.vpn_helpers.sh

#!/bin/bash

# Source this file in your .bash_profile e.g.:
#
# source ~/gitcheckouts/vpn_heplers/.vpn_helpers.sh
#
# Note: This script works best with NOPASSWD: ALL configured in your sudoers file:
# /etc/sudoers:
# %admin  ALL=(ALL) NOPASSWD: ALL
#
# Usage:
#
# vpn_connect             - Connect to VPN and force DNS into place
# vpn_disconnect          - Disconnect and reset DNS to defaults
# update_resolver         - Force VPN DNS into place (good for already established connections)
# update_resolver delete  - Reset DNS to defaults (good if VPN is already disconnected)


function obtain_service_ids {

scutil <<<"list" | awk -F/ '/DNS$/ { if (length($(NF-1)) == 36 ) { print $(NF-1) } }' | sort -u

}

function obtain_service_id {
scutil <<EOF | awk -F' : ' '/PrimaryService/ { print $2 }'
open
get State:/Network/Global/IPv4
d.show
quit
EOF
}

function modify_scutil_dns {
declare -a DOMAINS=("${!1}")
shift
local RESOLVERS=$@
sudo scutil <<EOF
open
d.init
d.add ServerAddresses * ${RESOLVERS}
$(for DOMAIN in ${DOMAINS[@]}; do echo d.add DomainName ${DOMAIN}; done)
set State:/Network/Service/${SERVICE_ID}/DNS
quit
EOF
}

function modify_networksetup_dns {
declare -a DOMAINS=("${!1}")
shift
local RESOLVERS=$@
local INTERFACE=${NETWORK_INTERFACE}
sudo networksetup -setsearchdomains ${INTERFACE} ${DOMAINS[@]}
sudo networksetup -setdnsservers ${INTERFACE} ${RESOLVERS}
}

function obtain_scutil_dns {
scutil <<EOF | awk -F' : ' 'BEGIN { resolvers = ""}; { if ($1 ~ "[0-9]$") { resolvers = resolvers OFS $2 }}; END { print resolvers }'
open
get State:/Network/Service/${SERVICE_ID}/DNS
d.show
quit
EOF
}

function update_resolver {
if [ "$1" == "delete" ]; then
  local RESOLVERS="${DEFAULT_DNS}"
  local DOMAINS=("${DEFAULT_SEARCH_DOMAINS[@]}")
else
  local DOMAINS=("${OFFICE_SEARCH_DOMAINS[@]}")
  local ADD_RESOLVER=${OFFICE_DNS}
  local SCUTIL_RESOLVERS="$(obtain_scutil_dns)"
  local RESOLVERS="${ADD_RESOLVER} ${SCUTIL_RESOLVERS/${WORK_RESOLVER}/}"
fi
# modify_scutil_dns ${RESOLVERS}
modify_networksetup_dns DOMAINS[@] ${RESOLVERS}
}


function vpn_connect {
/usr/bin/env osascript <<EOF
tell application "System Events"
  tell current location of network preferences
    set VPN to service "${OFFICE_VPN_NAME}"
    if exists VPN then connect VPN
       repeat while (current configuration of VPN is not connected)
         delay 1
       end repeat
  end tell
end tell
return
EOF
update_resolver
}

function vpn_disconnect {
/usr/bin/env osascript <<EOF
tell application "System Events"
  tell current location of network preferences
    set VPN to service "${OFFICE_VPN_NAME}"
      if exists VPN then disconnect VPN
    end tell
end tell
return
EOF
update_resolver delete
}

# Set these to "empty" for DHCP
export DEFAULT_DNS="empty"
# Use a bash array to support multiple search domains
export DEFAULT_SEARCH_DOMAINS=( empty )
# Used in the scripts above
export SERVICE_ID=$(obtain_service_id)
# Configure these for your settings
export OFFICE_DNS="192.168.5.50"
export OFFICE_VPN_NAME="Office VPN"
# Use a bash style array for OFFICE_SEARCH_DOMAINS
export OFFICE_SEARCH_DOMAINS=( c2fo.com corp.c2fo.com )
export NETWORK_INTERFACE="Wi-Fi"