How to programmatically detect the presence of a VPN

command lineNetworkvpn

I'd like to be able to programmatically detect the presence of a VPN on a Mac. Detecting if a VPN connection is active programmatically shows what the output of netstat -nr will look like when a VPN is active:

Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
0/1                10.81.10.5         UGSc            5        0   utun1
...

Some of the information is significant for my purpose, the rest of it isn't. What exactly do I need to check? Only that Netif contains utun1? Or do I need to see 0/1 there too? Or if not, what then?

I am currently testing for the first and last data items in that line, and it seems to be working, but I'd like to reduce the probability of any false positives or negatives. In Ruby it is:

# This is determined by whether or not a line like the following
# appears in the output of `netstat -nr`:
# 0/1                10.137.0.41        UGSc           15        0   utun1
def vpn_running?
  run_os_command('netstat -nr').split("\n").grep(/^0\/1.*utun1/).any?
end

Best Answer

That's exactly what I have in my own code. In bash it looks like:

vpn=$( netstat -rn | grep utun1 | wc -l )
if [[ $vpn -eq 0 ]] ; then
    # no VPN active
else
    # VPN active
fi

It's been pretty reliable in my environment. I'd like to be able to discern different VPN configurations in effect, but not so much as to have to code it (yet).

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