OpenVPN dhcp-options handlers for Mac OS X (Snow Leopard)

down.sh

#!/bin/bash
# Down script for OpenVPN
# Copyright (c) 2010 eqv.ca
# Licensed under New BSD http://www.opensource.org/licenses/bsd-license.php

NETSTAT=/usr/sbin/netstat
NETWORKSETUP=/usr/sbin/networksetup

# Override DHCP values or leave blank
DNS=
SEARCH=


DEFAULT_IFACE=`$NETSTAT -nr -f inet | grep '^default' | awk '{print $6}'`
DEFAULT_HWPORT=$(
    $NETWORKSETUP -listallhardwareports | \
    while read line; do
        if [[ $line =~ ^"Hardware Port: "(.*) ]]; then
            HWPORT=${BASH_REMATCH[1]}
        fi
        
        if [[ $line =~ ^"Device: $DEFAULT_IFACE"$ ]]; then
            echo $HWPORT
            exit 0
        fi
    done)

if [ -z "$DEFAULT_IFACE" ]; then
    echo "Warning: Could not detect default gateway interface."
    echo "DHCP options will not be reset."
    exit 0
fi

if [ -z "$DEFAULT_HWPORT" ]; then
    echo "Warning: Could not detect hardware port for default gateway interface."
    echo "DHCP options will not be reset."
    exit 0
fi


$NETWORKSETUP -setdnsservers $DEFAULT_HWPORT ${DNS-empty}
$NETWORKSETUP -setsearchdomains $DEFAULT_HWPORT ${SEARCH-empty}

up.sh

#!/bin/bash
# Up script for OpenVPN
# Copyright (c) 2010 eqv.ca
# Licensed under New BSD http://www.opensource.org/licenses/bsd-license.php

NETSTAT=/usr/sbin/netstat
NETWORKSETUP=/usr/sbin/networksetup

# Prepend DHCP options or leave blank
DNS=
SEARCH=


FOREIGN_OPTS="${!foreign_option_@}"

for var in $FOREIGN_OPTS; do
    VALUE="${!var}"
    if [[ "$VALUE" =~ ^"dhcp-option DNS "(.*) ]]; then
        DNS="$DNS${BASH_REMATCH[1]} "
    elif [[ "$VALUE" =~ ^"dhcp-option DOMAIN "(.*) ]]; then
        SEARCH="$SEARCH${BASH_REMATCH[1]} "
    else
        echo "Warning: foreign option $VALUE not recognized."
    fi
done


if [ -z "$DNS" -a -z "$SEARCH" ]; then
    # No options were sent
    exit 0
fi


DEFAULT_IFACE=`$NETSTAT -nr -f inet | grep '^default' | awk '{print $6}'`
DEFAULT_HWPORT=$(
    $NETWORKSETUP -listallhardwareports | \
    while read line; do
        if [[ $line =~ ^"Hardware Port: "(.*) ]]; then
            HWPORT=${BASH_REMATCH[1]}
        fi
        
        if [[ $line =~ ^"Device: $DEFAULT_IFACE"$ ]]; then
            echo $HWPORT
            exit 0
        fi
    done)

if [ -z "$DEFAULT_IFACE" ]; then
    echo "Warning: Could not detect default gateway interface."
    echo "DHCP options will not be implemented."
    exit 0
fi

if [ -z "$DEFAULT_HWPORT" ]; then
    echo "Warning: Could not detect hardware port for default gateway interface."
    echo "DHCP options will not be implemented."
    exit 0
fi


if [ "$DNS" ]; then
    $NETWORKSETUP -setdnsservers "$DEFAULT_HWPORT" $DNS
fi

if [ "$SEARCH" ]; then
    $NETWORKSETUP -setsearchdomains "$DEFAULT_HWPORT" $SEARCH
fi

echo -n "DNS servers: "; $NETWORKSETUP -getdnsservers "$DEFAULT_HWPORT"
echo -n "DNS search path: "; $NETWORKSETUP -getsearchdomains "$DEFAULT_HWPORT"

Since macOS 10.15 Catalina, the output of /usr/sbin/netstat has changed and I needed to use this instead:

DEFAULT_IFACE=`$NETSTAT -nr -f inet | grep '^default' | awk '{print $4}'`

ie. switch from $6 to $4. Using $NF (last column) also works for me on 10.14 as the Expire column is never filled for my default routes.