/24 192.168.3.0/24 192.168.10.100'

# how often (in secs) between each check for pptp default gateway
INTERVAL=30

# comment/uncomment to enable/disable continous monitoring
STOP_AFTER_SUCCESS=

# ------------------------------- END OPTIONS -------------------------------- #

# ---------------------- DO NOT CHANGE BELOW THIS LINE ----------------------- #

while sleep $INTERVAL; do
    VPN_IP="$(nvram get vpnc_ipaddr)"
    VPN_GW="$(nvram get vpnc_gateway)"
    VPN_IF="$(nvram get vpnc_pppoe_ifname)"

    # verify appearance of pptp client configuration in nvram
    [[ $VPN_IP && $VPN_GW && $VPN_IF ]] || continue

    # verify appearance of pptp client in process table
    pidof 'pppd' &>/dev/null || continue

    # verify appearance of pptp client default gateway in routing table
    ip route | egrep -q   "^0\.0\.0\.0/1\s.*$VPN_IF(\s|$)" || continue
    ip route | egrep -q "^128\.0\.0\.0/1\s.*$VPN_IF(\s|$)" || continue

    # delete pptp client default gateway
    ip route del   0.0.0.0/1 dev $VPN_IF
    ip route del 128.0.0.0/1 dev $VPN_IF

    # create static routes to remote ip(s)/network(s) over vpn
    for i in $REMOTE_NET; do
        ip route add $i via $VPN_IP dev $VPN_IF
    done

    # force routing system to recognize changes
    ip route flush cache

    # continue monitoring or quit?
    [ ${STOP_AFTER_SUCCESS+x} ] && exit 0
done

} 2>&1 | logger -t $(basename $0 .sh)[$$]
EOF
[ ${DEBUG+x} ] && sed -ri '2 s/^#(set -x)/\1/' $SCRIPT1
chmod +x $SCRIPT1
echo "installed: $SCRIPT1"
# ----------------------- end merlin-pptp-gw-override ------------------------ #

# ----------------------------- begin init-start ----------------------------- #
create_script() {
cat << 'EOF' > $SCRIPT2
#!/bin/sh
#set -x # comment/uncomment to disable/enable debug mode
{
nohup $SCRIPT1 &>/dev/null &
} 2>&1 | logger -t $(basename $0)[$$]
EOF
[ ${DEBUG+x} ] && sed -ri '2 s/^#(set -x)/\1/' $SCRIPT2
sed "s:\$SCRIPT1:$SCRIPT1:g" -i $SCRIPT2
chmod +x $SCRIPT2
}

if [ -f $SCRIPT2 ]; then
    echo "error: $SCRIPT2 already exists; requires manual installation"
else
    create_script
    echo "installed: $SCRIPT2"
fi
# ------------------------------ end init-start ------------------------------ #